Baryon Production and Flow Highlights from QM2006

1. Soft and intermediate pT physics highlights from QM2006 Selected topics …… Baryon production Flow Intermediate pT ~ Recombination New data at forward rapidity Freeze-out properties Predictions for LHC HIT 12th December 2006 Bedanga Mohanty

2. Baryon production Low energy SPS results got added at QM2006 We had seen this result Change of shape most pronounced at SPS energies : Peak  dip structure Mid-rapidity net-baryon density decreases rapidly Results from : C. Blume (NA49), B. Mohanty(STAR), I.G. Bearden (BRAHMS)

3. 3He Central Pb+Pb NA49 preliminary Baryon production Helium - supposed to be formed from p + n have a opposite shape (concave) - independent of energy Insight into coalescence mechanism ?

4. Averaged rapidity shift y : Baryon production peripheral central Proton yields : Interplay of baryon production and baryon transport at mid rapidity Degree of stopping similar at AGS and SPS - less at RHIC

5. Conclusion : Baryon production • Change in shape of dN/dy of net baryons occurs around SPS energy (Peak to dip structure) • The nuclei production (coalescence of nucleons) have a dN/dy shape which is independent of collision energy • Proton production is similar for beam energy : 17.3 to 200 GeV. Unique interplay of baryon production and transport • Degree of stopping similar for AGS and SPS. More transparency at RHIC

6. Flow Measurements : collision energy, collision species, particle type, pT, rapidity, centrality This QM : Summary and Future directions for the flow studies Results from : S. Voloshin (STAR), P. Sorensen (STAR), Y. Bai (STAR), G. Wang (STAR), R. Nouicer (PHOBOS), C. Loizides (PHOBOS), A. Taranenko (PHENIX), S. Sanders (BRAHMS)H. Liu (STAR), R. Bhalerao, I. G. Bearden (BRAHMS), D. Hoffman (PHOBOS), A. Tang, S.L. Blyth (STAR), S. Esumi (PHENIX)

7. Elliptic flow : Mass ordering, KE scaling,baryon-meson effect At intermediate pT - may due to particle mass or due to baryon-meson Low pT :Mass ordering Low pT : Scaling when plotted as mT - m0 Scenario qualitatively as expected from hydrodynamics

8. 0-80% Au+Au STAR preliminary Universal scaling holds for different centrality Note  = integrated v2 not eccentricity hydro models eccentricity proportional to int. v2 Is it really true ? Elliptic flow : Quark number and universal scaling Universal scaling observed when data presented normalized to quark content

9. PHOBOS claims collision geometry controls the dynamical evolution of heavy Ion collisions - v2 what about v1 ? Elliptic flow : Driven by collision geometry

10. Directed flow : depends on beam energy v1 depends on energy, not on system size.

11. Substantial non-photonic electron v2 observed • expected D meson v2 from non-photonic electron v2 Elliptic flow : D-mesons and thermalization ? Nbinary scaling indicates charm production at initial stage of the collisions

12. AuAu Central charm hadron AuAu Central strangeness hadron AuAu Central , K, p SQM06, Yifei Zhang Charm collectivity : thermalization ? Peter Braun-Munzinger Shinchi Esumi Model dependent (Blast Wave) analysis of J/  and non-photonic electrons (from semi-leptonic decays of mesons having charm quarks) spectra consistent with small transverse radial flow and larger freeze-out temperature

13. Star Preliminary Flow : Degree of thermalization v4 /v22 a detailed probe of ideal hydro behavior and related to the degree of thermalization! Large systematic uncertainty (from non-flow) difficult to conclude about thermalization • Scaled flow values allow constraints for several transport coefficients.

14. Elliptic flow : Situation at SPS ? Scaling at low pT not so prominent when plotted as mT - m0 pT reach may be not sufficient to see the quark number scaling SPS way below hydro-dynamical results. RHIC is in that regime V2 ~ dN/dy

15. Seem to understand this as v2 ~ dN/dy See similar thing for v1 and v4 also… Flow : Longitudinal scaling We observed this for multiplicity

16. Elliptic flow : next steps (Theory/phenomenology) Scaled flow values allow constraints for several transport coefficients Attempts are being made to study properties of the matter formed in heavy ion collisions

17. Elliptic flow : next steps (experimental) All the previous results we saw are average value which varies e-by-e by 35-40% Most of this variation is understood in terms of e-by-e variation in initial event shape

18. Elliptic flow : next steps - how to take care of effect of initial geometry Same impact parameter - shapes can be different at participant level

19. From the experimental data Future directions Conclusion : Flow • At low pT mass ordering of v2 values observed and at intermediate pT ordering by quark content (baryon-meson) • Universal scaling observed across pT, centrality, ion species and particle type - when data presented as a function of v2/n* Vs. mT-m0/n • v2 is driven by collision geometry and v1 by beam energy • Longitudinal scaling observed for all components of measured flow • Time to draw conclusions about property of the medium from the experimental measurements • Understand the event-by-event variation in flow values • How to calculate the eccentricity • Experimental work needed on D-meson flow and v4/v22 to address the issue of thermalization • Lee-Yang Zeroes method is less biased by non-flow correlation. Nucl. Phy. A 727 (2003) 373-426

