Measurement of the spin asymmetry in the photoproduction of pairs of high- p(T) hadrons at HERMES
We present a measurement of the longitudinal spin asymmetry A(||) in photoproduction of pairs of hadrons with high transverse momentum p(T). Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For h(+)h(-) pairs with p(h(1))(T)>1.5 GeV/c and p(h(2))(T)>1.0 GeV/c, the measured asymmetry is A(||) = -0. 28+/-0.12(stat)+/-0.02(syst). This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.
McIlhany
K
Yerevan Physics Institute, 375036, Yerevan, Armenia.
McKeown
RD
Meissner
F
Menden
FM
Metz
A
Meyners
N
Mikloukho
O
Miller
CA
Miller
MA
Milner
R
Most
A
Muccifora
V
Naryshkin
Y
Nathan
AM
Neunreither
F
Niczyporuk
M
Nowak
W
O'Neill
TG
Openshaw
R
Ouyang
J
Owen
BR
Pate
SF
Potashov
S
Potterveld
DH
Rakness
G
Redwine
R