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

ollisionsTapan K.Nayak for the WA98 Collab

oration

Nucl-ex/9909018

Centauro’s Signal

• Centauro events– Large numbers of hadr

ons

– Little apparent electromagnetic energy (no pi0)

– High hadronic pt 0.35+-0.15GeV

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

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)

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

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

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

N and Nch Correlation

• DCC model Model

• Hep-ph/9812434

– Baked Alaska model??

• Upper limit

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

Discrete wavelet technique

• Mother function & Father function

definition - phase space

Discrete wavelet technique

segmented

• Obtain FFC of function f

chlike

like

NN

Nf

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

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 assuming the fluctuations to be solely due to the presence of localized domains of DCC