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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.

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forward collisions and spin effects in evaluating amplitudes

Forward Collisionsand Spin Effects in Evaluating Amplitudes

N. Akchurin, Texas Tech University, USA

N. Buttimore, Trinity College Dublin, Ireland

A. Penzo, INFN and Universitàdi Trieste, Italy

SPIN 2010 September 30 Julich

introduction
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

N Buttimore

peripheral proton and ion collisions
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

N Buttimore

analyzing power in cni region
Analyzing Power in CNI Region

Analyses assume pp double-flip amplitudesare zero

Interference value tc= 8pa /stot , hadronic slope B

Bethe phase d ≈ 0.02, real-to-imaginary r≈ 0.02

Proton mass mand anomalous momentk= 1.7928

N Buttimore

spin flip ratio from low t a n for pp
Spin flip Ratio from Low –t AN for pp

|r5|= 0.059 ± 0.008

q5= 94.1 ± 1.6

 E704 (p=200 GeV/c)

RHIC (p=100 GeV/c)

☐ RHIC (√s= 200 GeV)

N Buttimore

proton carbon small angle asymmetry
Proton Carbon Small Angle Asymmetry

Advantages of using spinlessisosinglet ionsin the case of elastic proton carbon scattering

  • Only isoscalart-channel exchanges are permitted
  • Spin zero carbon limits types of gluon exchanges
  • Pomeron contribution differs from the proton caseproviding more insight into high energy dynamics

Kopeliovichand Trueman, Phys Rev D 64 (2001)

N Buttimore

pc scattering at p 22 gev c
pC Scattering at p=22 GeV/c

Asymmetry data J. Tojo et al, PRL 89 (2002) 052302

Spin Flip Magnitude and Phase

N Buttimore

pc scattering at p 22 gev c1
pC Scattering at p=22 GeV/c

Asymmetry data J. Tojo et al, PRL 89 (2002) 052302

N Buttimore

pc scattering at p 22 gev c2
pC Scattering at p=22 GeV/c

2s

1s

3s

Asymmetry data J. Tojo et al, PRL 89 (2002) 052302

N Buttimore

pc scattering at p 100 gev c
pC Scattering atp=100 GeV/c

Asymmetry data from O. Jinnouchi et al, SPIN2004

Spin Flip Magnitude and Phase

N Buttimore

pc scattering at p 100 gev c1
pC Scattering atp=100 GeV/c

Asymmetry data from O. Jinnouchi et al, SPIN2004

N Buttimore

pc scattering at p 100 gev c2
pC Scattering atp=100 GeV/c

2s

1s

3s

Asymmetry data from O. Jinnouchi et al, SPIN2004

N Buttimore

conclusions
Conclusions
  • Available small –t data for ANsuggest that pphadronic spin flip is small
  • Magnitude |r5|= 0.059 ± 0.008 and phase q5= 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

N Buttimore