103 research outputs found
An analysis of a minimal vectorlike extension of the Standard Model
We analyze an extension of the Standard Model with an additional SU(2)
hypercolor gauge group keeping the Higgs boson as a fundamental field.
Vectorlike interactions of new hyperquarks with the intermediate vector bosons
are explicitly constructed. We also consider pseudo-Nambu--Goldstone bosons
caused by the symmetry breaking SU(4)-> Sp(4). A specific global symmetry of
the model with zero hypercharge of the hyperquark doublets ensures the
stability of a neutral pseudoscalar field. Some possible manifestations of the
lightest states at colliders are also examined.Comment: 16 pages, 1 table, v.2: minor modification, reference is added,
formula (62) is correcte
Collisional and thermal ionization of sodium Rydberg atoms I. Experiment for nS and nD atoms with n=8-20
Collisional and thermal ionization of sodium nS and nD Rydberg atoms with
n=8-20 has been studied. The experiments were performed using a two-step pulsed
laser excitation in an effusive atomic beam at atom density of about 2 10^{10}
cm^{-3}. Molecular and atomic ions from associative, Penning, and thermal
ionization processes were detected. It has been found that the atomic ions were
created mainly due to photoionization of Rydberg atoms by photons of blackbody
radiation at the ambient temperature of 300K. Blackbody ionization rates and
effective lifetimes of Rydberg states of interest were determined. The
molecular ions were found to be from associative ionization in Na(nL)+Na(3S)
collisions. Rate constants of associative ionization have been measured using
an original method based on relative measurements of Na_{2}^{+} and Na^{+} ion
signals.Comment: 23 pages, 10 figure
Ionization of Sodium and Rubidium nS, nP and nD Rydberg atoms by blackbody radiation
Results of theoretical calculations of ionization rates of Rb and Na Rydberg
atoms by blackbody radiation (BBR) are presented. Calculations have been
performed for nS, nP and nD states of Na and Rb, which are commonly used in a
variety of experiments, at principal quantum numbers n=8-65 and at three
ambient temperatures of 77, 300 and 600 K. A peculiarity of our calculations is
that we take into account the contributions of BBR-induced redistribution of
population between Rydberg states prior to photoionization and field ionization
by extraction electric field pulses. The obtained results show that these
phenomena affect both the magnitude of measured ionization rates and shapes of
their dependencies on n. The calculated ionization rates are compared with the
results of our earlier measurements of BBR-induced ionization rates of Na nS
and nD Rydberg states with n=8-20 at 300 K. A good agreement for all states
except nS with n>15 is observed. We also present the useful analytical formulae
for quick estimation of BBR ionization rates of Rydberg atoms.Comment: 14 pages, 6 figures, 6 tables in Appendi
Autoionization of an ultracold Rydberg gas through resonant dipole coupling
We investigate a possible mechanism for the autoionization of ultracold
Rydberg gases, based on the resonant coupling of Rydberg pair states to the
ionization continuum. Unlike an atomic collision where the wave functions begin
to overlap, the mechanism considered here involves only the long-range dipole
interaction and is in principle possible in a static system. It is related to
the process of intermolecular Coulombic decay (ICD). In addition, we include
the interaction-induced motion of the atoms and the effect of multi-particle
systems in this work. We find that the probability for this ionization
mechanism can be increased in many-particle systems featuring attractive or
repulsive van der Waals interactions. However, the rates for ionization through
resonant dipole coupling are very low. It is thus unlikely that this process
contributes to the autoionization of Rydberg gases in the form presented here,
but it may still act as a trigger for secondary ionization processes. As our
picture involves only binary interactions, it remains to be investigated if
collective effects of an ensemble of atoms can significantly influence the
ionization probability. Nevertheless our calculations may serve as a starting
point for the investigation of more complex systems, such as the coupling of
many pair states proposed in [Tanner et al., PRL 100, 043002 (2008)]
Broadening and intensity redistribution in the Na() hyperfine excitation spectra due to optical pumping in the weak excitation limit
Detailed analysis of spectral line broadening and variations in relative
intensities of hyperfine spectral components due to optical pumping is
presented. Hyperfine levels of sodium and levels are
selectively excited in a supersonic beam at various laser intensities under the
conditions when optical pumping time is shorter than transit time of atoms
through the laser beam. The excitation spectra exhibit significant line
broadening at laser intensities well below the saturation intensity, and
redistribution of intensities of hyperfine spectral components is observed,
which in some cases is contradicting with intuitive expectations. Theoretical
analysis of the dynamics of optical pumping shows that spectral line broadening
depends sensitively on branching coefficient of the laser-driven transition.
