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Reconstruction Charm and Bottom with the ALICE EMCAL Mark Heinz for the ALICE collaboration Yale University Winter Workshop of Nuclear Dynamics Big Sky,

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Presentation on theme: "Reconstruction Charm and Bottom with the ALICE EMCAL Mark Heinz for the ALICE collaboration Yale University Winter Workshop of Nuclear Dynamics Big Sky,"— Presentation transcript:

1 Reconstruction Charm and Bottom with the ALICE EMCAL Mark Heinz for the ALICE collaboration Yale University Winter Workshop of Nuclear Dynamics Big Sky, Montana, Feb 2007

2 Workshop, Feb Outline Physics Motivation Method for reconstructing Bottom via displaced vertices ALICE Electromagnetic Calorimeter EMCAL simulation status Conclusion

3 Workshop, Feb Physics Motivation Current theoretical estimates for bottom and charm production still have large uncertainties. NLO pQCD, pp, s = 14 TeV CERN/LHCC , hep-ph/ MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

4 Workshop, Feb Physics Motivation Heavy ion collisions: Interactions of heavy quarks with the medium RHIC has recently shown the that the suppression of non- photonic electrons is not consistent with current energy loss predictions Using the current best estimates for medium density (q-hat) the suppression pattern is consistent with charm quarks only up to 8 GeV/c in p T Similar uncertainties are present for LHC energies non phot. el. STAR, submitted to PRL (nucl-ex/ )

5 Workshop, Feb Charm and Bottom via semi-leptonic decays Semileptonic Channels: c e + + anything (B.R.: 9.6%) D 0 e + + anything (B.R.: 6.87%) D e + anything (B.R.: 17.2%) b e + + anything(B.R.: 10.9%) B e + anything (B.R.: 10.2%) single non-photonic electron continuum Photonic Single Electron Background: conversions ( 0 ) 0, Dalitz decays,, … decays (negligible) Ke3 decays (neglible)

6 Workshop, Feb Displaced Vertex Method Search for semi-leptonic B-decay B e + D 0 e + K /e Idea of Displaced vertex finding using muons was first tested at CDF Create pairs of leptons and charged tracks which match the criteria for a secondary vertex: p T > 2 GeV/c, R= D0D0 B- e- K /e P e+K r PrimVtx SecVtx Reminder: B c : ~500 m D c : ~100 m Signed DCA: L xy = r.p e+k / |p e+k | L xy CDF Phys.Rev.D66 (2002))

7 Workshop, Feb Displaced Vertex Simulations (signal) 1 st Step: pure signal efficiency PYTHIA: 14 TeV, p+p, 40k events, pt(hard)>2.75 Yields 6000 electrons within detector acceptance from beauty Reconstruction efficiency per selected electron trigger ~70% Signal L xy (cm) Efficiency of method improves significantly with #ITS hits

8 Workshop, Feb Dominant backgrounds are semi-leptonic charm decays Simulation: PYTHIA, 14 TeV p+p, c-cbar, pt(hard)>2.1 GeV Effective way of eliminating is by cut on invariant mass Displaced Vertex (charm backgrounds) Charm PYTHIA events

9 Workshop, Feb Displaced vertex (backgrounds) 80k Minbias PYTHIA events (MSEL1) Combinatoric, pi0 and photon backgrounds can be investigated Background is consistent with zero, but more simulation statistics are needed to obtain an exact estimate of significance Minbias PYTHIA, 14 TeV

10 Workshop, Feb Track impact parameter resolution Primary vertex finding proceeds in 2 passes Select primary tracks on the basis of their d 0 Cut |d 0 | < n d0 (p t ) d0 (p t ) = vtx track (p t ) track vertex x y parametrized resolution

11 Workshop, Feb Secondary vertex resolution (simulation) Determine position resolution for semi- leptonic heavy flavor vertices from PYTHIA Position resolution in x,y,z is ~180m, no strong dependency on coordinate reconstruced- MC (cm) K /e SecVtx

12 Workshop, Feb Secondary vertex resolution (simulation) Study of vertex resolution as a function of hits in the inner tracker ITS-hits, maximum of 6 hits.

13 Workshop, Feb ALICE Set-up TRD ITS TPC Size: 16 x 26 meters Weight: 10,000 tons

14 Workshop, Feb ALICE Electromagnetic Calorimeter Coverage: | |<0.7, =110 o Lead-scintillator sampling calorimeter Shashlik fiber geometry Avalanche photodiode readout

15 Workshop, Feb ALICE EMCAL (2) 12 supermodules 24 strips in η 12 (or 6) modules in φ elementary sensors (towers) 77 alternating layers of 1.44 mm Pb (1% Sb) 1.76 mm polystirene scintillator x = 0.014x0.014 Supermodule Module (2x2 towers)

16 Workshop, Feb EMCAL energy resolution Energy resolution has been measured and is within specifications ~12%/E +2% Production Module SpecPrototype Module Spec

17 Workshop, Feb EMCAL Project milestones 18 institutions worldwide of which 13 are from ALICE-USA collaboration Assembly of supermodules will be shared between Yale (US) and Grenoble (F) US-portion of project dependant on funding from DOE: CD-2 (critical decision) this summer. Assembly and testing of supermodules (SM) at Yale to start in 2008 Installation of first SM in ~2009 (low luminosity PbPb)

18 Workshop, Feb EMCAL software development Cluster shape analysis for PID Electron/Hadron discrimination Track-Cluster Matching Electron trigger simulations High-Pt simulations (jet-finder) Institutes involved in HF simulations: Yale, LBL, LLNL, WSU, Nantes (Subatech), Strassbourg, Catania

19 Workshop, Feb EMCAL PID Cluster in EMCAL ° hadrons Study by Guenole Bourdaud e discrimination p/E distribution discrimination Cluster shape analysis Effective mass

20 Workshop, Feb Hadron/ 0 discrimination Granularity study of EMCAL For a 30 GeV photon the 0 suppression factor improve from 10 to 100 when increasing the granularity from 2x2 to 3x3 Study by A.Pavlinov (WSU) Granularity 2x2Granularity 3x3

21 Workshop, Feb TPC track to EMCAL cluster matching Code is now in Alice CVS Good matching effiency for low multiplicity Still some parameter tuning needed for Hijing simulations Study by A.Pulvirenti (Catania) Mult = 10 dN/dη = 4000 Cluster Matching Prob for electrons % %

22 Workshop, Feb Conclusion Displaced vertex method will be promising in measuring direct B-meson contribution to non- photonic electrons The method combines the EMCAL PID and triggering capabilities The ALICE EMCAL project is a collaboration between ALICE USA and European institutions The simulations for the EMCAL are on track, however more detailed physics simulations are required for the DOE CD-2 decision this summer


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