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Particle Physics Experiments.ppt

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					             Particle Physics

    Outline:
   Why do particle physics?
   Standard model
   particle physics is high energy physics
   accelerators
   detectors
   triggers, data recording
   analysis
   interpretation

   Webpages of interest
     http://www-d0.fnal.gov (Fermilab homepage)
     http://sg1.hep.fsu.edu/~wahl/Quarknet/index.html
      (has links to many particle physics sites)
     http://www.fnal.gov/pub/tour.html
      (Fermilab particle physics tour)
     http://ParticleAdventure.org/
      (Lawrence Berkeley Lab.)
     http://www.cern.ch (CERN -- European Laboratory
      for Particle Physics)
           Goals of particle physics
   particle physics or high energy physics
    •  is looking for the smallest constituents of
       matter (the “ultimate building blocks”) and for
       the fundamental forces between them;
      aim is to find description in terms of the
       smallest number of particles and forces
       (“interactions”)
      at given length scale, it is useful to describe
       matter in terms of specific set of
       constituents which can be treated as
       fundamental;
       at shorter length scale, these fundamental
       constituents may turn out to consist of smaller
       parts (be “composite”).
         in 19th century, atoms were considered smallest
          building blocks,
         early 20th century research: electrons,
          protons, neutrons;
         now evidence that nucleons have substructure -
          quarks;
         going down the size ladder: atoms -- nuclei --
          nucleons -- quarks -- preons ???... ???
       Issues of High Energy Physics
    Why?
     To understand more organized forms of matter
     To understand the origin and destiny of the
      universe.
   Basic questions:
     Are there irreducible building blocks?
        Are there few or infinitely many?
        What are they?
        What are their properties?
     What is mass?
     What is charge?
     What is flavor?
     How do the building blocks interact?
     Why are there 3 forces?
       gravity, electroweak, strong
       (or are there more?)
            Standard Model
   A theoretical model of interactions
    of elementary particles
   Symmetry:
    SU(3) x SU(2) x U(1)
   “Matter particles”
    quarks
       up, down, charm,strange, top bottom
    leptons
       electron, muon, tau, neutrinos

   “Force particles”
    Gauge Bosons
        (electromagnetic force)
       W, Z (weak, elctromagnetic)
       g gluons (strong force)

   Higgs boson
    spontaneous symmetry breaking of
     SU(2)
    mass
Standard Model
                          Building Blocks
     Fundamental Forces: Bosons


Force         Boson        Mass(GeV)       Strength
ravity         G?              ?            51039
 E-M                          0             1/137
Weak            W           80.42            10-5
                Z0          91.188
trong         g(rgb)           0             0: r0
                                             : r

     Point-like Particles: Fermions
            Particle        Charge           Mass (MeV)
            Leptons
         e               0      <0.01     <0.17     <18
         e                  1     0.511     105.6    1777
           Quarks
         u   c    t             300       1500    175000
         d   s    b              300       500      4500
      Matter constituents and force
                carriers




   (1994 summary from the Contemporary Physics
    Education Project at LBNL)

       And top is very very heavy !!!




   This mass (175 GeV/c2) is ~ 40x larger than the
    next most massive quark. Is this just an
    “accident” or does it point to some deeper truth
    about the nature of Electroweak symmetry
    breaking ?
Brief History of the Standard Model
   Late 1920’s - early 1930’s: Dirac, Heisenberg, Pauli,
    & others extend Maxwell’s theory of EM to include
    Special Relativity & QM (QED) - but it only works
    to lowest order!
   1933: Fermi introduces 1st theory of weak
    interactions, analogous to QED, to explain b decay.
   1935: Yukawa predicts the pion as carrier of a new,
    strong force to explain recently observed hadronic
    resonances.
   1937: muon is observed in cosmic rays
   1938: heavy W as mediator of weak interactions?
    (Klein)
   1947: pion is observed in cosmic rays
   1949: Dyson, Feynman, Schwinger, and Tomonaga
    introduce renormalization into QED - most accurate
    theory to date!
   1954: Yang and Mills develop Gauge Theories
   1950’s - early 1960’s: more than 100 hadronic
    “resonances” have been observed !
   1962 two neutrinos!
   1964: Gell-Mann & Zweig propose a scheme whereby
    resonances are interpreted as composites of 3
    “quarks”. (up, down, strange)
Brief History of the Standard Model
                     (continued)
    1970: Glashow, Iliopoulos, Maiani: 4th quark
     (charm) explains suppression of K decay into 

    1964-1967:spontaneous symmetry breaking
     (Higgs, Kibble)

    1967: Weinberg & Salam propose a unified Gauge
     Theory of electroweak interactions, introducing
     the W,Z as force carriers and the Higgs fieldto
     provide the symmetry breaking mechanism.

