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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 2-9 2010

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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

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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:0804.4330) RHIC (200 GeV) S.Wicks et al (Nucl.Phys.A784 (2007) R AA (charm)/R AA (beauty) pQCD ADS/CFT Winter Workshop 2010, Jamaica

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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)

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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 500-800. Sets scale for PID performance. Winter Workshop 2010, Jamaica

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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

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M.Heinz (Yale) 7 Hadron Rejection Power (HRP) Results from CERN test-beam for energies 40-80 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 400-1000. Winter Workshop 2010, Jamaica From published NIM paper arXiv: 0912.2005 Simulation

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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

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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

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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: 0712.2422 Winter Workshop 2010, Jamaica

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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

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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

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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

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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 12-150 GeV/c) Winter Workshop 2010, Jamaica PYTHIA jets (p T hard 12-150 GeV/c) Signal EfficiencyFake rejection

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

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M.Heinz (Yale) 16 Conclusions & Outlook Conclusions EMCAL PID (using E/p method) works well and we expect a hadron rejection power of 400-1000 (65% efficiency) for 10 GeV/c< p T

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Backup

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