# Presentation: 468658

## Charm in p(d)-A Collisions: E866/FNAL & PHENIX

**Mike Leitch - Los Alamos National Laboratory**
**For E866/NuSea & the PHENIX Collaboration**
***leitch@lanl.gov***

***PHENIX Muon Meeting, Santa Fe, June 16-18, 2003***

** ****Gluon shadowing & energy loss in nuclei**
** ****J/******** production mechanisms & absorption**
** ****Cronin effect (p****T**** broadening)**
** ****PHENIX measurements and charm in d-Au**
** ****Summary**

## Physics Issues in heavy-quark production in nuclei - Shadowing

-  **Shadowing** of gluons  depletion of the small x gluons
-  Very low momentum fraction partons have large size, overlap with neighbors, and fuse to thus enhancing higher population at higher momenta at the expense of lower momenta
-  Or, coherent scattering resulting in destructive interference for coherence lengths longer than the typical intra-nucleon distance

## Nuclear Dependence of charm in E866

**open charm: no A-dep**
**at mid-rapidity**

**Donald Isenhower, Mike Sadler, Rusty Towell, Josh Willis *****Abilene Christian***
**Don Geesaman, Sheldon Kaufman, Bryon Mueller *****ANL***
**Chuck Brown, Bill Cooper *****FNAL***
**Gus Petitt, Xiao-chun He, Bill Lee**** *****Georgia State***
**Dan Kaplan **** *****IIT***
**Tom Carey, Gerry Garvey, Mike Leitch, Pat McGaughey, Joel Moss, Jen-Chieh Peng, Paul Reimer, Walt Sondheim *****LANL***
**Mike Beddo, Ting Chang, Vassili Papavassiliou, Jason Webb**** *****New Mexico St.***** **
**Paul Stankus, Glenn Young **** *****ORNL***
**Carl Gagliardi, Bob Tribble, Eric Hawker, Maxim Vasiliev *****Texas A & M***** **
**Don Koetke *****Valparaiso***

_**Nuclear Dependence of charm in E866**_

## Gluon Shadowing – Largely Unknown

_**Gluon Shadowing – Largely Unknown**_

***Kopeliovich, Tarasov, & Hufner***
***hep-ph/0104256***

***Eskola, Kolhinen, Vogt hep-ph/0104124***

- PHENIX μ+μ-  (Au)

**Gluon shadowing for J/****Ψ’s in**** PHENIX ****μ acceptance****; large uncertainty:***** ***
***Eskola...***** : ~ 0.8 vrs *****Kopeliovich...***** : ~ 0.4**
** ****Must be measured**

**PHENIX ****μ**
**PHENIX ****e**
**E866 (*****Y*****~0)**

**Eskola**

**Kopeliovich**

**Shadowing (only) for d+Au -> J/******

## J/ at fixed target: Absorption at mid-rapidity

- Significant nuclear dependence of cross section is observed
- Power law parameterization  =  A
-  = 0.92		(E772, PRL _66 _(1991) 133) (limited pT acceptance bias)
-  = 0.919 ± 0.015 	(NA38, PLB _444 _(1998)516)
-  = 0.954 ± 0.003	(E866 @ xF=0. PRL _84 _(2000),3258 )
-  = 0.934 ± 0.014	(NA50, QM2001)
- Absorption model parameterization
- = 6.2 mb (NA38/50/51) to 4.4 mb (NA50, QM2002)
- Small difference in  between J/ and (2S) (E866)
- (J/) – (S) ~ 0.02-0.03 @ xF = 0