    1967: deep inelastic scattering shows “Bjorken
     scaling”
    1969: “parton” picture (Feynman, Bjorken)

    1971-1972: Gauge theories are renormalizable
     (t’Hooft, Veltman, Lee, Zinn-Justin..)

    1972: high pt pions observed at the CERN ISR

    1973: Gell-Mann & Fritzsch propose that quarks
     are held together by a Gauge-Field whose quanta,
     gluons, mediate the strong force Quantum
     Chromodynamics
    1973: “neutral currents” observed (Gargamelle
     bubble chamber at CERN)
Brief History of the Standard Model
                      (continued)

   1975: J/ interpreted as cc bound state
    (“charmonium”)
   1974: J/ discovered at BNL/SLAC;
   1976:  lepton discovered at SLAC
   1977:  discovered at Fermilab in 1977,
    interpreted as bb bound state (“bottomonium”)
     3rd generation

   1979: gluon “observed” at DESY
   1982: direct evidence for jets in hadron hadron
    interactions
   1983: W, Z observed at CERN

   1995: top quark found at Fermilab (D0, CDF)
   2000: direct evidence for tau neutrino () at
    Fermilab (DONUT experiment)
                 Collisions at the Tevatron
   pp Collisions  qq(g) Interact’s


                     Underlying
                       Event
             u                                       u
    g
                 q

     d   q       u                               d       u


                                  Hard Scatter



Fermilab
         Questions at the Tevatron
   The Standard Model
       Electro-Weak (EM + Weak Interact’s)
            W,Z, + quarks & leptons
            Most Accurate Theory ever !
             (but only for fundamental particles)
            Simple Processes  Real Tests
       QCD (Strong Force)
            gluons & quarks
            High E  Accurate Predictions
             Low E  Not a simple Theory
            Range of E’s accessible for partons in proton
       Properties of Particles
            All Quarks and Leptons Produced
             (only place for top quark)
            All Gauge Bosons………..almost
            What about the Higgs?
                 More Questions
   The SM works great !
    Why change it ?
       Has 18 arbitrary parameters
         Where do they come from ?
       Is the Higgs really what we think it should be
        ?
   2 Strategies:
       Look Harder                      Precision
       Get a Bigger Hammer     Energy
   The Tevatron is well suited to both of
    these strategies
                  Fermilab Upgrade



          Param            Run I         Run II
    ECM           [TeV]     1.8             2.0
Bunch X-ing
     Freq       [kHz]      290       2500         7500
    Time         [ns]      3500       396          132
  Bunches
      N                    66       3636    121121
       p        [1010]      23         27        27
    anti-p      [1010]     5.5          3         3
    Lumi      [cm2s1]   21030     21032    21032
     Ldt       [pb1]     125             2000
Inter’s/X-ing              2.5        5.8       2.3
   Rates
Inelastic pp              100 kHz        10 Mhz
  PpWX                   0.04 Hz         4.4 Hz
   pptt                  500 tot       4 / hour
              D Upgrade




Sub-System         Run I            Run II
 Magnets
 Solenoid            none             2T
  Toroid              2T              2T
 Tracking      Drift Chambers    Silicon Vtx
                     TRD         Scint Fibers
                                  Pre-Shower
Calorimetry        ULar        New electronics
                Cu,SSLAr
  Muons         Drift Tubes     Add Chambers
                Scintillators
  Trigger        2 Levels          3 Levels
                Experimental
             High Energy Physics
   Method
     Subject matter to extreme temperatures and
      densities.
       Energy ~ 2 trillion eV
       Temperature ~ 24,000 trillion K
       Density ~ 2000 x nuclear density
     Accelerate sub-atomic particles, to closer
      than 100 millionth the speed of light, and
      arrange for them to collide head on.
     Study the debris of particles that emerges
      from the collisions.
               Example
         Creating Top Quarks

                                 e   uc
                                        

                b (-1/3)



                             
                                  e    d s
         t (+2/3)    W
P (+1)                                P (-1)

                t (-2/3)

