181 research outputs found
Modification of Coulomb law and energy levels of hydrogen atom in superstrong magnetic field
The screening of a Coulomb potential by superstrong magnetic field is
studied. Its influence on the spectrum of a hydrogen atom is determined.Comment: Lectures at 39 ITEP Winter School and 11 Baikal Summer School; 12
pages, 5 figure
Suppression of decay channels in the Georgi-Machacek model
The decay mode is usually considered as one of the most promising
ways to discover new heavy neutral scalar . We show that in the
Georgi-Machacek model it is possible to get large enhancement of double SM-like
Higgs boson production due to decays while and decay channels
could be highly suppressed.Comment: 5 page
Quark Lagrangian diagonalization versus non-diagonal kinetic terms
Loop corrections induce a dependence on the momentum squared of the
coefficients of the Standard Model Lagrangian, making highly non-trivial (or
even impossible) the diagonalization of its quadratic part. Fortunately, the
introduction of appropriate counterterms solves this puzzle.Comment: 2 pages, 1 figur
New Physics at 1 TeV?
If decays of a heavy particle S are responsible for the diphoton excess with
invariant mass 750 GeV observed at the 13 TeV LHC run, it can be easily
accomodated in the Standard Model. Two scenarios are considered: production in
gluon fusion through a loop of heavy isosinglet quark(s) and production in
photon fusion through a loop of heavy isosinglet leptons. In the second case
many heavy leptons are needed or/and they should have large electric charges in
order to reproduce experimental data on .Comment: 7 pages, 4 figures, 1 tabl
The Thermal Abundance of Semi-Relativistic Relics
Approximate analytical solutions of the Boltzmann equation for particles that
are either extremely relativistic or non-relativistic when they decouple from
the thermal bath are well established. However, no analytical formula for the
relic density of particles that are semi-relativistic at decoupling is yet
known. We propose a new ansatz for the thermal average of the annihilation
cross sections for such particles, and find a semi-analytical treatment for
calculating their relic densities. As examples, we consider Majorana- and
Dirac-type neutrinos. We show that such semi-relativistic relics cannot be good
cold Dark Matter candidates. However, late decays of meta-stable
semi-relativistic relics might have released a large amount of entropy, thereby
diluting the density of other, unwanted relics.Comment: 22 pages, 5 figures. Comments and references adde
Extending the Higgs sector: an extra singlet
An extension of the Standard Model with an additional Higgs singlet is
analyzed. Bounds on singlet admixture in 125 GeV h boson from electroweak
radiative corrections and data on h production and decays are obtained.
Possibility of double h production enhancement at 14 TeV LHC due to heavy higgs
contribution is considered.Comment: 18 pages, 7 figures. v2: one equation added; references received
after the publication of v1 are adde
Evading the astrophysical limits on light pseudoscalars
We study the possibility of evading astrophysical bounds on light
pseudoscalars. We argue that the solar bounds can be evaded if we have a
sufficiently strong self coupling of the pseudoscalars. The required couplings
do not conflict with any known experimental bounds. We show that it is possible
to find a coupling range such that the results of the recent PVLAS experiment
are not in conflict with any astrophysical bounds.Comment: 10 pages, 5 figures, minor change
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