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EXPERIMENTAL REVIEW OF DISORIENTED CHIRAL CONDENSATES

EXPERIMENTAL REVIEW OF DISORIENTED CHIRAL CONDENSATES. Bedanga Mohanty Variable Energy Cyclotron Centre, Kolkata. OUTLINE Motivation Experimental Signatures Experiments Experimental Techniques Experimental Results Possibility and Limitations Summary. MOTIVATION.

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EXPERIMENTAL REVIEW OF DISORIENTED CHIRAL CONDENSATES

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  1. EXPERIMENTAL REVIEW OF DISORIENTED CHIRAL CONDENSATES Bedanga Mohanty Variable Energy Cyclotron Centre, Kolkata OUTLINE • Motivation • Experimental Signatures • Experiments • Experimental Techniques • Experimental Results • Possibility and Limitations • Summary Bedanga Mohanty

  2. MOTIVATION Chiral Symmetry is broken in ground state Possibility of it’s restoration for a hot and dense matter One of the consequence of this is formation of disoriented chiral condensates Study and detection of DCC : • Nature of chiral phase transition • Vacuum structure of strong interaction A.A. Anselm et al., PLB 261(1991) 482 Rajagopal et al NPB 404 (1993)577 Bedanga Mohanty

  3. EXPERIMENTAL SIGNATURE Ch. particlesvs. Photons Look at Ng vs. Nch correlation Bedanga Mohanty

  4. COSMIC RAY EXPERIMENTS It all started with the detection of a Centauro Event by JACEE Collaboration One of the possible explanation of such events was DCC PAMIR experiment (1977 – 1991) has given, so far the most direct evidence of DCC formation in cosmic ray events Bedanga Mohanty

  5. NUCLEON-NUCLEON COLLISION UA1 experiment at s = 540 GeV p - p¯ collisions Electromagnetic and Hadronic calorimeters UA5 experiment at s = 540 and 900 GeV p - p¯ collisions Streamer chamber for charged particles (4 coverage) Photons measured by putting a converter between 2 streamer chambers D0 and CDF at FERMILAB s = 1.8 TeV Looked at asymmetry in hadronic and electromagnetic energies MINIMAX at FERMILAB s = 1.8 TeV p - p¯ collisions Charged particles detected through MWPC Photons through PbSc electromagnetic Calorimeter Bedanga Mohanty

  6. NUCLEUS-NUCLEUS COLLISION WA98 at CERN SPS Center of Mass Energy = 17.3 GeV Ion : Pb beam on Pb target Photon and charged particle multiplicity detector with common  coverage between 2.9 to 3.75 STAR and PHENIX at RHIC PMD/EMCAL with TPC/FTPC in STAR EMCAL and drift and pad chambers in PHENIX NA49 at CERN SPS Through measurement of charged particles in more than 2m long TPC pT coverage from 0.005 GeV/c to 1.5 GeV/c and  between 4 to 5.5 ALICE at CERN LHC PMD and FMD PHOS and TPC Bedanga Mohanty

  7. TYPICAL EXPERIMENT FOR DCC SEARCH SPMD : 2.35 < h < 3.75 PMD : 2.9 < h < 4.2 Bedanga Mohanty

  8. EXPERIMENTAL TECHNIQUES Several experimental techniques were devised to specifically look for DCC and several already existing ones were modified for DCC purposes Photon-charged particle correlation Discrete Wavelet Technique Robust Observable Event Shape Analysis Phi-measure Photon-to-charge ratio fluctuation Bedanga Mohanty

  9. PHOTON AND CHARGED PARTICLE CORRELATION Plot event-by-event Nch Vs. Ng Get the perpendicular distance of each point from the Correlation line Get the distribution of these distances Broader the distribution more is the fluctuation Bedanga Mohanty

  10. DISCRETE WAVELET TECHNIQUE B.K. Nandi, T.K. Nayak, B. Mohanty, D.P. Mahapatra and Y.P. Viyogi Phys. Lett. B461 (1999) 142 Define photon fraction in highest resolution bins Choose a basis (Haar, D4..) Look at the distribution of the father function coefficients (FFC) at different scales Broader the FFC distribution more is the fluctuation Bedanga Mohanty

  11. ROBUST OBSERVABLES Developed by the MINIMAX collaboration, called as robust, as it take cares of detector effects Strong correlation between Ri,1 Vs. i for DCC-type events; absent for normal events Ri,1 = Fi,1 / Fi+1,0 Fi = <N(N-1)…(N-i+1)> / <N>i Fi,j = <Nch(Nch-1)..(Nch-i+1)Ng(Ng-1)..(Ng-j+1)> / <Nch>i <Ng>j Bedanga Mohanty

  12. EVENT SHAPE ANALYSIS B.K. Nandi, G.C. Mishra, B. Mohanty, D.P. Mahapatra and T.K. Nayak Phys. Lett. B449 (1999) 109 Uses flow technique to look for DCC Basic point exploited is event shape of DCC Can be used as a complimentary method along with other techniques Bedanga Mohanty

  13. -MEASURE B. Mohanty, Int. J. Mod. Phys. A18 (2003) 1067   has been modified to make it sensitive for DCC-type fluctuations  ~  <N><f2> - <f>(1-<f>) -measure is an observable widely used for fluctuation studies and is defined as <Z2>/<N> - <z2> z = x - <x> : single particle variable and Z = multi-particle analog Bedanga Mohanty

