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Gines Martinez-Garcia * , Sebastien Gadrat *,# , and Philippe Crochet &

Consequences of a  c /D enhancement effect on the non-photonic electron nuclear modification factor in central heavy ion collisions at RHIC energies. Gines Martinez-Garcia * , Sebastien Gadrat *,# , and Philippe Crochet & (*) Subatech, Nantes, France (&) LPC Clermont Ferrand, France

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Gines Martinez-Garcia * , Sebastien Gadrat *,# , and Philippe Crochet &

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  1. Consequences of a c/D enhancement effect on the non-photonic electron nuclear modification factor in central heavy ion collisions at RHIC energies Gines Martinez-Garcia*, Sebastien Gadrat*,#, and Philippe Crochet& (*) Subatech, Nantes, France (&) LPC Clermont Ferrand, France (#) Now at LPSC, Grenoble, France Hot Quarks 2008, Estes Park, Colorado, USA. More details in Physics Letter B663 (2008) 55.

  2. Outline of the talk • Physics Motivations: • Non-photonic electron nuclear modification factor (RAA) at RHIC energies; • Enhancement of baryon/meson ratio at RHIC energies; • Enhancement of the c/D ratio in HIC: • Model to compute the consequences on the non-photonic electron RAA; • Considering all ingredients: • c/D enhancement; • Quark energy loss; • Beauty contribution. Sébastien Gadrat, Hot Quarks 08

  3. Non-photonic electron RAA @ RHIC PHENIX, PRL 172301 (2007) STAR, PRL 192301 (2007) • Non-photonic electrons are assumed to arise from the semi-leptonic decay of charm and beauty hadrons; • Suppression increases with the centrality of the collision; • Suppression similar to light hadron suppression at high pT; • Radiative energy loss is not enough to explain the data. Sébastien Gadrat, Hot Quarks 08

  4. e± RAA @ RHIC understood ? Sébastien Gadrat, Hot Quarks 08

  5. Baryon/meson enhancement @ RHIC STAR, nucl-ex/0703040 STAR, nucl-ex/0701052 STAR, nucl-ex/0703033 • already observed for light (u, d) and strange species ; • the heavier the baryon, the higher in pT the maximum occurs (Ω/Φ) ; • quark coalescence models qualitatively describe the data (PRC65, PRL90, PRC68, PRC67, JPG30, PRC70). Sébastien Gadrat, Hot Quarks 08

  6. What about a c/D enhancement in HIC ? BR(c  e anything) is smaller than any BR(D  e anything) • A relative enhancement of the c/D would lead to a « natural » single electrons suppression with respect to p+p scaling ! • e± RAAnot exclusively sensitive to heavy quarks dE/dx ! Sébastien Gadrat, Hot Quarks 08

  7. Proof in numbers… Perfect binary scaling Same D0,D+,Ds relative yields with C the c/D enhancement factor and pp collisions @ 200 GeV : RAA=0.90 (0.79) for c/D=0.35(0.84)  C=5 (12) Yields (Pythia phenix settings) c/D ~ 0.073 Sébastien Gadrat, Hot Quarks 08

  8. Theoretical predictions L. Cunqueiro & C. Pajares, Private communication & Eur. Phys J C53 585 (2008), arXiv:0712.0509v1 [hep-ph] V. Greco, Private communication & Quenching Day, INFN (2005) Lc/D Recombination Percolation of strings pT [GeV] • Enhancement of Lc/D is expected in HIC; • Maximum at 5-6 GeV/c; • Existence of diquarks correlations inthe sQGP; Diquark correlations Sébastien Gadrat, Hot Quarks 08 S. Yasui et al., arXiv:0803.1366v1 [nucl-th] S. H. Lee et al., arXiv:0709.3637v2 [nucl-th]

  9. First study of this effect done by P. Sorensen and X. Dong PRC74 024902 (2006), SQM06 & HQ06 • Assumptions: • use /Ks0 measured shapes asa reference for c/D ones; • the charm RAAis similar to light hadronsRAA. Results: • enhancement effect for low pT: 2 ≾ pT ≾ 5 GeV/c; • high value for the max c/D ratio required (~ 1.7 taken from the /Ks0); • suppression less than 20%. New RAA including c/D effect ~20% Sébastien Gadrat, Hot Quarks 08

