Toward New Physics At the LHC by ghkgkyyt

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									        Toward New Physics
           At the LHC
The experimental program of the Large Hadron Collider at CERN

                      Lecture 4: New Physics
                                April 3, 2008

                          Joseph R. Incandela
                 University of California, Santa Barbara

                  21st Spring School on Particles and Fields
           The Institute of Physics, National Chiao-Tung University,
                               HsinChu, Taiwan
                  Acknowledgements
• I thank the following people (in no preferred order) for their slides:
    • Rick Cavanaugh, Daniel Froidevaux, Dan Green, Steinar Stapnes, Jörg
      Wenninger, Sally Dawson, Ian Hinchliffe, Karl Jacobs, Oliver Buchmuller, Ian
      Low, Albert De Roeck, Andy Parker, Roberto Tenchini, Guenther Dissertori,
      Jorgen D‟Hondt,…
• I thank the following people for discussions and special info
    • Peter Jenni, Henry Frisch, Paris Sphicas, Claudio Campagnari, Chris Quigg,
      Philip Schuster, Natalia Toro, …and
• … many others from UA1, UA2, CDF, D0, OPAL, ALEPH, CMS, ATLAS…
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                                                                     Recall
       There‟s currently an interesting set of
       circumstances in two “fundamental” areas of
       Physics*:
         • Experimental Particle Physics
                 • Many precise results with no substantial discrepancies with
                   the Standard Model (SM)
         • Experimental Astrophysics and Cosmology
                 • Abundant (literally) evidence for new physics




                                                                              *next few slides inspired by
                                                                              Ian Low (UC Irvine)
       LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                    J.R.Incandela
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                                                   Possible Implications
        • The division is itself a major clue and constrains theory
        • Viable models (that evade constraints of precision
          measurements) often have common features




       LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008         J.R.Incandela
The common structure can produce
     similar phenomenology
We may see something that is not so
        easy to interpret
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       LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
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       LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
     Nevertheless, the case for
Supersymmetry (SUSY) is compelling



 And so we have to consider it seriously
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                                                       Supersymmetry*
         • Extension of known space-time symmetries
                 • 10 generators of Poincare group:
                     • Lj, Kj, Pm for rotations, boosts, translations
                 • SUSY  fermionic operators Qa
                     • Arises naturally in String theory
                 • Is the maximal possible extension of the Poincare group
                      Qa acting on any state produces a new state having the same
                        quantum numbers - except spin which is shifted by ½
                 • Fermions  Bosons are interchanged under group transformation.
                     • Initial state a SM particle  final state its superpartner
                     • No SM particle is the super-partner of another SM particle
                 • Supersymmetry is broken
                     • Mass degenerate superpartners would have been discovered long
                        ago  there must be symmetry breaking contributions to the
                        masses which are large and positive.
         • Once broken…Superpartner mass scale is unconstrained but there is
               strong motivation for the weak scale
                                                                     * J. Feng hep-ph/0405215v2

       LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                J.R.Incandela
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                                  SUSY and the weak scale




                                                                                       Cancellation
• Higgs mass:
          • correction has quadratic divergence!
                  •  a cut-off scale – e.g. Planck scale
• Superpartners fix this:
                  • Need same coupling 
                  • Need superpartners at the weak scale
                          • Otherwise the logarithmic term becomes too large, which would require
                            more fine-tuning.
                          • Known as “soft” SUSY-breaking terms (others are possible)

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                           J.R.Incandela
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                             SUSY Spectrum of Neutrals*
                                                                                 Mass
                                                                                 parameters




          • Need 2 Higgs doublets
                  • Avoids triangle anomalies (divergent process involving a fermion
                    triangle loop with gauge bosons at the vertices)
          • Elegant choice Hu and Hd
                  • They give mass to up- and down-like fermions separately
                          • Helps evade large Flavor Changing Neutral Currents (FCNC)
          • Neutral Spectrum:
                  • Spin 0 sneutrinos, spin 3/2 gravitino, spin ½ Bino, Wino, and Higgsinos
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                    J.R.Incandela
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                                                        Spectrum (cont.)
          • The 4 spin ½ neutral SUSY partners only differ in their
            electroweak quantum nos.
                  • With SUSY broken, they are free to mix to form mass eigenstates
                          • These are the neutralinos k with k=1,2,3,4
                          • These fermions are Majorana (particle=antiparticle)
          • Beyond neutrals - spectrum as expected
                  • Fermion (boson) superpartner for each SM boson (fermion)




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008               J.R.Incandela
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                                                                 R-Parity
          • Superpartners solve some and create other problems
                  • Gauge hierarchy problem eliminated
                  • But now protons decay too rapidly
                          • Superpartners mediate both L and B number violation




