Strange Particle Measurements at the CERN SPS NA49 and NA61/SHINE Experiments

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1 Strange Particle Measurements at the CERN SPS NA49 and NA61/SHINE Experiments Outline: Experiments Motivation Evidence for the onset of deconfinement Strange particle production measurements Fluctuations in particle composition Summary Jan Kochanowski University in Kielce for the NA49 and NA61 Collaborations

2 NA61/SHINE and NA49 experiments S.Afanasiev et al., NiM A430, 210 (1999) 2

3 Phase diagram of strongly interacting matter CEP RHIC SPS AGS SIS QCD considerations suggest a 1st order phase boundary ending in a Critical End Point (CEP) lattice calculations locate CEP in the SPS energy range Z.Fodor, S.D.Katz,JHEP 0404,050 (04), R.V.Gavai, S.Gupta,PRD 71, (05) maximum of Critical End Point signal is expected for freeze-out close to CEP SPS energy range 3

4 Phase diagram scan NA49, NA61 experiments High statistics scan with a new vertex det. Detailed scan with existing detector future program approved completed NA49 scan with energy Pb+Pb at 20A, 30A, 40A, 80A, 158A GeV and with system size p+p, C+C, Si+Si, Pb+Pb at 158A GeV NA61-2D scan (T, μb ) with six SPS beam energies 13A, 20A, 30A, 40A, 80A, 158A GeV and five different systems p+p, p+pb, Be+Be, Ar+Ca, Xe+La - higher statistics at least 106 events per energy and per reaction - better centrality selection (PSD detector) and reduction of interactions in the gas inside VTPCs (Helium beam pipe) - similar analysis like in NA49 with better precision 4

5 Evidence for the onset of deconfinement Pb+Pb Pb+Pb horn Pb+Pb step dale rapid changes in energy dependence of hadron production properties provide evidence for the phase transition the LHC and RHIC BES points confirm NA49 measurements and trends Data: Theoretical predictions: NA49: C.Alt et al., PRC 77, (2008) M.Gazdzicki, M.Gorenstein, APP B30, 2705 (99) STAR: L.Kumar, arxiv:1106:6071 (2011), B.Mohanty,QM2011 ALICE: J.Schukraft QM2011, M.Floris QM2011, A.Toia QM2011 and Evidence for the onset of deconfinement A.Rustamov, arxiv: in Pb+Pb collisions at snn 8 GeV 5

6 K*(892), K*(892) production measured by NA49 T. Anticic et al., PRC 84, (2011) p+p, C+C, Si+Si, Pb+Pb 158A GeV yield of K* exceeds that of K* by factors of two similar like for K+ and K- yields (same valence quark composition) yield of K* and K* per wounded nucleon appears to increase from p+p to C+C, Si+Si and then decrease for Pb+Pb collisions at 158A GeV <K*>/<K+>, <K*>/<K-> ratios decrease with increasing size of colliding nuclei. Substantial duration of the hadronic stage of the fireball? 6

7 K*(892), K*(892) production measured by NA49 p+p, C+C, Si+Si, Pb+Pb 158A GeV T. Anticic et al., PRC 84, (2011) Pb+Pb 158A GeV yields of K* mesons in central Pb+Pb collisions are about 2.5 lower than the predictions of HGM with parameters fitted to the yields of stable hadrons * * for the yields of several resonance states (K, K, Λ, φ) measured by NA49 the suppression respect to HGM predictions seems to get stronger with decreasing lifetime of the resonance * Reduction of K yield by rescattering of decay products during hadronic stage? 7

8 First K- production measurements by NA61/SHINE NA61/SHINE and NA49 spectra agree EPOS model reproduces data trends; significant quantitative differences for K NA49 points obtained from xf pt spectra Eur.Phys. J. C68, 1 (2010) EPOS: PRC 74, (2011) 8

9 Fluctuations in particle composition motivation and measures In the vicinity of phase transition distinct fluctuations patterns are expected Event-by-event maximum likelihood fits were used to extract relative Method: C.Alt et al., PRC 79, (2009) species abundances Studied fluctuation measures : - scaled variance (multiplicity fluctuations) Var (N i / N j ) N i / N j 2 i, j particle species (π,k,p) ν dyn sgn (σ dyn ) σ 2dyn 9

