Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal ...angle straight phi of the pion relative to the lepton scattering plane was formed for pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinstraight phi moment of the cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.
The HERMES Spectrometer Ackerstaff, K.; Akopov, N.; Aschenauer, E.C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1998, Letnik:
417, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and
3He. These data give information on the ...spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers (micro-strip gas chambers, drift and proportional chambers) in front of and behind a 1.3
T.m magnetic field, as well as an extensive set of detectors for particle identification (a lead-glass calorimeter, a pre-shower detector, a transition radiation detector, and a threshold Cherenkov detector). Two of the main features of the spectrometer are its good acceptance and identification of both positrons and hadrons, in particular pions. These characteristics, together with the purity of the targets, are allowing HERMES to make unique contributions to the understanding of how the spins of the quarks contribute to the spin of the nucleon.
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}.
Spin asymmetries of semi-inclusive cross sections for the production of positively and negatively charged hadrons have been measured in deep-inelastic scattering of polarized positrons on polarized ...hydrogen and
3
He targets, in the kinematic range 0.023<
x<0.6 and 1 GeV
2<
Q
2<10 GeV
2. Polarized quark distributions are extracted as a function of
x for up
(u+
u
̄
) and down (
d+
d
̄
) flavors. The up quark polarization is positive and the down quark polarization is negative in the measured range. The polarization of the sea is compatible with zero. The first moments of the polarized quark distributions are presented. The isospin non-singlet combination
Δq
3 is consistent with the prediction based on the Bjorken sum rule. The moments of the polarized quark distributions are compared to predictions based on SU(3)
f
flavor symmetry and to a prediction from lattice QCD.
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.
The influence of the nuclear medium on the production of charged hadrons in semi-inclusive deep-inelastic scattering has been studied by the HERMES experiment at DESY using a 27.5 GeV positron beam. ...The differential multiplicity of charged hadrons and identified charged pions from nitrogen relative to that from deuterium has been measured as a function of the virtual photon energy \(\nu\) and the fraction z of this energy transferred to the hadron. There are observed substantial reductions of the multiplicity ratio \(R_M^{h}\) at low \(\nu\) and at high z, both of which are well described by a gluon-bremsstrahlung model of hadronization. A significant difference of the \(\nu\)-dependence of \(R_M^{h}\) is found between positive and negative hadrons. This is interpreted in terms of a difference between the formation times of protons and pions, using a phenomenological model to describe the \(\nu\)- and z-dependence of \(R_M^{h}\).
Although women veterans accounted for 4.1 percent of all veterans in 1983, they accounted for only 1.5 percent of all discharges from Veterans Administration hospitals in that year. These data ...suggest that women veterans are not utilizing their health care benefits as often as male veterans do, possibly because they are choosing to receive health care in non-VA facilities. Furthermore, the patterns of utilization for women veterans suggest a selective use of VA hospitals for serious illnesses that require protracted care. The author explores some possible explanations for this phenomenon and emphasizes the need for the VA health care system to incorporate such information in the planning of health care services for women veterans.
Cross section ratios for deep-inelastic scattering from
14N and
3He with respect to
2H have been measured by the HERMES experiment at DESY using a 27.5 GeV positron beam. The data cover a range in ...the Bjorken scaling variable
x between 0.013 and 0.65, while the negative squared four-momentum transfer
Q
2 varies from 0.5 to 15 GeV
2. The data are compared to measurements performed by NMC, E665, and SLAC on
4He and
12C, and are found to be different for
x<0.06 and
Q
2<1.5 GeV
2. The observed difference is attributed to an
A-dependence of the ratio
R=
σ
L
/
σ
T
of longitudinal to transverse deep-inelastic scattering cross sections at low
x and low
Q
2.
Five cases are described that offer evidence for the existence of the "serotonin irritation syndrome," an anxiety state associated with high cation environments, elevated serum serotonin, and ...decreased urinary 5-hydroxyindoleacetic acid. The therapeutic response and reduction in serum serotonin after treatment with methysergide and/or removal from the high-cation environment support a serotonergic basis of the anxiety.
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