                     W   
                                 e   u c
                                        


          b (+1/3)

                                  e    d s
         Research Program




   DØ Experiment
     To study 2 TeV proton antiproton
      collisions
     Fermilab, Batavia, Illinois
     Next run begins in April 2001
   CMS Experiment
     To study 14 TeV proton antiproton
      collisions
     CERN, Geneva, Switzerland
     First run begins in 2005
   Hellaz Experiment
     To study 1 MeV neutrinos from the Sun.
      When?!!!
       Particle physics experiments
   Particle physics experiments:
     collide particles to
        produce new particles
         reveal their internal structure and laws of
         their interactions by observing regularities,
         measuring cross sections,...
     colliding particles need to have high energy
        to make objects of large mass
        to resolve structure at small distances
     to study structure of small objects:
         need probe with short wavelength: use
         particles with high momentum to get short
         wavelength
        remember de Broglie wavelength of a particle
          = h/p
     in particle physics, mass-energy equivalence
      plays an important role; in collisions, kinetic
      energy converted into mass energy;
        relation between kinetic energy K, total energy
         E and momentum p : ___________
                E = K + mc2 = (pc)2 + (mc2)c2
                   About Units
   Energy - electron-volt
     1 electron-volt = kinetic energy of an electron
      when moving through potential difference of
      1 Volt;
        1 eV = 1.6 × 10-19 Joules = 2.1 × 10-6 W•s
        1 kW•hr = 3.6 × 106 Joules = 2.25 × 1025 eV


   mass - eV/c2
        1 eV/c2 = 1.78 × 10-36 kg
        electron mass = 0.511 MeV/c2
        proton mass = 938 MeV/c2
        professor’s mass (80 kg)  4.5 × 1037 eV/c2


   momentum - eV/c:
        1 eV/c = 5.3 × 10-28 kg m/s
        momentum of baseball at 80 mi/hr
                5.29 kgm/s  9.9 × 1027 eV/c
    How to do a particle physics experiment

    Outline of experiment:
      get particles (e.g. protons, antiprotons,…)
      accelerate them
      throw them against each other
      observe and record what happens
      analyse and interpret the data
    ingredients needed:
      particle source
      accelerator and aiming device
      detector
      trigger (decide what to record)
      recording device
      many people to:
         design, build, test, operate accelerator
         design, build, test, calibrate, operate, and
         understand detector
        analyse data
      lots of money to pay for all of this
     How to get high energy -collisions
   Need Ecom to be large enough to
         allow high momentum transfer (probe small
          distances)
                                                -
         produce heavy objects (top quarks, Higgs boson)
                                             _
         e.g. top quark production: e+e- tt,
                 _        _
           -
          qq  tt, gg  tt, …

   Shoot particle beam on a target (“fixed target”):
                   _____
          Ecom = 2Emc2 ~ 20 GeV for E = 100 GeV,
                                      m = 1 GeV/c2




   Collide two particle beams (“collider :
          Ecom = 2E ~ 200 GeV for E = 100 GeV
       How to make qq collisions, cont’d
   However, quarks are not found free in nature!
   But (anti)quarks are elements of (anti)protons.
   So, if we collide protons and anti-protons we should
                           _
                -
    get some qq collisions.




   Proton structure functions give the probability that
    a single quark (or gluon) carries a fraction x of the
    proton momentum (which is 900 GeV/c at the
    Tevatron)
                  Accelerator
   accelerators:
       use electric fields to accelerate particles,
        magnetic fields to steer and focus the beams
       synchrotron:
        particle beams kept in circular orbit by
        magnetic field; at every turn, particles “kicked”
        by electric field in accelerating station;
       fixed target operation: particle beam
        extracted from synchrotron, steered onto a
        target
       collider operation:
        accelerate bunches of protons and antiprotons
        moving in opposite direction in same ring; make
        them collide at certain places where detectors
        are installed
    Fermilab accelerator complex



