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

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

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

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

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

Measurements : collision energy, collision species, particle type, p T, rapidity, centrality This QM : Summary and Future directions for the flow studies Flow 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)

Elliptic flow : Mass ordering, KE scaling,baryon-meson effect Low p T :Mass ordering Low p T : Scaling when plotted as m T - m 0 Scenario qualitatively as expected from hydrodynamics At intermediate p T - may due to particle mass or due to baryon- meson

Elliptic flow : Quark number and universal scaling Universal scaling observed when data presented normalized to quark content Universal scaling holds for different centrality Note  = integrated v 2 not eccentricity hydro models eccentricity  proportional to int. v 2 Is it really true ? STAR preliminary 0-80% Au+Au

Elliptic flow : Driven by collision geometry PHOBOS claims collision geometry controls the dynamical evolution of heavy Ion collisions - v 2 what about v 1 ?

Directed flow : depends on beam energy v 1 depends on energy, not on system size.

Elliptic flow : D-mesons and thermalization ? N binary scaling indicates charm production at initial stage of the collisions Substantial non- photonic electron v 2 observed expected D meson v 2 from non-photonic electron v 2

Charm collectivity : thermalization ? 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 AuAu Central charm hadron AuAu Central , K, p AuAu Central strangeness hadron SQM06, Yifei Zhang Peter Braun-Munzinger Shinchi Esumi

Flow : Degree of thermalization Scaled flow values allow constraints for several transport coefficients. Star Preliminary v 4 /v 2 2 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

Elliptic flow : Situation at SPS ? Scaling at low p T not so prominent when plotted as m T - m0 p T reach may be not sufficient to see the quark number scaling SPS way below hydro- dynamical results. RHIC is in that regime V 2 ~ dN/dy

Flow : Longitudinal scaling We observed this for multiplicity Seem to understand this as v 2 ~ dN/dy See similar thing for v 1 and v 4 also…

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

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

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

Conclusion : Flow From the experimental data Future directions  At low p T mass ordering of v 2 values observed and at intermediate p T ordering by quark content (baryon- meson)  Universal scaling observed across p T, centrality, ion species and particle type - when data presented as a function of v 2 /n*  Vs. m T -m 0 /n  v 2 is driven by collision geometry and v 1 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 v 4 /v 2 2 to address the issue of thermalization  Lee-Yang Zeroes method is less biased by non-flow correlation. Nucl. Phy. A 727 (2003)

Recombination V. Greco, C.M. Ko and I. Vitev, PRC 71 (2005) Specific Energy dependence p/   (62.4 GeV) > p/   (200 GeV) 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. Results from :B. Mohanty(STAR), S. Blyth (STAR), J. Bielcikova (STAR), C. Blume(NA49), L.Ruan (STAR) R. Hwa and C. B. yang

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

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

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

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. Recombination still works, but we need a new idea. Yang’s talk tomorrow is still right. Recombination failed ? - Not yet - there are new ideas Phantom jet J. Putschke M. van Leeuwen

Conclusion : Recombination Baryon to meson ratios Azimuthal correlations  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  Initially data on Omega-hadron correlation presented at QM2006 seemed to falsify the recombination picture  Subsequent discussions at QM 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”

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

R dAu vs eta We had seen this : R dAu is suppressed as we go to forward rapidity What about R AA ?

Inclusive charged hadron R AA similar Inclusive charged hadron R AA similar at mid and forward rapidity

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

V 2 Identified particles 200GeV Au+Au  =0  ≈3  K p v 2 (p T ) similar at forward and mid rapidity Remember integrated v 2 (shown by PHOBOS) changes with rapidity

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

How about correlation : Forward and mid-rapidity Trigger: 3<p T trig <4 GeV/c, Associated: FTPC: 0.2<p T assoc < 2 GeV/c, TPC: 0.2<p T assoc < 3 GeV/c Away side in pp: broader at forward than mid-rapidity pp MB Away side in dAu: similar between forward and mid-rapidity dAu MB

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

Conclusion : At forward rapidity What changes? –dN/dy –pbar/p –Chemistry –V 2 (integral) –Initial state (R dAu ) What doesn’t? –Suppression (R AA ) –V 2 (pt) –Away-side azimuthal Correlation

Conditions close to kinetic freeze-out STAR Preliminary Results from : L. Ruan (STAR) A. Irodanova (STAR), D.Das (STAR) 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

Chemical Freeze-out conditions STAR Preliminary 5% central10% centralMin-Bias  Kp thermal fit T ch is fairly constant with dNch/d  but  s for Cu+Cu system seems bit higher GeV

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

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

LHC predictions : Flow Based on simple extrapolation : v 2 ~ 0.08

Conclusion : LHC predictions dN/dy ~ at mid-rapidity Rapidity loss ~ units T ch ~ 166 MeV at mid-rapidity  B ~ 1 MeV at mid-rapidity v 2 ~ 0.08 at mid-rapidity Thanks for your attention!