5,612 research outputs found
The Distribution of Constituent Charm Quarks in the Hadron
Using a statistical approach in the framework of non-covariant perturbation
theory the distributions for light and charmed quarks in the hadron have been
derived, taking into account the mass of the charmed quark. The parameters of
the model have been extracted from the comparison with NA3 data on
hadroproduction of J/psi particles. A reanalysis of the EMC data on charm
production in muon-nucleon scattering has been performed. It has been found in
comparison with the conventional source of charmed quarks from photon-gluon
fusion, that the EMC data indicate the presence of an additional contribution
from deep-inelastic scattering on charmed quarks at large x. The resulting
admixture of the Fock states, containing charmed quarks in the decomposition of
the proton wave function is of the order of 1%. The approach presented for the
excitation of the Fock states with charmed quarks can also be applied to states
with beauty quarks as well as to the hadronic component of the virtual photon
(resolved photon component).Comment: 23 pages, 4 PostScript figures, Latex2e. In revised version in
comparison with the original one all (?) mistypings have been corrected, one
more thank has been added and the comparison of the pion and the proton J/psi
production is described in more detai
Observation of the parallel-magnetic-field-induced superconductor-insulator transition in thin amorphous InO films
We study the response of a thin superconducting amorphous InO film with
variable oxygen content to a parallel magnetic field. A field-induced
superconductor-insulator transition (SIT) is observed that is very similar to
the one in normal magnetic fields. As the boson-vortex duality, which is the
key-stone of the theory of the field-induced SIT, is obviously absent in the
parallel configuration, we have to draw conclusion about the theory
insufficiency.Comment: 3 pages, 4 figure
Scaling analysis of the magnetic-field-tuned quantum transition in superconducting amorphous In-O films
We have studied the magnetic-field-tuned superconductor-insulator quantum
transition (SIT) in amorphous In-O films with different oxygen content and,
hence, different electron density. While for states of the film near the
zero-field SIT the two-dimensional scaling behaviour is confirmed, for deeper
states in the superconducting phase the SIT scenario changes: in addition to
the scaling function that describes the conductivity of fluctuation-induced
Cooper pairs, there emerges a temperature-dependent contribution to the film
resistance. This contribution can originate from the conductivity of normal
electrons.Comment: 4 pages, 5 figures; accepted for publication in JETP Lett. 71 (4),
200
Baikal-GVD: status and prospects
Baikal-GVD is a next generation, kilometer-scale neutrino telescope under
construction in Lake Baikal. It is designed to detect astrophysical neutrino
fluxes at energies from a few TeV up to 100 PeV. GVD is formed by multi-megaton
subarrays (clusters). The array construction started in 2015 by deployment of a
reduced-size demonstration cluster named "Dubna". The first cluster in its
baseline configuration was deployed in 2016, the second in 2017 and the third
in 2018. The full scale GVD will be an array of ~10000 light sensors with an
instrumented volume of about 2 cubic km. The first phase (GVD-1) is planned to
be completed by 2020-2021. It will comprise 8 clusters with 2304 light sensors
in total. We describe the design of Baikal-GVD and present selected results
obtained in 2015-2017.Comment: 9 pages, 8 figures. Conference proceedings for QUARKS201
Neutralinos and the Origin of Radio Halos in Clusters of Galaxies
We assume that the supersymmetric lightest neutralino is a good candidate for
the CDM and explore the possibility to produce diffuse radio emission from
high-energy electrons arising from the neutralino annihilation in galaxy
clusters whose intracluster medium is filled with a large-scale magnetic field.
We show that these electrons fit the population of seed relativistic electrons
postulated in many models for the origin of cluster radio halos. For magnetic
fields with central values G (depending on the DM profile),
the population of seed relativistic electrons from neutralino annihilation can
fit the radio halo spectra of Coma and 1E0657-56. The shape and the frequency
extension of the radio halo spectra are connected with the mass and physical
composition of the neutralino. A pure-gaugino neutralino with mass GeV can reasonably fit the spectra of both Coma and 1E0657-56. This
model provides a number of extra predictions that make it definitely testable.
On the one hand, it agrees with the observations that {\it (i)} the radio halo
is centered on the cluster dynamical center, usually coincident with the X-ray
center, {\it (ii)} the radio halo surface brightness is similar to the X-ray
one, and {\it (iii)} the monochromatic radio luminosity at 1.4 GHz correlates
strongly with the IC gas temperature. On the other hand, the model predicts
that radio halos should be present in every cluster, which is not actually
observed, although the predicted radio halo luminosities can change by a large
amount (), depending on the amplitude and the structure of
the IC magnetic field. Also, neutral pions arising from neutralino annihilation
should give rise to substantial gamma-ray emission that could be tested by the
next generation gamma-ray experiments.Comment: 49 pages, 11 Figures, Latex (using epsfig), submitted to The
Astrophysical Journal. submitted to The Astrophysical Journa
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some
references added, minor typos correcte
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