492 research outputs found
Heavy Z': resonant versus non-resonant searches
Collider searches for new vector-like particles such as Z' have mostly been
pursued by looking for a peak in the invariant mass spectrum of the decay
products. However off-shell Z' exchange may leave an imprint on other kinematic
distributions, leading thus to non-resonant searches. The aim of this paper is
to assess, in the context of the LHC, the interplay between resonant
(s-channel) and non-resonant (t-channel) searches for a generic leptophobic Z'
model. We show in particular that while non-resonant searches are less
sensitive to small couplings, they tend to be more adapted at high masses and
large couplings. We discuss our findings both at the level of the current
limits and the expectations at higher luminosities
BMSSM Higgses at 125 GeV
The BMSSM framework is an effective theory approach that encapsulates a
variety of extensions beyond the MSSM with which it shares the same field
content. The lightest Higgs mass can be much heavier than in the MSSM without
creating a tension with naturalness or requiring superheavy stops. The
phenomenology of the Higgs sector is at the same time much richer. We
critically review the properties of a Higgs with mass around 125GeV in this
model. In particular, we investigate how the rates in the important inclusive 2
photons channel, the 2 photons + 2 jets and the ZZ to 4 leptons (and/or WW) can
be enhanced or reduced compared to the standard model and what kind of
correlations between these rates are possible. We consider both a vanilla model
where stops have moderate masses and do not mix and a model with large mixing
and a light stop. We show that in both cases there are scenarios that lead to
enhancements in these rates at a mass of 125GeV corresponding either to the
lightest Higgs or the heaviest CP-even Higgs of the model. In all of these
scenarios we study the prospects of finding other signatures either of the
125GeV Higgs or those of the heavier Higgses. In most cases the \oo{\tau}\tau
channels are the most promising. Exclusion limits from the recent LHC Higgs
searches are folded in our analyses while the tantalising hints for a Higgs
signal at 125GeV are used as an example of how to constrain the BMSSM and/or
direct future searches.Comment: 21 p v1 Tevatron result added in addendum, typo
Relic density calculations beyond tree-level, exact calculations versus effective couplings: the ZZ final state
The inferred value of the relic density from cosmological observations has
reached a precision that is akin to that of the LEP precision measurements.
This level of precision calls for the evaluation of the annihilation cross
sections of dark matter that goes beyond tree-level calculations as currently
implemented in all codes for the computation of the relic density. In
supersymmetry radiative corrections are known to be large and thus must be
implemented. Full one-loop radiative corrections for many annihilation
processes have been performed. It is important to investigate whether the bulk
of these corrections can be parameterised through an improved Born
approximation that can be implemented as a selection of form factors to a
tree-level code. This paper is a second in a series that addresses this issue.
After having provided these form factors for the annihilation of the
neutralinos into fermions, which cover the case of a bino-like LSP (Lightest
Supersymmetric Particle), we turn our attention here to a higgsino-like dark
matter candidate through its annihilation into . We also investigate the
cases of a mixed LSP. In all cases we compare the performance of the form
factor approach with the result of a full one-loop correction. We also study
the issue of the renormalisation scheme dependence. An illustration of the
phenomenon of non decoupling of the heavy sfermions that takes place for the
annihilation of the lightest neutralino into is also presented.Comment: 20
Higgs couplings beyond the Standard Model
We consider the Higgs boson decay processes and its production, and provide a
parameterisation tailored for testing models of new physics beyond the Standard
Model. We also compare our formalism to other existing parameterisations based
on scaling factors in front of the couplings and to effective Lagrangian
approaches. Different formalisms allow to best address different aspects of the
Higgs boson physics. The choice of a particular parameterisation depends on a
non-obvious balance of quantity and quality of the available experimental data,
envisaged purpose for the parameterisation and degree of model independence,
importance of the radiative corrections, scale at which new particles appear
explicitly in the physical spectrum. At present only simple parameterisations
with a limited number of fit parameters can be performed, but this situation
will improve with the forthcoming experimental LHC data. Detailed fits can only
be performed by the experimental collaborations at present, as the full
information on the different decay modes is not completely available in the
public domain. It is therefore important that different approaches are
considered and that the most detailed information is made available to allow
testing the different aspects of the Higgs boson physics and the possible hints
beyond the Standard Model.Comment: 22 pages, 5 figures, 5 tables. This version is an update including
the most recent Higgs data and new fits to two extra model
Higgs couplings: disentangling New Physics with off-shell measurements
After the discovery of a scalar resonance, resembling the Higgs boson, its
couplings have been extensively studied via the measurement of various
production and decay channels on the invariant mass peak. Recently, it has been
suggested the possibility to use off-shell measurements: in particular, CMS has
published results based on the high- invariant mass cross section of the
process , which contains the contribution of the Higgs. While this
measurement has been interpreted as a constraint on the Higgs width after very
specific assumptions are taken on the Higgs couplings, in this letter we show
that a much more model-independent interpretation is possible.Comment: 6pp, 1 figur
One-loop corrections, uncertainties and approximations in neutralino annihilations: Examples
The extracted value of the relic density has reached the few per-cent level
precision. One can therefore no longer content oneself with calculations of
this observable where the annihilation processes are computed at tree-level,
especially in supersymmetry where radiative corrections are usually large.
Implementing full one-loop corrections to all annihilation processes that would
be needed in a scan over parameters is a daunting task. On the other hand one
may ask whether the bulk of the corrections are taken into account through
effective couplings of the neutralino that improve the tree-level calculation
and would be easy to implement. We address this issue by concentrating in this
first study on the neutralino coupling to i) fermions and sfermions and ii) Z.
After constructing the effective couplings we compare their efficiency compared
to the full one-loop calculation and comment on the failures and success of the
approach. As a bonus we point out that large non decoupling effects of heavy
sfermions could in principle be measured in the annihilation process, a point
of interest in view of the latest limit on the squark masses from the LHC. We
also comment on the scheme dependencies of the one-loop corrected results
Barentin – Rue des Catillons
L’opération de fouille archéologique a été effectuée en amont à la réalisation d’un lotissement par la société Les Terrains Normands, sur les parcelles 25 et 26. Le site est localisé au nord-est de la commune de Barentin, ville du Pays de Caux, sur le rebord du plateau dominant la vallée de l’Austreberthe, petit affluent de la Seine.La superficie ouverte est de 5 462 m2 répartis en 4 zones. Au total, ce sont 115 structures excavées (dont sept annulées) qui ont été mises au jour. La fouille a..
Higgs couplings as a probe of New Physics
We consider the Higgs boson decay processes and its production and provide a
parameterisation tailored for testing models of new physics. The choice of a
particular parameterisation depends on a non-obvious balance of quantity and
quality of the available experimental data, envisaged purpose for the
parameterisation and degree of model independence. At present only simple
parameterisations with a limited number of fit parameters can be performed, but
this situation will improve with the forthcoming experimental LHC data. It is
therefore important that different approaches are considered and that the most
detailed information is made available to allow testing the different aspects
of the Higgs boson physics and the possible hints beyond the Standard Model.Comment: 4p, Proceeding for HPNP 2013, Toyama, Feb. 2013; based on
arXiv:1210.812
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