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Zbigniew Chaj ę cki Ohio State University

Z. Ch. & M. Lisa, PRC 78 064903 (2008) Z. Ch. & M. Lisa, PRC 79 034908 (2009) Z. Ch., Acta Phys.Polon.B 40 1119 (2009) Z. Ch. & M. Lisa, to be published. Collectivity in p+p collisions?. Zbigniew Chaj ę cki Ohio State University. Outline & Motivation.

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Zbigniew Chaj ę cki Ohio State University

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  1. Z. Ch. & M. Lisa, PRC 78 064903 (2008) Z. Ch. & M. Lisa, PRC 79 034908 (2009) Z. Ch., Acta Phys.Polon.B 40 1119 (2009) Z. Ch. & M. Lisa, to be published Collectivity in p+p collisions? Zbigniew ChajęckiOhio State University Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  2. Outline & Motivation • common understanding of heavy ion collisions [soft sector] • p+p as a reference to heavy ion collisions • Effect of the phase-space constraints due to energy and momentum conservation • Results from 2-pion correlations in HIC and p+p • Femtoscopic correlations • Re-examining multiplicity-evolution of pT spectra, considering evolution of available phase space • postulate of unchanging parent distribution • Consistent treatment of the phase-space constraints and bulk in femtoscopy and spectra • Summary Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  3. Heavy-ion collisions - A system A+A  a system Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  4. Heavy Ion Collisions : Explosive flow revealed through specific fingerprints on soft-sector observables Femtoscopy : two-pion correlations Femtoscopy : non-id particle correlations Femtoscopy : identical particle correlations v2 Spectra R (fm) R (fm)  slow  K mT (GeV/c2) mT (GeV/c2) fast  STAR PRL 91 262301 (2003) Spectra v2 Femtoscopy STAR PRL 91 262301 (2003) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  5. Importance of reference ? = Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  6. p+p as a reference: hard sector STAR, PRL93 (2004) 252301 = Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  7. p+p as a reference: soft sector radial flow eliptic flow STAR PRL 92 112301 (2004) Au+Au p+p ? = “flow” Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  8. Phase-Space varies with multiplicity Phase-space factor: Hagedorn/Fermi Phase-space constraints Extreme case, N=3, easily calculable with Dalitz plot What about the effect for higher number of particles? Dalitz plot for a three-body final state. (p at 3 GeV), PDG 2008 Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  9. Correlations arising (only) from conservation laws (PS constraints) single-particle “parent” distribution w/o P.S. restriction “distortion” due to PS constraints what we measure with P.S. restriction k-particle distribution (k<N) no other correlations • Danielewicz et al, PRC38 120 (1988) • Borghini, Dinh, & Ollitraut PRC62 034902 (2000) • Borghini, Eur. Phys. J. C30:381-385, (2003) • Chajecki & Lisa, PRC 78 064903 (2008), PRC 79 034908 (2009) CLT approximation works best for N>10 & Ei< 23<E> Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  10. Phase-space effect on kinematic observables 1-particle PS effect 2-particle PS effect N=40 3-particle PS effect Borghini et al, PRC 66 014901 (2002) - also, Danielewicz, PLBB157:146 (1985) NA49 pions N. Borghini, PRC75:021904 (2007) Finite-particle constrains Z.Ch, M.Lisa, PRC 79 034908 (2009) N=5 CF (GenBod) EMCICs Z. Ch, M. Lisa, PRC 78 064903 (2008) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  11. k-particle correlation function Dependence on “parent” distrib f vanishes, except for energy/momentum means and RMS 2-particle correlation function (1st term in 1/N expansion) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  12. What’s the effect of PSD – nontrivial ! • structure not confined to large Q • kinematic cuts have strong effect event generator (genbod) with only E&M conservation Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009 Genbod N=18 <K>=0.9 GeV; PRF - ||<0.5

