Piotr Szarwas Adam Kisiel, Fabrice Retière Non-identical particle correlations at STAR

Warsaw November2 / 24 Outline Short history Physics motivation: a measure of emission asymmetry and transverse radial flow Data Analysis/Technical issues Results for -K and -p for 130 GeV Modeling emission asymmetry  130 GeV Blast Wave parameterization RQMD Preliminary results for 200 GeV for -K STAR service work – FileCatalog database design and implementation

Warsaw November3 / 24 Short history First task  Database with web interface for SSD detector (SEE talks tomorrow) I started analysis a year ago HBT and Flow workshop in BNL  first official presentation of my results Poster during QM My results were also included into Fabrice’s talk during QM Service work (SEE talks tomorrow)

Warsaw November4 / 24 Main ideas about non-identical particle correlation Non-identical particles interact after they freeze- out by final state interaction Coulomb and strong interactions - no HBT In -K and -p correlations Coulomb interaction dominate Particles have similar velocities not momentum C2 sensitive to space-time extent and something more…

Warsaw November5 / 24 Asymmetry analysis (classical picture) Catching up: cos   0  long interaction time  strong correlation Ratio of both scenarios allow quantitative study of the emission asymmetry Moving away: cos   0  short interaction time  weak correlation Crucial point: proton begins farther in “out” direction (in this case due to time-ordering) purple P emitted first green p is faster purple P emitted first green p is slower

Warsaw November6 / 24 What we really measure We can assume that pions, kaons, and protons sources have different size and may be their are shifted in source frame We measure only size and shift in pair rest frame Pion source Proton Source Separation between  and P and Boost to pair Rest frame 2 parameters - Mean shift (  r*) - Sigma (  r*)

Warsaw November7 / 24 Asymmetry and flow Initial separation in Pair Rest Frame (what we measure) can come from time shift and/or space shift in Source Frame (what we want to obtain) We are directly sensitive to time shift, the space shift can only be seen with radial flow – new radial flow measurement

Warsaw November8 / 24 Non-identical particle correlations at STAR Year 1 = Au-Au S nn =130GeV -K  paper in preparation (Poster during QM2002) -p  advanced (Poster during QM2002) Year 2 = Au-Au S nn =200GeV -K, -p, p-K  looks promising Year 2 = p-p S nn =200GeV -K, -p  looks promising (SEE Michał Talk)

Warsaw November9 / 24 Non-identical particle correlations at STAR Event selection Year1 = 130 GeV Year2 = 200 GeV Central events – 12% total hadronic cross-section Mid-Rapidity: |Y|< 0.5 dE/dx PID probability to select particle species Detector issues Two-track effects  elimination of tracks with possible shared hits Particle purity(PID probability) Momentum resolution Systematic momentum shift for small p T (energy loss)

Warsaw November10 / 24 Correlation functions and ratios (  -K) Good agreement for like- sign and unlike-sign pairs points to similar emission process for K + and K - Clear sign of emission asymmetry Two other ratios done as a double check – expected to be flat CF Out Side Long Done by Adam & Fabrice

Warsaw November11 / 24 Correlation functions and ratios (  -p) Good agreement for like- sign and unlike-sign pairs Clear sign of emission asymmetry Two other ratios done as a double check – expected to be flat CF Out Side Long Preliminary

Warsaw November12 / 24 Model calculations Hydro inspired blast-wave parameterization - pure dynamics (radial flow) and instantaneous emission RQMD - Includes both time shift and space- momentum correlations (dynamics) UrQMD and Nexus (SEE other talks today)

Warsaw November13 / 24 Blast wave = Flow baseline Blast wave Parameters from:  Spectra: v = 0.52c (transverse flow) and T=110 MeV from spectra  HBT: R = 13 fm (system size) from HBT  No free parameters No time shift  Only spatial shift due to flow Parameterization of the final state R tt Rside Rout Kt = pair Pt

Warsaw November14 / 24 Blast wave: transverse flow shifts average emission points Pion pt = 0.15 GeV/c bt = 0.73 Kaon pt = 0.5 GeV/c bt = 0.71 Proton pt = 1. GeV/c bt = 0.73

Warsaw November15 / 24 Blast wave comparisons (  -p) Blast-wave parametrization: not a fit T = 110 MeV – spectra trans. flow v = 0.52c – spectra radius = 13 fm – HBT No Time shift

Warsaw November16 / 24 Everything combined Calculations done by Fabrice

Warsaw November17 / 24 Data for Year2 maturing – like sign correlation OK, unlike sign not yet Main focus now – tuning the cuts Analysis being done during the stay in LBNL (in cooperation with F. Retiere) π-K correlations – Year2

Warsaw November18 / 24 Conclusion We observe the emission asymmetry between pions, kaons and protons Both average emission time shift and radial flow can contribute to the asymmetry Qualitative agreement with a blast wave scenario which describes other STAR data Also RQMD agree with the data  the same for NA49 Other analysis (kaon-proton…, year 2  200 GeV) in progress

Adam Kisiel, Work done by Adam

Warsaw November20 / 24 Correlation functions and ratios (  -K) Good agreement for like- sign and unlike-sign pairs points to similar emission process for K + and K - Clear sign of emission asymmetry Two other ratios done as a double check – expected to be flat CF Out Side Long

