155 research outputs found
The Higgs System in and Beyond the Standard Model
After the discovery of the Higgs boson particle on the 4th of July of 2012 at
the Large Hadron Collider, sited at the european CERN laboratory, we are
entering in a fascinating period for Particle Physics where both theorists and
experimentalists are devoted to fully understand the features of this new
particle and the possible consequences for High Energy Physics of the Higgs
system both within and beyond the Standard Model of fundamental particle
interactions. This paper is a summary of the lectures given at the third IDPASC
school (Santiago de Compostela, Feb. 2013, Spain) addressed to PhD students,
and contains a short introduction to the main basic aspects of the Higgs boson
particle in and beyond the Standard Model.Comment: 62 pages, 31 figures, Lectures of the IDPASC School at Santiago de
Compostela, Spain, February 201
Analytic Results for Higgs Production in Bottom Fusion
We evaluate analytically the cross section for Higgs production plus one jet
through bottom quark fusion. By considering the small pT limit we derive
expressions for the resummation coefficients governing the structure of large
logarithms, and compare these expressions with those available in the
literature.Comment: 14 pages, 7 figure
Diffractive Higgs Production by AdS Pomeron Fusion
The double diffractive Higgs production at central rapidity is formulated in
terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower,
Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple
self-consistent holographic framework capable of providing phenomenologically
compelling estimates of diffractive cross sections at the LHC. As in the
traditional weak coupling approach, we anticipate that several phenomenological
parameters must be tested and calibrated through factorization for a
self-consistent description of other diffractive process such as total cross
sections, deep inelastic scattering and heavy quark production in the central
region.Comment: 53 pages, 8 figure
Constraining parameter space in type-II two-Higgs doublet model in light of a 126 GeV Higgs boson
We explore the implications of a 126 GeV Higgs boson indicated by the recent
LHC results for two-Higgs doublet model (2HDM). Identifying the 126 GeV Higgs
boson as either the lighter or heavier of CP even neutral Higgs bosons in 2HDM,
we examine how the masses of Higgs fields and mixing parameters can be
constrained by the theoretical conditions and experimental constraints. The
theoretical conditions taken into account are the vacuum stability,
perturbativity and unitarity required to be satisfied up to a cut-off scale. We
also show how bounds on the masses of Higgs bosons and mixing parameters depend
on the cut-off scale. In addition, we investigate whether the allowed regions
of parameter space can accommodate particularly the enhanced di-photon signals,
ZZ* and WW* decay modes of the Higgs boson, and examine the prediction of the
signal strength of Z{\gamma} decay mode for the allowed regions of the
parameter space.Comment: To be published in JHEP, 20 pages, 11 figures, Figures and results
are updated for the recent LHC result
Supersymmetric Higgs Yukawa Couplings to Bottom Quarks at next-to-next-to-leading Order
The effective bottom Yukawa couplings are analyzed for the minimal
supersymmetric extension of the Standard Model at two-loop accuracy within
SUSY-QCD. They include the resummation of the dominant corrections for large
values of tg(beta). In particular the two-loop SUSY-QCD corrections to the
leading SUSY-QCD and top-induced SUSY-electroweak contributions are addressed.
The residual theoretical uncertainties range at the per-cent level.Comment: 25 pages, 9 figures, added comments and references, typos corrected,
results unchanged, published versio
Spontaneous Symmetry Probing
For relativistic quantum field theories, we consider Lorentz breaking,
spatially homogeneous field configurations or states that evolve in time along
a symmetry direction. We dub this situation "spontaneous symmetry probing"
(SSP). We mainly focus on internal symmetries, i.e. on symmetries that commute
with the Poincare group. We prove that the fluctuations around SSP states have
a Lagrangian that is explicitly time independent, and we provide the field
space parameterization that makes this manifest. We show that there is always a
gapless Goldstone excitation that perturbs the system in the direction of
motion in field space. Perhaps more interestingly, we show that if such a
direction is part of a non-Abelian group of symmetries, the Goldstone bosons
associated with spontaneously broken generators that do not commute with the
SSP one acquire a gap, proportional to the SSP state's "speed". We outline
possible applications of this formalism to inflationary cosmology.Comment: 31 page
NLL+NNLO predictions for jet-veto efficiencies in Higgs-boson and Drell-Yan production
Using the technology of the CAESAR approach to resummation, we examine the
jet-veto efficiency in Higgs-boson and Drell-Yan production at hadron colliders
and show that at next-to-leading logarithmic (NLL) accuracy the resummation
reduces to just a Sudakov form factor. Matching with NNLO calculations results
in stable predictions for the case of Drell-Yan production, but reveals
substantial uncertainties in gluon-fusion Higgs production, connected in part
with the poor behaviour of the perturbative series for the total cross section.