          • Need a new symmetry: R parity conservation
                  R = (-1)3(B-L)+2S where B,L,S=Baryon #, Lepton #, and Spin
                          R= +1 (-1) for all SM particles (SUSY partners)
          • Consequence: Lightest SUSY Particle (LSP) stable
                  • Cannot decay into SM particles
                  • And … impact of SUSY spectrum on SM particles is diminished

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008               J.R.Incandela
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                                                 SUSY breaking (SB)
          • What is the LSP?
                  • Must understand how SUSY is broken
                          • specifies soft SUSY breaking terms & so the mass spectrum
          • SUSY breaking is a vast and technical subject!
                  • Popular models assume a hidden sector is involved:
                          • Sounds ad-hoc, but there is a precedent: Electroweak Symmetry
                            Breaking (EWSB)




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                     J.R.Incandela
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                                                                      Mediation
        • EWSB divides SM interactions into 3 sectors
               1. “EWSB”: involving only the Higgs
               2. “Observable”: gauge bosons, quarks and leptons
               3. “Mediation”: involving the interactions between sectors
                  1 and 2 (i.e. Yukawa interactions)
                      •       Higgs obtains non-zero vacuum expectation value (vev) and
                              this occurrence is communicated to the SM fermions via some
                              unknown mediator.
        • Same concept applies to SUSY breaking
               1. “SUSY-Breaking”: Fields Z not in SM
               2. “Observable”: SM particles and their superpartners
               3. “Mediation”: all interactions between SUSY-breaking
                  fields Z and observable fields

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008               J.R.Incandela
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                                                    SUSY Breaking
          • Simplest cases, one field Z has non-zero vev F
                  • Gravitino acquires mass m3/2 = F/(3 M*)
                          • M* = (8GN)-½  2.4 x 1018 GeV (reduced Planck mass)
                  • Mediation sector terms for Z interacting with
                    superpartners become mass terms when Z F




          ~
          f, =superpartners of SM fermions and gauge bosons



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008        J.R.Incandela
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                                                                      Models
          • Supergravity Models
                  • Mediating interactions are gravitational: Mm ~ M*
                          • m3/2, mḟ, m ~ F/ M*
                          • F ~ (Mweak M*)  1010 GeV
                   High Scale SUSY-Breaking
                          Any superpartner OR the Gravitino could be the LSP
          • Gauge-Mediated (GMSB)
                  • Mediating fields are gauge fields: Mm  M*
                          • m3/2 = F/(M*3) mḟ, m ~ F/ Mm
                          • F ~ (Mweak Mm)  1010 GeV
                   Low-scale SUSY-breaking
                           Gravitino = LSP



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008             J.R.Incandela
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                                                             SUSY Models
          • Spectrum depends on how SUSY breaks
                  • Infinite possibilities
                  • Can narrow the field with several assumptions
                          • Assume weak-scale SUSY derives from something more
                            fundamental (e.g. Grand Unification or String theories)
                          • Assume the fundamental theory is highly structured
          • Why highly structured?
                  • Partly driven by aesthetics (simplicity)
                  • Also because the gauge couplings unify
                          • Occurs in SUSY models that are run up to higher energy via
                            the renormalization group equations




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008              J.R.Incandela
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                                     Gauge Coupling Unification




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                           Minimal Supergravity (mSUGRA)
          • Thus, the idea is the following:
                  • The many (>100) parameters of weak-scale SUSY
                    should be derived from a minimal set of parameters at
                    the unification scale.
          • mSUGRA: the “canonical” model
                  • 5 main parameters
                          • mo , m1/2 , Ao , tan(b), and sign(m)
                  • mo , m1/2 are universal scalar and fermion masses
                          • Like the couplings, one assumes that the spectra of
                            fundamental particles derives from fundamental masses
                  • m3/2 is a 6th free parameter
                          • Gravitino - could be LSP but in most of the literature it is
                            assumed to be very heavy and ignored.


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                   J.R.Incandela
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              An example of renormalization group evolution
              of universal SUSY masses in mSUGRA
                                                                      • Generally valid features:
                                                                         • Evolving from GUT scale
                                                                            • Gauge couplings increase SUSY
                                                                              masses
                                                                            • Yukawa couplings decrease them
                                                                         • Thus
                                                                            • Colored particles are heavy  Not
                                                                              LSP candidates
                                                                            • Bino is the lightest gaugino
                                                                            • Right-handed slepton the lightest
                                                                              scalars (specifically stau ÌR)
                                                                         • (mHu)2 is driven negative by the
                                                                           large top Yukawa coupling!


