My Layout

1
Suppression of non-photonic electrons from charm
baryon enhancementP.
Sorensen and X. Dongnucl-ex/0512042
Paul Sorensen
2
First, well review baryon enhancements
then well see why the B/M is relevant
to charm physicsfinally Ill
show that we know less about charm quark energy
loss than we thought
Paul Sorensen
3
baryon enhancement
the faster increase of baryon production is
common to many systems it cant be q vs. g
fragmentation ? multi-parton dynamics (power
corrections, higher twist) common to many systems
and all measured baryons
4
?/? ratio
S-L. Blyth SQM06
M. Lamont QM2005
the O/? ratio shows a similar enhancement at
intermediate pT, perhaps peaking slightly higher
5
associated B/M ratio
away-side comoving q/g enhance the probability
for baryon production
near-side more like pp
The large away-side B/M ratio also points to
multi-gluon/quark dynamics wherever the density
of comoving constituents is larger in-plane
v2 central vs. peripheral RCP and now in the
wake of quenched jets, it becomes easier to
produce baryons.
6
associated B/M ratio
away-side comoving q/g enhance the probability
for baryon production
STAR Preliminary identified associated soon to
come
Leon and Jana
near-side more like pp
nPart
The large away-side B/M ratio also points to
multi-gluon/quark dynamics wherever the density
of comoving constituents is larger in-plane
v2 central vs. peripheral RCP and now in the
wake of quenched jets, it becomes easier to
produce baryons.
7
identified particle RAA/RCP
e-Print Archive nucl-ex/0510052

• A large suppression of hadrons is observed
• Measurements interpreted in terms of energy-loss
  for quarks and gluons in medium
• The suppression patterns depend on particle-type
• Baryons exhibit less suppression
• Measurements interpreted several ways
  hydro-like flow, protons scaling with N-binary,
  coalescence/recombination, gluon junctions etc.

8
lower v?sNN
Q Is the baryon enhancement just due to pion
suppression? A No, at v?s17.3 GeV, baryons
enhanced w/o pion suppression
NA57 G. Bruno, A. Dainese STAR M. Lamont
If the baryon enhancement is from a larger pT
kick (or flow) for baryons, why doesnt B/M
increase when the spectrum is steeper?
9
in-plane baryon enhancement

• At intermediate pT, v2 of hadrons display quark
  number dependence
• At lower pT, the anisotropy depends on hadron
  mass and is in qualitative agreement with
  hydrodynamic models (with a QGP EOS)
• Hadronic models predict 50 smaller v2

10
charm
but what does this have to do with heavy flavor?
What if ?c/D is enhanced as much as
?/K? Branching ratios to electrons ?c 4.5 ?
1.7 D0 6.87 ? 0.28 D? 17.2 ? 1.9 Ds
8 6-5
?c
11
dead cone expectations
Radiative energy loss of heavy quarks and light
quarks --- Probe the medium property !
from Xin Dong, QM Budapest
12
introducing a ?c/D enhancement
13
implications for electrons
change to decay electron spectrum
when ?c/D has the same form as ?/KS, even if the
charm yield follows Nbin scaling, electron
spectrum will be suppressed
14
c suppression and ?c enhancement

• Electron RAA for ?c/D enhanced and charm RAA
  similar to h? RAA
• Resulting electron RAA is below preliminary
  measurements!
• Energy loss for charm quarks may be smaller than
  for light quarks

15
preferred charm RAA
A ?2 analysis shows that for this scenario,
preliminary PHENIX data prefer charm hadron RAA
1.35 ? light hadron RAA
16
what about Ds/D0
enhance the Ds yield by 50 (for this plot the
Ds/D0 ratio is taken to be pT independent, not
really a good assumption) a Ds enhancement can
also contribute to an electron suppression
17
We dont know how high in pT to expect a ?c/D
ratio to extend Precise comparisons to models
need direct measurements Important physics
includes transport coefficients, eta/s etc.
18
direct D
Combined fit of direct D and non-photonic
electron spectra is not yet precise enough to
contradict this picture
19
conclusions
We dont know yet if charm quarks are suppressed
as much as up and down quarks That conclusion
relies on the assumption that only the underlying
charm spectrum is changing from pp to AuAu (not
particle ratios etc.) We shouldt assume, we
should measure
STAR Full Barrel ToF Micro-vertex Tracker
PHENIX Barrel Endcap SVT
20
?c
Some people love hot girls R. Snellings
Others prefer hot guys C. Markert
But everyone loves hot quarks! Thanks to
the organizers!
21
length hierarchy ?ltRhadron
J.Phys.G31S889-S896,2005 nucl-ex/0412003
For intermediate pT probes, RCP depends on the
number of quarks in the hadron. Production
increases more quickly for hadrons with three
instead of two quarks
pT indicates the length scale the hadron can
probe 0.6 lt pT/n (GeV/c) lt 2.0 0.33 gt ? (fm) gt
0.1 Evidence for a distance scale smaller than a
hadron (constituent quark)
externally internally generated probe