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

Outline Physics Motivation Method for reconstructing Bottom via displaced vertices ALICE Electromagnetic Calorimeter EMCAL simulation status Conclusion mark.heinz@yale.edu Winter Workshop, Feb 2007

Physics Motivation Current theoretical estimates for bottom and charm production still have large uncertainties. NLO pQCD, pp, s = 14 TeV MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295. CERN/LHCC 2005-014, hep-ph/0601164 mark.heinz@yale.edu Winter Workshop, Feb 2007

Physics Motivation Heavy ion collisions: STAR, submitted to PRL (nucl-ex/0607012) non phot. el. 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 pT Similar uncertainties are present for LHC energies mark.heinz@yale.edu Winter Workshop, Feb 2007

Charm and Bottom via semi-leptonic decays Semileptonic Channels: c  e+ + anything (B.R.: 9.6%) D0  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: g conversions (p0  gg) p0, h, h’ Dalitz decays r, f, … decays (negligible) Ke3 decays (neglible) mark.heinz@yale.edu Winter Workshop, Feb 2007

Displaced Vertex Method Search for semi-leptonic B-decay B  e + D0  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: pT> 2 GeV/c, R=2+2 K /e Pe+K Signed DCA: Lxy= r .pe+k / |pe+k| Lxy CDF Phys.Rev.D66 (2002)) e- D0 SecVtx r B- Reminder: B ct: ~500 mm D ct: ~100 mm PrimVtx mark.heinz@yale.edu Winter Workshop, Feb 2007

Displaced Vertex Simulations (signal) 1st 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 Efficiency of method improves significantly with #ITS hits Lxy (cm) mark.heinz@yale.edu Winter Workshop, Feb 2007

Displaced Vertex (charm backgrounds) 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 Charm PYTHIA events mark.heinz@yale.edu Winter Workshop, Feb 2007

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 Minbias PYTHIA, 14 TeV mark.heinz@yale.edu Winter Workshop, Feb 2007

Track impact parameter resolution Primary vertex finding proceeds in 2 passes Select primary tracks on the basis of their d0 Cut |d0| < nsd0(pt) sd0(pt) = svtx  strack(pt) parametrized resolution track vertex x y mark.heinz@yale.edu Winter Workshop, Feb 2007

Secondary vertex resolution (simulation) Determine position resolution for semi-leptonic heavy flavor vertices from PYTHIA Position resolution in x,y,z is ~180mm, no strong dependency on coordinate /e K SecVtx reconstruced- MC (cm) reconstruced- MC (cm) reconstruced- MC (cm) mark.heinz@yale.edu Winter Workshop, Feb 2007

Secondary vertex resolution (simulation) Study of vertex resolution as a function of hits in the inner tracker ITS-hits, maximum of 6 hits. mark.heinz@yale.edu Winter Workshop, Feb 2007

ALICE Set-up TRD ITS TPC Size: 16 x 26 meters Weight: 10,000 tons mark.heinz@yale.edu Winter Workshop, Feb 2007

ALICE Electromagnetic Calorimeter Lead-scintillator sampling calorimeter Shashlik fiber geometry Avalanche photodiode readout Coverage: |h|<0.7, Df=110o mark.heinz@yale.edu Winter Workshop, Feb 2007

ALICE EMCAL (2) 12 supermodules 24 strips in η 12 (or 6) modules in φ 12672 elementary sensors (towers) 77 alternating layers of 1.44 mm Pb (1% Sb) 1.76 mm polystirene scintillator Dh x Df = 0.014x0.014 Module (2x2 towers) mark.heinz@yale.edu Winter Workshop, Feb 2007

EMCAL energy resolution Energy resolution has been measured and is within specifications ~12%/E +2% Production Module Spec Prototype Module Spec mark.heinz@yale.edu Winter Workshop, Feb 2007

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) mark.heinz@yale.edu Winter Workshop, Feb 2007

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 mark.heinz@yale.edu Winter Workshop, Feb 2007

EMCAL PID e/p discrimination p/E distribution g/p0 discrimination Cluster shape analysis Effective mass Cluster in EMCAL  ° hadrons Study by Guenole Bourdaud mark.heinz@yale.edu Winter Workshop, Feb 2007

Hadron/p0 discrimination Granularity study of EMCAL Granularity 2x2 Granularity 3x3 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) mark.heinz@yale.edu Winter Workshop, Feb 2007

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 Cluster Matching Prob for electrons dN/dη = 4000 % Mult = 10 % Study by A.Pulvirenti (Catania) mark.heinz@yale.edu Winter Workshop, Feb 2007

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 mark.heinz@yale.edu Winter Workshop, Feb 2007