Forward Collisions and Spin Effects in Evaluating Amplitudes N. Akchurin, Texas Tech University, USA N. Buttimore, Trinity College Dublin, Ireland A. Penzo, INFN and Università di Trieste, Italy SPIN 2010 September 30 Julich

Introduction Polarized proton collisions probe dependence on spin Analyticity relates low and high energy helicity amplitudes Hadronic spin effects are enhanced by photon exchange interference Study forward spin dependence for cross section normalisation SPIN Julich N Buttimore1

Peripheral Proton and Ion Collisions Hadronic spin dependence is important for Parton distribution functions and nucleon form factors Measuring the proton beam polarization at BNL RHIC, Makdisi, AIP Conf Proc 980 Spin dependent couplings of the Pomeron, Trueman, Phys Rev D77 SPIN JulichN Buttimore2

Analyzing Power in CNI Region Analyses assume pp double-flip amplitudes are zero Interference value t c = 8  /  tot, hadronic slope B Bethe phase  ≈ 0.02, real-to-imaginary  ≈ 0.02 Proton mass m and anomalous moment  = SPIN JulichN Buttimore3

Spin flip Ratio from Low –t A N for pp SPIN Julich4N Buttimore E704 (p=200 GeV/c)  RHIC (p=100 GeV/c) ☐ RHIC (√s= 200 GeV) |r 5 |= ±  5 = 94.1 ± 1.6

Phase & Magnitude for pp Spin flip SPIN Julich5N Buttimore 11 33 22

Overlay of Asymmetry Data at 6.8 GeV SPIN Julich6N Buttimore

Proton Carbon Small Angle Asymmetry Advantages of using spinless isosinglet ions in the case of elastic proton carbon scattering – Only isoscalar t-channel exchanges are permitted – Spin zero carbon limits types of gluon exchanges – Pomeron contribution differs from the proton case providing more insight into high energy dynamics Kopeliovich and Trueman, Phys Rev D 64 (2001) SPIN JulichN Buttimore7

pC Scattering at p=22 GeV/c SPIN JulichN Buttimore8 Asymmetry data J. Tojo et al, PRL 89 (2002) Spin Flip Magnitude and Phase

pC Scattering at p=22 GeV/c SPIN JulichN Buttimore9 Asymmetry data J. Tojo et al, PRL 89 (2002)

pC Scattering at p=22 GeV/c SPIN JulichN Buttimore10 Asymmetry data J. Tojo et al, PRL 89 (2002) 1 33 22

pC Scattering at p=100 GeV/c SPIN JulichN Buttimore11 Asymmetry data from O. Jinnouchi et al, SPIN2004 Spin Flip Magnitude and Phase

pC Scattering at p=100 GeV/c SPIN JulichN Buttimore12 Asymmetry data from O. Jinnouchi et al, SPIN2004

pC Scattering at p=100 GeV/c SPIN JulichN Buttimore13 Asymmetry data from O. Jinnouchi et al, SPIN2004 11 33 22

Conclusions Available small –t data for A N suggest that pp hadronic spin flip is small Magnitude |r 5 |= ± and phase  5 = 94.1 ± 1.7 degrees Only statistical experimental errors are considered in this analysis. Systematic errors need to be included The pp data at 6.8 GeV indicate more substantial hadronic spin flip Systematic errors in pC data also need study as the spin- flip phase is very different from the pp phase More accurate pC asymmetry data should result from a RHIC polarimeter upgrade SPIN JulichN Buttimore14