Anomaly of over ratios in Au+Au collision with jet quenching Xiaofang Chen IOPP, CCNU Collaborator: Enke Wang Hanzhong Zhang Benwei Zhang Beijing Mar

Anomaly of over ratios in Anomaly of over ratios in Au+Au collision with jet quenchingAu+Au collision with jet quenching

p

Xiaofang ChenXiaofang Chen IOPP, CCNU

Collaborator: Enke Wang Hanzhong Zha

ng Benwei Zhang

Beijing Mar. 22-24Beijing Mar. 22-24IOPPIOPP 11

Outline Outline

The introduction of single hadron The introduction of single hadron spectrum in NLO PQCD spectrum in NLO PQCD

The anomaly of and The anomaly of and ratios and the two reasons for thatratios and the two reasons for that

/p /p

Summary and discussionSummary and discussion

IOPPIOPP Beijing Mar. 22-24Beijing Mar. 22-24 22

Jet quenching:

Induced by multiple scattering in QGP medium, a partonjet will radiate gluon and lose its energy.


2 22

0 2( ) ( )

( )

( , ) ( , )

( , )( )ˆ

hpp

a b a p a b p babcdT

h c d c d

c d

dK dx dx f x Q f x Q

dp dy

D z Qdab cd

dt z

Invariant Cross Sections in pp collision

LO (Leading order) :

One-loop corrections2→3 processes (tree level)2→2 processes (tree level)

NLO (Next to Leading Order ) corrections:

Parton distribution function

CTEQ,MRS

Parton fragmentation function

BKK,KKP,AKK

A factor K=1.5-2 was put

A factor K is no longer needed


We use AKK fragmentation function

X.F. Zhang and G. Fai, Phys. Rev. Lett. 89, 272301 (2002)

Considering the shortage of fragmentation function,we introduce a phenomenological multiplication factor to the production of proton.


2 2 2 22

2( ) ( ) ( )

( )

( ) ( , , ) ( , , )

( , , )( )ˆ

hAA

A A a b a A a b A babcdT

h c d c d c d

c d

dK d bd rt r t r b dx dx f x Q r f x Q r

dp dy

D z Q Edab cd

dt z

Invariant Cross Sections in AA collision

2 22

3( ) 1

2A

At r r R

R

Nuclear thick functionModified parton distribution function

2 2 2/( , , ) ( , ) ( , ) 1 ( , )a A a A a p a n

Z Zf x Q r S x r f x Q f x Q

A A

Modified fragmentation functions

Due to jet quenching

Jet quenching in 2 2 and 2→3 processes

S.Y. Li and X.N. Wang , Phys. Lett. B527,85(2002).


''/2 0 ' 2 0 ' 2( , , ) (1 )[ ( , ) / ( , )]

/ / /

/ 0 2( , )/ C

zzL gcD z Q E e D z Q L D z Qh c c c h c c h g gz z

c cL

e D z Qh c

,//),/( ''cTgcTcTc EpLzEppz Wher

e,The energy loss of final parton jet

),,,(0

000

nrb

dLg

L

the averaged scattering number,


|)],(|)([2

),,(2

00 rbtrtA

Rrb AA

Ag

0

0

0

1 0 0

( , , )L

gd

dEE d b r n

dL

)/5.7/()6.1/( 02.1

001

EEdL

dE

d

the gluon density distribution,

In 1-demension expanding medium, the total energy loss is written as a path integration:

The energy loss per unit length with detailed balance:(Enke Wang and Xin-Nian Wang, PRL87 (2001) 142301)

An energy loss parameter proportional to the initial gluon density

00


min max

2 2min max

( , )1

,

hhAAAA

AAT in T

d b bdN

dp dy b b dp dy

( ) 2min max( , ) 1

NNin ABT bAB

in b b e d b

2

2

/

/AB T

AB

binary NN T

d dyd pR

N d dyd p

2 2bin A AN db dr t r t r b

1ABR

1ABR

No Medium Effect

Medium Effect

Nuclear Modification Factor:




production rate is dominated by quark jets at high production rate is dominated by quark jets at high and by gluon jet at low ;while and by gluon jet at low ;while

production production rate is dominated by gluon jets both in low and high rate is dominated by gluon jets both in low and high

. .

( ) / 2 ( ) / 2p p

TpTp

Tp


Data from STAR collaboration have indicated that and Data from STAR collaboration have indicated that and ratios at high in central Au+Au collisions approach ratios at high in central Au+Au collisions approach

those in p+p and d+Au collisions. These observations indicate that, atthose in p+p and d+Au collisions. These observations indicate that, athigh ,fragmentation in central Au+Au and p+p events is similar and there high ,fragmentation in central Au+Au and p+p events is similar and there

is no evidence of different energy loss for quarks and gluons in the medium. is no evidence of different energy loss for quarks and gluons in the medium.

