# Presentation: 593079

## J/Y & Heavy-Quark Production in E866 & PHENIX

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

***Fourth International Conference on***
***Perspectives in Hadronic Physics ***
***Abdus Salam International Center for Theoretical Physics, May 12-16, 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

## 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**_

## 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

## 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)

## 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 

_**Systematics of P**__**T**__** 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.

## J/Ψ and  Polarization

_**J/**__**Ψ**__** and **__****__** Polarization**_

***E866/NuSea***

**NRQCD based predictions (color octet model) necessary to explain CDF charm cross sections**
**E866 J/******** measurement not in agreement with NRQCD based predictions *****[Beneke & Rothstein, PRD ***_***54***_***, 2005 (1996)]***** which give**
**0.31 < ****λ < 0.63**
**J/******** complicated by feed-down (~40%) from higher mass states.**

**However ********(2S+3S), which should not suffer from feed-down, have maximal polarization consistent with the Octet model!**

**DY**

**Υ****2S+3S**

**Y****1S**

## 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**

## Radiographs of active area for South arm in run-II. (Three stations with 3 or 2 gaps each)

**Sta-1**

**Sta-2**

**Sta-3**

- Vast improvement for present (run-III) after extensive repairs to electronics and HV during shutdown

**Gap-1**

**Gap-2**

**Gap-3**

## 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-
- Similar numbers for p-p run possible

## 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

## Charm from High-pT ElectronsNon-photonic Single Electron Spectra

**PHENIX: PRL 88(2002)192303**

-  Single electron spectra, after
-   background (photonic source)
-   is subtracted, for central and
-   M.B collisions at s**NN**=130GeV
-  Electrons from charm and
-   beauty decays calculated by
-   PYTHIA
-   -- PYTHIA tuned
-      to fit low energy data
-   -- & scaled to Au+Au using
-      number of binary collisions.
-  Charm from PYTHIA in reasonable agreement with data
-  (within relatively large uncertainty)
-  The contribution from thermal dileptons and direct  is neglected
-   -- could mean we over-estimate the charm yield.

**Notes:**
After back ground electrons are subtracted, we can see the pT spectra of single 
electrons from non-photonic source. Light figure shows the spectra in central and 
minimum bias collisions at 130GeV of square root of s.

The electron from Charm and beauty decays are calculated by PYTHIA
And overlaid in the plot. In this calculation, PYTHIA parameter 
Is tuned so that the calculation is fit to low energy data.
Additionally, that calculated electron yield are scaled to gold on gold collisions
By using number of binary collision scaling.
You can see the charm in PYTHIA have good agreement with the data within
Large uncertainty. We should mention that the contribution from thermal
Di-leptons and direct photon is neglected in the cocktail calculation.
So, we may over-estimate the charm yield. 

## Charm Cross Section

-   compared with ISR data
-  Charm cross section is compared
-   with fixed target charm data.
-  Solid curve     : PYTHIA
-  shaded Band  : NLO pQCD
- Assuming binary scaling,
- PHENIX data are consistent with s systematics (within large uncertainties)

-  By fitting the PYTHIA electron spectrum to the data
-     for pt>0.8 GeV/c, get the total charm yield Ncc per event.

**PHENIX**

**PYTHIA**

**ISR**

**NLO pQCD ****(M. Mangano et al., **
**NPB405(1993)507)**

**PHENIX: PRL 88(2002)192303**

_**Charm Cross Section**_

**Notes:**
Charm production cross section are evaluate as following.
By fitting the PYTHIA electron spectrum to the data above 0.8GeV in pT.
We obtained the charm yield per events. Charm cross section
Per binary collision are obtained by this function. Here, Taa is 
A nuclear overlap integral which means integrated luminosity
Per event. Taa in minimum bias events and 0-10% central events
Are this number. Then, charm cross section are obtained as
380 micro barn in central 420 micro barn in minimum bias collisions
With large uncertainty.
That electron and charm cross sections are compared with
The low energy data and theoretical calculation.
Left figure shows the result of comparison. The red point shows
The PHENIX electron result and the blue point shows
The other measurement at low energy experiment. 
Top half indicates the charm cross section and the red point
Is the phenix measurement. Here, black line is the expectation
From PYTHIA calculation and gray band is QCD calculation. 
The PHENIX data are consistent with root s dependence 
Under binary collision scaling within large uncertainty. 

## Summary

_**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 at PHENIX**

## 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 30

## Backup slides

## 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**

## Slide 33

## 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.

## Cocktail Calculation

_**Cocktail Calculation**_

-  p**T** distribution of 0 are constrained
-   with PHENIX 0  and  measurement
-  p**T** slope of , ’  and  are
-   estimated with m**T** scaling
-   p**T** = sqrt(p**T****2 **+ Mhad**2**** – **M**2**)
-  Hadrons are relatively normalized by
-   0 at high p**T** from the other
-   measurement at SPS, FNAL, ISR, RHIC
-  Material in acceptance are studied for
-   photon conversion
- Signal above cocktail calculation can  be seen at high p**T**

**Notes:**
We calculated the cocktail of electron from the sources we considered.
In this calculation, pt spectra of pi0 are constrained with PHOENIX neutral 
and charged pion measurement. 
Spectral shape of the other hadrons are estimated by using mT scaling.
The yield of the other hadrons are relatively normalized by pi0 at
High pt. That normalization factor are taken from the other measurement
In proton induced collisions at those place.
Amount of material in our detector are studied to estimate the contribution 
From photon conversions.
Right figure shows the expected electron yield from several sources
and this black line is a total yield of all expected sources. 
You can see some difference between data and expected yield at
High pt.

## J/ Kinematic Coverage for present PHENIX d-Au (run-III)

- 	PHENIX has very broad coverage in xF, pT and x2 by combining
- North Arm
- Central Arm
- South Arm