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

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Outline

1) Parton Energy Loss and Jet-Medium Interaction

2) Heavy Ion Collisions as Exotic Factory Facility

3) Outlook

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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 !

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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

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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

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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

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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

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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

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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

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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!!

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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

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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

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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 !!

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Physics Information in Correlation Function

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-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?

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Correlation Function and Direct Decay Searches Complementary

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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?

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• 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

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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

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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

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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)

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End

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W

X

L

Volcanic mediate pT – Spatter (clumps)

An Equilibrated Partonic System

Use coalescence picture to study partons at the phase boundary

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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

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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?!

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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

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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?

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Nucleus-Nucleus Collisions and Volcanic Eruption

Volcanic high pT -- Strombolian eruption Volcanic mediate pT – Spatter (clumps)

Volcanic low pT – Bulk matter flows