Accelerator Based Particle Physics Experiments

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Accelerator Based Particle Physics Experiments

• Su Dong
• Stanford Student Orientation
• SLAC session
• Sep/16/2010

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The Fundamental Questions

• Are there undiscovered principles of nature new
  symmetries, new physical laws ?
• How can we solve the mystery of dark energy ?
• Are there extra dimensions of space ?
• Do all forces become one ?
• Why are there so many kinds of particles ?
• What is dark matter ?
• How can we make it in the laboratory ?
• What are neutrinos telling us ?
• How did the universe come to be ?
• What happened to antimatter ?

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Accelerator Based Particle Physics Programs

Expt Description Data Period
ATLAS pp collision _at_7-14 TeV at LHC 2010-
BaBar/ superB ee- _at_10GeV at SLAC B-factory/ ee- super B factory at Frascati 1999-2008/ ??
APEX/HPS Heavy Photon Search at Jlab 2010/2012-
SiD Silicon Detector for ILC ??
SLD ee- -gt Z0 _at_91GeV,polarized e- beam 1992-1998
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ATLAS _at_ LHC
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Physics Road map and Detector Evolution
Stage 2 2020
Stage 1 2015-6
Stage 0 2012
2015
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Physics Opportunities

• SLAC physics strategy
• Initial emphasis on physics signature tools
  (b-tag,jet/missingEt) and trigger. Use Standard
  Model measurements with early data to validate
  these tools to prepare for searches of new
  physics beyond Standard Model.
• Current SLAC physics analyses
• New physics search and top cross section
  measurement with b-tag and missing Et
• Search for long lived new particles
• Lepton jets
• Heavy fermions-gtsame sign dileptons
• Boosted W
• Close collaboration with SLAC theory group

• Higgs particle
• SuperSymmetry
• Large extra-dimensions
• The unexpected

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SLAC Involvement in ATLAS
2 Faculty 1 Panofsky fellow 17 Staff
physicists professionals 7 Postdocs 6
Grad students Tier2 computing center staff

• Experimental Involvement
• Pixel vertex detector and tracking
• High Level Trigger and DAQ
• Simulation
• Tier-2 computing center
• ATLAS Detector Upgrades
• Opportunities to develop wide variety of
  experimental skills

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Contact Info
Dr. Charlie Young young_at_slac.stanford.edu
Prof. Su Dong
sudong_at_slac.stanford.edu
Prof. Ariel Schwartzman sch_at_slac.stanford.edu (re
sident at CERN)
Dr. Andy Haas ahaas_at_slac.stanford.edu
Detailed info on ATLAS_at_SLAC for students
http//www.slac.stanford.edu/exp/atlas/students/
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BaBar _at_ PEP-II superB _at_ Frascati
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BaBar Physics
CP violation in B0 decays
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BaBar Analysis Opportunities

• Data taking ended Apr/08.
• 465M BB events
• 630M cc events
• 460M tt events
• Largest sample of Upsilon resonance data
• 2-photon, ISR

• Analysis topics
• ISR-gthadronic final states
• B/D decay Dalitz analysis
• Radiative B decays
• fDs
• Charmonium like resonances

Prof. David Leith leith_at_slac.stanford.edu
Dr. Blair Ratcliff blair_at_slac.stanford.edu
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Focusing DIRC prototype now in Research Yard

• Radiator
• 1.7 cm thick, 3.5 cm wide, 3.7 m long fused
  silica bar (the same used in the BaBar DIRC).
• Optical expansion region
• filled with mineral oil to match the fused silica
  refraction index (KamLand oil).
• include optical fiber for the electronics
  calibration.
• Focusing optics
• spherical mirror with 49cm focal length focuses
  photons onto a detector plane.
• Now being tested with new electronics

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Focusing DIRC prototype photon detectorsNucl.Inst
.Meth., A 553 (2005) 96
1) Burle 85011-501 MCP-PMT (64 pixels, 6x6mm
pad, sTTS 50-70ps)

• Timing resolutions were obtained using a fast
  laser diode in bench tests with single photons on
  pad center.

2) Hamamatsu H-8500 MaPMT (64 pixels, 6x6mm pad,
sTTS 140ps)
3) Hamamatsu H-9500 Flat Panel MaPMT (256 pixels,
3x12mm pad, sTTS 220ps)
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Cherenkov light tagging color by time
Chromatic growth rate s 40ps/m
Analytical calculation
dTOP/Lpath ns/m TOP/Lpath(l) - TOP/Lpath
(410nm)

• Cherenkov angle production controlled by nphase
  
• cos ?c 1/(nphaseb), nphase(red) lt nphase(blue)
  gt ?c lt ?c
• Propagation of photons is controlled by ngroup (?
  nphase)
• vgroup c0 /ngroup c0
  /nphase - ????phase????
• vgroup(red) gt vgroup
  (blue)

Data from the prototype
Geant 4 - without and with pixilization
dTOP/Lpath ns/m
dTOP/Lpath ns/m
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Future

• We are building a new full size prototype for
  Super B with new fused silica focusing elements
• Will be starting tests in Cosmic Ray Telescope
  in the SLAC Research Yard this year
• Excellent opportunity for hands-on RD with a
  innovative new detector.

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HPS is a new, small experiment which offers the
thesis student exposure to all aspects of
experimental particle physics, from experiment
design and optimization, to hardware
construction, installation and commissioning, and
data analysis.Rotation Projects https//conflue
nce.slac.stanford.edu/display/hpsg/RotationProjec
tsinHeavyPhotonSearch
John Jaros
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What is a Heavy Photon?

• A heavy photon (A) is a new, 100 MeV spin one,
  force-carrying particle that couples to an
  analogue of electric charge. Because it will mix
  with our photon, it couples to electrons,
  albeit weakly
• Heavy photons can be produced by electron
  bremstrahlung off heavy targets and they decay to
  ee
• A heavy photon appears as an ee- resonance on a
  large background of QED tridents.
• Heavy photons can travel detectabledistances
  before decaying, providing a unique signature.

g ? e
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Why Consider Heavy Photons?

• Are there are additional U(1)s in Nature? If so,
  theyll show up by mixing with our photon,
  inducing weak couplings to electric charge.
• Heavy Photons could mediate Dark Matter
  annihilations. Their decays may explain excess
  high energy electrons and positrons in the cosmic
  rays their interactions may account for the DAMA
  dark matter detection.

Pamela Positron Excess
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SLAC Activities on HPS and APEX

• SLAC Heavy Photon Group is engaged
  in two projects
• HPS (Heavy Photon Search) has just submitted a
  proposal to JLab
• Review next week at JLab workshop approval this
  Fall?
• Hope to engineer, construct, test, install by
  Spring 2012
• Building Si tracker/vertexer, targets, and SVT
  data acquisition system GOOD PROJECTS
  FOR ROTATION STUDENTS
• APEX (A Prime Experiment) utilizes two large
  existing spectrometers in Jlabs Hall A to search
  for heavy photons
• SLAC built targets, helped with test run, and is
  developing analysis
• SLAC will continue helping run and analyze APEX
• Contact John Jaros
  john_at_slac.stanford.edu

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