Prompt photon measurements with PHENIX's MPC-EX detector

29th Winter Workshop on Nuclear Dynamics

Campbell, Sarah^1

Building 510C, Brookhaven National Laboratoy, PHENIX, Upton, NY 11973, United States^1

关键词: Forward rapidity;    Heavy ion collision;    Jet measurements;    Nuclear parton distribution functions;    Prompt photons;    Reconstruction energy;    Single-spin asymmetries;    Transverse momenta;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/458/1/012028/pdf
DOI  :  10.1088/1742-6596/458/1/012028

来源: IOP

【 摘 要 】

The MPC-EX detector is a Si-W preshower extension to the existing Muon Piston Calorimeter (MPC). The MPC-EX consists of eight layers of alternating W absorber and Si mini-pad sensors. Located at forward rapidity, 3.180 GeV, a factor of four improvement over current capabilities. Not only will the MPC-EX strengthen PHENIX's existing forward π0and jet measurements, it will provide sufficient prompt photon and π0separation to make a prompt photon measurement possible. Prompt photon yields at high pT, pT> 3 GeV/c, can be statistically extracted using the double ratio method. In transversely polarized p+p collisions, the measurement of the prompt photon single spin asymmetry, An, will resolve the sign discrepancy between the Sivers and twist-3 extractions of An. In p+Au collisions, the prompt photon RpAuwill quantify the level of gluon saturation in the Au nucleus at low-x, x ∼ 10-3, with a projected systematic error band a factor of four smaller than EPS09's current allowable range. The MPC-EX detector will expand our understanding of the gluon nuclear parton distribution functions, providing important information about the initial state of heavy ion collisions, and clarify how the valence parton's transverse momentum and spin correlates to the proton spin.