Selected results from the STAR experiment

Selected results from the STAR experiment
Petr Chaloupka for the STAR collaboration Czech Technical University in Prague LOGO fjfi

Outline Introduction RHIC, STAR properties of QCD matter
RHIC Beam Energy Scan selected results Heavy Flavor production open charm quarkonia STAR near term upgrades Anti-He4 at RHIC Conclusions Dodelat podle realneho obsahu

Properties of nuclear matter
Quantum chromodynamics (QCD) fundamental description of strong interaction extensively tested in the perturbative regime little is known about soft regime and emergent phenomena Analogy with solid state physics QED – fundamental theory Rich, dynamically generated, set of phenomena Example: water Cilem fyziky tezkych iontu je zkoumat stavy jaderne hmoty, jejiz chovani je popsano na fundamentalni kvantovou chromodynamikou, za extremnich podminek jako ve vysoka teplota a tlak. Narizdil od bezne hmoty za podminke blizky tomu, jak je zname na Zemi, kterou popisuje QED a jejiz vlasnoti jsou povetsinou dobre znamy, se o chovani jaderne materie rezimech, ktere nelze popsat pomoci perturbativni QCD, predevsim pak o kolektivnich hmonocasticovych jevech vi jen malo. Cilem takoveho vyzkumu je vyjadrena napriklad pak znalost fazoveho diagramu jaderne hmoty tak jej napriklad zname pro vodu --. U jadere hmoty jsouvsak vlastnosti fazoveho digramu odvozeny predevsim z teoretickych predstav.. 15 phase, 16 triple points, 2 critical points

Asymptotic freedom in QCD
1973 Gross, Wilczek, Politzer

Quark-gluon plasma Prediction of deconfined state of matter with partonic degrees of freedom - “Quark Gluon Plasma” believed to exist shortly after Big Bang

QCD phase diagram Jiny obrazek
Cilem fyziky tezkych iontu je zkoumat stavy jaderne hmoty, jejiz chovani je popsano na fundamentalni kvantovou chromodynamikou, za extremnich podminek jako ve vysoka teplota a tlak. Narizdil od bezne hmoty za podminke blizky tomu, jak je zname na Zemi, kterou popisuje QED a jejiz vlasnoti jsou povetsinou dobre znamy, se o chovani jaderne materie rezimech, ktere nelze popsat pomoci perturbativni QCD, predevsim pak o kolektivnich hmonocasticovych jevech vi jen malo. Cilem takoveho vyzkumu je vyjadrena napriklad pak znalost fazoveho diagramu jaderne hmoty tak jej napriklad zname pro vodu --. U jadere hmoty jsouvsak vlastnosti fazoveho digramu odvozeny predevsim z teoretickych predstav..

QCD phase diagram General idea:
Collide nuclei at high energy to create suitable conditions for “melting” matter into the QGP Jiny obrazek Cilem fyziky tezkych iontu je zkoumat stavy jaderne hmoty, jejiz chovani je popsano na fundamentalni kvantovou chromodynamikou, za extremnich podminek jako ve vysoka teplota a tlak. Narizdil od bezne hmoty za podminke blizky tomu, jak je zname na Zemi, kterou popisuje QED a jejiz vlasnoti jsou povetsinou dobre znamy, se o chovani jaderne materie rezimech, ktere nelze popsat pomoci perturbativni QCD, predevsim pak o kolektivnich hmonocasticovych jevech vi jen malo. Cilem takoveho vyzkumu je vyjadrena napriklad pak znalost fazoveho diagramu jaderne hmoty tak jej napriklad zname pro vodu --. U jadere hmoty jsouvsak vlastnosti fazoveho digramu odvozeny predevsim z teoretickych predstav..

