160 likes | 166 Views
STAR physics program and technical challenges with the RHIC Au+Au energy scan. Grazyna Odyniec/LBNL for STAR collaboration QM 2008 , Jaipur, India, February 2008. Outline : HI - study exp. QCD phase diagram BES at RHIC Program Experimental questions.
E N D
STAR physics program and technical challenges with the RHIC Au+Au energy scan Grazyna Odyniec/LBNL for STAR collaboration QM 2008, Jaipur, India, February 2008 Outline : HI - study exp. QCD phase diagram BES at RHIC Program Experimental questions
QCD phase diagram M.Stephanov, hep-ph/0402115v1 (March 2006) Predictions (models, lattice) for location of CP: dense & hot medium deconfined phase (partonic dof) continuous transition (crossover) critical point (CP) hadron gas Search for CP needs measurements over a broad range of mB and T QM 2008, Jaipur, India, February 2008
Beam Energy Scan at RHIC: sNN ~ 5-50 GeVexperimental window to QCD phenomenologyat finite temperature and and baryon number density • At RHIC : indications of sQGP found • but remain unknown: • properties of hypothesized sQGP • boundary between hadronic and partonic phases • possible critical point QM 2008, Jaipur, India, February 2008
“sQGP” at RHIC top energy RHIC At RHIC: LHC • mT-NQ scaling • partonic collectivity • deconfinement RHIC experiments in agreement hot and dense matter with partonic collectivity has been formed at RHIC QM 2008, Jaipur, India, February 2008
Some indications at lower energies – NA49 at SPS NA49 PRC 40A GeV proton v2 non-monotonic K+/p+ behavior,“horn”, but dynamical fluctuations quite monotonic…? collapse of proton v2 - signature of phase transition (Stoecker,Shuryak), but result depends on analysis technique … ? inconclusive QM 2008, Jaipur, India, February 2008
Access to large range of mB and T Beam Energy Scan (BES) at RHIC + SPS + FAIR RHIC: advantage of collider geometry ! At fixed target geometry: detector acceptance changes with energy track density at mid-y increases fast with energy -> technical difficulties in tracking QM 2008, Jaipur, India, February 2008
RHIC run 10 (fall 2009) (1) Large energy range accessible (2) Collider geometry (acceptance won’t change with S, track density varies slowly) (3) STAR detectors well suited (large acceptance), tested & understood STAR PAC 2007 Strawman proposal: Note: NA61 @ CERN (starting in 2010): 10, 20, 30, 40, 80, 158 GeV/c QM 2008, Jaipur, India, February 2008
STAR experience with Low Energy RHIC running see D. Cebra talk observed apparent rates of collisions surprisingly high (?!) to do: (1) understand background (2) optimize triggering 2001: 19.6 GeV Au+Au 2004: 22.4 GeV Cu+Cu 2007: 9 GeV Au+Au 2008: 9 (5?) GeV Au+Au STAR TPC image of 9 GeV Au+Au, taken on June 7, 2007 (run 8158119, ev.44), figure from Jeff Langraf QM 2008, Jaipur, India, February 2008
Analysis of 9 GeV run data (June 2007) Preliminary conclusions very optimistic, but …. in 2500 events on tape fewer than 1 % vertex candidates were found During 2008 d+Au run a contribution to the BBC coincidence rate from beam-background coincidence was identified: • - background can explain almost entire event rate during the low energy test • actual event rate is unknown and could be very low • time for physics program may be underestimated • BBC alone is not a good measure of luminosity for the low energy run -> new run: BBC&&CTB(TOF) • trigger ? QM 2008, Jaipur, India, February 2008
STAR experiment readiness for Low Energy Run STAR will measure : yields and particle ratios T vs mB, particle spactra (pt, rapidity, …), strangeness production (K/p, multistrange, …), fluctuations and correlations (including forward-backward corr), flow (v1,v2,v4, …) with charged and identified particles, HBT radii, (if statistics adequate - possibly charm, jets/high pt, …) Search for : - disappearance of partonic activities - fluctuations, correlations turn on and off signature of deconfinement (-> simulations showing sensitivity-work in progress) QM 2008, Jaipur, India, February 2008
Experimental challenges at low energy run under discussion: new detector (RPSD) to (1) determine reaction plane and (2) t0 for TOF is under discussion • to achieve those goals, we need: • triggering • PID (TOF completed by 2010) • reaction plane determination but rates without low energy e-cooling: ~5 Hz at 4.6 GeV; with e-cooling much better QM 2008, Jaipur, India, February 2008
Triggering BBC is sensitive down to single MIP hitting the detector BBC Upgrade: 1 PMT for each tile (important at low energies) BBC can effectively trigger for low energy runs (-> centrality from reference multiplicity), but one needs to worry about background -> new test run March 2008 (BBCx&&CTB/TOF ?) QM 2008, Jaipur, India, February 2008
Particle Identification in STAR log10(dE/dx) log10(p) TOF completed in 2010 • TOF alone: (p,K) up to 1.6 GeV/c, p up to 3 GeV/c • TOF+TPC(dE/dx, topology) up to 12 GeV (NIMA 558 (419) 2006) PID capabilities (stat.) cover a broad range: ~ 0.2 – 12 GeV/c QM 2008, Jaipur, India, February 2008
Reaction Plane Determination v1 Kejun Wu v2 Good reaction plane resolution – a new detector under consideration QM 2008, Jaipur, India, February 2008
Summary • The unique RHIC energy scan program will map the QCD diagram in sNN =5-50 GeV, (corresponding to mB ~ 600-150 MeV) • systematic study of collective dynamics and fluctuations with p, L, X, W, p, K, K*, r, f... • turning off partonic activities (e.g. v2 of f, W, D – no NQ scaling, quenching ->0, …) • STAR detector with 2p acceptance is ready to carry out this program • can trigger on low energy events (tests) • full TOF in 2010 -> PID • low energy e-cooling at RHIC extremely beneficial QM 2008, Jaipur, India, February 2008
THANKS ! QM 2008, Jaipur, India, February 2008