1,156 research outputs found
Coloured coannihilations: Dark matter phenomenology meets non-relativistic EFTs
We investigate the phenomenology of a simplified model with a Majorana
fermion as dark matter candidate which interacts with Standard Model quarks via
a colour-charged coannihilation partner. Recently it has been realized that
non-perturbative dynamics, including the Sommerfeld effect, bound state
formation/dissociation and thermal corrections, play an important role in
coannihilations with coloured mediators. This calls for a careful analysis of
thermal freeze-out and a new look at the experimental signatures expected for a
thermal relic. We employ a state of the art calculation of the relic density
which makes use of a non-relativistic effective theory framework and calculate
the effective annihilation rates by solving a plasma-modified Schrodinger
equation. We determine the cosmologically preferred parameter space and
confront it with current experimental limits and future prospects for dark
matter detection.Comment: Published version, references and section on indirect detection adde
Re-derived overclosure bound for the inert doublet model
We apply a formalism accounting for thermal effects (such as modified
Sommerfeld effect; Salpeter correction; decohering scatterings; dissociation of
bound states), to one of the simplest WIMP-like dark matter models, associated
with an "inert" Higgs doublet. A broad temperature range T ~ M/20...M/10^4 is
considered, stressing the importance and less-understood nature of late
annihilation stages. Even though only weak interactions play a role, we find
that resummed real and virtual corrections increase the tree-level overclosure
bound by 1...18%, depending on quartic couplings and mass splittings.Comment: 29 pages. v2: clarifications added, published versio
Perturbative unitarity bounds for effective composite models
In this paper we present the partial wave unitarity bound in the parameter
space of dimension-5 and dimension-6 effective operators that arise in a
compositeness scenario. These are routinely used in experimental searches at
the LHC to constraint contact and gauge interactions between ordinary Standard
Model fermions and excited (composite) states of mass . After deducing the
unitarity bound for the production process of a composite neutrino, we
implement such bound and compare it with the recent experimental exclusion
curves for Run 2, the High-Luminosity and High-Energy configurations of the
LHC. Our results also applies to the searches where a generic single excited
state is produced via contact interactions. We find that the unitarity bound,
so far overlooked, is quite complelling and significant portions of the
parameter space () become excluded in addition to the standard
request .Comment: This version of the paper merges the previous version published in
Phys. Lett. B 795 (2019) 644-649
(https://doi.org/10.1016/j.physletb.2019.06.042) with the subsequent Erratum
currently in press in Physics Letters B
(https://doi.org/10.1016/j.physletb.2019.134990
Thermal dark matter co-annihilating with a strongly interacting scalar
Recently many investigations have considered Majorana dark matter
co-annihilating with bound states formed by a strongly interacting scalar
field. However only the gluon radiation contribution to bound state formation
and dissociation, which at high temperatures is subleading to soft 2->2
scatterings, has been included. Making use of a non-relativistic effective
theory framework and solving a plasma-modified Schrodinger equation, we address
the effect of soft 2->2 scatterings as well as the thermal dissociation of
bound states. We argue that the mass splitting between the Majorana and scalar
field has in general both a lower and an upper bound, and that the dark matter
mass scale can be pushed at least up to 5...6 TeV.Comment: 19 pages. v2: clarifications added, published versio
On the equivalence of different approaches for generating multisoliton solutions of the KPII equation
The unexpectedly rich structure of the multisoliton solutions of the KPII
equation has been explored by using different approaches, running from dressing
method to twisting transformations and to the tau-function formulation. All
these approaches proved to be useful in order to display different properties
of these solutions and their related Jost solutions. The aim of this paper is
to establish the explicit formulae relating all these approaches. In addition
some hidden invariance properties of these multisoliton solutions are
discussed
Soliton solutions of the Kadomtsev-Petviashvili II equation
We study a general class of line-soliton solutions of the
Kadomtsev-Petviashvili II (KPII) equation by investigating the Wronskian form
of its tau-function. We show that, in addition to previously known line-soliton
solutions, this class also contains a large variety of new multi-soliton
solutions, many of which exhibit nontrivial spatial interaction patterns. We
also show that, in general, such solutions consist of unequal numbers of
incoming and outgoing line solitons. From the asymptotic analysis of the
tau-function, we explicitly characterize the incoming and outgoing
line-solitons of this class of solutions. We illustrate these results by
discussing several examples.Comment: 28 pages, 4 figure
Hierarchy problem and fine-tuning in a decoupling approach to multiscale effective potentials
In many realizations of beyond the Standard Model theories, new massive
particles are introduced, leading to a multi-scale system with widely separated
energy scales. In this setting the effective potential, which takes into
account quantum corrections for the scalar sector, has to be supplemented with
a prescription to handle the hierarchy in mass scales. In this paper, we focus
on the so-called decoupling method, which freezes the effects of heavy
particles on the RG running of the light degrees of freedom at low energies.
For a two-scalar theory, we disentangle the effects of the high-energy degrees
of freedom on the shape of the potential and on the fine-tuning of the model
parameters. We find that, while the decoupling method leads to an acceptable
and convergent effective potential, the method does not solve the fine-tuning
problem that is inherent to the hierarchy problem of multi-scale theories. We
also consider two alternative implementations of the decoupling, which give
different results for the shape of the potential, but still lead to similar
conclusions on the amount of fine-tuning in the model.Comment: 19 pages, 7 figure
Non-relativistic susceptibility and a dark matter application
When thermal rate equations are derived for the evolution of slow variables,
it is often practical to parametrize the right-hand side with chemical
potentials. To close the system, the chemical potentials are subsequently
re-expressed in terms of the slow variables, which involves the consideration
of a "susceptibility". Here we study a non-relativistic situation in which
chemical potentials are large compared with the temperature, as is relevant for
late-time pair annihilations in dark matter freeze-out. An order-of-magnitude
estimate and a lattice simulation are presented for a susceptibility dominated
by bound states of stop-like mediators. After this "calibration", the formalism
is applied to a model with Majorana singlet dark matter, confirming that masses
up to the multi-TeV domain are viable in the presence of sufficient (though not
beyond a limit) mass degeneracy in the dark sector.Comment: 14 pages. v2: clarifications adde
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