Joint Institute for Nuclear Research

1. Joint Institute for Nuclear Research International Intergovernmental Organization Nuclotron-based Ion Collider fAcility (NICA) at JINR: New Prospect for Heavy Ion Collisions Genis Musulmanbekov, JINR, Dubna For NICA Collaboration

2. Contents • Heavy Ion Collisions (HIC): Motivations • NICA Facility at Dubna • Goals of NICA/MPD Project • Physics and Observables in HIC • MultiPurpose Detector (MPD)

3. Heavy Ion Collisions • ~ 20 years • GSI ELab = 1 – 2 AGeV • Dubna ELab = 1 – 6 AGeV • BNL – AGS ELab = 20 – 158 AGeV • CERN – SPS ELab= 20 – 158 AGeV • BNL – RHIC √s =20 – 200 GeV

4. New Phenomena in HIC Stopping power Collective flows Enhanced yield of multi(strange) baryons Enhanced and nonmonotonic (vs. beam energy) yield of K+ mesons. Broadening of transverse momentum distribution of kaons Broadening of dilepton decay width of rho –mesons. Jet quenching, J/Psi suppression and others

6. Freezout Time Hadron gas Mixed Phase QGM Pre-equilibrium Space Initial nuclei

9. T RHIC,SPS,NICA,FAIR NICA Mixed phase NB

11. Nuclear and Energy Density in central Au+Au collisions

12. High baryonic densities FAIR and NICA s =9GeV J.Cleymans, J.Randrup,2006 Maximal baryonic densities on freeze-out curve!рHigh densities on interaction stage!?

13. Experimental programs CP – critical endpoint OD – onset of deconfinement HDM – hadronic dense matter

14. NICA Facility

15. The main goal of the NICA project is an experimental study of hot and dense nuclear matter and spin physics • These goals are proposed to be reached by: • development of the existing accelerator facility (1st stage of the • NICA accelerator programme: Nuclotron-M subproject) as a • basis for generation of intense beams over atomic mass range • from protons to uranium and light polarized ions; • design and construction of heavy ion collider with maximum • collision energy of sNN = 11 GeV and average luminosity • 1027 cm-2 s-1 (for U92+), and polarized proton beams with energy • s ~ 25 GeV and average luminosity > 1030 cm-2 s-1;

16. Scheme of the NICA compex Injector: 2×109 ions/pulse of 238U32+ at energy 6 MeV/u Booster (30 Tm) 2(3?) single-turn injections, storage of 3.2×109, acceleration up to 50 MeV/u, electron cooling, acceleration up to 400 MeV/u Collider (45 Tm) Storage of 15 bunches  1109 ions per ring at 3.5 GeV/u, electron and/or stochastic cooling Stripping (40%) 238U32+ 238U92+ Nuclotron (45 Tm) injection of one bunch of 1.1×109 ions, acceleration up to 3.5 GeV/u max. Two superconducting collider rings IP-2 IP-1 2х15injection cycles

17. NICA parameters

18. The NICA Project Milestones •Stage 1: years 2007 – 2009 - Upgrate and Development of the Nuclotron facility -Preparation of Technical Design Report of the NICA and MPD -Start prototyping of the MPD and NICA elements •Stage 2: years 2008 – 2012 -Design and Construction of NICA and MPD •Stage 3: years 2010 – 2013 - Assembling •Stage 4: year 2013 - 2014 - Commissioning

19. NICA provides unique possibility for the heavy ion physics program: Heavy ion beams in wide energy range: Possibility to perform atomic mass and centrality scan Few intersection points for detectors with large energy-independent acceptance √s = 4 – 11 GeV 4. High luminosityL~1027 см-2с-1

20. NICA/MPD physics program • Search for • in-medium properties of hadrons in a dense and hot baryonic matter; • Nuclear matterequation of state, • possible signs of deconfinement • chiral symmetry restoration • phase transitionsand • QCD critical endpoint