Phase transition Lattice QCD calculations: critical energy density
predict smooth cross-over at large T and mB=0. at high T reaching 80 % of non- interacting gas limit remaining interaction- change of initial expectation of perfect gas to (strongly) interacting liquid (sQGP) 1978 – Shuryak coined “Quark gluon plasma” F. Karsch, et al. Nucl. Phys. B605 (2001) 579

Collision evolution Chemical freeze-out (Tch) inelastic collisions cease Kinetic freeze-out (Tfo < Tch) elastic collisions cease

Relativistic Heavy Ion Collider
1.2km PHENIX STAR

STAR experiment

TPC and TOF Time Projection Chamber (TPC): charged particle tracking
2p coverage in |h|<1.3 dE/dx PID: p /K separation up to pT ~ 0.6 GeV/c Time Of Flight (TOF): Timing resolution <100ps 1/b PID TOF + TPC : p /K: pT ~ 1.6 GeV/c and proton pT~ 3.0 GeV/c p K 

Collision geometry Number of participants (Npart):
v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid Number of participants (Npart): number of incoming nucleons in the overlap region Number of binary collisions (Nbin or Ncoll): number of equivalent inelastic nucleon-nucleon collisions Derived from multiplicity information and a simple version of Glauber theory (by now well under control)

Elliptic flow initial spacial anisotropy
interactions and time evolution final momentum anisotropy sensitive to thermalization, EOS and early pressure v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid time evolution

Elliptic flow v2 – close to hydro limit compared to SPS strange flows
STAR, PRL (2003) b ≈ 4 fm b ≈ 6.5 fm b ≈ 10 fm v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid

Elliptic flow at RHIC Large v2 compared to SPS
Fine structure” v2(pT) for different mass particles v2/epsilo – sensitive test v podstate final vs initial eccentricity v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction flui Nucl.Phys. A757 (2005) Includes strange particles Close to ideal hydro predictions

Partonic collectivity
Is v2 generated on hadronic or partonic level? Precision measurements on identified particle v2 from high statistics Au+Au 200 GeV. 0-30%: baryon-meson grouping / NCQ scaling holds. 30-80%: Multi-strange hadron v2 deviate from NCQ scaling at mT-m0>1 GeV/c2. Precision identified particle v2 data provide constraints to study the sQGP properties. v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid STAR: PRL 95, (2005) PHENIX: PRL 98, (2007)

Partonic collectivity
Is v2 generated on hadronic or partonic level? Scaling by number of constituent quarks Precision measurements on identified particle v2 from high statistics Au+Au 200 GeV. 0-30%: baryon-meson grouping / NCQ scaling holds. 30-80%: Multi-strange hadron v2 deviate from NCQ scaling at mT-m0>1 GeV/c2. Precision identified particle v2 data provide constraints to study the sQGP properties. v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid STAR: PRL 95, (2005) PHENIX: PRL 98, (2007)

V2 from Au+Au 200GeV High precision result from 200 GeV for Au+Au
including strange and multistrange particles central collision – clear baryon/meson splitting at medium pT key role of f – heavy meson partonic collectivity confirmation flow of heavy quarks? (charm, bottom)- check of thermalization Precision measurements on identified particle v2 from high statistics Au+Au 200 GeV. 0-30%: baryon-meson grouping / NCQ scaling holds. 30-80%: Multi-strange hadron v2 deviate from NCQ scaling at mT-m0>1 GeV/c2. Precision identified particle v2 data provide constraints to study the sQGP properties. v2 – close to hydro limit compared to SPS strange flows partonic flow phi flow patonic collectivity ?heavy quarks? hight pt-supression R_AA , jety, ridge ?heavy flavor sQGP – from gas to strongly iteraction fluid Xin Dong, QM2012

Hight pT probes Study interaction of created matter with passing particle high pT partons created at initial stage - pQCD expected traversing particle energy loss Raa jety observed strong supressioin

Hight pT probes Study interaction of created matter with passing particle high pT partons created at initial stage - pQCD suppression of high momentum particles – jet quenching control over cold matter effects via d+Au expected traversing particle energy loss Raa jety observed strong supressioin

Hight pT probes finding jet in this ? … hard
Study interaction of created matter with passing particle high pT partons created at initial stage - pQCD suppression of high momentum particles – jet quenching control over cold matter effects via d+Au expected traversing particle energy loss Raa jety observed strong supressioin finding jet in this ? … hard

Nuclear modification factor
comparing particle production to p+p 𝑅 AA ( 𝑝 𝑇 = Yield AA ( 𝑝 𝑇 〈𝑁𝑏𝑖𝑛〉 AA Yield pp ( 𝑝 𝑇 Average number of p-p collision in A-A collision Region of interest: pT & 5 GeV No effect: R=1 at high pT A+A similar to p+p superposition Suppresion: R<1 at high pT expected traversing particle energy loss Raa jety observed strong supressioin

