We present a new measurement of the spin-dependent structure function
g
1
d
of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range ...0.003 <
x < 0.7 and 1 GeV
2 <
Q
2 < 60 GeV
2. This structure function is found to be negative at small
x. The first moment
Γ
1
d=∫
0
1
g
1
dd
x evaluated at
Q
0
2 = 10 GeV
2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of
Γ
1
p
, we obtain
Γ
1
p
−
Γ
1
n
= 0.199 ± 0.038 which agrees with the Bjorken sum rule.
We present a new measurement of the virtual photon proton asymmetry
A
1
p from deep inelastic scattering of polarized muons on polarized protons in the kinematic range 0.0008 <
x < 0.7 and 0.2 <
Q
2 ...< 100 GeV
2. With this, the statistical uncertainty of our measurement has improved by a factor of 2 compared to our previous measurements. The spin-dependent structure function
g
1
p is determined for the data with
Q
2 > 1 GeV
2. A perturbative QCD evolution in next-to-leading order is used to determine
g
1
p(
x) at a constant
Q
2. At
Q
2 = 10 GeV
2 we find, in the measured range,
∫
0.003
0.7
g
1
P(x)
dx=0.139±0.006 (
stat) ±0.008 (
syst) ±0.006(
evol)
. The value of the first moment
Г
1
P=
∫
0
1
g
1
p(x)
d x
of
g
1
p depends on the approach used to describe the behaviour of
g
1
p at low
x. We find that the Ellis-Jaffe sum rule is violated. With our published result for
Γ
1
d we confirm the Bjorken sum rule with an accuracy of ≈ 15% at the one standard deviation level.
We present a measurement of the muon neutrino–nucleon inclusive charged current cross section, off an isoscalar target, in the neutrino energy range 2.5⩽Eν⩽40 GeV. The significance of this ...measurement is its precision, ±4% in 2.5⩽Eν⩽10 GeV, and ±2.6% in 10⩽Eν⩽40 GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.
An application of nuclear emulsions with automatic scanning Stiegler, Ulrich
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2000, Letnik:
454, Številka:
1
Journal Article
Recenzirano
It will be shown that emulsions can be mass produced and automatically scanned in large quantities. CHORUS demonstrated the first large-scale application. Emulsions can be used to search for rare ...events in a high track density environment like DONUT. Heavy target masses as in OPERA are possible. The use of emulsions is getting more and more easier.
Results from the
ν
τ
appearance search in a neutrino beam using the full NOMAD data sample are reported. A new analysis unifies all the hadronic
τ decays, significantly improving the overall ...sensitivity of the experiment to oscillations. The “blind analysis” of all topologies yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90% CL allowed region in the sin
22
θ
μτ
–
Δm
2 plane which includes sin
22
θ
μτ
<3.3×10
−4 at large
Δm
2 and
Δm
2< 0.7 eV
2/
c
4 at sin
22
θ
μτ
=1. The corresponding contour in the
ν
e
→
ν
τ
oscillation hypothesis results in sin
22
θ
eτ
<1.5×10
−2 at large
Δm
2 and
Δm
2<5.9 eV
2/
c
4 at sin
22
θ
eτ
=1. We also derive limits on effective couplings of the
τ lepton to
ν
μ
or
ν
e
.
A review on the internal spin structure of the proton and neutron is presented, with emphasis on inclusive deep inelastic scattering of polarized electrons and muons on proton and deuteron targets.
A search was made among νμ charged current events collected in the NOMAD experiment for the reaction: νμ+N→μ−+D★++hadrons↪D0+π+↪K−+π+. A high purity D★+ sample composed of 35 events was extracted. ...The D★+ yield in νμ charged current interactions was measured to be T=(0.79±0.17(stat.)±0.10(syst.))%. The mean fraction of the hadronic jet energy taken by the D★+ is 0.67±0.02(stat.)±0.02(syst.). The distributions of the fragmentation variables z, PT2 and xF for D★+ are also presented.
A study of strange particle production in
ν
μ
charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles
(
K
0
s
,Λ,
Λ
̄
) have been ...measured. Mean multiplicities are reported as a function of the event kinematic variables
E
ν
,
W
2 and
Q
2 as well as of the variables describing particle behaviour within a hadronic jet:
x
F
, z and
p
T
2. Decays of resonances and heavy hyperons with identified K
0
s and
Λ in the final state have been analyzed. Clear signals corresponding to K
★±, Σ
★±,
Ξ
− and
Σ
0 have been observed.
The
Λ polarization in
ν
μ
charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed
Λ 's) is more than an order of magnitude larger than that of ...previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the
W -boson direction which is enhanced in the target fragmentation region:
P
x(x
F<0)=−0.21±0.04
(stat)±0.02
(sys)
. In the current fragmentation region we find
P
x(x
F>0)=−0.09±0.06
(stat)±0.03
(sys)
. These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the
Λ production plane) has been observed for the first time in a neutrino experiment:
P
y=−0.22±0.03
(stat)±0.01
(sys)
. The dependence of the absolute value of
P
y
on the
Λ transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron–hadron experiments.
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