                                                                      What is this about?
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                   J.R.Incandela
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                              Minimization of the EWK potential for
                              Electroweak Symmetry Breaking
                                                                      • At tree level EWSB requires



                                                                         • True for all but lowest
                                                                           values of tan(b) (which are
                                                                           disfavored anyway)
                                                                         • Can only be satisfied if
                                                                           (mHu)2 <0
                                                                         • No other mass parameters
                                                                           are so significantly affected
                                                                           by the large top Yukawa
                                                                           coupling
   A large top mass then has a                                          A natural explanation of
   significant role in SM                                               why SU(2) is the only SM
   phenomenology through SUSY                                           symmetry that is broken
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                               J.R.Incandela
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                                    Minimal SUSY Higgs Sector
          • Minimal Case of 2 doublets:
                 • After W,Z masses, 5 remaining d.o.f.
                        • 5 physical Higgs bosons ho, Ho, Ao, H
                        • Scalar potential has one free parameter
                 • Masses are expressed in terms of mA and tanb
                 tanb = v2/v1 and v12+ v22 = v2
                 Where v1 (v2) are the vev‟s for the Hd (Hu)
                 • Large radiative corrections (at one-loop)
                        • Mh2 < MZ2 + (3GF/(21/2p2)) Mt4 ln(1+m2/Mt2)
                        • Mh  130 GeV
                              150 GeV (if there are also Higgs singlet(s))
          • Important feature
                        • Couplings to vector bosons now shared
                               ghoVV2 + gHoVV2 = gHVV2 (SM)

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008           J.R.Incandela
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                                                   Back to the LSP
                                                                      • Scan parameter space
                                                                        for LSP possibilities
                                                                        • One slice through
                                                                          mSUGRA shown here




          • The LSP in mSUGRA
                  • Lightest neutralino c1 or the RH stau ÌR
          • Many other models exist
                  • But mSUGRA contains a very wide variety of
                    phenomenological possibilities and LSP candidates
                   Useful for studying a broad array of signatures. This is
                    what is done in CMS.
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                       J.R.Incandela
     Dark Matter




   Another motive for
R-Parity-Conserving SUSY
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                                                                      R. Kolb at SUSY07 Karlsruhe
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                                                            The Dark Side
                 • Matter is only 5% of the energy in the universe.
                         • Cosmology-Astrophysics evidence for physics beyond the
                           Standard Model (BSM) is overwhelming
                 • Relic Density for non-baryonic dark matter:
                         • 0.094 < DM h2 < 0.129 (95% CL), h = 0.71 (km/s)/Mpc
                           (Hubble expansion)
                 • Weak scale SUSY with R-Parity conservation is
                   perhaps the best-motivated framework
                         •    Provides a natural dark matter candidate (neutralino)
                         •    Leads to remarkable gauge coupling unification
                         •    Can provide an explanation for why SU(2) is broken
                         •    Solves the gauge hierarchy problem



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008             J.R.Incandela
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                                         Thermal Relic Density
                                                                      • Weakly Interacting Massive
                                                                        Particles (WIMPs)
                                                                         • Mass and annihilation
                                                                           xsec set by weak scale
                                                                           m2 ~ sA v-1 ~ Mwk2
                                                                         • Thus a 300 GeV WIMP
                                                                           freezes out at T ~ 10 GeV
                                                                           and t~10-8 s
          • As universe expands                                          • The freeze-out density is:
                                                                         ~ 10-10 GeV-2/ sA v
                  • Interactions/annihilations
                    cease at a time that                                 • Typical weak xsec:
                    depends on annihilation                              sA v~a2/Mwk2~10-9 GeV-2
                    cross section sA times
                    mean velocity v                                           h2 ~0.1
                  • Freeze out condition:
                          • Neq ~ sAv~T2/M*
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                            J.R.Incandela
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                                                            Beyond SUSY
          • Though SUSY looks very compelling, theorists
            have proposed many alternatives and we do not
            know which if any is the right one …
                  •    Strong dynamics
                  •    Grand Unified theories
                  •    Little Higgs
                  •    String-theory motivated models
                          • ADD Large extra dimension
                          • Randall Sundrum warped extra dimension
          • More on this later…




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008       J.R.Incandela
Before presenting results of all of the
studies done by ATLAS and CMS…


     The experimentalist‟s perspective
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                                                                      prologue
          • “Inputs, from LEP and from HERA, beautifully merge into the tools
            that have been developed to describe proton-antiproton collisions at
            the Tevatron, where the agreement between theoretical predictions
            and data confirms that the key assumptions of the overall approach
            are robust. ….”*
                  *Michelangelo Mangano:
                          Understanding the Standard Model, as a bridge to the discovery of
                            new phenomena at the LHC http://arxiv.org/abs/0802.0026v2
                          I draw upon the contents of this paper at various places in this talk.


