Heavy flavor measurements with high-p T electrons in the ALICE EMCal Mark Heinz (for the ALICE Collaboration) Yale University 26 th Winter Workshop on Nuclear Dynamics Ocho Rios, Jamaica, Jan

M.Heinz (Yale) 2 Physics Motivation (p+p) Beauty physics in p+p (examples): –Transverse momentum spectrum, X-section, (normalization for “Quarkonia” studies) –Jet-Shapes –Fragmentation function X-section vs NLO CDF (PRD78,2008)  (r/R) Jet-Shape Winter Workshop 2010, Jamaica

M.Heinz (Yale) 3 Physics Motivation (Heavy Ion) Investigate energy loss of quarks vs. gluons Investigate differences between the predictions of pQCD vs ADS/CFT Horowitz, Gyulassy (arXiv: ) RHIC (200 GeV) S.Wicks et al (Nucl.Phys.A784 (2007) R AA (charm)/R AA (beauty) pQCD ADS/CFT Winter Workshop 2010, Jamaica

M.Heinz (Yale) 4 Electron Identification in Alice  Barrel (TPC/TRD/TOF)  Superior electron/hadron discrimination up to p~10 GeV/c  EMCal  Very good electron/hadron discrimination for p > 10 GeV/c. PID parameters tuned.  4 Super-modules installed in ALICE  5th SM at calibration stage at Yale University  Energy calibration of detector with  0 currently underway  Part of routine data-taking  Sufficient coverage for day 1 physics Winter Workshop 2010, Jamaica Run 2010 configuration (Pb+Pb low luminosity)

M.Heinz (Yale) 5 Electron Rates (PYTHIA) PYTHIA Rates are scaled to 1 month of Pb+Pb running (0.5mb -1 s -1, 10 6 sec, A 2 ) Significant beauty-electron yield out to p T ~50 GeV/c Dominant background are W-electrons above 20 GeV/c Hadron/Electron ratio is Sets scale for PID performance. Winter Workshop 2010, Jamaica

M.Heinz (Yale) 6 EMCAL PID: E/p For electron identification we use the ratio of E cluster /p track. Track-Cluster matching efficiency ~65% The electron peak can be cleanly separated from pions. Material interaction in front of the EMCAL does deteriorate the performance. Winter Workshop 2010, Jamaica Simulation

M.Heinz (Yale) 7 Hadron Rejection Power (HRP) Results from CERN test-beam for energies GeV. These compare well to ideal simulation (ie. no additional detector material in front of EMCAL) Results from simulation for a set of optimized cuts for electron identification and full ALICE detector simulation. For ~65% electron efficiency we obtain a HRP between Winter Workshop 2010, Jamaica From published NIM paper arXiv: Simulation

M.Heinz (Yale) 8 Electron Spectra Reconstructed conversion electron vertices are found by the V0-finder and tagged using an invariant mass cut (M inv <100 MeV). These are then subtracted from the inclusive electrons. After EMCAL PID non-photonic electron candidates dominate misidentified hadrons by at least factor 10. Dominant background to b-electrons above 20 GeV/c from W- electrons. This can be further reduced by secondary vertex strategies. Winter Workshop 2010, Jamaica PYTHIA

Corrected Spectra Efficiency corrected rates of non-photonic electron candidates Systematical errors indicate the variation of EMCAL PID criteria M.Heinz (Yale) 9 Winter Workshop 2010, Jamaica PYTHIA Simulation

M.Heinz (Yale) 10 B-Tagging: Displaced Vertex Method The method previously used by CDF to identify secondary vertices from semi- leptonic decays. Further development and implementation in ALICE. Breakdown of method: –Find a high-pt electron trigger particle in EMCAL –Pair with all charged hadrons within a cone of radius dR. –Reconstruct “approximate” (average between B-D decay) secondary vertex using an identified electron and all associated hadrons –apply more cuts to reduce backgrounds from other leptonic decays. –Plot L xy distribution and obtain B- contribution from positive/negative imbalance D0D0 B- e- K  /e P e+K r PrimVtx SecVtx L xy = r.p e+k / |p e+k | L xy CDF Phys.Rev.D66 (2002)) M.Heinz, arXiv: Winter Workshop 2010, Jamaica

M.Heinz (Yale) 11 Method Cuts Tracks –Track Impact Parameter < 0.5 cm (electron) –Silicon Hits: ITS>=4 –P T > 1.0 GeV/c (associated hadrons) Secondary Vertex –pairDCA < 0.02 cm –R= √     (electron-hadron) < 1.0 rad –Vertex length < 1.0 cm –SignDCA L xy > 0.1 –Invariant Mass (e+k) > 1.5 Winter Workshop 2010, Jamaica

M.Heinz (Yale) 12 Sign-Dca L xy The method relies on the fact that the B-meson creates a displaced vertex with c  ~500  m. Winter Workshop 2010, Jamaica

M.Heinz (Yale) 13 Electron tag efficiency Tagging algorithm can be tuned by requiring a given number of heavy flavor vertices which pass our cuts Winter Workshop 2010, Jamaica

M.Heinz (Yale) 14 B-Jet Tagging performance in p+p FASTJET Jet-Finding Algorithm: k T, R= 0.4 (anti-k T comparable) Standard definitions: –Efficiency = tagged B-jets/MC-B-jets –Fake Rejection = Non B-Jet efficiency Algorithm currently tuned for maximum fake rejection. Studies ongoing to map out full cut-space Results comparable to CMS Soft Lepton Tag (Note 2005/058) PYTHIA jets (p T hard GeV/c) Winter Workshop 2010, Jamaica PYTHIA jets (p T hard GeV/c) Signal EfficiencyFake rejection

Expected tagged Jet yield M.Heinz (Yale) 15 Winter Workshop 2010, Jamaica

M.Heinz (Yale) 16 Conclusions & Outlook Conclusions EMCAL PID (using E/p method) works well and we expect a hadron rejection power of (65% efficiency) for 10 GeV/c< p T <80 GeV/c. Hadron/Electron ratios from MC in this range are ~500. Reconstructed electrons after subtraction of the photonic component and EMCAL PID dominate the background of mis-identified hadrons by at least a factor 10. Preliminary studies of B-jet tagging algorithms in simulated p+p events have been performed. First results for efficiency and fake rejection using the displaced vertex method have been calculated and are comparable to similar methods used in other experiments. Tagged Jet-yields should be sufficient for measurements of B-jets to p T ~50-60 GeV/c. Outlook More optimization of B-tagging algorithms First look at real data … Winter Workshop 2010, Jamaica

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18 CMS Electron Tag performance  c  uds  g - M.Heinz (Yale)Winter Workshop 2010, Jamaica