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UED Modelling with CalcHEP

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UED Modelling with CalcHEP Powered By Docstoc
					                                                                  Royal Holloway

                                 UED                         University of London




                 Universal Extra Dimensions


        Tony Poll (Southampton University)‫‏‬
             Dr Tracey Berry (RHUL)‫‏‬
  Dr Alexander Belyaev (Southampton University)‫‏‬

                        Summer 2008



31 August 2008          Tony Poll - Southampton University              1
                                                              Royal Holloway
                                                         University of London



                        Content
    Beyond the Standard Model
    Extra Dimensions
    CalcHEP – particle decay and collisions tool
    Decay Chains and Signatures
    Cross Sections and Branching Ratios
    Next steps


31 August 2008      Tony Poll - Southampton University
                                                                  Royal Holloway
                                                             University of London



                 Beyond the Standard Model

•   BSM theories have been proposed to explain
      •   Dark matter
      •   Hierarchy problem - Relative weakness of the
          gravitational force
      •   Cosmological constant problem
      •   Strong CP problem
•   Many alternate BSM theories
      •   Super-Symmetry, Strings, ED etc

31 August 2008          Tony Poll - Southampton University              3
                                                                   Royal Holloway
                                                              University of London



                   Alternate ED Models

•   MUED – Minimal Universal Extra Dimensions
      •   'Minimal' – only one extra dimension
      •   'Universal' – all SM particles extend into the ED
•   ADD – (Arkani-Hamed, Dimopoulos, Dvali)‫‏‬
      •   Only the graviton extend into several extra
          dimensions
•   RS – Randall-Sundrum
      •   Only the graviton extends into one highly warped
          extra dimensions
31 August 2008           Tony Poll - Southampton University              4
                                                                    Royal Holloway
                                                               University of London



                     New ED Particles

•   MUED predicts new massive particles
      •   Kaluza-Klein (KK) particles
      •   Same spin & coupling as SM particles
•   KK particles have excitation modes
      •   First excitation mode graviton: g1, etc.
      •   Limited to 20 levels in this project




31 August 2008            Tony Poll - Southampton University              5
                                                              Royal Holloway
                                                         University of London



                 Extra Dimensions

•   ED‫‏‬particles‫‏‬are‫‏‬in‫‏‬the‫‏‬extra‫‏‬dimension‫'‏‬bulk‘
•   ED particles only appear at small dimensions
•   New ED particles are 'dark matter' candidates




31 August 2008      Tony Poll - Southampton University              6
                                                                             Royal Holloway
                                                                        University of London



                               MUED Particles

•   KK particle mass
      •   mn2 = n2/R2 + mSM2
            •    n = excitation mode
                  •   n = 0 is the SM
            •    R = Compactification radius
•   Theory cut off when the number of excitation
    modes, ΛR, = 20



31 August 2008                     Tony Poll - Southampton University              7
                                                                   Royal Holloway
                                                              University of London



                            CalcHEP
•   CalcHEP (Calculator for High Energy Physics)‫‏‬
•   Program for modelling particle collisions and decays
•   E.g. A proton proton collision creating two daughter
    particles would be entered as:
      •   p,p->2*x
•   CalcHEP defines particles and parameters
•   E.g. Protons consist of quarks, anti-quarks and gluons
      •   p: u,U,d,D,G
•   Particle mass and cross-section are defined
31 August 2008           Tony Poll - Southampton University              8
                                                                        Royal Holloway
                                                                   University of London



                       CalcHEP Models
 Defined by:
    Particles
         E.g. W±, Z, gluon, up-quark, down-quark, anti-quarks etc
    Parameters
         Zmass, tmass, etc
    Constraints
         E.g. Wmass = Zmass x Cos(Weinberg angle)‫‏‬
    Vertices
         Feynman rules

31 August 2008                Tony Poll - Southampton University              9
                                                               Royal Holloway

