337 research outputs found
Coannihilation with a chargino and gauge boson pair production at one-loop
We present a complete calculation of the electroweak one-loop corrections to
the relic density within the MSSM framework. In the context of the neutralino
as dark matter candidate, we review different scenarios of annihilation and
coannihilation with a chargino. In particular we investigate predictions for
the annihilation into gauge boson pairs for different kinds of neutralino:
bino-, wino- and higgsino-like. We present some interesting effects which are
not present at tree-level and show up at one-loop. To deal with the large
number of diagrams occuring in the calculations, we have developed an automatic
tool for the computation at one-loop of any process in the MSSM. We have
implemented a complete on-shell gauge invariant renormalization scheme, with
the possibility of switching to other schemes. We emphasize the variations due
to the choice of the renormalization scheme, in particular the one-loop
definition of the parameter tan(beta).Comment: 4 pages, 5 figures, to appear in the proceedings of the 17th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions (SUSY09), Boston, USA, 5-10 June, 200
Automatised full one-loop renormalisation of the MSSM I: The Higgs sector, the issue of tan(beta) and gauge invariance
We give an extensive description of the renormalisation of the Higgs sector
of the minimal supersymmetric model in SloopS. SloopS is an automatised code
for the computation of one-loop processes in the MSSM. In this paper, the first
in a series, we study in detail the non gauge invariance of some definitions of
tan(beta). We rely on a general non-linear gauge fixing constraint to make the
gauge parameter dependence of different schemes for tan(beta) at one-loop
explicit. In so doing, we update, within these general gauges, an important
Ward-Slavnov-Taylor identity on the mixing between the pseudo-scalar Higgs,
A^0, and the Z^0. We then compare the tan(beta) scheme dependence of a few
observables. We find that the best tan(beta) scheme is the one based on the
decay A^0 -> tau^+ tau^- because of its gauge invariance, being unambiguously
defined from a physical observable, and because it is numerically stable. The
oft used DRbar scheme performs almost as well on the last count, but is usually
defined from non-gauge invariant quantities in the Higgs sector. The use of the
heavier scalar Higgs mass in lieu of tan(beta) though related to a physical
parameter induces too large radiative corrections in many instances and is
therefore not recommended.Comment: 34 pages, 1 figure, typos corrected, accepted for publication in
Phys. Rev.
Relic density at one-loop with gauge boson pair production
We have computed the full one-loop corrections (electroweak as well as QCD)
to processes contributing to the relic density of dark matter in the MSSM where
the LSP is the lightest neutralino. We cover scenarios where the most important
channels are those with gauge boson pair production. This includes the case of
a bino with some wino admixture, a higgsino and a wino. In this paper we
specialise to the case of light dark matter much below the TeV scale. The
corrections can have a non-negligible impact on the predictions and should be
taken into account in view of the present and forthcoming increasing precision
on the relic density measurements. Our calculations are made with the help of
\SloopS, an automatic tool for the calculation of one-loop processes in the
MSSM. The renormalisation scheme dependence of the results as concerns \tgb
is studied.Comment: 25 pages, 10 figures, Citations adde
Automatised full one-loop renormalisation of the MSSM II: The chargino-neutralino sector, the sfermion sector and some applications
An on-shell renormalisation programme for the chargino/neutralino and the
sfermion sectors within the Minimal Supersymmetric Standard Model as
implemented in a fully automated code, SloopS, for the calculation of one-loop
processes at the colliders and in astrophysics, is presented. This is a sequel
to our study in arXiv:0807.4668 [hep-ph] where an on-shell renormalisation of
the Higgs (and the gauge/fermion) sector is performed. The issue of mixing is
treated in a unified and coherent manner in all these sectors, in particular we
give some new insight into the renormalisation of the mixing angle in the
sfermion sector and like with the Higgs sector and the issue of tan(beta) we
discuss different schemes. We also perform numerical comparisons between our
code SloopS and different results found in the literature. In particular we
consider loop corrections to the neutralino and sfermion masses, chargino pair
production and stau pair production in e^{+}e^{-} colliders, as well as a few
decays of the heavier chargino. For all these observables, we analyse the
tan(beta) scheme dependence using different definitions of this parameter and
