Overview BackgroundPhysics and experimental issues.- Further explore low-x physics (Gluon Saturation)
- Polarized spin asymmetries at large xF
- Fixed Target opportunities
Implications for RHIC planning
Background Forward physics is at present being explored at RHIC by BRAHMS (charged identified hadrons) STAR (0 ), PHENIX (muons), PHOBOS (charged particles) and via ZDC, PCAL measurements.Physics opportunities exist for additional measurements at RHIC that are not covered in the present program, and should lead to new measurements with existing or modified detectors.As of now a subset people from Brahms and Phobos have been discussing ideas; a broader group would be helpful to carry this to a proposal and de facto experiment stage.
Such ideas were discussed at a one-day workshop in October, and in the BNL Physics Departments Planning Groups White-Paper. Such ideas were discussed at a one-day workshop in October, and in the BNL Physics Departments Planning Groups White-Paper.The ideas brought forward cover a broad range of physics interests. It is not clear the execution of these can be covered within a single experi-mental setup. Some of these ideas have connections to the future program with eRHIC; In part via exploration at large y, small x and through possible ‘common’ detector elements.
Heavy Ions Heavy Ions- Low-x physics
- Gluon saturation is best explored at forward rapidities or high energies corresponding to small x. The CGC approach is an intriguing description of initial state strong interactions and offers a connection between RHIC, HERA and eRHIC.
- Extended measurements at forward rapidities will offer an additional experimental test of this. Particularly important will be p(d)-A, and A-d(p) measurements
What is needed to extend these measurements significantly Extend pt reach to ~6 GeV/c for inclusive spectra.Kinematic limit restrict such measurements to ~2-3.5Momenta and PID determination in range of 20-60 GeV/c
Yields and rates needed.
Straw man Detector
Benefits Such a new/modified detector will bring the d-A measurements into a pt region where one might expect partonic hard scattering, and can quantify observed differences.Observing these high-pt particles with the opposite side particle production might illuminate the question of di-jet vs. gluon fusion processes.Making such quantitative measurements of the d-A and pp with detailed comparisons to theoretical descriptions is relevant to the future e-A program at eRHIC.
Forward Spin Physics- Needed measurements in Transverse polarization (AN)
- 0 AN have been measured by STAR
- Additional measurements are possible with Brahms but the range in xF is limited due to solid angles.
Polarized pp AN measurements
Other connections Other opportunities are present in diffractive physics and Ultra peripheral collisions. These are options that could be implemented within an area with an open geometry like IP2.- Large uncertainties in knowledge on atmospheric interactions, in particular inelasticity parameter. Regions of particular interest are large xF (0.4-0.9) and lighter ion beams (Fe, N, p)
- Part of this community may be attracted to a forward physics program.
Incorporating this into RHIC decadal planning The proposed d-A program will require other such run(s) within the frame of the decadal plan (and a new/modified detector, size to be determined).The spin program would fall into a time-scale where polarization and intensities have been developed so a (relative) short program can make the AN measurements for +- to larger XFA fixed target program is envisioned using an existing detector system on a shorter time-scale.
Conclusions This initiative is clearly a work in progress, and has several options with details still have to be worked out. There are though several important physics issues that ought to be addressed by the RHIC physics program.The region of forward physics do have a clear connection, experimental, instrumental as well as physics interest to the envisioned program at eRHIC.
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