390 research outputs found
Collider signatures of sterile neutrinos in models with a gauge-singlet Higgs
Sterile neutrinos have been invoked to explain the observed neutrino masses,
but they can also have significant implications for cosmology and accelerator
experiments. We explore the collider signatures of a simple extension of the
Standard Model, where sterile neutrinos acquire their mass after electroweak
symmetry breaking, via their coupling to a real singlet Higgs. In this model,
heavy sterile neutrinos can be produced in accelerators from decays of the
Higgs bosons. Their own decay can yield distinct signals, suggesting both the
presence of an extended Higgs sector and the coupling of the singlet fermions
to the latter. In the same scenario, a relic matter abundance arises from the
decay of the singlet Higgs into weakly coupled keV sterile neutrinos. The
coupling of the Higgs doublet to particles outside the Standard Model relaxes
the current experimental bounds on its mass.Comment: v2: JHEP accepted version, 19 pages, 9 figure
Heavy sterile neutrinos and supernova explosions
We consider sterile neutrinos with rest masses ~0.2 GeV. Such sterile
neutrinos could augment core collapse supernova shock energies by enhancing
energy transport from the core to the vicinity of the shock front. The decay of
these neutrinos could produce a flux of very energetic active neutrinos,
detectable by future neutrino observations from a galactic supernova. The
relevant range of sterile neutrino masses and mixing angles can be probed in
future laboratory experiments.Comment: 5 page
Dark Matter's secret liaisons: Phenomenology of a dark U(1) sector with bound states
Dark matter (DM) charged under a dark U(1) force appears in many extensions of the Standard Model, and has been invoked to explain anomalies in cosmic-ray data, as well as a self-interacting DM candidate. In this paper, we perform a comprehensive phenomenological analysis of such a model, assuming that the DM abundance arises from the thermal freeze-out of the dark interactions. We include, for the first time, bound-state effects both in the DM production and in the indirect detection signals, and quantify their importance for Fermi, Ams-02, and CMB experiments. We find that DM in the mass range 1 GeV to 100TeV, annihilating into dark photons of MeV to GeV mass, is in conict with observations. Instead, DM annihilation into heavier dark photons is viable. We point out that the late decays of multi-GeV dark photons can produce significant entropy and thus dilute the DM density. This can lower considerably the dark coupling needed to obtain the DM abundance, and in turn relax the existing constraints
Dark-matter sterile neutrinos in models with a gauge singlet in the Higgs sector
Sterile neutrino with mass of several keV can be the cosmological dark
matter, can explain the observed velocities of pulsars, and can play an
important role in the formation of the first stars. We describe the production
of sterile neutrinos in a model with an extended Higgs sector, in which the
Majorana mass term is generated by the vacuum expectation value of a
gauge-singlet Higgs boson. In this model the relic abundance of sterile
neutrinos does not necessarily depend on their mixing angles, the
free-streaming length can be much smaller than in the case of warm dark matter
produced by neutrino oscillations, and, therefore, some of the previously
quoted bounds do not apply. The presence of the gauge singlet in the Higgs
sector has important implications for the electroweak phase transition,
baryogenesis, and the upcoming experiments at the Large Hadron Collider and a
Linear Collider.Comment: 12 pages, 7 figure
Final-state interactions in the response of nuclear matter
Final-state interactions in the response of a many-body system to an external
probe delivering large momentum are normally described using the eikonal
approximation, for the trajectory of the struck particle, and the frozen
approximation, for the positions of the spectators. We propose a generalization
of this scheme, in which the initial momentum of the struck particle is
explicitly taken into account. Numerical calculations of the nuclear matter
response at 1 2 GeV/c show that the inclusion of this momentum
dependence leads to a sizable effect in the low energy tail. Possible
implications for the analysis of existing electron-nucleus scattering data are
discussed.Comment: 21 pages, 4 figure
Co-expression of KLK6 and KLK10 as prognostic factors for survival in pancreatic ductal adenocarcinoma
Kallikreins play an important role in tumour microenvironment and as cancer biomarkers in different cancer entities. Previous studies suggested an upregulation of KLK10 and KLK6 in pancreatic ductal adenocarcinoma (PDAC). Therefore, we evaluated the clinicopathological role of these kallikreins and their value as biomarkers in PDAC
The Effect of the Short-Range Correlations on the Generalized Momentum Distribution in Finite Nuclei
The effect of dynamical short-range correlations on the generalized momentum
distribution in the case of , -closed shell
nuclei is investigated by introducing Jastrow-type correlations in the
harmonic-oscillator model. First, a low order approximation is considered and
applied to the nucleus He. Compact analytical expressions are derived and
numerical results are presented and the effect of center-of-mass corrections is
estimated. Next, an approximation is proposed for of
heavier nuclei, that uses the above correlated of He.