                  • We come to the LHC from a variety of previous accelerator
                    complexes (LEP, HERA, SLAC, Tevatron…) and non-acclerator
                    experiments. This is a good thing, the job will take all of our
                    collective effort and experience …




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                         J.R.Incandela
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                                 Past versus future discoveries
                  • W&Z
                          • Masses and production rates were predicted
                          • Signals stood out “like being hit on the head with a hammer”
                          • Interpretation was unambiguous
                  • Top
 Past




                          • Signal was a bit harder to dig out (initially a counting experiment) and
                            less straightforward to interpret but…
                          • We knew it had to be “somewhere”
                          • Production and decay properties were predicted
                  • Higgs
                          • Like top – for a given mass, we know its production and decay
                            properties in the SM and alternative BSMs. For some masses, counting
  Future




                            experiments may be the first sign.
                          • Or maybe like W & Z –the signal could appear as a striking mass peak
                  • New Physics (NP)
                          • Don‟t know what to expect. Theory provides examples, some are
                            compelling, none are guaranteed ...
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                        J.R.Incandela
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                                                            BSM Billboard




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                                                         BSM Signatures
                                                                      • A few thoughts …
                                                                         • Model builders provide ideas for
                                                                           unexpected signatures
                                                                           • Very uncertain that any of these
                                                                             models will be seen, but there are
                                                                             benefits
                                                                             • We prepare more broadly
                                                                             • We are motivated to look at generic
                                                                               things from a different perspective
                                                                                • e.g. very boosted top quarks,
                                                                                  very high ET leptons,
                                                                                  triggering on jets when there‟s
                                                                                  no beam!
                                                                         • The number and variety of
                                                                           theories are indicative of
                                                                           something else…
                                                                      • What is really needed, is data.

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                   J.R.Incandela
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                                                    Our job description
                  • Efficiently acquire all interesting data and understand it in detail, as it
                    unfolds with increasing luminosity
                  • Understand the SM to the extent our data and existing MC allow (with
                    likely development and tuning of the latter due to the former)
                  • And then to see what is there that we cannot explain
                  • Not be biased by any particular models
                  • Be like Faraday. Listen to theorists but do not be too influenced. Observe
                    nature as purely as possible with methods that are continually refined by
                    experience.
                  • “If we see something odd in a given final state, it is not by appealing to, or
                    freshly concocting, a new physics model that gives rise to precisely this
                    anomaly that makes the signal more likely or more credible. The process
                    of discovery … should be based solely on the careful examination of
                    whether indeed this signal violates the SM expectation.” M.L.Mangano
          • “Our analyses should be designed “to provide the extraordinary
            evidence that is needed to back up an extraordinary claim”



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                      J.R.Incandela
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                                            Good things come early

                                                                      So far, hadron
                                                                      colliders have
                                                                      an unbroken
                                                                      streak of
                                                                      discovery
                                                                      opportunities

                                                                      Low mass SUSY
                                                                      or some other
                                                                      source of Dark
                                                                      Matter could
                                                                      appear early




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                                                                 SUSY Signatures
                                                                      • Different topologies for new
                                                                       physics will overlap different SM
                                                                       processes. Examples
                                                                         • Jets + MET (but no leptons)
                                                                            • Backgrounds: QCD,(tt, Z+Jets, tW)
                                                                         • Jets + MET+2 OS leptons
                                                                            • Background: mainly tt


                                                                      • Different classes of observations
                                                                       require different levels of scrutiny
                                                                         • A mass peak or edge is self-
                                                                           calibrating and unambiguous but
                                                                            • “… almost certainly pass through a
                                                                              period where the signal is marginal.”
                                                                         • Anomalous kinematics are more
                                                                           tricky but can be a smoking gun
                                                                         • A counting experiment requires the
                                                                           most effort to be fully convincing


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                    J.R.Incandela
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                                                                 SUSY Signatures
                                                                      • Different topologies for new
                                                                       physics will overlap different SM
                                                                       processes. Examples
                                                                         • Jets + MET (but no leptons)
                                                                            • Backgrounds: QCD,(tt, Z+Jets, tW)
                                                                         • Jets + MET+2 OS leptons
                                                                            • Background: mainly tt


                                                                      • Different classes of observations
                                                                       require different levels of scrutiny
                                                                         • A mass peak or edge is self-
                                                                           calibrating and unambiguous but
                                                                            • “… almost certainly pass through a
                                                                              period where the signal is marginal.”
                                                                         • Anomalous kinematics are more
                                                                           tricky but can be a smoking gun
                                                                         • A counting experiment requires the
                                                                           most effort to be fully convincing


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                    J.R.Incandela
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                                                       SM at 10-14 TeV


                                                                      • A new window on Nature
                                                                        • We „ll see portions of the SM
                                                                          that have never been seen.
                                                                        • A lot of it will look familiar but
                                                                          will be ornamented with jets to
                                                                          a degree that we have not
                                                                          previously encountered
                                             QCD
                                             Jets