              ACCELERATORS
   are devices to increase the energy of
    charged particles;
     use magnetic fields to shape (focus and bend)
      the trajectory of the particles;
     use electric fields for acceleration.
   types of accelerators:
     electrostatic (DC) accelerators
        Cockcroft-Walton accelerator (protons up to 2
        MeV)
        Van de Graaff accelerator (protons up to 10
        MeV)
       Tandem Van de Graaff accelerator (protons up
        to 20 MeV)
     resonance accelerators
       cyclotron (protons up to 25 MeV)
       linear accelerators
           – electron linac: 100 MeV to 50 GeV
           – proton linac: up to 70 MeV
     synchronous accelerators
       synchrocyclotron (protons up to 750 MeV)
       proton synchrotron (protons up to 900 GeV)
       electron synchrotron (electrons from 50 MeV
        to 90 GeV)
     storage ring accelerators (colliders)
           ACCELERATORS, cont’d
   electrostatic accelerators:
     generate high voltage between two
       electrodes  charged particles move in
                       electric field,
      energy gain = charge times voltage drop;
     Cockcroft-Walton and Van de Graaff
       accelerators differ in method to achieve
       high voltage.
   proton linac (drift tube accelerator):
     cylindrical metal tubes (drift tubes) along axis
      of large vacuum tank
     successive drift tubes connected to opposite
      terminals of AC voltage source
     no electric field inside drift tube  while in
      drift tube, protons move with constant
      velocity
     AC frequency such that protons always find
      accelerating field when reaching gap between
      drift tubes
     length of drift tubes increases to keep drift
      time constant
     for very high velocities, drift tubes nearly of
      same length (nearly no velocity increase when
      approaching speed of light)
                Accelerators,          cont’d


   cyclotron
     consists of two hollow metal chambers called
        (“dees” for their shape, with open sides which are
        parallel, slightly apart from each other (“gap”)
       dees connected to AC voltage source - always one
        dee positive when other negative  electric field in
        gap between dees, but no electric field inside the
        dees;
       source of protons in center, everything in vacuum
        chamber;
        whole apparatus in magnetic field perpendicular to
        plane of dees;
       frequency of AC voltage such that particles always
        accelerated when reaching the gap between the
        dees;
        in magnetic field, particles are deflected:
        p = qBR p = momentum, q = charge,
                    B = magnetic field strength,
                    R = radius of curvature
       radius of path increases as momentum of proton
        increases time for passage always the same as long
        as momentum proportional to velocity
        this is not true when velocity becomes too big
        (``relativistic change of mass'')
      Accelerators: “relativistic effects”
   “relativistic effects”
     special relativity tells us that certain
      approximations made in Newtonian mechanics
      break down at very high speeds;
     relation between momentum and velocity in
      “old” (Newtonian) mechanics: p = m v becomes
                                 ________
      p = mo v , with  = 1/1 - (v/c)2
      mo = “rest mass”, i.e. mass is replaced by
                         rest mass times 
                - “relativistic growth of mass”
     factor  often called “Lorentz factor”;
      ubiquitous in relations from special relativity;
      energy: E = moc2
     acceleration in a cyclotron is possible as long
      as relativistic effects are negligibly small, i.e.
      only for small speeds, where momentum is still
      proportional to speed; at higher speeds,
      particles not in resonance with accelerating
      frequency; for acceleration, need to change
      magnetic field B or accelerating frequency f
      or both;
              Accelerators,        cont’d


   electron linac
     electrons reach nearly speed of light at small
      energies (at 2 MeV, electrons have 98% of
      speed of light);
      no drift tubes; use travelling e.m. wave inside
      resonant cavities for acceleration.
   synchrocyclotron:
     B kept constant, f decreases;
   synchrotron :
     B increases during acceleration,
      f fixed (electron synchrotron)
      or varied (proton synchrotron);
      radius of orbit fixed.
          Particle detectors,          cont’d

   Scintillator:
     energy liberated in de-excitation and capture
      of ionization electrons emitted as light -
      ``scintillation light'’
     light channeled to photomultiplier in light
      guide (e.g. optical fibers);
     scintillating materials: certain crystals (e.g.
      NaI), transparent plastics with doping (fluors
      and wavelength shifters)
   proportional tube:
     metallic tube with thin wire in center, filled
      with gas, HV between wall (-, “cathode”) and
      central wire (+,”anode”);  strong electric
      field near wire;
     charged particle in gas  ionization 
      electrons liberated;
     electrons accelerated in electric field  can
      liberate other electrons by ionization which in
      turn are accelerated and ionize  “avalanche
      of electrons” moves to wire  current pulse;
      current pulse amplified  electronic signal:
     gas is usually noble gas (e.g. argon), with some
      additives e.g. carbon dioxide, methane,
      isobutane,..) as “quenchers”;
           Particle detectors,         cont’d