10 Identity method The identity method allows to obtain second and third moments of identified particle multiplicity distribution corrected for misidentification effect. PRC 83, PRC 84, arxiv:nucl-th/ Once detector response ( ρi ) and Wi distributions are known the method is used to obtain moments of identified particle multiplicity distributions. ρi,wi,... <Ni2>, <Ni Nj > No event-by-event fits and mixed events required in identity method 10

11 Fluctuations of particle composition Trend of NA49 results at low energies confirmed. Differences between STAR and NA49 results remains. p/π: νdyn < 0 due to resonance decay (reproduced by multiplicity scaling model) Model: V.Koch, T. Schuster, PRC 81, (2010) ν dyn N i N j K/π: νdyn > 0 anti-correlation (reproduced by multiplicity scaling model) Unchanged correlation strength (same physics) with energy? K/p: νdyn shows a strong dependence on energy, going from positive values at low energies to νdyn < 0 at high energies (not reproduced by multiplicity scaling model) Underlying correlation physics (baryon-strangeness) changing with energy? 11

12 Fluctuations of particle composition dependence on acceptance clear difference of NA49 and STAR acceptance for 30A GeV identity method can work with low multiplicity and acceptance cuts can be applied 12

13 Fluctuations of particle composition dependence on acceptance clear dependence on acceptance cut at low SPS energies for K,π and K,p no energy dependence of particle composition for STAR equivalent acceptance Differences between NA49 and STAR results can be explained by different acceptance 13

14 Multiplicity fluctuations of π, K, p NA61: p+p; NA49: Pb+Pb (3.5%) increase of ωπ in Pb+Pb collisions due to NW fluctuations? ωk > 1 ωp < 1 strangeness conservation at least in p+p collisions? baryon number conservation at least in p+p collisions? decrease of ωp with energy in Pb+Pb collisions but increase in p+p interactions EPOS model agrees with p+p data 14

15 Summary Onset of deconfinement in central Pb+Pb, NA49 measurements are confirmed: - results from RHIC agree with relevant NA49 data - first LHC data confirm the interpretation K*(892), K*(892) productions in central C+C, Si+Si, Pb+Pb and inelastic p+p coll.: - observed suppression of K* yields in central Pb+Pb collisions as well as the decrease of <K*>/<K+>, <K*>/<K-> with increasing size of the colliding nuclei may suggest a substantial duration of the hadronic stage of the fireball K- production was measured by NA61 in p+p collisions as a function of y, p T Fluctuations of particle composition : - differences between NA49 (Pb+Pb) and STAR (Au+Au) results can be explained by different acceptance - K/π and p/π fluctuations as a function of energy can be described by a simple multiplicity scaling model whereas K/p fluctuations show a deviation from the model. It can be a hint of changing of underlying correlation physics - multiplicity fluctuations in p+p collisions mainly reflect conservation laws; they are reproduced by EPOS model 15

16 NIKHEF, Amsterdam, Netherlands ETH, Zurich, Switzerland University of Athens, Athens, Greece Fachhochschule Frankfurt, Frankfurt, Germany Comenius University, Bratislava, Slovenia Faculty of Physics, University of Sofia, Sofia, Bulgaria Eotvos Lorand University, Budapest, Hungary Karlsruhe Institute of Technology, Karlsruhe, Germany KFKI IPNP, Budapest, Hungary Institute for Nuclear Research, Moscow, Russia MIT, Cambridge, USA Institute for Particle and Nuclear Studies, KEK, Japan INP, Cracow, Poland Jagiellonian University, Cracow, Poland Joint Institute for Nuclear Research, Dubna, Russia Joint Institute for Nuclear Research, Dubna, Russia GSI, Darmstadt, Germany Wigner Research Centre, Budapest, Hungary University of Frankfurt, Frankfurt, Germany LPNHE, University of Paris VI and VII, Paris, France CERN, Geneva, Switzerland University of Silesia, Katowice, Poland Jan Kochanowski Univeristy, Kielce, Poland Rudjer Boskovic Institute, Zagreb, Croatia University of Marburg, Marburg, Germany National Center for Nuclear Research, Warsaw, Poland MPI, Munich, Germany St. Petersburg State University, St. Petersburg, Russia Charles University, Prag, Czech Republic State Uniwersityof New York, Stony Brook, USA University of Washington, Seattle, USA Jan Kochanowski University in Kielce, Poland Faculty of Physics, University of Sofia, Sofia, Bulgaria University of Athens, Athens, Greece Sofia University, Sofia, Bulgaria Iniversity of Belgrade, Belgrade, Serbia INR&NE, BAS, Sofia, Bulgaria University of Bergen, Bergen, Norway State University of New York, Stony Brook, USA University of Bern, Bern, Switzerland Soltan Institute for Nuclear Studies, Warsaw, Poland University of Frankfurt, Frankfurt, Germany Warsaw University of Technology, Warsaw, Poland University of Nova Gorica, Nova Gorica, Slovenia University of Warsaw, Warsaw, Poland University of Geneva, Geneva, Switzerland Rudjer Boskovic Institute, Zagreb, Croatia University of Warsaw, Warsaw, Poland Warsaw University of Technology, Warsaw, Poland The Universidad Tecnica, Valparaiso, Chile 16

