Accelerator Based Particle Physics Experiments

Transcription

1 Accelerator Based Particle Physics Experiments Su Dong Stanford Student Orientation SLAC session Sep/16/2010 1

2 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? 2

3 Accelerator Based Particle Physics Programs Expt Description Data Period ATLAS pp TeV at LHC BaBar/ superb at SLAC B-factory/ e+e- super B factory at Frascati /?? APEX/HPS Heavy Photon Search at Jlab 2010/2012- SiD Silicon Detector for ILC?? SLD e+e- -> Z e- beam

4 LHC 4

5 Physics Road map and Detector Evolution Stage 0: 2012 Stage 1: Stage 2:

6 Physics Opportunities Higgs particle SuperSymmetry Large extra-dimensions The unexpected 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 E t Search for long lived new particles Lepton jets Heavy fermions->same sign dileptons Boosted W Close collaboration with SLAC theory group 6

7 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 7

8 Contact Info Prof. Su Dong Dr. Charlie Young Prof. Ariel Schwartzman (resident at CERN) Dr. Andy Haas Detailed info on for students: 8

9 PEP-II & Frascati 9

10 BaBar Physics CP violation in B 0 decays 10

11 BaBar Analysis Opportunities Data taking ended Apr/ M BB events 630M cc events 460M ττ events Largest sample of Upsilon resonance data 2-photon, ISR Analysis topics: ISR->hadronic final states B/D decay Dalitz analysis Radiative B decays f Ds Charmonium like resonances Prof. David Leith leith@slac.stanford.edu Dr. Blair Ratcliff blair@slac.stanford.edu 11

12 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: 9/16/

13 Focusing DIRC prototype photon detectors Nucl.Inst.&Meth., A 553 (2005) 96 1) Burle MCP-PMT (64 pixels, 6x6mm pad, σ TTS ~50-70ps) σ narrow 70ps time (ns) 2) Hamamatsu H-8500 MaPMT (64 pixels, 6x6mm pad, σ TTS ~140ps) σ narrow 140ps Timing resolutions were obtained using a fast laser diode in bench tests with single photons on pad center. time (ns) 3) Hamamatsu H-9500 Flat Panel MaPMT (256 pixels, 3x12mm pad, σ TTS ~220ps) σ narrow 220ps time (ns) 9/16/

14 Cherenkov light: tagging color by time Chromatic growth rate: σ ~ 40ps/m Analytical calculation: Cherenkov angle production controlled by n phase : cos θ c = 1/(n phase β), n phase (red) < n phase (blue) => θ c < θ c Propagation of photons is controlled by n group ( n phase ) : v group = c 0 /n group = c 0 /[n phase - λ phase λ Geant 4 - without and with pixilization: Data from the prototype: (blue) dtop/lpath [ns/m] = TOP/Lpath(λ) - TOP/Lpath (410nm) v group (red) > v group dtop/lpath [ns/m] dtop/lpath [ns/m] 9/16/

15 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 R&D with a innovative new detector. 9/16/

16 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: s+in+heavy+photon+search John Jaros

17 What is a Heavy Photon? A heavy photon (A ) is a new, ~100 MeV spin one, forcecarrying particle that couples to an analogue of electric charge. Because it will mix with our photon, it couples to electrons, albeit weakly: g = ε e 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 detectable distances before decaying, providing a unique signature.

18 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

19 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 Si Tracker APV25 Readout 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 john@slac.stanford.edu