RAA in Au+Au 200GeV observed RAA at RHIC:
no suppression in peripheral collisions 𝑅 AA ( 𝑝 𝑇 = Yield AA ( 𝑝 𝑇 〈𝑁𝑏𝑖𝑛〉 AA Yield pp ( 𝑝 𝑇 collision geometry: expected traversing particle energy loss Raa jety observed strong supressioin Phys.Rev.Lett.91:172302,2003

RAA in Au+Au 200GeV observed RAA at RHIC:
no suppression in peripheral collisions large suppression in central collision - factor ~ 5 𝑅 AA ( 𝑝 𝑇 = Yield AA ( 𝑝 𝑇 〈𝑁𝑏𝑖𝑛〉 AA Yield pp ( 𝑝 𝑇 collision geometry: expected traversing particle energy loss Raa jety observed strong supressioin Phys.Rev.Lett.91:172302,2003

Dihadron correlations
Different way of looking at jet quenching angular correlation between leading and associated hadron trigger particle trigger: < pT(trig) < 6 GeV associated: 2 < pT < pT(trig) associated particle expected traversing particle energy loss Raa jety observed strong supressioin recent v2 of jets STAR, PRL 90(2003) Azimuthal distribution of hadrons with pT > 2 GeV/c relative to trigger hadron with pTtrig > 4 GeV/c (background subtracted). Data are from p+p, central d+Au and central Au+Au collisions.

Dihadron correlations
Different way of looking at jet quenching angular correlation between leading and associated hadron trigger particle trigger: < pT(trig) < 6 GeV associated: 2 < pT < pT(trig) Disappearance of awayside correlation in Au+Au Partner in hard scatter is absorbed in the dense medium expected traversing particle energy loss Raa jety observed strong supressioin recent v2 of jets STAR, PRL 90(2003) Azimuthal distribution of hadrons with pT > 2 GeV/c relative to trigger hadron with pTtrig > 4 GeV/c (background subtracted). Data are from p+p, central d+Au and central Au+Au collisions.

Summary: matter at RHIC
Strong elliptic flow Collective flow of created matter Constituent quark number degrees of freedom apparent in scaling laws of elliptic flow Jet quenching Energy loss of high-pT partons traversing the hot and dense matter Particle production through recombination/coalescence Dominates over fragmentation at medium pT Paradigm shift: non-interacting gas => strongly coupled QGP ( sQGP)

RHIC Beam Energy Scan

Beam Energy Scan Main goal Study the QCD phase diagram:
Search for the signals of possible phase boundary Search for the possible QCD critical point arXiv:

STAR – uniform acceptance
MRPC ToF Barrel BBC PMD EMC Barrel EMC End Cap TPC HLT FTPC STAR – uniform acceptance Au+Au 7.7 GeV Au+Au 200 GeV Coverage: 0 < f < 2p |h| < 1.0 Uniform acceptance: All energies and particles p p p p pT (GeV/c) Rapidity

Disappearance of RCP suppression
RCP suppression NOT seen at lower energies! The QGP signature turned off? Relative contribution of soft physics and hard scattering

Evolution of v2 and NCQ scaling
NCQ scaling of v2 is interpreted as a sign of partonic collectivity. STAR Preliminary New feature: Significant difference between baryon-antibaryon v2 at lower energies

NCQ scaling of v2 is interpreted as a sign of partonic collectivity. STAR Preliminary STAR Preliminary New feature: Significant difference between baryon-antibaryon v2 at lower energies No clear baryon/meson grouping for antiparticles at <=11.5 GeV STAR Preliminary

NCQ scaling of v2 is interpreted as a sign of partonic collectivity. STAR Preliminary STAR Preliminary STAR Preliminary New feature: Significant difference between baryon-antibaryon v2 at lower energies No clear baryon/meson grouping for antiparticles at <=11.5 GeV NCQ scaling holds separately for particles and antiparticles. f-meson v2 deviates (~2s) from others for √sNN ≤ 11.5 GeV, more data needed Possible explana?on • • Baryon transport to mid-‐rapidity? ref: J. Dunlop et al., PRC 84, (2011) Hadronic poten=al? ref: J. Xu et al. PRC 85, (2012)

