386 research outputs found
Asymmetric Dark Matter in the Sun and the Diphoton Excess at the LHC
It has been recently pointed out that a momentum-dependent coupling of the
asymmetric Dark Matter (ADM) with nucleons can explain the broad disagreement
between helioseismological observables and the predictions of standard solar
models. In this paper, we propose a minimal simplified ADM model consisting of
a scalar and a pseudoscalar mediator, in addition to a Dirac fermionic DM, for
generating such momentum-dependent interactions. Remarkably, the pseudoscalar
with mass around 750 GeV can simultaneously explain the solar anomaly and the
recent diphoton excess observed by both ATLAS and CMS experiments in the early
TeV LHC data. In this framework, the total width of the resonance
is naturally large, as suggested by the ATLAS experiment, since the resonance
mostly decays to the ADM pair. The model predicts the existence of a new light
scalar in the GeV range, interacting with quarks, and observable dijet, monojet
and signatures for the 750 GeV resonance at the LHC.Comment: 7 pages, 4 figures. Version to appear in PR
Flavour Covariant Formalism for Resonant Leptogenesis
We present a fully flavour-covariant formalism for transport phenomena and
apply it to study the flavour-dynamics of Resonant Leptogenesis (RL). We show
that this formalism provides a complete and unified description of RL,
consistently accounting for three distinct physical phenomena: (i) resonant
mixing and (ii) coherent oscillations between different heavy-neutrino
flavours, as well as (iii) quantum decoherence effects in the charged-lepton
sector. We describe the necessary emergence of higher-rank tensors in flavour
space, arising from the unitarity cuts of partial self-energies. Finally,
within a Resonant -Genesis model, we illustrate the importance of this
formalism by showing that the final lepton asymmetry can vary by as much as an
order of magnitude between partially flavour-dependent treatments, which do not
capture all of the pertinent flavour effects.Comment: 7 pages, 2 figures; numerical example revised; Contribution to the
Proceedings of the ICHEP 2014, Valencia, Spai
Kadanoff-Baym Approach to Flavour Mixing and Oscillations in Resonant Leptogenesis
We describe a loopwise perturbative truncation scheme for quantum transport
equations in the Kadanoff-Baym formalism, which does not necessitate the use of
the so-called Kadanoff-Baym or quasi-particle ansaetze for dressed propagators.
This truncation scheme is used to study flavour effects in the context of
Resonant Leptogenesis (RL), showing explicitly that, in the weakly-resonant
regime, there exist two distinct and pertinent flavour effects in the
heavy-neutrino sector: (i) the resonant mixing and (ii) the oscillations
between different heavy-neutrino flavours. Moreover, we illustrate that
Kadanoff-Baym and quasi-particle ansaetze, whilst appropriate for the
flavour-singlet dressed charged-lepton and Higgs propagators of the RL
scenario, should not be applied to the dressed heavy-neutrino propagators. The
use of these approximations for the latter is shown to capture only flavour
oscillations, whilst discarding the separate phenomenon of flavour mixing.Comment: 35 pages, 4 figures; further discussion added and typos corrected;
final published versio
Flavour Covariant Transport Equations: an Application to Resonant Leptogenesis
We present a fully flavour-covariant formalism for transport phenomena, by
deriving Markovian master equations that describe the time-evolution of
particle number densities in a statistical ensemble with arbitrary flavour
content. As an application of this general formalism, we study flavour effects
in a scenario of resonant leptogenesis (RL) and obtain the flavour-covariant
evolution equations for heavy-neutrino and lepton number densities. This
provides a complete and unified description of RL, capturing three distinct
physical phenomena: (i) the resonant mixing between the heavy-neutrino states,
(ii) coherent oscillations between different heavy-neutrino flavours, and (iii)
quantum decoherence effects in the charged-lepton sector. To illustrate the
importance of this formalism, we numerically solve the flavour-covariant rate
equations for a minimal RL model and show that the total lepton asymmetry can
be enhanced by up to one order of magnitude, as compared to that obtained from
flavour-diagonal or partially flavour off-diagonal rate equations. Thus, the
viable RL model parameter space is enlarged, thereby enhancing further the
prospects of probing a common origin of neutrino masses and the baryon
asymmetry in the Universe at the LHC, as well as in low-energy experiments
searching for lepton flavour and number violation. The key new ingredients in
our flavour-covariant formalism are rank-4 rate tensors, which are required for
the consistency of our flavour-mixing treatment, as shown by an explicit
calculation of the relevant transition amplitudes by generalizing the optical
theorem. We also provide a geometric and physical interpretation of the
heavy-neutrino degeneracy limits in the minimal RL scenario. Finally, we
comment on the consistency of various suggested forms for the heavy-neutrino
self-energy regulator in the lepton-number conserving limit.Comment: 109 pages, 14 figures, 5 tables; typos corrected; final published
versio
Distributed Leadership Agency and Work Outcomes: Validation of the Italian DLA and Its Relations With Commitment, Trust, and Satisfaction
