Results from the beam energy scan at RHIC: Exploring the QCD phase structure in A+A collisions

Results from the beam energy scan at RHIC: Exploring the QCD phase structure in A+A collisions Bedanga Mohanty NaConal InsCtute of Science EducaCon and Research (NISER) Outline: ² Phase diagram of QCD ² TheoreCcal (brief) and Experimental status (BES- I) ² Summary 1

Phase Diagram and Basic InteracCons Phase diagram of Water Electromagnetic interaction Precisely known Phase diagram of strong interactions. Largely still a conjecture arxiv:1111.5475 [hep- ph] 2

Phase Diagram of QCD - TheoreCcally µ B = 0 Spontaneous Z 3 breaking µ B > 0 Chiral symmetry restored Ann. Rev. Nucl. Part. Sci. 53, 163, 2003 K. Rajagopal and F. Wilczek, Handbook of QCD Interplay of the chiral symmetry and the center symmetry. These symmetries are exact for zero and infinite quark masses, respectively. Very rich phase structure unfolds in the phase diagram. 3

Cross- over and Temperature Physical quark masses ConCnuum limit SimulaCons along Lines of Constant Physics m K /m π = 3.689; f K /m π = 1.185 Staggered fermionic accon Nature443:675-678,2006 Nucl. Phys. A 830 (2009) 805c No significant volume dependence At high T and µ Β = 0 is a cross over. Agreement on cross over temperature using chiral condensates. 195 190 185 180 175 170 165 160 155 T c [MeV] Physical m l /m s HISQ/tree Asqtad 150 Combined continuum extrapolation -2 HISQ/tree: quadratic in N 145-2 Asqtad: quadratic in N 140-2 N 135 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 Phys.Rev. D85 (2012) 054503 4

Thermodynamics at µ B = 0 MeV 16 12 arxiv:1407.6387 non-int. limit 0.35 0.30 c s 2 non-int. limit HRG 8 4 T c 3p/T 4 /T 4 3s/4T 3 T [MeV] 0 130 170 210 250 290 330 370 0.25 0.20 0.15 0.10 c HRG [GeV/fm 3 ] 0.1 0.2 0.5 1 2 5 10 40 4 70 60 HRG non-int. limit 3 50 40 2 1 stout ( -3p)/T 4 p/t 4 s/4t 4 HISQ T [MeV] 0 130 170 210 250 290 330 370 30 20 4 /T 4 C v /T 3 10 T [MeV] 0 130 170 210 250 290 330 370 5

JHEP 1208 (2012) 053 Trajectories, EOS at non- Zero µ B JHEP 1104 (2011) 001 Lattice QCD provides Temperature and Baryon density evolution of the system in the QCD phase diagram. 6

Search for CriCcal Point - Theory Numerical QCD calculations at large µ B sign problem Techniques: Reweighting, Taylor expansion & Im. potential µ Real world Heavy quarks QCD critical point DISAPPEARED 0 X crossover 1rst m u,d m s Acta Phys.Polon.Supp. 5 (2012) 825-835 Phys. Rev. D 78, 14503 (2008) PoS LATTICE2013 (2013) 202 JHEP 0404, 50 (2004) Phys.Rev.D 71, 114014 (2005) Issues (not common to all) : lattice spacing, physical quark mass, continuum limit, Volume Theory: still some more work to be done need more CPU 7

QCD Phase Diagram - Theory At µ B = 0 Lattice QCD v Quark hadron Transition Cross-over v Transition temperature ~ 150 MeV (Observable dependent) v Robust continuum limit results: EOS and Thermodynamics At µ B non-zero v Efforts on to draw the transition line large uncertainties v Efforts on to get EOS and thermodynamics v Critical point search progressing positive results indicate CP region below Beam energy 30 GeV 8

QCD Phase Diagram - Experimental ConservaCon in strong interaccons - - Charge - - Baryon number - - Strangeness Vary: T, µ B, µ S, µ Q Vary beam energy to change Temperature & Baryon Chemical Potential Nature 448 (2007) 302 9

(I)2000-2012: RHIC, LHC LHC, RHIC, FAIR 1) sqgp: strongly coupled QGP, η/s =>0, ideal fluid. 2) At μ B =0 smooth cross over. (II)2010-2014: RHIC BESI (20 μ B 400 MeV, 200 s NN 7.7 GeV) 1) s NN 15 GeV, μ B 300 MeV: Hadronic interaccons become dominant. 2) CollecCvity and fluctuacon results hint phase transicon. However, more data are needed to confirm. RHIC BESII and FAIR CBM. (III)2018 and beyond: Collider: RHIC BESII (7.7< s NN < 20 GeV, 450 μ B 300 MeV) Fixed- target: FAIR CBM ( s NN 12 GeV, μ B 300 MeV) 1) High luminosity, new detectors 2) Physics focus:criccal Point, Phase Boundary and Quarkyonic Maser

