# Presentation: 803919

## Physics with Tagged Forward Protons at RHIC Włodek GurynBrookhaven National Laboratory, Upton, NY, USA

- Introduction - (qualitative) description of the processes;
- What can be done at RHIC?
- Implementation;
- Summary.

## Physics Processes I

## Physics Processes II

- These processes are mediated by gloun rich exchanges

## Elastic and Inelastic Processes

- In terms of QCD, Pomeron exchange consists of the exchange of a color singlet
- combination of gluons. Hence, triggering on forward protons at high (RHIC) energies predominantly selects exchanges mediated by gluonic matter.

- For each proton vertex one has
**t **    four-momentum transfer
******p/p **
**M****X** invariant mass

## p(d)A Scattering

- Study dependence on A and beam polarization of inclusive diffraction in p(d)A pA.
- Due to spectator effects in deuteron Nucleus collisions dApX the pT spectrum of the outgoing proton shows a clear diffractive pattern because of the absorption of the center of incoming wave [B.K.].
- One can also study the size of the rapidity gap in the same reaction, where the size of the "rapidity gap" reflects the different contributions of various Fock configurations of the proton that scatters through the color field of the nucleus [R.V.].

## Central Production in DPE

- In the double Pomeron exchange process each proton “emits” a Pomeron and the two Pomerons interact producing a massive system MX.
- The massive system could form resonances or consist of jet pairs. Because of the constraints provided by the double Pomeron interaction, glueballs, and other states coupling preferentially to gluons, will be produced with much reduced backgrounds compared to standard hadronic production processes.

## Glueball Central Production in DPE

- The idea that the production of glueballs is enhanced in the central region in the process pp  pMXp was first proposed by F.Close and was demonstrated by WA102 expt.
- The pattern of resonances produced in central region depends on:
- dPT  kT1 kT2
- When dPT  QCD qq states are prominent and when dPT is small the surviving resonances include glueball candidates.

## Implementation at RHIC

- Need detectors to tag forward protons and detector with good acceptance and
- particle ID to measure central system

## Physics with Tagged Forward Protons with the STAR Detector at RHIC

- H. Spinka
*Argonne National Laboratory, USA*
- R.E. Chrien, R. Gill, W. Guryn*, B. Hackenburg, J. Landgraf, T.A. Ljubičič, D. Lynn,
- C. Pearson, P. Pile, S. Tepikian, K. Yip
*Brookhaven National Laboratory, USA*
- A. A. Bogdanov, S.B. Nurushev, M.F Runtzo
*Moscow Engineering Physics Institute (MEPHI), Moscow, Russia*
- I. G. Alekseev, V. P. Kanavets, L. I. Koroleva, B. V.  Morozov, D. N. Svirida
*ITEP, Moscow, Russia*
- B. Surrow
*MIT, Boston USA*
- S. Khodinov, M. Rijssenbeek
*SUNY Stony Brook, USA*
- A.Sandacz
*Soltan Institue for Nuclear Studies, Warsaw, Poland*
- *Contact person
- E-mail _[guryn@bnl](mailto:guryn@bnl.gov)__[.](mailto:guryn@bnl.gov)__[gov](mailto:guryn@bnl.gov)_
- Phone (631) 344 3878

## Acceptance Studies SDD

- Single proton in the Roman Pot

## Acceptance Study DPE

- Two protons are detected

## Reconstruction of the Momentum Loss 

****** **Accelerator transport

- Need to measure vector at the detection point, hence two RPs are needed on each side of STAR.
- For a proton, which scatters with  and  we have:

## Running Scenario for Phase I

- Important conditions:
- One event in the TPC per proton pair in RPs  “low luminosity”;
- Alignment is very important  use elastic events;
- Need to reach small t and  values  large *=20m.
- Hence a dedicated three-day run is preferable

- The setup time of the *=20 m optics is estimated to be 12 hours.
- With 40 hrs data taking, luminosity 2×1029 cm-2sec-1   2105 DPE events.

## Summary

- The physics program of tagged forward protons with STAR at RHIC can:
- Study standard hadron diffraction both elastic and inelastic and its spin dependence in unexplored t and s range;
- Study the structure of color singlet exchange in the non-perturbative regime of QCD.
- Search for central production of light and massive systems in double Pomeron exchange process -  glueballs.
- Search for an Odderon - an eigenstate of CGC.
- At RHIC II one would take advantage of smaller TPC, include more coverage to better characterize rapidity gaps.
- Those studies will add to our understanding of QCD in the non-perturbative regime where calculations are not easy and one has to be guided by measurements.
- There is a great potential for important discoveries

## Proton Trajectory