Results from STAR at RHIC Mirko Planini for

Results from STAR at RHIC Mirko Planinić for the STAR collaboration University of Zagreb LHC Days in Split 4 -9 October 2010

We will never see the whole body Mirko Planinić LHC Days in Split 2010

Phase diagram of nuclear matter Pressure/atm Phase diagram of water Temperature Mirko Planinić LHC Days in Split 2010

Stages of the collision ? initial state hadronic phase and freeze-out QGP and hydrodynamic expansion pre-equilibrium hadronization Animation by Jeffery Mitchell (B N L). • We detect only signals from the last stage. • In order to be sure that we have QGP we must understand all stages of collision (signatures). Mirko Planinić LHC Days in Split 2010

Relativistic Heavy Ion Collider (RHIC) at Brookhaven PHOBOS PHENIX 1 km RHIC BRAHMS STAR AGS TANDEMS animation by Mike Lisa counter-rotating beams of ions from p to Au @ √s. NN=5 -500 Ge Mirko Planinić 5 LHC Days in Split 2010

STAR detector MRPC To. F Barrel MTD EMC Barrel EMC End Cap FMS BBC FPD TPC PMD FTPC trigger DAQ 1000 HLT computing COMPLETE Ongoing R&D Mirko Planinić 6 LHC Days in Split 2010

Au+Au @ STAR Beamline h~ +0. 5 Quark. Net 2006 90 o h~ +0. 5 creates over 5000 charged particles! (~600 at ~ 90 o to beamline)

Did we reach critical energy density? Lets do a coffee napkin estimate Dh = 1 Look at all produced particles in a Central ‘Head-on’ Collision Total energy released in Dh=1 is ~ 1000 Ge. V Max initial overlap volume Energy Density = Total Energy/Volume ~ 1000 Ge. V/200 fm 3 Initial Energy Density Estimate, e ~ 5 Ge. V/fm 3 cold nuclear matter ≈ 0. 13 Ge. V/fm 3 Mirko Planinić 3 Þ So the answer is YES, we are above the critical value of. LHC ~0. 7 Gev/fm Days in Split 2010

Comparing High Momentum particles Mid-Central Ratio of gold to proton-proton Peripheral We “lose” high momentum (speed) particles for Central Collisions

High p. T suppression STAR p+p reference Binary coll. scaling J. Adams et al, Phys. Rev. Lett. 91 (2003) 072304 ♦RCentral Au+Au collisions: factor ~4 -5 suppression. << 1; R > 1 Confirms final state effects present AA d. Au ♦ p. T >5 Ge. V/c: suppression ~ independent of p. T. ♦ p. QCD describes data only when energy loss included. Mirko Planinić LHC Days in Split 2010

Confirming the probe Survival Probability Photons - unsuppressed Hadrons - suppressed Direct g p 0, h We have an understood and calibrated probe Mirko Planinić LHC Days in Split 2010

Jet quenching Jet correlations in central proton-proton Gold-Gold. reactions. Away side jet disappears Strong back-to-back for particles p. T > 2 Ge. V peaks. Azimuthal Angular Correlations Mirko Planinić LHC Days in Split 2010

Particle emission patterns Peripheral Collisions: Overlap “hot spot” looks like an almond. Reaction plane z y x Do the particle emission patterns reflect this initial shape? If they do – can learn more about timescales of the “cooling” process and help us Mirko Planinić distinguish between liquid and gas behavior LHC Days in Split 2010

View along beamline b (reaction plane) Emission patterns follow the shape of the overlap region. Quark. Net 2006

Fourier analysis of emission patterns. Extract n=2, elliptic flow àFind significant values of v 2 for peripheral collisions. à Behaving like a liquid (collectively) Elliptic flow observable is sensitive to early evolution of system Mirko Planinić Large v 2 is an indication of early thermalization LHC Days in Split 2010

Elliptic Flow for different particles First time hydro works: suggests early thermalization - t = 0. 6 fm/c Hydro by Huovinen et al. hydro tuned to fit central spectra data. e = 20 Ge. V/fm 3 • Pure hydrodynamical models including QGP phase describe elliptic flow for many species QGP-almost perfect fluid STAR PRC 72 (05) 014904 200 Ge. V Au+Au min-bias v 2 is different for different particles Mirko Planinić LHC Days in Split 2010

Elliptic flow v 2 large even for , W Phys. Rev. C 77 (2008) 54901 large v 2 (even , W): strong interactions at early stage large v 2 of , W (low hadronic x-sections): partonic collectivity at RHIC. Mirko Planinić LHC Days in Split 2010

Constituent quark scaling The complicated observed flow pattern in v 2(p. T) for hadrons is predicted to be simple at the quark level under p. T → p. T /n v 2 → v 2 / n , n = (2, 3) for (meson, baryon) Works for p, (p), K 0 s, , , W Constituents of QGP are partons Mirko Planinić 18 LHC Days in Split 2010

v 2 – Cu-Cu vs Au-Au Phys. Rev. C 81 (2010) 44902 Greater non-flow effects in Cu-Cu. n Significantly smaller v 2 in Cu-Cu than in Au-Au for given centrality n Scales with v 2(Npart) n Large non-flow effects at high p. T Mirko Planinić LHC Days in Split 2010

Summary of what we learned at RHIC • Energy density in the collision is way above that where hadrons can exist • p-p reference measurements are well understood • Large suppression of high p. T hadrons • Away side jets are suppressed • Cold nuclear matter effects on jets are small • The medium has quark and gluon degrees of freedom in initial stages • The QGP is flowing like an almost “perfect” liquid We have created new state of matter at RHIC the QGP High p. T results can be explained as due to significant partonic energy loss in the QGP before fragmentation Mirko Planinić

Main themes of the STAR Beam Energy Scan: • Search for turn-off of major s. QGP signatures already established at top RHIC energies • Search for first order phase transition signatures • Search for evidence of critical point

We will never see the whole body Critical point ? Jet quenching Constituent quark scaling Energy density>Ec Elliptic flow High p. T suppression Mirko Planinić LHC Days in Split 2010

Heavy ions at the LHC What are the initial conditions RHICs higher Is gluon saturation seen? luminosity and longer running Is v 2 LHC < v 2 RHIC ? time keep it Time evolution of the medium competitive Is QGP still strongly coupled? Behaving like a perfect liquid or more gas like? Energy loss similar to at RHIC? What is mass/flavor dependence of the Eloss? Heavy flavor copiously produced at RHIC? The expectation: Thank you ! LHC plasma hotter, denser, longer lived With the LHC and RHIC programs running in parallel the 2010’s promise an exciting decade for Relativistic Heavy-Ion Collision Research Mirko Planinić LHC Days in Split 2010

Backup –recent CMS results compared to Au. Au Mirko Planinić LHC Days in Split 2010

Recent CMS p+p results Mirko Planinić LHC Days in Split 2010

STAR’s beam energy scan RUN 10 Mirko Planinić LHC Days in Split 2010

Mirko Planinić LHC Days in Split 2010