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Heavy-to-light ratios as a test of medium-induced energy loss at RHIC and the LHC

N. Armesto. Heavy-to-light ratios as a test of medium-induced energy loss at RHIC and the LHC. Quark Matter 2005: 18th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions Budapest, August 4th-9th 2005. N éstor Armesto Departamento de Física de Partículas and

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Heavy-to-light ratios as a test of medium-induced energy loss at RHIC and the LHC

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  1. N. Armesto Heavy-to-light ratios as a testof medium-induced energy loss at RHIC and the LHC Quark Matter 2005: 18th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions Budapest, August 4th-9th 2005 Néstor Armesto Departamento de Física de Partículas and Instituto Galego de Física de Altas Enerxías Universidade de Santiago de Compostela 1

  2. N. Armesto Contents 1. Motivation. 2. Model. 3. Results for RHIC. 4. Results for the LHC. 5. Bottom at RHIC. 6. Conclusions. With Andrea Dainese (Padova), Carlos A. Salgado and Urs A. Wiedemann (CERN), Phys. Rev. D71 (2005) 054027 (hep-ph/0501225). Work in progress with the former plus Matteo Cacciari (Paris VI). 2 Heavy-to-light ratios as ...

  3. N. Armesto Genuine prediction of this approach: DE (g) > DE (q) > DE(Q) mass effect colour charge 1. Motivation: BDMPS/GLV/GWZ/ZW: interference of production and scatterings of the radiated gluon Characterization of the medium: 3 Heavy-to-light ratios as ...

  4. N. Armesto RHIC, no medium effects Quenching weights (www.pd.infn.it/~dainesea/qwmassive.html): probability for medium energy loss. • CTEQ4L pdf's, EKS98. • gg (qqbar) to QQbar, Q(bar)g to Q(bar)g. • g to QQbar (important for the LHC). • Ff into D (B) and semileptonic e-decays. • RHIC: tune to STAR D-meson data. • LHC: tune to NLO pQCD calculation. 2. Model (I): Standard LO pQCD (PYTHIA): 4 Heavy-to-light ratios as ...

  5. N. Armesto 2. Model (II): (Dainese et al '04; Eskola et al '04; poster by Loizides) Detailed modeling of geometry. pTparton>5 GeV Characteristic feature: the mass effect is smaller for smaller lengths. 5 Heavy-to-light ratios as ...

  6. N. Armesto RD/h=RAAD/RAAh (Dokshitzer-Kharzeev ’01). • q/g difference affects all pT. • Mass effects sizeable for pT<12 GeV. • Look at 7< pT<12 GeV. • v2 (expected ~ to that for h) and centrality dependence: work in progress. 3. Results for RHIC: 6 Heavy-to-light ratios as ...

  7. N. Armesto • Small trigger bias effect (i.e. difference between massless c and b). • 10<pT<20 GeV: charm sensitive to color (g at low x), bottom to mass. 4. Results for the LHC: Transport coefficient (density) scaled by multiplicity: factor 2.5 to 7 larger at the LHC than at RHIC (Armesto et al '04, Eskola et al '04). Charm Beauty 7 Heavy-to-light ratios as ...

  8. N. Armesto Data presented here by PHENIX and STAR are consistent with radiative energy loss provided the contribution from b is small. Greene van Leeuwen • FONLL(Cacciari et al '98; '01; '05)partonic spectra supplemented with radiative Eloss via quenching weights plus FONLL fragmentation: * Uncertainties (mass variation; conservative) upto pT=6 GeV. * RAuAue can be ~0.4 in the range 5<pT<10 GeV. 5. Bottom at RHIC (I): • RHIC data in AuAu: electron spectra (PHENIX: Butsyk, Kwon; STAR: Bielcik, Laue, Zhang), weak correlation in pT with D/B, and contribution from B decays (Djordjevic et al '05; talks by Djordjevic and Vogt). 8 Heavy-to-light ratios as ...

  9. N. Armesto Eskola et al '04 • Larger transport coefficient? (but upper bound to come, hopefully, from correlations (PHENIX: Grau; STAR: Dietel, Magestro)). • How well do we control the production of heavy flavours at RHIC? Cacciari et al '05 CDF '03, 1.96 TeV 5. Bottom at RHIC (II): If RAuAue<0.4 in the range 5<pT<10 GeV: • Strong interaction of heavy quarks with the medium; hadronization inside? (talks by Djordjevic, Rapp, Teaney). 9 Heavy-to-light ratios as ...

  10. N. Armesto 6. Conclusions: • Heavy flavours constitute an experimentally accessible testing ground for our understanding of radiative energy loss. • Both at RHIC and at the LHC heavy-to-light ratios offer solid possibilities to check the formalism like those presented here: D's for 7<pT<12 GeV at RHIC, and D's and B's for 10<pT<20 GeV at the LHC. • Problems with single electron spectra in AuAu at RHIC may have several solutions: new effects, hadronization in medium, further constraints on the transport coefficient, contribution from b decays,... • Data presented here by PHENIX and STAR are consistent with radiative energy loss provided the contribution from b's is small. • Clarification of this issue will demand (at RHIC and at the LHC): * pp/dAu reference to be controlled (e.g. Kharzeev et al '03): new possibilities to check our understanding of HF production. * If possible, data for mesons, not only for electrons. 10 Heavy-to-light ratios as ...

  11. N. Armesto Backup I: quenching weights Mass effect smaller for smaller R=qhat L3/2, so small for small lengths. 11 Heavy-to-light ratios as ...

  12. N. Armesto Backup II: bottom in FONLL Cacciari et al '03; '04 Reasonable description of b production. 12 Heavy-to-light ratios as ...

  13. N. Armesto Backup III: fixed vs. variable L To try to understand a disagreement with Djordjevic et al ‘05 • mc=1.5 GeV, mb=4.75 GeV; no fragmentation yet. • qhat=1.2 GeV2/fm with fixed L=6 fm reproduce RAA(0-10%) ~0.2 for pions. • A large fixed length produces a larger effect of the mass on the Eloss: mass effect small for small L. 13 Heavy-to-light ratios as ...

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