20. Recombination Since shower partons make insignificant contribution to ,  production for pT<8 GeV/c, no jets are involved. Predict: no associated particles giving rise to peaks in , near-side or away-side. Thermal partons are uncorrelated, so all associated particles are in the background. V. Greco, C.M. Ko and I. Vitev, PRC 71 (2005) 041901 Specific Energy dependence p/ (62.4 GeV) > p/ (200 GeV) Results from :B. Mohanty(STAR), S. Blyth (STAR), J. Bielcikova (STAR), C. Blume(NA49), L.Ruan (STAR) R. Hwa and C. B. yang

21. V. Greco et al PRC 72 (2005) 041901 R.J. Fries et al PRC 68 (2003) 044902 I. Vitev et al PRC 65 (2002) 04902 Lack of quantitative agreement with models Qualitative agreement with coalescence prediction p/+(62.4) > p/+ (200) p/-(62.4) < p/- (200) Recombination : Baryon/Meson ratio

22. The shape of the ratios across 17-200 GeV energies around intermediate pT are similar. Can this feature be consistent with recombination picture ? Recombination : Baryon/Meson ratio

23. Recombination : Correlation Correlation observed - prominent peak at near side No dependence on strange quark content Does that mean recombination mechanism has failed ?

24. Recombination failed ? - Not yet - there are new ideas J. Putschke M. van Leeuwen Phantom jet Rudi Hwa ….. STAR At face value the data falsify the prediction and discredits RM. I now explain why the prediction was wrong and how the data above can be understood. Yang’s talk tomorrow is still right. Recombination still works, but we need a new idea.

25. Baryon to meson ratios Azimuthal correlations Conclusion : Recombination • Initially data on Omega-hadron correlation presented at QM2006 seemed to falsify the recombination picture • Subsequent discussions at QM2006 - led to the need for more careful understanding of the data from both theoretical and experimental side. • Data needs to be presented after taking care of the effect due to extended correlation structure in eta - “ridge” • Some of the features are qualitatively consistent with recombination picture • Lack of quantitative agreement • Similar shape of the ratios across beam energy 17.3 to 200 GeV may not be consistent within the current recombination framework

26. What changes? What doesn’t? New results from forward rapidity Results from : I. G. Bearden (BRAHMS), C. Nygaard (BRAHMS), S. J. Sanders (BRAHMS), T. M. Larsen (BRAHMS), J. H. Lee (BRAHMS), L. Molnar (STAR)

27. RdAu vs eta We had seen this : RdAu is suppressed as we go to forward rapidity What about RAA ?

28. Inclusive charged hadron RAA similar Inclusive charged hadron RAA similar at mid and forward rapidity

29. Identified particle RAA, 200GeV Au+Au y=3.1 y=1 y=0 pions kaons protons Identified RAA similar at mid and forward rapidity

30. V2 Identified particles 200GeV Au+Au  ≈3 =0 K p v2(pT) similar at forward and mid rapidity Remember integrated v2 (shown by PHOBOS) changes with rapidity

31. How about K/ vs. pbar/p? Chemistry changes with rapidity at RHIC. Forward rapidity at RHIC ~ mid rapidity at SPS

32. How about correlation : Forward and mid-rapidity Trigger: 3<pTtrig<4 GeV/c, Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pTassoc< 3 GeV/c pp MB dAu MB • Away side in dAu: • similar between forward • and mid-rapidity • Away side in pp:broader at • forward than mid-rapidity

33. Compare correlation in Au+Au : Forward and mid-rapidity AuAu 60-80% Trigger: 3<pTtrig<4 GeV/c, Associated: FTPC: 0.2<pTassoc< 2 GeV/c, TPC: 0.2<pTassoc< 3 GeV/c AuAu 0-10% AuAu 0-5% • Away-side correlations are very similar! • Energy loss picture is the same for mid- and forward rapidities?

34. What changes? dN/dy pbar/p Chemistry V2 (integral) Initial state (RdAu) What doesn’t? Suppression (RAA) V2 (pt) Away-side azimuthal Correlation Conclusion : At forward rapidity

35. Conditions close to kinetic freeze-out STAR Preliminary STAR Preliminary Smooth evolution of Freeze-out parameters with dNch/d Seems dNch/dy finally matters or these are not the correct observable to study the dynamics Results from : L. Ruan (STAR) A. Irodanova (STAR), D.Das (STAR)

36. Chemical Freeze-out conditions Kp thermal fit STAR Preliminary Min-Bias 10% central 5% central Cu+Cu @ 200 GeV Cu+Cu @ 62.4 GeV Tch is fairly constant with dNch/d but s for Cu+Cu system seems bit higher

37. LHC predictions : Multiplicity AGS dN/dy SPS RHIC 62 “net”proton RHIC 200 LHC 5500 Fully transparent collisions ? Extrapolation for Rapidity loss - similar values at LHC as for 200 GeV Net baryons Multiplicity Results from :U. Wiedemann, J. Cleymans

38. LHC predictions : Freeze-out conditions Chemical Freeze-out temperature : similar to RHIC Baryon chemical potential ~ 1 MeV

39. LHC predictions : Flow Based on simple extrapolation : v2 ~ 0.08

40. dN/dy ~ 1100 - 1600 at mid-rapidity Rapidity loss ~ 2 - 2.5 units Tch ~ 166 MeV at mid-rapidity B ~ 1 MeV at mid-rapidity v2 ~ 0.08 at mid-rapidity Conclusion : LHC predictions Thanks for your attention!