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Search for Disoriented Chiral Condensates in 158AGeV Pb+Pb Collisions

Investigating the presence of disoriented chiral condensates in Pb+Pb collisions at 158 AGeV using WA98 data analysis. The study focuses on Centauro events, chiral symmetry breaking, pi0 ratios, Nγ and Nch correlations. Various techniques such as wavelet analysis are employed to study non-statistical fluctuations in the data.

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Search for Disoriented Chiral Condensates in 158AGeV Pb+Pb Collisions

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  1. Search for Disoriented Chiral Condensates in 158AGeV Pb+Pb Collisions Tapan K.Nayak for the WA98 Collaboration Nucl-ex/9909018

  2. Centauro’s Signal • Centauro events • Large numbers of hadrons • Little apparent electromagnetic energy (no pi0) • High hadronic pt 0.35+-0.15GeV

  3. Centauro’s event candidates 5 Centauro’s candidate • Cosmic ray • 5 + 2 candidates in Brazil-Japan collaboration in Bolivia • 1 candidate in Pamir emulsion chanmber ex • Anti-Centauro candidate from JACEE coll Anti-Centauro candidate

  4. No Centauros • Cosmic ray • No centauros in emulsion chamber at Kanbala, at Mt.Fuji. • China-Japan coll, upperlimit 3%(>100TeV,95%CL) • Accelarator • CERN UA5 etc : negative results up to sqrt(s)=900GeV • FERMILAB MINIMAX(T864)

  5. Disoriented Chiral Condensates • Cantauros event’s source ??? • Chiral symmetry • Chiral symmetry is broken when hadronization. • Pi0 to total pi ratio • Pi = isospin zero • Binominal distribution • largeN -> Gaussian dist • HI collisions • Rapid expansions in the longitudinal direction leads domains of the unconventionally oriented vacuum configuration.

  6. WA98 Experiment • Silicon Pad Multiplicity Detector(SPMD) • 32.8cm downstream • 2.35<  < 3.75 • Photon Multiplicity Detector(PMD) • 21.5m downstream • 2.9<  < 4.2 • Plastic scinti + 3X0 lead conveter, 28segment • 66k central events • 5% central determined by midrapidity calorimeter(MIRAC) • Common coverage of PMD and SPMD was considerd

  7. N and Nch Correlation • hep-ex/9802019 • Event by event analy • N and Nch • Correlation axis(Z) has been obtained by fitting by second order polynomial. • Closest distance(Dz) has been calculated numerically • Dz represents the relative fluctuation of N and Nch

  8. N and Nch Correlation • DCC model •  Model • Hep-ph/9812434 • Baked Alaska model?? • Upper limit

  9. N and Nch Correlation • Smaller  segmented into 2,4,8,16bins • Broader distribution of Sz • Fig1(b), the rms deviations of data differ significantly(???) • This is non-statistical fluctuations for bin sizes>45deg

  10. Discrete wavelet technique • Mother function & Father function •  definition • - phase space

  11. Discrete wavelet technique •  segmented • Obtain FFC of function f

  12. Discrete wavelet technique • 2,4,8,16 resolution scale • J=3,4 consistent • J=1,2 clear difference from mixed event and Venus+Geant • FFC(j=3,4) is obtained from FFC(j=1,2) • Difference is due to the fluctuations

  13. Conclusion • Two independent ana of - phase space • Presence of non statistical fluctuations • This could be effected by many different physics effects • Attempts are being made to explain this assuming the fluctuations to be solely due to the presence of localized domains of DCC

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