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                J.R.Incandela
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                                                       SM at 10-14 TeV
                                                                      • Low initial luminosity
                                                                        • Study Min Bias
                                                                           • Narrow down the current large
                                                                             range of extrapolations of PDFs,
                                                                             dN/dh etc
                                                                        • Study Jets
                                                                           • Initial optimization of jet algorithms
                                                                             on real data for resolution, scale,
                                                                             lepton and g fakes, etc.
                                             QCD                         • Then more complex final states
                                             Jets                     • Also calibrate with known objects
                                                                        • Study candles for leptons and photons
                                                                           • o,,  initially to understand detector,
                                                                             tracking, leptons & other objects
                                                                           • Extend to W or Z leptons
                                                                      • Compare to MC V+Jets
                                                                      • Extend into tt core region and then
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008
                                                                      • Deal with tails…             J.R.Incandela
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                              “The LHC is a very Jetty place”*




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
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                                      Life at low x in a pp collider
• LHC ≠ Tevatron
         • Small momentum fractions x
           in many key searches:
             • large phase space for gluon
               emission
         • Consider tt:
             • For a jet threshold of ~15 GeV,
               essentially all tt events will
               have 1 or more additional jets
                                                                      160.0
         • Consider V+jets                                            140.0
             • Ratio of LHC to Tevatron                               120.0
               production cross sections for                          100.0
               W/Z + n jets becomes huge as                            80.0                         W+jets
               n increases                                             60.0                         Z+jets
                                                                       40.0
                                                                       20.0
                                                                        0.0
                                                                              0   2   4   6

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                           J.R.Incandela
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              V+jets a bridge between data and theory
                                                                      • Theory has (generally) kept pace
                                                                         • W+jets a key background for top
                                                                           discovery. Estimated with data+MC
                                                                      • Recent CDF results versus theory:
                                                                         • Top Left : pTjet for Z+  1j, Z +  2j
                                                                         • Bottom: W+n jets
                                                                            • Very good agreement at NLO
                                                                            • MEPS matching routines – also
                                                                              agree up to a constant k factor




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                      J.R.Incandela
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                                W+Jets: Jet ET spectra at LHC
 http://arxiv.org/abs/0802.0026v2
                                                                      Projected ET
                                                                      spectra of nth jet
                                                                      (n=1,2,3,4) in
                                                                      W+ n jet events at
                                                                      the LHC using
                                                                      various MEPS
                                                                      MC and compared
                                                                      to Alpgen

                                                                      With one exception
                                                                      all are within 50%




  • Studies in data are greatly facilitated by ratios
           • [Z+(n+1)jets] / [Z+n jets]
           • [W+n jets] / [Z+ n jets]
  • Many systematics cancel at least partially
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008           J.R.Incandela
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                                                                tt at 14 TeV
                                                                      • Next we have to deal with tt
                                                                        • The additional jets complicate
                                                                          reconstruction/isolation of top.
                                                                          • Top is not like W or Z
                                                                          • “Top is not a candle, it‟s more like a
                                                                            candelabra”
                                                                               – Ken Bloom (U. Nebraska)


                                                                        • Once we understand the control
                                                                          regions: W/Z + n jets for low n, and
                                             QCD                          QCD fakes, we can begin to tackle
                                             Jets
                                                                          the core regions of tt.
                                                                        • Then, have to understand the tails
                                                                          • If there is a substantial BSM signal
                                                                            overlapping any region of top, this
                                                                            will be a difficult job and we will likely
                                                                            have to rely even more on MC than
                                                                            we did for V+jets

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                       J.R.Incandela
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                                               Also study tt by n jets




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                                     The Devil will be in De Tails




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                                                     New Physics (NP)
                                                                      • New physics will also occupy some
                                                                        part(s) of this space
                                                                          • Leptons for top are not different
                                                                            than leptons for SUSY
                                                                          • Work done in SM groups can be
                                                                            directly translatable to NP
                                                                            searches
                                                                      • Event selection should reflect both
                                                                        the need to study control regions
                                                                        and the commonality of topologies
                                             QCD
                                                                         • Inclusivity of Triggers, Skims to allow
                                             Jets
                                                                           • Data driven QCD bkgd estimates
                                                                           • Fakes estimates, cross-checks
                                                                         • Common event selections will
                                                                           facilitate comparisons
                                                                           • More people study and help to
                                                                             understand a given sample


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                    J.R.Incandela
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                   SM processes we can‟t initially isolate: single top
           • Accounted as backgrounds even before we can show they are there
           • They are thus not critical to very early searches but will become very
             useful as data accumulates.
  • Single top
           • Window to new physics:
                • t‟, W‟, FCNC, SUSY
           Access to top properties

  • Also Dibosons


           • t channel 9.9% @10fb-1
           • W-associated ~20% @ 10 fb-1
           • S-channel 36% @10fb-1


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008          J.R.Incandela
  OK now to the studies…


