Transcript Probing Properties of the QCD Medium via Heavy Quark

Recent STAR Results on NPE and
Hyperon-Hyperon Correlations
Huan Zhong Huang
黄焕中
Department of Physics and Astronomy
University of California
Los Angeles, CA 90095-1547
July 23-25, 2012, STAR Regional Meeting @ SDU
Outline
1) Parton Energy Loss and Jet-Medium Interaction
2) Heavy Ion Collisions as Exotic Factory Facility
3) Outlook
2
A QCD Partonic Matter in Heavy Ion Collisions
QCD – fundamental corner stone of the Standard Model
- Condense Matter Physics with underlying QCD interaction
partonic
hadronic
Three Intriguing Aspects:
-- QCD Topological Objects/CME/LPV
-- Properties of QCD Partonic Matter
-- QCD Phases and Phase Boundary
Heavy Quarks @RHIC:
Mostly produced at t=0, and an excellent probe for
3
properties of QCD matter !
pT Scales and Physical Processes
RCP
Three PT Regions:
-- Fragmentation
-- multi-parton dynamics
(recombination or
coalescence or …)
-- Hydrodynamics
(constituent quarks ?
parton dynamics
from gluons to
constituent quarks? )
Need NPE to access
high pT region !
4
Jet – Medium Interactions
Jet and/or medium
induced particle
emission
Jet-h or NPE-h
correlations
Away-Side
Near-Side
Leading particle
jet energy loss
(trigger)
RAA and v2
Trig-hadron angular correlations Df = ftrig-fhadron
NPE spectra and RAA
Most central 5% AuAu collisions
Scaled NPE in p+p
NPE RAA
NPE spectrum in AuAu
from Wenqin Xu’s thesis
RAA~ 0.3 at pT= 4-6 GeV/c, NPE indeed suppressed !
6
Model comparison
Model calculation,
impact parameter =0,
i.e. 0% central
This analysis,
0-5% central
M. He, R. J. Fries, R. Rapp,
arXiv:1106.6006
Model: heavy quarks collide with light quarks and form hadrons
A non-perturbative process, with effective potential from LQCD
About 4 times larger collision cross-section than
pQCD considerations, and agrees with data
7
Bottom versus Charm in the Model
M. He, R. J. Fries, R. Rapp, arXiv:1106.6006
Both data and theory
have large uncertainty
c/b
very different
1: hadron formation (non-pQCD) in medium (?), parameter tuning
2: Bottom (B-mesons) loss much less energy than Charm quarks (D-mesons)
bottom/charm ratio is not precisely known,
Large uncertainty on model RAA
8
Heavy Quark Elliptic flow
RAA alone is not sufficient ! More constraints –
e.g., differential suppression w.r.t. azimuthal angle
-- caused by HQ thermalization (low pT) and/or different path lengths (high pT)
y
ϕ, azithmual
x
Longer path length
More energy loss
Shorter path length
Less energy loss
dL
d  DE 
dn


df
df
df
or
Path length dependence
of energy loss generates v2

The path-length-dependence sensitive to different mechanisms:
Collision Energy Loss: DE  L
Radiative Energy Loss: DE  L2
ADS/CFT Energy Loss: DE  L3
smaller v2
larger v2
9
Results and model comparison
This analysis
Measured NPE v2
• charm/bottom combined
• very statistically limited at higher pT
• 0-60% centrality
Same Model
for RAA
Model NPE v2 < Measured NPE v2
• smaller but Close
• different centrality in model:
b =7.0 fm ~ 40%centrality
Sizeable NPE elliptic flow: yes
Heavy Quark elliptic flow : not necessarily
To identify path-length-dependence
need more statistics to reach high pT
c
u
D0
K

e

10
Conic Emission or V3 Initial Geometry
More particles are
emitted in a cone
direction on the
away-side !!
Dynamics:
Mach cone effect
from supersonic
jets passing thru
the medium?
Gluon radiation?
parton scattering?
Geometry:
v3 initial state
Use Heavy Quarks!!
pTtrig = 2.5-4.0 GeV/c; pTasso = 1.0-2.5 GeV/c
Au+Au
Mark Horner (for STAR Collaboration):
J. Phys. G: Nucl. Part. Phys. 34 (2007) S995
11
NPE-h Correlation
Raw NPE-h
[1 2 v 2,npe  v 2,h  cos(2 Df)]
v 2,npe = 0.05 ~ 0.10
Subtract the
assume NPE v2=5%
modulated v2 background

