Theoretical predictions for Higgs boson decay into four leptons.

After the discovery of the Higgs boson at the LHC, the precise determination of its properties and the search for Beyond the Standard Model (BSM) signals are two of the most important tasks in particle physics. The investigation of the Higgs sector relies on the comparison between theoretical predictions and experimental data. In order to compare the SM predictions with very precise data, the reduction of theoretical uncertainties is mandatory. This is the main motivation for the work presented in my Ph.D. dissertation. I have focused my attention on the Higgs boson decay into four charged leptons. In the thesis I detail the calculation of the full Next-to-Leading Order (NLO) electroweak corrections to Higgs boson decay into four charged leptons, by considering the gold-plated channel. The NLO corrections are matched with a QED Parton Shower (PS), in order to simulate exclusive multiple photon emission and provide novel results at NLOPS electroweak accuracy. I also provide some new results on the possible effects of new physics which have been obtained in an Effective Field Theory (EFT) framework

Higgs boson decay into four leptons at NLOPS electroweak accuracy

In view of precision studies of the Higgs sector at the Run II of the LHC, the improvement of the accuracy of the theoretical prediction is becoming a pressing issue. In this framework, we detail a calculation of the full Next-to-Leading Order (NLO) electroweak corrections to Higgs boson decay into four charged leptons, by considering the gold-plated channel H -> Z(*) Z(*) -> 2l 2l', l,l' = e, mu. We match the NLO corrections with a QED Parton Shower (PS), in order to simulate exclusive multiple photon emission and provide novel results at NLOPS electroweak accuracy. We compare our NLO predictions to those of the program Prophecy4f and present NLOPS phenomenological results relevant for Higgs physics studies, with particular attention to precision measurements of the Higgs boson mass, spin-parity assignment and tests of the Standard Model. Our calculation is implemented in a new code, Hto4l, which can be easily interfaced to any generator describing Higgs boson production. As an example, we provide illustrative results for Higgs production and decay in the process gg -> H -> 4l using POWHEG with NLOPS accuracy in the production mode.Comment: 27 pages, 2 tables, 9 figures. New numerical results and plots for dressed leptons. Conclusions unchanged. Version to appear in JHE

Prospects for the determination of the top-quark Yukawa coupling at future e+e−e^+e^- colliders

We estimate the sensitivity to the top-quark Yukawa coupling $y_t$ at future $e^+e^-$ colliders. We go beyond the standard approach that focuses on $t\bar t h$ production and consider final states with a Higgs boson but not top quarks. The sensitivity to $y_t$ in such processes comes from the coupling of the Higgs boson to top quarks in loops. Such final states can be produced in significant numbers at center-of-mass energies that will be accessible by all proposed $e^+e^-$ colliders. In a simplified theoretical framework to parametrise deviations from the Standard Model, we find that at FCC-$ee$ and CEPC operating at $\sqrt{s}=240$ GeV, $y_t$ could potentially be measured with precision better than $1\%$. For CLIC and ILC the extraction of $y_t$ could be improved by a factor of about 2 and 7 respectively, compared to its extraction from just $t\bar t h$ final states.Comment: 14 pages, 2 figures. v2 (published version): added references, extended discussio

Probing Quantum Confinement and Electronic Structure at Polar Oxide Interfaces

Polar discontinuities occurring at interfaces between two different materials constitute both a challenge and an opportunity in the study and application of a variety of devices. In order to cure the large electric field occurring in such structures, a reconfiguration of the charge landscape sets in at the interface via chemical modifications, adsorbates or charge transfer. In the latter case, one may expect a local electronic doping of one material: one sparkling example is the two-dimensional electron liquid (2DEL) appearing in SrTiO$_3$ once covered by a polar LaAlO$_3$ layer. Here we show that tuning the formal polarisation of a (La,Al)$_{1-x}$(Sr,Ti)$_x$O$_3$ (LASTO:$x$) overlayer through chemical composition modifies the quantum confinement of the 2DEL in SrTiO$_3$ and its electronic band structure. The analysis of the behaviour in magnetic field of superconducting field-effect devices reveals, in agreement with $ab\ initio$ calculations and self-consistent Poisson-Schr\"odinger modelling, that quantum confinement and energy splitting between electronic bands of different symmetries strongly depend on interface charge densities. These results not only strongly support the polar discontinuity mechanisms with a full charge transfer to explain the origin of the 2DEL at the celebrated LaAlO$_3$/SrTiO$_3$ interface, but also demonstrate an effective tool for tailoring the electronic structure at oxide interfaces.Comment: 18 pages, 4 figures, 1 ancillary file (Supporting Information

