1. Selected Results from STAR Beam Energy Scan Program Michal Šumbera Nuclear Physics Institute AS CR, Řež/Prague (for the STAR Collaboration) 1 M. Šumbera NPI ASCR

2. 1) Turn-off of sQGP signatures 2) Search for the signals of phase boundary 3) Search for the QCD critical point The RHIC Beam Energy Scan Motivation 2 M. Šumbera http://arxiv.org/abs/1007.2613

3. TPC: Detects Particles in the |  |<1 range , K, p through dE/dx and TOF K 0 s  through invariant mass Coverage: 0 <  < 2  |  | < 1.0 Uniform acceptance: All energies and particles 3

4. Triggering required effort, but was a solvable problem. Geometric acceptance remains the same, track density gets lower. Detector performance generally improves at lower energies. BES-I Data: Central Au+Au at 7.7 GeV in STAR TPC Uncorrected N ch dN evt / (N evt dN ch ) BES Au+Au Data Taking 4 M. Šumbera NPI ASCR

5. STAR TPC - Uniform Acceptance over all RHIC Energies Au+Au at 7.7 GeV Au+Au at 39 GeV Au+Au at 200 GeV  Crucial for all analyses 5

6. Selected Results 6 M. Šumbera STAR publications on BES results Observation of an energy-dependent difference in elliptic flow between particles and antiparticles in relativistic heavy ion collisionsantiparticles in relativistic heavy ion collisions, Phys. Rev. Lett. 110 (2013) 142301 Elliptic flow of identified hadrons in Au+Au collisions at Elliptic flow of identified hadrons in Au+Au collisions at √s NN = 7.7--62.4 GeV,7.7--62.4 GeV Phys. Rev. C 88 (2013) 14902 Inclusive charged hadron elliptic flow in Au + Au collisions atInclusive charged hadron elliptic flow in Au + Au collisions at √s NN = 7.7--62.4 GeV,7.7--62.4 GeV Phys. Rev. C 86 (2012) 54908 Energy Dependence of Moments of Net-proton Multiplicity Distributions at RHIC STAREnergy Dependence of Moments of Net-proton Multiplicity Distributions at RHIC STAR, e-Print: arXiv:1309.5681 [nucl-ex]arXiv:1309.5681 + many conference proceedings…

7. (0-5%/60-80%) Suppression of Charged Hadrons … Suppression of Charged Hadrons … PRL 91, 172302 (2003) 7 M. Šumbera

8. (0-5%/60-80%) STAR Preliminary … and its Disappearance R CP ≥ 1 at lower energies - Cronin effect? R CP ≥ 1 at lower energies - Cronin effect? PRL 91, 172302 (2003) 8 M. Šumbera

9. Enhancement vs. QGP suppression Motivation: Agreement between the simulation and the data at low beam energies and its break down at higher energies could help to find the energy at which QGP becomes dominant.  In HIJING (jet quenching off) R CP at lower energies is enhanced, but there is no quantitative agreement with charged hadron R CP from data.  No suppression at higher energies observed, as expected (quenching was turned off). 9 M. Šumbera S. Horvat (STAR): arXiv: 1303.7260 HIJING 1.35: Gyulassy M. and Wang X. Com. Phys. Com. 83 307(1994)

10. Positive particles STAR Preliminary 10 R CP : Identified Particles  Proton R CP > pion R CP, similar to d+Au at √s NN =200 GeV ⇒ Pions may serve as a better gauge for jet quenching within the p T range available through particle identification.

11.  Antiproton R CP < pion R CP for p T <1GeV/c  Pion R CP suppressed for √s NN ≥39GeV 11 Negative particles STAR Preliminary R CP : Identified Particles

12. 12  meson p T spectra Fit by Levy (straight line) works well STAR Preliminary

13.  K s 0 R CP : (0-5%)/(40-60%)   R CP : (0-10%)/(40-60%) and (0-5%)/(40-60%) for 200GeV 13 R CP :  and K s 0 STAR Preliminary

14. 14  R CP : energy dependence   R CP ≥ 1 at intermediate p T for √s NN ≤ 39GeV

15. M. Šumbera NPI ASCR 15 Strange Quark Dynamics  At i ntermediate p T Ω/  ratios show different behavior for √s NN ≥ 19.6 and √s NN = 11.5 GeV.  Derived strange quark p T distributions show a similar trend. STAR Preliminary Change of particle production mechanism ? Hwa & Yang, Phys. Rev. C 75, 054904 (2007), Phys. Rev. C 78, 034907 (2008).

