151 research outputs found
Higgs boson production via vector-like top-partner decays: diphoton or multilepton plus multijets channels at the LHC
We first build a minimal model of vector-like quarks where the dominant Higgs
boson production process at LHC -- the gluon fusion -- can be significantly
suppressed, being motivated by the recent stringent constraints from the search
for direct Higgs production over a wide Higgs mass range. Within this model,
compatible with the present experimental constraints on direct Higgs searches,
we demonstrate that the Higgs () production via a heavy vector-like
top-partner () decay, , , allows to
discover a Higgs boson at the LHC and measure its mass, through the decay
channels or . We also comment on the recent hint
in LHC data from a possible GeV Higgs scalar, in the presence of
heavy vector-like top quarks.Comment: 14 pages, 8 figure
Forming and preserving aragonite in shear zones: First report of blueschist facies metamorphism in the Jabal Akhdar Dome, Oman Mountains
We report the first occurrence of high-pressure metamorphic aragonite in Precambrian
carbonates of the Jabal Akhdar Dome in the Oman Mountains (northern Oman). We propose
a model for both its formation at blueschist facies conditions and its subsequent preservation
to the surface within the tectonic framework of the Late Cretaceous obduction of
the Semail Ophiolite. Aragonite formed at temperature ∼350 °C and pressure ≥0.9 GPa and
is preserved within mylonitic shear zones and in stretched-fiber dilational veins where the
necessary conditions for its formation and preservation, such as plastic strain accommodation,
fluid-enhanced mineralogical reactions, and an anisotropic permeability structure, were
preferentially met with respect to the surrounding rock. High-strain structural domains are
ideal sites to look for and study prograde and retrograde high-pressure metamorphic histories
in deeply subducted and exhumed terrains
A geology-based 3D velocity model of the Amatrice Basin (Central Italy)
In this paper we present a new methodological approach which integrates geological and geophysical data into a 3D modelling process to be mainly employed in seismic hazard assessment studies of earthquake-prone areas around the world, as well as in applications for land use and urban planning. As a case study, the reconstruction of a geology-based 3D velocity model of the uppermost hundreds of metres of the Amatrice high-seismic-hazard area is described.
The model was constructed using geological (e.g., maps, cross-sections and core-wells) and geophysical (e.g., down-hole, MASW, refraction, and seismic noise measurements) data, which were georeferenced and uploaded into 3D geological modelling software, where faults, stratigraphic boundaries, and geophysical attributes were digitised, checked, hierarchised, and modelled. The performed 3D geological model was parameterised with Vs and Vp velocities and, finally, the environmental noise (i.e., horizontal-to-vertical spectral ratio analysis, HVSR) recorded at some seismic stations was compared with the seismic responses modelled at some nearby control points.
In the study area, the proposed geology-based 3D velocity model represents both a new potential geophysical prediction tool for areas devoid of geophysical measurements (i.e. HVSR curves) and a potential input-model for future ground-motion and seismic-wave-propagation simulations aimed at a more precise local seismic response assessment and, consequently, at the development of more realistic seismic hazard scenarios.
