Heavy flavour capabilities with the ALICE TRD

Benjamin Dönigus

20.09.2008

ISNP 2008

Erice/Sicily

Outline

• Motivation

• The ALICE experiment at the LHC

• Heavy flavoured mesons– Quarkonia– Open beauty

• Heavy flavoured baryons

• Conclusion

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Physics Motivation• Charm and beauty quarks have

heavy mass composition through the coupling to Higgs field

• In QGP where the chiral symmetry might be restored, charm and beauty quarks remains heavy

• Charm and beauty are a good probe for the medium

The measurement of charm/beauty cross section allows:

• Test of pQCD (scales F, R)• Probe parton distributions• Probe heavy-quark energy loss• Baseline for J/ enhancement

(suppression) in Pb + Pb[1]

X. Zhu, M. Bleicher, K. Schweda, H. Stöcker, N. Xu et al., PLB 647 (2007) 366.[1] P. Braun-Munzinger and J. Stachel, Nature 448(2007)302

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4

Production cross sections

c(LHC) = c(RHIC) × 25

b(LHC) = b(RHIC) × 100

jet(LHC) = jet(RHIC) x 105

K. Safarik, CERN, Geneva

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Production of cc & bb pairs in different LHC running modes

Most b-quarks emerge in B-mesons, significant fraction in b baryons

Most c-quarks emerge in D-mesons, a good fraction in c baryons, e.g. in every HI collision around 7 D s and 1 c is created in the acceptance

0

D0D

Ds

c

J

ALICE Collaboration et al 2006 J. Phys. G: Nucl. Part. Phys. 32 1295-2040

Statistics plot: H. Yang and Y. Wang

Size: 16 x 26 meters

Weight: 10,000 tonnes

ALICEA Large Ion Collider Experiment

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1000 physicists31 countries109 institutes

Particle Identification in ALICE

• ‘stable’ hadrons (π, K, p): 100 MeV/c < p < 5 GeV/c; (π and p with ~ 80 % purity to ~ 60 GeV/c)• dE/dx in silicon (ITS) and gas (TPC) + time-of-flight (TOF) + Cherenkov (RICH)

• decay topologies (K0, K+, K-, , D)• K and decays beyond 10 GeV/c

• leptons (e,μ ), photons, π0

• electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π0 in PHOS: 1 < p < 80 GeV/c

• excellent particle ID up to ~ 50 to 60 GeV/c7

• electron ID in central barrel p>1 GeV/c

• fast trigger for high momentum particles (hadrons, electrons) within ~6 s

• 540 detectors ~ 760m2

• 18 supermodules

• length: 7m

• X/X0 ~ 22 %

• 28 m3 Xe/CO2 (85/15)

• 1.2 million readout channels

Transition Radiation Detector (TRD)

ALICE TRD

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SM09

SM08

SM00

SM17

4/18 supermodules installedwill be completed for the first heavy ion run 2010

TRD PID

A. Bercuci, GSI, Darmstadt & A. Wilk, IKP, Münster

Definition:Fraction of particles wrongly identified as electrons @ 90% electron efficiency

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QuarkoniaSignal from quarkoniaFor PbPb collisions at 5.5 TeV per nucleon pair

• 1 year statistics• 2x10 events• 10 % central• pt > 1 GeV/c

Measure the yield of J/ and the family

8

W.Sommer, IKF, Frankfurt

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B → e + X

Branching Ratio = 21%– 11% from b → B → e+X– 10% from b → B → D → e+X

PrimaryVertex B

e

Xd0

rec. track

Open beauty

c (D0)~123 m c (B) ~500 m

Electron Identification (TPC+TRD)(separation between e/)

Kinematical Cuts (in d0 according to the pt bin)

ALICE Collaboration et al 2006 J. Phys. G: Nucl. Part. Phys. 32 1295-2040

Heavy flavoured baryons• The baryon/meson ratio measured at RHIC showed an anomalous

enhancement for lighter quarks.• Measurements also showed that at RHIC the heavy quark

quenching is stronger than in theoretical predictions as seen in the RAA for non-photonic electrons.

G. Martínez-García et al 2008 J. Phys. G: Nucl. Part. Phys. 35 044023

e-

+

K-

b0

p

c+

c =369 m

c =60 m

Trigger

lPrimary Vertex

Decay Vertex 1Decay Vertex 2

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369 m

60 m

b c e e with c p K- +

b = udbc = udc

b is the simplest baryon which contains a beauty quarkand has a semileptonic decay into c e of 5% branchingratio

b & c have up to now not be measuredat heavy ion collisions

--

14CDF note 7635

• Detect c K p and

• carries the missing mass/energy

very broad distribution (~ 2 GeV)

fits MC expectations

• 173 pb (April 2006 – September 2007)

• Trigger used (pt > 2 GeV/c)

+ +

-1

CDF results for b

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Pythia results for b c e Reconstruction of the invariant mass without the anti-neutrino leads to a similar distribution as measured at CDF

Study e-Trigger with TRD

-

Conclusion

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• ALICE is a general purpose heavy ion experiment which will help to understand matter under extreme conditions

• The ALICE TRD will provide a good electron identification and a electron trigger for pt > 3 GeV/c

• Heavy-quark hadrons carry unique information on QCD-medium  properties created at the LHC

• TRD will help to identify electrons from heavy-quark decays

Thank you!

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