751 research outputs found
Hints of Standard Model Higgs Boson at the LHC and Light Dark Matter Searches
The most recent results of searches at the LHC for the Higgs boson h have
turned up possible hints of such a particle with mass m_h about 125 GeV
consistent with standard model (SM) expectations. This has many potential
implications for the SM and beyond. We consider some of them in the contexts of
a simple Higgs-portal dark matter (DM) model, the SM plus a real gauge-singlet
scalar field D as the DM candidate, and a couple of its variations. In the
simplest model with one Higgs doublet and three or four generations of
fermions, for D mass m_D DD tends to have a
substantial branching ratio. If future LHC data confirm the preliminary Higgs
indications, m_D will have to exceed m_h/2. To keep the DM lighter than m_h/2,
one will need to extend the model and also satisfy constraints from DM direct
searches. The latter can be accommodated if the model provides sizable isospin
violation in the DM-nucleon interactions. We explore this in a
two-Higgs-doublet model combined with the scalar field D. This model can offer
a 125-GeV SM-like Higgs and a light DM candidate having isospin-violating
interactions with nucleons at roughly the required level, albeit with some
degree of fine-tuning.Comment: 17 pages, 4 figures, slightly revised, main conclusions unchanged,
references added, matches published versio
Dome Down Laparoscopic Cholecystectomy: Our Experience and the State of Art
Introduction: Laparoscopic Cholecystectomy is nowadays the gold standard technique for
benign gallbladder disease both in elective and emergency surgery. But it is even true that in very
acute cholecystitis when the tissues are inflamed and the anatomy can be difficult to recognize, the
classic laparoscopic approach can lead to biliary and vascular injuries. Dome down laparoscopic
approach can be used to avoid conversion to open surgery and decrease surgical complications.
Methods: A retrospective record of all Cholecystectomy carried out in our unit by experienced
surgeons from January 2013 to August 2017 was examined. Cases were divided by surgical
technique: Classical laparoscopic technique, Open cholecystectomy, Laparoscopic converted to
open cholecystectomy, Dome down laparoscopic Cholecystectomy (DDLC). A systematic literature
search was performed using PubMedz and Embase databases. The search was limited to studies
on humans and to those reported in the English language between January 2009 and December
2016.
Results and discussion: 194 cholecystectomy were performed, among these 163 with
laparoscopic technique and 3% of all laparoscopic approached cholecystectomy were performed
as DDLC. The mean hospital stay was 5 days (2-11). 1 out of 5 patients needed postoperatory
ERCP and endobiliary stent was positioned removed in 30 days with no other complications.
Other 4 patients were evaluated after 1 week from dismission with no evidence of postoperative
complications.
Conclusion: Dome down cholecystectomy is a feasible and safe procedure; it avoids biliary
and vascular injuries in difficult cholecystectomy. It can still be improved by the combination
with ultrasonic devices or with new surgical techniques such as Single-incision Laparoscopic
cholecistectomy
A narrative review about difficult laparoscopic cholecystectomy: technical tips
Background: Laparoscopic cholecystectomy (LC) is the most practiced procedure in general surgery worldwide. It is nowadays the optimum surgical procedure for symptomatic gallbladder lithiasis. Nevertheless, it should not be underestimated since vascular and biliary duct injuries are not uncommon, with devastating consequences. This study aimed to advise the best surgical technical approach for LC according to the intraoperative situation to avoid accidental anatomical structures injuries. Methods: A traditional narrative literature search for articles published up to December 2021 was performed using the most common search engines (PubMed, Web of Science, Google Scholar). The search strategy utilized in all databases included the combination of the keywords: "laparoscopic cholecystectomy", "difficult cholecystectomy", "acute cholecystitis", "prevention bile duct injuries", "safe cholecystectomy". No restrictions were applied to the language of the publication if an English version of the article was available. Key Content and Findings: Difficult laparoscopic cholecystectomy (DLC) is a distressing condition. Its definition is not well established and may vary according to the surgeon's experience. Several techniques have been proposed to minimize the bile duct or hepatic injury risk during the challenging cholecystectomy. Conclusions: Although LC is nowadays the optimum surgical procedure for symptomatic gallbladder lithiasis, it should not be underestimated since vascular and biliary duct injuries are very morbid, significantly increase care costs, and often lead to litigations
Inert-Sterile Neutrino: Cold or Warm Dark Matter Candidate
In usual particle models, sterile neutrinos can account for the dark matter
of the Universe only if they have masses in the keV range and are warm dark
matter. Stringent cosmological and astrophysical bounds, in particular imposed
by X-ray observations, apply to them. We point out that in a particular
variation of the inert doublet model, sterile neutrinos can account for the
dark matter in the Universe and may be either cold or warm dark matter