The model here presented constitutes a first version of the 3D geological-geophysical model for the studied area, which will be improved with new data and more advanced algorithms available in the future
Bounding wide composite vector resonances at the LHC
In composite Higgs models (CHMs), electroweak precision data generically push
colourless composite vector resonances to a regime where they dominantly decay
into pairs of light top partners. This greatly attenuates their traces in
canonical collider searches, tailored for narrow resonances promptly decaying
into Standard Model final states. By reinterpreting the CMS same-sign dilepton
(SS2) analysis at the Large Hadron Collider (LHC), originally designed to
search for top partners with electric charge , we demonstrate its
significant coverage over this kinematical regime. We also show the reach of
the 13 TeV run of the LHC, with various integrated luminosity options, for a
possible upgrade of the SS2 search. The top sector of CHMs is found to be
more fine-tuned in the presence of colourless composite resonances in the few
TeV range.Comment: 9 pages, 5 figures. Minor corrections for publication in JHE
ATLAS Z Excess in Minimal Supersymmetric Standard Model
Recently the ATLAS collaboration reported a 3 sigma excess in the search for
the events containing a dilepton pair from a Z boson and large missing
transverse energy. Although the excess is not sufficiently significant yet, it
is quite tempting to explain this excess by a well-motivated model beyond the
standard model. In this paper we study a possibility of the minimal
supersymmetric standard model (MSSM) for this excess. Especially, we focus on
the MSSM spectrum where the sfermions are heavier than the gauginos and
Higgsinos. We show that the excess can be explained by the reasonable MSSM mass
spectrum.Comment: 13 pages, 7 figures; published versio
Erythromycin-resistant lactic acid bacteria in the healthy gut of vegans, ovo-lacto vegetarians and omnivores
Diet can affect the diversity and composition of gut microbiota. Usage of antibiotics in food production and in human or veterinary medicine has resulted in the emergence of commensal antibiotic resistant bacteria in the human gut. The incidence of erythromycin-resistant lactic acid bacteria (LAB) in the feces of healthy vegans, ovo-lacto vegetarians and omnivores was analyzed. Overall, 155 LAB were isolated and characterized for their phenotypic and genotypic resistance to erythromycin. The isolates belonged to 11 different species within the Enterococcus and Streptococcus genera. Enterococcus faecium was the dominant species in isolates from all the dietary categories. Only 97 out of 155 isolates were resistant to erythromycin after Minimum Inhibitory Concentration (MIC) determination; among them, 19 isolates (7 from vegans, 4 from ovo-lacto vegetarians and 8 from omnivores) carried the erm(B) gene. The copresence of erm(B) and erm(A) genes was only observed in Enterococcus avium from omnivores. Moreover, the transferability of erythromycin resistance genes using multidrug-resistant (MDR) cultures selected from the three groups was assessed, and four out of six isolates were able to transfer the erm(B) gene. Overall, isolates obtained from the omnivore samples showed resistance to a greater number of antibiotics and carried more tested antibiotic resistance genes compared to the isolates from ovo-lacto vegetarians and vegans. In conclusion, our results show that diet does not significantly affect the occurrence of erythromycin-resistant bacteria and that commensal strains may act as a reservoir of antibiotic resistance (AR) genes and as a source of antibiotic resistance spreading
New Higgs Production Mechanism in Composite Higgs Models
Composite Higgs models are only now starting to be probed at the Large Hadron
Collider by Higgs searches. We point out that new resonances, abundant in these
models, can mediate new production mechanisms for the composite Higgs. The new
channels involve the exchange of a massive color octet and single production of
new fermion resonances with subsequent decays into the Higgs and a Standard
Model quark. The sizable cross section and very distinctive kinematics allow
for a very clean extraction of the signal over the background with high
statistical significance. Heavy gluon masses up to 2.8 TeV can be probed with
data collected during 2012 and up to 5 TeV after the energy upgrade to
TeV.Comment: 27 pages, 22 figures. V2: typos corrected, matches published versio
Physics at a 100 TeV pp collider: beyond the Standard Model phenomena
This report summarises the physics opportunities in the search and study of
physics beyond the Standard Model at a 100 TeV pp collider.Comment: 196 pages, 114 figures. Chapter 3 of the "Physics at the FCC-hh"
Repor
Higgs Low-Energy Theorem (and its corrections) in Composite Models
The Higgs low-energy theorem gives a simple and elegant way to estimate the
couplings of the Higgs boson to massless gluons and photons induced by loops of
heavy particles. We extend this theorem to take into account possible nonlinear
Higgs interactions resulting from a strong dynamics at the origin of the
breaking of the electroweak symmetry. We show that, while it approximates with
an accuracy of order a few percents single Higgs production, it receives
corrections of order 50% for double Higgs production. A full one-loop
computation of the gg->hh cross section is explicitly performed in MCHM5, the
minimal composite Higgs model based on the SO(5)/SO(4) coset with the Standard
Model fermions embedded into the fundamental representation of SO(5). In
particular we take into account the contributions of all fermionic resonances,
which give sizeable (negative) corrections to the result obtained considering
only the Higgs nonlinearities. Constraints from electroweak precision and
flavor data on the top partners are analyzed in detail, as well as direct
searches at the LHC for these new fermions called to play a crucial role in the
electroweak symmetry breaking dynamics.Comment: 30 pages + appendices and references, 12 figures. v2: discussion of
flavor constraints improved; references added; electroweak fit updated,
results unchanged. Matches published versio
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