Quark quark double scattering in nuclei with twist expansion approach
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Quark-quark double scattering in nuclei with twist expansion approach. Ben-Wei Zhang 1. Texas A&M University, USA 2. Central China Normal University, China. Based on the work in collaboration with X.-N. Wang and A. Schaefer. Outline. Introduction

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Quark quark double scattering in nuclei with twist expansion approach

Quark-quark double scattering in nuclei with twist expansion approach

Ben-Wei Zhang

1. Texas A&M University, USA

2. Central China Normal University, China

Based on the work in collaboration with X.-N. Wang and A. Schaefer


Outline
Outline

  • Introduction

  • Modified FF due to quark-quark scattering with twist expansion approach

  • Multiplicity ratios of hadrons in nuclei

  • Summary


parton

hadrons

ph

E

Jet Quenching

Jet quenching has been observed as a new nuclear phenomenon at RHIC

X.N. Wang, Nucl.Phys. A750 (2005) 98


Quark quark double scattering
Quark-Quark Double Scattering

  • Two kinds of double scattering in eA DIS

quark-gluon

double scattering

quark-quark

double scattering

X.F. Guo, X.N. Wang, PRL85,3591(2000)


Properties of q q double scattering
Properties of q-q double scattering

X.N. Wang and X.F. Guo, NPA 696, 788 (2001)

  • Quark-quark double scattering will mix the quark and gluon fragmentation functions;

    Jet conversion;

  • Quark-quark double scattering may give different modifications to quark FF and anti-quark FF.

W. Liu, C.M. Ko, B.W. Zhang, nucl-th/0607047

B.W. Zhang, X.N. Wang, A. Schaefer, in preparation


Generalized factorization
Generalized Factorization

Consider a typical quark-quark

double scattering process in

semi-inclusive eA DIS:

J. Qiu,G. Sterman, NPB 353(1991)105; NPB 353(1991)137


Interference effect
Interference effect

interference effect


Other processes
Other processes

lowest order

without radiation

……

……


Quark quark double scattering1
Quark-quark double scattering

  • Single Scattering: leading twist contribution

  • Double Scattering: twist-4 contribution


Modified fragmenation function
Modified Fragmenation Function

  • Summing single and double scattering gives

  • We define the modified quark FF as:


Quark quark correlation function
Quark-quark correlation function

M. Luo, J. Qiu,G. Sterman, PRD 50(1994)1951.

J. Osborne and X.N. Wang, NPA 710(2002)281.


Quark and anti quark ff i
Quark and anti-quark FF(I)

  • We get the modification to quark FF as:

  • Similarly we can obtain

    modification to

    anti-quark FF.


Quark and anti quark ff ii
Quark and anti-quark FF(II)

  • The difference between modified quark FF and modified anti-quark FF:


Multiplicity ratios of hadrons
Multiplicity ratios of hadrons

  • Multiplicity ratio measured at HERMES:

HERMES

hep-ex/0012049

hep-ex/0307023


Theoretical explanation
Theoretical explanation

  • In the constituent quark model:


Summary
Summary

  • Quark-quark scattering is eA DIS are studied with twist expansion approach

  • Modification to quark FF in nuclei is different from the modification to anti-quark FF in nuclei.

  • This difference may explain the multiplicity ratios of hadrons in nuclei observed at HERMES.


Summary cont
Summary (cont.)

  • Quark-quark double scattering can modify fragmentation functions without radiation.

  • Quark-quark double scattering may change the flavor of partons: jet conversion

  • In heavy-ion collisions quark-quark double scattering can not be neglected if quark density is comparable to gluon density in hot nuclear medium.


Thank you!

谢谢!




Hard partonic part
Hard partonic part

  • Semi-inclusive hadronic tensor can be given:


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