Mapping phase diagram

Strangeness reconstruction
STAR – excellent reconstruction capability PID (TPC+TOF): pion/kaon: pT~1.6 GeV/c, proton pT~3.0 GeV/c Strange hadrons: decay topology & invariant mass

Strange particle spectra
Au+Au 39 GeV K0s L Au+Au 39 GeV X- Au+Au 39 GeV STAR Preliminary STAR Preliminary Extensive strange particle spectra measurements f, K0s: Levy function fit L, X : Boltzmann fit L: feed-down corrected

Chemical freeze-out Particles used: THERMUS Model: p, K, p, L, K0s, X
Tch , μB, μB,and gS Maping µB region from 20 to 400 MeV in the QCD phase diagram. Centrality dependence of freeze-out temperature with baryon chemical potential observed at lower energies. Andronic: NPA 834(2010) 237 Cleymans: PRC 73(2006)

Kinetic freeze-out Particles used: p,K,p Blast Wave: Tkin and <b> E. Schnedermann et al., Phys. Rev. C 48, 2462 (1993) STAR Preliminary Au+Au STAR Preliminary Higher kinetic temperature corresponds to lower value of average flow velocity and vice-versa. All beam energies - the central collisions are characterized by a lower Tkin and larger <b>

Beam Energy Scan Summary
Very successful Beam Energy Scan program versatility of RHIC and STAR combination Possible signatures of “QGP -turn off” at low energies Disappearance of RCP suppression at lower energies. Break down of v2 NCQ scaling between particles and antiparticles. Signatures of critical point / 1st order transition Not part of this talk There are hints, but needs better statistics Mapping of QCD phase diagram covers μB range from MeV Phase Diagram: - Large mB range covered by the STAR in the phase diagram - Centrality dependence of Tch vs. mB observed for the lower energies Phase Boundary: - Proton v1 slope changes sign between 7.7 GeV and 11.5 GeV - Particles-antiparticles v2 difference increases with decreasing √sNN - f-meson v2 deviates from others for √sNN ≤ 11.5 GeV - Dynamical charge correlations: vanish below 11.5 GeV - Rcp > 1 for pT > 2 GeV/c and √sNN ≤ 11.5 GeV Critical Point: - Ratio fluctuations (2nd moment) show monotonic behavior vs. √sNN - Deviation from Poisson observed for higher moments of net-protons BES-II: - Propose higher statistics data below 20 GeV - Fixed target proposal to extend mB coverage up to 800 MeV

Heavy Flavor Production

Heavy flavor physics at STAR
Why to use heavy quarks ( c, b) Masses are only slightly modified by QCD. Sensitive to initial gluon density and gluon distribution. Produced at initial collision stage Sensitive to initial gluon density and gluon distribution at RHIC. produced mostly from gluon fusion Involve different interaction mechanisms from light quarks with the medium gluon bremsstrahlung radiation collisional energy loss collision dissociation Ads/CFT Heavy quarkonia production reveals critical features of the medium. suppression from color screening or gluon scattering enhancement from coalescence

Heavy flavor physics at STAR
Why to use heavy quarks ( c, b) Masses are only slightly modified by QCD. Sensitive to initial gluon density and gluon distribution. Produced at initial collision stage Interact with the medium differently from light quarks. Suppression or enhancement pattern reveals critical features of the medium (temperature) suppression from color screening or gluon scattering enhancement from coalescence Possible Cold Nuclear effects (CNM) light M.Djordjevic PRL 94 (2004) ENERGY LOSS Sensitive to initial gluon density and gluon distribution at RHIC. produced mostly from gluon fusion Involve different interaction mechanisms from light quarks with the medium gluon bremsstrahlung radiation collisional energy loss collision dissociation Ads/CFT Heavy quarkonia production reveals critical features of the medium. suppression from color screening or gluon scattering enhancement from coalescence The probability of finding a gluon with a momentum fraction xis notthe same in a free proton as in a proton inside a nucleus; this “detail” has significant consequences

Open heavy flavor production
Indirect: semi-leptonic decays can be triggered easily (high pT) Higher branching ratio Indirect access to the heavy quark kinematics Mixing contribution from all charm and bottom hadron decays