                 Sample E,e→ 2 x X                        University of London




                 Feynman Diagrams




31 August 2008       Tony Poll - Southampton University             10
                                                                     Royal Holloway
                                                                University of London



                  CalcHEP MUED Model
•   MUED CalcHEP model provided by Datta, Kong &
    Matchev (Amended by Belyaev)‫‏‬which defined:
•   New particles
      •   E.g. SM + KK particles e.g. g1, ~eL
•   New parameters
      •   R-inverse, Number of KK levels (ΛR)‫‏‬
•   New constraints
      •   E.g. R = 1/R-inverse, KK1 up-quark mass etc
•   Vertices (Feynman rules)‫‏‬
31 August 2008             Tony Poll - Southampton University             11
                                                                 Royal Holloway

                 p,p->e,E,B1,B1 Feynman                     University of London




                         Diagrams




31 August 2008         Tony Poll - Southampton University             12
                                                                       Royal Holloway
                                                                  University of London



                    Collision Sub-Processes
•   Many possible sub-processes in p,p collisions
         p,p →‫ 2‏‬x X creates1549 sub-processes
                E.g. U,u→b,~SB;‫‏‬D,d→~Su,~SU‫‏‬etc
•   Highest cross-sections are estimated to be for
    processes involving the strong interactions:
      •   p,p‫‏→‏‬g1,g1
      •   p,p‫‏→‏‬Q1/q1 Q1/q1
      •   p,p‫‏→‏‬g1,Q1/q1
•   Our‫‏‬initial‫‏‬investigation‫‏‬focused‫‏‬on‫‏‬p,p‫‏→‏‬g1,g1
31 August 2008               Tony Poll - Southampton University             13
                                                                                          Royal Holloway
                                                                                     University of London



                             The decay
Signature: p,p →‫‏‬q,q,e,E,B1 + q,q,e,E,B1
p,p →‫‏‬g1,g1                                 (proton,proton‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

      ↓
      g1→q1,q                               (KK‫‏‬gluon‫‏→‏‬KK‫‏‬quark‫‏+‏‏‬quark)‫‏‬

                 ↓
                 q1→Z1,q                    (KK‫‏‬quark‫‏→‏‬KK‫‏‬Z‫‏+‏‏‬quark)‫‏‬

                    ↓
                    Z1→‫‏‬l1,l∓               (KKZ‫‏→‏‬KK‫‏‬lepton‫‏+‏‏‬lepton)‫‏‬

                           ↓
                           l1→B1,l±         (KK‫‏‬lepton‫‏→‏‬KK‫‏‬photon‫‏+‏‬OSSF‫‏‬lepton)‫‏‬
31 August 2008               Tony Poll - Southampton University                                14
                                                                           Royal Holloway
                                                                      University of London



                                   Signature
•   Signature: p,p →‫‏‬q,q,e,E,B1 + q,q,e,E,B1
•   Can only observe SM particles at the LHC
      •   4 hadronic jets (q,q,q,q)‫‏‬
      •   4 leptons (e,E,e,E)‫‏‬
•   MUED particles (B1)‫‏‬are‫‏‬implied‫‏‬by‫‏‬the‫'‏‬missing‫‏‬energy‘
      •   I.e. Missing transverse energy, Etmiss
•   B1: KK photon, lightest KK particle (LKP), stable
•   Characteristic hadronic jets and leptons may indicate KK
    particles in the extra dimension.

31 August 2008                   Tony Poll - Southampton University             15
                                                                         Royal Holloway
                                                                    University of London



                              Parameters
•   Radius of ED
      •   Modelled as R-inverse over the range 100 – 2000 Gev

   Number of KK excitation levels
      •   Held constant at 20 in this series of calculations
•   Higgs mass in the SM
      •   Held constant at 120 GeV in this series of calculations




31 August 2008                Tony Poll - Southampton University              16
                                                                     Royal Holloway
                                                                University of London



