# Presentation: 138331

## Discussion

- Global Analysis of Polarized RHIC and DIS data:
*How do we get there?*

- Global Analysis Workshop at BNL, Oct. 8, 2007

## Disclaimer:No decisionsOnly thoughts and proposals.For every one to get involved and participateAim today is to plan: how we start off and get there...

- Discussion

- 10/08/2007

## Observations

- Need for a global analysis using the most advanced experimental data and theoretical techniques is beyond argument
- There is ample experience in un-polarized DIS and p-p/p-pbar data set:
- Ample guidance
- Open questions
- Food for thought

- Discussion

- 10/08/2007

## A Minimum Aim

- To include polarized DIS data and the new RHIC data (present and future) to determine the best possible *polarized gluon* distribution and its first moment
- In future when W physics comes of age we should be able to include them consistently in the analysis to extract the flavor *separated quarks and anti-quarks distributions*
- Adding new DIS data is straight forward at this stage, but
- issues of handling HT corrections, target mass corrections, radiative corrections may need to be thought through...(?)

- Discussion

- 10/08/2007

## Technical Issues

- Getting a consistent fitting code at NLO that reliably determines the pdfs
*Mainly a theoretical effort at the moment to be led by the theorists amongst us*
- Do a systematic uncertainty analysis including statistical and systematic uncertainties and their correlations
*Mainly a project in which experimentalists will contribute principally*

- Discussion

- 10/08/2007

## A semi-proposal:

- Theorists who did this full time, did not get future jobs, despite their significant contribution
- Can not expect a full time theorist to do this
- How about an experimentalist + backing from theorists and experimentalists on various technical issues
- Supported as well by experimental collaborations (STAR, PHENIX, DIS-exp.s)
- Contribution is not only welcome, but *essential*
*We propose to start something like the “RHIC Spin Collaboration”*
- This is the assumption we are starting off with

- Discussion

- 10/08/2007

## Technical Theoretical Issues

- Theorists and basic structures to start this work already exists at NLO
- Players: *theorists around the table today*
- Analysis:
*NLO analysis for DIS + SIDIS exists in some form (Usable?)*
*Basic technical ideas and demonstrations on how to include RHIC (pp) data also exist*
- Our theory friends will of course lead this effort, keeping us all involved and informed in the discussions
- Need of CPUs/Computing power

- Discussion

- 10/08/2007

## Experimental Issues

- Beyond the fitting method, jump in to help with:
- At the beginning “Computing”
- Help with CPU for grid calculations
- Lead effort for multi-user user possibility
- Help with automation
- Handling of *uncertainties* in a technically consistent way
- Study and understanding of theoretical and experimental uncertainty correlations with consultation with experimentalists and theorists
- Uncertainty analysis with large computing farms

- Discussion

- 10/08/2007

## Correlated with these are issues of actually working on these issues:

- A core group starts off with the basic NLO fit development
- a “coordinator-group” for analysis
- A computing coordinator at an appropriate time:
- Initial grid computation issues: plan this according to what is expected from the data in future from RHIC (Inclusive pi0s, jets, then direct photon, gamma-Jet, Jet-Jet... then W physics)
- Always overseen by our theory friends:
- A new data set coordinator like the one in CTEQ “project coordinator” to include each of the pi0, jets...DIS data....
- Optimally chosen from EXPERIMENTAL collaborations

- Discussion

- 10/08/2007

## Mode of operation I

- Lets start with assumption: group will be here or around here or meet here
- Theorists local or/and visit as necessary
- PHENIX and STAR experimentalists visit often
- Short or long term stays of experimentalists envisioned and we should try to support
- Facilities for small informal meetings easily available (BNL and some times change of venue at SBU)
- Multiple, frequent visits by theorists to be supported by local support (BNL, RBRC, DOE, NSF, *any* other...)
- Post doctoral fellows, students lead the actual work with supervision from groups around them here.
- Experimentalists will necessarily do experimental work with collaborations.

- Discussion

- 10/08/2007

## Mode of operation II

- Monthly, bi-monthly, weekly meetings as seen appropriate
- Couple with big RHIC spin meeting(?) or separately as twice “collaboration” meeting a year
- Use phone, video, skype, personal visits across the groups contributing and institutions
- Communicate on regular basis on email (setup a email list for open discussion at BNL?)
- Suggestion: _[spinpdfs-l-lists@bnl.gov](mailto:spinpdfs-l-lists@bnl.gov)_ or something like this....

- Discussion

- 10/08/2007

## Results & publish them?(my personal opinion)

- Theoretically all new results or methods if appropriate should be published by the theorists as *they* please
- Uncertainty analyses comes from experimental issues, and their proper handling: will have to be decided up on within the “Global Fit Collaboration”
*Possibility of a GFC-fit result in long time future to explain all methods, archive the physics and methods*
*This may include all of us who have contributed in some way to this effort*
- Experimental collaborations(PHENIX, STAR, COMPASS...) may chose to use and publish subset of these data for their publication... its their discretion...
- We would try to keep the analysis in focus to get the best PDFs

- Discussion

- 10/08/2007

## Summary

- We need to do *this*, no matter what
- All are welcome to join and contribute
- We expect we need a lot of help at *various stages*, perhaps not start right away: ...This is not to exclude some one but only to organize this work
- Work could start with 1 post doctoral fellow supported by all of us. ( We have a candidate with unique background , expect students to jump in and help with technical details very soon )
- Last but not the least: When should we have the next meeting?

- Discussion

- 10/08/2007