136 research outputs found
Decays of a NMSSM CP-odd Higgs in the low-mass region
A popular regime in the NMSSM parameter space involves a light CP-odd Higgs
. This scenario has consequences for e.g. light singlino Dark Matter
annihilating in the -funnel. In order to confront the pseudoscalar to
experimental limits such as flavour observables, Upsilon decays or Beam-Dump
experiments, it is necessary to control the interactions of this particle with
hadronic matter and derive the corresponding decays. The partonic description
cannot be relied upon for masses close to GeV and we employ a
chiral lagrangian, then extended to a spectator model for somewhat larger
masses, to describe the interplay of the CP-odd Higgs with hadrons.
Interestingly, a mixing can develop between and neutral pseudoscalar
mesons, leading to substantial hadronic decays and a coupling of to the
chiral anomaly. Additionally, quartic -meson couplings induce tri-meson
decays of the Higgs pseudoscalar. We investigate these effects and propose an
estimate of the Higgs widths for masses below GeV. While we focus
on the case of the NMSSM, our results are applicable to a large class of
models.Comment: 23 pages, 9 figures, published versio
A New Tool for the study of the CP-violating NMSSM
Supersymmetric extensions of the Standard Model open up the possibility for
new types of CP-violation. We consider the case of the Next-to-Minimal
Supersymmetric Standard Model where, beyond the phases from the soft
lagrangian, CP-violation could enter the Higgs sector directly at tree-level
through complex parameters in the superpotential. We develop a series of
Fortran subroutines, cast within the public tool NMSSMTools and allowing for a
phenomenological analysis of the CP-violating NMSSM. This new tool performs the
computation of the masses and couplings of the various new physics states in
this model: leading corrections to the sparticle masses are included; the
precision for the Higgs masses and couplings reaches the full one-loop and
leading two-loop order. The two-body Higgs and top decays are also attended. We
use the public tools HiggsBounds and HiggsSignals to test the Higgs sector.
Additional subroutines check the viability of the sparticle spectrum in view of
LEP-limits and constrain the phases of the model via a confrontation to the
experimentally measured Electric Dipole Moments. These tools will be made
publicly available in the near future. In this paper, we detail the workings of
our code and illustrate its use via a comparison with existing results. We also
consider some consequences of CP-violation for the NMSSM Higgs sector.Comment: 60 pages, 9 figures, updated versio
Update of the flavour-physics constraints in the NMSSM
We consider the impact of several flavour-changing observables in the -
and the Kaon sectors on the parameter space of the NMSSM, in a minimal flavour
violating version of this model. Our purpose consists in updating our previous
results in arXiv:0710.3714 and designing an up-to-date flavour test for the
public package NMSSMTools. We provide details concerning our implementation of
the constraints in a series of brief reviews of the current status of the
considered channels. Finally, we present a few consequences of these flavour
constraints for the NMSSM, turning to two specific scenarios: one is
characteristic of the MSSM-limit and illustrates the workings of charged-Higgs
and genuinely supersymmetric contributions to flavour-changing processes; the
second focus is a region where a light CP-odd Higgs is present. Strong limits
are found whenever an enhancement factor - large , light ,
resonant pseudoscalar - comes into play.Comment: 22 pages, 7 figure
NMSSM interpretations of the observed Higgs signal
While the properties of the signal that was discovered in the Higgs searches
at the LHC are consistent so far with the Higgs boson of the Standard Model
(SM), it is crucial to investigate to what extent other interpretations that
may correspond to very different underlying physics are compatible with the
current results. We use the Next-to-Minimal Supersymmetric Standard Model
(NMSSM) as a well-motivated theoretical framework with a sufficiently rich
Higgs phenomenology to address this question, making use of the public tools
HiggsBounds and HiggsSignals in order to take into account comprehensive
experimental information on both the observed signal and on the existing limits
from Higgs searches at LEP, the TeVatron and the LHC. We find that besides the
decoupling limit resulting in a single light state with SM-like properties,
several other configurations involving states lighter or quasi-degenerate with
the one at about 125 GeV turn out to give a competitive fit to the Higgs data
and other existing constraints. We discuss the phenomenology and possible
future experimental tests of those scenarios, and compare the features of
specific scenarios chosen as examples with those arising from a more global
fit.Comment: 46 pages, 23 figures. Version accepted by JHE
Towards Higgs masses and decay widths satisfying the symmetries in the (N)MSSM
In models with an extended Higgs sector, such as the (N)MSSM, scalar states
mix with one another. Yet, the concept of Higgs mixing is problematic at the
radiative level, since it introduces both a scheme and a gauge dependence. In
particular, the definition of Higgs masses and decay amplitudes can be impaired
by the presence of gauge-violating pieces of higher order. We discuss in depth