21. Experimental observables: • Scanning in beam energy and centrality of excitation functions for • Multiplicity and global characteristics of identified hadrons including multi-strange particles • Fluctuations in multiplicity and transverse momenta • Directed and elliptic flows for various indentified hadrons • Particle correlations • Dileptons and photons • Polarization effects in heavy ion collisions • (polarization of strange baryons, azimuthal asymmetries)

22. ♣ • What to measure • Multistrange hyperons.The yields, spectra and collective flows of (multi) strange hyperons are expected to provide information on the early and dense phase of the collision. • Event-by-event fluctuations.The hadron yields and their momenta should be analyzed event-wise in order to search fornonstatistical fluctuationswhich are predicted to occur in the vicinityof the critical endpoint. • HBT correlations.Measurement of short range correlations between hadrons π, K, p, Λ allows one to estimate thespace-time size of a systemformed in nucleus-nucleus interactions. • Penetrating probes.Measurements of dilepton pairs permit to investigate thein-medium spectral functionsof low-mass vector mesons which are expected to be modified due to effects of chiral symmetry restoration in dense and hot matter. • . • Polarization effects.Measurement of (multi)strange baryon polarization, asymmetries, Azimuthal charge asymmetry (CME).

23. Current Experimental and Theoretical Status of Heavy Ion Collision Investigations

24. Strange-to-nonstrange ratios in central collisions. “Horn” Effect (World Data)‏ Figure from arXiv:nucl-ex/0405007v1

25. Excitation functions of particle ratios Transport models: HSD,UrQMD,GiBUU Experimental data: E896, NA49,STAR, PHENIX, BRAHMS Exp. data (particularly a maximum atE~30 AGeV) are not well reproduced within the hadron-string picture => evidence fornonhadronic degrees of freedom E.Bratkovskaya et al.,(2004)

26. Excitation function of particle ratios Munzinger: Simposium on Dense Baryonic Matter, GSI 2009 Thermal Model: rapid saturation of contributions from higher resonances in conjunction with additional pions from the sigma describes horn structure well.

27. Transverse mass spectra of Kaons • Transport models: • HSD 2.0 • UrQMD 2.0 • UrQMD 2.1 (effective heavy resonanceswithmasses2 < M < 3GeVandisotropicdecay) • GiBUU • All transportmodelsfailtoreproducethe T-slopewithoutintroducingspecial „tricks“ whichare, however, inconsistentwithother observables! 3D-fluid hydrodynamical model gives the right slope! Is the matter a parton liquid?

28. Fluctuations: theoretical status Lattice QCD predictions: Fluctuations of thequark number density(susceptibility) at μ_B >0 (C.Allton et al., 2003) χq (quark number density fluctuations) will diverge atthecritical end point Experimental observation: •Baryon number fluctuations • Charge number fluctuations 0

29. Multiplicity Fluctuations Theoretical predictions: 3 – 10 times anhancement NA49 result: Measured scaled variances are close to the Poisson one – close to 1! No sign of increased fluctuations as expected for a freezeout near the critical point of strongly interacting matter was observed.

30. Multiplicity Fluctuations Multiplicityfluctuationswofchargedparticlesas a functionofthenumberofprojectileparticipantsNpartproj :

31. Event-by-event dynamical fluctuations K/π ratio Event mixing for the statistical background estimation:

32. Event-by-event dynamical fluctuations Transverse Momentum Event mixing for the statistical background estimation: , where For the system of independently emitted particles fluctuation Фpt goes to zero (no particle correlations).

33. Collective flow: general considerations z x Y Non central Au+Au collisions : interaction between constituents leads to a pressure gradient => spatial asymmetry is converted to an asymmetry in momentum space => collective flow - directed flow Y Out-of-plane - elliptic flow In-plane V2 > 0 indicates in-plane emission of particles V2 < 0 corresponds to a squeeze-out perpendicular to the reaction plane (out-of-plane emission) X v2 = 7%, v1=0 v2 = 7%, v1=-7% v2 = -7%, v1=0

