Heavy flavour capabilities with the ALICE TRD Benjamin Dönigus ISNP 2008 Erice/Sicily

Outline Motivation The ALICE experiment at the LHC Heavy flavoured mesons –Quarkonia –Open beauty Heavy flavoured baryons Conclusion 2

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 3

4 Production cross sections  c (LHC) =  c (RHIC) × 25  b (LHC) =  b (RHIC) × 100  jet (LHC) =  jet (RHIC) x 10 5 K. Safarik, CERN, Geneva

5 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 D0D0 DD DsDs cc J  ALICE Collaboration et al 2006 J. Phys. G: Nucl. Part. Phys Statistics plot: H. Yang and Y. Wang

Size: 16 x 26 meters Weight: 10,000 tonnes ALICE A Large Ion Collider Experiment 6  1000 physicists  31 countries  109 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 (K 0, K +, K -, , D) K and  decays beyond 10 GeV/c leptons (e,μ ), photons, π 0 electrons TRD: p > 1 GeV/c, muons: p > 5 GeV/c, π 0 in PHOS: 1 < p < 80 GeV/c excellent particle ID up to ~ 50 to 60 GeV/c 7

electron ID in central barrel p>1 GeV/c fast trigger for high momentum particles (hadrons, electrons) within ~6  s 540 detectors ~ 760m 2 18 supermodules length: 7m X/X 0 ~ 22 % 28 m 3 Xe/CO 2 (85/15) 1.2 million readout channels Transition Radiation Detector (TRD) ALICE TRD 8 SM 09 SM 08 SM 00 SM 17 4/18 supermodules installed will 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 90% electron efficiency

10 Quarkonia Signal from quarkonia For PbPb collisions at 5.5 TeV per nucleon pair 1 year statistics 2x10 events 10 % central p t > 1 GeV/c  Measure the yield of J/  and the  family 8 W.Sommer, IKF, Frankfurt

11 B → e + X Branching Ratio = 21% –11% from b → B → e+X –10% from b → B → D → e+X Primary Vertex B e X d0d0 rec. track Open beauty c  (D 0 )~123  m c  (B) ~500  m Electron Identification (TPC+TRD) (separation between e/  ) Kinematical Cuts (in d 0 according to the p t bin) ALICE Collaboration et al 2006 J. Phys. G: Nucl. Part. Phys

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 R AA for non-photonic electrons. G. Martínez-García et al 2008 J. Phys. G: Nucl. Part. Phys

e-e- ++ K-K- b0b0 p c+c+ c  =369  m c  =60  m Trigger l Primary Vertex Decay Vertex 1 Decay Vertex  m 60  m  b   c e e with  c  p  K -+  b = udb  c = udc  b is the simplest baryon which contains a beauty quark and has a semileptonic decay into  c e of 5% branching ratio  b &  c have up to now not be measured at heavy ion collisions - -

14 CDF 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 (p t > 2 GeV/c) ++ CDF results for  b

15 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 16 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 p t > 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! 17