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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 1 Consequences of a c /D enhancement effect on the non-photonic electron nuclear modification factor in central heavy-ion collisions at RHIC G. Martinez-Garcia, S. Gadrat and P. Crochet, Phys. Lett. B 663 (2008) 55 also P. Sorensen and X. Dong, Phys. Rev. C 74 (2006) 024902 Outline 1. Non-photonic electron (NPE) R AA @ RHIC 2. “anomalous” baryon/meson enhancement @ RHIC 3. Putting 1. & 2. together or how a charm baryon/meson enhancement lowers the NPE R AA
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 2 NPE R AA @ RHIC PHENIX: A. Adare et al., Phys. Rev. Lett. 98 (2007) 172301, STAR: B. I. Abelev et al., Phys. Rev. Lett. 98 (2007) 192301 charm & bottom energy loss via NPE R AA p t < 3-4 GeV/c: NPE R AA < 0 R AA, as expected (color charge & dead-cone) p t > 4-5 GeV/c: NPE R AA ~ 0 R AA, puzzling… quantitative agreement between PHENIX & STAR PHENIX STAR NPE R AA vs hadron R AA ? b vs c contributions?
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 3
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 4
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 6 What if this applies also to the c /D ratio? sizeable yield of c w.r.t. D mesons in pp @ 200GeV BR( c e+X) < BR(D e+X) a c /D enhancement lowers the yield of NPE in HIC NPE R AA is not exclusively sensitive to heavy quark dE/dx
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 7 The proof in numbers assumptions: binary scaling same relative yield of D mesons in pp & AA collisions with C the c /D enhancement factor and pp collisions @ 200 GeV (with particle yield from PYTHIA) R AA = 0.90(0.79) for c /D = 0.35(0.84) i.e. C = 5(12)
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 8 Differences light vs heavy for recombination process transverse momentum (I) p t of a light meson(baryon) = 2(3) times p t of the valence quarks p t of a heavy (simple) hadron ~ p t of the heavy quark transverse momentum (II) for the same velocity, p t of a light(heavy) quark is small(large) recombination of heavy quark appears at larger p t ? the light(heavy) quark fragmentation time is large(small) ~ 25, 1.6 & 0.4 fm/c for a 10 GeV/c , D & B meson* recombination of light & heavy quarks qualitatively different *A. Adil & I. Vitev, Phys. Lett. B 649 (2007) 139
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 9 Predictions on c /D enhancement diquark correlations quark recombination percolation of strings recombination & percolation agree quantitatively: c /D ~ 0.3 @ p t ~ 5-6 GeV/c diquark correlations predict larger enhancement L. Cunquiero et al., Eur. Phys. J. C 53 (2008) 585, C. Pajares, private communication, V. Greco, http://alice.pd.infn.it/quenchingDay.html, S.H. Lee et al., arXiv:0709.3637v2 [nucl-th]
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 10 First study on c /D enhancement vs NPE R AA ~20% P. Sorensen and X. Dong, Phys. Rev. C 74 (2006) 024902 main assumption: c /D(p t ) identical to measured /K 0 s (p t ) large enhancement (a factor 20) located at low p t (< 5GeV/c) 20% suppression at p t ~ 2.5 GeV/c
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 11 The approach revisited S. Sorensen and X. Dong, Phys. Rev. C 74 (2006) 024902 our study, Phys. Lett. B 663 (2008) 55 c /D shape in AuAuas /K 0 S data Gaussian c /D shape in ppas /K 0 S data PYTHIA maximum of c /D ratio ~1.7 at p t ~3 GeV/c~0.9 at p t ~5 GeV/c energy losshadron shape scaling S.Wicks et al., Nucl. Phys. A 784 (2007) 426 electrons from B decaynoyes
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 12 Simulation steps 1. baseline: pp @ 200 GeV NPE (PYTHIA) 2. add c /D enhancement 3. add energy loss 4. add electrons from B decay
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 13 1) PYTHIA: pp collisions @ 200 GeV PYTHIA using PHENIX tuning (Phys. Rev. Lett. 88 (2002) 192303) PYTHIA slightly softer than PHENIX & agrees with FONLL (as in PRL 97 (2002) 252002) decay electrons from c have a softer spectrum than decay electrons from D suppression of NPE in AA collisions is further enhanced for p t >~ 2 GeV/c
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 14 2) folding-in the c /D enhancement p t -differential charm cross-section is conserved R AA = (dN/dp t with c /D enhanc.) / (dN/dp t w/o c /D enhanc.) assumption for c /D vs p t : Gaussian with mean=5 GeV/c, cte=0.9, =2.9 GeV/c
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 15 NPE R AA with c /D enhancement (only NPE from charm here) c /D enhancement results in ~ 40% of suppression for p t ~ 2-4 GeV/c smaller suppression (20%) at large p t (due to the Gaussian shape) comparison limited to p t > 2 GeV/c (shadowing not included)
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 16 3) including energy loss (only NPE from charm here) rad. & col. energy loss from S. Wicks et al., Nucl. Phys. A 784 (2007) 426 suppression from col. energy loss ~ suppression from c /D enhancement R AA with all effects ~ 0.2 for p t > 3 GeV/c (similar to that of light hadrons)
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 17 4) including electrons from B decay theoretical uncertainties in m Q, F / 0, R / 0, PDF charm/bottom crossing point from 2.5 to 10.5 GeV/c (central value ~ 4.5 GeV/c) FONLL calculations from M. Cacciari et al., Phys. Rev. Lett. 95 (2005) 122001 pp @ 200GeV, FONLL
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 18 NPE R AA with c /D enhancement, dE/dx & e B 2 scenarios p t CP = 4.5 GeV/c (central) & p t CP = 10.5 GeV/c (highest) c /D enhancement is responsible for 10(25) % of the suppression for a charm/bottom crossing-point at 4.5(10.5) GeV/c
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 19 Summary a c /D enhancement, as observed for p/ +, /K s 0 & / , lowers the non-photonic electron R AA at intermediate p t by 10-25% because BR( c e+X) smaller than BR(D e+X) p t (e c ) softer than p t (e D) measurement of c /D urgently needed before solid conclusions from non-photonic electrons R AA can be drawn more details in Phys. Lett. B 663 (2008) 55
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Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08Philippe.Crochet@clermont.in2p3.frBad Honnef, 27/06/08 20 Outlooks: c /D enhancement & NPE flow toy model: build a sample of D 0 & c give them elliptic flow with PHENIX/STAR nq scaling let them decay get decay electron v2 vs. p t for different % of D 0 & c c /D enhancement increases NPE v2 detailed (PYTHIA) simulations in progress
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