872 research outputs found
Hard-core Radius of Nucleons within the Induced Surface Tension Approach
In this work we discuss a novel approach to model the hadronic and nuclear
matter equations of state using the induced surface tension concept. Since the
obtained equations of state, classical and quantum, are among the most
successful ones in describing the properties of low density phases of strongly
interacting matter, they set strong restrictions on the possible value of the
hard-core radius of nucleons. Therefore, we perform a detailed analysis of its
value which follows from hadronic and nuclear matter properties and find the
most trustworthy range of its values: the hard-core radius of nucleons is
0.30--0.36 fm. A comparison with the phenomenology of neutron stars implies
that the hard-core radius of nucleons has to be temperature and density
dependent.Comment: 12 pages, 4 figures, references added, typos correcte
Fully-heavy tetraquark spectroscopy in the relativistic quark model
Masses of the ground and excited (1P, 2S, 1D, 2P, 3S) states of the
fully-heavy tetraquarks, composed of charm () and bottom () quarks and
antiquarks, are calculated in the diquark-antidiquark picture within the
relativistic quark model based on the quasipotential approach and quantum
chromodynamics. The quasipotentials of the quark-quark and diquark-antidiquark
interactions are constructed similarly to the previous consideration of mesons
and baryons. Relativistic effects are consistently taken into account. A
tetraquark is considered as a bound state of a diquark and an antidiquark. The
finite size of the diquark is taken into account, using the form factors of the
diquark-gluon interaction. It is shown that most of the investigated states of
tetraquarks lie above the decay thresholds into a meson pair, as a result they
can be observed only as broad resonances. The narrow state X(6900) recently
discovered in the di- production spectrum by the LHCb, CMS and ATLAS
Collaborations corresponds to an excited state of the fully-charmed tetraquark.
Other recently discovered exotic heavy resonances X(6200), X(6400), X(6600),
X(7200), X(7300) can also be interpreted as the different excitations of the
fully-charmed tetraquark.Comment: 36 pages, 2 figure
Re-entrant resonant tunneling
We study the effect of electron-electron interactions on the
resonant-tunneling spectroscopy of the localized states in a barrier. Using a
simple model of three localized states, we show that, due to the Coulomb
interactions, a single state can give rise to two resonant peaks in the
conductance as a function of gate voltage, G(Vg). We also demonstrate that an
additional higher-order resonance with Vg-position in between these two peaks
becomes possibile when interactions are taken into account. The corresponding
resonant-tunneling process involves two-electron transitions. We have observed
both these effects in GaAs transistor microstructures by studying the time
evolution of three adjacent G(Vg) peaks caused by fluctuating occupation of an
isolated impurity (modulator). The heights of the two stronger peaks exibit
in-phase fluctuations. The phase of fluctuations of the smaller middle peak is
opposite. The two stronger peaks have their origin in the same localized state,
and the third one corresponds to a co-tunneling process.Comment: 9 pages, REVTeX, 4 figure
Quantum, Multi-Body Effects and Nuclear Reaction Rates in Plasmas
Detailed calculations of the contribution from off-shell effects to the
quasiclassical tunneling of fusing particles are provided. It is shown that
these effects change the Gamow rates of certain nuclear reactions in dense
plasma by several orders of magnitude.Comment: 11 pages; change of content: added clarification of one of the
important steps in the derivatio
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