3,873 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
The Triple Higgs Boson Self-Coupling at Future Linear e+e- Colliders Energies: ILC and CLIC
We analyzed the triple Higgs boson self-coupling at future
colliders energies, with the reactions . We evaluate the total cross-sections for both and ,
and calculate the total number of events considering the complete set of
Feynman diagrams at tree-level. We vary the triple coupling
within the range and +2. The numerical
computation is done for the energies expected to be available at a possible
Future Linear Collider with a center-of-mass energy and a luminosity 1000 . Our analysis is also extended to a
center-of-mass energy 3 and luminosities of 1000 and 5000
. We found that for the process , the
complete calculation differs only by 3% from the approximate calculation
, while for the process , the expected number of events, considering the decay products of both
and , is not enough to obtain an accurate determination of the triple Higgs
boson self-coupling.Comment: 19 pages, 12 figure
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
Does Magnetic Charge Imply a Massive Photon ?
In Abelian theories of monopoles the magnetic charge is required to be
enormous. Using the electric-magnetic duality of electromagnetism it is argued
that the existence of such a large, non-perturbative magnetic coupling should
lead to a phase transition where magnetic charge is permanently confined and
the photon becomes massive. The apparent masslessness of the photon could then
be used as an argument against the existence of such a large, non-perturbative
magnetic charge. Finally it is shown that even in the presence of this
dynamical mass generation the Cabbibo-Ferrari formulation of magnetic charge
gives a consistent theory.Comment: 10 pages LaTe
Probing the Higgs mechanism via
We investigate the sensitivity of the reaction to
the Higgs sector based on the complete one-loop corrections in the minimal
Standard Model and the gauged non-linear -model. While this sensitivity
is very strong for the suppressed cross-section of equally polarized photons
and longitudinal W bosons, it is only marginal for the dominant mode of
transverse polarizations. The corrections within the -model turn out to
be UV-finite in accordance with the absence of \log\MH terms in the Standard
Model with a heavy Higgs boson.Comment: 12 pages uuencoded postscrip
Observation of Leggett's collective mode in a multi-band MgB2 superconductor
We report observation of Leggett's collective mode in a multi-band MgB2
superconductor with T_c=39K arising from the fluctuations in the relative phase
between two superconducting condensates. The novel mode is observed by Raman
spectroscopy at 9.4 meV in the fully symmetric scattering channel. The observed
mode frequency is consistent with theoretical considerations based on the first
principle computations.Comment: Accepted for PR
The mediating role of comorbid conditions in the association between type 2 diabetes and cognition: a cross-sectional observational study using the UK Biobank cohort
Aims: Using the UK Biobank cohort, a large sample of middle aged and older adults in the UK, the present study aimed to examine the cross-sectional association between type 2 diabetes and cognition and to assess the hypothesised mediating role of common comorbid conditions, whilst controlling for important demographic and lifestyle factors.
Methods: Using regression models and general structural equation models, we examined the cross-sectional association between type 2 diabetes status and: fluid intelligence; reaction time; visual memory; digit span and prospective memory; and the hypothesised mediating role of common comorbid conditions: visceral obesity; sleep problems; macrovascular problems; respiratory problems,; cancer and depressive symptoms in 47,468 participants from the UK Biobank cohort, of whom 1,831 have type 2 diabetes. We controlled for ethnicity, sex, age, deprivation, smoking status, alcohol consumption, physical activity levels and use of diabetes medication.
Results: Participants with type 2 diabetes had a significantly shorter digit span, b = -0.14, 99.2% CIs [-0.27, -0.11] than those without type 2 diabetes. Those with type 2 diabetes did not differ from those without type 2 diabetes on fluid intelligence, reaction time, visual memory and prospective memory. The associations that do exist between type 2 diabetes and cognition are consistently mediated via macrovascular problems, depressive symptoms, and to a lesser extent visceral obesity. Respiratory problems, sleep disturbances and cancer did not mediate the association between type 2 diabetes status and measures of cognition.
Conclusions: Comorbid conditions explain some of the observed association between type 2 diabetes and cognitive deficits. This suggests that prevention, management or treatment of these comorbid conditions may be important to reduce the likelihood of cognitive decline. Treatment studies with long follow-ups are needed to examine this.
Tweet: Comorbid conditions explain the association between type 2 diabetes and cognitive deficits. Prevention, management or treatment of these comorbid conditions may prevent or delay the onset of cognitive decline in people with type 2 diabetes
Glassy transition in a disordered model for the RNA secondary structure
We numerically study a disordered model for the RNA secondary structure and
we find that it undergoes a phase transition, with a breaking of the replica
symmetry in the low temperature region (like in spin glasses). Our results are
based on the exact evaluation of the partition function.Comment: 4 pages, 3 figure
On the detectability of the CMSSM light Higgs boson at the Tevatron
We examine the prospects of detecting the light Higgs h^0 of the Constrained
MSSM at the Tevatron. To this end we explore the CMSSM parameter space with
\mu>0, using a Markov Chain Monte Carlo technique, and apply all relevant
collider and cosmological constraints including their uncertainties, as well as
those of the Standard Model parameters. Taking 50 GeV < m_{1/2}, m_0 < 4 TeV,
|A_0| < 7 TeV and 2 < tan(beta) < 62 as flat priors and using the formalism of
Bayesian statistics we find that the 68% posterior probability region for the
h^0 mass lies between 115.4 GeV and 120.4 GeV. Otherwise, h^0 is very similar
to the Standard Model Higgs boson. Nevertheless, we point out some enhancements
in its couplings to bottom and tau pairs, ranging from a few per cent in most
of the CMSSM parameter space, up to several per cent in the favored region of
tan(beta)\sim 50 and the pseudoscalar Higgs mass of m_A\lsim 1 TeV. We also
find that the other Higgs bosons are typically heavier, although not
necessarily much heavier. For values of the h^0 mass within the 95% probability
range as determined by our analysis, a 95% CL exclusion limit can be set with
about 2/fb of integrated luminosity per experiment, or else with 4/fb (12/fb) a
3 sigma evidence (5 sigma discovery) will be guaranteed. We also emphasize that
the alternative statistical measure of the mean quality-of-fit favors a
somewhat lower Higgs mass range; this implies even more optimistic prospects
for the CMSSM light Higgs search than the more conservative Bayesian approach.
In conclusion, for the above CMSSM parameter ranges, especially m_0, either
some evidence will be found at the Tevatron for the light Higgs boson or, at a
high confidence level, the CMSSM will be ruled out.Comment: JHEP versio
- …