# Presentation: 820422

## J/ from PHENIX

- J/ production and use as a probe
- Review of current analyses that are nearing completing
- J/ from AuAu
- Outlook

- 7 Feb 2005

## Models of Charm and J/ Production

- Many input parameters to both pQCD portion and hadronization portion of models

- Total cross sections and Differential vs. y, pT, √s, etc. necessary to simultaneously constrain theoretical uncertainties

- _Factorize calculations:_
- pQCD to calculate cc production
-       propagation and Hadronization
- Production sensitive to gluon distribution function
- In polarized pp, sensitive to gluon polarization
- Common pQCD for open charm, J/ used to distinguish between initial and final-state effects

**Models of Charm and J/******** Production**

- 7 Feb 2005

## Nuclear Effects on Charm, J/ Production in dA

**Initial state/final state interactions with medium**
- Multiple scatteringbroadening of pT spectra
- Energy loss
- Absorption reduces J/ as      , J/ propagate through nucleus

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

- EKS98 Shadowing

**Modification of the parton distribution functions:**
- Gluon shadowing would lead to reduction of production at low x.  Antishadowing would give enhancement at moderate x

- 7 Feb 2005

## Charm and J/ in Heavy Ion Collision

- _pA effects scaled up PLUS_
- Hot hadron gas, comovers
- QGP/dense matter modifications to production:
- Debye screening,
- Enhancement in coalescence models, balancing of D+D↔J/+X
- Thermal production of charm
- Energy loss and dead cone effect

- 7 Feb 2005

## J/ Suppression in Pb-Pb at NA50

- Suppression with respect to normal nuclear suppression expectations
- Theorists have produced various alternative models which also reproduce data:
- Statistical coalescence model (also needs enhanced open charm)
- Comovers
**RHIC data on J/******** highly desired to compare**

- 7 Feb 2005

## J/ from AuAu Collisions at 200 GeV, Run 2

- Not enough statistical significance to distinguish various models but strong enhancement seems to be disfavored.

**J/******** from AuAu Collisions at 200 GeV, Run 2**

- 7 Feb 2005

## J/ Measurements from PHENIX

- pp at 200 GeV (Runs 2, 3 and 4 at RHIC)
- Baseline for understanding modifications in dAu, AuAu
- J/ polarization (may help in understanding production)
- Gluon contribution to spin
- dAu at 200 GeV (Run 3)
- Nuclear modifications to procution in cold-nuclear matter.
- AuAu at 200 GeV (Run 2 and 4)
- How does hot dense matter formed modify production, what does this imply about matter formed?

- 7 Feb 2005

## LANL Contributions to J/efforts

- In addition to hardware, detector commisioning, etc.:
- Run 2 pp
- All MuTr analysis software from LANL
- First J/ measurement from RHIC
- Small group producing cross section output; LANL 1 of 6 on paper-writing committee
- Run 3 dAu
- LANL continued to be major contributor to analysis software
- LANL headed up analysis and paper-writing of results
- Run 4 AuAu
- Much larger analysis team now, but LANL still playing one of lead roles in tool development and analysis
- Work in progress
- Run 5 CuCu and pp
- Plan to work on spin and polarization pp measurement.  Most likely some work contributing to CuCu

- 7 Feb 2005

## J/ from pp Collisions at 200 GeV (Runs 2+3)

- Central and forward rapidity measurements:
- Rapidity shape consistent with various PDFs
- √s dependence consistent with various PDFs with factorization and renormalization scales chosen to match data
- Higher statistics needed to constrain PDFs

- 7 Feb 2005

## PHENIX:  J/ in dA

**PHENIX:  J/******** in dA**

- PHENIX measurements cover expected shadowing, anti-shadowing range
- All expected to see pT broadening
- dE/dx not expected to be significant effect at RHIC energies
- Overall absorption expected

- 7 Feb 2005

## J/ from dAu Collisions at 200 GeV

- Suppression in deuteron direction consistent with some shadowing but can’t distinguish among various models, Overall absorption

- d

- Au

- 7 Feb 2005

## J/ from AuAu Collisions at 200 GeV

- Technical Challenges
- Very high occupancy environment
- Large data set to analyze in timely manner
- Physics Challenges
- Theoretical Expectations cover Large Range
- Interpretation may be challenging
- Expectations
- Few thousand J/s from each arm
- Yield versus centrality, rapidity pT
- Flow measurement

- 7 Feb 2005

## Technical Challenges - High Occupancy

- 7 Feb 2005

## Difficult to Find Everything with High Efficiency

- North

- South

**Difficult to Find Everything with High Efficiency**

- Much work over past months to improve performance (mostly LANL) with noticeable headway, but may require additional work
- Plan to proceed with a pass on data and preliminary result

- 7 Feb 2005

## Current State of Signal:Background, 40-92%, 20-40%

- South

- 7 Feb 2005

## Future J/

- Run 5 and Run 6 pp
- Significant J/ polarization measurement
- Possibility for gluon polarization, certainly techniques and tools will be established
- Improved signal:background in AuAu events with forward silicon
- Combine with other vector meson measurements (’, , chi? )

- 7 Feb 2005

## Backups

- 7 Feb 2005

## Gluon Polarization (feasible in Run 5/6)

- A_LL from J/Psi

- 7 Feb 2005