the origin and magnitude of such effects and suggest two strategies preserving
or restoring gauge invariance. In addition, the intuitive concept of mixing and
the simplicity of its definition in terms of two-point diagrams can make it
tempting to include higher-order corrections on this side of the calculation,
irrespectively of the order achieved in vertex diagrams. Using the global
-symmetry in the decoupling limit, we show that no
improvement can be expected from such an approach at the level of the Higgs
decays, but that, on the contrary, the higher-order terms may lead to
numerically large spurious effects.Comment: 49 pages, 12 figures, version accepted by EPJ
Constraints from the Muon g-2 on the Parameter Space of the NMSSM
We generalize the computation of supersymmetric contributions to the muon
anomalous magnetic moment (g-2)_mu to the NMSSM. In the presence of a light
CP-odd Higgs scalar, these can differ considerably from the MSSM. We discuss
the amount of these contributions in regions of the parameter space of the
general NMSSM compatible with constraints from B physics. In the mSUGRA-like
cNMSSM, constraints from (g-2)_mu prefer regions in parameter space
corresponding to a low SUSY breaking scale.Comment: 19 pages, 6 figure
Decays of a bino-like particle in the low-mass regime
We study the phenomenology associated with a light bino-like neutralino with
mass under the tau mass in the context of the R-parity violating Minimal
Supersymmetric Standard Model. This is a well-motivated example of scenarios
producing potentially light and long-lived exotic particles, which might be
testable in far-detector experiments, such as the FASER experiment at the Large
Hadron Collider. A quantitative assessment of the discovery potential or the
extraction of limits run through a detailed understanding of the interactions
of the light exotic fermion with Standard Model matter, in particular, the
hadronic sector. Here, we propose a systematic analysis of the decays of such a
particle and proceed to a model-independent derivation of the low-energy
effects, so that this formalism may be transposed to other UV-completions or
even stand as an independent effective field theory. We then stress the
diversity of the possible phenomenology and more specifically discuss the
features associated with the R-parity violating supersymmetric framework, for
example neutron-antineutron oscillations.Comment: 50 pages, 5 figure
CDF Multi-Muon Events and Singlet Extensions of the MSSM
We discuss a generalization of the minimal supersymmetric extension of the
Standard Model in the form of three additional singlet superfields, which would
explain the essential features of the CDF multi-muon events presented recently:
a large production cross section of ~ 100 pb originates from the production of
a CP-odd scalar A with a mass in the 70 - 80 GeV range and a large value of
tan(beta) ~ 40. The CP-odd scalar A decays dominantly into CP-odd and CP-even
scalars a_1 and h_1, which generate decay cascades h_1 -> 2 h_2 -> 4 a_2 -> 8
tau-leptons, and a_1 -> h_1 a_2 with h_1 decaying as above. The decay a_2 ->
tau+ tau- is slow, leading to a lifetime of O(20) ps. The phenomenology of the
model differs from similar scenarios presented before in that one of the two
cascades leads to 10 instead of 8 tau-leptons, and additional production
processes like associate A production with b b-bar pairs are relevant.Comment: 10 pages, comments on the required total cross section added, to
appear in MPL
, Dark Matter and in the NMSSM
We study regions in the parameter space of the NMSSM which are able to
simultaneously explain the current measured values for the mass and
the muon anomalous magnetic moment , and provide a dark matter relic
density consistent with the observations as well as constraints from detection
experiments. The corresponding regions feature light charginos, sleptons and
staus in the 100-800~GeV range, at least some of them with masses below 150~GeV
such that the electroweakly-interacting SUSY particles generate sufficiently
large contributions to . The LSP is always singlino-like with a mass below
140~GeV, and could possibly remain invisible even at future detection
experiments. Decays of electroweak sparticles proceed through cascades via
staus and/or sleptons which makes their detection challenging. We propose
benchmark points for future searches of such sparticles. The lightest CP-even
scalar may have a mass in the 95-98~GeV range with, however, modest signal
rates in view of the mild excesses reported in this range at LEP and by CMS at
the LHC.Comment: 8 pages, 6 figures, references added, figures improved, SLHA files of
bench mark points added as ancillary file
Bottomonium spectroscopy with mixing of eta_b states and a light CP-odd Higgs
The mass of the eta_b(1S), measured recently by BABAR, is significantly lower
than expected from QCD predictions for the Upsilon(1S) - eta_b(1S) hyperfine
splitting. We suggest that the observed eta_b(1S) mass is shifted downwards due
to a mixing with a CP-odd Higgs scalar A with a mass m_A in the range 9.4 -
10.5 GeV compatible with LEP, CLEO and BABAR constraints. We determine the
resulting predictions for the spectrum of the eta_b(nS) - A system and the
branching ratios into tau^+ tau^- as functions of m_A.Comment: 4 pages, 4 figures, submitted to PRL, misprint correcte
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