17 Additional Slides 17

18 Evidence for the onset of deconfinement 18

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20 Fluctuation measures studied by NA49 - scaled variance ω of the multiplicity distribution P(n) Var ( n) < n 2 > < n > 2 ω = = < n> < n> intensive fluctuation measure independent particle emission: ω = 1 wounded nucleon model: ω(a+a)=ω(n+n)+<n>ωw ω affected by NW fluctuations - Φx measure of fluctuations of observable x (<p T>, <Φ>, Q) M.Gazdzicki and St.Mrowczynski, Z.Phys. C54, 127(1992) superposition model: Φx(A+A)= Φx(N+N) independent particle emission: Φx= 0 Φx strongly intensive fluctuation measure independent of NW and its fluctuations - F2 factorial moments of low mass π+π- pair number fluctuations in pt space proper mass window and multiplicity are required mixed events used as the reference power-law behavior from σ mode expected - σdyn measure of particle ratio fluctuations ( K/π, p/π, K/p ) 2 2 σ dyn = sign(σ data σ mix ) 2 2 σ data σ mix ; 2 σ dyn = ν dyn E-by-E fit of particle multiplicities required mixed events used as the reference σ2dyn~ 1/NW, sensitive to fluctuations 20

21 Particle ratio fluctuations (standard method) event-by-event PID based on energy loss de/dx in MTPCs inclusive probability density function + event-by-event maximum likelihood fit to extract relative species abundances Θm Method: C.Alt et al., PRC 79, (2009) acceptance different for different species and depends on beam energy; it has to be taken into account for model comparisons reference sample of mixed events which preserve multiplicity distribution quantify effect of finite-number statistics and de/dx resolution dynamical fluctuations: 21

22 Identity method 22

23 Identity method 23

24 Identity method 24

25 Particle ratio fluctuations NA49 data: T.Schuster QM2011 Increase of σdyn towards peripheral collsions for all three ratios Similar trend in RHIC STAR data for (K++K-)/(π++π-) at snn = 62 and 200 GeV B.I.Abelev et al., PRL 103, (2009) UrQMD predicts similar behaviour with Nw Scaling with multiplicities, works for all three ratios V.Koch, T.Schuster PRC 81, (2010) Unchanged correlation strength (same physics) with system size? 25

26 Particle ratio fluctuations NA49 data: T.Schuster QM2011 p/π: σdyn < 0 correlation due to resonance decay S.Jeon,V.Koch PRL 83, 5435 (99) reproduced by hadronic transport models (UrQMD, HSD) Scaling with multiplicities: K/π: σdyn > 0 anti-correlation UrQMD and HSD models are contradictory; neither describes data well Scaling: V.Koch, T.Schuster PRC 81, (2010) Unchanged correlation strength (same physics) with energy? 26

27 Particle ratio fluctuations NA49 data: T.Anticic et al., PRC (2011); T.Schuster QM2011 σdyn shows a strong dependence on snn, going from positive values at low energies to σdyn < 0 at high energies ratio for positive charges K+/p+, has no resonance contribution neither hadronic models (UrQMD, HSD) nor scaling with multiplicities ( V.Koch, T.Schuster PRC 81, (2010) ) describe data Theory: V.Koch, A.Majumder, J.Randrup PRL 95, (05) Is the underlaying correlation physics (baryon-stangeness) changing with energy? 27