Heavy flavour capabilities with the ALICE TRD

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Heavy flavour capabilities with the ALICE TRD

• Benjamin Dönigus
• 20.09.2008
• ISNP 2008
• Erice/Sicily

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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 mF, mR)
• Probe parton distributions
• Probe heavy-quark energy loss
• Baseline for J/y (U) enhancement (suppression) in
  Pb Pb1

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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Production cross sections
?c(LHC) ?c(RHIC) 25 ?b(LHC) ?b(RHIC)
100 ?jet(LHC) ?jet(RHIC) x 10
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K. Safarik, CERN, Geneva
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Production of cc bb pairs in different LHC
running modes
Most c-quarks emerge in D-mesons, a good
fraction in Lc baryons, e.g. in every HI
collision around 7 D s and 1 Lc is created in the
acceptance
J??
?c
Ds
0
Most b-quarks emerge in B-mesons, significant
fraction in Lb baryons
D0
D?
Statistics plot H. Yang and Y. Wang
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ALICE Collaboration et al 2006 J. Phys. G Nucl.
Part. Phys. 32 1295-2040
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ALICE
A Large Ion Collider Experiment

• 1000 physicists
• 31 countries
• 109 institutes

Size 16 x 26 meters Weight 10,000 tonnes
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Particle Identification in ALICE

• stable hadrons (p, K, p) 100 MeV/c lt p lt 5
  GeV/c (p 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-, L, D)
• K and L decays beyond 10 GeV/c
• leptons (e,µ ), photons, p0
• electrons TRD p gt 1 GeV/c, muons p gt 5 GeV/c,
  p0 in PHOS 1 lt p lt 80 GeV/c

• excellent particle ID up to 50 to 60 GeV/c

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ALICE TRD
Transition Radiation Detector (TRD)

• electron ID in central barrel pgt1 GeV/c
• fast trigger for high momentum particles
  (hadrons, electrons) within 6 ms

• 540 detectors 760m2
• 18 supermodules
• length 7m
• X/X0 22
• 28 m3 Xe/CO2 (85/15)
• 1.2 million readout channels

SM00
SM08
4/18 supermodules installed will be completed for
the first heavy ion run 2010
SM17
SM09
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TRD PID
Definition Fraction of particles wrongly
identified as electrons _at_ 90 electron efficiency
A. Bercuci, GSI, Darmstadt A. Wilk, IKP,
Münster
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Quarkonia

• Signal from quarkonia
• For PbPb collisions at
• 5.5 TeV per nucleon pair
• 1 year statistics
• 2x10 events
• 10 central
• pt gt 1 GeV/c
• Measure the yield of
• J/Y, Y and the U family

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W.Sommer, IKF, Frankfurt
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Open beauty

• B ? e X
• Branching Ratio 21
• 11 from b ? B ? eX
• 10 from b ? B ? D ? eX

ct (D0)123 mm ct (B) 500 mm
Electron Identification (TPCTRD) (separation
between e/p)
Kinematical Cuts (in d0 according to the pt
bin)
ALICE Collaboration et al 2006 J. Phys. G Nucl.
Part. Phys. 32 1295-2040
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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
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Lb ? Lc e ne with Lc ? p p K
-

Lb is the simplest baryon which contains a beauty
quark and has a semileptonic decay into Lc e n of
5 branching ratio Lb Lc have up to now not be
measured at heavy ion collisions
-
-
Trigger
p
p
Lb udb
K-
e-
Lc udc
Lc
Decay Vertex 1
Decay Vertex 2
60 mm
ct 60 mm
Lb0
ct 369 mm
369 mm
nl
Primary Vertex
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CDF results for Lb

• Detect Lc ? K p p and m
• nm carries the missing mass/energy
• ? very broad distribution ( 2 GeV)
• ? fits MC expectations
• 173 pb (April 2006 September 2007)
• m Trigger used (pt gt 2 GeV/c)

-1
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CDF note 7635
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Pythia results for Lb ? Lc e n
-
Reconstruction of the invariant mass without the
anti-neutrino leads to a similar distribution as
measured at CDF
? Study e-Trigger with TRD
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Conclusion

• 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 gt 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

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Thank you!