1 / 28

Photon physics in ALICE

Photon physics in ALICE. Y.Kharlov D.Peressounko IHEP RRC “Kurchatov Institute” for the ALICE collaboration. and. Photon physics. Neutral meson spectra, R AA , v 2 … Chemical composition: p 0 , h , w.

henry-hughes
Download Presentation

Photon physics in ALICE

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. Photon physics in ALICE Y.Kharlov D.Peressounko IHEP RRC “Kurchatov Institute” for the ALICE collaboration and

  2. Photon physics Neutral meson spectra, RAA, v2… Chemical composition: p0,h, w Direct photon – jet correlations g thermal g isolated p,h,w,.. g Direct photon spectra, RAA, v2… Inclusive, Isolated, Thermal ginclusive Photon physics with ALICE

  3. ALICE setup in 2009: section at h=0 EMCAL: |h|<0.7 Df: 110o 2/5 installed PHOS: • high-granularity photon • spectrometer (20 X0) • acceptance: =100, ||<0.12 • 18k PbWO4 crystals 2.22.218. cm3 • 5 modules 6456 crystals each • energy range: 0.1-100 GeV • EMCAL • large aperture Pb-Sc • electromagnetic calorimeter (20 X0) • acceptance: =107, ||<0.7 • 13k towers 66 cm2. • 11 supermodules 2448 towers each • energy range: 0.1-250 GeV • CERN-ALICE-TDR-014 PHOS: |h|<0.125 Df: 100o 3/5 installed 3 Photon physics with ALICE

  4. Photon detectors resolutions ITS+TPC+TRD EMCAL PHOS sE/E (%) 2 sx(mm) ~1 Rip (cm) 428 460 < 160 5.5 MeV 16 MeV 3.3 MeV 0.8<pt<2 GeV sp (MeV) pt=1-2 GeV 4 Photon physics with ALICE

  5. p0 measurement merged clusters not spherical  shower shape analysis 10 - 30 GeV/c in EMCal 50 - 100 GeV/c in PHOS • well separated clusters • invariant mass analysis • < 10 GeV/c in EMCal • < 30-50 GeV/c in PHOS EMCAL g identified as g PHOS g identified as p0 p+p p0 as p0 p0 as g pT (GeV/c) Photon physics with ALICE

  6. p0 and h measurement PHOS, h PHOS PHOS,p0 mgg (GeV) Conversion Conversion,p0 Conversion See poster K.Aamodt et al., for p0/hviaconvertedphotons Photon physics with ALICE

  7. 0 in central Pb-Pb collisions at 5.5 ATeV Only event mixing technique reveals 0 peak at low pT Photon physics with ALICE

  8. Acceptance for p0, h, w measurement Acceptance is normalized per |y|<0.5, =2 8 Photon physics with ALICE

  9. ALICE trigger for photon physics • ALICE minimum bias trigger: • Accepts almost any pp collisions based on signals in inner and forward ALICE detectors • Trigger busy time is determined by the slowest detector in a trigger partition. • Although collision rate in pp is high (3.5 kHz), event rate can be as slow as 200 Hz which corresponds to effective luminosity L=51027 cm-2s-1. • PHOS trigger: • Can select events with high energy deposited in 22 or 44 crystals • If the trigger partition with PHOS includes fast detectors, event rate is defined only by the luminosity • The higher the trigger threshold, the lower event rate is, and the slower detectors can be included into the trigger partition • EMCAL • Same as PHOS, but with different thresholds • TRD • Trigger one+e-pairwithhighptandsmallopeningangle. • Under investigation Photon physics with ALICE

  10. PHOS L0 trigger rate in pp @ 10 TeV L0 definition: 2x2 (4x4) cells energy sum > threshold somewhere in PHOS Rate is calculated under assumption of 3.5 kHz collision rate Setting PHOS L0thresholdtoamoderatevalue (~500 MeV) resultsinlowenoughdatatakingratewithminimaleffectofatriggerbusytime. Photon physics with ALICE

  11. 0, , h and wcross sections in pp ppX pp0X NLO pQCD + CTEQ5M + KPP. Bands indicate possible uncertainties in QCD scale [P. Aurenche, et al., Eur. Phys. J. C 13,347 (2000)] ppX ppX LO pQCD: Pythia 6 Photon physics with ALICE

  12. Expected yields in first ALICE run Photon physics with ALICE

  13. Accesible range in Pb+Pbcolisions Pb+Pbgdir+X Pb+Pbp0+X RAA=1 RAA=0.2 LPbPb=5·1026 [cm-2s-1] T = 1·106 [s] ∫L = 0.5 [nb-1] Binary scaled p+pcrosssection@ 5.5 TeV (INCNLO) Nbinarycalculatedusing [F.Arleoetal., hep-ph/0311131] centralityclass 0-10% Photon physics with ALICE

