heavy flavour capabilities with the alice trd benjamin dönigus 20.09.2008 isnp 2008 erice/sicily
TRANSCRIPT
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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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
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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
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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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