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Heavy-Quarks with ALICE  Some Highlights from the ALICE Physics Week in Prague March 2008

Heavy-Quarks with ALICE  Some Highlights from the ALICE Physics Week in Prague March 2008. Kai Schweda, University of Heidelberg / GSI Darmstadt. Outline. Motivation Total charm cross section with ALICE B  J/  + X feeddown 1 st day Detector Performance in p+p Summary.

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Heavy-Quarks with ALICE  Some Highlights from the ALICE Physics Week in Prague March 2008

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  1. Heavy-Quarks with ALICE  Some Highlights from the ALICE Physics Week in Prague March 2008 Kai Schweda, University of Heidelberg / GSI Darmstadt

  2. Outline • Motivation • Total charm cross section with ALICE • B  J/ + X feeddown • 1st day Detector Performance in p+p • Summary

  3. Higgs mass: electro-weak symmetry breaking. (current quark mass) • QCD mass: Chiral symmetry breaking. (constituent quark mass) • Strong interactions do not affect heavy-quark masses. • Important tool for studying properties of the hot/dense medium at RHIC and LHC. • Test pQCD predictions at RHIC and LHC. Quark Masses Total quark mass (MeV) X. Zhu, M. Bleicher, K.S., H. Stoecker, N. Xu et al., PLB 647 (2007) 366.

  4. Heavy - Quark Production • Charm x 10 • Beauty x 100 • 3) Heavy-quarks abundantly produced at LHC ! STAR data: A. Suaide, P. Djawothoto QM2006;Calcs.: R. Vogt.

  5. J/y Production P. Braun-Munzinger and J. Stachel, Nature 448 (2007) 302.  suppression,compared to scaled p+p  regeneration,enhancement (SPS) Low energy (SPS): few ccbar quarks in the system  suppression of J/y High energy (LHC): many ccbar pairs in the system  enhancement of J/y  Signal of de-confinement + thermalization of light quarks !

  6. Predictions for LHC • large ccbar production at LHC • corona effects negligible • regeneration of J/y dominates • striking centrality dependence Signature for QGP formation ! • Initial conditions at LHC ? scc A. Andronic et al., nucl-th/0701079.

  7. Charm at the LHC:testing pQCD at s = 14 TeV • Important test of pQCD in a new energy domain • D production not yet fully understood at Tevatron and RHIC • Need displaced vertex technique for precise heavy-flavor measurements Tevatron data: CDF PRL91 (2003) 241804, RHIC data: Y. Zhang, QM2008, FONLL calcs. R. Vogt, Eur. Phys. J.ST 155 (2008) 213.

  8. TOF (K/p id) TPC (tracking) K p ITS (vertexing) Hadronic charm in ALICE • D0 Kp • D+ Kpp Ds KKp D*  D0p D0 Kpr LcpKp under study

  9. D0 p+ + K- Reconstruction p+ K- D0, ct = 123 mm Plot: A. Shabetai

  10. Charm cross section in pp Expected sensitivity in comparison to pQCD: D0 Kp stat. err. vs # events ~1 month Detector configuration: ITS + TPC + TOF 1 year at nominal luminosity (109 pp events) Slide: A. Dainese, INFN - Italy.

  11. Slide: A. Dainese, INFN - Italy. Inner Tracking System (ITS) • Silicon Pixel Detector (SPD): • ~10M channels • 240 sensitive vol. (60 ladders) • Silicon Drift Detector (SDD): • ~133k channels • 260 sensitive vol. (36 ladders) • Silicon Strip Detector (SSD): • ~2.6M channels • 1698 sensitive vol. (72 ladders) SSD ITS total: 2198 alignable sensitive volumes  13188 d.o.f. SPD SDD

  12. Effect of ITS misalignment on d0 resolution • Impact parameter resol: strack = ascatter/pt  bmeas  cmisalign • Effect studied with full simulation of exptected initial (full+) and residual (after realignment) misalignments • See talk tomorrow • Effect on D0 measurement studied (next slides) null residual full full+ Slide: A. Dainese, INFN - Italy.

  13. Effect of misalignment on S/B and significance (S/S+B) • Residual misalignment: negligible effect • “Full” misalignment: 15-20% worsening of statistical errors

  14. Kinematical distributions:promptJ/yversus secondaryJ/y • rapidity and transverse momentum (all distribution normalized to 1 m.b. event) B  J/ + X Primary J/y y Secondary J/y but pT dependent Slide: Giuseppe E Bruno, Università di Bari and INFN - Italy.

  15. Kinematical distributions:promptJ/yversus secondaryJ/y • product of impact parameters d0xd0 Primary J/y Secondary J/y • Disentangle primordial J/from B  J/ decay • Determine bbar Slide: Giuseppe E Bruno, Università di Bari and INFN - Italy,also: Wolfgang Sommer, Uni Frankfurt.

  16. J/y  e+ + e- Reconstruction J/y: c c : b b • J/y e+ + e- (BR = 6%) • Reconstruct invariant mass • TRD identifies electrons • 4/18 SM installed for first p+p run  Identify quarkonia

  17. Summary • Heavy-quarks (c,b) carry important information on de-confinement and light-quark thermalization • Measure yield, spectra, correlations and v2 of:D0, D+, D*+, Ds, J/y, Lb,to identify and characterize QGP ! • ALICE is well suited for these studies

  18. Average Momentum Correlator – angular dependence • At full Df: <Dpt,1Dpt,2> = 199.5 +/- 6 (MeV/c)2 • or Spt~30 % Same event Mixed event • Enhanced correlations • Only FC produces correlations athighDf • Distinction of the baseline at middle Df – flat to 0 • Average Momentum Correlator as a sensitive measure of back to back correlations

  19. D p c c p D D Meson Pair Correlations : Some Results • Correlation variable studied: 103/N * dN/d(Df)  = (D) – (Dbar) • At low energies, D-Dbar production correlated! • Pythia describes these correlations! • How about LHC energies?  • E791 : Eur. Phys. J. direct C1 (1999) 4 • WA92 : Phys. Lett. B385 (1996) 487 • NA32 : PLB257 (1991) 519 , PLB302 (1993) 112, PLB353 (1995) 547 Georgios Tsildeakis,HD.

  20. Charm correlations c-cbar are correlated • Flavor creation: back to back • Gluon splitting: forward • Flavor excitation: flat Correlations vanish  frequent interactions among partons !  probe light-quark thermalization !

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