Results are presented for the nucleus O. It is found that the effect of
short-range correlations is significant for rather large values of the momenta
and/or and should be included, along with center of mass corrections
for light nuclei, in a reliable evaluation of in the whole
domain of and .Comment: 29 pages, 8 figures. Further results, figures and discussion for the
CM corrections are added. Accepted by Journal of Physics
Affleck-Dine dynamics and the dark sector of pangenesis
Pangenesis is the mechanism for jointly producing the visible and dark matter
asymmetries via Affleck-Dine dynamics in a baryon-symmetric universe. The
baryon-symmetric feature means that the dark asymmetry cancels the visible
baryon asymmetry and thus enforces a tight relationship between the visible and
dark matter number densities. The purpose of this paper is to analyse the
general dynamics of this scenario in more detail and to construct specific
models. After reviewing the simple symmetry structure that underpins all
baryon-symmetric models, we turn to a detailed analysis of the required
Affleck-Dine dynamics. Both gravity-mediated and gauge-mediated supersymmetry
breaking are considered, with the messenger scale left arbitrary in the latter,
and the viable regions of parameter space are determined. In the gauge-mediated
case where gravitinos are light and stable, the regime where they constitute a
small fraction of the dark matter density is identified. We discuss the
formation of Q-balls, and delineate various regimes in the parameter space of
the Affleck-Dine potential with respect to their stability or lifetime and
their decay modes. We outline the regions in which Q-ball formation and decay
is consistent with successful pangenesis. Examples of viable dark sectors are
presented, and constraints are derived from big bang nucleosynthesis, large
scale structure formation and the Bullet cluster. Collider signatures and
implications for direct dark matter detection experiments are briefly
discussed. The following would constitute evidence for pangenesis:
supersymmetry, GeV-scale dark matter mass(es) and a Z' boson with a significant
invisible width into the dark sector.Comment: 51 pages, 7 figures; v2: minor modifications, comments and references
added; v3: minor changes, matches published versio
Role of Sterile Neutrino Warm Dark Matter in Rhenium and Tritium Beta Decays
Sterile neutrinos with mass in the range of one to a few keV are important as
extensions of the Standard Model of particle physics and are serious dark
matter (DM) candidates. This DM mass scale (warm DM) is in agreement with both
cosmological and galactic observations. We study the role of a keV sterile
neutrino through its mixing with a light active neutrino in Rhenium 187 and
Tritium beta decays. We pinpoint the energy spectrum of the beta particle, 0 <
T_e < (Q_{beta} - m_s), as the region where a sterile neutrino could be
detected and where its mass m_s could be measured. This energy region is at
least 1 keV away rom the region suitable to measure the mass of the light
active neutrino, located near the endpoint Q_{beta} . The emission of a keV
sterile neutrino in a beta decay could show up as a small kink in the spectrum
of the emitted beta particle. With this in view, we perform a careful
calculation of the Rhenium and Tritium beta spectra and estimate the size of
this perturbation by means of the dimensionless ratio R of the sterile neutrino
to the active neutrino contributions. We comment on the possibility of
searching for sterile neutrino signatures in two experiments which are
currently running at present, MARE and KATRIN, focused on the Rhenium 187 and
Tritium beta decays respectively.Comment: 16 pages, 10 figures. Version to appear in Nucl. Phys. B. Results and
conclusions unchange
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