A nlo analysis on fragility of dihadron tomography in high energy aa collisions
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A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions. Han-Zhong Zhang Institute of Particle Physics, Huazhong Normal University, China Co-authors: J. Owens E. Wang X.-N. Wang. Introduction Numerical analysis on single hadron and dihadron production Conclusions.

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A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions

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A nlo analysis on fragility of dihadron tomography in high energy aa collisions

A NLO Analysis on Fragility of Dihadron Tomography in High Energy AA Collisions

Han-Zhong Zhang

Institute of Particle Physics, Huazhong Normal University, China

Co-authors: J. Owens E. Wang X.-N. Wang

  • Introduction

  • Numerical analysis on single hadron and dihadron production

  • Conclusions

QuarkMatter2006

Nov. 18 , 2006


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

I. Introduction

leading

particle

hadrons

q

q

hadrons

leading particle

Leading particle suppressed

hadrons

q

q

hadrons

N-N collision

A-A collision

leading

particle suppressed

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Hard Probe Signal of QGP in RHIC and LHC

Jet quenching:

Induced by multiple scattering in QGP medium, a parton

jet will radiate gluon and lose its energy.

2


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

LO analysis of jet quenching in AA:

2→2 processes (tree level)

Jet quenching in 2→2 processes

A factor K=1.5-2 was put by hand to account for higher order corrections

3


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

Motivation :1) contribution for higher order correction?

2) find a robust probe of dense matter

QM 2006 Shanghai

Han-Zhong Zhang IOPP

NLO (Next to Leading Order ) corrections:

K is absent

One-loop corrections

Jet quenching in 2→3 processes

2→3processes (tree level)

(Jeff. Owens , PRD65(2002)034011;

B.W. Harris and J. Owens , PRD65(2002)094032)

4


Modified fragmentation function ff

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Modified Fragmentation Function (FF)

Jet Quenchingeffects lead to the modification of FF

KKP

(X. -N. Wang , PRC70(2004)031901)

where

and the averaged scattering number,

It determines the thickness of the outer corona where

a parton jet survives in the overlapped region.

5


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

In 1-demension expanding medium, the total energy loss:

The energy loss with detailed balance:

(Enke Wang and Xin-Nian Wang, PRL87(2001)142301)

An energy loss parameter

proportional to the initial gluon density

6


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

II. Numerical analysis on single hadron and dihadron production

1) fix scales and energy loss parameter

2) the centrality dependent of the

suppression factor

3) hadron contour plot

4) fragility of single and dihadron tomography

7


The invariant p t spectra of single hadron

QM 2006 Shanghai

Han-Zhong Zhang IOPP

The invariant p_T spectra of single hadron

p-p data at 200GeV are used to fix scales,

8


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

0-10% AuAu data at 200GeV are used to fix the energy loss parameter (proportional to the initial gluon density):

9


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Centrality Dependence

10


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

Single hadron is dominated by surface emission

y

emission surface

Single hadron

x

parton jet

coronathickness

QM 2006 Shanghai

Han-Zhong Zhang IOPP

completely suppressed

Color strength =single hadronyield from partons in the square

11


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

1.68

QM 2006 Shanghai

Han-Zhong Zhang IOPP

is a fragileprobe of dense matter.

loses its effectiveness

as a good probe of dense matter

Similar to the study by K. J. Eskola , H. Honkanen, C. A. Salgado,

U. A. Wiedemann, NPA747 (2005) 511-529

12


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

of dihadron in Au+Au collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

No jet quenching in d+Au,

Fit dAu data by pp result to fix scales,

Invariant mass

0.3

13


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

If no jet quen-ching,

14


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

PRL95(2005)152301

QM 2006 Shanghai

Han-Zhong Zhang IOPP

The ratio between the yield/trigger in AA and in pp:

If no jet quen-ching,

0.3

15


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

Dihadron is from surface emission + punch-through jets

N

y

triggered hadron

x

associated hadron

partonic di-jet

tangential

S

punch-through jets

25% left

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Color strength =dihadronyield from partons in the square

16


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

is a robust probe of dense matter.

1.68

QM 2006 Shanghai

Han-Zhong Zhang IOPP

at 200GeV

Trigger:8GeVat RHIC

17


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

is a robust probe of dense matter.

QM 2006 Shanghai

Han-Zhong Zhang IOPP

at 5.5TeV

LHC

Trigger:20GeVat LHC

18


Iii conclusions

1)

Because of the stronger quenching effects,

the single hadron is dominated by surface emission;

the dihadron is from surface emission + punch-through jets.

2)

The dihadron is more sensitive to the initial gluon density

than the single hadron . When becomes fragile in

higher energy AA, is a robust probe of dense matter.

3)

Without inputing K factor by hand, NLO results fit data well.

Because of the additional 2→3processes, NLO contributions

behave with stronger quenching effect than LO contributions:

QM 2006 Shanghai

Han-Zhong Zhang IOPP

III. Conclusions

19


Thank for your attention

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Thank for your attention!

谢谢!

20


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

is the differential 2-body or 3-body phase space element

QM 2006 Shanghai

Han-Zhong Zhang IOPP

The inclusive cross sections for single hadron production:

The inclusive cross sections for dihadron production:

is the squared matrix elements


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Hard sphere model


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

the formula of spectra inAA

QM 2006 Shanghai

Han-Zhong Zhang IOPP

nuclear modification factor


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

(Shi-Yuan Li and Xin-Nian Wang , PLB527(2002)85)

(Enke Wang and Xin-Nian Wang, PRL87(2001)142301)

(B. B. Back et al. [PHOBOS collaboration], PRC70(2004)021902)

QM 2006 Shanghai

Han-Zhong Zhang IOPP


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

Nuclear shadowing

effects only

in small pT region

So in large pT,

medium effects

only come from

Jet Quenching !!!


Invariant mass

Invariant mass:

How to fix scales:

If no medium effects,

QM 2006 Shanghai

Han-Zhong Zhang IOPP

(X. –N. Wang , PLB 595(2004)165


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

QM 2006 Shanghai

Han-Zhong Zhang IOPP

The dihadron azimuthal distributions


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

increases while decreases with collision energy.

RHIC

LHC

QM 2006 Shanghai

Han-Zhong Zhang IOPP

There are much more punch-through jets in higher energy AA

collisions,


A nlo analysis on fragility of dihadron tomography in high energy aa collisions

is a robust probe of dense matter.

QM 2006 Shanghai

Han-Zhong Zhang IOPP

at 5.5TeV

Trigger:20GeVat LHC


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