2,515 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.
Locally C -Nash groups
This is a post-peer-review, pre-copyedit version of an article published in Revista Matemática Complutense. The final authenticated version is available online at : http://dx.doi.org/10.1007/s13163-018-0278-1We introduce the category of locally C-Nash groups, basic examples of such groups are complex algebraic groups. We prove that the latter form a full subcategory. We also show that both, abelian locally Nash and abelian locally C-Nash groups, can be characterised via meromorphic maps admitting an algebraic addition theorem; we give an invariant of such groups associated to the groups of periods of a chart at the identity. Finally, we prove that the category of simply connected abelian locally C-Nash groups coincides with that of universal coverings of the abelian complex irreducible algebraic groups (a complex version of a result of Hrushovski and Pillay in Isr J Math 85(1–3):203–262, 1994; Conflu Math 3(4):577–585, 2011)ElĂas Baro and Margarita Otero are partially supported by Spanish MTM2014-55565-P and Grupos UCM 910444. Juan de Vicente also supported by a grant of the International Program of Excellence in Mathematics at Universidad AutĂłnoma de Madri
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
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