83 research outputs found
Two Higgs bosons near 125 GeV in the complex NMSSM and the LHC Run-I data
We analyse the impact of explicit CP-violation in the Higgs sector of the
Next-to-Minimal Supersymmetric Standard Model (NMSSM) on its consistency with
the Higgs boson data from the Large Hadron Collider (LHC). Through detailed
scans of the parameter space of the complex NMSSM for certain fixed values of
one of its CP-violating (CPV) phases, we obtain a large number of points
corresponding to five phenomenologically relevant scenarios containing GeV Higgs boson(s). We focus, in particular, on the scenarios where the
visible peaks in the experimental samples can actually be explained by two
nearly mass-degenerate neutral Higgs boson states. We find that some points
corresponding to these scenarios give an overall slightly improved fit to the
data, more so for non-zero values of the CPV phase, compared to the scenarios
containing a single Higgs boson near 125 GeV.Comment: 22 pages, 3 figures. Substantially revised text, improved results and
figures, overall conclusions unchanged. Some added references. Version to
appear in the special issue "Supersymmetry beyond the (N)MSSM" of AHE
Improved Constraints on Z' Bosons from Electroweak Precision Data
We analyze various models with an extra U(1) gauge symmetry in addition to
the Standard Model (SM) gauge group at low energies, and impose limits on the
mass of the neutral Z' boson, M_Z', predicted in all such models, and on the
Z-Z' mixing angle, theta_ZZ'. The precision electroweak data strongly constrain
theta_ZZ' to very small values and for most models we find lower limits on M_Z'
of order 1 TeV. In one case we obtain a somewhat better fit than in the SM
(although this is only marginally statistically significant) and here we find a
weak upper limit at the 90% C.L.Comment: 18 pages, 10 figures, final version as it will appear in Journal
(JHEP
Quantum interference among heavy NMSSM Higgs bosons
In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), it is possible
to have strong mass degeneracies between the new singlet-like scalar and the
heavy doublet-like scalar, as well as between the singlet-like and doublet-like
pseudoscalar Higgs states. When the difference in the masses of such states is
comparable with the sum of their widths, the quantum mechanical interference
between their propagators can become significant. We study these effects by
taking into account the full Higgs boson propagator matrix in the calculation
of the production process of pairs in gluon fusion at the Large
Hadron Collider (LHC). We find that, while these interference effects are
sizeable, they are not resolvable in terms of the distributions of differential
cross sections, owing to the poor detector resolution of the
invariant mass. They are, however, identifiable via the inclusive cross
sections, which are subject to significant variations with respect to the
standard approaches, wherein the propagating Higgs bosons are treated
independently from one another. We quantify these effects for several
representative benchmark points, extracted from a large set of points, obtained
by numerical scanning of the NMSSM parameter space, that satisfy the most
important experimental constraints currently available.Comment: 18 pages, 5 figures, 2 tables. Revised benchmark points and figures,
overall results and conclusions unchanged. Version to appear in PR
Closing in on the Wino LSP via trilepton searches at the LHC
The neutralino dark matter (DM) predicted by the Minimal Supersymmetric
Standard Model (MSSM) has been probed in several search modes at the Large
Hadron Collider (LHC), one of the leading ones among which is the trilepton
plus missing transverse momentum channel. The experimental analysis of this
mode has, however, been designed to probe mainly a bino-like DM, originating in
the decays of a pair of next-to-lightest neutralino and lightest chargino, both
of which are assumed to be wino-like. In this study, we analyse how this
trilepton channel can be tuned for probing also the wino-like DM. We note that,
while the mentioned standard production mode generally leads to a relatively
poor sensitivity for the wino-like DM, there are regions in the MSSM parameter
space where the net yield in the trilepton final state can be substantially
enhanced at the LHC with TeV. This is achieved by taking into
account also an alternative channel, pair-production of the wino-like DM itself
in association with the heavier chargino, and optimisation of the kinematical
cuts currently employed by the LHC collaborations. In particular, we find that
the cut on the transverse mass of the third lepton highly suppresses both the
signal channels and should therefore be discarded in this DM scenario. We
perform a detailed detector-level study of some selected parameter space points
that are consistent with the most important experimental constraints, including
the recent ones from the direct and indirect DM detection facilities. Our
analysis demonstrates the high complementarity of the two channels, with their
