The energy dependence of the single-transverse-spin asymmetry, A N, and the cross section for neutron production at very forward angles were measured in the PHENIX experiment at the Relativistic Heavy Ion Collider for polarized p+p collisions at √s=200 GeV. The neutrons were observed in forward detectors covering an angular range of up to 2.2 mrad. We report results for neutrons with a momentum fraction of xF=0.45 to 1.0. The energy dependence of the measured cross sections were consistent with xF scaling, compared to measurements by an experiment at the Intersecting Storage Ring, which measured neutron production in unpolarized p+p collisions at √s=30.6-62.7 GeV. The cross sections for large xF neutron production for p+p collisions, as well as those in e+p collisions measured at the Hadron-Electron Ring Accelerator, are described by a pion exchange mechanism. The observed forward neutron asymmetries were large, reaching AN=-0.08±0.02 for xF=0.8; the measured backward asymmetries, for negative xF, were consistent with zero. The observed asymmetry for forward neutron production is discussed within the pion exchange framework, with interference between the spin-flip amplitude due to the pion exchange and nonflip amplitudes from all Reggeon exchanges. Within the pion exchange description, the measured neutron asymmetry is sensitive to the contribution of other Reggeon exchanges even for small amplitudes.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 2013 Aug 8|
Bibliographical noteFunding Information:
Mortality of breast cancer is almost due to subsequent metastases, but the micrometastasis is difficult to be detected. Early diagnosis of distant metastasis is a key to improve prognosis of breast cancer. The nm23 gene is a putative metastasis suppressor gene originally identified in routine melanoma cells. The Received date: February 8, 2002; Accepted date: March 28, 2002. Foundation item: This work was supported by the National 9th Five-Year Program of China(No. 96-906-01 - 13). *Author to whom correspondence should be addressed. Phone: (0086-22)-23359901 ext. 352; Fax: (0086-22)-23359984; E-mail: kathy firstname.lastname@example.org Biography: Liu Hong(1968-), female, master of oncology, associate professor, Tianjin Medical University, majors in oncology.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)