2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009;
Denver, Colorado
Session T3: DNP Prize and Award Session II
3:30 PM–5:18 PM,
Monday, May 4, 2009
Room: Plaza E
Sponsoring
Unit:
DNP
Chair: William Zajc, Columbia University
Abstract ID: BAPS.2009.APR.T3.3
Abstract: T3.00003 : New Results from Spin Physics at RHIC
4:42 PM–5:18 PM
Preview Abstract
Abstract
Author:
Renee Fatemi
(University of Kentucky)
The sign and magnitude of the gluon spin contribution
($\Delta{G}$) to the spin of the proton has been a topic of
intense interest and speculation since inclusive deep inelastic
scattering experiments found the total quark spin contribution to
be surprisingly small. Starting in 2002, the Relativistic Heavy
Ion Collider (RHIC) at Brookhaven National Lab has provided
access to longitudinally and transversely polarized proton
collisions. Both PHENIX and STAR, the two largest collaborations
at RHIC, have used this data to complete a series of inclusive
hadron and jet double spin asymmetry ($A_{LL}$) measurements.
The mid-rapidity $\pi^0$ and jet results, now included in a
global analysis of existing world data, are shown to provide
significant constraints on $\Delta{G}$ within their range of
kinematic sensitivity. Recent inclusive pion and jet $A_{LL}$
measurements will be presented. Plans to measure $A_{LL}$ in
correlation channels, for example di-jets and photon-jets, and
parity violating asymmetries for identified $W^{+/-}$ in future
longitudinal proton runs will be discussed.
In addition to a successful $\Delta{G}$ program, the RHIC-Spin
community is actively contributing to the new and rapidly
expanding frontier within nucleon structure studies of transverse
spin measurements. Quantum Chromodynamics predicts an extremely
small ($\propto\frac{m_q}{\sqrt{s}}$) spin asymmetry for leading
hadron production in the reaction
$p^\uparrow{p}\rightarrow{h}+X$. Contrary to expectations,
transverse single-spin asymmetries (SSA) of up to $30\%$ were
discovered in forward particle production more than three decades
ago, and surprisingly, asymmetries of the same magnitude have
been found to persist at current RHIC center-of-mass energies.
The most recent forward $\pi^0$ and $\eta$ SSA from STAR and
PHENIX, as well as charged hadron measurements from the BRAHMS
collaboration, will be discussed and compared with theoretical
predictions.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.APR.T3.3