Warsaw November21 / 24 Data for Year2 maturing – like sign correlation OK, unlike sign not yet Main focus now – tuning the cuts Analysis being done during the stay in LBNL (in cooperation with F. Retiere) π-K correlations – Year2

Warsaw November22 / 24 FileCatalog database and interface FileCatalog stores information about various data files and events contained inside (DAQ files, event.root files, MuDSTs and others) User scripts provide a quick way of getting a list of files containing events meeting a specified criteria, together with their location FileCatalog database is an essential component needed for new job dispatcher (Scheduler) and the plan to store data on distributed local disks (at RCF), also needed for DAQ100

Warsaw November23 / 24 FileCatalog implementation Database design, implementation in MySQL, PERL module interface and user utilities (get_file_list.pl script) done by AK in cooperation with Jerome Lauret FileCatalog is now in use at RCF, and is planned to be deployed at PDSF This work was done during the stay in BNL (autumn '01, winter '02), as a service work for Jerome Lauret

Extra slides

Warsaw November25 / 24 Hit sharing cut effect on Side ratio (  -K) Before the cut After the cut Should be at 1.0 as there is no physics effect that can cause the asymmetry Maximum number of shared hits between two tracks = 10% crossing separated opposite K side configurations

Warsaw November26 / 24 Hit sharing cut effect on Side ratio (  -p) Before the cut After the cut Should be at 1.0 as there is no physics effect that can cause the asymmetry Maximum number of shared hits between two tracks = 10% crossing separated opposite K side configurations

Warsaw November27 / 24 Behavior of Lambda peak for Out k* out <0k* out >0 Assume we have a perfect detector, and measure all particles. Half of the L’s will decay into k* out >0 and the other half into k* out <0 For the non- L’s (combinatoric background) there will be more k* out >0 than k* out <0, simply because the proton p T spectrum is less steep than the pion p T spectrum. This means that the L bump will be higher in the C- than the C+, and of course then the “double” ratio will show the bump.

Warsaw November28 / 24  p-  + k* side <0 reconstructed pion momentum too small  M inv too small  p-  + k* side >0 reconstructed pion momentum too big  M inv too big p-  - k* side <0 reconstructed pion momentum too big  M inv too big p-  - k* side >0 reconstructed pion momentum too small  M inv too small = primary vertex =  or  = p or  p =  + or  - Behavior of Lambda peak for Side

Warsaw November29 / 24 Everything combined , K and p source shift consistent with flow? Blast wave as flow baseline Do we need anything else  Time shift due to resonances ( for ,  for p)?

Warsaw November30 / 24  -p Y2

Warsaw November31 / 24 The asymmetry analysis (classical picture) Catching up Interaction time larger Stronger correlation Moving away Interaction time smaller Weaker correlation “Double” ratio Sensitive to the space-time asymmetry in the emission process Kinematics selection may be on any variable e.g. k Out, k Side, cos(v,k) R.Lednicky, V. L.Lyuboshitz, B.Erazmus, D.Nouais, Phys.Lett. B373 (1996) 30.

Warsaw November32 / 24 Main ideas about non-identical particle correlation Non-identical particles interact after they freeze- out by final state interaction Coulomb and strong interactions In -K and -p correlations Coulomb interaction dominate No HBT effect Particles have similar velocities not momentum

Warsaw November33 / 24 K-P Y2 ~100 k central events Strong correlation Rather flat ratios

Warsaw November34 / 24 Correlation functions and ratios (  -K) Good agreement for like- sign and unlike-sign pairs points to similar emission process for K + and K - Clear sign of emission asymmetry Two other ratios done as a double check – expected to be flat CF Out Side Long

Warsaw November35 / 24 3D Gauss & BW Comparision (  -K) Static gaussian source -K: Radius: 9.5 fm Instant emission Time shift between pions and kaons: 8 fm/c Out asymmetry comes only from time shift Blast-wave parametrization: not a fit T = 110 MeV – spectra trans. flow v = 0.52c – spectra radius = 13 fm – HBT No Time shift

Warsaw November36 / 24 RQMD Space  scrambled no correlation No scrambling space–momentum correlations Time Time shift! - ≈3 fm/c k* (GeV/c) R out (fm)

Warsaw November37 / 24 Getting quantitative for  -K Data: fit correlation functions = -6.3 fm (in pair rest frame ) r* =  (r -  t)  t pion -t kaon < 5.6 fm/c  r kaon -r pion < 4.2 fm Data agree with blast wave RQMD overestimates the shift

Warsaw November38 / 24  -K Y2 Source shift ~100K events

Warsaw November39 / 24 RQMD pure and scrambled Can we disentangle time shift and flow? Scrambling the positions, or artificially setting emission time to zero, removes some of the Out asymmetry, The combination of the techniques removes it completely Out asymmetry comes from the combination of time shift and position-momentum correlations

Warsaw November40 / 24 UrQMD model calculations Model studies to see the effect of centrality and rescattering on pion-kaon correlations Test the hypothesis that non-identical particle correlations probe flow Understand the space and time contribution to the asymmetry In cooperation with F.Retiere, S. Soff, N. Xu