1,038 research outputs found
Initial State Radiation in Majorana Dark Matter Annihilations
The cross section for a Majorana Dark Matter particle annihilating into light
fermions is helicity suppressed. We show that, if the Dark Matter is the
neutral Majorana component of a multiplet which is charged under the
electroweak interactions of the Standard Model, the emission of gauge bosons
from the initial state lifts the suppression and allows an s-wave annihilation.
The resulting energy spectra of stable Standard Model particles are importantly
affected. This has an impact on indirect searches for Dark Matter.Comment: 9 pages, 3 figure
Elemental analysis of particulate matter by X-ray fluorescence methods: A green approach to air quality monitoring
This review explores X-ray fluorescence (XRF) spectrometry for elemental analysis of particulate matter (PM) for
air quality monitoring. The introduction presents PM classification based on size and composition, covering
various elemental analysis methods while highlighting the increasing interest in XRF due to its non-destructive,
rapid, and green features. The fundamental concepts of XRF and the experimental configurations commonly used
are discussed, focusing on Energy Dispersive X-Ray Fluorescence (EDXRF) and Total Reflection X-Ray Fluorescence
(TXRF). PM sampling devices and substrate are described, with a specific emphasis on filtering membranes
for EDXRF and reflecting substrates for TXRF. Sample preparation strategies and procedures are presented.
Qualitative and quantitative analysis is described, with a particular focus on the calibration approaches implemented for PM. Finally, the challenges faced by XRF in becoming a recognized reliable analytical technique for PM analysis, comparable to other standardized techniques for PM filters analysis, while capitalizing on its green advantages
Performance evaluation of different centrifugal pendulum morphologies through multibody dynamics simulation
A dynamic model of a Cardan joint to evaluate the effect of elasticity and manufacturing errors
High energy gamma-ray constraints on decaying Dark Matter
New bounds on decaying Dark Matter are derived from the gamma-ray
measurements of (i) the isotropic residual (extragalactic) background by Fermi
and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are
among the most stringent constraints currently available, for a large range of
dark matter masses and a variety of decay modes, excluding half-lives up to
about 10^26 to few 10^27 seconds. In particular, they rule out the
interpretation in terms of decaying dark matter of the e+/- spectral features
in PAMELA, Fermi and H.E.S.S., unless very conservative choices are adopted. We
also discuss future prospects for CTA bounds from Fornax which, contrary to the
present H.E.S.S. constraints of (ii), may allow for an interesting improvement
and may become better than those from the current or future extragalactic Fermi
data.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), ID622, Rio de Janeiro (Brazil
On the Importance of Electroweak Corrections for Majorana Dark Matter Indirect Detection
Recent analyses have shown that the inclusion of electroweak corrections can
alter significantly the energy spectra of Standard Model particles originated
from dark matter annihilations. We investigate the important situation where
the radiation of electroweak gauge bosons has a substantial influence: a
Majorana dark matter particle annihilating into two light fermions. This
process is in p-wave and hence suppressed by the small value of the relative
velocity of the annihilating particles. The inclusion of electroweak radiation
eludes this suppression and opens up a potentially sizeable s-wave contribution
to the annihilation cross section. We study this effect in detail and explore
its impact on the fluxes of stable particles resulting from the dark matter
annihilations, which are relevant for dark matter indirect searches. We also
discuss the effective field theory approach, pointing out that the opening of
the s-wave is missed at the level of dimension-six operators and only encoded
by higher orders.Comment: 25 pages, 6 figures. Minor corrections to match version published in
JCA
Displaced Higgs production in type III seesaw
We point out that the type III seesaw mechanism introducing fermion triplets
predicts peculiar Higgs boson signatures of displaced vertices with two b jets
and one or two charged particles which can be cleanly identified. In a
supersymmetric theory, the scalar partner of the fermion triplet contains a
neutral dark matter candidate which is almost degenerate with its charged
components. A Higgs boson can be produced together with such a dark matter
triplet in the cascade decay chain of a strongly produced squark or gluino.
When the next lightest supersymmetric particle (NLSP) is bino/wino-like, there
appears a Higgs boson associated with two charged tracks of a charged lepton
and a heavy charged scalar at a displacement larger than about 1 mm. The
corresponding production cross-section is about 0.5 fb for the squark/gluino
mass of 1 TeV. In the case of the stau NLSP, it decays mainly to a Higgs boson
and a heavy charged scalar whose decay length is larger than 0.1 mm for the
stau NLSP mixing with the left-handed stau smaller than 0.3. As this process
can have a large cascade production pb for the squark/gluino mass
TeV, one may be able to probe it at the early stage of the LHC
experiment.Comment: 10 pages, 5 figure
Common gauge origin of discrete symmetries in observable sector and hidden sector
An extra Abelian gauge symmetry is motivated in many new physics models in
both supersymmetric and nonsupersymmetric cases. Such a new gauge symmetry may
interact with both the observable sector and the hidden sector. We
systematically investigate the most general residual discrete symmetries in
both sectors from a common Abelian gauge symmetry. Those discrete symmetries
can ensure the stability of the proton and the dark matter candidate. A hidden
sector dark matter candidate (lightest U-parity particle or LUP) interacts with
the standard model fields through the gauge boson Z', which may selectively
couple to quarks or leptons only. We make a comment on the implications of the
discrete symmetry and the leptonically coupling dark matter candidate, which
has been highlighted recently due to the possibility of the simultaneous
explanation of the DAMA and the PAMELA results. We also show how to construct
the most general U(1) charges for a given discrete symmetry, and discuss the
relation between the U(1) gauge symmetry and R-parity.Comment: Version to appear in JHE
Gamma ray tests of Minimal Dark Matter
We reconsider the model of Minimal Dark Matter (a fermionic, hypercharge-less quintuplet of the EW interactions) and compute its gamma ray signatures. We compare them with a number of gamma ray probes: the galactic halo diffuse measurements, the galactic center line searches and recent dwarf galaxies observations. We find that the original minimal model, whose mass is fixed at 9.4 TeV by the relic abundance requirement, is constrained by the line searches from the Galactic Center: it is ruled out if the Milky Way possesses a cuspy profile such as NFW but it is still allowed if it has a cored one. Observations of dwarf spheroidal galaxies are also relevant (in particular searches for lines), and ongoing astrophysical progresses on these systems have the potential to eventually rule out the model. We also explore a wider mass range, which applies to the case in which the relic abundance requirement is relaxed. Most of our results can be safely extended to the larger class of multi-TeV WIMP DM annihilating into massive gauge bosons
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
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