Forms of collective leadership, such as distributed leadership, have become increasingly important. The need for measurement of the variables involved in the delegation processes represents a new challenge for organizations that want to ensure high-level working. The present study aimed to validate the Italian version of the distributed leadership agency (DLA). The study was carried out on 704 employees (doctors, nurses, clerks, staff workers, healthcare assistants, consultants, management) of an Italian public hospital, who were selected to complete a survey on organizational perceptions. Multiple confirmatory factor analyses (maximum likelihood) have been computed to explore the factorial structure of the DLA, along with associations with other work outcomes. Results about the Italian DLA confirmed the original trifactorial structure of the construct, suggested by Yukl (2002), through good fit indexes and reliability scores; moreover, consistent with the literature, DLA was strongly related to satisfaction, commitment, and trust. Results contribute to underline the robustness of the construct of DLA in different cultural sectors and provide a useful tool to be adopted in the Italian context
Left atrial trajectory impairment in hypertrophic cardiomyopathy disclosed by geometric morphometrics and parallel transport
The analysis of full Left Atrium (LA) deformation and whole LA deformational trajectory in time has been poorly investigated and, to the best of our knowledge, seldom discussed in patients with Hypertrophic Cardiomyopathy. Therefore, we considered 22 patients with Hypertrophic Cardiomyopathy (HCM) and 46 healthy subjects, investigated them by three-dimensional Speckle Tracking Echocardiography, and studied the derived landmark clouds via Geometric Morphometrics with Parallel Transport. Trajectory shape and trajectory size were different in Controls versus HCM and their classification powers had high AUC (Area Under the Receiving Operator Characteristic Curve) and accuracy. The two trajectories were much different at the transition between LA conduit and booster pump functions. Full shape and deformation analyses with trajectory analysis enabled a straightforward perception of pathophysiological consequences of HCM condition on LA functioning. It might be worthwhile to apply these techniques to look for novel pathophysiological approaches that may better define atrio-ventricular interaction
ADIPONECTIN, LEPTIN, RESISTIN LEVELS IN CYSTIC FIBROSIS ADOLESCENTS
INTRODUCTION: Patients with Cystic Fibrosis, especially in adolescence, could develop endocrine and metabolic complications, related to nutritional state and chronic inflammation. They develop a progressive decrease in lean body mass correlated with the progression of lung disease. Adipose tissue is involved as well and adipocytokines are a possible link between malnutrition and long term complications. PATIENTS AND METHODS: In 24 Cystic Fibrosis adolescents we studied auxological, nutritional, glycometabolic, endocrine patterns, together with leptin, adiponectin and resistin levels. We selected patients not affected by diabetes, insulin resistance, malnutrition, acute inflammatory states so as to avoid possible influences on the adipocytokines. RESULTS: All patients presented with an adequate BMI centile, with no statistically significant difference versus controls. HOMA IR and HOMA B% are in the normal range but lower than in controls, expression of a lower insulin-resistance with a lower insulin secretion. Leptin is significantly higher than in controls and maintains a correlation with BMI and gender. Resistin levels are more elevated in Cystic Fibrosis than in controls, with a statistically significant direct correlation with CRP (C-reactive protein) and insulinemia T0\u2019 and T120\u2019.Adiponectin is significantly higher in Cystic Fibrosis, inversely correlated with CRP and insulinemia and directly with cholesterol and HDL-cholesterol. CONCLUSIONS:The detection of adipocytokines levels could improve the metabolic follow-up of these patients: the maintenance of an adequate leptin gender difference is useful in the follow-up of puberty in adolescence. Adiponectin could be a marker of insulin sensitivity and prevent protein catabolism and loss of lean body mass. Resistin levels may be used as a marker of insulin resistance and may indicate the severity of chronic inflammation. This is the first study available in literature about adiponectin levels in pediatric Cystic Fibrosis patients and about resistin in Cystic Fibrosis
A simple model of radiative emission in M87
We present a simple physical model of the central source emission in the M87
galaxy. It is well known that the observed X-ray luminosity from this galactic
nucleus is much lower than the predicted one, if a standard radiative
efficiency is assumed. Up to now the main model invoked to explain such a
luminosity is the ADAF (Advection-Dominated-Accretion-Flow) model. Our approach
supposes only a simple axis-symmetric adiabatic accretion with a low angular
momentum together with the bremsstrahlung emission process in the accreting
gas. With no other special hypothesis on the dynamics of the system, this model
agrees well enough with the luminosity value measured by Chandra.Comment: 11 pages, 6 figures, accepted for publication in The Astrophysical
Journa
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