16. NCQ Scaling Test: particles NCQ Scaling Test: particles 16 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)  Universal trend for most of particles – n cq scaling not broken at low energies  ϕ meson v 2 deviates from other particles in Au+Au@(11.5 & 7.7) GeV: ~ 2σ at the highest p T data point. Needs more data to make clear conclusion. ~ 2σ at the highest p T data point. Needs more data to make clear conclusion. Reduction of v 2 for ϕ meson and absence of n cq scaling  during the evolution the system remains in the hadronic phase [B. Mohanty and N. Xu: J. Phys. G 36, 064022(2009)]

17. NCQ Scaling Test: antiparticles NCQ Scaling Test: antiparticles 17 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)

18. Δv 2 : v 2 (Particles) - v 2 (Antiparticles) Δv 2 : v 2 (Particles) - v 2 (Antiparticles)  The difference between particles and anti-particles is observed. The baryon chemical potential is directly connected to the difference in v 2 between particles and antiparticles.  A linear increase Δv 2 = a × μ B for all particle species for 7.7 GeV ≤ √s NN ≤ 62.4 GeV.  The baryon chemical potential is directly connected to the difference in v 2 between particles and antiparticles. 18 M. Šumbera STAR: PRL 110 (2013) 142301 STAR: Phys.Rev. C88, 014902 (2013)

19. Beam Energy Scan Phase- II 19 M. Šumbera

20. STAR BES Program Summary 206585112 0 420 2.5 57.719.639 775 √s NN (GeV)  B (MeV) QGP properties BES phase-I Test Run Fixed Target BES phase-II Large range of  B in the phase diagram !!! Explore QCD Diagram 20 M. Šumbera

21. Explore QCD Diagram STAR BES Program Summary 206585112 0 420 2.5 57.719.639 775 √s NN (GeV)  B (MeV) QGP properties BES phase-I Test Run Fixed Target BES phase-II Large range of  B in the phase diagram !!! 21 M. Šumbera

22. Is there another way? Can another facility do this faster? Or better? The Alternatives 22 M. Šumbera NPI ASCR

23. Time Line: 2009-2015 Energy Range: √s NN =4.9 - 17.3 GeV  B = 0.560 - 0.230 GeV BES I Runn + Running now, that’s good + Energy range is good - But fixed-target - And light ions Not Ideal S uper P roton S ynchrotron (SPS) 23 M. Šumbera NPI ASCR

24. Nuclotron based Ion Collider fAcility (NICA) Time Line: Not yet funded. Plan is to submit documents by end of 2012. Operations could not begin before 2017 (probably much later) Energy Range: √s NN = 3.9 - 11 GeV for Au+Au;  B = 0.630 - 0.325 GeV. Multi-Purpose Detector (MPD) + Collider, that’s good + High Luminosity expected MPD similar to STAR Maybe as early as 2017 - (But probably later) - Energy is too low! - Will miss the critical point 24 M. Šumbera NPI ASCR

25. F acility for A ntiproton and I on Research (FAIR) Time Line: SIS-100 is funded and will be complete by 2018 SIS-300 will need additional funding (no time estimate) Energy Range: SIS-100: Au+Au @ √s NN =2.9 GeV SIS-300: Au+Au √s NN = 2.7 - 8.2 GeV  B =0.730 - 0.410 GeV Compressed Baryonic Matter (CBM) STS MVD TOF TRD RICH ECAL ++ Very High Interaction Rate - Fixed target geometry - No time estimate for SIS-300 Probably after 2022 - Even with SIS-300, the energy is too low! - Will miss the critical point M. Šumbera NPI ASCR 25

