4,032 research outputs found
Prospects of detecting massive isosinglet neutrino at LHC in the CMS detector
A possibility to search for a heavy isosinglet (sterile) neutrino using its
decay mode in the - channel production in the CMS experiment is studied. The only
assumption about the heavy neutrino is its nonzero mixing with or
. The corresponding CMS discovery potential expressed in terms of
the heavy neutrino mass and the mixing parameter between the heavy and light
neutrino is determined. It is shown that the heavy neutrino with a mass up to
800 could be detected in CMS. We also investigate the production of the
heavy neutrino mixed with and/or in the model through the reaction with the same heavy neutrino decay channel as
above. We find that for it is possible to discover the heavy
neutrino with a mass up to .Comment: 14 pages, 13 figure
The exact tree-level calculation of the dark photon production in high-energy electron scattering at the CERN SPS
Dark photon () that couples to the standard model fermions via the
kinetic mixing with photons and serves as a mediator of dark matter production
could be observed in the high-energy electron scattering off nuclei followed by the decay. We have
performed the exact, tree-level calculations of the production cross
sections and implemented them in the program for the full simulation of such
events in the experiment NA64 at the CERN SPS. Using simulations results, we
study the missing energy signature for the bremsstrahlung
invisible decay that permits the determination of the mixing
strength in a wide, from sub-MeV to sub-GeV, mass range. We refine and
expand our earlier studies of this signature for discovering by including
corrections to the previously used calculations based on the improved
Weizsaker-Williams approximation, which turn out to be significant. We compare
our cross sections values with the results from other calculations and find a
good agreement between them. The possibility of future measurements with
high-energy electron beams and the sensitivity to are briefly discussed.Comment: 11 pages, 6 figures, revised version, improved cross-section
integrator is used, comparison with bremsstrahlung spectrum is added, final
conclusions remain unchange
Missing energy signature from invisible decays of dark photons at the CERN SPS
The dark photon () production through the mixing with the bremsstrahlung
photon from the electron scattering off nuclei can be accompanied by the
dominant invisible decay into dark-sector particles. In this work we
discuss the missing energy signature of this process in the experiment NA64
aiming at the search for decays with a high-energy electron
beam at the CERN SPS. We show the distinctive distributions of variables that
can be used to distinguish the signal from background. The
results of the detailed simulation of the detector response for the events with
and without emission are presented. The efficiency of the signal event
selection is estimated. It is used to evaluate the sensitivity of the
experiment and show that it allows to probe the still unexplored area of the
mixing strength and masses up to
GeV. The results obtained are compared with the results
from other calculations. In the case of the signal observation, a possibility
of extraction of the parameters and by using the missing
energy spectrum shape is discussed. We consider as an example the with the
mass 16.7 MeV and mixing , which can explain an
excess of events recently observed in nuclear transitions of an excited state
of Be. We show that if such exists its invisible decay can be observed
in NA64 within a month of running, while data accumulated during a few months
would allow also to determine the and parameters.Comment: 12 pages, 15 figures. Revised versio
Split Supersymmetry at the Logarithmic Test of Future Colliders
We consider a large number of pair production processes at future colliders
(LHC, ILC) for values of the c.m. energy in the TeV range, where a logarithmic
expansion of Sudakov kind would provide a reliable description of Split
supersymmetric electroweak effects. We calculate all the leading and next to
leading terms of the expansions, that would differ drastically in the
considered domain from those of an extreme "light" scenario. We imagine then
two possible competitive future situations, at LHC and at ILC, where the
determination of the energy dependence of the cross sections of certain
processes could reveal a "signal" of the correct supersymmetric scheme.Comment: 32 pages, 10 figure
Lepton flavor violation at linear collider experiments in supersymmetric grand unified theories
Lepton flavor violation at linear collider experiments is discussed. We show
that detectable lepton flavor violation could occur through scalar lepton pair
production and decay in the supersymmetric SU(5) grand unified theory in spite
of the stringent present experimental constraints by rare process searches.
Possible cross sections about 40fb for an e+e- collider and 280fb for an e-e-
collider are illustrated.Comment: 12 pages, including 3 figures, REVTeX, eps
LHC signatures for Z` models with continuously distributed mass
We discuss phenomenological consequences of renormalizable Z` models with
continuously distributed mass. We point out that one of possible LHC signatures
for such nodel is the existence of broad resonance in Drell-Yan reaction .Comment: 7 page
Calculating loops without loop calculations: NLO computation of pentaquark correlators
We compute next-to-leading order (NLO) perturbative QCD corrections to the
correlators of interpolating pentaquark currents. We employ modular techniques
in configuration space which saves us from the onus of having to do loop
calculations. The modular technique is explained in some detail. We present
explicit NLO results for several interpolating pentaquark currents that have
been written down in the literature. Our modular approach is easily adapted to
the case of NLO corrections to multiquark correlators with an arbitrary number
of quarks/antiquarks.Comment: 23 pages, 1 figure, published version. arXiv admin note: text overlap
with arXiv:hep-lat/031001
The quantum inequalities do not forbid spacetime shortcuts
A class of spacetimes (comprising the Alcubierre bubble, Krasnikov tube, and
a certain type of wormholes) is considered that admits `superluminal travel' in
a strictly defined sense. Such spacetimes (they are called `shortcuts' in this
paper) were suspected to be impossible because calculations based on `quantum
inequalities' suggest that their existence would involve Planck-scale energy
densities and hence unphysically large values of the `total amount of negative
energy' E_tot. I argue that the spacetimes of this type may not be unphysical
at all. By explicit examples I prove that: 1) the relevant quantum inequality
does not (always) imply large energy densities; 2) large densities may not lead
to large values of E_tot; 3) large E_tot, being physically meaningless in some
relevant situations, does not necessarily exclude shortcuts.Comment: Minor corrections and addition
Can an odd number of fermions be created due to chiral anomaly?
We describe a possibility of creation of an odd number of fractionally
charged fermions in 1+1 dimensional Abelian Higgs model. We point out that for
1+1 dimensions this process does not violate any symmetries of the theory, nor
makes it mathematically inconsistent. We construct the proper definition of the
fermionic determinant in this model and underline its non-trivial features that
are of importance for realistic 3+1 dimensional models with fermion number
violation.Comment: 12 pages revtex, 2 figure
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