  13. The Complete Experimentalist’s Recipe 9 fit parameters - 4 femtoscopic - normalization - 4 EMCICs or any other parameterization of CF Fit this …. Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  14. Fits to STAR p+p data kT = [0.15,0.25] GeV/c kT = [0.25,0.35] GeV/c kT = [0.35,0.45] GeV/c kT = [0.45,0.60] GeV/c STAR preliminary Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  15. Fit results: STAR p+p@200 GeV Five physical variables - four fit parameters Can we verify whether kinematic variables showing up in fit parameters have physical values? STAR preliminary Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  16. femtoscopy in p+p @ STAR Z0 decay @ LEP mT dep. of HBT radii - World Systematcs R Z(fm) DELPHI  π R (fm) K p Λ Z. Ch., Acta Phys.Polon.B 40 1119 (2009) m, mT (GeV) hep-ph/0108194 1. Heisenberg uncertainty? 2. String fragmentation? (Lund) • e.g. G. Alexander • “plausible” in z-direction • unlikely in transvrse • inconsistent with mult-dep • p+p and A+A measured in same experiment, same acceptance, same techniques • unique opportunity to compare physics • what causes pT-dependence in p+p? • same cause as in A+A? 3. Resonance effects? • essentially no quantitative predictions • pT dependence maybe (??) • mass dependence no [Andersson, Moriond 2000] 4. Flow??? • e.g. Wiedemann & Heinz ‘97 • maybe, but will be significantly different effect than for Au+Au • Increasingly suggested in HEP experiments HBT HBT+ “conservation” Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  17. NA22 Collaboration Z. Phys. C 71, 405–414 (1996) (hadron-hadron collisions) • RHIC: “comparison machine” • Vary size. All else fixed. [acceptance, technique…] • spectra • femtoscopy • compare with a system we “know” is flowing OPAL Collaboration, Eur.Phys.J.C52:787-803,2007; arXiv:0708.1122 [hep-ex] [based on shape of C(q)…] Our data do not confirm the expectation from the string type model… A good description of our data is, however, achieved in the framework of the hydrodynamical expanding source model. E735 Collaboration, PRD48 1931 (1993) also PLB 2002 consistent with an expanding shell model. W. Kittel Acta Phys.Polon. B32 (2001) 3927 [Review article] R2tside , R2tout and, less markedly, R2long decrease with increasing kt . The presence of correlations between the particle production points and their momenta is an indication that the pion source is not static, but rather expands during the particle emission process. … and suggests the existence of an important “collective flow”, even in the system of particles produced in e+e− annihilation! A 1/√m T scaling first observed in heavy-ion collisions is now also observed in Z fragmentation and may suggest a “transverse flow” even there! Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  18. Heavy Ion Collisions : Explosive flow R (fm) mT (GeV/c2) Spectra v2 Femtoscopy STAR PRL 91 262301 (2003) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  19. Apples:apples comparison… Ratio of AuAu HBT radii by pp • R(pT) taken as strong space-time • evidence of flow in Au+Au • clear, quantitative consistency predictions of BlastWave • “Identical” signal seen in p+p • cannot be of “identical” origin?(other than we “know it cannot”...) STAR preliminary Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  20. Au+Au 0-5% Au+Au 60-70% p+p minbias STAR PRL 92 112301 (2004) • Blast-wave fit to spectra: • much less explosive flow in p+p collisions Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  21. 1-particle phase-space effect STAR PRL 92 112301 (2004) Then we would measure: measured Au+Au 0-5% Au+Au 60-70% “distortion” of single-particle spectra “matrix element” What ifthe only difference between p+p and A+A collisions was N? p+p minbias STAR PRL 92 112301 (2004) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  22. Multiplicity evolution of spectra - p+p to A+A (soft sector) STAR PRL 92 112301 (2004) N evolution of spectra dominated by PS “distortion” p+p system samples same parent distribution, but under stronger PS constraints Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  23. Kinematic scales of “the system” Fit results for p+p consistent with expectations from Maxwell-Boltzman equation, Blast-wave, Pythia, … • postulate of same parent consistent with all spectra • magnitude • pT dependence (shape) • mass dependence Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  24. Consistency check …. Characteristic scales of relevant system in which limited energy-momentum is shared Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  25. By popular demand Blast-Wave Model: F. Retiere, M. Lisa, PRC70:044907,2004. STAR PRL 92 112301 (2004) Almost universal “flow” & “temperature” parameters in a BlastWave fit Apparent changes in β, T with dN/dη caused by finite phase-space effect p+p Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  26. Fits to pion CF in p+p by STAR Use parameters obtained from the fit to STAR femtoscopic correlation function and use them to “correct” spectra kT = [0.35,0.45] GeV/c STAR preliminary STAR Preliminary kT = [0.35,0.45] GeV/c Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  27. Combined fit: consistent flow-based description Blast-Wave Model: F. Retiere, M. Lisa, PRC70:044907,2004. Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  28. Combined fit: consistent flow-based description “raw” (ignoring PS effets) p+p collisions show same radial flow signals as A+A collisions PS effects fixed by correlations Joint spectra/HBT BW fit PS effects free adjusted to spectra & fit to spectra PS effects fixed by correlations Joint spectra/HBT BW fit “raw” (ignoring PS effects) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  29. Heavy Ion Collisions vs p+p R (fm) mT (GeV/c2) Spectra v2 Femtoscopy STAR PRL 91 262301 (2003) Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  30. Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  31. Summary STAR Preliminary exp CF HBT HBT+ “conservation” STAR PRL 92 112301 (2004) ? • Energy and momentum conservation induces phase-space constraint that has explicit multiplicity dependence • should not be ignored in (crucial!) N-dependent comparisons • significant effect on 2- (and 3-) particle correlations [c.f. Ollitrault, Borghini, Voloshin…] • …and single-particle spectra (often neglected because no “red flags”) • Femtoscopy & Spectra • in H.I.C., well understood, detailed fingerprint of flow • RHIC – first opportunity for direct comparison with p+p • accounting for finite phase-space effects  identical flow signals in p+p Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

  32. b Z. Ch. - RHIC & AGS Annual Users' Meeting, June 2, 2009

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