Total and Differential Cross Sections, and Polarization Effects in pp Elastic Scattering at RHIC
Abstract
An experiment to measure proton-proton (pp) elastic scattering at the Relativistic Heavy Ion Collider (RHIC), the pp2pp experiment, is being constructed. The experiment will be able to measure pp elastic scattering with polarized and unpolarized beams in both collider and fixed-target modes of operation covering Center of Mass Energy range 7 < √s < 500 GeV. By measuring elastic scattering in the nonperturbative regime of QCD, with four momenta transfer 0.006 < t < 1.5 (GeV/c)^2, experiment will address one of the main, unsolved problems in particle and nuclear physics: long range QCD and confinement. Thus, the experiment will extensively map the diffractive regime of strong interactions over a wide range of s and |t|. Additional polarization observables will give access to spin degrees of freedom, which distinguish between different nucleon structure models, like the quark diquark model of the proton. By measuring spin asymmetries like A_N, A_NN, A_LL at moderate values of |t|, we will be able to determine the helicity amplitudes φ_i, which describe elastic scattering. Those amplitudes are not well known at this time. A systematic study of this at RHIC will lead to understanding of the spin structure of the nucleon and of the exchanged mediator of the force, the Pomeron and Odderon. For the first run, position sensitive Si detectors inside Roman Pots will measure small angle scattering in the collider mode. Future experiments will utilize a polarized jet target and recoil detectors to provide precise measurements of average asymmetry in the Coulomb Nuclear Interference (CNI) region. The current status of preparations for the first experiments will be presented and the future program will be discussed.
- Publication:
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APS Division of Nuclear Physics Meeting Abstracts
- Pub Date:
- October 2000
- Bibcode:
- 2000APS..DNP.JG005G