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 July 23-25, 2012, STAR Regional 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 3 partonichadronic 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 Mostly produced at t=0, and an excellent probe for properties of QCD matter !

p T Scales and Physical Processes R CP Three P T Regions: -- Fragmentation -- multi-parton dynamics (recombination or coalescence or …) -- Hydrodynamics (constituent quarks ? parton dynamics from gluons to constituent quarks? ) 4 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  trig -  hadron Near-Side Away-Side R AA and v 2 Jet-h or NPE-h correlations

6 NPE spectra and R AA R AA ~ 0.3 at p T = 4-6 GeV/c, NPE indeed suppressed ! Most central 5% AuAu collisions NPE spectrum in AuAu from Wenqin Xu’s thesis NPE R AA Scaled NPE in p+p

7 Model comparison Model: heavy quarks collide with light quarks and form hadrons A 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: 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 R AA Bottom versus Charm in the Model M. He, R. J. Fries, R. Rapp, arXiv: Both data and theory have large uncertainty c/b very different

9 Heavy Quark Elliptic flow R AA alone is not sufficient ! More constraints – e.g., differential suppression w.r.t. azimuthal angle -- caused by HQ thermalization (low p T ) and/or different path lengths (high p T ) or Longer path length More energy loss Shorter path length Less energy loss x y ϕ, azithmual Path length dependence of energy loss generates v 2 Radiative Energy Loss: Collision Energy Loss: ADS/CFT Energy Loss: The path-length-dependence sensitive to different mechanisms: smaller v 2 larger v 2

10 Results and model comparison Measured NPE v 2 charm/bottom combined very statistically limited at higher p T 0-60% centrality This analysis Same Model for R AA Model NPE v 2 < Measured NPE v 2 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 p T D0D0

Conic Emission or V 3 Initial Geometry 11 p T trig = GeV/c; p T asso = 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: v 3 initial state Use Heavy Quarks!!

12 NPE-h Correlation Raw NPE-h Subtract the modulated v 2 background assume NPE v 2 =5%assume NPE v 2 =10% Broadening in the away-side Energy Loss or else ?

Parton Energy Loss  Hadron P T 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 R AA and v 2 at high p T !! 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 Remarks on Parton E Loss

14 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 – ( , uuddss) [  ] (ssssss) strange quark matter meta-stable Parity/CP odd vacuum bubbles disoriented chiral condensate …… STAR’s capability has been enhanced greatly with recent upgrades !!

15 Physics Information in Correlation Function 15  Correlation Function: both  s from the primary vertex – if there is a  resonance state -- enhanced peak at resonance and attractive  interactions if there is a bound state H, then two  s near threshold can form H -- depletion of  correlations (WRT a reference?!) (if we can measure p-n correlation, the effect of deuteron formation) both  s from secondary vertices – weak decay product – [  -  ] state?

16 Correlation Function and Direct Decay Searches Complementary 16 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   +p+  branching ratio?

% 200 GeV Set A – Weak  N coupling Set B – Medium  N coupling Set C – Strong  N coupling Fit  A. Ohnishi and T. Furumoto STAR Preliminary  The scattering length (a 0 ) and the effective range (r eff ) with no, weak, medium, and strong coupling to  -N : a 0 (fm) r eff (fm) No coupling weak (Set.A) medium (Set.B) strong (Set.C)  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

% 200 GeV Search the  p  Channel ~ 23 M events  candidates – mass within 4 MeV of PDG value p  pair – mass below  PDG mass by 5 MeV

19  0-10 % 200 GeV Search the  p  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

20 RHIC – a dedicated QCD Facility Having a great run! Even greater potential for future discoveries ! pp pA AA pp pA AA Exotic (spin) (CGC,EMC) (Deconfinement Phase Transition)

21 End

22    Volcanic mediate p T – 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 (v 2 ) in the dense parton drop !!     Parton Spectroscopy at RHIC More theoretical development – He, Fries and Rapp, Phys.Rev. C82 (2010)

Features of Partonic Matter 24    Central Au+Au Collisions at RHIC Bulk Partonic Matter -- 1) parton collectivity, multi- parton dynamics coalescence/recombination 2) v 2 and p T 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 GeV?!

25  /  11.5 GeV also deviates from GeV What is the collision energy where the deviation from partonic dominated matter becomes eminent? data from 19.6 and 27.0 GeV Au+Au collisions -- Perhaps more scan between 11.5 and 19.6 needed

V 2 and R AA are Related Precise value of v 2 at p T > 6, 10 GeV/c ? R AA at pT > 10 GeV/c at RHIC should R AA approach unity at higher p T ? Future measurements will shed more lights on possible physical scenarios for parton energy loss dynamics ! Heavy Quarks will be special -- Lorentz  dependence on parton ELoss on jet-medium interaction near-side vs away-side? 26

27 Nucleus-Nucleus Collisions and Volcanic Eruption Volcanic high p T -- Strombolian eruption Volcanic mediate p T – Spatter (clumps) Volcanic low p T – Bulk matter flows