1 / 15

Crystal Detector R&D proposal for Soft Photon Measurement in STAR

Crystal Detector R&D proposal for Soft Photon Measurement in STAR. Presented by Gang Wang (UCLA). University of California at Los Angeles Joint Institute for Nuclear Research Institute of Modern Physics at Lanzhou. Soft photons: 20 - 1000 MeV. Physics motivations :

gaston
Télécharger la présentation

Crystal Detector R&D proposal for Soft Photon Measurement in STAR

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Crystal Detector R&D proposalfor Soft Photon Measurement in STAR Presented by Gang Wang (UCLA) University of CaliforniaatLosAngeles Joint Institute for Nuclear Research Institute of Modern Physics at Lanzhou

  2. Soft photons: 20 -1000 MeV • Physics motivations : • New physics domain exploration • Radiative decays of particles • EM radiation from bulk medium • Experimental opportunities : • TPC +TOF +HFT +Crystal Detector = unique combination, new particle measurement capability • Larger photon cross-section allows smaller acceptance See next page for details…

  3. Physics motivations • Pre-equilibrium and thermal photons • Pre-equilibrium stage of the heavy ion collision and its evolution decidedly unexplored. • Thermal photon radiation from the QGP and HRG phases • Radioactive decays of particles • S0L + g • ccJ/y + g • ~40% J/yfrom feed-down decays • EM radiation from bulk medium • quark jets traversing the QCD color medium • high pT charged hadron – soft photon back-to-back correlation -> properties of the dense partonic matter • high angular momentum of bulk quark matter • dipole radiation • Synchrontron radiationfrompossibleformationoflongitudeinal E/B fields

  4. Experiment: direct photons at WA98 Direct PhotonProduction in 158 A GeV 208Pb+208Pb Collisions WA98, Phys. Rev. Lett. 93 (022301), 2004 Range: 0.5 < pT < 3.5 GeV/c Yield of the direct photons at low pT extracted from the strength of the two-photon correlation. (See efforts by the Yale Group) Low-pT range [0.02, 1.0] GeV/c is not accessible

  5. Experiment: direct photons at PHENIX Range: 1.0< pT < 10.0 GeV/cDirect photon spectra obtainedwiththestatisticalsubtraction method Probingthe QCD equationofstatewiththermalphotonsinnucleus-nucleus collisionsat RHICDavid d’Enterriaand Dimitri Peressounko, nucl-th/0503054 Low-pT range [0.02, 1.0] GeV/c is not accessible

  6. Soft photon measurement pTcoverage : from 20 to 1000 MeV • Can not be measured by PHENIX, ALICE and STAR with present detectors • Predicted yield is large and even with a small crystal patch measurements seem to be possible at STAR in near future • How well (for how much) we can do that ? Needed R&D in FY07 to find out

  7. Crystals Inorganic crystals is the only practical option for STAR, CsI(Tl) from IMP is the one we propose to investigate.

  8. Monte-Carlo simulations Crystal Detector is implemented within STARSIM framework. It is located in place of BEMC module 88 and TOF tray 88. STAR EAST VIEW Super-cube : 9x20 crystals Crystal Patch Crystal calorimeter: Three projective “super-cubes” 9x20 Total 540 crystals inDhxDf = 0.66x6o Crystals: 2.54 cm x 2.54 cm x 25 cm Interaction point Crystal Patch

  9. Crystal Detector: sample MC events Hijing central Au +Au event: clean, two photons photons Hijing central Au +Au event: hadronic background example

  10. Occupancy and Energy Deposition Background sources which contribute to detector occupancy : charged tracks and albedo from BEMC modules. Occupancy data indicates that even in central Au +Au events it is possible to identify soft photons cleanly!

  11. Photon rates for low-pTregion Preliminary photon count rates for 0.02 < pT < 0.20 GeV are calculated using fully reconstructed Hijing events (starsim + BFC). Cluster finder algorithm efficiency is not included yet, charged hadron background removal is considered to be 100% efficient at this moment. Preliminary estimations show that we will need ~1M central events for ~3% error in yield measurements (low-pT region for all centrality bins) Expected energy resolution 5-10%, depends on cluster size: 3x3, 4x4 crystals and photo detector cutoffs. Small acceptance is compensated by large photon yield!

  12. FY07, R&D Goals: MC simulations • Complete understanding of the efficiency and purity of reconstructed soft photons in the Crystal Detector : • Various cluster finder algorithms investigation • Robust procedure for removal of non-photonic backgrounds • Possible hardware veto layer for charged tracks? • Shower shape analysis possibilities and isolation cuts • Extended BEMC albedo studies • Shielding, isolation cuts? • Required dataset for detailed analysis : • 50k fully reconstructed AuAu200 central events (Hijing) with most probable geometry settings (help from S&C group) • Disk space is the most important issue here • Disk space required for studies is ~0.5 Tb • Various performance issues : • Pileup, leakages, optimizations etc…

  13. FY07, R&D Goals: Hardware • Define crystal detector element. • crystal, wrapping, coupling with Photo Detector, Photo-detector, readout • lots of things known from literature – need first hand experience. • Optimize light yield/uniformity. • Investigate possibility of using TPC DAQ1000 • PSA/Altro chips for readout of PD. (Counting on help from Tonko) • Make preliminary design of a mechanical support structure and investigate integration into the STAR detector. (help from STSG) • Understand radiation conditions, required rad. hardness tests and monitoring scheme for crystals. • By the end of FY07 we want to define cost/schedule. Requests: • Acquire crystals from IMP. (in progress) • Acquire PD from Hamamatsu. • Acquire/Borrow radioactive sources • Set up a testing lab at BNL

  14. Summary • Very first and preliminary results look optimistic. • More detailed R&D work is needed in FY07 and we hope to reach a firm decision on feasibility of the soft photon physics with crystals in STAR • We need more collaborators! Thanks to STAR Software team for their help!

  15. Backup slides • Energy resolution: require a lot of explanation • graph 3x3 20-200 MeV band (10% to as low as 3%?) • Shower shape in crystals 3x3 – central fraction, leak from sides put here light yield per MeV, realistic cutoff How crystal patch can be compared with conversion on gas of TPC?

More Related