Testing New Physics with bottom quarks at LHC: a pragmatic approach

2013/2014This work discusses how Bottom-quark physics at the Large Hadron Collider (LHC) can be used as a probe to hint to Beyond the Standard Model Physics from a phenomenological point of view. In this contest, the calculation of three observables is presented, all related to the production of one boson (Z, or a Higgs particle of Beyond the Standard Model nature) in association with a bottom-quark. The Polarization Asymmetry of the Z-boson produced in association with a b-quark is computed at Leading Order, using the 5-flavours number scheme, assuming it is measured at the LHC with a center of mass energy of 14 TeV. It is shown how this observable can be used for an accurate determination of the A_b parameter, measured at the Stanford Linear Collider (and, indirectly, at the Large Electron Positron), and known to be in tension with its Standard Model prediction: this strongly motivates its new, independent, determination at the LHC. As an estimate of the theoretical uncertainties affecting the prediction of the Polarization Asymmetry, this is re-computed varying both the renormalization/factorization scale and the Parton Density Function set, showing its strong stability against such effects. The Forward-Backward asymmetry of the b-quark produced in association with a leptonically decaying Z-boson, firstly defined by the candidate, is computed at LO in the 5-flavours number scheme. It is here shown that this observable inherits, from the Polarization Asymmetry of the Z-boson in the same process, stability under factorization/renormalization scale variations and PDF-set choice. For this observable, directly accessible by the LHC experimental collaborations, a complete feasibility study is presented in this work, simulating, with modern tools (MadGraph, PYTHIA, Delphes), both the showering/hadronization processes and the detector response, assuming a final integrated luminosity of 400 fb^-1 with 14 TeV in the center of mass of the colliding proton beams. This allows to determine, for the Forward-Backward asymmetry, an upper bound on the leading experimental systematic and statistical uncertainties at the next LHC run. Finally, the production cross section of a light Higgs boson in association with one b-quark is computed at Next-to-Leading Order in alpha_em in the framework of the Next-to-Minimal Supersymmetric Standard Model. The calculation has been done in the 5FNS, using, respectively, the DRBAR renormalisation scheme to manage Ultraviolet divergencies, and the soft-photon approximation to treat consistently Infrared divergencies. This is the first calculation of the Electromagnetic NLO effect in the NMSSM, which shows a relevant relative magnitude respect to the LO determination of genuinely NMSSM nature.XXVII Ciclo198

Dark matter at the LHC

Review of recent ATLAS and CMS results abobut Dark matter searches, intended for as an overview LHC talk to be presented at a conference with a rather broad audience

Highlights of top-quark production cross-section measurements with ATLAS at LHC: from precision to rarity

Top-quark production in proton-proton collisions at a center-of-mass energy of 13 TeV is measured with the data collected by the ATLAS detector over five orders of magnitude. The relatively large inclusive cross-section for the production of top-quark pair production is deter- mined using events in the lepton+jets channel and it reaches a relative uncertainty of 4.6% allowing for experimental scrutiny to theoretical calculations at next-to-next-to-leading order. Measurements of differential cross-sections of top-quark-antiquark pair-production performed in the all-hadronic channel allow studies of the correlation between the top-quark pair system and additional jet radiation by exploiting fully-reconstructed final states. Such measurements are com- pared quantitatively with predictions from several setups of next-to-leading order matrix-element generators combined with parton-shower generators. Finally, the ATLAS collaboration recently established first evidence for the hard scattering process in which two top-quark-antiquark pairs are produced. This process is also called four-top-quarks production and is predicted to have a small cross-section of 12 fb in the standard model. Candidate events are selected if a lepton pair with the same electric charge is present or if there are at least three leptons in the event. The background is mainly given by top-quark-antiquark production in association with a W boson and heavy-flavour jets. A multivariate discriminant is used to optimize the separation between signal and background events and enhance the sensitivity

Prospects for measurements of the four-top-quark production cross section at the ATLAS experiment at the HL-LHC

In run 2 of the Large Hadron Collider the ATLAS experiment has found the first evidence for the four-top-quark production processes. In this contribution, we present a sensitivity study of the high-luminosity phase of the LHC to this extremely rare process with a cross section in the Standard Model of only 12 fb. Projections are given for the precision of the inclusive $t\bar{t}t\bar{t}$ cross section measurements in several scenarios extrapolating the run 2 measurements

Charged triple Gauge couplings at present and future colliders.

