Transverse Double Spin Asymmetries in the CNI region at sqrt(s) = 200 GeV

PAs: I. Alekseev, D. Svirida, ITEP, Moscow, ...

     At high energies and very small four momentum transfer squared (t) proton-proton elastic scattering is described by the interference of the Coulomb and nuclear amplitudes (CNI region). The latter is believed to be totally dominated by the classical pomeron exchange. In this case no double spin flip amplitude is present in the nuclear term and only very small double spin asymmetries can be expected due to the electromagnetic component. The manifestation of non-negligible transverse double spin effects would point to possible contributions from other Reggeons, such as the hypothetical Odderon, to the scattering amplitude.

     We report the first high presision results on the double spin asymmetries A_NN and A_SS in the collider energies. The data sample has ~20 million of elastic events in the -t range 0.003 < -t < 0.035 (GeV/c)². Small but non-zero double spin asymmetry  (A_NN+A_SS)/2 = -0.0051±0.0006(stat)±0.0012(syst) observed. We know of no theoretical prediction directly compatible.

Paper proposal presentation: drupal.star.bnl.gov/STAR/system/files/ANN_ASS_paper.pdf

Analysis notes:
Data analysis: drupal.star.bnl.gov/STAR/system/files/pp2ppANN_note.pdf
Luminosity analysis: drupal.star.bnl.gov/STAR/system/files/scalers_note_0.pdf

Analysis presentation: drupal.star.bnl.gov/STAR/system/files/ann_ass_presentation.pdf

Figures:
Raw double spin asymmetry for total t-range and the five t-intervals: drupal.star.bnl.gov/STAR/system/files/mainfit.pdf
(A_NN+A_SS)/2 and (A_NN-A_SS)/2 as function of -t. Vertical error bars include statistical error and systematic error coming from background subtraction: https://drupal.star.bnl.gov/STAR/system/files/uncorr_fit.pdf
Fitted values of r2 and r4 with ellipses corresponding to contribution of different error sources and total error: https://drupal.star.bnl.gov/STAR/system/files/r2r4.pdf