Reconstruction Charm and Bottom with the ALICE EMCAL

Mark Heinz for the ALICE collaborationYale University

Winter Workshop of Nuclear DynamicsBig Sky, Montana, Feb 2007

mark.heinz@yale.edu Winter Workshop, Feb 2007 2

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 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.

mark.heinz@yale.edu 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)

mark.heinz@yale.edu 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)

mark.heinz@yale.edu 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))

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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.

mark.heinz@yale.edu Winter Workshop, Feb 2007 13

ALICE Set-up

TRD ITS

TPC

Size: 16 x 26 meters

Weight: 10,000 tons

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

ALICE Electromagnetic Calorimeter

Coverage: ||<0.7, =110o

Lead-scintillator sampling calorimeterShashlik fiber geometry Avalanche photodiode readout

mark.heinz@yale.edu 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)

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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)

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

mark.heinz@yale.edu 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

% %

mark.heinz@yale.edu 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