Identified particle spectra and jet interactions with the medium

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Identified particle spectra and jet interactions
with the medium
Paul Sorensen Lawrence Berkeley National Lab
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Heavy Ion Goals and QCD

• Create a system of quasi-free quarks and gluons
• Learn about the EOS
• Study the deconfined-to-confined transition
• hadronization of the matter
• development of mass
• Determine properties of the matter
• energy density
• gluon density
• temperature T
• coupling ?s(Q, T)

Lattice QCD for finite temperature
Tc170 MeV
PDG
?s(Q)??s(Q,T/Tc)
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Modifications to ?s
heavy quark-antiquark coupling at finite T from
lattice QCD O.Kaczmarek, hep-lat/0503017
high Q2
low Q2
heating the vacuum modifies soft/long-wave-length
processes (like hadronization) At RHIC were
trying to probe these modifications
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probing the fireball
We cant perform scattering experiments with the
fireball so we rely on internally created probes.
This only tells us half the story.
But can we learn enough from the information we
have pT, ?, y? For example, can we determine the
dof from different pT regions?
?10 fm
?1 fm
0 fm lt?lt 1 fm
?0 fm
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review
nucl-ex/0412003

• First a large proton excess is observed.
• These measurements could be interpreted several
  ways flow, scaling with N-binary (i.e. absence
  of jet quenching), etc.
• Enhancement is noted to be related to the number
  of constituent quarks rather mass
• also an upper pT limit is placed on the baryon
  excess.
• Finally elliptic flow is found to scale with the
  number of quarks
• also the large baryon v2 excluded scenarios
  involving less energy loss for protons.

PHENIX PRC69, 0304909 (2004)
STAR Phys. Rev. C 72 (2005) 014904
Evidence gathered for modifications to
hadronization at intermediate pT
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Baryon to Meson
How might the B/M ratio be related to
modifications to hadronization?
Phenix PRL 91, 172301
Factorization is not likely to hold for these
collision at this pT fragmentation functions
become energy and system-size dependent
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Outline

• Azimuthal dependence of spectra
• Centrality dependence of spectra
• Jet interactions with the medium

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Event anisotropies
Azimuthal momentum-space anisotropy a self
quenching probe of early interactions
out-of-plane y
Au nucleus
in-plane
Au nucleus
sensitivity to the system geometry can arise
through secondary rescattering, soft-gluon
radiation, etc.
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v2 vs. pT
Large values indicate strong sensitivity to the
system geometry for production at all measured
pT v2 at intermediate pT is grouped by quark
number
Intermediate pT
PRL 92 (2004) 052302 PRL 91 (2003) 182301
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Extended pT
Year 4 data gives RHIC higher statistics and
greater coverage for identified particle v2
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Extended pT
Year 4 data gives RHIC higher statistics and
greater coverage for identified particle v2
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Extended pT
PHENIX/STAR comparison shows consistency Consisten
t with no particle type dependence at 7 GeV/c But
why not earlier?
PHENIX Preliminary ? Charged Hadrons
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Quark-number scaling

• Since hadronization is a soft process, it should
  be modified by changes to the shape of the
  running coupling at low Q2.
• In one simple hadronization model quark v2 is
  approximately related to hadron v2 through
• v2q v2h(pT/n)/n,
• where n is the number of quarks in the hadron
• implies v2 is developed before hadronization
• model implies deconfinement

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Run IV update
The observed scaling does not appear to follow
the simple 3 vs. 2 constituent quark number
relationship Is this related to a jet component,
a breakdown of simple approximations, or
something new? Numerical approximations give a
1 relative error Imperfect v2/n was also
anticipated within models incorporating more
realistic assumptions.
STAR Preliminary (Talk by M.Oldenburg)
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a closer look
STAR Preliminary
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comparison to predictions
Inclusion of gluons in recombination was
predicted to lead to a larger meson v2/n than
baryon v2/n B.Müller, et al. nucl-th/0503003
Tantalizing indication for the fate of gluons and
the nature of the constituents Systematic errors
on the data and calculations need to be carefully
addressed
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comparison to predictions
MPC Coalescence/Jetset jet fragmentation
contribution spatial correlations also can
spoil the scaling of v2/n D. Molnar
nucl-th/0406066
pT/n (GeV/c)

• Original quark v2 is not recovered by v2/n. The
  trend is correct but deviations are larger than
  whats seen in the data
• Calculations will also miss the Baryon to Meson
  ratio but the fragmentation component appears to
  show up in correlation measurements

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The multi-strange hadrons
Even the ?(ss), and ?(sss) have large v2 values
and appear to follow baryon vs. meson systematics

• (in)dependence of v2 on hadronic x-sections or
  flavor/mass
• can phi and Omega v2 be understood without
  prehadronic flow?

