2nd Workshop on the QCD Structure of the Nucleon June 12-16, 2006 Villa Mondragone Monte Porzio Catone, Rome, Italy. RHIC Results on Transverse Spin. Steve Heppelmann Penn State University. Three RHIC Experiments are producing results on Transverse Single Spin Asymmetries A N.
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June 12-16, 2006
Monte Porzio Catone,
Penn State University
From Abhay Deshpande Single Spin Asymmetries A
STAR Single Spin Asymmetries A detector layout (run 5)
Run 6 (FPD++)
2006 to present
FMS Forward Meson
Run 7 2006
FMS Design Single Spin Asymmetries A
FPD Run 3-5 (2003-2005)
FPD++ Run 6 (2006)
FMS Run 7- (2006- )
y Single Spin Asymmetries A
STAR Central Region
Reconstructed di-jets from
EM calorimeter only trigger data:
2002- No charged track An Seen
@Pt~1.5 GeV An < .01
@Pt~4.5 GeV An < .16
2006- 3,000,000 dijets (-1<<2)
will be sensitive to Sivers kT;
measure predicted opening angle
transverse spin dependence.
J. Adams et al. (STAR collaboration), Phys. Rev. Lett. 92 (2004) 171801 [hep-ex/0310058].
Similar asymmetry to many lower energy
R.D. Klem et al., Phys. Rev. Lett. 36 (1976) 929;
W.H. Dragoset et al., Phys. Rev. D18 (1978) 3939;
S. Saroff et al., Phys. Rev. Lett. 64 (1990) 995;
B.E. Bonner et al., Phys. Rev. D41 (1990) 13;
K. Krueger et al, Phys. Lett. B459 (1999);
C.E. Allgower et al., Phys. Rev. D65 (2002) 092008.
But now, for the first time,
in a region where NLO PQCD calculations
fairly accurately predict the cross section.
-RHIC CNI Absolute polarization still preliminary.
-Result Averaged over azimuthal
acceptance of detectors.
-Positive XF (small angle
scattering of the polarized proton).
Run 2 Published Result.
Run 3 Preliminary Result.
-More Forward angles.
Run 3 Preliminary
Backward Angle Data.
-No significant Asymmetry
( Presented at Spin 2004:
Run 3 + Run 5 Preliminary <>=3.7,4.0
(Presented SPIN 2005 Dubna Sept 27-Oct 1)
STAR 2pp π0 + X cross sections at 200 GeV
NLO pQCD calculations by Vogelsang, et al.
Online calibration of CNI polarimeter
Data are consistent with the 1/pT expectation of pQCD
BRAHMS 2 Results
p 2 +
AN of proton and pbar
BRAHMS has obtained preliminary results for single transverse
spin asymmetries for p±,K±, p, and pbar in √s =200 GeV pp collisions
at RHIC in the xF range of 0.1 to 0.35
AN(p+) for 0.2 <x in agreement with Twist-3 calculations
- AN(K+) ~ AN(K-): positive
- AN(p) ~0, AN(pbar): positive
AN(K) in disagreement with naïve expectation from valence quark fragmentation. Need more theoretical inputs.
Current 62 GeV run will allow Brahms to extend to higher XF.
more on PHENIX analysis:
see: Christine Aidala (tomorrow)
2001-2002 transverseP~15% L= 0.15 pb-1
2003 longitudinal-spin run P~30% L=0.35 pb-1
2004 longitudinal spin P~40% L=0.12 pb-1
2005 longitudinal-spin run P~45%
w/ short transverse run L=0.15 pb-1
2006 transverse (this run)
(Radial polarization) P~55% L>2.4 pb-1
3 modules: 150X0 5.1λIVery Forward Neutron
neutronCalculation of AN
|h| < 0.35
PRL 95 (2005)