And what new physics might look like
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                  New Physics Searches with CMS & ATLAS
        • Sources: Physics Technical Design Report Vol. II
               • J. Phys. G. Nucl. Part. Phys. 34 (2007) 995-1579
                  • General Focus: low luminosity (2 x 1033) operation and
                     integrated luminosities up to 30-60 fb-1
                  • Also considered very early data from a few pb-1 to a few fb-1
               • Will draw on this work for this talk
                  • Can‟t cover it all (fortunately for you) not an expert all areas
               • Highlight areas where new physics could reveal itself early
        • CMS now preparing for really early data: 10 pb-1 -100 pb-1
               • Many new studies are underway and some completed. See 2008
                 results:
               • http://cms-physics.web.cern.ch/cms-physics/physics-home.htm
        • ATLAS results shown here can be found at
               • https://twiki.cern.ch/twiki/bin/view/Atlas/AtlasPhysics

        • 1000‟s of pages of documented studies
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008             J.R.Incandela
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              Spectacular LHC Events Soon to Come!




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
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                          CMS SUSY Benchmark Points (PTDR)
 • Selection of 13
   Points
           • Low mass
             LM1LM9
           • High mass
             HM1HM4
 • Important: different
   topologies/decay
   modes, i.e. on
   different signatures
           • LM1,2,6,9 are also                                       * LM8
             close to WMAP
             benchmarks
                                                                              *LM9



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                  J.R.Incandela
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                                             Signature based analyses
    • A Variety of inclusive analyses @ a specific
      benchmark points then extended to the m1/2-mo plane
      using FAMOS (CMS fast detector simulation)
              •    MET + jets @ LM1: MET>200
              •    Muons + MET + jets @ LM1: MET>130
              •    Same sign di-muons @ LM1: MET>200
              •    Opposite sign dileptons @ LM1:MET>200
                                                       ~
              •    Di-taus @ LM2 : ~ 02 decays 95% to tt: MET>150
                                     c
              •    Inclusive analysis with Higgs @LM5:MET>200
              •    Inclusive Zo @LM4:MET>230
              •    Inclusive top @ LM1: Top plus leptons: MET>150



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008     J.R.Incandela
                                             LM1: MET and 3 jets
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                                                                      • Cleanup instrumental
                                                                        bkds, halo, cosmics, etc.
                                                                         • E.g. require
                                                                            • primary vertex
                                                                            • Total EM fraction
                                                                              Fem>0.175
                                                                                • Fem = ET weighted EM
                                                                                  fraction in |h|<3
                                                                            • Event charged
                                                                              fraction Fch>0.1
                                                                                • Fch = PT of charged
                                                                                  tracks associated to
                                                                                  jets over calorimeter
                                                                                  jet ET in |h|<1.7



        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                         J.R.Incandela
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                                                MET in QCD events
                                                                      • MET in QCD multijet
                                                MET in QCD              events tends to be along
                                                multijet events
                                                                        leading or 2nd leading jet
                                                                        directions
                                                                      • SUSY populates a
                                                                        distinct region




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                          J.R.Incandela
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                                                 QCD MET from data




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
                  Calibrate ZnØ + jets with Z mm +jets
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                                                                           Concern:
                                                                           Model the ZnØ
                         Selected ZnØ+  2jets                            background using
                                                                           Z mm is great but
                                                                           takes a lot of data
                                                  Selected Zmm +         to get enough
                                                  2jets with PT(Z) > 200
                                                                           dimuon events.
                                                  Muons excluded
                                                                           Couple alternatives
                                                                           recently considered




                      Selected Zmm +  2jets
                      with PT(Z) > 200
                      Muons included




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                   J.R.Incandela
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                                                              Using W+jets




                                                                             Yes !
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                  J.R.Incandela
                                                             Using g + jets!
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                                                                      Eg in g + jets   Z just a massive g

                                                                      EZ in Z + jets   But you don‟t pay the
                                                                                       branching ratio penalty

                                                                                       BR(Z mm) ~ 3%




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                   J.R.Incandela
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                                                       Jets + Missing ET

                          Low mass SUSY




                                                                      MET
                                                                      LM1




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008         J.R.Incandela
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                                                   Final event counts




          • Final Cuts on ET of j1,j2,HT > 180,110,500 GeV
          • Global signal efficiency 13%, S/B~26




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008     J.R.Incandela
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                                   Inclusive SUSY searches




          • Low-mass SUSY (Msp~500GeV) accessible with O(100 pb-1)
            Dt to discovery determined by:
                  • Time to understand detector performance: MET tails, jet performance &
                    energy scale, lepton id
                  • Time to collect control samples -- e.g. g+jets, W+jets, Z+jets, WW, top..