   multi wire proportional chamber:
     contains many parallel anode wires between two
      cathode planes (array of prop.tubes with
      separating walls taken out)
     operation similar to proportional tube;
     cathodes can be metal strips or wires  get
      additional position information from cathode
      signals.
   drift chamber:
     field shaping wires and electrodes on wall to
      create very uniform electric field, and divide
      chamber volume into “drift cells”, each containing
      one anode wire;
     within drift cell, electrons liberated by passage
      of particle move to anode wire, with avalanche
      multiplication near anode wire;
     arrival time of pulse gives information about
      distance of particle from anode wire; ratio of
      pulses at two ends of anode wire gives position
      along anode wire;
            Particle detectors,       cont’d


   Cherenkov detector:
     measure Cherenkov light (amount and/or
      angle) emitted by particle going through
      counter volume filled with transparent gas
      liquid, aerogel, or solid  get information
      about speed of particle.
   calorimeter:
     “destructive” method of measuring a particle's
      energy: put enough material into particle's way
      to force formation of electromagnetic or
      hadronic shower (depending on kind of
      particle)
     eventually particle loses all of its energy in
      calorimeter;
     energy deposit gives measure of original
      particle energy.
   Note:
    many of the detectors and techniques
    developed for particle and nuclear
    physics are now being used in medicine,
    mostly diagnosis, but also for therapy.
Identifying particles
     Particle Identification




                         Muon B&C
                        Magnet
                        Muon A-Layer
                        Hadronic
                        Layers
                            Calorimeter
                         EM Layers

                        Central Tracking
                        Beam Axis
e      jet     
What do we actually “see”

   tt e  jets
        Muon

                                 Jet-1




Jet-2
                          Missing energy

               Electron
                    Detectors
   Detectors
     use characteristic effects from interaction of
      particle with matter to detect, identify
      and/or measure properties of particle; has
      “transducer” to translate direct effect into
      observable/recordable (e.g. electrical) signal
     example: our eye is a photon detector;
     “seeing” is performing a photon scattering
      experiment:
       light source provides photons
       photons hit object of our interest -- some
        absorbed, some scattered, reflected
       some of scattered/reflected photons make it
        into eye; focused onto retina;
       photons detected by sensors in retina
        (photoreceptors -- rods and cones)
       transduced into electrical signal (nerve pulse)
       amplified when needed
       transmitted to brain for processing and
        interpretation
Particle interactions with matter
 electromagnetic interactions:
   excitation
   ionization
   Cherenkov radiation
   transmission radiation
   bremsstrahlung
   photoelectric effect
   Compton scattering
   pair production
 strong interactions:
   secondary hadron production,
   hadronic showers


 detectors usually have some amplification
  mechanism
    Interaction of particles with matter
    when passing through matter,
      particles interact with the electrons and/or
      nuclei of the medium;
      this interaction can be electromagnetic or
      strong interaction, depending on the kind of
      particle; its effects can be used to detect the
      particles;
    possible interactions and effects in
     passage of particles through matter:
      excitation of atoms or molecules (e.m. int.):
         charged particles can excite an atom or
          molecule (i.e. lift electron to higher energy
          state);
          subsequent de-excitation leads to emission of
          photons;
      ionization (e.m. int.)
         electrons liberated from atom or molecule, can
          be collected, and charge is detected
      Cherenkov radiation (e.m. int.):
         if particle's speed is higher than speed of light
          in the medium, e.m. radiation is emitted --
          “Cherenkov light” or Cherenkov radiation, which
          can be detected;
         amount of light and angle of emission depend on
          particle velocity;
Interaction of particles with matter, cont’d

 transition radiation (e.m. int.):
    when a charged particle crosses the boundary
     between two media with different speeds of light
     (different “refractive index”), e.m. radiation is
     emitted -- “transition radiation”
     amount of radiation grows with (energy/mass);
 bremsstrahlung (= braking radiation) (e.m. int.):
    when charged particle's velocity changes, e.m.
     radiation is emitted;
    due to interaction with nuclei, particles deflected
     and slowed down emit bremsstrahlung;
     effect stronger, the bigger (energy/mass) 
     electrons with high energy most strongly
     affected;
 pair production (e.m. int.):
     by interaction with e.m. field of nucleus, photons
     can convert into electron-positron pairs
 electromagnetic shower (e.m. int.):
    high energy electrons and photons can cause
     “electromagnetic shower” by successive
     bremsstrahlung and pair production
 hadron production (strong int.):
     strongly interacting particles can produce new
     particles by strong interaction, which in turn can
     produce particles,... “hadronic shower”
       Examples of particle detectors