                                Method
•   For R-inverse ranging from 100 – 2000 GeV
•   Calculate‫‏‬cross‫‏‬section‫(‏‬CS)‫‏‬for‫‏‬p,p‫‏→‏‬g1,g1
•   Calculate the branching ratio for each line in the decay
    chain.
      •   E.g. BR for g1→q,q1; q1→q,‫‏‬Z1; Z1→l∓,l1; l1→l±,B1
•   Total‫‏‬CS‫(‏‬p,p→q,q,e,E,B1 + q,q,e,E,B1)‫‏‬
      •   =‫‏‬CS(p,p‫‏→‏‬g1,g1) x
      [BR(g1→q,q1) x BR( q1→q,‫‏‬Z1) x BR( Z1→l∓,l1) x BR( l1→l±,B1)]2


31 August 2008             Tony Poll - Southampton University             17
                                                                                          Royal Holloway
                                                                                     University of London



                   Reminder of the decay
Signature: p,p →‫‏‬q,q,e,E,B1 + q,q,e,E,B1
p,p →‫‏‬g1,g1                                 (proton,proton‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

      ↓
      g1→q1,q                               (KK‫‏‬gluon‫‏→‏‬KK‫‏‬quark‫‏+‏‏‬quark)‫‏‬

                 ↓
                 q1→Z1,q                    (KK‫‏‬quark‫‏→‏‬KK‫‏‬Z‫‏+‏‏‬quark)‫‏‬

                    ↓
                    Z1→‫‏‬l1,l∓               (KKZ‫‏→‏‬KK‫‏‬lepton‫‏+‏‏‬lepton)‫‏‬

                           ↓
                           l1→B1,l±         (KK‫‏‬lepton‫‏→‏‬KK‫‏‬photon‫‏+‏‬OSSF‫‏‬lepton)‫‏‬
31 August 2008               Tony Poll - Southampton University                                18
                                                                                     Royal Holloway

                    Initial collision and                                       University of London




                        Sub-process
3 significant, mutually exclusive initial collisions:
     p,p‫‏→‏‏‬g1,g1                   (p,p‫‏→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

     p,p‫‏→‏‏‬q1,Q1                   (p,p‫‏→‏‬KK‫‏‬quark‫‏+‏‬KK‫‏‬anti-quark)‫‏‬

     p,p‫‏→‏‏‬g1,Q1/q1                (p,p‫‏→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬quark‫‏‬or‫‏‬KK‫‏‬anti-quark)‫‏‬

4 mutually exclusive sub-processes of each collision. E.g.
     u,U‫‏→‏‬g1,g1                    (u + anti-u‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

     U,u‫‏→‏‬g1,g1                    (anti-u‫‏+‏‬u‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

     d,D‫‏→‏‬g1,g1                    (d + anti-d‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

     D,d‫‏→‏‬g1,g1                    (anti-d‫‏+‏‬d‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

Consider the first sub-process:
     u,U‫‏→‏‬g1,g1                    (u + anti-u‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬
31 August 2008            Tony Poll - Southampton University                              19
                                   Royal Holloway
                              University of London

Invariant Mass Distribution
  R-Inverse = 1000 GeV
                           Royal Holloway

     p,p→g1,g1        University of London




Transverse Momentum
                                                                                          Royal Holloway
                                                                                     University of London



                       u,U Decay Chain
u,U →‫‏‬g1,g1                                 (proton,proton‫→‏‬KK‫‏‬gluon‫‏+‏‬KK‫‏‬gluon)‫‏‬

      ↓
      g1→q1,q                               (KK‫‏‬gluon‫‏→‏‬KK‫‏‬quark‫‏+‏‏‬quark)‫‏‬

                 ↓
                 q1→Z1,q                    (KK‫‏‬quark‫‏→‏‬KK‫‏‬Z‫‏+‏‏‬quark)‫‏‬

                    ↓
                    Z1→‫‏‬l1,l∓               (KKZ‫‏→‏‬KK‫‏‬lepton‫‏+‏‏‬lepton)‫‏‬