26. SPS NA61 2009 4.9-17.3 100 Hz CP&OD Facilty Exp.: Start: Au+Au Energy: Event Rate: Physics: RHIC BESII STAR 2017 7.7– 19.6+ 100 Hz CP&OD NICA MPD >2017? 2.7 - 11 <10 kHz OD&DHM SIS-300 CBM >2022? 2.7-8.2 <10 MHZ OD&DHM √s NN (GeV) At 8 GeV PHENIX CP = Critical Point OD = Onset of Deconfinement DHM = Dense Hadronic Matter Comparison of Facilities Fixed Target Lighter ion collisions Fixed Target Conclusion: RHIC is the best option M. Šumbera NPI ASCR

27. Fixed Target Proposal 27 M. Šumbera NPI ASCR - Annular 1% gold target inside the STAR beam pipe - 2m away from the center of STAR - Data taking concurrently with collider mode at beginning of each fill

28. Fixed Target Proposal Simulation 28 M. Šumbera NPI ASCR UrQMD simulated Au+Al (beampipe) event ©Chris Flores, UC Davis

29. B. Haag DNP F13 Fixed-Target (Beampipe)Events

30. Event Selection & Kinematics

31. √s NN = 3.0 GeV B. Haag DNP F13 Each set of points is a different rapidity slice; bottom to top: 0.0< y < 0.1 to 1.5< y <1.6 Curves are offset by powers of ten The nucleon- nucleon center-of- mass rapidity slice is indicated in red

32. √s NN = 3.5 GeV B. Haag DNP F13 Each set of points is a different rapidity slice; bottom to top: 0.0< y < 0.1 to 1.5< y <1.6 Curves are offset by powers of ten The nucleon- nucleon center-of- mass rapidity slice is indicated in red

33. √s NN = 4.5 GeV B. Haag DNP F13 Each set of points is a different rapidity slice; bottom to top: 0.0< y < 0.1 to 1.5< y <1.6 Curves are offset by powers of ten The nucleon- nucleon center-of- mass rapidity slice is indicated in red

34. Rapidity Density Distributions 10.26.03B. Haag DNP F13 34 The rapidity density distributions have been measured from target rapidity to the nucleon- nucleon center-of- mass rapidity. The distributions are fit with Gaussians. Error are statistical only dN/dy distributions for Au Like +Al may not peak at zero.

35. Summary  STAR results from BES program covering large  B range provide important constraint on QCD phase diagram: – R CP of unidentified charged hadrons turns-off near 39 GeV. – Identified R CP is qualitatively similar and suggests that pions are less affected by (still unquantified) sources of enhancement. – Particles-antiparticles v 2 difference increases with decreasing √s NN and is directly connected to baryon chemical potential. – Baryon–meson splitting is observed when collisions energy ≥ 19.6 GeV for both particles and the corresponding anti-particles. for both particles and the corresponding anti-particles. –...and many other results not covered in this talk.  Search for the critical point continues: -Proposed BES-II program  Fixed target proposal to extend  B coverage up to 800 MeV 35 M. Šumbera