   photomultiplier:
     photomultiplier tubes convert small light
      signal (even single photon) into detectable
      charge (current pulse)
     photons liberate electrons from
      photocathode,
     electrons “multiplied” in several (6 to 14)
      stages by ionization and acceleration in high
      electric field between “dynodes”, with gain 
      104 to 1010
     photocathode and dynodes made from
      material with low ionization energy;
     photocathodes: thin layer of semiconductor
      made e.g. from Sb (antimony) plus one or more
      alkali metals, deposited on glass or quartz;
     dynodes: alkali or alkaline earth metal oxide
      deposited on metal, e.g. BeO on Cu (gives high
      secondary emission);
       Examples of particle detectors

   Spark chamber
     gas volume with metal plates (electrodes);
      filled with gas (noble gas, e.g. argon)
     charged particle in gas  ionization 
      electrons liberated;
       string of electron - ion pairs along particle
      path
     passage of particle through “trigger counters”
      (scintillation counters) triggers HV
     HV between electrodes  strong electric
      field;
     electrons accelerated in electric field  can
      liberate other electrons by ionization which in
      turn are accelerated and ionize  “avalanche
      of electrons”, eventually formation of plasma
      between electrodes along particle path;
     gas conductive along particle path
       electric breakdown  discharge  spark
     HV turned off to avoid discharge in whole gas
      volume
     Examples of particle detectors, contd
   Scintillation counter:
     energy liberated in de-excitation and capture
      of ionization electrons emitted as light -
      “scintillation light”
     light channeled to photomultiplier in light
      guide (e.g. piece of lucite or optical fibers);
     scintillating materials: certain crystals (e.g.
      NaI), transparent plastics with doping (fluors
      and wavelength shifters)
   Geiger-Müller counter:
     metallic tube with thin wire in center, filled
      with gas, HV between wall (-, “cathode”) and
      central wire (+,”anode”);  strong electric
      field near wire;
     charged particle in gas  ionization 
      electrons liberated;
     electrons accelerated in electric field 
      liberate other electrons by ionization which in
      turn are accelerated and ionize  “avalanche
      of electrons”; avalanche becomes so big that
      all of gas ionized  plasma formation 
      discharge
     gas is usually noble gas (e.g. argon), with some
      additives e.g. carbon dioxide, methane,
      isobutane,..) as “quenchers”;
The D0 detector
                   DØ Calorimeter




   Uranium-Liquid Argon sampling calorimeter
      Linear, hermetic, and compensating
   No central magnetic field!
      Rely on EM calorimeter
 Forward Mini-drift                            Forward Scintillator
                        Central Scintillator
 chambers




Shielding
                                                                      D Upgrade




New Solenoid, Tracking System
Si, SciFi,Preshowers

                           + New Electronics, Trig, DAQ
                   D Upgrade Tracking

     Silicon Tracker
        Four layer barrels (double/single sided)
        Interspersed double sided disks
        793,000 channels
     Fiber Tracker
        Eight layers sci-fi ribbon doublets (z-u-v, or z)
        74,000 830 m fibers w/ VLPC readout
                                                    1.1
Preshowers                          cryostat

Central
   Scintillator strips                                      1.7
       – 6,000 channels

     Forward
       –   Scintillator strips
       –   16,000 channels
Solenoid
       –2T   superconducting
                  Silicon Tracker
      50 cm                                1/2 of detector



                                                             3




7 barrels     12 Disks “F”           8 Disks“H”



       1/7 of the detector   (large-z disks not shown)




                                 387k ch in 4-layer double
                                 sided Si barrel (stereo)




                                405k ch in interspersed
                                disks (double sided stereo)
                                and large-z disks
       Silicon Tracker -Detectors
   Disks
     “F” disks wedge (small diameter):
        144 double sided detectors, 12 wedges = 1disk
        50m pitch, +/-15 stereo
       7.5cm long, from r=2.5 to 10cm, at
        z=6,19,32,45,50,55 cm
     “H” disk (large diameter):
       384 single sided detectors
       50 m pitch
       from r=9.5-20 cm, z= 94, 126 cm
   Barrels
     7 modular, 4 layer barrel segments
     single sided:
       layers 1 , 3 in two outermost barrels.
     double sided:
       layers 1, 3 have 90o stereo (mpx’d 3:1)
         50 & 100m pitch, 2.1 cm wide
       layers 2,4 have small angle stereo (2o)
         50 & 62.5m pitch, 3.4 cm wide

