The (spin) structure of the nucleon van der Steenhoven, G.
The European physical journal. A, Hadrons and nuclei,
11/2003, Volume:
18, Issue:
2-3
Journal Article
Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The ...asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.
A single-spin asymmetry in the distribution of exclusively produced
π
+ mesons azimuthally around the virtual photon direction relative to the lepton scattering plane has been measured for the first ...time in deep-inelastic scattering of positrons off longitudinally polarized protons. Integrated over the experimental acceptance, the sin
φ moment of the polarization asymmetry of the cross section is measured to be −0.18±0.05(stat.)±0.02(syst.). The asymmetry is also studied as a function of the relevant kinematic variables, and its magnitude is found to grow with decreasing
x and increasing −
t and vanish at
t→
t
min (where
x is the Bjorken scaling variable and
t is the squared four-momentum transferred to the nucleon).
We conducted a 1-year follow-up study on back pain among 196 men taking up golf. A questionnaire on individual characteristics, occupation, sports, and back pain was distributed at the start of the ...study and was followed by another questionnaire after 12 months. Eleven percent of the original subjects (25 of 211) were lost to followup, but withdrawal from the survey was not associated with health status. In the baseline survey (N = 221), the self-reported lifetime cumulative incidence of back pain was 63%; 28% reported back pain during the month before answering the questionnaire, and 13% reported current back pain. Athletes had an increased odds ratio of 2.1 (95% confidence interval, 1.1 to 4.0) for previous back pain. During the 12 months between the surveys, the incidence of first-time back pain was 8% and the incidence of recurrent back pain was about 45%. Men involved in golf and another sport demonstrated a risk of 1.4 for recurrence of back pain, compared with men playing golf only. Six subjects attributed the recurrent back pain to playing golf. Given the high proportion of athletes in this study (68%), the risk factor of playing golf failed to demonstrate an additional significant effect on the general relationship between sport and back pain.
A series of semi-inclusive deep-inelastic scattering measurements on deuterium, helium, neon, krypton, and xenon targets has been performed in order to study hadronization. The data were collected ...with the HERMES detector at the DESY laboratory using a 27.6 GeV positron or electron beam. Hadron multiplicities on nucleus
A relative to those on the deuteron,
R
A
h
, are presented for various hadrons (
π
+
,
π
−
,
π
0
,
K
+
,
K
−
,
p, and
p
¯
) as a function of the virtual-photon energy
ν, the fraction
z of this energy transferred to the hadron, the photon virtuality
Q
2
, and the hadron transverse momentum squared
p
t
2
. The data reveal a systematic decrease of
R
A
h
with the mass number
A for each hadron type
h. Furthermore,
R
A
h
increases (decreases) with increasing values of
ν (
z), increases slightly with increasing
Q
2
, and is almost independent of
p
t
2
, except at large values of
p
t
2
. For pions two-dimensional distributions also are presented. These indicate that the dependences of
R
A
π
on
ν and
z can largely be described as a dependence on a single variable
L
c
, which is a combination of
ν and
z. The dependence on
L
c
suggests in which kinematic conditions partonic and hadronic mechanisms may be dominant. The behaviour of
R
A
π
at large
p
t
2
constitutes tentative evidence for a partonic energy-loss mechanism. The
A-dependence of
R
A
h
is investigated as a function of
ν,
z, and of
L
c
. It approximately follows an
A
α
form with
α
≈
0.5
–
0.6
.
The virtual photon absorption cross section differences
σ
1/2−
σ
3/2 for the proton and neutron have been determined from measurements of polarised cross section asymmetries in deep inelastic ...scattering of 27.5 GeV longitudinally polarised positrons from polarised
1
H and
3
He internal gas targets. The data were collected in the region above the nucleon resonances in the kinematic range
ν< 23.5 GeV and 0.8 GeV
2<
Q
2< 12 GeV
2. For the proton the contribution to the generalised Gerasimov-Drell-Hearn integral was found to be substantial and must be included for an accurate determination of the full integral. Furthermore the data are consistent with a QCD next-to-leading order fit based on previous deep inelastic scattering data. Therefore higher twist effects do not appear significant.
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0S→pπ+π−. A peak is observed in the pK0S invariant mass spectrum at ...1528±2.6(stat)±2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental resolution of σ=4.3–6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Θ+(uudds̄) pentaquark baryon. No signal for an hypothetical Θ++ baryon was observed in the pK+ invariant mass distribution. The absence of such a signal indicates that an isotensor Θ is excluded and an isovector Θ is unlikely.
The data acquisition system for the ANTARES neutrino telescope Ameli, F.; Anton, G.; Anvar, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2007, 2007-1-00, Volume:
570, Issue:
1
Journal Article
Peer reviewed
Open access
The ANTARES neutrino telescope is being constructed in the Mediterranean Sea. It consists of a large three-dimensional array of photo-multiplier tubes. The data acquisition system of the detector ...takes care of the digitisation of the photo-multiplier tube signals, data transport, data filtering, and data storage. The detector is operated using a control program interfaced with all elements. The design and the implementation of the data acquisition system are described.
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