2,488 research outputs found
The mass spectrum of double heavy baryons in new potential quark models
A new approach to study the mass spectrum of double heavy baryons (QQâČq) containing strange and charmed quarks is proposed. It is based on the separation of variables in the Schrodinger equation in the prolate spheroidal coordinates. Two nonrelativistic potential models are considered. In the first model, the interaction potential of the quarks is the sum of the Coulomb and non-spherically symmetrical linear confinement potential. In the second model it is assumed that the quark confinement provided by a spherically symmetric harmonic oscillator potential. In both models the mass spectrum is calculated, and a comparison with previous results from other models is performed
Correlation between heavy flavour production and multiplicity in pp and p-Pb collisions at high energy in the multi-pomeron exchange model
The multiplicity dependence of heavy flavour production in pp-collisions at
LHC energies is studied in the framework of the multi-pomeron exchange model.
The model is introducing the string-string interaction collectivity effects in
pp collisions, which modifies multiplicity and transverse momenta, leading to
the non-trivial mean pt vs. multiplicity (_Nch - Nch) correlation. The
string collectivity strength parameter is fixed by experimental data on
multiplicity and transverse momentum correlation in a wide energy range (from
ISR to LHC). The particles discrimination is implemented according to Schwinger
mechanism taking into account the strong decays of hadron resonances. We
demonstrate, that the faster-than-linear growth of the open charm production
with the event charged particle multiplicity, observed in experimental pp high
energy collisions, can be explained by the modification of the string tension
due to the increasing overlap and interaction of quark-gluon strings. The model
is extended for p-A interactions and the calculations for p-Pb collisions are
performed.The research was supported by the grant of the Russian Science Foundation (project 16-12-10176)
Multipomeron Model with Collective Effects for High-Energy Hadron Collisions
We propose the generalized multipomeron exchange model for multiparticle production in high-energy protonâproton, protonânucleus and heavy-ion collisions. For all of these systems, we consider collectivity effects based on the quarkâgluon string fusion concept, where new types of particle-emitting sourcesâstrings with higher tensionâare produced. We obtained the model parameters using the data on the multiplicity dependence of the mean transverse momentum of charged particles in pp and ppÂŻ collisions over a wide energy range (from ISR to LHC). We calculated the yields of strange, multi-strange and charm particles as a function of multiplicity for pp, p-Pb and Pb-Pb collisions at the LHC energy and compared the results with the experimental data.This research has been conducted with partial financial support from St. Petersburg State University (project No. 93025435). The application of multivariate Bayesian Gaussian process and the principal component decomposition studies was funded by Russian Science Foundation grant No. 17-72-20045
Vector Centrality in Hypergraphs
Identifying the most influential nodes in networked systems is of vital
importance to optimize their function and control. Several scalar metrics have
been proposed to that effect, but the recent shift in focus towards network
structures which go beyond a simple collection of dyadic interactions has
rendered them void of performance guarantees. We here introduce a new measure
of node's centrality, which is no longer a scalar value, but a vector with
dimension one lower than the highest order of interaction in a hypergraph. Such
a vectorial measure is linked to the eigenvector centrality for networks
containing only dyadic interactions, but it has a significant added value in
all other situations where interactions occur at higher-orders. In particular,
it is able to unveil different roles which may be played by the same node at
different orders of interactions -- information that is otherwise impossible to
retrieve by single scalar measures. We demonstrate the efficacy of our measure
with applications to synthetic networks and to three real world hypergraphs,
and compare our results with those obtained by applying other scalar measures
of centrality proposed in the literature.Comment: 10 pages, 9 figure
The influence of the dechanneling process on the photon emission by an ultra-relativistc positron channeling in a periodically bent crystal
We investigate, both analytically and numerically, the influence of the
dechanneling process on the parameters of undulator radiation generated by
ultra-relativistic positron channelling along a crystal plane, which is
periodically bent. The bending might be due either to the propagation of a
transverse acoustic wave through the crystal, or due to the static strain as it
occurs in superlattices. In either case the periodically bent crystal serves as
an undulator which allows to generate X-ray and gamma-radiation.
We propose the scheme for accurate quantitative treatment of the radiation in
presence of the dechanneling. The scheme includes (i) the analytic expression
for spectral-angular distribution which contains, as a parameter, the
dechanneling length, (ii) the simulation procedure of the dechanneling process
of a positron in periodically bent crystals. Using these we calculate the
dechanneling lengths of 5 GeV positrons channeling in Si, Ge and W crystals,
and the spectral-angular and spectral distributions of the undulator over broad
ranges of the photons. The calculations are performed for various parameters of
the channel bending.Comment: published in J. Phys. G: Nucl. Part. Phys. 27 (2001) 95-125,
http://www.iop.or
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
Measurements of multi-particle azimuthal correlations (cumulants) for charged
particles in p-Pb and Pb-Pb collisions are presented. They help address the
question of whether there is evidence for global, flow-like, azimuthal
correlations in the p-Pb system. Comparisons are made to measurements from the
larger Pb-Pb system, where such evidence is established. In particular, the
second harmonic two-particle cumulants are found to decrease with multiplicity,
characteristic of a dominance of few-particle correlations in p-Pb collisions.
However, when a gap is placed to suppress such correlations,
the two-particle cumulants begin to rise at high-multiplicity, indicating the
presence of global azimuthal correlations. The Pb-Pb values are higher than the
p-Pb values at similar multiplicities. In both systems, the second harmonic
four-particle cumulants exhibit a transition from positive to negative values
when the multiplicity increases. The negative values allow for a measurement of
to be made, which is found to be higher in Pb-Pb collisions at
similar multiplicities. The second harmonic six-particle cumulants are also
found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find
which is indicative of a Bessel-Gaussian
function for the distribution. For very high-multiplicity Pb-Pb
collisions, we observe that the four- and six-particle cumulants become
consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and
Pb-Pb are measured. These are found to be similar for overlapping
multiplicities, when a gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87
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