34. Directed v1 and elliptic v2 flows Small wiggle in v1at midrapidity is not described byHSDandUrQMD Too largeelliptic flow v2at midrapidity fromHSDand UrQMD for all centralities ! Experiment (NA49): breakdown of elliptic v2 flow at midrapidity ! Signature for a first order phase transition? H.Stoecker et al., 2005

35. HBT interferometry Rlong p1 x1 qside p2 x2 qout Rside qlong Rout Two-particle interferometry: p-space separation  space-time separation • HBT: Quantum interference between identical particles 2 C (q)‏ 1 q (GeV/c)‏ Sergey Panitkin

36. In Search of the QGP. Expectations. “Energy density” • One step further: • Hydro calculation of Rischke & Gyulassy expects Rout/Rside ~ 2->4 @ Kt = 350 MeV.

37. Excitation function of the HBT parameters • ~10% Central AuAu(PbPb) events • y ~ 0 • kT0.17 GeV/c • no significant rise in spatio-temporal size of the  emitting source at RHIC • Ro/Rs ~ 1 • Some rise in Rlong Note ~100 GeV gap between SPS and RHIC Where are signs of phase transition?!

38. the puzzle Model Comparison (the puzzle) • Subset of models shown • Broad range of physics scenarios explored • Poor description of HBT data

39. Dileptons • Dileptonsare an ideal probeforvectormesonspectroscopy in thenuclear mediumandforthenucleardynamics ! • Excitationfunctionfordileptonyields • Study ofin-medium effectswithdileptonexperiments: • DLS, SPS (CERES, HELIOS))

40. Broadening of dilepton decay spectra of light resonances arXiv:nucl-th/9803035v2 arXiv:nucl-th/0805.3177v1

41. 5. Dileptons • Clear evidencefor a broadeningofther spectralfunction! • wandf showclearpeaks on an approx. exponentialbackground in mass!

42. In-medium modifications of e+e- and m+m- spectra HSD predictions W. Cassing, Nucl.Phys.A674:249-276,2000.

43. Chiral Magnetic Effect (CMF)

44. Chiral Magnetic Effect • Non-central heavy-ion collisions • Large orbital angular momentum (L) 90o to RP • Strong localized B-field (due to net charge of system) • If system is deconfined, can have strong P-violating domains & different no. of left-& right-hand quarks • Preferential emission of like-sign charged particles along

45. Chiral Magnetic Effect -Strong Parity Violation?

46. The NICA experimental program Observables: Penetrating probes:, , , → e+e- (μ+μ-) Strangeness:K, , , , , global features: collective flow, fluctuations, ..., exotica Systematic investigations: A+A collisions from 8 to 45 (35) AGeV, Z/A=0.5 (0.4) p+A collisions from 8 to 90 GeV p+p collisions from 8 to 90 GeV Detector requirements Large geometrical acceptance (azimuthal symmetry !) good hadron and electron identification excellent vertex resolution high rate capability of detectors, FEE and DAQ Large integrated luminosity: High beam intensity and duty cycle, Available for several month per year

47. MPD general view CentralDetector - CD & two ForwardSpectrometers (optional) – FS-A&FS-B

48. CD dimension

49. MPD scheme 3 stages of putting into operation 2-nd stage IT,EC-subdetectors TOF RPC ZDC 3-d stage F-spectrometers (optional ?) TPC ECal EC Tracker 1-st stage barrel part (TPC, Ecal, TOF) + ZDC, BBC, S-SC, …

50. MPD conceptual design Inner Tracker (IT) - silicon strip detector / micromegas for tracking close to the interaction region. Barrel Tracker (BT) - TPC + Straw (for tagging) for tracking & precise momentum measurement in the region -1 < h < 1 End Cap Tracker (ECT) - Straw (radial) for tracking & p-measurement at | h | > 1 Time of Flight (TOF) - RPC (+ start/stop sys.) to measure Time of Flight for charged particle identification. Electromagnetic Calorimeter (EMC) for p0 reconstruction & electron/positron identification. Beam-Beam Counters (BBC) to define centrality (& interaction point). Zero Degree Calorimeter (ZDC) for centrality definition. MPD basic geometry Acceptance