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Heavy flavour capabilities with the ALICE TRD

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. Physics Motivation.

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Heavy flavour capabilities with the ALICE TRD

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  1. Heavy flavour capabilities with the ALICE TRD Benjamin Dönigus 20.09.2008 ISNP 2008 Erice/Sicily

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

  3. 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 + 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

  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 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 D D0 Statistics plot: H. Yang and Y. Wang 5 ALICE Collaboration et al 2006 J. Phys. G: Nucl. Part. Phys.32 1295-2040

  6. ALICE A Large Ion Collider Experiment • 1000 physicists • 31 countries • 109 institutes Size: 16 x 26 meters Weight: 10,000 tonnes

  7. 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-, L, D) • K and L 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/c

  8. electron ID in central barrel p>1 GeV/c fast trigger for high momentum particles (hadrons, electrons) within ~6 ms ALICE TRD Transition Radiation Detector (TRD) • 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

  9. TRD PID Definition: Fraction of particles wrongly identified as electrons @ 90% electron efficiency A. Bercuci, GSI, Darmstadt & A. Wilk, IKP, Münster

  10. Quarkonia • Signal from quarkonia • For 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/Y, Y´ and the U family 8 W.Sommer, IKF, Frankfurt

  11. rec. track e Open beauty Primary Vertex B X d0 • B → e + X • Branching Ratio= 21% • 11% from b → B → e+X • 10% from b → B → D → e+X ct (D0)~123 mm ct (B) ~500 mm Electron Identification (TPC+TRD) (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

  12. 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

  13. 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 Lce 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 13

  14. 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 > 2 GeV/c) -1 14 CDF note 7635

  15. 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

  16. 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 > 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

  17. Thank you!

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