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 $X_{\rm 1}$ directly, other observables closely linked to $X_{\rm 1}$ 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 $X_{\rm 1}$ is the depth of shower maximum $X_{\rm max}$. We will discuss the sensitivity of an $X_{\rm max}$-based analysis on $\sigma_{\rm p-air}$ 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