1. 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

2. 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 2010-09-30 Julich N Buttimore1

3. 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 2010-09-30 JulichN Buttimore2

4. 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  = 1.7928 SPIN 2010-09-30 JulichN Buttimore3

5. Spin flip Ratio from Low –t A N for pp SPIN 2010-09-30 Julich4N Buttimore E704 (p=200 GeV/c)  RHIC (p=100 GeV/c) ☐ RHIC (√s= 200 GeV) |r 5 |= 0.059 ± 0.008  5 = 94.1 ± 1.6

6. Phase & Magnitude for pp Spin flip SPIN 2010-09-30 Julich5N Buttimore 11 33 22

7. Overlay of Asymmetry Data at 6.8 GeV SPIN 2010-09-30 Julich6N Buttimore

8. 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 2010-09-30 JulichN Buttimore7

9. pC Scattering at p=22 GeV/c SPIN 2010-09-30 JulichN Buttimore8 Asymmetry data J. Tojo et al, PRL 89 (2002) 052302 Spin Flip Magnitude and Phase

10. pC Scattering at p=22 GeV/c SPIN 2010-09-30 JulichN Buttimore9 Asymmetry data J. Tojo et al, PRL 89 (2002) 052302

11. pC Scattering at p=22 GeV/c SPIN 2010-09-30 JulichN Buttimore10 Asymmetry data J. Tojo et al, PRL 89 (2002) 052302 11 33 22

12. pC Scattering at p=100 GeV/c SPIN 2010-09-30 JulichN Buttimore11 Asymmetry data from O. Jinnouchi et al, SPIN2004 Spin Flip Magnitude and Phase

13. pC Scattering at p=100 GeV/c SPIN 2010-09-30 JulichN Buttimore12 Asymmetry data from O. Jinnouchi et al, SPIN2004

14. pC Scattering at p=100 GeV/c SPIN 2010-09-30 JulichN Buttimore13 Asymmetry data from O. Jinnouchi et al, SPIN2004 11 33 22

15. Conclusions Available small –t data for A N suggest that pp hadronic spin flip is small Magnitude |r 5 |= 0.059 ± 0.008 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 2010-09-30 JulichN Buttimore14