High sensitivity variable-temperature infrared nanoscopy of conducting oxide interfaces

Probing the local transport properties of two-dimensional electron systems (2DES) confined at buried interfaces requires a non-invasive technique with a high spatial resolution operating in a broad temperature range. In this paper, we investigate the scattering-type scanning near field optical microscopy as a tool for studying the conducting LaAlO3/SrTiO3 interface from room temperature down to 6 K. We show that the near-field optical signal, in particular its phase component, is highly sensitive to the transport properties of the electron system present at the interface. Our modelling reveals that such sensitivity originates from the interaction of the AFM tip with coupled plasmon-phonon modes with a small penetration depth. The model allows us to quantitatively correlate changes in the optical signal with the variation of the 2DES transport properties induced by cooling and by electrostatic gating. To probe the spatial resolution of the technique, we image conducting nano-channels written in insulating heterostructures with a voltage-biased tip of an atomic force microscope.Comment: 19 pages, 5 figure

Artificial quantum confinement in LAO3/STO heterostructure

Heterostructures of transition metal oxides (TMO) perovskites represent an ideal platform to explore exotic phenomena involving the complex interplay between the spin, charge, orbital and lattice degrees of freedom available in these compounds. At the interface between such materials, this interplay can lead to phenomena that are present in none of the original constituents such as the formation of the interfacial 2D electron system (2DES) discovered at the LAO3/STO3 (LAO/STO) interface. In samples prepared by growing a LAO layer onto a STO substrate, the 2DES is confined in a band bending potential well, whose width is set by the interface charge density and the STO dielectric properties, and determines the electronic band structure. Growing LAO (2 nm) /STO (x nm)/LAO (2 nm) heterostructures on STO substrates allows us to control the extension of the confining potential of the top 2DES via the thickness of the STO layer. In such samples, we explore the dependence of the electronic structure on the width of the confining potential using soft X-ray ARPES combined with ab-initio calculations. The results indicate that varying the thickness of the STO film modifies the quantization of the 3d t2g bands and, interestingly, redistributes the charge between the dxy and dxz/dyz bands

Bronchogenic cyst of the ileal mesentery: a case report and a review of literature

<p>Abstract</p> <p>Introduction</p> <p>Bronchogenic cyst is a rare clinical entity that occurs due to abnormal development of the foregut; the majority of bronchogenic cysts have been described in the mediastinum and they are rarely found in an extrathoracic location.</p> <p>Case presentation</p> <p>We describe the case of an intra-abdominal bronchogenic cyst of the mesentery, incidentally discovered during an emergency laparotomy for a perforated gastric ulcer in a 33-year-old Caucasian man.</p> <p>Conclusions</p> <p>Bronchogenic cyst should be considered in the differential diagnosis of subdiaphragmatic masses, even in an intraperitoneal location.</p

Reducing Nitrate Accumulation and Fertilizer Use in Lettuce with Modified Intermittent Nutrient Film Technique (NFT) System

Lettuce (Lactuca sativa L.) is a leading greenhouse-grown vegetable. However, nitrate (NO3) accumulation in leaves remains a major issue. The aims of this research were: (i) to test the modified intermittent Nutrient Film Technique (NFT) in the cultivation of soilless lettuce in which plants are grown on peat blocks in trays and supplied with an intermittent flow of nutrient solution, and (ii) to calibrate the fertilization scheme to increase yield performance, while keeping NO3 concentration under control. Two greenhouse trials were performed between autumn 2013 and spring 2014. Results showed that a 30-day cycle is the optimum duration in terms of fresh biomass yield, both for autumn and spring cultivation. Reducing N fertilization in the last cropping days never aected NO3 concentration in leaves during autumn trial, due to unfavourable growing conditions. Conversely, suspension of fertilization 2 days before harvest had a consistent eect during the spring trial, when NO3 concentration in leaves was highly reduced (from 20 to 36%) without yield penalties. Thus, suspending fertilization 2\u20134 days before harvesting in intermittent NFT may reduce, on average, NO3 accumulation by 29\u201358% and the fertilization rate by 7\u201316%, respectively. Yet, growing conditions are crucial to make this system eective