Open heavy flavor production
Indirect: semi-leptonic decays can be triggered easily (high pT) Higher branching ration Indirect access to the heavy quark kinematics Mixing contribution from all charm and bottom hadron decays Direct reconstruction direct access to heavy quark kinematics hard to trigger smaller branching ratio large combinatorial background (need handle on decay vertex)

D0 and D* pT spectra in p+p
arXiv: Phys. Rev. D 86 (2012) available data from p+p at Ös=200 and 500 GeV D0 yields scaled by Ncc / ND0 = 1 / 0.56 D* yields scaled by Ncc / ND* = 1 / 0.22 FONLL: R. Vogt, priv. c. Both data sets are consistent with FONLL upper limit Test of pQCD calculations Baseline of heavy ion measurements is under control STAR preliminary

D0 yield and RAA in 200 GeV Au+Au

Peripheral collisions no suppression

Peripheral collisions no suppression Mid-peripheral, central suppression at high pT

Peripheral collisions no suppression Mid-peripheral, central suppression at high pT similar to light hadrons enhancement at intermediate pT - radial flow of light quarks coalescence with charm

Charm total cross-section
Extending to the full rapidity: Run2003 d+Au : D0 + e Run2009 p+p: D0 + D* ,Runs 2010, 2011 Au+Au: D0 Run2003 d+Au : D0 + e Run2009 p+p : D0 + D* Run 2010 & 2011 Au+Au: D0 Charm cross-section follows the “world trend”

Non-photonic electrons(NPE)
NPE – proxy to heavy flavor production measure e± spectra from decays of heavy quarks Main source of backgrounds comes from photonic electrons Dalitz decay: p0 → g + e+ + e- (BR: ~1.2%) conversion electrons: g → e+ + e- depends on the material budget Study of non-photonic electrons is a good way to measure production of bottom and charm hadrons via semi-leptonic decays. c →e± +anything(9.6 %) b→e +anything(10.86 %) • Main background in this measurement comes from photonic electrons. → Dalitz decay: π0 → γ+e++e- (BR: ~1.2%) → Gamma conversions: γ → e++e- (Conversion prob.: 7/9*Radiation Length)

NPE in 200GeV Au+Au Strong suppression at high pT.
comparable to suppression of hadrons. Mixing of bottom/charm contributions . Cannot be explained by radative energy loss only. RAA uncertainty is dominated by p+p. will improve with large statistics data Study of non-photonic electrons is a good way to measure production of bottom and charm hadrons via semi-leptonic decays. c →e± +anything(9.6 %) b→e +anything(10.86 %) • Main background in this measurement comes from photonic electrons. → Dalitz decay: π0 → γ+e++e- (BR: ~1.2%) → Gamma conversions: γ → e++e- (Conversion prob.: 7/9*Radiation Length)

Charm flow Finite v2 at low pT is an indication of strong charm- medium interaction. Consistent results from NPE and D0 Increase of v2 at high pT possibly due to jet correlation and pathlength dependence of energy loss.

Quarkonia production Charmonia: J/y, y', cc Bottomia: (1S,2S,3S), cb
Expect a suppression of quarkonia in a QGP [T.Matsui and H. Satz, Phys Lett. B 178, 416 (1986).] color screening of heavy quark pair potential unique probe of deconfined medium Sequential melting of different states melting depends on binding energy and T C provides a thermometer of QGP [A .Mocsy, Eur. Phys. J. C61, (2009)]

Does J/y flow ? J/y from recombination of thermalized charm quarks is expected to acquire flow v2 consistent with non-flow for pT > 2GeV/c disfavors production by coalescence from thermalized quarks. arXiv:

 measurement  considered cleaner probe
negligible absorption and regeneration p+p year dedicated Upsilon trigger Au+Au year 2010 – three centrality bins (1S+2S+3S) suppression observed, increasing with centrality Consistent with prediction from a model requiring strong 2S and complete 3S suppression.

