76 research outputs found
Impacts of alcohol consumption by mothers and fathers, parental monitoring, adolescent disclosure and novelty-seeking behaviour on the likelihood of alcohol use and inebriation among adolescents
The aim of this prospective cohort study was to examine how alcohol consumption by mothers and fathers, parental monitoring (knowledge, control, and solicitation), adolescent disclosure and novelty seeking were associated with the likelihood of alcohol use and inebriation among adolescents in three different age groups (13â14 years, 14â15 years, and 17 years). The results showed that alcohol consumption by parents is of significance for adolescent alcohol consumption (odds ratio mothers: 1.47 [1.17â1.84], odds ratio fathers 1.33 [1.08â1.65]) and inebriation, especially in the 17-year-old age group. The results showed that novelty seeking was a strong risk factor in all three age groups, while parental control and knowledge had no impact. This study shows that parental solicitation increased the odds at age 17 for alcohol consumption (2.64 [1.02â6.83]) and inebriation, while adolescent disclosure decreased the odds (0.18 [0.05â0.68]). In summary, the study shows that parents should be particularly attentive to adolescents with high novelty-seeking behaviour and that parental alcohol consumption influences adolescent alcohol habits.publishedVersio
Effect of Synthesis on Quality, Electronic Properties and Environmental Stability of Individual Monolayer Ti\u3csub\u3e3\u3c/sub\u3eC\u3csub\u3e2\u3c/sub\u3e MXene Flakes
2D transition metal carbide Ti3C2Tx (T stands for surface termination), the most widely studied MXene, has shown outstanding electrochemical properties and promise for a number of bulk applications. However, electronic properties of individual MXene flakes, which are important for understanding the potential of these materials, remain largely unexplored. Herein, a modified synthetic method is reported for producing high-quality monolayer Ti3C2Tx flakes. Field-effect transistors (FETs) based on monolayer Ti3C2Tx flakes are fabricated and their electronic properties are measured. Individual Ti3C2Tx flakes exhibit a high conductivity of 4600 ± 1100 S cmâ1 and field-effect electron mobility of 2.6 ± 0.7 cm2 Vâ1 sâ1. The resistivity of multilayer Ti3C2Tx films is only one order of magnitude higher than the resistivity of individual flakes, which indicates a surprisingly good electron transport through the surface terminations of different flakes, unlike in many other 2D materials. Finally, the fabricated FETs are used to investigate the environmental stability and kinetics of oxidation of Ti3C2Tx flakes in humid air. The high-quality Ti3C2Tx flakes are reasonably stable and remain highly conductive even after their exposure to air for more than 24 h. It is demonstrated that after the initial exponential decay the conductivity of Ti3C2Tx flakes linearly decreases with time, which is consistent with their edge oxidation
Naturalness and Higgs Decays in the MSSM with a Singlet
The simplest extension of the supersymmetric standard model - the addition of
one singlet superfield - can have a profound impact on the Higgs and its
decays. We perform a general operator analysis of this scenario, focusing on
the phenomenologically distinct scenarios that can arise, and not restricting
the scope to the narrow framework of the NMSSM. We reexamine decays to four b
quarks and four tau's, finding that they are still generally viable, but at the
edge of LEP limits. We find a broad set of Higgs decay modes, some new,
including those with four gluon final states, as well as more general six and
eight parton final states. We find the phenomenology of these scenarios is
dramatically impacted by operators typically ignored, specifically those
arising from D-terms in the hidden sector, and those arising from weak-scale
colored fields. In addition to sensitivity of m_Z, there are potential tunings
of other aspects of the spectrum. In spite of this, these models can be very
natural, with light stops and a Higgs as light as 82 GeV. These scenarios
motivate further analyses of LEP data as well as studies of the detection
capabilities of future colliders to the new decay channels presented.Comment: 3 figures, 1 appendix; version to appear in JHEP; typos fixed and
additional references and acknowledgements adde
Next-to-leading Corrections to the Higgs Boson Transverse Momentum Spectrum in Gluon Fusion
We present a fully analytic calculation of the Higgs boson transverse
momentum and rapidity distributions, for nonzero Higgs , at
next-to-leading order in the infinite-top-mass approximation. We separate the
cross section into a part that contains the dominant soft, virtual, collinear,
and small--enhanced contributions, and the remainder, which is
organized by the contributions due to different parton helicities. We use this
cross section to investigate analytically the small- limit and compare
with the expectation from the resummation of large logarithms of the type
. We also compute numerically the cross section at moderate
where a fixed-order calculation is reliable. We find a -factor
that varies from , and a reduction in the scale dependence, as
compared to leading order. Our analysis suggests that the contribution of
current parton distributions to the total uncertainty on this cross section at
the LHC is probably less than that due to uncalculated higher orders.Comment: 40 pages, 10 figures, JHEP style (minor changes, added reference
Improved description of charged Higgs boson production at hadron colliders
We present a new method for matching the two twin-processes gb->H+/-t and
gg->H+/-tb in Monte Carlo event generators. The matching is done by defining a
double-counting term, which is used to generate events that are subtracted from
the sum of these two twin-processes. In this way we get a smooth transition
between the collinear region of phase space, which is best described by
gb->H+/-t, and the hard region, which requires the use of the gg->H+/-tb
process. The resulting differential distributions show large differences