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                   J.R.Incandela
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                                                                      HM1




          • Prior to data, backgrounds are not really known….
                  • More of a relevant issue for High Mass (HM) points

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008         J.R.Incandela
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                                    Inclusive MET + Jets + 1 lepton
   • Add lepton  clean trigger
                                                                                         ATLAS
             • Important during early running!

   • Typical Characteristics:
      • Single Isolated lepton
                     • Low pT ~ 20-30 GeV
             •  3 or  4 jets:
                     • Hard leading (& NL) Jets
             • Large MET
                     • Typically > 100 GeV                            Meff > 100 GeV

             • Cuts on D(jets, MET)
             • Large Meff

   • Main remaining backgrounds                                                        1 fb-1
                                                                                                Control Region :
      • ttbar, W/Z+n-Jets                                              Signal Region :
                                                                        Meff > 100 GeV            Meff < 100 GeV




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                  J.R.Incandela
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                                   Inclusive MET + Jets + 2 leptons
        • Add 1 Same Flavor Lepton
                • Even cleaner
                • Little to no QCD
        • Typical Selection Strategy
                • Several, high pT Jets
                • Large MET
                • Strong lepton isolation cuts                        p   
                                                                              d
                                                                              u
        • Main backgrounds                                                    u     
                                                                                              d       nm
                                                                                                       m
                                                                                  W
                • tt                                                              g ,Z   W
                                                                                         W             m
                • Double boson                                                u
                                                                                  W
                                                                                              d       nm
                        • 2 OS SF :           W+W-,
                                          WZ, ZZ                      p      u
                        • 2 SS SF : W+W+, W-W-                                d
                            ~unique to LHC


                • Double partons not yet studied
                        • W “+” W, W “+” Z, Z “+” Z


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                               J.R.Incandela
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                                   Inclusive MET + Jets + 2 leptons

                                                                      2 OS SF Leptons
                                                                      L = 1 fb-1




                                              2 SS SF Leptons


                                                                                        L = 1 fb-1


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                      J.R.Incandela
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                                 SUSY signals (cascades)
                               
                                     ~
                                     g    q     q
                                                                      ~                           b
                                                                     q       c2
                                                                               0
c
   0
    2                                                                              h                     b
                           
                                                                         c
                                                                             0
                                                                              2
                                                        c10  ETmiss                       c10  ETmiss

                         1 fb-1

                                                                                              Can be
                                                                                              discovery
                                                                                              channel
                   M(bb)                                                                      for the
                                                                                       0
                                           
                                                                                   h          Higgs




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                            J.R.Incandela
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                              Expected CMSSM Discovery Reach
          • As a function of integrated                                            ATLAS
            luminosity                                                              Preliminary
                                                                                                         without systematics

          • For different discovery
            channels (1 fb-1)                                                                   SN-ATLAS-2002-020
                                CMSSM:


                              CMS Preliminary 1 fb-1
                                               Phys. Lett. B, 657/1-3 (2007)
                                               Preferred region @ 95%CL:




                                                                               Expected Tevatron Reach

                            Discoverable with just 6 pb-1
                            Excludable with less than 1 fb-1!
                                                                               ATLAS Similar




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                             J.R.Incandela
            What we see may be difficult to interpret

• Minimal Universal Extra Dimensions                   Datta, Matchev, Kong
                                                 q
   • 1 Extra compact dimension: R                      Phys.Rev. D72 (2005) 096006


   • Everything propagates in Bulk                          l  (near)
   • KK tower of “SM-like” states                                         
                                                                        l (far)
      • evenly separated
      • nearly degenerate
• Signatures like low mass SUSY!
   • Many Jets                            CMS AN 2006/008
   • Large MET (KK parity  stable LKP)
                                                     CMS
   • Leptons
                                                     Preliminary
      • With OS dilepton mass edges
   • High cross-section
      • Early Physics Potential
• Current constraints:
   • R-1 > 600 Gev (for mH >115 GeV)
           Gauge Mediated Breaking of SUSY
•   SUSY broken at lower scale by Gauge Bosons               ATLAS
     •   Couple to “messengers” from hidden sector at
         some high energy scale Fo
     •   Gravitino becomes LSP
     •   Neutralino can be NLSP

•   Distinctive Signature
     •   Large MET
     •   Large Meff
     •   High ET photon
           •   NLSP Lifetime  large ct Non-pointing
           •   Prompt NLSP decays  Pointing
           •   Depends on SUSY breaking scale!
•   Interesting Phenomenology                            ATLAS
     •   From Eg , L, ct
                                                         Prel.
     •   Can derive mNLSP and thus SUSY Breaking Scale
                                                             CMS Prel.
                                                                         100 pseudo
                                                                         experiments
•   Early Discover Potential                                             of 10 fb-1
     •   N = 1 ; tan b = 1 ; sgn[m] = +1 ;
         Mm = 280 GeV ;  = 140 Gev
     •   O(1) fb-1
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                                    Anomalous jets, dijet cross-sections
              Substructure, contact interactions, high mass resonances
   1 fb-1 is well into new territory:
   Jets up to ~3-3.5 TeV
   Di-jet masses up to ~5-6 TeV