  14. Isolated direct photons Y. Mao et al., Eur.Phys.J.C57:613-619,2008 G. Conesa et al., ALICE-INT-2005-014,NIM A 580 (2007) 1446 g isolated 5 PHOS modules 2 PHOS modules gfragmented IC: R =0.3, S(pT)=2 GeV/c IC: R =0.2, pT>2 GeV/c See posters Y.Mao and R. Ichou Photon physics with ALICE

  15. pp = PYTHIA PbPb =PYTHIA (signal) +HIJING (UE) Full reconstruction in ALICE Isolated Spectra in EMCAL pp @ √14 TeV PbPb @ √5.5 TeV PbPb @ √5.5 TeV, qhat = 50 g-jet (signal); jet-jet (p0 –hadron background)

  16. g-hadron correlations PYTHIA pp collisions √s=14 TeV All associated charged hadrons with pT > 2 GeV/c G. Conesa, ProceedingsofScience, PoS (HIGH-pTLHC) 003 Photon physics with ALICE

  17. g-h correlation in pp and AA pTt pTa pout • XE= -pTh · pT / |pT|2 kT xEz EPJC (2008) 57: Y. Mao PYQUEN DAA = CFAA/CFpp background soft hadrons background photons XE See poster Y.Mao Photon physics with ALICE

  18. Conclusions • ALICE is well equipped by photon detectors • PHOS in 2008-2011 • EMCAL in 2009-2011 • ITS, TPC installed; TRD in 2008-2010 • ALICE will measure direct photon, neutral meson spectra, -hadron and -jet correlations, jet fragmentation functions • The first 1-month LHC run with pp@10 TeV results in 0 spectrum up to pT<25 GeV/c in PHOS (40 with PHOS L0 trigger) and similar pt range in EMCAL and conversion in central tracking system. • Isolated direct photons can be measured in the range pt>10 -15 GeV/c • Gamma-hadron correlations can be constructed for isolated photons Photon physics with ALICE

  19. Thanks • Special thanks to Gustavo Conesa and Ana Marin • ALICE collaboration Photon physics with ALICE

  20. Backup slides

  21. Impact parameter < 50 mm for pt > 1.5 GeV Momentum resolution ~ 5% @ 100 GeV Tracking • robust, redundant tracking from 100 MeV to 100 GeV • modest soleniodal field (0.5 T) => easy pattern recognition • long lever arm => good momentum resolution • small material budget: ~ 10% X0 vertex -> end of TPC (r = 2.6 m) • very little dependence on dNch/dy up to 8000 (important for systematics !)

  22. PID from ~ 100 MeV to above 50 GeV Alice uses ~ all known techniques! Particle Identification • stable hadrons (p, K, p): • dE/dx in silicon (ITS) and gas (TPC) + Time-of-Flight (TOF) + Cerenkov (HMPID) • leptons (e, m) • transition radiation (TRD), muon spectrometer • photons, h,p0 • e.m calorimeters (PHOS, EMCAL) • decay topology (K0, K+, K-, L, D+, ..), secondary vertices (c,b)

  23. ALICE setup in 2009: section at h=0 ITS: |h|<0.9 Df: 2p HMPID: |h|<0.6 Df=57.6o 7/7 installed EMCAL: |h|<0.7 Df: 110o 2/5 installed TRD: |h|<0.9 f: 2p* 6-7/18 installed TPC: |h|<0.9 Df: 2p TOF: |h|<0.9 f: 2p* 18/18 installed *Holes are made in front of 3 PHOS modules PHOS: |h|<0.125 Df: 100o 3/5 installed

  24. PHOS status 1 module was installed and commissioned in ALICE in 2008 2 more modules will be installed in 2009 Completed (all 5 modules) in 2010-2011 Photon physics with ALICE

  25. EMCAL status TDR passed. 2 supermodules were installed in March 2009. 3(4) supermodules to be installed in 2009. Completed (11 supermodules) in 2011. Photon physics with ALICE

  26. LHC run scenarios • Nominal LHC scenario for ALICE: • pp collision energy: 14 TeV • luminosity: 31030 cm-2s-1 • First LHC run scenario: • pp collisions at 10 TeV (?) • luminosity: 51028 cm-2s-1 (?) • Data taking time: from days to months • If PHOS is triggered by the ALICE minimum bias trigger, then event rate is limited by 200 Hz: Leff = 51027 cm-2s-1 • If PHOS is triggered by its standalone L0 trigger on high pT, event rate is defined by pT spectrum only Photon physics with ALICE

  27. Raw 0spectrum in pp@10 TeV: N(pT) and S/B ratio Photon physics with ALICE

  28. Photon detectors of ALICE EMCAL EMCAL PMD PHOS PHOS Photon physics with ALICE

More Related