compared to both the gb-> H+/-t and gg->H+/-tb processes illustrating the
necessity to use matching when tagging the accompanying b-jet.Comment: 21 pages, 9 figures. Revised with updated discussion and reference
Direct Higgs production and jet veto at the Tevatron and the LHC in NNLO QCD
We consider Higgs boson production through gluon--gluon fusion in hadron
collisions, when a veto is applied on the transverse momenta of the
accompanying hard jets. We compute the QCD radiative corrections to this
process at NLO and NNLO. The NLO calculation is complete. The NNLO calculation
uses the recently evaluated NNLO soft and virtual QCD contributions to the
inclusive cross section. We find that the jet veto reduces the impact of the
NLO and NNLO contributions, the reduction being more sizeable at the LHC than
at the Tevatron.Comment: 22 pages, 12 postscript figure
The Minimal Phantom Sector of the Standard Model: Higgs Phenomenology and Dirac Leptogenesis
We propose the minimal, lepton-number conserving, SU(3)xSU(2)xU(1)
gauge-singlet, or phantom, extension of the Standard Model. The extension is
natural in the sense that all couplings are of O(1) or forbidden due to a
phantom sector global U(1)_D symmetry, and basically imitates the standard
Majorana see-saw mechanism. Spontaneous breaking of the U(1)_D symmetry
triggers consistent electroweak gauge symmetry breaking only if it occurs at a
scale compatible with small Dirac neutrino masses and baryogenesis through
Dirac leptogenesis. Dirac leptogenesis proceeds through the usual
out-of-equilibrium decay scenario, leading to left and right-handed neutrino
asymmetries that do not fully equilibrate after they are produced. The model
contains two physical Higgs bosons and a massless Goldstone boson. The
existence of the Goldstone boson suppresses the Higgs to bb branching ratio and
instead the Higgs bosons will mainly decay to invisible Goldstone and/or to
visible vector boson pairs. In a representative scenario, we estimate that with
30 fb^-1 integrated luminosity, the LHC could discover this invisibly decaying
Higgs, with mass ~120 GeV. At the same time a significantly heavier, partner
Higgs boson with mass ~210 GeV could be found through its vector boson decays.
Electroweak constraints as well as astrophysical and cosmological implications
are analysed and discussed.Comment: 21 pages, 4 figures. Corrected typos and added references. To appear
in JHE
Neutralino relic density in supersymmetric GUTs with no-scale boundary conditions above the unification scale
We investigate SU(5) and SO(10) GUTs with vanishing scalar masses and
trilinear scalar couplings at a scale higher than the unification scale. The
parameter space of the models, further constrained by b-\tau Yukawa coupling
unification, consists of a common gaugino mass and of \tan\beta. We analyze the
low energy phenomenology, finding that A-pole annihilations of neutralinos
and/or coannihilations with the lightest stau drive the relic density within
the cosmologically preferred range in a significant region of the allowed
parameter space. Implications for neutralino direct detection and for CERN LHC
experiments are also discussed.Comment: 14 pages, 5 figures, JHEP style. Version accepted for publication in
JHE
Constraints on Supersymmetric Flavour Models from b->s gamma
We consider the effects of departures from minimal flavour violations (MFV)
in the context of CMSSM-like theories. Second and third generation off-diagonal
elements in the Yukawa, sfermion, and trilinear mass matrices are taken to be
non-zero at the GUT scale. These are run down together with MSSM parameters to
the electroweak scale. We apply constraints from fermion masses and CKM matrix
elements to limit the range of the new free parameters of the model. We
determine the effect of the departure from MFV on the branching ratio of b->s
gamma. We find that only when the expansion parameter in the down-squark sector
is relatively large there is a noticeable effect, which tends to relax the
lower limit from b->s gamma on the universal gaugino mass. We also find that
the expansion parameter associated with the slepton sector needs to be smaller
than the corresponding parameter in the down-squark sector in order to be
compliant with the bound imposed by the branching ratio of tau-> mu gamma.Comment: Comments: 43 pages, 14 figures. Version accepted for publication:
typos corrected, rewritten for better understanding and references adde
Sneutrino cold dark matter, a new analysis: relic abundance and detection rates
We perform a new and updated analysis of sneutrinos as dark matter
candidates, in different classes of supersymmetric models. We extend previous
analyses by studying sneutrino phenomenology for full variations of the
supersymmetric parameters which define the various models. We first revisit the
standard Minimal Supersymmetric Standard Model, concluding that sneutrinos are
marginally compatible with existing experimental bounds, including direct
detection, provided they compose a subdominant component of dark matter. We
then study supersymmetric models with the inclusion of right-handed fields and
lepton-number violating terms. Simple versions of the lepton-number-violating
models do not lead to phenomenology different from the standard case when the
neutrino mass bounds are properly included. On the contrary, models with
right-handed fields are perfectly viable: they predict sneutrinos which are
compatible with the current direct detection sensitivities, both as subdominant
and dominant dark matter components. We also study the indirect detection
signals for such successful models: predictions for antiproton, antideuteron
and gamma-ray fluxes are provided and compared with existing and future
experimental sensitivities. The neutrino flux from the center of the Earth is
also analyzed.Comment: 72 pages, 50 figures. The version on the archive has low-resolution
figures. The paper with high resolution figures may be found through
http://www.to.infn.it/~arina/papers or
http://www.to.infn.it/~fornengo/Research/paperlist.htm
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