324 research outputs found
Inclusive Displaced Vertex Searches for Heavy Neutral Leptons at the LHC
The inclusion of heavy neutral leptons to the Standard Model particle content
could provide solutions to many open questions in particle physics and
cosmology. The modification of the charged and neutral currents from
active-sterile mixing of neutral leptons can provide novel signatures in
Standard Model processes. We revisit the displaced vertex signature that could
occur in collisions at the LHC via the decay of heavy neutral leptons with
masses of a few GeV emphasizing the implications of flavor, kinematics,
inclusive production and number of these extra neutral fermions. We study in
particular the implication on the parameter space sensitivity when all mixings
to active flavors are taken into account. We also discuss alternative cases
where the new particles are produced in a boosted regime.Comment: 24 pages, 10 figures. Extended analysis. Published versio
Neutrino Non-standard Interactions with arbitrary couplings to u and d quarks
We introduce a model for Non-Standard neutral current Interaction (NSI)
between neutrinos and the matter fields, with an arbitrary coupling to the up
and down quarks. The model is based on a new gauge symmetry with a light
gauge boson that mixes with the photon. We show that the couplings to the
and quarks can have a ratio such that the contribution from NSI to the
Coherent Elastic Neutrino-Nucleus Scattering (CENS) amplitude vanishes,
relaxing the bound on the NSI from the CENS experiments. Additionally, the
deviation of the measured value of the anomalous magnetic dipole moment of the
muon from the standard-model prediction can be fitted. The most limiting
constraints on our model come from the search for the decay of the new gauge
boson to and invisible particles, carried out by NA48/2 and NA64,
respectively. We show that these bounds can be relaxed by opening up the decay
of the new gauge boson to new light scalars that eventually decay into the pairs. We show that there are ranges that can lead to both a solution to
the anomaly and values of large enough to be probed by future solar neutrino experiments.Comment: 13+4 pages, 4 figures. V2 matches the published version in PR
WIMPs during Reheating
Weakly Interacting Massive Particles (WIMPs) are among the best-motivated
dark matter candidates. In the standard scenario where the freeze-out happens
well after the end of inflationary reheating, they are in tension with the
severe experimental constraints. Here, we investigate the thermal freeze-out of
WIMPs occurring {\it during} reheating, while the inflaton coherently
oscillates in a generic potential . Depending on the value of
and the spin of the inflaton decaying products, the evolution of the
radiation and inflaton energy densities can show distinct features, therefore,
having a considerable impact on the freeze-out behavior of WIMPs. As a result
of the injection of entropy during reheating, the parameter space compatible
with the observed DM relic abundance is enlarged. In particular, the WIMP
thermally averaged annihilation cross-section can be several magnitudes lower
than that in the standard case. Finally, we discuss the current bounds from
dark matter indirect detection experiments, and explore future challenges and
opportunities.Comment: 19 pages, 5 figure
- …