combined significance reaching above 4 for a wino-like DM mass around
100 GeV, with an integrated luminosity as low as 100 fb.Comment: 22 pages, 8 figures, 4 tables. Exclusion limits from Dark Matter
Indirect Detection also taken into account. Significant improvements in
figures and text. Final results and conclusions unchanged. Version to appear
in JHE
Two Higgs bosons near 125 GeV in the NMSSM: beyond the narrow width approximation
In the next-to-minimal supersymmetric (NMS) Standard Model (SM), it is
possible for either one of the additional singlet-like scalar and pseudoscalar
Higgs bosons to be almost degenerate in mass with the ~125 GeV SM-like Higgs
state. In the real NMSSM (rNMSSM), when the mass difference between two scalar
states is comparable to their individual total decay widths, the quantum
mechanical interference, due to the relevant diagonal as well as off-diagonal
terms in the propagator matrix, between them can become sizable. This
possibility invalidates usage of the narrow width approximation (NWA) to
compute the cross section for the production of a di-photon pair with a given
invariant mass via resonant Higgs boson(s) in the gluon fusion process at the
Large Hadron Collider (LHC). When, motivated by the baryon asymmetry of the
universe, CP-violating (CPV) phases are explicitly invoked in the Higgs sector
of the NMSSM, all the interaction eigenstates mix to give five CP-indefinite
physical Higgs bosons. In this scenario, the interference effects due the
off-diagonal terms in the Higgs mass matrix that mix the pseudoscalar-like
state with the SM-like one can also become significant, when these two are
sufficiently mass-degenerate. We perform a detailed analysis, in both the real
and complex NMSSM, of these interference effects, when the full propagator
matrix is taken into account, in the production of a photon pair with an
invariant mass near 125 GeV through gluon fusion. We find that these effects
can account for up to ~40% of the total cross section for certain model
parameter configurations. We also investigate how such mutually interfering
states contributing to the ~125 GeV signal observed at the LHC can be
distinguished from a single resonance.Comment: 26 pages, 9 figures. Typos corrected, some figures and text improved.
Version published in EPJ
A light NMSSM pseudoscalar Higgs boson at the LHC Run 2
We revisit the light pseudoscalar in the Next-to-Minimal Supersymmetric
Standard Model (NMSSM) with partial universality at some high unification scale
in order to delineate the parameter space regions consistent with up-to-date
theoretical and experimental constraints and examine to what extent this state
can be probed by the Large Hadron Collider (LHC) during Run 2. We find that it
can be accessible through a variety of signatures proceeding via and/or , the former assuming hadronic decays and the
latter two -tags within a fat jet or two separate slim ones. Herein, the
light pseudoscalar state is produced from a heavy Higgs boson decay in either
pairs or singly in association with a boson (in turn decaying into
electrons/muons).Comment: 6 pages, 6 figures, 1 table - Talk given at the Toyama International
Workshop on Higgs as a Probe of New Physics 2015, 11-15, February, 2015,
Toyama, Japa
A light NMSSM pseudoscalar Higgs boson at the LHC redux
The Next-to-Minimal Supersymmetric Standard Model (NMSSM) contains a
singlet-like pseudoscalar Higgs boson in addition to the doublet-like
pseudoscalar of the Minimal Supersymmetric Standard Model. This new
pseudoscalar can have a very low mass without violating the LEP exclusion
constraints and it can potentially provide a hallmark signature of non-minimal
supersymmetry at the LHC. In this analysis we revisit the light pseudoscalar in
the NMSSM with partial universality at some high unification scale. We
delineate the regions of the model's parameter space that are consistent with
the up-to-date theoretical and experimental constraints, from both Higgs boson
searches and elsewhere (most notably -physics), and examine to what extent
they can be probed by the LHC. To this end we review the most important
production channels of such a Higgs state and assess the scope of its
observation at the forthcoming Run-2 of the LHC. We conclude that the
-associated production of the pseudoscalar, which has been emphasised
in previous studies, does not carry much promise anymore, given the measured
mass of the Higgs boson at the LHC. However, the decays of one of the heavier
scalar Higgsbosons of the NMSSM can potentially lead to the discovery of its
light pseudoscalar. Especially promising are the decays of one or both of the
two lightest scalar states into a pseudoscalar pair and of the heaviest scalar
into a pseudoscalar and a boson. Since the latter channel has not been
explored in detail in the literature so far, we provide details of some
benchmark points which can be probed for establishing its signature.Comment: 33 pages, 13 figures. Typos corrected, figures and some text
improved, references added. Version to appear in JHE
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