Measurements of open charm and beauty production cross sections in deep inelastic
ep
scattering at HERA from the H1 and ZEUS Collaborations are combined. Reduced cross sections are obtained in the ...kinematic range of negative four-momentum transfer squared of the photon
2.5
GeV
2
≤
Q
2
≤
2000
GeV
2
and Bjorken scaling variable
3
·
10
-
5
≤
x
Bj
≤
5
·
10
-
2
. The combination method accounts for the correlations of the statistical and systematic uncertainties among the different datasets. Perturbative QCD calculations are compared to the combined data. A next-to-leading order QCD analysis is performed using these data together with the combined inclusive deep inelastic scattering cross sections from HERA. The running charm- and beauty-quark masses are determined as
m
c
(
m
c
)
=
1
.
290
-
0.041
+
0.046
(
exp
/
fit
)
-
0.014
+
0.062
(
model
)
-
0.031
+
0.003
(
parameterisation
)
GeV and
m
b
(
m
b
)
=
4
.
049
-
0.109
+
0.104
(
exp
/
fit
)
-
0.032
+
0.090
(
model
)
-
0.031
+
0.001
(
parameterisation
)
GeV
.
The first measurement of lepton-jet momentum imbalance and azimuthal correlation in lepton-proton scattering at high momentum transfer is presented. These data, taken with the H1 detector at HERA, ...are corrected for detector effects using an unbinned machine learning algorithm (multifold), which considers eight observables simultaneously in this first application. The unfolded cross sections are compared with calculations performed within the context of collinear or transverse-momentum-dependent factorization in quantum chromodynamics as well as Monte Carlo event generators.
It has been shown recently that diamond-like carbon (DLC) with a sp
3 fraction above 60% is a better wall coating material for ultracold neutron applications than beryllium. We report on results of ...Raman spectroscopic and XPS measurements obtained for diamond-like carbon coated neutron guides produced in a new facility, which is based on pulsed laser deposition at 193
nm. For diamond-like carbon coatings on small stainless steel substrates we find sp
3 fractions in the range from 60 to 70% and showing slightly increasing values with laser pulse energy and pulse repetition rate.
Large-scale integration of new renewables requires substantial increases of transmission capacity on existing transmission corridors. To limit land use, overhead transmission lines have been widely ...built as multicircuit lines. On these, changing one ac circuit to dc to increase transmission capacity leads to lines with hybrid ac/dc towers. Since practically no operational experience with such hybrid lines exists to date, questions such as superimposed ac and dc fields intensified by corona-generated space charges arise. In this paper, a method to simulate these ion-flow fields using the discontinuous Galerkin method is for the first time applied to hybrid towers. Ways to considerably reduce the computational effort of the problem are discussed. The results indicate that hybrid lines are feasible in reference to space-charge-related problems. Shielding the ground is possible at the expense of increased coupling between the ac and dc circuits.
An efficient gravitational spectrometer for ultracold neutrons Geltenbort, P.; Göltl, L.; Henneck, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2010, Letnik:
624, Številka:
1
Journal Article
Recenzirano
We report on the design and construction of an efficient gravitational spectrometer for ultracold neutrons. The spectrometer is suited to experiments that can greatly profit from knowledge of the ...neutron energy spectrum without losing available statistics, such as many of the current precision experiments that use ultracold neutrons.
The description of the apparatus is complemented by the results of the first test measurements which served as a proof of principle and showed its capability of discriminating between different UCN energy ranges. The measurements showed the expected behavior and are in qualitative agreement with Monte Carlo simulations.
The quantum numbers of the X(3872) meson are determined to be J(PC)=1(++) based on angular correlations in B(+)→X(3872)K(+) decays, where X(3872)→π(+)π(-)J/ψ and J/ψ→μ(+)μ(-). The data correspond to ...1.0 fb(-1) of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements J(PC)=2(-+) is rejected with a confidence level equivalent to more than 8 Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
For the first time, ultracold neutrons have been stored in a volume formed of foils coated with diamond-like carbon. The coefficients for loss,
η, and depolarization,
β, per wall collision were ...determined simultaneously. The results for different samples,
η
∼
10
−4
and
β
∼
10
−5
–
10
−6
, are among the best values measured for high Fermi potential materials without elaborate surface pre-treatment. Thin foil storage material will be widely applicable, e.g., in neutron
β-decay studies.
Cross sections for elastic and proton-dissociative photoproduction of
J
/
ψ
mesons are measured with the H1 detector in positron-proton collisions at HERA. The data were collected at
ep
...centre-of-mass energies
and
, corresponding to integrated luminosities of
and
, respectively. The cross sections are measured as a function of the photon-proton centre-of-mass energy in the range 25<
W
γp
<110 GeV. Differential cross sections d
σ
/d
t
, where
t
is the squared four-momentum transfer at the proton vertex, are measured in the range |
t
|<1.2 GeV
2
for the elastic process and |
t
|<8 GeV
2
for proton dissociation. The results are compared to other measurements. The
W
γp
and
t
-dependences are parametrised using phenomenological fits.
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