QCD Phase Structure: Theory- Experiment Cross over QGP CP HRG 1 st Order Partonic Phase Hadronic Phase Cross Over First Order Critical region* 11

Freeze- out Dynamics So far 1 st moments of mulcplicity distribucons were used, now higher moments are being considered. Phys.Rev. C84 (2011) 064911 Phys.Rev.Les. 109 (2012) 192302 Phys.Rev.Les. 111 (2013) 062005 Phys.Rev.Les. 113 (2014) 052301 Phys.Rev.Les. 113 (2014) 072001 12

Cross over at µ B ~ 0 MeV (1/2 ) dn/dy p T dp T 10 5 10 4 10 3 10 2 10 1 10 0 ALICE 0-5% IP-Glasma+MUSIC + + - K + + K - p + p Phys. Rev. Les. 110, 012302 (2013) 10-1 0 0.5 1 1.5 2 2.5 p 0.2 T [GeV] 0.15 v 2 v 3 v 4 v 5 ATLAS 20-30%, EP narrow: /s(t) wide: /s=0.2 v n 2 1/2 0.1 Experimental data indirectly supports cross over transition 0.05 0 0 0.5 1 1.5 2 13 p T [GeV]

Establishing Quark Gluon Phase - I Jet Quenching NCQ Scaling R AA (p T ) = 1 d 2 N AA / dp T dη T AA d 2 σ NN / dp T dη Eur.Phys.J. C72 (2012) 1945 v 2 cos2 = ϕ = p p 2 x 2 x + p p 2 y 2 y 14

Establishing Quark Gluon Phase - II Strangeness Enhancement Quarkonia Suppression Phys.Les. B673 (2009) 183-191 Phys.Rev.Les. 109 (2012) 222301 15

Establishing Quark Gluon Phase - II Strangeness Enhancement Quarkonia Suppression pp/pbe >) part /(dn/dy/<n AA >) part (dn/dy/<n 10 1 10 ALICE - + + - s NN = 2.76 TeV NA57 s NN = 17.3 GeV NA49 1 1 10 100 <N part > Phys.Les. B673 (2009) 183-191 Phys.Rev.Les. 109 (2012) 222301 16

Establishing the Quark Gluon Phase - III - 2 RP ) + cos( 0.6 10 0.4 0.2 0-0.2-0.4-0.6 Charge correlations -3 same opp. ALICE Pb-Pb @ STAR Au-Au @ = 2.76 TeV 0 10 20 30 40 50 60 70 centrality, % s NN s NN (ALICE) same+opp. mean cos( + - 2 ) c HIJING / v 2 {2} = 0.2 TeV CME expectation (same charge [13]) Phys.Rev.Les. 110 (2013) 012301 <cos( 1 + 2-2 TPC )> (x10-2 ) 0.15 0.1 0.05 0.0-0.05 0.3 0.2 0.1 0.0-0.1-0.2-0.3 (1) K S 0 ch - - K S 0 ch + 200GeV 39GeV (2) ch - ( ch + ) - ch + ( ch - ) 200GeV 39GeV STAR Preliminary 80 60 40 20 0 Collision Centrality Charge CorrelaCons disappears: with neutral hadrons 17

QCD Phase Structure: Partonic vs. Hadronic Phys.Rev.Les. 110 (2013) 142301; SN0598 Partonic interac:ons dominant NCQ Scaling, Large φ v 2 & Charge Correlations Two Distinct Regions: > 39 GeV 18 < 11.5 GeV

QCD Phase Structure: Partonic vs. Hadronic Phys.Rev.Les. 110 (2013) 142301; SN0598 0-80% Au+Au Collisions at RHIC 0.06 0.04 (1) s NN = 7.7(GeV) K + p (2) s NN = 11.5(GeV) v 2 /n Q 0.02 0 BESII: -meson v 2 statistical error BESII: -meson v 2 statistical error -0.02 0 0.25 0.5 0.75 1 1.25 0 0.25 0.5 0.75 1 1.25 Transverse Momentum p T /n Q (GeV/c) Partonic interac:ons dominant NCQ Scaling, Large φ v 2 & Charge Correlations Two Distinct Regions: > 39 GeV 19 < 11.5 GeV