candidates, even for masses much larger than the keV range. These Inert-Sterile
neutrinos, produced non-thermally in the early Universe, would be stable and
have very small couplings to Standard Model particles, rendering very difficult
their detection in either direct or indirect dark matter searches. They could
be, in principle, revealed in colliders by discovering other particles in the
model.Comment: 10 pages, 5 figures; version 2: small changes in the text and
references adde
Relevance of Ion-Channeling for Direct DM Detection
The channeling of the recoiling nucleus in crystalline detectors after a WIMP
collision would produce a larger scintillation or ionization signal in direct
detection experiments than otherwise expected. I present estimates of the
importance of this effect for the total direct detection rate and the daily
modulation of the signal using analytic models produced in the 1960's and 70's
to describe the effects of channeling and blocking in crystals.Comment: Talk given at the TAUP 2009 conference, Rome, Italy, July 1-5 2009. 3
pages, 4 figures. jpconf.cls and jpconf11.clo files need to typeset the tex
fil
Anomaly mediated SUSY breaking scenarios in the light of cosmology and in the dark (matter)
Anomaly mediation is a popular and well motivated supersymmetry breaking
scenario. Different possible detailed realisations of this set-up are studied
and actively searched for at colliders. Apart from limits coming from flavour,
low energy physics and direct collider searches, these models are usually
constrained by the requirement of reproducing the observations on dark matter
density in the universe. We reanalyse these bounds and in particular we focus
on the dark matter bounds both considering the standard cosmological model and
alternative cosmological scenarios. These scenarios do not change the
observable cosmology but relic dark matter density bounds strongly depend on
them. We consider few benchmark points excluded by standard cosmology dark
matter bounds and suggest that loosening the dark matter constraints is
necessary in order to avoid a too strong (cosmological) model dependence in the
limits that are obtained for these models. We also discuss briefly the
implications for phenomenology and in particular at the Large Hadron Collider.Comment: 37 pages, 20 figures, 1 tabl
Modeling Thermal Fluctuations: Phase Mixing and Percolation
We consider the nonequilibrium dynamics of a a real scalar field in a
degenerate double-well potential. The system is prepared in the lowest free
energy state in one of the wells and the dynamics is driven by the coupling of
the field to a thermal bath. Using a simple analytical model, based on the
subcritical bubbles method, we compute the fraction of the total volume which
fluctuates to the opposite phase as a function of the parameters of the
potential. Furthermore, we show how complete phase mixing, {\em i.e.} symmetry
restoration, is related to percolation, which is dynamically driven by domain
instability. Our method describes quantitatively recent results obtained by
numerical simulations, and is applicable to systems in the Ising universality
class.Comment: Latex, 7 pages, 2 postscript figures, submitted to PRL. Also
available at http://fnas08.fnal.gov
Decay of the Z Boson into Scalar Particles
In extensions of the standard model, light scalar particles are often
possible because of symmetry considerations. We study the decay of the Z boson
into such particles. In particular, we consider for illustration the scalar
sector of a recently proposed model of the 17-keV neutrino which satisfies all
laboratory, astrophysical, and cosmological constraints.Comment: 11 pages (2 figures, not included) (Revised, Oct 1992). Some
equations have been corrected and 1 figure has been eliminate
Measurement of the gluon PDF at small x with neutrino telescopes
We analyze the possibility that neutrino telescopes may provide an
experimental determination of the slope lambda of the gluon distribution in the
proton at momentum fractions x smaller than the accelerator reach. The method
is based on a linear relation between lambda and the spectral index (slope) of
the down-going atmospheric muon flux above 100 TeV, for which there is no
background. Considering the uncertainties in the charm production cross section
and in the cosmic ray composition, we estimate the error on the measurement of
lambda through this method, excluding the experimental error of the telescopes,
to be ~ +/- 0.2Comment: 16 pages with 16 figures - new version, comments added, same results
and figure
On the measurement of the proton-air cross section using longitudinal shower profiles
In this paper, we will discuss the prospects of deducing the proton-air cross
section from fluorescence telescope measurements of extensive air showers. As
it is not possible to observe the point of first interaction
directly, other observables closely linked to must be inferred from
the longitudinal profiles. This introduces a dependence on the models used to
describe the shower development. The most straightforward candidate for a good
correlation to is the depth of shower maximum . We
will discuss the sensitivity of an -based analysis on and quantify the systematic uncertainties arising from the model
dependence, parameters of the reconstruction method itself and a possible
non-proton contamination of the selected shower sample.Comment: 4 pages, Proceedings for ISVHECRI Weihei 200
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