                           ↓
                           l1→B1,l±         (KK‫‏‬lepton‫‏→‏‬KK‫‏‬photon‫‏+‏‬OSSF‫‏‬lepton)‫‏‬



31 August 2008               Tony Poll - Southampton University                                22
  Invariant Mass of e + E             Royal Holloway
                                 University of London




R-Inverse = 200 - 2000 GeV

    R-inv = 200 GeV    R-inv = 500 GeV




    R-inv = 1000 GeV   R-inv = 2000 GeV
Transverse Momentum of e              Royal Holloway
                                 University of London




R-Inverse = 200 - 2000 GeV

    R-inv = 200 GeV    R-inv = 500 GeV




    R-inv = 1000 GeV   R-inv = 2000 GeV
Transverse Momentum of E              Royal Holloway
                                 University of London




R-Inverse = 200 - 2000 GeV

    R-inv = 200 GeV    R-inv = 500 GeV




    R-inv = 1000 GeV   R-inv = 2000 GeV
                                                                                                                                                                                                                               Royal Holloway
                                                                                                                                                                                                                          University of London



                                                                  Decay Branching Ratios
                                                                     g1->q,q1                                                                                                  q1->q,Z1
                                100.00                                                                                                              100
                                          90.00                                                                                                           90
                                          80.00                                                                                                           80
    Branching Ration (%)




                                          70.00                                                                                                           70




                                                                                                                    Branching Ratio (%)
                                                                                            Total(g1->q,q1)                                               60
                                          60.00
                                                                                            g1->q, q1: d, SD
                                          50.00                                                                                                           50                                            q1->q,Z1: u, Z1
                                                                                            g1->q, q1: c, DC
                                          40.00                                             g1->q, q1: u, DU                                              40
                                                                                            g1->q, q1: u, SU                                              30
                                          30.00
                                          20.00                                                                                                           20
                                          10.00                                                                                                           10
                                                                                                                                                          0
                                                 0.00
                                                                                                                                                               0       500    1000       1500    2000
                                                        0   500     1000      1500   2000
                                                                                                                                                                       R-inverse (GeV)
                                                            R-inverse (GeV)


                                                                   Z1->e,~EL                                                                                                  ~EL->e,B1
                                                 100                                                                                                      100
                                                   90                                                                                                      90
                                                   80                                                                                                      80




                                                                                                                                    Branching Ratio (%)
                           Branching Ratio (%)




                                                   70                                                                                                      70
                                                   60                                                                                                      60
                                                   50                                       Z1->l,l1: e,                                                   50                                            l1->l, B1: e,
                                                                                            ~EL                                                            40                                            B1
                                                   40
                                                   30                                                                                                      30
                                                   20                                                                                                      20
                                                   10                                                                                                      10
                                                    0                                                                                                       0
                                                        0   500    1000       1500   2000                                                                          0    500    1000       1500   2000

                                                            R-inverse (GeV)                                                                                             R-inverse (GeV)



31 August 2008                                                                                Tony Poll - Southampton University                                                                                                    26
                                                                                                                                                                                                   Royal Holloway

                                            Cross Sections and Decay                                                                                                                          University of London




                                                Branching Ratios

                                              p,p->g1, g1 Cross Section                                                                            Combined: g1->q,q,e,E,B1 Branching Ratio
                                                                                                                                      0.060
                       1200.000


                                                                                                                                      0.050
                       1000.000


                                                                                                                                      0.040
                        800.000




                                                                                                                Branching Ratio (%)
                                                                                        CS:‫‏‬p,p‫‏→‏‬g1,‫‏‬g1‫(‏‬pb)
Cross-section (pb)




                                                                                                                                                                                                        BR: Combined: g1-
                                                                                                                                      0.030
                        600.000                                                                                                                                                                         >q,q,e,E,B1



                        400.000                                                                                                       0.020



                        200.000                                                                                                       0.010