Heavy flavor summary p+p reference data Open charm Quarkonia
FONLL QCD describes the data rather well Open charm Charm flows significant v2 for NPE, D0 flow Early freeze-out/smaller radial flow than light hadrons Significant suppression of NPE and D0 at high pT Quarkonia From J/y – coalescence dominance is disfavored a high pT Upsilon suppression Consistent with full S3 and strong S2 melting NLO CS+CO and CEM models describe J/ψ pT spectrum in p+p ➡ J/ψ polarization in p+p collisions consistent with NLO+ CSM and COM models predictions, and with no polarization ➡ B-hadron feed-down contribution 10-25% at 4 < pT < 12 GeV/c in p+p ➡ J/ψ RdAu consistent with the model using EPS09+ σabsJ/ψ (3 mb - obtained for a fit to the data) ➡ J/ψ suppression in Au+Au increases with centrality and decreases with pT - at high pT suppression for central collisions ➡ J/ψ v2 measurement disfavors the case when J/ψ is produced dominantly by coalescence from thermalized (anti-)charm quarks for pT > 2 GeV/c

STAR near term upgrades

Heavy flavor tracker (HFT)
SSD IST PXL Inner Field Cage FGT Outer Field Cage TPC Volume Heavy Flavor Tracker (HFT) - Prototype Year 2013 and complete run in Year 2014. NPE RAA in central Au+Au collisions shows similar suppression as that of light spectra. Precise calculation of charm and bottom contribution to the NPE is crucial to interpret these results. HFT will allow measurement of B → e spectrum separately (Current method via NPE-hadron correlation has large systematics uncertainties) PIXEL two layers 18.4x18.4 m pixel pitch 10 sector, delivering ultimate pointing resolution that allows for direct topological identification of charm. new monolithic active pixel sensors (MAPS) technology SSD existing single layer detector, double side strips (electronic upgrade) IST one layer of silicon strips along beam direction, guiding tracks from the SSD through PIXEL detector. - proven strip technology Solenoid EAST WEST 68

Outlook for D0 v2 and RCP Assuming D0 Rcp distribution as charged hadron. 500M Au+Au m.b. events at 200 GeV. Direct measurement of open-charm RCP - charm energy loss in QCD matter Direct measurement of open-charm v2 - medium thermalization degree Subtraction of charm component from NPE - study bottom energy loss 69

Muon Telescope Detector

Muon Telescope Detector
MTD will allow detection of di-muon pairs from QGP thermal radiation, quarkonia, light vector mesons, resonances in QGP, and Drell-Yan production single muons from the semi- leptonic decays of heavy flavor hadrons advantages over electrons: no  conversion, much less Dalitz decay contribution trigger capability for low to high pT J/ in central Au+Au collisions excellent mass resolution, separate different Upsilon states L. Ruan et al., Journal of Physics G: Nucl. Part. Phys. 36 (2009) Advantages for open heavy flavor measurements: No gamma conversion and much less Dalitz decay contribution → very low photonic background. High muon efficiency. Muon to pion (hadron) ratio enhancement by factor ( ) → less hadron contamination. Muon correlation could help distinguish heavy flavor production from initial lepton pair production. No bremsstrahlung for muon-muon. 43% in run 2013, and complete in run 2014.

Discovery of anti-He4 at RHIC

RHIC as an anti-matter machine

anti-He4 identification in TPC
2007 2010 Level 3 trigger - tagging of events with tracks of |Z| = 2. In total one billion AuAu events sampled. dE/dx overlap at higher momentum, TOF information is needed

PID from TOF+TPC 18 counts in total 15 from 200 GeV AuAu in 2010
background ~ 1.4 probability of misidentification ~ significance > 6 2 from 200 GeV AuAu in 2007 1 from 62 GeV AuAu in 2010

anti-He4 yield Relativistic Heavy Ion collisions : High antibaryon density High temperature Favorable environment for both production mechanisms. Exponential trend predicted by both models Production rate reduces by a factor of 1.6x103 (1.1x103) for each additional antinucleon (nucleon) added to the antinucleus (nucleus). Next stable are anti-6Li and anti-6He ( suppression ~ 10-6). anti-4He may remain the heaviest stable antimatter in the foreseeable future.

anti-He4 yield Relativistic Heavy Ion collisions : High antibaryon density High temperature Favorable environment for both production mechanisms. Exponential trend predicted by both models Point of reference for various searches for new phenomena in the cosmos. The production rate of antihelium4 in nuclear collisions is consistent with thermodynamic and coalescent nucleosynthesis models. If anti-a in the cosmos were from coalescence, the ratio of anti-a/a would be With a sensitivity of 10-9, even a single anti-a count seen by the AMS experiment would be a strong evidence of anti-star.