  14. A FLUCTUATION PROBE FOR DCC Fluctuation in the ratio, R : The average is over events and where We define: DDCC = 1.8 This difference is significant and provides a powerful method of DCC search. B Mohanty, D. Mahapatra and T.Nayak Phys.Rev.C 66 (2002) 044901 Bedanga Mohanty

  15. COSMIC RAY RESULTS C.R.A. Augusto et al., Phys. Rev. D59 (1999) 054001 Solid triangles : PAMIR data Solid squares : Generic production Do not exclude the possibility of DCC formation mechanism In high energy interactions Bedanga Mohanty

  16. NUCLEON-NUCLEON  UA5 RESULTS K. Alpgard et al., (UA5 Collab.) Phys. Lett. B115 (1982) 71 G.J. Alner et al., (UA5 Collab.) Phys. Lett. B180 (1986) 415 <R> Charged particle ET Photons <R> = Ehad – Eem / Ehad + Eem Correlation of charged multiplicity and photon multiplicity Upper limit on Centauro events = 0.24% Bedanga Mohanty

  17. NUCLEON-NUCLEON  UA1 RESULTS G. Arinson et al., (UA1 Collab.) Phys. Lett. B122 (1983) 189 data Simulation Electromagnetic energy No DCC Electromagnetic energy Hadronic energy Hadronic energy Correlation between electromagnetic energy and hadronic energy Bedanga Mohanty

  18. NUCLEON-NUCLEON  MINIMAX RESULTS T.C. Brooks et al., (MINIMAX Collab.) Phys. Rev. D 61 (2000) 032003 Pure DCC : R(1,1) ~ 0.6 – 0.7 Exclusive production : Event either DCC or generic Associated production : DCC production proportional to Generic production Upper limit on DCC production DCC event per generic event < 0.21 Probability an event is DCC < 0.05 Bedanga Mohanty

  19. NUCLEUS-NUCLEUS  WA98 RESULTS Ref : Phys.Lett.B420:169-179,1998 Bedanga Mohanty

  20. NUCLEUS-NUCLEUS  WA98 RESULTS Ref : PRC 64 (2001) 011901 (R) • Top 5% central events ONLY • Bins in f : 1,2, 4, 8, 16 • Discrete Wavelet Analysis • Correlation Analysis: Results from data compared to mixed events and simulation Bedanga Mohanty

  21. NUCLEUS-NUCLEUS  WA98 RESULTS Ref : PRC 67 (2003) 044901 B. Mohanty, P. hD Thesis Utkal University Fluctuations in both : Ng & Nch Localized fluctuations decrease from central to peripheral. Upper limit for DCC-like localized fluctuations: 3x10-3 for central collisions. Bedanga Mohanty

  22. NUCLEUS-NUCLEUS  WA98 RESULTS M.M. Aggarwal (WA98 Collab.), Pramana 60 (2003) 987 An event with 90° patch having ƒ = 0.7 Preceding and Succeeding events normal Bedanga Mohanty

  23. NUCLEUS-NUCLEUS  NA49 RESULTS H. Appelhauser et al., (NA49 Collab.) Phys. Lett. B 459 (1999) 679 Momentum fluctuation  DCC Bedanga Mohanty

  24. NUCLEUS-NUCLEUS  PHENIX RESULTS Typical Centauro event Reported by PHENIX + charged particles O photons T. Nakamura (PHENIX Collab.) Poster at QM2002 Bedanga Mohanty

  25. POSSIBILITIES AND LIMITATIONS B. Mohanty et. al : Int. J. Mod. Phys A19 (2004) 1453 DCC MODEL : Introduce DCC-type fluctuations in VENUS event generator by isospin flipping of pions with the probability . Domain defined in terms of its extent in pseudo-rapidity and azimuthal angle Method of analysis : Wavelets Signal/Background Signal (S) : of DCC distribution Background (B) : of normal distribution Bedanga Mohanty

  26. LIMITATIONS - I Shift in f-distribution in the lower range Effect more for smaller domains of DCC Charge excess events affected Bedanga Mohanty

  27. LIMITATIONS - II Multiple domain, detector effects and charged particle contamination in photons Correlation due to contamination masks signal Multi-domains – Following Central limit Theo. f-dist approaches normal distribution Realistic efficiency and purity of particle detection shrinks f-distribution Bedanga Mohanty

  28. POSSIBILITIES - I Multiplicity of pions and sensitive analysis techniques Carrying out analysis by dividing the phase space helps in case of multiple domains of DCC Higher Multiplicity reduces the statistical fluctuations Bedanga Mohanty

  29. POSSIBILITIES - II Knowing the purity – effect can be corrected Effect of charged particle contamination in photon sample can be reduced Better to analyze events with higher f values Bedanga Mohanty

  30. POSSIBILITIES - III Charge excess Vs. Photon excess events Better to look for events with photon excess Bedanga Mohanty

  31. POSSIBILITIES - IV Momentum information of particles Charged particle detector with particle-wise momentum information + a photon multiplicity detector is the best option Bedanga Mohanty

  32. SUMMARY Exotic events DCC ?? Null results Upper limit Look for PHOTON excess events, within different pT regions Using a multi-resolution technique Strange DCC ?? – Gavin, Kapusta Isospin fluctuations in kaons Bedanga Mohanty

  33. MOTIVATION Chiral Symmetry is broken in ground state Possibility of it’s restoration for a hot and dense matter Through search for disoriented chiral condensates Study and detection of DCC : • Nature of chiral phase transition • Vacuum structure of strong interaction A.A. Anselm et al., PLB 261(1991) 482Rajagopal et al NPB 404 (1993)577 Bedanga Mohanty

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