# Presentation: 149116

## Two particle correlations in the Glasma & the Ridge 

**Raju Venugopalan**
**Brookhaven National Laboratory**

**AGS users meeting, May 27th, 2008**

## For particles to have been emitted from the same 

**For particles to have been emitted from the same **
**Event Horizon****, causality dictates that **

**If **Y **is as large as (especially) suggested by**
**PHOBOS, correlations were formed very early**
**- in the Glasma...**

## An example of super horizon fluctuations...

## Big Bang

**Big Bang**

- CGC/
- Glasma

- QGP

**Little Bang**

- WMAP data
- (3x105 years)

**Inflation**

**Hot Era**

- Plot by T. Hatsuda

##  Glasma 

**Glasma (\Glahs-maa\):**** **
***Noun:**** ***non-equilibrium matter **
**between Color ****Glass**** Condensate (CGC)**
**& Quark Gluon Plas****ma**** (QGP)**

**Ludlam, McLerran, Physics Today (2003****)**

## After a HI collision, classical fields form a 

**After a HI collision, classical fields form a **
**Glasma flux tube**** with *****longitudinal chromo E & B fields***

**Typical size of flux tube **
**in transverse direction is **
**1 / Q****S ****< 1/********QCD**

**Lappi, McLerran, NPA772 (2006) **

**Systematic framework for **
**multi-particle production in the Glasma**
** ****- Gelis, Lappi, RV, arXiv:0804.2630**

## QCD vacuum and sphaleron transitions

**Vacua labeled by different **
**Chern-Simons # ******

**“****Over the barrier”**** sphaleron transitions can change the **
**topological charge in an event => the index theorem tells us that **
**this induces a induce a net chirality. **

**E****B**

**Kharzeev, Krasnitz, RV, Phys. Lett. B545 (2002)**

## Two particle correlations in the Glasma 

**Can it explain the near side ridge ?**

## 2 particle correlations in the Glasma (I)

- +

- =

**Leading (classical) contribution**

**Note:** *Interestingly, computing leading logs to all orders, both *
*diagrams can be expressed as the first diagram with *
*sources evolved a la JIMWLK Hamiltonian*

**Gelis, Lappi, RV (2008)**

**Dumitru, Gelis ,McLerran, RV, arXiv:0804.3858[hep-ph]]**

## 2 particle correlations in the Glasma (II)

**Leading color “topologies”:**

**“****single diffractive”**

**“****interference” graph**

## 2 particle correlations in the Glasma (III)

**Suppressed color “topologies”:**

**“****single diffractive”**
**(emission from different **
**quark lines in amp. and **
**complex conjugate amp.)**

**“****double diffractive”**

## 2 particle spectrum (II)

**Simple “Geometrical” result:**

** ******** ****4 (more accurate result requires numerical **
**soln. of YM eqns. - in progress.**

**with K_N ******** 0.3 **

## 2 particle spectrum (III)

**Particle emission from the Glasma **
**tubes is ****isotropic**** in the azimuth**
**Particles correlated by ****transverse flow**** (or at high p****T**** by **
**opacity effects)  are highly localized transversely**
**- experience same ****transverse boost**

**Voloshin, Shuryak**
**Gavin, Pruneau, Voloshin**

## 2 particle spectrum...

**Centrality dependence of V****r**** from blast wave fits**
**Centrality dependence of Q****S**** a la Kharzeev-Nardi**

## Ridge from flowing Glasma tubes

**K****N**** ~ 0.1**

**(energy & centrality dep.**
**of flow parametrizaton **
**courtesy of  P.Sorensen)**

**Gets many features right:**
**i) Same flavor composition as bulk matter**
**ii) Large multiplicity (1/3****rd****) in the Ridge relative to the bulk**
**iii) Ridge independent of trigger p****T****-geometrical effect**
**iv) Signal for like and unlike sign pairs the same at large ******

**STAR **
**preliminary**** **

## Ridge from flowing Glasma tubes

**Angular dist. **
**appears to require larger boosts,**
**or absorption by medium **
**a la Shuryak**

**Caveat:**

**Blast wave picture may be too simplistic - need more **
**accurate description of transverse flow profile**

## SUMMARY

**Long range rapidity correlations are **
**   ****formed early - in the Glasma**
**Multi-particle emission from radially flowing Glasma flux tubes provide a dynamical picture of the ridge. **
**The analysis can be improved by better treatment of I) transverse flow & **
**   ****II) rapidity evolution of rapidity interval between the pairs**

## EXTRA SLIDES

## Some possible ridge explanations

- New approaches used in to attempt to disentangle
-  System size dependence
-  Identified particle correlation
-  Di-hadron correlation with respect to reaction plane
-  3-particle correlation

- QCD bremsstrahlung radiation boosted
- by transverse flow
- S.A.Voloshin, Phys.Lett.B. 632(2007)490
- E.Shuryak, hep-ph:0706.3531

- Broadening of quenched jets in turbulent color fields
- A.Majumder et.al
- Phys. Rev. Lett.99(2004)042301

- Recombination between thermal and shower partons  at intermediate pT
- R.C. Hwa & C.B. Chiu
- Phys. Rev. C 72 (2005) 034903

- In medium radiation and longitudinal flow push
- N.Armesto et.al Phys.Rev.Lett.
- 93(2007) 242301

- Momentum Kick Model
- C.Y. Wong  hep-ph:0712.3282