  10. A more detailed study of the charm enhanced B/M effect on the non-photonic RAA Sébastien Gadrat, Hot Quarks 08

  11. Pythia: p+p at 200 GeV • PHENIX data are well reproduced by Pythia (tuned according to PRL88 192303 (2002)) though Pythia spectrum slightly softer; • Decay electrons from c exhibit a softer spectrum:  suppression of non-photonic electrons is further enhanced ! Sébastien Gadrat, Hot Quarks 08

  12. c/D enhancement hypothesis Evolution of the Lc/D (pT) assumed in the present work: Gaussian shape centred at 5 GeV, maximum at 0.9 and s=2.9 GeV; • Shape of theLc/D (pT) enhancement • pT differential cross section is conserved ; • dN/dpT with nuclear effects • RAA = • dN/dpT w/o any nuclear effect Sébastien Gadrat, Hot Quarks 08

  13. RAA(pT) from c/D enhancement Non-photonic electrons from charm • Natural suppression of the non-photonic electron till 40% in the pT region 2-4 GeV/c; • Suppression of 20% up to pT~9 GeV/c; Attention ! Shadowing has not been taken into account but only relevant for pT < 2GeV/c. Sébastien Gadrat, Hot Quarks 08

  14. RAA(pT) with c/D enhancement and charm energy loss • Collisional energy loss leads to a similar effect as c/D enhancement (light blue vs red); • Suppression 0.2 level, like light quarks seen for pT>3 GeV/c (blue); Sébastien Gadrat, Hot Quarks 08

  15. Beauty contribution T. Ullrich, Hard Probes 08 Crossing-points: 4.5 and 10.5 GeV/c • Not well known from experimental data; • Large uncertainty from theory (mc, mb, Qr, Qf); Sébastien Gadrat, Hot Quarks 08

  16. RAA (pT) with all the effects Additional suppression of the non-photonic electrons of 10(25)% due to c/D enhancement for a charm vs beauty crossing point of 4.5 (10.5) GeV/c; Sébastien Gadrat, Hot Quarks 08

  17. Conclusions • Enhancement of the c/D ratio in HIC would lead to a suppression of non-photonic electrons; • Assuming an enhancement similar to light hadrons with a maximum at pT=5 GeV, as expected from recombination models, the suppression of non-photonic electrons is increased by 10-25% in the pt range 4-9 GeV; • Direct measurement of open heavy flavour production are imperative before solid conclusion on the e± RAA can be drawn. Sébastien Gadrat, Hot Quarks 08

  18. PRELIMINARY minimum-bias Rapp & van Hees, PRC 71, 034907 (2005) Run-7 Perspectives Run-4 • Role of the c/D enhancement on the elliptic flow of non-photonic electron has to be understood … R. Averbeck, QM2008 Simulation in progress… Sébastien Gadrat, Hot Quarks 08

  19. Back up Sébastien Gadrat, Hot Quarks 08

  20. Other effects related to the chemical composition of heavy flavoured hadron • Enhancement of Ds meson production: • BR in the semi-leptonic channel is not well known 8+6-5 %. However, similar BR expected from the spectator model; • Small effect expected with this BR. • Enhancement of beauty B/M ratio: • The mass of the beauty quark being higher, beauty semi-leptonic decays exhibit similar behaviour in beauty hadrons. Expected from the spectator model; • Large enhancement is expected form diquarks correlations (factor 10); S. H. Lee et al., arXiv:0709.3637v2 Sébastien Gadrat, Hot Quarks 08

  21. Qualitative differences: light vs heavy quark recombination • For the same velocity, the pT of the heavy quark is larger, ~ mQ/mq factor: • Recombination extend to higher pT; • Estimation pTc~1 GeV x mc/mq = ~4 GeV (mc=1.25 GeV, mq=300 MeV); • Full pT : • Light: pT of the hadron (2 or 3) times the pT of the quarks; • Heavy: pT of the hadron slightly higher than the pT of the heavy quark; • The light (heavy) quark fragmentation time is long (short): • 20, 1.5 & 0.4 fm/c for a 10 GeV/c , D & B meson (hep-ph/0611109) Sébastien Gadrat, Hot Quarks 08

  22. New parameterisation Gaussian shape centred at ~7 GeV, maximum of 0.9 and  =2.9 GeV. 40% Sébastien Gadrat, Hot Quarks 08

  23. New parameterisation 10(25)% up to pT ~9 GeV/c for a charm vs beauty crossing point at 4.5(10.5) GeV/c! Sébastien Gadrat, Hot Quarks 08

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