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Accelerator Based Particle Physics Experiments . Su Dong Stanford Student Orientation SLAC session Sep/16/2010. The Fundamental Questions. Are there undiscovered principles of nature: new symmetries, new physical laws ? How can we solve the mystery of dark energy ?

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accelerator based particle physics experiments
Accelerator Based Particle Physics Experiments

Su Dong

Stanford Student Orientation

SLAC session


the fundamental questions
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 ?
physics road map and detector evolution



Physics Road map and Detector Evolution

Stage 2: 2020

Stage 1: 2015-6

Stage 0: 2012


physics opportunities
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->same sign dileptons
  • Boosted W
  • Close collaboration with SLAC theory group
  • Higgs particle
  • SuperSymmetry
  • Large extra-dimensions
  • The unexpected…
slac involvement in atlas
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
contact info
Contact Info

Dr. Charlie Young

Prof. Su Dong

Prof. Ariel Schwartzman

(resident at CERN)

Dr. Andy Haas

Detailed info on ATLAS@SLAC for students:


BaBar @ PEP-II

& superB @ Frascati

babar physics
BaBar Physics

CP violation in B0 decays

babar analysis opportunities
BaBar Analysis Opportunities
  • Analysis topics:
  • ISR->hadronic final states
  • B/D decay Dalitz analysis
  • Radiative B decays
  • fDs
  • Charmonium like resonances
  • Data taking ended Apr/08.
  • 465M BB events
  • 630M cc events
  • 460M tt events
  • Largest sample of Upsilon resonance data
  • 2-photon, ISR

Prof. David Leith

Dr. Blair Ratcliff

focusing dirc prototype now in research yard
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:

snarrow ≈70ps

time (ns)

snarrow ≈220ps

time (ns)

snarrow ≈140ps

time (ns)

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)

cherenkov light tagging color by time
Cherenkov light: tagging color by time

Chromatic growth rate:

s ~ 40ps/m

Cherenkov angle production controlled by nphase:

cos c = 1/(nphaseb),nphase(red) < nphase(blue) => c< c

Propagation of photons is controlled by ngroup (≠ nphase):

vgroup =c0 /ngroup = c0 /[nphase - phase

vgroup(red) > vgroup (blue)

Analytical calculation:

dTOP/Lpath [ns/m] = TOP/Lpath(l) - TOP/Lpath (410nm)

Data from the prototype:

Geant 4 - without and with pixilization:

dTOP/Lpath [ns/m]

dTOP/Lpath [ns/m]

  • 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 R&D with a innovative new detector.

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:

John Jaros

what is a heavy photon
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 e+e –
  • A heavy photon appears as an e+e- resonance on a large background of QED tridents.
  • Heavy photons can travel detectabledistances before decaying, providing a unique signature.

g’ =  e

why consider heavy photons
Why Consider Heavy Photons?
  • Are there are additional U(1)’s in Nature? If so, they’ll 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

slac activities on hps and apex
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 systemGOOD PROJECTS FOR ROTATION STUDENTS

APEX (A Prime Experiment) utilizes two large existing spectrometers in Jlab’s 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

Si Tracker

APV25 Readout