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Search for Disoriented Chiral Condensates in 158AGeV Pb+Pb C
ollisionsTapan K.Nayak for the WA98 Collab
orationNucl-ex/9909018
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Centauro’s Signal
• Centauro events– Large numbers of hadr
ons– Little apparent electro
magnetic energy (no pi0)
– High hadronic pt 0.35+-0.15GeV
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Centauro’s event candidates
• Cosmic ray– 5 + 2 candidates in Bra
zil-Japan collaboration in Bolivia
– 1 candidate in Pamir emulsion chanmber ex
– Anti-Centauro candidate from JACEE coll
5 Centauro’s candidate
Anti-Centauro candidate
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No Centauros
• Cosmic ray– No centauros in emulsion chamber at Kanbala, at Mt.Fuj
i.– China-Japan coll, upperlimit 3%(>100TeV,95%CL)
• Accelarator– CERN UA5 etc : negative results up to sqrt(s)=900GeV– FERMILAB MINIMAX(T864)
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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.
NNN
Nf
0
0
N/n/1!1N22!n
!n22!NN,nP
n22
N22
0aaa2CN2
0
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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(MIR
AC)– Common coverage of PMD and SPMD was considerd
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N and Nch Correlation– hep-ex/9802019
• Event by event analy– N and Nch– Correlation axis(Z) has bee
n obtained by fitting by second order polynomial.
– Closest distance(Dz) has been calculated numerically
• Dz represents the relative fluctuation of N and Nch
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N and Nch Correlation• DCC model
Model• Hep-ph/9812434
– Baked Alaska model??• Upper limit
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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
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Discrete wavelet technique
• Mother function & Father function
definition - phase space
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Discrete wavelet technique
segmented
• Obtain FFC of function f
chlike
likeNN
Nf
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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
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Conclusion
• Two independent ana of - phase space– Presence of non statistical fluctuations– This could be effected by many different physic
s effects• Attempts are being made to explain this ass
uming the fluctuations to be solely due to the presence of localized domains of DCC