Analytical expressions for branching ratio dependent critical Rabi frequency
and critical laser intensity are derived, which give the threshold for onset of
noticeable line broadening by optical pumping. Transitions with larger and
smaller branching coefficients are relatively less affected. The theoretical
excitation spectra were calculated numerically by solving density matrix
equations of motion using the split propagation technique, and they well
reproduce the observed effects of line broadening and peak intensity
variations. The calculations also show that presence of dark (i.e., not laser-
coupled) Zeeeman sublevels in the lower state results in effective branching
coefficients which vary with laser intensity and differ from those implied by
the sum rules, and this can lead to peculiar changes in peak ratios of
hyperfine components of the spectra.Comment: 12 pages, 10 figure
The severity and dynamics of changes in the serum concentration of biochemical markers of muscle tissue damage in an experienced ultramarathon runner after overcoming a distance of 165 km against the background of continuing physical activity
Purpose: to determine the severity and dynamics of changes in the concentration of biochemical markers of muscle tissue damage in the blood serum of an experienced ultramarathon runner after overcoming a distance of 165 kilometers.Materials and methods: measurement of serum concentrations of markers of muscle tissue damage (aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), creatine kinase MB (CK-MB), myoglobin) in serum before and 16 and 144 hours after ultramarathon in an experienced runner (age 36, height 186 cm, weight 76 kg, body mass index 21.96).Results: 16 hours after the end of the race, extremely high levels of AST, ALT, CK, CK-MB and myoglobin were observed, the combination of which indicates severe rhabdomyolysis. After 144 hours, a decrease in the level of all markers of muscle tissue damage, including myoglobin, was noted, however, they continued to remain significantly higher than the reference values. At the same time, the athlete did not have any significant pathological symptoms, and he continued to train in the recovery mode.Conclusion: ultramarathon races lead to significant muscle damage, which can lead to rhabdomyolysis. Its severity may not correlate with any significant clinical manifestations
The assessment of the structure of anti-doping rules violation and the evaluation of anti-doping measures efficiency in Russian athletics during 2000–2020
The assessment of the structure and trends of doping perpetrations among athletes with a proven high prevalence of doping use might be of great practical interest. Non-compliance with the zero-tolerance policy towards anti-doping rules violators among sports communities with a high prevalence of doping offenses is the main cause of the ineffective fight against doping.Objective: to analyze the structure of anti-doping rule violations and evaluate the effectiveness of measures to counter the spread of doping in Russian athletics in 2000–2020.Materials and methods: to form an objective picture, a database was collected on all anti-doping rule violators in Russian athletics from 2000 to June 01, 2020 from open sources. Retrospective analysis of the protocols of all official competitions held in Russia since 2000 and included in the RUSAF Unified Schedule was performed.Results: 381 cases of anti-doping rule violation committed during 2000–2020 period by 355 athletes were registered. 25 athletes committed 2 doping offenses and 1 athlete 3 ones. Women perpetrated more offenses than men.Conclusions: our study objectified the doping issue in Russian athletics and evaluated the effectiveness of anti-doping measures. The study indicates the need to stop ignoring zero-tolerance policy principles towards doping offenders among the athletic community and creates an incentive to develop functional mechanisms to combat doping
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