QCD Phase structure Quark- Gluon and Hadronic Phases ² At small baryonic chemical potential the QCD transition corresponding to a state of de-confined quarks and gluons takes place at high temperature. ² Models with lattice QCD cross over equation of state explain data. ² For large baryonic chemical potential (> 350 MeV) hadronic interactions dominate. 20

QCD Phase Structure: 11.5 39 GeV Observations consistent with general theoretical expectations from a First Order Phase Transition Phys.Rev.Les. 112 (2014) 162301; SN0598 D.H. Rischke et al. HIP1, 309(1995) H. Stoecker, NPA750, 121(2005) J. Steinheimer et al., arxiv:1402.7236 P. Konchakovski et al., arxiv:1404.276 21

CriCcal Point Observable Necessity: Observable sensitive to correlation length and susceptibilities Challenges: Finite system size effects, ξ < 6 fm Finite time effects, ξ ~ 2-3 fm Observable: < (δn) 2 > ~ ξ 2 < (δn) 3 > ~ ξ 4.5 < (δn) 4 > - 3 < (δn) 2 > 2 ~ ξ 7 S σ ~ χ Β (3) /χ Β (2) κσ 2 χ Β (4) /χ Β (2) Phys.Rev.Les. 107 (2011) 052301 Phys. Rev. Les. 91, 102003 (2003) Phys. Rev. Les. 102, 032301 (2009) Phys. Rev. D 61, 105017 (2000) Phys.Les. B696 (2011) 459 22 Phys.Rev.Les. 105 (2010) 022302

QCD based Model: CP Region and Kurtosis T, GeV t critical point QGP PotenCal Κ 4 0.1 H hadron gas freezeout curve nuclear matter 0 1 µ B, GeV 120 100 80 60 40 20 0 20 0.4 0.2 0.0 0.2 0.4 0.6 t Collisions Energy à increasing Prob. DistribuCon M. Stephanov: Phys.Rev.Les. 107 (2011) 052301 M. Asakawa et al., Phys. Rev. Les. 103 (2009) 262301 J. Deng Poisson à Oscillation à Poisson 23

QCD Phase Structure: Below 39 GeV Phys.Rev.Les. 112 (2014) 032302; SN0598 Net- proton à Net- baryon Phys.Rev. C87 (2013) 041901 Phys.Rev. C86 (2012) 024904 Critical Region: below 27 GeV? Find the Oscillation.BES-II Κ 4 120 100 80 60 40 20 0 20 0.4 0.2 0.0 0.2 0.4 0.6 t 24

QCD Phase Structure: Below 39 GeV arxiv: 1405.4617 Phys. Les. B 724, 51 (2013). Data: Net- proton DistribuCon shape ~ protons Poisson: Net- proton and proton distribucons shows deviacon from Poisson Binomial: Net- proton and proton distribucons deviate at 19.6 Hadron Resonance Gas Model: DeviaCons for net- proton and proton distribucons at 19.6 and 27 GeV. UrQMD: Net- proton and proton distribucons deviate at 19.6 25 and 27 GeV.

QCD Phase Structure: 1 st order Phase TransiCon and CP ² Non-monotonic variations of v 1 slope for net-protons signature of softening of equation of state/1 st Order Phase transition? ² Hints of non-monotonic variation of κσ 2 for netprotons --- Is there an osscilation? BES- II / larger phase space acceptance needed. 29

Phase structure: InteresCng PossibiliCes K. Fukushima @ATHIC 2014 Rept.Prog.Phys. 74 (2011) 014001 CPOD:2013: J. Stroth Quarkyonic phase (Theoretical) à Experimental signature Nucl.Phys. A830 (2009) 709C- 712C (Baryon correlations, Photons)? Nucl. Phys. A 796, 83 (2007 arxiv:1302.1119 30

Summary Theory Experiment 0 Lattice QCD: Solid results at zero µ B Ø Cross over PRL2014 Ø EOS, Transition Temp. PRL2013 Ø QCD Thermodynamics Progress at large µ B PRL2014 Ø CP > µ B = 300 MeV PRL2014 Temperature T/T C 1.5 1 0.5 0 LHC SPS AGS SIS Future Success of BES@RHIC Measure CP Oscillations Increased statistics and phase space in RHIC BES-II/CBM, FAIR / NICA/SHINE Search for a new state of Matter Quarkyonic Phase SHINE/CBM, FAIR/NICA RHIC FAIR/NICA Chemical hadronic phase freeze-out* 0 2 4 6 8 Baryon Chemical Potential µ B /T C 31 quark-gluon plasma (T C = 175 MeV) //models/kurtosis4science/figure/tmu_dl_15july2012.kumac//

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