1 / 20

Consequences of a  c /D enhancement effect on the non-photonic electron nuclear modification

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

jolene
Download Presentation

Consequences of a  c /D enhancement effect on the non-photonic electron nuclear modification

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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 • Non-photonic electron (NPE) RAA @ RHIC • “anomalous” baryon/meson enhancement @ RHIC • Putting 1. & 2. together or how a charm baryon/meson enhancement lowers the NPE RAA

  2. NPE RAA @ RHIC STAR PHENIX • charm & bottom energy loss via NPE RAA • pt < 3-4 GeV/c: NPE RAA < 0 RAA, as expected (color charge & dead-cone) • pt > 4-5 GeV/c: NPE RAA ~ 0RAA, puzzling… • quantitative agreement between PHENIX & STAR • NPE RAA vs hadron RAA? • b vs c contributions? PHENIX: A. Adare et al., Phys. Rev. Lett. 98 (2007) 172301, STAR: B. I. Abelev et al., Phys. Rev. Lett. 98 (2007) 192301

  3. 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 RAA is not exclusively sensitive to heavy quark dE/dx  What if this applies also to the c/D ratio?

  4. assumptions: • binary scaling • same relative yield of D mesons in pp & AA collisions The proof in numbers with C the c/D enhancement factor and pp collisions @ 200 GeV (with particle yield from PYTHIA) RAA = 0.90(0.79) for c/D = 0.35(0.84) i.e. C = 5(12)

  5. Differences light vs heavy for recombination process • transverse momentum (I) • pt of a light meson(baryon) = 2(3) times pt of the valence quarks • pt of a heavy (simple) hadron ~ pt of the heavy quark • transverse momentum (II) • for the same velocity, pt of a light(heavy) quark is small(large) •  recombination of heavy quark appears at larger pt? • 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

  6. Predictions on c/D enhancement quark recombination percolation of strings • recombination & percolation agree quantitatively: c/D ~ 0.3 @ pt ~ 5-6 GeV/c • diquark correlations predict larger enhancement diquark correlations 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]

  7. First study on c/D enhancement vs NPE RAA P. Sorensen and X. Dong, Phys. Rev. C 74 (2006) 024902 • main assumption: c/D(pt) identical to measured /K0s(pt) • large enhancement (a factor 20) • located at low pt (< 5GeV/c) •  20% suppression at pt ~ 2.5 GeV/c ~20%

  8. The approach revisited

  9. Simulation steps • baseline: pp @ 200 GeV  NPE (PYTHIA) • add c/D enhancement • add energy loss • add electrons from B decay

  10. 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 pt >~ 2 GeV/c

  11. 2) folding-in the c/D enhancement assumption for c/D vs pt: Gaussian with mean=5 GeV/c, cte=0.9, =2.9 GeV/c • pt-differential charm cross-section is conserved • RAA = (dN/dpt with c/D enhanc.) / (dN/dpt w/o c/D enhanc.)

  12. NPE RAA with c/D enhancement (only NPE from charm here) • c/D enhancement results in ~ 40% of suppression for pt ~ 2-4 GeV/c • smaller suppression (20%) at large pt (due to the Gaussian shape) • comparison limited to pt > 2 GeV/c (shadowing not included)

  13. 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 • RAA with all effects ~ 0.2 for pt > 3 GeV/c (similar to that of light hadrons)

  14. 4) including electrons from B decay pp @ 200GeV, FONLL theoretical uncertainties in mQ, 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

  15. NPE RAA with c/D enhancement, dE/dx & e  B • 2 scenarios ptCP = 4.5 GeV/c (central) & ptCP = 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

  16. Summary • a c/D enhancement, as observed for p/+, /Ks0 & /, lowers the non-photonic electron RAA at intermediate pt by 10-25% because • BR(c  e+X) smaller than BR(D  e+X) • pt(e  c) softer than pt(e  D) • measurement of c/D urgently needed before solid conclusions from non-photonic electrons RAA can be drawn • more details in Phys. Lett. B 663 (2008) 55

  17. Outlooks: c/D enhancement & NPE flow • toy model: • build a sample of D0 & c • give them elliptic flow with PHENIX/STAR nq scaling • let them decay • get decay electron v2 vs. pt for different % of D0 & c  c/D enhancement increases NPE v2 detailed (PYTHIA) simulations in progress

More Related