We compare our results to those from POWHEG with and without reweighting by
HqT, as used experimentally, and observe acceptable agreement. In an appendix
we derive the part of the NNLL resummation corrections associated with the
radius dependence of the jet algorithm.Comment: 30 pages, 8 figures; v2 as published in JHE
The Healthy Steps Study: A randomized controlled trial of a pedometer-based Green Prescription for older adults. Trial protocol
Background: Graded health benefits of physical activity have been demonstrated for the reduction of coronary heart disease, some cancers, and type-2 diabetes, and for injury reduction and improvements in mental health. Older adults are particularly at risk of physical inactivity, and would greatly benefit from successful targeted physical activity interventions. Methods/Design: The Healthy Steps study is a 12-month randomized controlled trial comparing the efficacy of a pedometer-based Green Prescription with the conventional time-based Green Prescription in increasing and maintaining physical activity levels in low-active adults over 65 years of age. The Green Prescription interventions involve a primary care physical activity prescription with 3 follow-up telephone counselling sessions delivered by trained physical activity counsellors over 3 months. Those in the pedometer group received a pedometer and counselling based around increasing steps that can be monitored on the pedometer, while those in the standard Green Prescription group received counselling using time-based goals. Baseline, 3 month (end of intervention), and 12 month measures were assessed in face-to-face home visits with outcomes measures being physical activity (Auckland Heart Study Physical Activity Questionnaire), quality of life (SF-36 and EQ-5D), depressive symptoms (Geriatric Depression Scale), blood pressure, weight status, functional status (gait speed, chair stands, and tandem balance test) and falls and adverse events (self-report). Utilisation of health services was assessed for the economic evaluation carried out alongside this trial. As well, a process evaluation of the interventions and an examination of barriers and motives for physical activity in the sample were conducted. The perceptions of primary care physicians in relation to delivering physical activity counselling were also assessed. Discussion: The findings from the Healthy Steps trial are due in late 2009. If successful in improving physical activity in older adults, the pedometer-based Green Prescription could assist in reducing utilisation of health services and improve cardiovascular health and reduction of risk for a range of non-communicable lifestyles diseases
The Minimal Scale Invariant Extension of the Standard Model
We perform a systematic analysis of an extension of the Standard Model that
includes a complex singlet scalar field and is scale invariant at the tree
level. We call such a model the Minimal Scale Invariant extension of the
Standard Model (MSISM). The tree-level scale invariance of the model is
explicitly broken by quantum corrections, which can trigger electroweak
symmetry breaking and potentially provide a mechanism for solving the gauge
hierarchy problem. Even though the scale invariant Standard Model is not a
realistic scenario, the addition of a complex singlet scalar field may result
in a perturbative and phenomenologically viable theory. We present a complete
classification of the flat directions which may occur in the classical scalar
potential of the MSISM. After calculating the one-loop effective potential of
the MSISM, we investigate a number of representative scenarios and determine
their scalar boson mass spectra, as well as their perturbatively allowed
parameter space compatible with electroweak precision data. We discuss the
phenomenological implications of these scenarios, in particular, whether they
realize explicit or spontaneous CP violation, neutrino masses or provide dark
matter candidates. In particular, we find a new minimal scale-invariant model
of maximal spontaneous CP violation which can stay perturbative up to
Planck-mass energy scales, without introducing an unnaturally large hierarchy
in the scalar-potential couplings.Comment: 71 pages, 34 eps figures, numerical error corrected, clarifying
comments adde
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