Probing the Gluon Sivers Function through direct photon production at RHIC
| Autor: | Anuradha Misra, Rohini M. Godbole, Abhiram Kaushik, Siddhesh Padval |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Physics
Quark Particle physics Photon 010308 nuclear & particles physics media_common.quotation_subject FOS: Physical sciences Parton Invariant (physics) 01 natural sciences Asymmetry Universality (dynamical systems) Gluon High Energy Physics - Phenomenology High Energy Physics - Phenomenology (hep-ph) 0103 physical sciences Centre for High Energy Physics High Energy Physics::Experiment 010306 general physics Nuclear Experiment media_common |
| Zdroj: | Physical Review |
| Popis: | We study the production of prompt-photons at RHIC in the context of a generalised parton model framework, with a view to obtain information on the gluon Sivers function (GSF). At RHIC energy ($\sqrt{s}=200$ GeV), the Compton process, $gq\to\gamma q$ contributes significantly to the production of direct-photons at midrapidity and dominates it in the negative (backward) rapdity region. We find that for direct photons, asymmetries of upto 10\% are allowed by a maximal gluon Sivers function. However, the asymmetry obtained using existing fits of the GSF available is literature is negligible. We also estimate the impact that photons produced via fragmentation can have on the signal and find that their inclusion can dilute the asymmetry by between 10-50\% of the direct-photon value. Finally, using the Colour-Gauge Invariant generalised parton model (CGI-GPM) approach, we consider the effects of initial state and final state interactions which can affect the universality of the Sivers functions in different processes. We find that the inclusion of these effects leads to the size of the gluon contributions being roughly halved. However, in the backward region which we are interested in, the sizes of the quark contributions are suppressed even further, leading to increased dominance of the gluon contributions. Comment: 32 pages, 7 figures, v3: Version published in Phys. Rev. D. Discussion of BSR based results updated. References added |
| Databáze: | OpenAIRE |
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