comment on the impact of using different renormalisation of the mixing
parameter in the sfermion sector.Comment: 41 pages, 14 figures, added reference
The stabilized automorphism group of odometers and of Toeplitz subshifts
We characterize the stabilized automorphism group for odometers and Toeplitz
subshifts and then prove an invariance property of the stabilized automorphism
group of these dynamical systems. A particular case of interest is that for
torsion free odometers the stabilized automorphism group is a full isomorphism
invariant
Loop-induced photon spectral lines from neutralino annihilation in the NMSSM
We have computed the loop-induced processes of neutralino annihilation into
two photons and, for the first time, into a photon and a Z boson in the
framework of the NMSSM. The photons produced from these radiative modes are
monochromatic and possess a clear "smoking gun" experimental signature. This
numerical analysis has been done with the help of the SloopS code, initially
developed for automatic one-loop calculation in the MSSM. We have computed the
rates for different benchmark points coming from SUGRA and GMSB soft SUSY
breaking scenarios and compared them with the MSSM. We comment on how this
signal can be enhanced, with respect to the MSSM, especially in the low mass
region of the neutralino. We also discuss the possibility of this observable to
constrain the NMSSM parameter space, taking into account the latest limits from
the FERMI collaboration on these two modes.Comment: 18 pages, 3 figures. Minor clarifications added in the text. Typing
mistakes and references corrected. Matches published versio
Searching for Dark Matter at the LHC with a Mono-Z
We investigate a mono-Z process as a potential dark matter search strategy at
the LHC. In this channel a single Z boson recoils against missing transverse
momentum, attributed to dark matter particles, , which escape the
detector. This search strategy is related, and complementary to, monojet and
monophoton searches. For illustrative purposes we consider the process
in a toy dark matter model, where the Z boson is
emitted from either the initial state quarks, or from the internal propagator.
Among the signatures of this process will be a pair of muons with high pT that
reconstruct to the invariant mass of the Z, and large amounts of missing
transverse energy. Being a purely electroweak signal, QCD and other Standard
Model backgrounds are relatively easily removed with modest selection cuts. We
compare the signal to Standard Model backgrounds and demonstrate that, even for
conservative cuts, there exist regions of parameter space where the signal may
be clearly visible above background in future LHC data, allowing either new
discovery potential or the possibility of supplementing information about the
dark sector beyond that available from other observable channels.Comment: 11 pages, 13 figure
Surgical Treatment of Spinal Meningiomas in the Elderly (≥75 Years): Which Factors Affect the Neurological Outcome? An International Multicentric Study of 72 Cases
(1) Background: With the increasing life expectancy in the Western world, an increasing number of old patients presents with spinal meningioma. Considering the benign nature of these tumors, the functional outcome remains of great importance, since more people reach old age in general conditions of well-being and satisfactory autonomy. (2) Methods: We conducted an international multicenter retrospective study to investigate demographic, clinical and radiological data in a population of elderly patients (≥75 years of age) undergoing surgery for SM from January 2000 to December 2020 in four European referral centers. The aim was to identify prognostic and predictive factors for a good postoperative functional outcome. (3) Results: 72 patients were included in the study. Complete tumor resection (Simpson I or II) was achieved in 67 (95.7%) cases. Intraoperative complications were reported in 7 (9.9%) patients while postoperative complications were found in 12 (16.7%). An excellent general postoperative status (McCormick I and II) was achieved in 65.3%. Overall, surgical resection had a good impact on patients’ functional outcome (86.1% either showing an improvement or maintaining a good preoperative status). Uni- and multivariate analyses found that both age and preoperative modified McCormick independently correlated with relative outcome (coeff = −0.058, p = 0.0251; coeff = 0.597, p < 0.0001) and with postoperative status (coeff = 0.058, p = 0.02507; coeff = 0.402, p = 0.00027), respectively. (4) Conclusions: Age and preoperative modified McCormick were found to be independent prognostic factors. Nevertheless, advanced age (≥75), per se, did not seem to contraindicate surgery, even in those with severe preoperative neurological deficits. The functional results sustain the need for surgical resection of SM in the elderly
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