                   12cm
                                      two detectors
                                      wire bonded
                       Trigger
   Trigger = device making decision on
        whether to record an event
   why not record all of them?
       we want to observe “rare” events;
       for rare events to happen sufficiently often, need
        high beam intensities  many collisions take place
       e.g. in Tevatron collider, proton and antiproton
        bunches will encounter each other every 132ns
       at high bunch intensities, every beam crossing
        gives rise to collision 
              about 7 million collisions per second
       we can record about 20 to (maybe) 50 per second
   why not pick 10 events randomly?
       We would miss those rare events that we are
        really after:
               e.g. top production:  1 in 1010 collisions
                 Higgs production:  1 in 1012 collisions
        would have to record 50 events/second for
        634 years to get one Higgs event!
       Storage needed for these events:
                3  1011 Gbytes
   Trigger has to decide fast which events
    not to record, without rejecting the
    “goodies”
      Sample cross sections
 p                       t                    p


            q                q
                         t




Process      s(pb)                       events
collision   8 x 1010                   8 trillion
 2 jets     3 x 106                   300 million
 4 jets     125,000                   12,500,000
 6 jets      5,000                      500,000
                                 -1
   W        25,000     x 100 pb        2,500,000
   Z        11,000                     1,100,000
  WW           10                         1000
    tt          5                         500
 Higgs        0.1                          10
Luminosity and cross section
   Luminosity is a measure of the beam
    intensity
    (particles per area per second)
        ( L~1031/cm2/s )

   “integrated luminosity”
    is a measure of the amount of data
    collected (e.g. ~100 pb-1)

    cross section s is measure of effective
    interaction area, proportional to the
    probability that a given process will
        occur.
        1 barn = 10-24 cm2
        1 pb = 10-12 b = 10-36 cm2 = 10- 40 m2

   interaction rate:

dn / dt  L  s                n  s  Ldt
               Trigger Configuration

Detector   L1 Trigger                  L2 Trigger
       7 MHz           10 kHz                             1 kHz

CAL            L1CAL            L2Cal


FPS
                L1PS            L2PS
CPS


                                L2CFT
                                                Global
CFT            L1CFT
                                                 L2


SMT                             L2STT


                L1               L2
Muon
               Muon             Muon


FPD            L1FPD
                                           L2: Combined
                                           objects (e, , j)
                L1: towers, tracks
                   DØ Experiment
   Physicists
       Susan Blessing
       Sharon Hagopian
       Vasken Hagopian
       Stephan L. Linn
       Harrison B. Prosper         Research Interests
       Horst D. Wahl                   Top quarks
       Bill Lee                        Supersymmetry
       Silvia Tentindo-Repond          Leptoquarks
   Graduate Students                   Higgs
       Brian Connolly              Recent Work
       Russell Gilmartin             Measurement of top
       Attila Gonenc                  quark mass
       Craig Group                   Search for
                                       leptoquarks
       Jose Lazoflores
                                      Search for
       Yuri Lebedev
                                       supersymmetric top
       Sinjini Sengupta               quarks
   Undergraduate student:
     Burnham Stokes
                 CMS Experiment
   Physicists
       S. Hagopian
       V. Hagopian
       K. Johnson
       H.B. Prosper
       H.D. Wahl               Research Interests
   Engineers:                    Supersymmetry
     Maurizio Bertoldi           Higgs
     James Thomaston           Recent Work
   Undergraduate student:        R&D of a laser-
                                   based monitoring
     Lucas Naveira
                                   system for the CMS
                                   calorimeter
                                  R&D of devices to
                                   scan large
                                   scintillating tiles.
                                  Coordination of test
                                   beam experiments
                                   at CERN
                 Summary

   Dzero: 2000 to 2005
     Will remain the main focus of our
      research program for the next seven
      years.
     We have a wonderful window of
      opportunity to make major contributions
      to our field.
   CMS:    2005 and beyond
     The LHC will vastly increase our ability
      to probe Nature. We are very confident
      that CMS will have a profound impact on
      our understanding of particle physics.
   Hellaz: 2003 (?) and beyond

				
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