reconstruction charm and bottom with the alice emcal
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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, Montana, Feb 2007. Outline. Physics Motivation Method for reconstructing Bottom via displaced vertices - PowerPoint PPT PresentationTRANSCRIPT
Reconstruction Charm and Bottom with the ALICE EMCAL
Mark Heinz for the ALICE collaborationYale University
Winter Workshop of Nuclear DynamicsBig Sky, Montana, Feb 2007
[email protected] Winter Workshop, Feb 2007 2
Outline
Physics Motivation Method for reconstructing Bottom via
displaced vertices ALICE Electromagnetic Calorimeter EMCAL simulation status Conclusion
[email protected] Winter Workshop, Feb 2007 3
Physics Motivation Current theoretical estimates for bottom and
charm production still have large uncertainties.
NLO pQCD, pp, s = 14 TeV
CERN/LHCC 2005-014,hep-ph/0601164
MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.
[email protected] Winter Workshop, Feb 2007 4
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 pT
Similar uncertainties are present for LHC energies
non phot. el.
STAR, submitted to PRL (nucl-ex/0607012)
[email protected] Winter Workshop, Feb 2007 5
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: conversions (0 ) 0, ’ Dalitz decays , , … decays (negligible) Ke3 decays (neglible)
[email protected] Winter Workshop, Feb 2007 6
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
D0
B-
e-
K
/e
Pe+K
r
PrimVtx
SecVtx
Reminder:B c: ~500 mD c: ~100 m
Signed DCA: Lxy= r .pe+k / |pe+k|
Lxy
CDF Phys.Rev.D66 (2002))
[email protected] Winter Workshop, Feb 2007 7
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
Lxy (cm)
Efficiency of method improves significantly with #ITS hits
[email protected] Winter Workshop, Feb 2007 8
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
[email protected] Winter Workshop, Feb 2007 9
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 TeVMinbias PYTHIA, 14 TeV
[email protected] Winter Workshop, Feb 2007 10
Track impact parameter resolution Primary vertex finding proceeds in 2 passes Select primary tracks on the basis of their d0
Cut |d0| < nd0(pt)
d0(pt) = vtx track(pt)
track
vertex x
y
parametrized resolution
[email protected] Winter Workshop, Feb 2007 11
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) reconstruced- MC (cm) reconstruced- MC (cm)
K
/e
SecVtx
[email protected] Winter Workshop, Feb 2007 12
Secondary vertex resolution (simulation)
Study of vertex resolution as a function of hits in the inner tracker ITS-hits, maximum of 6 hits.
[email protected] Winter Workshop, Feb 2007 13
ALICE Set-up
TRD ITS
TPC
Size: 16 x 26 meters
Weight: 10,000 tons
[email protected] Winter Workshop, Feb 2007 14
ALICE Electromagnetic Calorimeter
Coverage: ||<0.7, =110o
Lead-scintillator sampling calorimeterShashlik fiber geometry Avalanche photodiode readout
[email protected] Winter Workshop, Feb 2007 15
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 x = 0.014x0.014
Supermodule
Module (2x2 towers)
[email protected] Winter Workshop, Feb 2007 16
EMCAL energy resolution
Energy resolution has been measured and is within specifications ~12%/E +2%
Production Module Spec Prototype Module Spec
[email protected] Winter Workshop, Feb 2007 17
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)
[email protected] Winter Workshop, Feb 2007 18
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
[email protected] Winter Workshop, Feb 2007 19
EMCAL PID
Cluster in EMCAL
°
hadrons
Study by Guenole Bourdaud
e discrimination p/E distribution
discrimination Cluster shape analysis Effective mass
[email protected] Winter Workshop, Feb 2007 20
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 2x2 Granularity 3x3
[email protected] Winter Workshop, Feb 2007 21
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
% %
[email protected] Winter Workshop, Feb 2007 22
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