8,167 research outputs found
Multi-lepton signatures at LHC from sneutrino dark matter
We investigate multi-lepton LHC signals arising from an extension at the
grand unification scale of the standard minimal supersymmetric model (MSSM)
involving right-handed neutrino superfields. In this framework neutrinos have
Dirac masses and the mixed sneutrinos are the lightest supersymmetric particles
and hence the dark matter candidates. We analyze the model parameter space in
which the sneutrino is a good dark matter particle and has a direct detection
cross-section compatible with the LUX bound. Studying the supersymmetric mass
spectrum of this region, we find several signatures relevant for LHC, which are
distinct from the predictions of the MSSM with neutralino dark matter. For
instance two opposite sign and different flavor leptons, three uncorrelated
leptons and long-lived staus are the most representative. Simulating both the
signal and expected background, we find that the multi-lepton signatures and
the long-lived stau are in the reach of the future run of LHC with a luminosity
of 100/fb. We point out that if one of these signatures is detected, it might
be an indication of sneutrino dark matter.Comment: 34 pages, 14 figures and 6 tables; this version matches the published
on
New techniques for chargino-neutralino detection at LHC
The recent LHC discovery of a Higgs-like boson at 126 GeV has important
consequences for SUSY, pushing the spectrum of strong-interacting
supersymmetric particles to high energies, very difficult to probe at the LHC.
This gives extra motivation to study the direct production of electroweak
particles, as charginos and neutralinos, which are presently very poorly
constrained. The aim of this work is to improve the analysis of
chargino-neutralino pair production at LHC, focusing on the kinematics of the
processes. We propose a new method based on the study of the poles of a certain
kinematical variable. This complements other approaches, giving new information
about the spectrum and improving the signal-to-background ratio. We illustrate
the method in particular SUSY models, and show that working with the LHC at
100/fb luminosity one would be able to distinguish the SUSY signal from the
Standard Model background.Comment: accepted for publication in JHE
Dark matter protohalos in MSSM-9 and implications for direct and indirect detection
We study how the kinetic decoupling of dark matter (DM) within a minimal
supersymmetric extension of the standard model, by adopting nine independent
parameters (MSSM-9), could improve our knowledge of the properties of the DM
protohalos. We show that the most probable neutralino mass regions, which
satisfy the relic density and the Higgs mass contraints, are those with the
lightest supersymmetric neutralino mass around 1 TeV and 3 TeV, corresponding
to Higgsino-like and Wino-like neutralino, respectively. The kinetic decoupling
temperature in the MSSM-9 scenario leads to a most probable protohalo mass in a
range of . The part of the
region closer to 2 TeV gives also important contributions from the
neutralino-stau co-annihilation, reducing the effective annihilation rate in
the early Universe. We also study how the size of the smallest DM substructures
correlates to experimental signatures, such as the spin-dependent and
spin-independent scattering cross sections, relevant for direct detection of
DM. Improvements on the spin-independent sensitivity might reduce the most
probable range of the protohalo mass between 10 and
10, while the expected spin-dependent sensitivity
provides weaker constraints. We show how the boost of the luminosity due to DM
annihilation increases, depending on the protohalo mass. In the Higgsino case,
the protohalo mass is lower than the canonical value often used in the
literature (10), while does not
deviate from cm s; there is no
significant enhancement of the luminosity. On the contrary, in the Wino case,
the protohalo mass is even lighter, and is two orders
of magnitude larger; as its consequence, we see a substantial enhancement of
the luminosity.Comment: 26 pages, 8 figure
MSSM Forecast for the LHC
We perform a forecast of the MSSM with universal soft terms (CMSSM) for the
LHC, based on an improved Bayesian analysis. We do not incorporate ad hoc
measures of the fine-tuning to penalize unnatural possibilities: such
penalization arises from the Bayesian analysis itself when the experimental
value of is considered. This allows to scan the whole parameter space,
allowing arbitrarily large soft terms. Still the low-energy region is
statistically favoured (even before including dark matter or g-2 constraints).
