159 research outputs found
Testing the higgsino-singlino sector of the NMSSM with trileptons at the LHC
We propose a simplified light higgsino-singlino scenario in the NMSSM, in
which the masses of the chargino and the lightest neutralino determine the
masses and couplings of all 3 lightest neutralinos. This scenario is
complementary to the simplified wino-like chargino/neutralino scenario used
conventionally for the interpretation of results from trilepton searches, and
motivated by lower bounds on the gluino mass in the case of GUT relations
between the wino and gluino masses. We present all masses and mixing angles
necessary for the determination of production cross sections of the chargino
and the 3 neutralinos in the form of Tables in the M_{neutralino_1} -
M_{chargino_1} plane, assuming Higgs mass motivated values for tan(beta)=2 and
lambda=0.6. We show that this scenario leads to considerable signal rates, and
present constraints in this plane from recent searches for trileptons at the
LHC.Comment: 16 pages, 1 Figure, 8 Table
Gradient flows for functions via multi-scale renormalization group equations
Renormalization schemes and cutoff schemes allow for the introduction of
various distinct renormalization scales for distinct couplings. We consider the
coupled renormalization group flow of several marginal couplings which depend
on just as many renormalization scales. The usual functions describing
the flow with respect to a common global scale are assumed to be given. Within
this framework one can always construct a metric and a potential in the space
of couplings such that the functions can be expressed as gradients of
the potential. Moreover the potential itself can be derived explicitly from a
prepotential which, in turn, determines the metric. Some examples of
renormalization group flows are considered, and the metric and the potential
are compared to expressions obtained elsewhere.Comment: 8 page
Possible explanation of excess events in the search for jets, missing transverse momentum and a Z boson in pp collisions
We study to which extent SUSY extensions of the Standard Model can describe
the excess of events of 3.0 standard deviations observed by ATLAS in the on-Z
signal region, respecting constraints by CMS on similar signal channels as well
as constraints from searches for jets and E^{miss}_T. GMSB-like scenarios are
typically in conflict with these constraints, and do not reproduce well the
shape of the E^{miss}_T distribution of the data. An alternative scenario with
two massive neutralinos can improve fits to the total number of events as well
as to the H_T and E^{miss}_T distributions. Such a scenario can be realised
within the NMSSM.Comment: 14 pages, 4 figures, 1 Table, more details of constraints and fits
are discussed, to appear in EPJ
Present Status and Future Tests of the Higgsino-Singlino Sector in the NMSSM
The light higgsino-singlino scenario of the NMSSM allows to combine a
naturally small parameter with a good dark matter relic density. Given
the new constraints on spin-dependent and spin-independent direct detection
cross sections in 2016 we study first which regions in the plane of chargino-
and LSP-masses below 300 GeV remain viable. Subsequently we investigate the
impact of searches for charginos and neutralinos at the LHC, and find that the
limits from run I do not rule out any additional region in this plane. Only the
HL-LHC at 3000 fb will test parts of this plane corresponding to
higgsino-like charginos heavier than 150 GeV and relatively light singlinos,
but notably the most natural regions with lighter charginos seem to remain
unexplored.Comment: 16 pages, 2 figures, added discussion on the remaining fine-tunin
A 750 GeV Diphoton Signal from a Very Light Pseudoscalar in the NMSSM
The excess of events in the diphoton final state near 750 GeV observed by
ATLAS and CMS can be explained within the NMSSM near the R-symmetry limit. Both
scalars beyond the Standard Model Higgs boson have masses near 750 GeV, mix
strongly, and share sizeable production cross sections in association with
b-quarks as well as branching fractions into a pair of very light
pseudoscalars. Pseudoscalars with a mass of ~ 210 MeV decay into collimated
diphotons, whereas pseudoscalars with a mass of ~ 500-550 MeV can decay either
into collimated diphotons or into three pi^0 resulting in collimated photon
jets. Various such scenarios are discussed; the dominant constraints on the
latter scenario originate from bounds on radiative Upsilon decays, but they
allow for a signal cross section up to 6.7 fb times the acceptance for
collimated multiphotons to pass as a single photon.Comment: Major update, 21 pages, scenarios with M_A ~ 210 MeV and M_A ~ 550
MeV added, references and output files from NMSSMTools added, section and
figure on Delta_eta of diphotons added. To appear in JHE
Possible Explanation of the Electron Positron Anomaly at 17 MeV in Transitions Through a Light Pseudoscalar
We estimate the values of Yukawa couplings of a light pseudoscalar A with a
mass of about 17 MeV, which would explain the anomaly observed in the
Atomki pair spectrometer experiment. The resulting couplings of A to up and
down type quarks are about 0.3 times the coupling of the standard Higgs boson.
Then constraints from K and B decays require that loop contributions to flavour
changing vertices cancel at least at the 10% level. Constraints from beam dump
experiments require the coupling of A to electrons to be larger than about 4
times the coupling of the standard Higgs boson, leading to a short enough A
life time consistent with an explanation of the anomaly.Comment: 12 pages, discussion of nuclear shell model corrected, to appear in
JHE
NMSPEC: A Fortran code for the sparticle and Higgs masses in the NMSSM with GUT scale boundary conditions
NMSPEC is a Fortran code that computes the sparticle and Higgs masses, as
well as Higgs decay widths and couplings in the NMSSM, with soft SUSY breaking
terms specified at MGUT. Exceptions are the soft singlet mass m_s^2 and the
singlet self coupling kappa, that are both determined in terms of the other
parameters through the minimization equations of the Higgs potential. We
present a first analysis of the NMSSM parameter space with universal SUSY
breaking terms at MGUT -- except for m_s and A_kappa -- that passes present
experimental constraints on sparticle and Higgs masses. We discuss in some
detail a region in parameter space where a SM-like Higgs boson decays
dominantly into two CP odd singlet-like Higgs states.Comment: 21 pages, 3 figure
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