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v2 at intermediate pT
Constituent quarks appear to be the relevant
degrees-of-freedom just prior to
hadronization With sufficient precision we can
address questions about the nature of the
constituents and the microscopic nature of the
matter The centrality dependence of spectra
compliments v2 measurements
more quench (?pTlt0) v2 ? RCP ?
more flow (?pTgt0) v2 ? RCP ?
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the centrality dependence
v2 and RCP complimentary measures to probe flow
vs. energy loss. RCP is a better than RAA for
many studies because its not sensitive to the
change in chemistry from pp to AuAu
Baryon production increases more quickly with
collision overlap density than meson
production more evidence of constituent quark
number instead of mass
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Update on f?RCP
STAR Preliminary
Talk by Xiangzhou Cai
The ? RCP is well below proton or lambda RCP.
Consistent with NCQ scaling expectations. a
discrepancy arises between PHENIX and STAR RAA
(RAA ? RCP)
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Non-photonic electron RAA
Are Ds just like other mesons? There inclusive
yield scales with Nbin but the RAA is similar to
meson RAA. At intermediate pT, do we see
evidence for flow coalescence or do we only see
energy loss? v2 distinguishes between these
scenarios.
Comparing PHENIX and STAR electron RAA to charged
hadrons we note a similar and surprisingly large
suppression!
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electron v2 dE/dx or flow
See talk by F. Laue

• Collisional energy loss can give us charm RAA
  0.3 and v2 5
• A push from below (flow) is likely needed to get
  a larger charm v2.
• D v25 can come from v2c0 coalescence or
  v2c5 no coal.

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Lower energy

• Features of the particle-type dependence are
  common to different energies. But the underlying
  behavior changes between 17.2 and 200 GeV
• At low energy RCP is larger but v2 is smaller.
  Reveals whats happening to the spectra change
  in underlying spectrum, more energy loss (?pTlt0)
  and more flow (?pTgt0)

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4-quark candidates
The centrality dependence of 4-quark-state
candidates (a0(980) and f0(980) for example) can
be used to probe their quark content.
accessible through ??- minv cocktail analysis
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Jet-like correlation structures
J. Adams et al, Phys. Rev. Lett. 91 (2003) 072304

• Dihadron correlations at intermediate pT indicate
  the presence of jet-like correlations
• Can these measurements be reconciled with the
  apparent non-fragmentation nature suggested by
  other measurements?
• Notice the enhanced near-side peak in AuAu well
  see more of this.

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identified trigger particles
PHENIX arXivnucl-ex/0408007
PHENIX arXivnucl-ex/0408007

• Baryons and mesons have similar probabilities to
  have an associated hadron
• But why do both of them have a higher
  probability to have an associated hadron in AuAu
  collisions than in pp collisions?
• This may arise from interactions between soft
  matter and hard partons. What indications do we
  have for this?

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identified trigger particles
PHENIX arXivnucl-ex/0408007
PHENIX arXivnucl-ex/0408007

• Mesons have a greater probability to have an
  associated hadron (thanks Barbara)
• But why do both of them have a higher
  probability to have an associated hadron in AuAu
  collisions than in pp collisions?
• This may arise from interactions between soft
  matter and hard partons. What indications do we
  have for this?

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mediums response to jets
Correlations from fluctuations
Subtract elliptic flow and the near-side
jet-peak Mediums response to an impinging jet is
revealed
The fluctuation bin-size dependences are related
to two-particle correlations Fluctuations are
inverted to autocorrelations
pick gluons from the vacuum
gluon density dNg/dy 1000
STAR Preliminary see posters by Duncan Prindle
look for modifications to particle composition in
the away-side/recoil region
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Near- and away-side B/M
away-side comoving partons enhance the
probability for baryon production
near-side like pp
The larger B/M ratio in the away side is also
suggestive of recombination wherever the
density of comoving constituents is larger
(in-plane, central vs. peripheral, and now in the
wake of quenched jets), it becomes easier to
produce baryons. We already knew that it was
partons losing energy in a dense medium, this may
help us determine if the matter is hadronic or
not (dAu?).
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Conclusions

• Production is highly sensitive to the fireball
  geometry. Either from
• - hadronization a long-wave-length/soft process
  or
• soft pushes (i.e. flow)
• quenching in medium (soft gluon radiation)
• Quark degrees of freedom are apparent from RCP,
  and v2
• the flavor dependence is apparently not from
  mass, quark vs. gluon, or hadronic cross-section.
  Rather, particles are grouped by constituent
  quark number.
• Measurements of large collectivity developed for
  ? and ? challenge any non-QGP or hadronic
  scenario
• Significant modification to ?s at low and
  intermediate Q2 are demonstrated through
  modifications to hadronization

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• Its highly interacting
• It doesnt appear to be hadronic
• What do we call it?

chiral symmetry breaking limit ?s,c0.43
(hep-ph/0302011)
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the end
Thanks to the organizers and S. Blyth, J. Chen,
X. Dong, H. Huang, Y. Lu, H-G. Ritter, A. Rose,
M. Oldenburg, K. Schweda, and N. Xu
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Jet remnants (thermalization)
What happens to a hard probe that traverses a
colored medium? Can we observe effects of
dissipation or thermalization?
Trigger pT 46 GeV/c
STAR Preliminary F. Wang, J.Phys.G30S1299-S1304,
2004
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Anti-baryon to baryon ratio
Also, notice that the pbar/p ratios dont yet
reach pQCD predictions
PHENIX PRC69, 0304909 (2004)
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Baryon/anti-baryon ratios
Au Au Central
Some indication of gluon vs. quark jet dependence
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year 4 ratios
AuAu Central
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year 4 RCP