36. Argonne National Laboratory, Argonne, Illinois 60439 Brookhaven National Laboratory, Upton, New York 11973 University of California, Berkeley, California 94720 University of California, Davis, California 95616 University of California, Los Angeles, California 90095 Universidade Estadual de Campinas, Sao Paulo, Brazil University of Illinois at Chicago, Chicago, Illinois 60607 Creighton University, Omaha, Nebraska 68178 Czech Technical University in Prague, FNSPE, Prague, 115 19, Czech Republic Nuclear Physics Institute AS CR, 250 68 Řež/Prague, Czech Republic University of Frankfurt, Frankfurt, Germany Institute of Physics, Bhubaneswar 751005, India Indian Institute of Technology, Mumbai, India Indiana University, Bloomington, Indiana 47408 Alikhanov Institute for Theoretical and Experimental Physics, Moscow, Russia University of Jammu, Jammu 180001, India Joint Institute for Nuclear Research, Dubna, 141 980, Russia Kent State University, Kent, Ohio 44242 University of Kentucky, Lexington, Kentucky, 40506-0055 Institute of Modern Physics, Lanzhou, China Lawrence Berkeley National Laboratory, Berkeley, California 94720 Massachusetts Institute of Technology, Cambridge, MA Max-Planck-Institut f"ur Physik, Munich, Germany Michigan State University, East Lansing, Michigan 48824 Moscow Engineering Physics Institute, Moscow Russia NIKHEF and Utrecht University, Amsterdam, The Netherlands Ohio State University, Columbus, Ohio 43210 Old Dominion University, Norfolk, VA, 23529 Panjab University, Chandigarh 160014, India Pennsylvania State University, University Park, Pennsylvania 16802 Institute of High Energy Physics, Protvino, Russia Purdue University, West Lafayette, Indiana 47907 Pusan National University, Pusan, Republic of Korea University of Rajasthan, Jaipur 302004, India Rice University, Houston, Texas 77251 Universidade de Sao Paulo, Sao Paulo, Brazil University of Science \& Technology of China, Hefei 230026, China Shandong University, Jinan, Shandong 250100, China Shanghai Institute of Applied Physics, Shanghai 201800, China SUBATECH, Nantes, France Texas A&M University, College Station, Texas 77843 University of Texas, Austin, Texas 78712 University of Houston, Houston, TX, 77204 Tsinghua University, Beijing 100084, China United States Naval Academy, Annapolis, MD 21402 Valparaiso University, Valparaiso, Indiana 46383 Variable Energy Cyclotron Centre, Kolkata 700064, India Warsaw University of Technology, Warsaw, Poland University of Washington, Seattle, Washington 98195 Wayne State University, Detroit, Michigan 48201 Institute of Particle Physics, CCNU (HZNU), Wuhan 430079, China Yale University, New Haven, Connecticut 06520 University of Zagreb, Zagreb, HR-10002, Croatia 36 M. Šumbera

37. 37 M. Šumbera

38. The RHIC Beam Energy Scan Project A landmark of the QCD phase diagram Since the original design of RHIC (1985), running at lower energies has been envisioned RHIC has studied the possibilities of running lower energies with a series of test runs: 19.6 GeV Au+Au in 2001, 22.4 GeV Cu+Cu in 2005, and 9.2 GeV Au+Au in 2008 In 2009 the RHIC PAC approved a proposal to run a series of six energies to search for the critical point and the onset of deconfinement. These energies were run during the 2010 and 2011 running periods. 38 M. Šumbera NPI ASCR

39.  HIJING captures beam energy dependence of spectra.  Jet quenching as modeled in HIJING has a greater effect on higher beam energies.  For AMPT, lower beam energies are better matched by SM off, while SM on better captures the beam energy dependence. ⇒ Physics of hadronization shifts from coalescence to fragmentation? 39 Model summary M. Šumbera

40. NCQ Scaling Quality: particles NCQ Scaling Quality: particles 40 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)

41. NCQ Scaling Quality: antiparticles NCQ Scaling Quality: antiparticles 41 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)

42. Azimuthal Anisotropy  Directed flow v 1 is due to the sideward motion of the particles within the reaction plane. It is sensitive to baryon transport, space-momentum correlations and QGP formation.  Elliptic flow v 2 results from the interaction among produced particles and is directly related to transport coefficients of produced matter. M. Šumbera 42

43. STAR Preliminary v1v1 Directed Flow of p and π p π - 43 STAR Preliminary 10 – 40% STAR Preliminary

44. Directed Flow of p and π: mid-central 44 STAR Preliminary Proton v 1 slope: Proton v 1 slope: changes sign from positive at 7.7 GeV to negative at 11.5 GeV and remains small negative up to √s NN =200GeV. Pion and antiproton v 1 slope: Pion and antiproton v 1 slope: always negative.   For √s NN ≥11.5 GeV contradicts baryon stopping picture predicting opposite slope for protons and pions. Net-proton v 1 slope: Net-proton v 1 slope: shows double sign change. Can not be explained by URQMD model but is qualitatively consistent with a prediction of hydrodynamic model with a first order phase transition *. *)H. Stocker, Nucl. Phys. A 750, 121 (2005). E895: PRL 84, 5488 (2000) NA49: PR C68, 034903 (2003) STAR: NP A904, 357 (2013) STAR: PRL 108, 202301(2012)

