Speaker
Kensuke Okada
(Riken / BNL)
Description
To study the proton spin structure, the Relativistic Heavy Ion Collider
(RHIC) at BNL provides a unique opportunity by colliding polarized protons.
The hard subprocesses in proton-proton collisions involve gluons in
leading order, therefore measurements of cross section asymmetries
between aligned and anti aligned proton helicities give us information
about the spin dependent gluon distribution, which might hold the
longstanding missing proton spin component.
For the longitudinal spin program, the PHENIX experiment accumulated
about 10/pb of data at sqrt(s)=200GeV with roughly 60% proton beam
polarization and 0.1/pb of data at sqrt(s)=62GeV with 50% polarization.
Up until now, we have performed spin asymmetry measurements
focusing on pi0 production with the central electromagnetic
calorimeters. Despite low integrated luminosity, it was shown that
the sqrt(s)=62GeV data have comparable sensitivity to the gluon
polarization through the high x_T=2p_T/sqrt(s) region.
In addition, various channels such as partial jets, charged pions, direct
photons in the central rapidity region, large rapidity J/psi's through the
muon channel and pi0's in a newly installed large rapidity electromagnetic
calorimeter will provide complementary results.
We also measure double helicity asymmetries of the average intrinsic k_T
by 2-particle correlations,which may be sensitive to the partonic orbital
angular momentum, another possible contribution to the proton spin.
In this talk, we report recent results and plans of the PHENIX
longitudinal spin program.
Author
Kensuke Okada
(Riken / BNL)
