# Presentation: 582372

## Charm Production in E866/FNAL & PHENIX

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

***Seattle Theory Institute, June 2-6, 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**_

## Scaling of J/ Suppression?

-  Shadowing and initial-state gluon energy loss thought to be main reasons for increasing suppression at larger xF
-  But this effect does not scale with x2 as expected for shadowing between E866 at 800 GeV & NA3 at 200 GeV
-  Although does scale with xF which would be expected for energy loss
-  Remains a puzzle...

- E866 - PRL 84, 3256 (2000)
- & NA3 - PRL_84_(2000),3258

## 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

## 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 

## E866 - J/Nuclear dependence even for Deuterium/Hydrogen

**From fits to E866/NuSea**
**p + Be, Fe, W data:**

- Nuclear dependence in deuterium seems to follow the systematics of larger nuclei, but with an effective A smaller than two.

## 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?**_

## PHENIX Muon Arms

- Acceptance : 1.2 < |**| < 2.4        *       *
- 
- Muon minimum momentum ~ 2 GeV/c

_**PHENIX Muon Arms**_

## First J/  +-’s at RHIC

_**First J/**__****__** **__****__** **__****__**+**__****__**-’s**__** at RHIC**_
-  36 counts from South muon arm in 2001-2002 run as shown at Quark Matter last July (now 66 with tuned pattern recognition and analysis)
-  Quark Matter cross section consistent with lower energy measurements extrapolated to RHIC energy by various theoretical models

**QM02**
- 36 counts

**QM02**

## Electron Measurement in PHENIX

- High resolution tracking and momentum measurement from  Drift chamber.
- Good electron identification from Ring Imaging Cherenkov detector (RICH) and Electromagnetic Calorimeter (EMCal).
- High performance Level-1/Level-2 trigger

- Measure electron between ||<=0.35 and mom>=0.2GeV

## J/ee in pp @ 200 GeV

- J/ee in pp @ 200 GeV

**|y| <0.35      ****N****J/******** = 24 **_**+**_** 6 **_**+**_** 4 (sys)****     **
**Bd********/dy = 61.8 **_**+**_**9.8 (stat) **_**+**_** 9.4 (sys) **_**+**_** 6.4 (abs) nb**

## ppJ/ at RHIC

**PHENIX data agrees with the color evaporation model prediction at ********s=200 GeV**

- _pp____J/____ at RHIC_

****** ****(p+p********J/********X)**
**3.98 ******** 0.62 (stat.) ******** 0.56 (sys) ******** 0.41 (abs) μb**

## South Muon Arm

- North Muon Arm

**Both PHENIX Muon Arms Operational in Present d-Au Run**

## 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

## J/->e+e- Signal in d-Au Collision

- With online calibration, we observed J/->e+e- signal.
- The width of J/ is expected to be 60 MeV after good calibration.
- We expect to get a few hundred J/->e+e- from the 2003 d-Au run.

- Observed signal online
- Crude calibration

## 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)**

## 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)**

**(also impact parameter dependence)**

## Slide 25

## 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

## Summary-continued

**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

## Slide 28

## Backup slides

## E866 - Correction to Nuclear Dependence for pT Acceptance

-  Acceptance in pT is considerably narrowed at low xF
-  Use MC acceptance & dσ/dpT consistent with our data to correct for incomplete coverage
-  **This also is why E772 (which had stronger narrowing of p****T**** at small x****F****) J/********’s got ******** ~ 0.92**

_**E866 - Correction to Nuclear Dependence for p**__**T**__** Acceptance**_

## 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.

## 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**