## What might be expected for alpha for mid-rapidity J/Psi's at RHIC?

**From our measurements at FNAL and those at NA38/50 we see (taking a rough average),**
**             ****alpha = 0.94**
**Now if we believe there is strong anti-shadowing in the x2=0.1 region, as shown by Eskola and used also by Kopeliovich; then the FNAL and CERN experiments are in this range and their alpha values are larger due to this anti-shadowing. So lets ****take out this anti-shadowing**** from alpha and see what's left over,**
**             ****R(Au/d) = (197/2)^(alpha-1) = (197/2)^(0.94-1) = 0.76**
**then Eskola anti-shadowing in the ratio is about 1.15, so**
**             ****R(Au/d)[w/o anti-shad] ~ 0.66   and alpha[w/o anti-shad] = 1 + (ln(R)/ln(A/d)) ~ **_**0.91**_
**i.e. the ****effective alpha for J/Psi without anti-shadowing**** from the FNAL and CERN experiments is about 0.03 lower.**
**Then at RHIC energies for ****central rapidity Eskola predicts little or no shadowing, so this alpha = 0.91**** would be the expectation if this is true (no shadowing at central rapidity)**
**On the other hand, Kopeliovich predicts a reduction in the gluon density at x2 ~ 1.5e-2 (about where e+e- J/Psi's are for us) to about 0.75. So for Kopeliovich shadowing we would get for central rapidity,**
**                 ****R(Au/d)[Kopeliovich,y=0] ~ (0.66)(0.75) = 0.50   or alpha = 0.85**
**For the numbers above, the ****difference between no shadowing and "Kopeliovich“ shadowing**** is 0.91 -> 0.85 in alpha, or ****0.66 -> 0.50 in the Au/d ratio at mid-rapidity****. **
**At ****forward rapidity (i.e. for J/Psi -> mu+mu-)**** the effect should be much stronger, with Eskola showing a reduction in the gluons to about 0.80 and Kopeliovich to about 0.40, i.e.,**
**Eskola: R(Au/d)(mu+mu-) ~ (0.66)(0.80) = 0.53   or alpha ~ 0.86**
**Kopeliovich: R(Au/d)(mu+mu-) ~ (0.66)(0.40) = 0.26   or alpha ~ 0.71**

## Energy loss of gluons in nuclei

**Kopeliovich, Tarasov, Hufner**
**Nucl.Phys. A696 (2001) 669-714**
**(hep-ph/0104256)**

_**Energy loss of gluons in nuclei**_

- Energy loss of incident parton shifts effective xF  and produces nuclear suppression which increases with xF

## Gavin & Milana Energy Loss (from R. Vogt, hep-ph/9907317)

_**Gavin & Milana Energy Loss **_**(from R. Vogt, hep-ph/9907317)**

## PT Broadening at 800 GeV

_**P**__**T**__** Broadening at 800 GeV**_

- (pT) shape is independent of xF & same for NA3 at a lower energy
- (curves are                                                   with *A* slightly different for each)

**E772 & E866: p-A at 800 *****GeV***

**Drell-Yan**

**J/******** & ********’**

**Upsilons**

## Systematics of PT Broadening 

## Feeding of J/Ψ’s from Decay of Higher Mass Resonances

***E705 @ 300 GeV/c, PRL ***_***70***_***, 383 (1993)***

-  Large fraction of J/Ψ’s are not produced directly

-  Nuclear dependence of parent resonance, e.g. χC is probably different than that of the J/Ψ
-  e.g. in proton production ~30% of J/Ψ’s will have effectively stronger absorption because they were actually more strongly absorbed (larger size) χC’s while in the nucleus

|  | Proton | Pion |
| --- | --- | --- |
| χ,1,2  J/Ψ | 30% | 37% |
| Ψ ́  J/Ψ  | 5.5% | 7.6% |

| Meson | M(GeV) | R(Fm) | BE
(MeV) |
| --- | --- | --- | --- |
| J/Ψ | 3.1 | .45 | ~640 |
| Ψ ́ | 3.7 | .88 | ~52 |
| χC | 3.5 | .70 |  |

## Open Charm Nuclear Dependence : xF Dependence?

*WA82 340 GeV ****- *
*PRB *_*284*_*,453 (1992)*

- Open charm has little or no nuclear dependence
- 	 = 1.00± 0.05 		(E769  250GeV +A)
- 	 = 0.92 ±0.06		(WA82 340GeV +A)
- 	 = 1.02 ±0.03 ±0.02	(E789 800GeV p+A)
- This is consistent with that there being little nuclear shadowing in the x region probed by the fixed target charm experiments.
- Significant nuclear suppression is reported in large xF region (WA78, =0.81 ± 0.05). This could be due to nuclear shadowing in small x (large xF), but this is not well understood.
- At RHIC, we can probe x values much smaller than for fixed target and may observe nuclear shadowing effect in charm production.