                                                        CDF

                                                                      Deviation from SM




        Challenges: Jet energy scale,
                     Parton density functions (PDF),
                     underlying event, trigger, jet definition

        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                       J.R.Incandela
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                             Dijet xsec ratio and new Physics




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008   J.R.Incandela
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                                                 High mass dimuons:
                          Z‟, graviton resonances, large extra dimensions…
              Tracking: alignment and propagation muons  tracker important
              As noted yesterday: Mass resolution (and so discovery potential)
              not too strongly affected by tracker alignment scenario


                          Z’




                                                                      Efficiencies from data
        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                            J.R.Incandela
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                          Track Momentum resolution: 10-1000 pb-1



                                                                      pT resolution integrated over h




    Z peak visible with first rough alignments




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                               J.R.Incandela
                   Early LHC Discovery Potential

Model                       Mass reach                              Luminosity (fb-1)        Early Systematic Challenges
Contact Interaction          < 2.8 TeV                                       0.01              Jet Z’@6TeV Scale
                                                                                                    Eff., Energy
 Z’
                               ADD X-dim@9TeV                              SUSY@3TeV
                                                                                                      Alignment

3000
 ALRM                       M ~ 1 TeV                                       0.01
 SSM                        M ~ 1 TeV                                         0.02
 LRM                        M ~ 1 TeV
                                          Compositeness@40TeV                 0.03
 E6, SO(10)                 M ~ 1 TeV                                      0.03 – 0.1
                          H(120GeV)gg
Excited Quark               M ~0.7 – 3.6 TeV                                   0.1                 Jet Energy Scale
300
                Higgs@200GeV TeV
Axigluon or Colouron  M ~0.7 – 3.5                                             0.1                 Jet Energy Scale
E6 diquarks                 M ~0.7 – 4.0 TeV                                   0.1                 Jet Energy Scale




                                                                SHUTDOWN
Technirho     SUSY@1TeV – 2.4 TeV
                     M ~0.7                                                    0.1                 Jet Energy Scale




                                                                             200 fb-1/yr
 30
ADD Virtual GKK             MD~ 4.3 - 3 TeV, n = 3-6                           0.1                    Alignment
                            MD~ 5 - 4 TeV, n = 3-6                              1
ADD Direct GKK              MD~ 1.5-1.0 TeV, n = 3-6                           0.1              MET, Jet/photon Scale
SUSY                        M ~1.5 – 1.8 TeV                                    1            MET, Jet Energy Scale, Multi-
Jet+MET+0 lepton            M ~0.5 TeV                                        0.01            Jet backgrounds, Standard
                                                                                                  Model backgrounds
Jet+MET+1 lepton           10-20 TeV
                            M ~0.5                                             0.1
Jet+MET+2 leptons
                           fb /yr
                            M ~0.5 TeV
                             -1             100 fb-1/yr                        0.1         1000 fb-1/yr
mUED                        M ~0.3 TeV                                        0.01                       ibid
                            M ~ 0.6 TeV                                         1
TeV-1 (ZKK(1))              Mz1 < 5 TeV                                          1
RS1     2008                2010               2012          2014                    2016          2018               2020
di-jetsEarly     LHC       M ~0.7- 1 TeV,
                       Runs: 0.1 to0.8 fb-1
                              G1                c=0.1                          0.1                 Jet Energy Scale
di-muons                    MG1~0.8- 2.3 TeV,   c=0.01-0.1                      1                     Alignment
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                       Maybe nature has some REAL SURPRISES in store…



                                                                                   Large extra dimensions,
                                                                                    Planck scale ~ EW scale

                                                                                   Possible micro black hole
                                                                                    production; decay via
                                                                                    Hawking radiation into
                                                                                    photons, leptons, jets…

                                                                                   CMS and ATLAS might see
                                                                                   this with 1-100 pb-1 !




                                                                      sphericity
                                                                                            From P. DeJong
                                                                                            Moriond 2007




        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                                  J.R.Incandela
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                                                                      Summary
          • There are good reasons to believe that there is
            something new at the energy scales accessible to the
            LHC that could appear early.
          • Indications are that ATLAS and CMS will be ready to
            exploit this opportunity.
          • Many studies documented in PTDR
          • Much achieved, but much more to learn
                  • Focus on the first data (0.01 to 1.0 fb-1) from now until first
                    collisions
                  • Many improvements in tools and our understanding of our
                    capabilities are expected
          • Initial detector performance and speed of optimization
            will be crucial


        LHC Lectures NCTU, Hsin Chu, Taiwan, March 31-April 3, 2008                   J.R.Incandela

								
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