Ilioinguinal nerve neurectomy is better than preservation in lichtenstein hernia repair. A systematic literature review and meta-analysis

Objective This study aimed to evaluate the incidence of chronic groin pain (primary outcome) and alterations of sensitivity (secondary outcome) after Lichtenstein inguinal hernia repair, comparing neurectomy with ilioinguinal nerve preservation surgery. Summary background data The exact cause of chronic groin postoperative pain after mesh inguinal hernia repair is usually unclear. Section of the ilioinguinal nerve (neurectomy) may reduce postoperative chronic pain. Methods We followed PRISMA guidelines to identify randomized studies reporting comparative outcomes of neurectomy versus ilioinguinal nerve preservation surgery during Lichtenstein hernia repairs. Studies were identified by searching in PubMed, Scopus, and Web of Science from April 2020. The protocol for this systematic review and meta-analysis was submitted and accepted from PROSPERO: CRD420201610. Results In this systematic review and meta-analysis, 16 RCTs were included and 1550 patients were evaluated: 756 patients underwent neurectomy (neurectomy group) vs 794 patients underwent ilioinguinal nerve preservation surgery (nerve preser- vation group). All included studies analyzed Lichtenstein hernia repair. The majority of the new studies and data comes from a relatively narrow geographic region; other bias of this meta-analysis is the suitability of pooling data for many of these studies. A statistically significant percentage of patients with prosthetic inguinal hernia repair had reduced groin pain a 6 months after surgery at 8.94% (38/425) in the neurectomy group versus 25.11% (113/450) in the nerve preservatio group [relative risk (RR) 0.39, 95% confidence interval (CI) 0.28–0.54; Z = 5.60 (P 0.00001)]. Neurectomy did no significantly increase the groin paresthesia 6 months after surgery at 8.5% (30/353) in the neurectomy group versu 4.5% (17/373) in the nerve preservation group [RR 1.62, 95% CI 0.94–2.80; Z = 1.74 (P = 0.08)]. At 12 months afte surgery, there is no advantage of neurectomy over chronic groin pain; no significant differences were found in th 12-month postoperative groin pain rate at 9% (9/100) in the neurectomy group versus 17.85% (20/112) in the inguina nerve preservation group [RR 0.50, 95% CI 0.24–1.05; Z = 1.83 (P = 0.07)]. One study (115 patients) reported dat about paresthesia at 12 months after surgery (7.27%, 4/55 in neurectomy group vs. 5%, 3/60 in nerve preservatio group) and results were not significantly different between the two groups [RR 1.45, 95% CI 0.34, 6.21;Z = 0.5 (P = 0.61)]. The subgroup analysis of the studies that identified the IIN showed a significant reduction of the 6th mont evaluation of pain in both groups and confirmed the same trend in favor of neurectomy reported in the previous overal analysis: statistically significant reduction of pain 6 months after surgery at 3.79% (6/158) in the neurectomy grou versus 14.6% (26/178) in the nerve preservation group [RR 0.28, 95% CI 0.13–0.63; Z = 3.10 (P = 0.002)]. Conclusion Ilioinguinal nerve identification in Lichtenstein inguinal hernia repair is the fundamental step to reduce or avoid postoperative pain. Prophylactic ilioinguinal nerve neurectomy seems to offer some advantages concerning pain in the first 6th month postoperative period, although it might be possible that the small number of cases contributed to the insignificancy regarding paresthesia and hypoesthesia. Nowadays, prudent surgeons should discuss with patients and their families the uncertain benefits and the potential risk of neurectomy before performing the hernioplasty