 v =10%
assume NPE
2
Broadening
in the away-side
Energy Loss
or else ?
12
Remarks on Parton E Loss
Parton Energy Loss  Hadron PT Scale > 5-6 GeV/c
Intrinsically a Dynamical Evolution System (path length?) !
-- Rapid Decrease of Energy Density with Evolution Time
-- Even partons originated from the center of the
hot/dense fireball may escape
Theoretically Eloss calculations – dynamic issue
simultaneous calculation of RAA and v2 at high pT !!
Medium Response to Jets Plowing Through
-- Heavy quark interactions with medium
- non-photonic electron – hadron correlations
- D – h correlations , NPE-NPE correlations
-- Separate Charm and Bottom energy loss
– Heavy Flavor Tracker Upgrade– 2014 !
13
Discoveries from Unexpected Areas?!
RHIC -- Frontier for bulk partonic matter formation
(quark clustering and rapid hadronization)
-- Factory for exotic particles/phenomena
Potential exotic particles/phenomena:
penta-quark states (uudds, uudds!)
di-baryons
H – (LL, uuddss)
[WW] (ssssss)
strange quark matter
meta-stable Parity/CP odd vacuum bubbles
disoriented chiral condensate
……
STAR’s capability has been enhanced greatly with recent upgrades !!
14
Physics Information in Correlation Function
LL Correlation Function:
both Ls from the primary vertex –
if there is a LL resonance state
-- enhanced peak at resonance
and attractive LL interactions
if there is a bound state H, then two
Ls near threshold can form H
-- depletion of LL correlations
(WRT a reference?!)
(if we can measure p-n correlation,
the effect of deuteron formation)
both Ls from secondary vertices –
weak decay product – [X-L] state? 15
Correlation Function and Direct
Decay Searches Complementary
Correlation Function – Depletion of phase space due
to bound state formation
-- inclusive, sensitive to total yield
Direct Searches
-- depend on branching ratio
If H(uuddss) is a weakly bound state with a binding
energy ~ 10s MeV as predicted by recent
Lattice QCD calculations,
HL+p+p
branching ratio?
16
Search for di-hyperons and study hyperon-hyperon
interactions from correlation measurement
•
0-40% Au+Au @ 200 GeV
 The scattering length (a0) and the
effective range (reff) with no, weak,
medium, and strong coupling to X-N :
a0 (fm)
STAR Preliminary
Set A – Weak XN coupling
Set B – Medium XN coupling
Set C – Strong XN coupling
reff (fm)
No coupling
-2.42
-6.36
weak (Set.A)
-2.47
-6.65
medium (Set.B) -2.98
-13.53
strong (Set.C)
-2.61
-2.27
 Current fit parameters is consistent
with non-existence of a strongly bound
state of LL
Fit A. Ohnishi and T. Furumoto
17
Search the Lpp Channel
~ 23 M events
Lcandidates – mass within 4 MeV of PDG value
pp pair – mass below L PDG mass by 5 MeV
0-10 % Au+Au @ 200
GeV
18
Search the Lpp Channel
The rotational method reproduces the background better
Nature is not kind enough to give us ‘H’ particle
We will continue to search for other candidates
0-10 % Au+Au @ 200 GeV
LL
19
RHIC – a dedicated QCD Facility
Having a great run!
Even greater potential for
future discoveries !
AA
pp
(spin)
(Deconfinement
Phase Transition)
Exotic
pA
(CGC,EMC)
20
End
21
An Equilibrated Partonic System
L
X
W
Volcanic mediate pT – Spatter (clumps)
Use coalescence picture to study
partons at the phase boundary
22
Effective Parton Distribution in the QM Drop at Hadronization
L
X
f
Parton Spectroscopy at RHIC
W
Use particle emission to
measure parton pT distribution
and angular anisotropy (v2)
in the dense parton drop !!
More theoretical development –
He, Fries and Rapp, Phys.Rev. C82 (2010) 034907
23
Features of Partonic Matter
L
Central Au+Au Collisions at RHIC
Bulk Partonic Matter -1) parton collectivity, multiparton dynamics
coalescence/recombination
X
2) v2 and pT distributions
for effective quarks -W evolution from gluons –
constituent quarks
3) Intriguing dynamics of baryon
rich matter at low energy
4) Major shift in DOF between 11-39 GeV?!
24
W/f ratios @ 11.5 GeV also deviates from 39-200 GeV
What is the collision energy where the deviation from
partonic dominated matter becomes eminent?
-- 2011 data from 19.6 and 27.0 GeV Au+Au collisions
-- Perhaps more scan between 11.5 and 19.6 needed 25
V2 and RAA are Related
Precise value of
v2 at pT > 6, 10 GeV/c ?
RAA at pT > 10 GeV/c at RHIC
should RAA approach
unity at higher pT ?
Future measurements will
shed more lights on possible
physical scenarios for
parton energy loss
dynamics !
Heavy Quarks will be special
-- Lorentz g dependence
on parton ELoss
on jet-medium interaction
near-side vs away-side?
26
Nucleus-Nucleus Collisions and Volcanic Eruption
Volcanic high pT -- Strombolian eruption
Volcanic mediate pT – Spatter (clumps)
27
Volcanic low pT – Bulk matter flows