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

MOTIVATION Possibility of it’s restoration for a hot and dense matter 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

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

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

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

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

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

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

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

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

Fi = <N(N-1)…(N-i+1)> / <N>i 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

EVENT SHAPE ANALYSIS Uses flow technique to look for DCC 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

-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

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

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

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

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

NUCLEON-NUCLEON  MINIMAX RESULTS T.C. Brooks et al., (MINIMAX Collab.) Phys. Rev. D 61 (2000) 032003 R(1,1) 1.026  0.004 R(2,1) 1.035  0.010 R(3,1) 1.059  0.027 R(4,1) 1.118  0.065 R(5,1) 1.310  0.151 R(6,1) 1.904  0.382 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

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

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

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

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

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

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

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

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

Correlation due to contamination masks signal 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

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

POSSIBILITIES - II Better to analyze events with higher f values 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

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

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

SUMMARY Look for PHOTON excess events, within different pT regions Experiment Collaboration CM Energy Search Region (η,φ) 1980 Mt. Chacaltaya Brazil-Japan √s≧1.7 TeV ------------ 1992 Balloon JACEE 5.0<η<9.0 ⊿φ<2π 1991 Mt. PAMIR PAMIR -------- ------ 1982 SPPS UA5 √s=540 GeV |η|<5.0 1983 UA1 |η|<3.1 1986 √s=900 GeV 1996 TEVATRON CDF √s=1.8 TeV |η|<4.2 ,⊿φ<2π 1997 MINIMAX 3.4<η<4.2 1998 SPS WA98 √s=3.5 TeV (Pb+Pb) 2.90<η< 3.75 ⊿φ<π 2001 RHIC PHENIX √s=39.4 TeV (Run2) (Au+Au) |η| < 0.35 ⊿φ<1/2π (×2 arm) 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

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) 482 Rajagopal et al NPB 404 (1993)577 Bedanga Mohanty