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• 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 _at_ RHIC
• anomalous baryon/meson enhancement _at_ RHIC
• Putting 1. 2. together or how a charm
  baryon/meson enhancement lowers the NPE RAA

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NPE RAA _at_ RHIC
STAR
PHENIX

• charm bottom energy loss via NPE RAA
• pt lt 3-4 GeV/c NPE RAA lt ?0 RAA, as expected
  (color charge dead-cone)
• pt gt 4-5 GeV/c NPE RAA ?0 RAA, 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
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What if this applies also to the ?c/D ratio?
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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 _at_ 200 GeV (with particle yield
from PYTHIA)
RAA 0.90(0.79) for ?c/D 0.35(0.84) i.e. C
5(12)
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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
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Predictions on ?c/D enhancement
quark recombination
percolation of strings

• recombination percolation agree
  quantitatively ?c/D 0.3 _at_ 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., arXiv0709.3637v2 nucl-th
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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 (lt 5GeV/c)
• ? 20 suppression at pt 2.5 GeV/c

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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 AuAu as ?/K0S data Gaussian
?c/D shape in pp as ?/K0S data PYTHIA
maximum of ?c/D ratio 1.7 at pt 3 GeV/c 0.9 at pt 5 GeV/c
energy loss hadron shape scaling S.Wicks et al., Nucl. Phys. A 784 (2007) 426
electrons from B decay no yes
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Simulation steps

1. baseline pp _at_ 200 GeV ? NPE (PYTHIA)
2. add ?c/D enhancement
3. add energy loss
4. add electrons from B decay

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1) PYTHIA pp collisions _at_ 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 gt 2 GeV/c

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2) folding-in the ?c/D enhancement
assumption for ?c/D vs pt Gaussian with mean5
GeV/c, cte0.9, ?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.)

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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 gt 2 GeV/c (shadowing
  not included)

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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 gt 3 GeV/c
  (similar to that of light hadrons)

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4) including electrons from B decay
pp _at_ 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
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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

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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 ? eX) smaller than BR(D ? eX)
• 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

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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