Future of low-x forward physics at RHIC Bland, L. C.; Bieser, F.; Brown, R. L. ...
The European physical journal. C, Particles and fields,
08/2005, Letnik:
43, Številka:
1-4
Journal Article
Recenzirano
Odprti dostop
Comparisons of particle production from high-energy ion collisions with next-to-leading order perturbative QCD calculations show good agreement down to moderate transverse momentum values. ...Distributions of azimuthal angle differences between coincident hadrons in these collisions support a partonic origin to the particle production, again down to moderate transverse momentum values. The rapidity dependence of inclusive and coincident particle production can therefore be used to probe parton distribution functions down to small momentum fractions where theory anticipates that parton saturation could be present. This paper describes how such experiments could be completed.
The design, construction and operation of the HERMES forward (front) tracking chambers and associated electronics are described. Resolution and limited aging tests have been performed on these drift ...chambers, which use an Ar/CF
4/CO
2 (90
:
5
:
5) gas mixture. No degradation in chamber performance has been observed for a cumulative charge in excess of
9
C/
cm
.
Measurements are reported of the production of high energy
π
0 mesons at large pseudorapidity, coincident with charged hadrons at mid-rapidity, for proton+proton and deuteron+gold collisions at
s
N
N
...=
200
GeV
. The p+p cross section for inclusive
π
0 production follows expectations from next-to-leading order perturbative QCD. A suppression of the back-to-back azimuthal correlations was observed in d+Au, qualitatively consistent with the gluon saturation picture. Experimental uncertainties regarding the inclusive measurement are discussed.
A measurement of the proton spin structure function g1p(x,Q{sup 2}) in deep-inelastic scattering is presented. The data were taken with the 27.6 GeV longitudinally polarised positron beam at HERA ...incident on a longitudinally polarised pure hydrogen gas target internal to the storage ring. The kinematic range is 0.021<x<0.85 and 0.8 GeV{sup 2}<Q{sup 2}<20 GeV{sup 2}.
The STAR endcap electromagnetic calorimeter Allgower, C.E.; Anderson, B.D.; Baldwin, A.R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2003, Letnik:
499, Številka:
2
Journal Article
Recenzirano
The STAR endcap electromagnetic calorimeter will provide full azimuthal coverage for high-
p
T photons, electrons and electromagnetically decaying mesons over the pseudorapidity range 1.086⩽
η⩽2.00. ...It includes a scintillating-strip shower-maximum detector to provide π
0/γ discrimination and preshower and postshower layers to aid in distinguishing between electrons and charged hadrons. The triggering capabilities and coverage it offers are crucial for much of the spin physics program to be carried out in polarized proton–proton collisions.
Measurements of the individual multiplicities of \(\pi^+, \pi^-\) and \(\pi^0\) produced in the deep-inelastic scattering of 27.5 GeV positrons on hydrogen are presented. The average charged pion ...multiplicity is the same as for neutral pions, up to \(z \approx 0.7\), where z is the fraction of the energy transferred in the scattering process carried by the pion. This result (below \(z \approx 0.7\)) is consistent with isospin invariance. The total energy fraction associated with charged and neutral pions is \(\rm 0.51 \pm 0.01 (stat.) \pm 0.08\) (syst.) and \(\rm 0.26 \pm 0.01 (stat.) \pm 0.04 (syst.)\), respectively. For fixed z, the measured multiplicities depend on both the negative squared four momentum transfer \(Q^2\) and the Bjorken variable x. The observed dependence on \(Q^2\) agrees qualitatively with the expected behaviour based on NLO-QCD evolution, while the dependence on x is consistent with that of previous data after corrections have been made for the expected \(Q^2\)-dependence.
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