sPHENIX cold QCD topical group

["Lajoie, John G [PHYSA]" <lajoie AT iastate.edu>]

Dear Cold-QCD'ers:

Sasha, Ralf and I had a very productive discussion at the collaboration meeting about ways to jump-start possible forward instrumentation for sPHENIX.  In fact, the discussions resulted in a concrete set of action items we plan to pursue, so I thought it might be best to share this with the full cold QCD list so people are aware of what we are thinking and have an opportunity to participate.

First, some background -

As many of you are aware, spurred on by the work on the sPHENIX forward instrumentation paper from last year, Joe Osborn and I have been working with Hannu Paukunnen and his EPPS16 collaborators to estimate how well a comprehensive set of measurements in p+A at RHIC could constrain nuclear PDF's. At the present time they are working to include prompt photon pseudodata, and this again brought of the issue of forward prompt photons with (f)sPHENIX. At about the same time I visited Uniplast in Russia with Edward Kistenev, who suggested a passable EMCal could be made by cutting down the existing E864 Pb/Scifi calorimeter (10x10cm^2) towers to ~16cm in length and segmenting them with smaller light guides - 2cmx2cm would be close to the Moliere radius. (For those not familiar with the E864 calorimeter I am attaching a copy of the NIM article.)  We would only need to round up about 330 (of 768 total) E864 modules at BNL to cut them down and cover a pseudorapidity from 1.4-4 in the forward direction; we would still need mechanicals and electronics (copy of EMCal?).

This would give us an EMCal with sub-par EM resolution, BUT with sufficient granularity at ~4m to separate pizeroes from prompt photons. Sasha Basilevsky had a look using a fast MC and it looks like this idea is worth further study; it seems feasible for the lower rapidities, it gets dicey at the higher rapidities and needs simulation.  The physics justification would of course be nPDF's and CNM, but this would also enable a study of longitudinal dynamics in HI's (needs simulation).  While this would not be the full hadron arm we have all envisioned, it would get our foot in the door with something concrete.

So here's what we are thinking of doing over the next six months:

1. JL is planning to get this new version of the forward EMCal into G4 simulations this week.  This will enable the detailed performance studies that are the next step beyond Sasha's fast study.

2.  Sasha and I are in pursuit of an E864 module we can cut down, instrument and take to the FNAL test beam this spring. This should be doable, although we might have to raise some $ for light guides we can borrow EMCal electronics. This would establish the performance of the device in the real world.

3. We should push a little more on the EPPS16 pseudodata analysis. We have discussed publishing the results of the exercise and we should do that.  I think a publication like this would help underpin the CNM physics case nicely; it would be nice if this was on the arXiv this spring.

4. Enlist our HI colleagues to look as HI simulations and see if there are some key simulation performance plots that can be made. The experience in this is mostly in STAR and LHC folks, so we should look there and try to enlist some aid.

5.  If 1-4 come together nicely, perhaps a  presentation to the PAC in June would be in order? We could discuss this with the spokespersons.

Thoughts and discussion (and volunteers!) are welcome.

Regards,
John

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

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