recent star results on npe and hyperon-hyperon correlations huan zhong huang 黄焕中 department of...
TRANSCRIPT
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
2
Outline
1) Parton Energy Loss and Jet-Medium Interaction
2) Heavy Ion Collisions as Exotic Factory Facility
3) Outlook
3
A QCD Partonic Matter in Heavy Ion Collisions
partonic hadronic
Three Intriguing Aspects: -- QCD Topological Objects/CME/LPV -- Properties of QCD Partonic Matter -- QCD Phases and Phase Boundary
QCD – fundamental corner stone of the Standard Model- Condense Matter Physics with underlying QCD interaction
Heavy Quarks @RHIC:Mostly produced at t=0, and an excellent probe for
properties of QCD matter !
4
pT Scales and Physical Processes
RCPThree 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 !
Jet – Medium Interactions
Leading particle jet energy loss
Jet and/or medium induced particle emission (trigger)
Trig-hadron angular correlations = Df ftrig-fhadron
Near-Side
Away-SideRAA and v2
Jet-h or NPE-hcorrelations
6
NPE spectra and RAA
RAA~ 0.3 at pT= 4-6 GeV/c, NPE indeed suppressed !
Most central 5% AuAu collisions
NPE spectrum in AuAufrom Wenqin Xu’s thesis
NPE RAA Scaled NPE in p+p
7
Model comparison
Model: heavy quarks collide with light quarks and form hadronsA non-perturbative process, with effective potential from LQCD
This analysis, 0-5% central
Model calculation,impact parameter =0, i.e. 0% central
M. He, R. J. Fries, R. Rapp, arXiv:1106.6006
About 4 times larger collision cross-section than pQCD considerations, and agrees with data
8
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
Bottom versus Charm in the ModelM. He, R. J. Fries, R. Rapp, arXiv:1106.6006
Both data and theory have large uncertainty
c/bvery different
9
Heavy Quark Elliptic flowRAA 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)
orLonger path lengthMore energy loss
Shorter path lengthLess energy loss
x
y
ϕ, azithmual
dL
d
d E d
dn
d
Path length dependenceof energy loss generates v2
Radiative Energy Loss:
E L
E L2
E L3
Collision Energy Loss:
ADS/CFT Energy Loss:
The path-length-dependence sensitive to different mechanisms:
smaller v2
larger v2
10
Results and model comparison
Measured NPE v2
• charm/bottom combined• very statistically limited at higher pT
• 0-60% centrality
This analysis 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 necessarilyTo identify path-length-dependenceneed more statistics to reach high pT
u
cD0
K
e
11
Conic Emission or V3 Initial Geometry
pTtrig = 2.5-4.0 GeV/c; pT
asso = 1.0-2.5 GeV/c
Mark Horner (for STAR Collaboration):
J. Phys. G: Nucl. Part. Phys. 34 (2007) S995
Au+Au
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 stateUse Heavy Quarks!!
12
NPE-h CorrelationRaw NPE-h
Subtract the modulated v2 background
assume NPE v2=5% assume NPE v2=10% Broadening in the away-side
Energy Loss or else ?
[1 2v2,npe v2,h cos(2)]
v2,npe 0.05 ~ 0.10
13
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 !
Remarks on Parton E Loss
1414
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-baryonsH – ( -L L, uuddss) [ -W W] (ssssss)
strange quark matter
meta-stable Parity/CP odd vacuum bubblesdisoriented chiral condensate……
STAR’s capability has been enhanced greatly with recent upgrades !!
15
Physics Information in Correlation Function
15
-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 interactionsif 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?
16
Correlation Function and Direct Decay Searches Complementary
16
Correlation Function – Depletion of phase space dueto bound state formation -- inclusive, sensitive to total yield
Direct Searches -- depend on branching ratio
If H(uuddss) is a weakly bound state with a bindingenergy ~ 10s MeV as predicted by recentLattice QCD calculations,HL+p+pbranching ratio?
17
• 0-40% Au+Au @ 200 GeV
Set A – Weak N couplingSet B – Medium N couplingSet C – Strong N coupling
Fit A. Ohnishi and T. Furumoto
STAR Preliminary
The scattering length (a0) and the effective range (reff) with no, weak, medium, and strong coupling to -N :
a0 (fm) 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) -2.27 -2.61
Current fit parameters is consistent with non-existence of a strongly bound state of
Search for di-hyperons and study hyperon-hyperon interactions from correlation measurement
18
0-10 % Au+Au @ 200 GeV
Search the Lpp Channel~ 23 M eventsLcandidates – mass within 4 MeV of PDG valuepp pair – mass below L PDG mass by 5 MeV
19
LL
0-10 % Au+Au @ 200 GeV
Search the Lpp ChannelThe rotational method reproduces the background betterNature is not kind enough to give us ‘H’ particleWe will continue to search for other candidates
20
RHIC – a dedicated QCD Facility Having a great run! Even greater potential for
future discoveries !
pp pA
AA
pppA
AA
Exotic
(spin) (CGC,EMC)
(Deconfinement Phase Transition)
2222
W
X
L
Volcanic mediate pT – Spatter (clumps)
An Equilibrated Partonic System
Use coalescence picture to study partons at the phase boundary
23
Effective Parton Distribution in the QM Drop at Hadronization
Use particle emission to measure parton pT distribution and angular anisotropy (v2) in the dense parton drop !!
WX
L
f
Parton Spectroscopy at RHIC
More theoretical development – He, Fries and Rapp, Phys.Rev. C82 (2010) 034907
24
Features of Partonic Matter
W
X
LCentral Au+Au Collisions at RHIC Bulk Partonic Matter --
1) parton collectivity, multi- parton dynamics coalescence/recombination
2) v2 and pT distributions for effective quarks -- evolution from gluons – constituent quarks
3) Intriguing dynamics of baryon rich matter at low energy
4) Major shift in DOF between 11-39 GeV?!
25
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
26
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?