                          0.000                                                                                                       0.000
                                  0   200   400 600 800 1000 1200 1400 1600 1800 2000                                                         0   200   400   600   800 1000 1200 1400 1600 1800 2000

                                                   R-inverse (GeV)                                                                                             R-inverse (GeV)




                     31 August 2008                                           Tony Poll - Southampton University                                                                                            27
                                                                                                                            Royal Holloway
                                                                                                                       University of London



                                           Combined Decay CS
                                                             p,p->q,q,e,E,B1+
                                                                 q,q,e,E,B1
                               0.300




                               0.250




                               0.200
          Cross-section (pb)




                                                                                                                 CS * BR^2
                               0.150




                               0.100




                               0.050




                               0.000
                                       0   200   400   600    800    1000   1200   1400     1600   1800   2000

                                                             R-inverse (GeV)



31 August 2008                                         Tony Poll - Southampton University                                        28
                 Total Cross-Sections                             Royal Holloway
                                                             University of London




                 for all Sub-processes
    CalcHEP UI produces CS for each sub-process
         E.g. u,U->e,E,B1,B1
    Use subproc_cycle batch command to calculate
     total cross section for all sub-processes




31 August 2008          Tony Poll - Southampton University             29
                                                                      Royal Holloway
                                                                 University of London



                            Next Steps
•   Calculate events from CS
•   Investigate all possible 4 lepton combinations:
      •   4e,‫4‏‬μ,‫2‏‬e‫2‏+‏‬μ
•   Investigate other significant sub-processes:
      •   p,p‫→‏‬Q1,‫‏‬q1‫‏‬and‫‏‬p,p‫‏→‏‬g1,Q1/q1
•   Mitigate backgrounds (ZZ, tt, bbbb, Zbb) by kinematic
    limits, transverse energy cuts, and dilepton invariant
    mass.


31 August 2008              Tony Poll - Southampton University             30
                                                                     Royal Holloway
                                                                University of London



                           Summary
    Extra Dimensions may resolve issues with the Standard Model
    Minimal Universal Extra Dimensions theory could be verified by
     experimental evidence from ATLAS
    CalcHEP is a powerful tool for modelling particle collisions and
     decays
    MUED decay chains, cross sections, branching ratios and
     signatures have been calculated for a range of dimensions
    Next steps: Event prediction, alternate collision and decay
     chains, background mitigation



31 August 2008            Tony Poll - Southampton University
                                                              Royal Holloway
                                                         University of London



                 Acknowledgements
    Minimal Universal Extra Dimensions in
     CalcHEP/CompHEP: A. Datta, K. Kong & K.
     Matchev
    New Physics at the LHC: A Les Houches
     Report: Four Leptons + Missing Energy from
     One UED: M. Grigg & P. Ribeiro




31 August 2008      Tony Poll - Southampton University             32
                                                           Royal Holloway
                                                      University of London



                  Appendix




31 August 2008   Tony Poll - Southampton University             33
                                                               Royal Holloway

             4 Leptons + Missing Energy                   University of London




                   from One UED
    M. Gigg & P. Ribeiro
    Multi-lepton signatures and detection with CMS
    Description of event selection
    Distinguishing between MUED and SUSY




31 August 2008       Tony Poll - Southampton University
                                                                         Royal Holloway
                                                                    University of London


         MUED Cross-Sections for R-
         Inverse and Selection Cuts
                                              Sample Selections:
                                                     L1: Level 1 trigger
                                                     HLT: High level trigger
                                                     ε2x≥2 OSSF: At least
                                                      2 OSSF leptons
                                                     ETmiss: missing
                                                      transverse energy
                                                     Zveto: Rejecting ZZ
                                                      background
31 August 2008   Tony Poll - Southampton University                           35
                                                                  Royal Holloway

                 MUED Discovery Potential                    University of London




                       with CMS




31 August 2008          Tony Poll - Southampton University             36
with CMS




31 August 2008          Tony Poll - Southampton University            36

				
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