Conclusions STAY TUNED.... Matter at the highest collision energy
strongly interacting almost perfect liquid - sQGP collective behavior with partonic degrees of freedom Successful completion of RHIC Beam Energy Scan observed signal of the onset of deconfinement, ongoing search for 1st order phase transition and critical point Heavy flavor program rich collection of results and more will come with planned upgrades STAR has entered the era of precision QCD measurements – lots of interesting results coming. STAY TUNED....

Backup slides

Beam Energy Scan II increased luminosity ~ 10 times
BES II will focus on the most interesting regions of the phase diagram Electron cooling is key to the feasibility of this program; will provide increased luminosity ~ 10 times Proposal BES-II (Years ): √sNN (GeV) μB (MeV) Requested Events(106) Au+Au 19.6 206 150 Au+Au 15 256 Au+Au 11.5 316 50 Au+Au 7.7 420 70 U+U: ~20 ~200 100

Fixed target proposal

D0 and D* in p+p 200GeV

D0 in 200GeV Au+Au Combining data from Run2010 & 2011.
Total: ~800 M Min.Bias events Significant signals are observed In collisions of all centralities

D0 in 200GeV Au+Au Combining data from 2010 & 2011.
Total: ~800 M Min.Bias events Significant signals are observed In collisions of all centralities possible to split into 3 centrality with 7 pT bins

peripheral collisions – no suppression mid-peripheral, central suppression at high pT enhancement at intermediate pT ? early freeze-out and/or less flow then light quarks

Charm cross-section Total charm cross-section at midrapidity:
Run2003 d+Au : D0 + e Run2009 p+p: D0 + D* ,Runs 2010, 2011 Au+Au: D0 Charm cross-section follows Nbin – scaling production dominated by initial hard scatterings.

NPE in 200GeV Au+Au NPE spectrum in central and semi-central collisions in Au+Au at 200GeV. New measurement of with a highly improved result at high pT . Study of non-photonic electrons is a good way to measure production of bottom and charm hadrons via semi-leptonic decays. c →e± +anything(9.6 %) b→e +anything(10.86 %) • Main background in this measurement comes from photonic electrons. → Dalitz decay: π0 → γ+e++e- (BR: ~1.2%) → Gamma conversions: γ → e++e- (Conversion prob.: 7/9*Radiation Length)

NPE in 200GeV Au+Au Strong suppression at high pT, increasing with pT. No difference with hadron suppression at high pT observed within the errors. RAA uncertainty is dominated by p+p. Should be improved with Run large statistics data Mixing of bottom/charm contributions Cannot be explained by radative energy loss only Study of non-photonic electrons is a good way to measure production of bottom and charm hadrons via semi-leptonic decays. c →e± +anything(9.6 %) b→e +anything(10.86 %) • Main background in this measurement comes from photonic electrons. → Dalitz decay: π0 → γ+e++e- (BR: ~1.2%) → Gamma conversions: γ → e++e- (Conversion prob.: 7/9*Radiation Length) DGLV: Djordjevic, PLB632, 81 (2006) CUJET: Buzzatti, arXiv: T-Matrix: Van Hees et al., PRL100,192301(2008). Coll. Dissoc. R. Sharma et al., PRC 80, (2009). Ads/CFT: W. Horowitz Ph.D thesis.

J/y production in p+p 200GeV
Color singlet model (NNLO*CS): [P. Artoisenet et al., PRL. 101, (2008)] Include no feeddown from higher mass state. NLO CS+ color octet (CO): [Y.-Q. Ma, et al., Phys. Rev. D84, (2011)] Agree with the data Color Evaporation Model(CEM): [M. Bedjidian et al., hep-ph/ ] Include feeddown from Xc and ψ’ STAR: Phys. Rev. C80, (R) (2009) STAR: JPG 38, (2011) PHENIX: Phys. Rev. D 82, (2010)

J/y in Au+Au at 200GeV STAR pT coverage from 0 to 10 GeV/c
Softer spectra as compared to Blast Wave for lighter hadrons. regeneration at low-pT ? smaller radial flow? suppression increases with collision centrality

J/y RAA in d+Au at 200GeV High statistical uncertainty
Observed cold nuclear matter effects in agreement with Phenix Agrees with prediction including shadowing and nuclear absorption

Selected results from the STAR experiment

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