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FLUCTUATION as a signal of QGP: Present Experimental Results

FLUCTUATION as a signal of QGP: Present Experimental Results. Au+Au at RHIC. Large number particles in each event (at SPS, RHIC and LHC) allows for Event-by-Event physics Study of Event-by-Event Fluctuations become quite relevant. Tapan Nayak Jan 6, 2003. Event-by-Event Fluctuations.

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FLUCTUATION as a signal of QGP: Present Experimental Results

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  1. FLUCTUATION as a signal of QGP: Present Experimental Results Au+Au at RHIC • Large number particles in each event (at SPS, RHIC and LHC) allows for Event-by-Event physics • Study of Event-by-Event Fluctuations become quite relevant. Tapan Nayak Jan 6, 2003

  2. Event-by-Event Fluctuations • J.D. Bjorken 1992 • Rajagopal & Wilczek 1993

  3. Tricritical point of QCD phase diagram Stephanov, Rajagopal and Shuryak PRL 81 (1998) Similar to behavior of strange quark mass and temperature in m-T plane At the TRICRITICAL POINT: singularities in thermodynamical observables => LARGE EVENT-BY-EVENT FLUCTUATIONS

  4. s s Formation of DCC: gives rise to a pulse of low pT pions with a probability: p p Chiral Symmetric pions Large fluctuations in number of photons and charged particles f Centauro, anti-Centauro events Disoriented Chiral Condensates (DCC) Normally:Each of the pion flavors are roughly equally populated. We define:

  5. MEASURES OF FLUCTUATIONS Space-time evolution of fluctuations are important!

  6. SPMD : 2.35 < h < 3.75 PMD : 2.9 < h < 4.2

  7. 158.A GeV Pb+Pb at SPS Gaussians for narrow bins in centrality Min. Bias Nch Min. Bias Photons STATISTICAL + DYNAMICAL

  8. Multiplicity Fluctuation Participant model: N : Particle Multiplicity Npart : No. of participants ni : No of particles produced by ith participant, accepted within the acceptance of detector • CENTRALITY • ACCEPTANCE Multiplicity distributions are GAUSSIANS for narrow bins in centrality. The physics (statistical + dynamical) is in the width of the distribution. The amount of fluctuation w = s2/ < N >

  9. Multiplicity Fluctuations for various centralities Photons Charged Particles Peripheral Central Data agree fairly well with participant model calculations

  10. Fluctuations ofCh. particlesvs. Photons Single event display => Charged particles superimposed on photons

  11. Ngvs. Nch FLUCTUATIONS • Top 5% central events ONLY • Bins in f : 1,2, 4, 8, 16 • Discrete Wavelet Analysis • Correlation Analysis: Localized phase fluctuations

  12. RMS WIDTHS OF DATA compared with GEANT & 4-types of MIXED EVENTS Data width > M1 width Data width = M2 width Data width > M3-g and M3-ch • Data widths > M1 • => Presence of localized • fluctuations in • Ng • Nch • Correlated • fluctuation X

  13. Formation of DCC – upper limits Localized DCC domain Centrality Not detectable Global DCC 0-5% central • Localized fluctuations decrease from central to peripheral. • Upper limit for DCC-like localized fluctuations: 3x10-3 for central collisions. 1. Phys.Lett.B420:169-179,1998 2. Phys.Rev.C64:011901,2001 3. nucl-ex/0206017, to be published in PRC Krzywicki & Serreau Phys. Lett.B 448 (1999) 257

  14. RHIC Results so far No indication of additional or decreased fluctuation observed so far. Balance function width

  15. PMD In STAR experiment at RHIC PMD SuperModule Photon Multiplicity Detector (PMD) • Preshower Detector, fine granularity • Two planes: Veto + Pre-shower • Total no. of cells: 82,944 • Gas detector with hexagonal cells • h Coverage: 2.3 – 3.9 • Cell c.s.: 1.0 cm2, depth: 0.8 cm • Area of the detector: 4.2m2 PMD in Full STAR setup

  16. In ALICE Experiment at CERN Front View of PMD • Gas detector with • hexagonal cells. • 170,000 honeycomb • cells (each of 0.22 • cm2 area). • Two planes • Total area: 1.8m2 • for each plane. MUON ARM

  17. SUMMARY • Study of Fluctuations of various quantities provides a powerful • means of observing QCD phase transition. • Measurement at SPS gives • no evidence of non-statistical fluctuation • no indication of e-by-e correlated fluctuations (DCC-type) • Upper limits of DCC production is set at 90% C.L. • Event-by-event physics and fluctuations should be studied along • with other signals as functions of centrality of the collision and • various colliding systems. QCD phase transitions can be studied thru anomalous fluctuations and correlations – just as in real life situations.

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