1. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 1 Femtoscopy in STAR vs world systematics Zbigniew Chajęcki, OSU for the Collaboration

2. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 2 Outline  HBT in Heavy-Ion Collisions at RHIC  Multiplicity as universal scaling  R(m T ) - direct probe of flow scenario  Femtoscopy in p+p [reminder]  m T scaling of HBT radii (AA/pp) [reminder]  Energy and Momentum Conservation Induced Correlations in p+p  STAR results from p+p (all fits)  world systematics : R inv (N,m T ), R o,s,l (m T )  How different is pp from AA at the end?

3. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 3 Heavy ions at RHIC Multidimensional analysis at RHIC R(√S NN, m T, b, N part, A, B, PID)... but is there a scaling variable?

4. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 4 Multiplicity scaling of HBT radii at RHIC Radii scale with multiplicity Lisa, Pratt, Soltz, Wiedemann, Ann.Rev.Nucl.Part.Sci. 55 (2005) 357-402

5. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 5  Flow is the most important bulk feature at RHIC  mT-dependence of femtoscopy probes flow the most directly  quantitative agreement w/p-only observables m T dependence of pion HBT radii

6. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 6 Femtoscopy - direct evidence of flow Spectra v2v2 HBT Flow-dominated “Blast-wave” toy models capture main characteristics e.g. PRC70 044907 (2004)  K R (fm) m T (GeV/c) STAR PRL 91 262301 (2003) space-momentum substructure mapped in detail 6

7. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 7 Id-pion correlations in p+p STAR preliminary m T [GeV/c 2 ]  p+p and A+A measured in thesame experiment  great opportunity to compare physics  what causes p T -dependence in p+p?  same cause as in A+A?

8. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 8 Femtoscopy in pp vs heavy ions pp, dAu, CuCu - STAR preliminary Ratio of (AuAu, CuCu, dAu) HBT radii by pp HBT radii scale with pp Scary coincidence or something deeper?

9. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 9 Z.Ch., Gutierrez, Lisa, Lopez-Noriega, [nucl-ex/0505009] Pratt, Danielewicz [nucl-th/0501003] Non-femto correlations / SH representation d+Au: peripheral collisions STAR preliminary

10. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 10 Decomposition of CF onto Spherical Harmonics Au+Au: central collisions C(Q out ) C(Q side ) C(Q long ) Z.Ch., Gutierrez, Lisa, Lopez-Noriega, [nucl-ex/0505009] Pratt, Danielewicz [nucl-th/0501003] Q x <0.03 GeV/c

11. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 11 Non-femtoscopic correlations in STAR Baseline problem is increasing with decreasing multiplicity STAR preliminary N-dep. of non-femtoscopic correlations in p+p STAR preliminary

12. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 12 EMCICs in other experiments CLEO PRD32 (1985) 2294NA22, Z. Phys. C71 (1996) 405 Q x <0.04 GeV/c OPAL, Eur. Phys. J. C52 (2007) 787-803 Q x <0.2 GeV/c NA23, Z. Phys. C43 (1989) 341 E766, PRD 49 (1994) 4373 Multiplicity increases

13. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 13 MC simulations ‘ad-hoc’ parameterizations OPAL, NA22, … Common approaches to „remove” non-femtoscopic correlations An alternative explanation: Energy and Momentum Conservation Induced Correlations, Z.Ch. and Mike Lisa [PRC 78 (2008) 064903, ArXiv:0803.022] “zeta-beta” fit by STAR [parameterization of non-femtoscopic correlations in A lm ’s] |Q||Q| |Q||Q| |Q||Q|  

14. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 14 k-particle distributions w/ phase-space constraints single-particle distribution w/o P.S. restriction k-particle distribution (k<N) with P.S. restriction observed P - total 4-momentum

15. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 15 k-particle distribution k-particle distribution in N-particle system N.B. relevant later –Danielewicz et al, PRC38 120 (1988) –Borghini, Dinh, & Ollitraut PRC62 034902 (2000) –Borghini Eur. Phys. J. C30:381-385, (2003) –Chajecki & Lisa, PRC78 (2008) 064903 arXiv:0803.0022 * “large”: N > ~10

16. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 16 The Complete Experimentalist’s Recipe or any other parameterization of CF 9 fit parameters - 4 femtoscopic - normalization - 4 EMCICs Fit this ….

17. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 17 EMCIC fit to STAR p+p data STAR preliminary k T = [0.15,0.25] GeV/ck T = [0.25,0.35] GeV/c k T = [0.35,0.45] GeV/ck T = [0.45,0.60] GeV/c

18. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 18 Fit results: EMCIC parameters STAR preliminary Five physical variables - four fit parameters Can we verify whether kinematic variables showing up in fit parameters have physical values?

19. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 19 Various fits to STAR p+p data STAR preliminary

20. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 20 m T scaling of HBT radii Various fits give different radii but m T scaling of HBT radii still holds STAR preliminary

21. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 21 Multiplicity dependence in p+p 200 GeV R inv [fm] STAR preliminary

22. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 22 p+p vs heavy ions - R(N,m T ) STAR preliminary Similar m T and multiplicity dependence of HBT radii in p+p and heavy ions in STAR Is STAR p+p unique? Let’s look at world’s results on HBT in elementary particle collisions …

23. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 23 Z.Ch. arXiv:0901.4078 [nucl-ex] Femtoscopy in small systems System√s [GeV]FacilityExperiment p-p 1.9LEARCPLEAR 1.9CERNABBCCLVW 7.2AGSE766 17SPSNA49 -prelim 26SPSNA23 27.4SPSNA27 31-62ISRAFS 44,62ISRABCDHW 200SPSNA5 200RHICSTAR-prelim p-  p 53ISRAFS 200SPSNA5 200-900SPSUA1 1800TevatronE735 -- 126ISRAFS h-p 5.6CERNABBCCLVW 21.7SPSEHS/NA22 System√s[GeV]FacilityExperiment e+e-e+e- 3-7,29SLACMark-II 10CESRCLEO 29SLACTPC 29-37PETRATASSO 58TRISTANAMY 91LEPOPAL 91LEPL3 91LEPDELPHI 91LEPALEPH e-p 300HERAZEUS 300HERAH1  -p 23CERNEMC-NA9  -N 30TevatronE665 -N >10BBNC R ≈ 0.5 - 1.5 fm

24. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 24 My first impression Can we do a direct comparison between experiments?

25. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 25 Parameterizations of 1D CF used in comparision b/w experiments R B ≈2·R G

26. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 26 R(N) - world systematics R(N, ) - no point to compare the magnitude of the HBT radii between experiments since almost each experiment has different ; e.g. (E735) > (STAR) -look for trends, instead! STAR preliminary

27. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 27 1D R(p T ) * ** STAR preliminary

28. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 28 3D R(m T ) Leptonic results included! STAR preliminary

29. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 29 EMCICs seen in small systems Femtoscopy similar in p+p as in Au+Au @ STAR “World results” show both p T and N dependence! Same physics in p+p as in Au+Au and the only difference due to phase-space effects? possibilities: 1.HBT signals are insensitive to underlying physics (flow etc) 2.they are sensitive & the very different physics of A+A and p+p look coincidentally identical 3.they are sensitive, and driving physics is the same Summary

30. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 30 R inv (N,√s) - world systematics 7.21 GeV21.7 GeV27.4 GeV 1800 GeV31-62 GeV STAR preliminary 200 GeV

31. Z. Ch. for STAR - WWND 2009, Big Sky, MT, Feb. 1-8, 2009 31 R G /R B (N, √s) - world systematics 21.7 GeV 1800 GeV 200-900 GeV 200 GeV 53-126 GeV STAR preliminary UA1