45. v 2 (p T ): Transport model comparisons  Purely hadronic system () does not explain relatively large elliptic flow at these energies.  Purely hadronic system (UrQMD) does not explain relatively large elliptic flow at these energies. provides the best description of the data (except of protons and anti- protons @ GeV).  AMPT-SM provides the best description of the data (except of protons and anti- protons @ 7.7 GeV).  In all other cases both and under- predict v 2 (p T ).  In all other cases both AMPT and UrQMD under- predict v 2 (p T ).  Purely hadronic system () does not explain relatively large elliptic flow at these energies.  Purely hadronic system (UrQMD) does not explain relatively large elliptic flow at these energies. provides the best description of the data (except of protons and anti- protons @ GeV).  AMPT-SM provides the best description of the data (except of protons and anti- protons @ 7.7 GeV).  In all other cases both and under- predict v 2 (p T ).  In all other cases both AMPT and UrQMD under- predict v 2 (p T ). 45 M. Šumbera 0-80% central Au+Au UrQMD 2.23: M. Bleicher et al, J. Phys. G 25, 1859 (1999). AMPT 1.11: Z.-W. Lin et al., Phys. Rev. C 72, 064901 (2005). AMPT-SM: string melting version STAR: STAR: Phys.Rev. C88, 014902 (2013)

46. Corresponding anti-particlesParticles v 2 vs. m T -m 0  Baryon–meson splitting is observed when collisions energy ≥ 19.6 GeV for both particles and the corresponding anti-particles for both particles and the corresponding anti-particles  For anti-particles the splitting is almost gone within errors at 11.5 GeV 46 STAR: STAR: Phys.Rev. C88, 014902 (2013) M. Šumbera NPI ASCR

47. NCQ Scaling Test: particles NCQ Scaling Test: particles 47 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)  Universal trend for most of particles – n cq scaling not broken at low energies  ϕ meson v 2 deviates from other particles in Au+Au@(11.5 & 7.7) GeV: ~ 2σ at the highest p T data point. Needs more data to make clear conclusion. ~ 2σ at the highest p T data point. Needs more data to make clear conclusion. Reduction of v 2 for ϕ meson and absence of n cq scaling  during the evolution the system remains in the hadronic phase [B. Mohanty and N. Xu: J. Phys. G 36, 064022(2009)]

48. NCQ Scaling Test: antiparticles NCQ Scaling Test: antiparticles 48 M. Šumbera STAR: STAR: Phys.Rev. C88, 014902 (2013)

49. H.J.Specht, Erice 2012 49 Beam conditions: CERN vs. GSI/FAIR Luminosity at the SPS comparable to that of SIS100/300 No losses of beam quality at lower energies except for emittance growth RP limits at CERN in EHN1, not in (former) NA60 cave < 11 – 35 (45) SPS SIS100/300 beam target interaction intensity thickness rate 2.5×10 6 5×10 5 [λi ][λi ] [Hz] 20% NA60 (2003) new injection scheme 10 8 10% 10 7 10 8 1% 10 6 interaction rate [Hz] 10 5 - 10 7 Energy range: 10 – 158 [AGeV] LHC AA 5×10 4 Pb beams scheduled for the SPS in 2016-2017, 2019-2021 M. Šumbera NPI ASCR

50. How to optimize the physics outcome for the next 10-15 y Proposal: split HADES and CBM at SIS-100 HADES at SIS-100 CBM at SPS Upgrade HADES, optimized for e + e -, to also cope with Au-Au (now Ni-Ni) Modify CBM to be optimal (magnet) for either e + e - or μ + μ - ; role of hadrons? Merge with part of personell of CBM Merge with ‘CERN’ effort towards a NA60 successor experiment Profit from suitable R&D of CBM Profit from suitable R&D of CBM, in particular for Si If SIS-300 would be approved in >2020, one could continue CBM there in >2027 H.J.Specht, Erice 2012 M. Šumbera NPI ASCR 50

51. v 2 (  ) vs. v 2 (p) Mass: proton ~  At low p T, v 2 (  )/v 2 (p) decreases with decreasing beam energies → Indicating less partonic collectivity with decreasing beam energy. STAR Collaboration: arXiv: Phys. Rev. C 88, 014902 (2013) and Phys. Rev. Lett. 110, 142301 (2013). Phys. Rev C 87, 014903 (2013 )