_**Open Charm Nuclear Dependence : x**__**F**__** Dependence?**_

## Motivation
Mainly produced from gluon fusion  sensitive to initial gluon density and gluon distribution.
Energy loss when propagating through dense medium.
Baseline measurement for charmonium suppression.
A silicon vertex detector would allow direct measurement via the displaced vertex, but for now we rely on the semi-leptonic decay modes.

- Mainly produced from gluon fusion  sensitive to initial gluon density and gluon distribution.
- Energy loss when propagating through dense medium.
- Baseline measurement for charmonium suppression.
- A silicon vertex detector would allow direct measurement via the displaced vertex, but for now we rely on the semi-leptonic decay modes.

- Open Charm Measurements

- K+

- -

- 

- e+

**D*****0**

********

## New results from the PHENIX muon and electron arms for d-Au collisions are beginning to come out from this years data and should shed light on the question of shadowing for gluons, as well as provide a baseline for high-luminosity Au-Au measurements in the next RHIC run.

**(Comparison of North and South J/******** yields not instructive at this stage since we are only beginning to study efficiency issues which could have large effects and the data samples are not identical)**

- Dimuon Mass (GeV/c)

- ~ 232 J/’s
-  = 164 MeV

- South Muon Arm

-  ~ 356 J/’s
-  = 145 MeV

- Dimuon Mass (GeV/c)

- North Muon Arm

## North

- Muon Arm

- South
- Muon Arm

**FAKE data points to illustrate statistical power of d-Au data just taken**
**(there will be additional systematic uncertainties)**

## Centrality Dependence with expected statistics & Vogt calculations

**FAKE data points to illustrate statistical power of d-Au data just taken**
**(there will be additional systematic uncertainties)**

**Centrality Dependence with expected statistics & Vogt calculations**

## Centrality dependence of absorption in simple Eikonal picture from Lars Gerland (for p-A)

**Centrality dependence of absorption in simple Eikonal picture from Lars Gerland (for p-A)**

## FAKE data points to illustrate statistical power of d-Au data just taken

**FAKE data points to illustrate statistical power of d-Au data just taken**
**(there will be additional systematic uncertainties)**

## Summary

**Eskola**

**Kopeliovich**

**Shadowing for d+Au -> J/******

_**Summary**_

**J/******** suppression has a rich variation with kinematic variables, i.e x****F**** and p****T**
** ****gluon shadowing, absorption, parton energy-loss and p****T**** broadening all important**
** ****J/******** is complicated by feed-down from higher mass resonances**
** ****open-charm has no nuclear dependence at mid-rapidity (but this doesn’t shed any light on shadowing at small x)**
** ****Understanding J/******** suppression for normal nuclear matter is critical if the J/******** is to be used as a probe for hot high-density matter (QGP) in heavy-ion collisions**
** ****At RHIC the effect of shadowing is very uncertain with predictions that vary by large factors. So it is quite important to measure shadowing**