/p /p

Tp

ATAR Collaboration, J. Adams et al. Phys. Rev. Lett. 97, 152301 (2006)ATAR Collaboration, J. Adams et al. Phys. Rev. Lett. 97, 152301 (2006)

Tp

In order to differentiate and ,we think come from gluon and quark, come from gluon and antiquark .

pp pp


Recent studies have shown that elastic scattering of quark and gluon jetsRecent studies have shown that elastic scattering of quark and gluon jets in the QGP also leads to an appreciable loss of their energies.in the QGP also leads to an appreciable loss of their energies.

S. Wicks, W. Horowitz, M. Djordjevic, and M. Gyulassy, Nucl. Phys. A784,426 (2007)S. Wicks, W. Horowitz, M. Djordjevic, and M. Gyulassy, Nucl. Phys. A784,426 (2007) M.G. Mustafa, Phys. Rev. C 72, 014905 (2005)M.G. Mustafa, Phys. Rev. C 72, 014905 (2005)

Another forms of energy loss maybe exist in the process when parton jetsAnother forms of energy loss maybe exist in the process when parton jets propagate through the QGP medium. propagate through the QGP medium.

The energy loss is calculated in the state The energy loss is calculated in the state of equilibrium ,but the QGP may be in non-equilibriumof equilibrium ,but the QGP may be in non-equilibrium..





Different and ratios due to equal energy losses of gluons and quarksDifferent and ratios due to equal energy losses of gluons and quarks/p /p

qq gg q q g gq qInelastic scattering: elastic scattering:

Flavor conversion :

Quark and gluon jets traversing through a quark-gluon plasma not only lose their energy but also can undergo flavor conversion.

X.N. Wang and X. Guo, Nucl. Phys. A696, 788(2001);B.W. Zhang, X.N. Wang, and A. Schafer,ibid. A783551(2007)


W. Liu , C.M. Ko, and B.W. Zhang PRC75, 051901(2007)

We find that conversionsWe find that conversions between quark and gluon jets between quark and gluon jets indeed lead to an increase in the final number of gluon jets indeed lead to an increase in the final number of gluon jets

in central heavy ion collisions than in the case without conversions.in central heavy ion collisions than in the case without conversions.

Arxiv: 0801.0453v1 W. Liu and R. J FriesArxiv: 0801.0453v1 W. Liu and R. J Fries Jet flavor conversions reduce the numberJet flavor conversions reduce the number

of high transverse momentum quark jets by 30%.of high transverse momentum quark jets by 30%.



Different and ratios due to flavor conversionDifferent and ratios due to flavor conversion/p /p

The AKKThe AKK fragmentation functions show that gluon fragmentation cfragmentation functions show that gluon fragmentation contribute to 40% of pion production at while more than 8ontribute to 40% of pion production at while more than 80% of proton are from gluon fragmentation. (0% of proton are from gluon fragmentation. (S. Albino,B.A. Kniehl and G. KramS. Albino,B.A. Kniehl and G. Kram

er. Nucl.Phys. B725,181(2005)er. Nucl.Phys. B725,181(2005) ) )

10Tp Gev




Summary and discussionSummary and discussion

We investigate the consequence if gluons lose the same We investigate the consequence if gluons lose the same amount of energy in QGP as quarks and demonstrate that amount of energy in QGP as quarks and demonstrate that it will enhance the and ratios for central Au+Au it will enhance the and ratios for central Au+Au

collision.collision./p /p

We explore the effect of strong jet conversion where a nWe explore the effect of strong jet conversion where a net of quark-to-gluon conversion also result in similar et of quark-to-gluon conversion also result in similar

and ratios in central Au+Au and p+p collisions and ratios in central Au+Au and p+p collisions/p /p

The exploration presented here is a phenomenological The exploration presented here is a phenomenological one and why the energy losses of quarks and gluons are eone and why the energy losses of quarks and gluons are equal or a strong jet conversion happened in Au+Au collisqual or a strong jet conversion happened in Au+Au collis

ion still need further intense theoretical investigate.ion still need further intense theoretical investigate.

Thank you!Thank you!

Documents

Anomaly of over ratios in Au+Au collision with jet quenching Xiaofang Chen IOPP, CCNU Collaborator: Enke Wang Hanzhong Zhang Benwei Zhang Beijing Mar