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Charge Fluctuations inπ+p and +p Collisions at 250GeV/c

Yuanfang Wu

1. Introduction

2. Results

• The dependency of charge fluc. on Y

• The dependency of charge fluc. on n

3. Summary

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1. Introduction

► Charge fluc. → a new signal of QGP PT

► Measures charge ratio fluc.:

net charge fluc.:

.,,

,)(

222

2

nnnRRRn

nR

RnRD

ch

ch

.,

,4)(

222

2

nnQQQQ

n

QQD

ch

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1. Introduction

► Theoretical predictions for D-measures Random: D(Q) ~ 4 Random: D(Q) ~ 4 HG: D(R) ~ 3 - 4HG: D(R) ~ 3 - 4 QGP : D(R) ~ 0.75 - 1QGP : D(R) ~ 0.75 - 1► Corrections

► Motivations • Which measure is better and if the corr. are proper?Which measure is better and if the corr. are proper? • Data on h-h collisions is absent.Data on h-h collisions is absent.

.

μC

yC

DD~

,2

2

μC,

totalch

Δych1

yC

yn

yn

n

n

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1.1. Introduction Introduction

► DataData :

π+ p and π+ p and + p Collisions at 250GeV/c+ p Collisions at 250GeV/c ( NA22 Coll. )( NA22 Coll. )

A total of 44 524 NSD events 0.001GeV/c < p0.001GeV/c < ptt < 10 GeV/c < 10 GeV/c full 4π acceptance full 4π acceptance

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2. Results • The dependency of the fluc. on Y

1) & 2) &

3) &

)(QD )(~QD

)(~ RD

)( RD )(~ RD

)( RD

n

nR

n

nR

yyy cut

,

2/||

)(QD )( RD )( RD

)(~QD )(

~ RD )(~ RD

y

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2. Results • nch dis. for diff. |y| < ycut

1) |y|<2, even & odd

are the same.

2) |y|<2.5, even & odd

start to separate.

It first happens at

large nch.

3) full range, only

even left.

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2. Results • The dependency of the fluc. on nnchch at |y| < 2.5

)(QD )( RD )( RD

)(~QD )(

~ RD )(~ RD

chn

chn

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2. Results • The dependency of the fluc. on nch at |y|<3

)( RD )( RD)(QD

)(~QD )(

~ RD )(~ RD chn

chn

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3. Summary

☺ ☺ and both have strong and both have strong ΔΔy dependencey dependence..

☺☺ in diff. in diff. ΔΔy are much smaller than those of y are much smaller than those of random and HG, but pass through the band of random and HG, but pass through the band of QGP . QGP . stays between the bands of HG and QGP and stays between the bands of HG and QGP and show no show no ΔΔy dependence at large y dependence at large ΔΔy. y.

☺☺ The and develop a peak with increasing The and develop a peak with increasing of of ΔΔy, lying partly in the bands for a HG and a QGP, y, lying partly in the bands for a HG and a QGP, respectively, but their corrected versions always aboverespectively, but their corrected versions always above the band for the HG and keep increasing with the size the band for the HG and keep increasing with the size of of ΔΔy.y.

)(QD

)(~QD

)( RD )( RD

)(QD

)(RD

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3. Summary

☺ ☺ and both have nand both have nchch dependence dependence..

☺☺ has better record in net charge fluc. between has better record in net charge fluc. between even and odd neven and odd nchch than the charge ratio ones. than the charge ratio ones.

☺☺ smear the existent differences between even smear the existent differences between even

and odd charged and odd charged nnch,ch, while the make their while the make their nnchch dependence disappear within experimental errors.dependence disappear within experimental errors.

☺☺PYTHIA can reproduce the net charge and charge PYTHIA can reproduce the net charge and charge

ratio fluc. in different Yratio fluc. in different Ycut cut and for different and for different nnchch. . However, PYTHIA over-estimates the fluc. of odd However, PYTHIA over-estimates the fluc. of odd nnchch at |y|<3.at |y|<3.

)(QD

)(~QD

)(~RD

)(QD )(RD