1,033 research outputs found
On Relativistic Models in the Equilibrium Statistical Mechanics
Relativistic effects in the thermodynamical properties of interacting
particle systems are investigated within the framework of the relativistic
direct interaction theory in various forms of dynamics. In the front form of
relativistic dynamics an exactly solvable model of a one-dimensional hard
spheres gas is formulated and an equation of state and thermodynamical
potentials for such a gas are found. Weakly-relativistic corrections to the
thermodynamical functions of the dilute gas with short-range interactions are
discussed on the basis of the approximately relativistic Hamiltonian function
in the instant form of dynamics.Comment: 16 pages, no figures, submit. to Cond. Matt. Phy
Beta decays in investigations and searches for rare effects
Current status of experimental investigations of rare single beta decays
(48Ca, 50V, 96Zr, 113Cd, 113mCd, 115In, 123Te, 180mTa, 222Rn) is reviewed.
Nuclei which decay through single beta decay very often constitute backgrounds
in studies of rare effects like double beta decay, solar neutrinos or dark
matter. Summary of correction factors used in description of forbidden beta
decays is also briefly given.Comment: 4 pages, contribution to the MEDEX'2017 conference, one more
acknowledgment adde
False starts in history of searches for double beta decay, or Discoverless double beta decay
A collection of stories is presented on discoveries of double beta decay
(including neutrinoless one) which were refuted in the subsequent
investigations.Comment: 6 pages, contribution to the Workshop on Calculation of Double Beta
Decay Matrix Elements (MEDEX'11), Prague, June 13-16, 201
Semi-empirical calculation of quenching factors for ions in scintillators
Semi-empirical method of calculation of quenching factors for scintillators
is described. It is based on classical Birks formula with the total stopping
powers for electrons and ions which are calculated with the ESTAR and SRIM
codes, respectively. Method has only one fitting parameter (the Birks factor
kB) which can have different values for the same material in different
conditions of measurements and data treatment. A hypothesis is used that, once
the kB value is obtained by fitting data for particles of one kind and in some
energy region (e.g. for a few MeV alpha particles from internal contamination
of a detector), it can be applied to calculate quenching factors for particles
of another kind and for another energies (e.g. for low energy nuclear recoils)
if all data are measured in the same experimental conditions and are treated in
the same way. Applicability of the method is demonstrated on many examples
including materials with different mechanisms of scintillation: organic
scintillators (solid C8H8, and liquid C16H18, C9H12); crystal scintillators
(pure CdWO4, PbWO4, ZnWO4, CaWO4, CeF3, and doped CaF2(Eu), CsI(Tl), CsI(Na),
NaI(Tl)); liquid noble gases (LXe). Estimations of quenching factors for
nuclear recoils are also given for some scintillators where experimental data
are absent (CdWO4, PbWO4, CeF3, Bi4Ge3O12, LiF, ZnSe).Comment: 32 pages; accepted in Astropart. Phy
Isotropic Forms of Dynamics in the Relativistic Direct Interaction Theory
The Lagrangian relativistic direct interaction theory in the various forms of
dynamics is formulated and its connections with the Fokker-type action theory
and with the constrained Hamiltonian mechanics are established. The motion of
classical two-particle system with relativistic direct interaction is analysed
within the framework of isotropic forms of dynamics in the two- and
four-dimensional space-time. Some relativistic exactly solvable
quantum-mechanical models are also discussed.Comment: 49 pages, 12 figures, Latex2
Quasi-Relativistic Center-of-Mass Variables in Applications
Collective center-of-mass variables are introduced in the Lagrangian
formalism of the relativistic classical mechanics of directly interacting
particles. It is shown that the transition to the Hamiltonian formalism leads
to the Bakamjian-Thomas model. The quantum-mechanical system consisting of two
spinless particles is investigated. Quasi-relativistic corrections to the
discrete energy spectrum are calculated for some Coulomb-like interactions
having field theoretical analogues.Comment: 12 pages, Latex2
Feasibility study of the observation of the neutrino accompanied double beta-decay of Ge-76 to the 0+(1) excited state of Se-76 using segmented germanium detectors
Neutrino accompanied double beta-decay of Ge-76 can populate the ground state
and the excited states of Se-76. While the decay to the ground state has been
observed with a half-life of 1.74 +0.18 -0.16 10^21 years, decays to the
excited states have not yet been observed. Nuclear matrix elements depend on
details of the nuclear transitions. A measurement of the half-life of the
transition considered here could help to reduce the uncertainties of the
calculations of the nuclear matrix element for the neutrinoless double beta
decay of Ge-76. This parameter relates the half-life of the process to the
effective Majorana neutrino mass. The results of a feasibility study to detect
the neutrino accompanied double beta-decay of Ge-76 to the excited states of
Se-76 are presented in this paper. Segmented germanium detectors were assumed
in this study. Such detectors, enriched in Ge-76 to a level of about 86%, will
be deployed in the GERDA experiment located at the INFN Gran Sasso National
Laboratory, Italy. It is shown that the decay of Ge-76 to the 1122 keV 0+ level
of Se-76 can be observed in GERDA provided that the half-life of the process is
in the range favoured by the present calculations which is 7.5 10^21 y to 3.1
10^23 y.Comment: 18 pages, 4 figures. Submitted to Nucl. Phys.
Spontaneous double alpha decay: First experimental limit and prospects of investigation
Nuclear decays with simultaneous emission of two alpha particles are
energetically possible for a number of nuclides. Prospects of searching for
such kind of decay for nuclides present in the natural isotopic composition of
elements are discussed here. The first experimental limit on half-life for
2alpha decay is set for 209Bi as T1/2 > 2.9e20 y at 90% C.L., using the data of
work [P. de Marcillac et al., Nature 422 (2003) 876]. Theoretical T1/2
estimations for the process are also given. Using these values, which are on
the level of 1e33 y or more, one can conclude that the prospects of
experimental observation of 2alpha decay are very pessimistic.Comment: 8 p., submitted to Nuclear Physics and Atomic Energ
Classical relativistic systems of charged particles in the front form of dynamics and the Liouville equation
Classical relativistic system of point particles coupled with an
electromagnetic field is considered in the three-dimensional representation.
The gauge freedom connected with the chronometrical invariance of the
four-dimensional description is reduced by use of the geometrical concept of
the forms of relativistic dynamics. The remainder gauge degrees of freedom of
the electromagnetic potential are analysed within the framework of Dirac's
constrained Hamiltonian mechanics in the front form of dynamics. The results
are implemented to the problems of relativistic statistical mechanics. Based on
the corresponding Liouville equation the classical partition function of the
system is written down in a gauge-invariant manner and an integration over
field variables is performed.Comment: 19 pages, no figure
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