115 research outputs found
Neutralino and gravitino dark matter with low reheating temperature
We examine a scenario in which the reheating temperature after
inflation is so low that it is comparable to, or lower than, the freeze out
temperature of ordinary WIMPs. In this case the dark matter relic abundance is
reduced, thus relaxing the impact of the usually strong constraint coming from
the requirement that the universe does not overclose. We first re-examine the
dynamics of freezeout during reheating. Next we apply a Bayesian approach to
study the parameter space of the MSSM with ten free parameters, the CMSSM and
the singlino-dominated regions of the NMSSM. In each case we find dramatic
departures from the usually considered regime of high , with important
implications for direct detection dark matter searches. In the MSSM we examine
WIMP mass range up to ~5 TeV, and find regions of bino dark matter over the
whole mass range, and of higgsino dark matter with mass over a similar range
but starting from the ~1 TeV value of the standard high scenario. We show
that the prospects for bino detection strongly depend on , while the
higgsino is for the most part detectable by future one-tonne detectors. The
wino, which is excluded in the standard scenario, becomes allowed again if its
mass is roughly above 3.5 TeV, and can be detectable. In the CMSSM, the bino
and higgsino mass ranges become more constrained although detection prospects
remain similar. In the Next-to-MSSM at low enough wide ranges of
singlino-dominated parameter space of the model become cosmologically allowed.
We also study the contribution to the DM relic density from direct and cascade
decays of the inflaton. Finally, we consider the case of a gravitino as dark
matter. We find strong bounds from overclosure and Big Bang Nucleosynthesis,
and derive lower limits on which depend on the gravitino mass and on the
nature of the lightest ordinary superpartner.Comment: section and references adde
Axino dark matter with low reheating temperature
We examine axino dark matter in the regime of a low reheating temperature T_R
after inflation and taking into account that reheating is a non-instantaneous
process. This can have a significant effect on the dark matter abundance,
mainly due to entropy production in inflaton decays. We study both thermal and
non-thermal production of axinos in the context of the MSSM with ten free
parameters. We identify the ranges of the axino mass and the reheating
temperature allowed by the LHC and other particle physics data in different
models of axino interactions. We confront these limits with cosmological
constraints coming the observed dark matter density, large structures formation
and big bang nucleosynthesis. We find a number of differences in the
phenomenologically acceptable values of the axino mass and the reheating
temperature relative to previous studies. In particular, an upper bound on the
axino mass becomes dependent on T_R, reaching a maximum value at T_R~10^2 GeV.
If the lightest ordinary supersymmetric particle is a wino or a higgsino, we
obtain lower a limit of approximately 10 GeV for the reheating temperature. We
demonstrate also that entropy production during reheating affects the maximum
allowed axino mass and lowest values of the reheating temperature.Comment: v2: improved discussion of warm dark matter bounds, results for stau
LOSP adde
Gravitino dark matter with constraints from Higgs boson mass and sneutrino decays
We investigate gravitino dark matter produced thermally at high temperatures
and in decays of a long-lived sneutrino. We consider the Non-Universal Higgs
Model and a generalized gauge mediation model, and in each case identify
sneutrino LOSP regions of the parameter space consistent with the mass of the
Higgs-like boson observed at the LHC. We apply relevant collider and
cosmological bounds, including constraints from Big Bang Nucleosynthesis and
from warm dark matter on large scale structures. Generally, we find allowed
values of the reheating temperature TR below 10^9 GeV, i.e. somewhat smaller
than the values needed for thermal leptogenesis, even with a conservative lower
bound of 122 GeV on the Higgs mass. Requiring mass values closer to 126 GeV
implies TR below 10^7 GeV and the gravitino mass less than 10 GeV.Comment: 19 pages, 19 figures, version published in JHE
FASER: ForwArd Search ExpeRiment at the LHC
New physics has traditionally been expected in the high- region at
high-energy collider experiments. If new particles are light and
weakly-coupled, however, this focus may be completely misguided: light
particles are typically highly concentrated within a few mrad of the beam line,
allowing sensitive searches with small detectors, and even extremely
weakly-coupled particles may be produced in large numbers there. We propose a
new experiment, ForwArd Search ExpeRiment, or FASER, which would be placed
downstream of the ATLAS or CMS interaction point (IP) in the very forward
region and operated concurrently there. Two representative on-axis locations
are studied: a far location, from the IP and just off the beam
tunnel, and a near location, just from the IP and right behind
the TAN neutral particle absorber. For each location, we examine leading
neutrino- and beam-induced backgrounds. As a concrete example of light,
weakly-coupled particles, we consider dark photons produced through light meson
decay and proton bremsstrahlung. We find that even a relatively small and
inexpensive cylindrical detector, with a radius of and
length of , depending on the location, can discover dark photons
in a large and unprobed region of parameter space with dark photon mass and kinetic mixing parameter . FASER will clearly also be sensitive to many other forms of
new physics. We conclude with a discussion of topics for further study that
will be essential for understanding FASER's feasibility, optimizing its design,
and realizing its discovery potential.Comment: 35 Pages, 12 figures. Version 2, references added, minor change
Low fine tuning in the MSSM with higgsino dark matter and unification constraints
We examine the issue of fine tuning in the MSSM with GUT-scale boundary
conditions. We identify specific unification patterns and mass relations that
can lead to a significant lowering of the fine tuning due to gauginos, scalars,
and the \mu\ parameter, relative to the simplest unification conditions. We
focus on a phenomenologically interesting region that is favored by the Higgs
mass and the relic density where the dark matter is a nearly pure higgsino with
mass given by \mu~1 TeV while the scalars and gauginos have masses in the
multi-TeV regime. There, we find that the fine tuning can be reduced to the
level of a few percent. Despite the gluino mass in the ballpark of 2 TeV,
resulting mass spectra will be hard to explore at the LHC, but good prospects
for detection come from dark matter direct detection experiments. Finally, we
demonstrate with a specific example how the conditions and mass relations
giving low fine tuning can originate in the context of supergravity and Grand
Unified Theories.Comment: 35 pages, 8 figures. Figure 2 added, minor changes. Version published
in JHE
Looking forward to test the KOTO anomaly with FASER
The search for light and long-lived particles at the LHC will be intensified
in the upcoming years with a prominent role of the new FASER experiment. In
this study, we discuss how FASER could independently probe such scenarios
relevant for new physics searches at kaon factories. We put an emphasis on the
proposed explanations for the recently observed three anomalous events in the
KOTO experiment. The baseline of FASER precisely corresponds to the proposed
lifetime solution to the anomaly that avoids the NA62 bounds on charged kaons.
As a result, the experiment can start constraining relevant models within the
first few weeks of its operation. In some cases, it can confirm a possible
discovery with up to 10000 spectacular high-energy events in FASER during LHC
Run 3. Further complementarities between FASER and kaon factories, which employ
FASER capability to study di-photon signatures, are illustrated for the model
with axion-like particles dominantly coupled to gauge bosons.Comment: Version published in PR
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