Contrary to other studies, the results are almost unaffected by changing the
upper limits taken for the soft terms. The results are also remarkable stable
when using flat or logarithmic priors, a fact that arises from the larger
statistical weight of the low-energy region in both cases. Then we incorporate
all the important experimental constrains to the analysis, obtaining a map of
the probability density of the MSSM parameter space, i.e. the forecast of the
MSSM. Since not all the experimental information is equally robust, we perform
separate analyses depending on the group of observables used. When only the
most robust ones are used, the favoured region of the parameter space contains
a significant portion outside the LHC reach. This effect gets reinforced if the
Higgs mass is not close to its present experimental limit and persits when dark
matter constraints are included. Only when the g-2 constraint (based on
data) is considered, the preferred region (for ) is well inside
the LHC scope. We also perform a Bayesian comparison of the positive- and
negative- possibilities.Comment: 42 pages: added figures and reference
Indirect and direct detection prospect for TeV dark matter in the MSSM-9
We investigate the prospects of indirect and direct dark matter searches
within the minimal supersymmetric standard model with nine parameters (MSSM-9).
These nine parameters include three gaugino masses, Higgs, slepton and squark
masses, all treated independently. We perform a Bayesian Monte Carlo scan of
the parameter space taking into consideration all available particle physics
constraints such as the Higgs mass of 126 GeV, upper limits on the scattering
cross-section from direct-detection experiments, and assuming that the MSSM-9
provides all the dark matter abundance through thermal freeze-out mechanism.
Within this framework we find two most probable regions for dark matter: 1-TeV
higgsino-like and 3-TeV wino-like neutralinos. We discuss prospects for future
indirect (in particular the Cherenkov Telescope Array, CTA) and direct
detection experiments. We find that for slightly contracted dark matter
profiles in our Galaxy, which can be caused by the effects of baryonic infall
in the Galactic center, CTA will be able to probe a large fraction of the
remaining allowed region in synergy with future direct detection experiments
like XENON-1T.Comment: 8 pages, 3 figure
The health of SUSY after the Higgs discovery and the XENON100 data
We analyze the implications for the status and prospects of supersymmetry of
the Higgs discovery and the last XENON data. We focus mainly, but not only, on
the CMSSM and NUHM models. Using a Bayesian approach we determine the
distribution of probability in the parameter space of these scenarios. This
shows that, most probably, they are now beyond the LHC reach . This negative
chances increase further (at more than 95% c.l.) if one includes dark matter
constraints in the analysis, in particular the last XENON100 data. However, the
models would be probed completely by XENON1T. The mass of the LSP neutralino
gets essentially fixed around 1 TeV. We do not incorporate ad hoc measures of
the fine-tuning to penalize unnatural possibilities: such penalization arises
automatically from the careful Bayesian analysis itself, and allows to scan the
whole parameter space. In this way, we can explain and resolve the apparent
discrepancies between the previous results in the literature. Although SUSY has
become hard to detect at LHC, this does not necessarily mean that is very
fine-tuned. We use Bayesian techniques to show the experimental Higgs mass is
at off the CMSSM or NUHM expectation. This is substantial but
not dramatic. Although the CMSSM or the NUHM are unlikely to show up at the
LHC, they are still interesting and plausible models after the Higgs
observation; and, if they are true, the chances of discovering them in future
dark matter experiments are quite high
El Papus: una revolució satÃrica que va copar la crÃtica humorÃstica espanyola de juliol de 1975 a març de 1976
El present article analitza com el setmanari satÃric El Papus, que neix inspirat i copiant
dues revistes trencadores i amb èxit de vendes, com ara la francesa Hara-Kiri i l'espanyola
Barrabás, va protagonitzar una de les tirades i difusions més importants a Espanya de
juliol de 1975 a març de 1976. Va arribar als 236.000 exemplars de tirada i, fins i tot, l'extra
de març de 1976 en va registrar 400.000. A través de l'anà lisi de les dades registrades en
l'Oficina de Justificació de la Difusió (OJD), s'ha comprovat detalladament l'evolució de la
difusió de la revista i s'observen quatre clÃmaxs importants. Aixà mateix, s'explica la
trajectòria del setmanari atenent a factors governamentals, socials i comunicatius.This article examines how the satirical weekly magazine El Papus, which was initially
inspired by and copied two groundbreaking magazines (the French Hara-Kiri and the
Spanish Barrabás), achieved one of the largest print runs and circulations in Spain in the
period of July 1975 to March 1976. It reached a regular print run of 236,000 copies, while
its March 1976 extra rose to 400,000. The study of the data from the Spanish Circulation
Audit Bureau (OJD) has provided a detailed look at the way in which this magazineÂ’s
distribution evolved, revealing four main high points. Also discussed here is the course
of El PapusÂ’s development in response to governmental, social and communicationrelated
factors
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