- open charm

## U.W. Theory Institute (INT), d-Au week, 2-6 June 2003

- 2 June – **Francois Arleo**, ECT, “*Energy loss of hard partons in cold and hot QCD media*”.
- 3 June – **David d-Enterria**, Columbia Univ, “*Hard scattering in Au+Au, D+Au and p+p collisions at sqrt(s_nn) = 200 GeV; Latest result from PHENIX at RHIC*”
- 4 June – **Peter Jacobs**, LBNL, “*Hard scattering in Au+Au, D+Au and p+p collisions at sqrt(s_nn) = 200 GeV; Latest result from STAR at RHIC*”
- 5 June – **Carlos Salgado**, CERN, “*Higt-pT particle production in nuclear collisions*”
- 5 June – **Rainer Fries**, Duke, “*Hadronization in Heavy Ion Collisions: Recombination and Fragmentation*”
- 6 June – **Mike Leitch**, LANL, “*Charm Production in E866/FNAL & PHENIX*”
- 6 June – **Ramona Vogt**, LBNL, “*J/Psi production at SPS and RHIC*”
- Participants: *Arleo, Aurenche, Bass Burward-Hoy, d-Enterria, Fries, Gagliardi, Gerland,  Jacak, Jacobs, Jalilian-Marian, Kunde, Leitch, Qiu, Randrup, Rischke, Salgado, Tuchin, Vitev, Vogt, Weidemann, Zhang, ...*

## Peter Jacobs

## Slide 22

## Slide 23

## Backup slides

## South PHENIX Muon Arm

- South Arm operating at optimal level after extensive repair work during the shutdown before the d+Au run
-  less than 1/3 of d+Au data in this analysis
-  trigger and other efficiencies still under study

- Number of J/’s expected from the *L *~ 2.7 nb-1
- d-Au run (w/o shadowing)
-  ~ 1000/arm for +-
-  ~ 400 for e+e-
- p-p run (just completed) may give ~ 300/arm J/’s

## North PHENIX Muon Arm

- _North PHENIX Muon Arm_

- 200 GeV d+Au

-  ~ 356 J/’s
- 3.11 ± .01 GeV
-  = 145 ± 11 MeV

- opposite-sign pairs
- same-sign pair bkgd

- Dimuon Mass (GeV/c)

- d+Au run is 1st for North Muon arm
-  mass resolution already close to optimal even without final alignment constants
-  this analysis from less than 1/3 of the d+Au data
-  efficiencies, especially for the trigger, still largely unknown for this quick analysis

- Comparison of North and South J/ yields not instructive at this stage since we are only beginning to study efficiency issues which could have large effects and the data samples are not identical

## 200A GeVAu-Au J/     ee

**NA50 - Phys. Lett B 521 (2002) 195**

**Binary scaling**

**4.4 mb absorption**
**7.1 mb absorption**

- 200A GeVAu-Au J/     ee

**We can not discriminate between scenarios, given our present statistical accuracy**

**PHENIX**

## Parton Energy Loss in Nuclei for Drell-Yan – Kopeliovich Model

***Johnson, Kopeliovich et al., hep-ph/0105195***

**Shadowing**

**dE/dx &**
**Shadowing**

***Drell-Yan data from E772 (PRL 64, 2479 (1990))***

**Shadowing when coherence length,**
** **
**is larger than nucleon separation**
** ****From E772 & E866 Drell-Yan data**
** ****With separation of shadowing**
**& dE/dz via Mass dependence**
** ****In the color-dipole model:**
**dE/dz ~ -2.7 ****±**** .4 ****±**** .5 GeV/fm**
**      **PRC _65_, 025203 (2002)

## Process Dependence of Shadowing?

-  Ordinary shadowing is process independent and is a “property” of the structure function in a nucleus

*Kopeliovich et al hep-ph/0104256*
*& hep-ph/0205151*

- In the color-dipole model suppression at large xF (small x2) is much stronger for the J/ than for open-charm
-  but here much of the “shadowing” is “higher-twist final-state c-cbar interactions”

- Jorg Raufeisen (private comm.)
-  Gluon shadowing in the color-dipole model for Au
-  here only the higher-twist _shadowing_ causes the difference between open and closed charm
-  (anti-shadowing from Eskola - ad hoc)
-  also see, PRD _67_, 054008 (2003)

- PHENIX will look for this in d-Au measurements by comparisons of rapidity dependence of suppression between open- and closed-charm.