| Abstract: | A study is reported of the same- and opposite-sign charge-dependent azimuthal
correlations with respect to the event plane in Au+Au collisions at 200 GeV.
The charge multiplicity asymmetries between the up/down and left/right
hemispheres relative to the event plane are utilized. The contributions from
statistical fluctuations and detector effects were subtracted from the
(co-)variance of the observed charge multiplicity asymmetries. In the mid- to
most-central collisions, the same- (opposite-) sign pairs are preferentially
emitted in back-to-back (aligned on the same-side) directions. The charge
separation across the event plane, measured by the difference, $Delta$,
between the like- and unlike-sign up/down $-$ left/right correlations, is
largest near the event plane. The difference is found to be proportional to the
event-by-event final-state particle ellipticity (via the observed second-order
harmonic $v_2^{
m obs}$, where $Delta=(1.3pm1.4({
m
stat})^{+4.0}_{-1.0}({
m syst})) imes10^{-5}+(3.2pm0.2({
m
stat})^{+0.4}_{-0.3}({
m syst})) imes10^{-3}v_2^{
m obs}$ for 20-40% Au+Au
collisions. The implications for the proposed chiral magnetic effect (cme) are
discussed. |
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