Due to its non abelian nature, the Standard Model gauge group allows the presence, among others, of a charged Triple Gauge Coupling (cTGC) γ∗/ZW+W− between a neutral and two charged electroweak gauge bosons. Such coupling can receive Beyond the Standard Model (BSM) contributions, leaving open the possibility of anomalous cTGC not yet constrained by electroweak precision measurements. We focus on W+W− production, which can be probed both at hadron and lepton colliders, presenting a feasibility study for searches for BSM contributions in cTGC both at present and future colliders

Ten Years After Bariatric Surgery: Bad Quality of Life Promotes the Need of Psychological Interventions

Background: This study aims to evaluate long-term quality of life (QoL) and primary clinical outcomes, 10 years after biliointestinal bypass (BIB) surgery. It was expected that, although BIB might show encouraging primary outcomes, long term QoL could be significantly impaired.Methods: Ninety patients were contacted for a phone interview [age 41.0 ± 10.6 (mean ± SD) years, age-range 31-65 years]. QoL (by SF-36) and the clinical situation (by ad hoc questionnaire) were collected. Data were analyzed with SPSS 22. SF-36 scores were compared with Italian normative data from general and healthy population. We also compared primary clinical outcomes and SF-36 scores between patients who reported high and low levels of satisfaction with BIB.Results: Considering SF-36 results, patients showed significant impairments in QoL compared to general and healthy populations. Sixty-five percent would repeat the BIB. All patients showed at least one chronic adverse event. It occurred a significant decrease in pre-post co-occurrence rates of diabetes (χ2 = 18.41; p < 0.001) and hypertension (χ2 = 50.27; p < 0.001). Large and significant weight loss indexes (i.e., percent excess weight loss (%EWL); body mass index) were observed between pre-post intervention.Conclusion: BIB showed promising primary clinical outcomes (i.e., hypertension, diabetes, and weight loss). However, subjects reported a significant impairment in all SF-36 domains. Ad hoc psychological interventions should be implemented to ameliorate the quality of life of these patients

Intracorporeal Versus Extracorporeal Anastomosis in Laparoscopic Right Colectomy: An Updated Systematic Review and Cumulative Meta-Analysis

Purpose: The effect of intracorporeal anastomosis (IA) versus extracorporeal anastomosis (EA) in laparoscopic right hemicolectomy is controversial. The aim of this study was to evaluate the safety, effectiveness, and functional outcomes of IA compared with EA and to explore the timely tendency variations favoring one treatment over another. Materials and Methods: PubMed, EMBASE, and Web of Science were consulted. A systematic review, pairwise meta-analysis, and cumulative meta-analysis were conducted. Results: Twenty-three studies (3755 patients) were included: 45.7% underwent IA, whereas 54.3% underwent EA. The estimated pooled postoperative infectious complications, anastomotic leak, and overall complications risk ratios were 0.51 (95% confidence interval [CI]: 0.31 to 0.84; P = .009), 0.64 (95% CI: 0.40 to 1.03; P = .063), and 0.78 (95% CI: 0.62 to 0.97; P = .028), respectively. The cumulative meta-analysis showed a statistically significant timely tendency in favor of IA while considering infectious and overall complications. The estimated pooled mean difference of time to first flatus, first defecation, first oral diet, and hospital stay were -16.68 (P < .001), -25.94 (P < .001), -16.35 (P < .001), and -0.72 (P < .001), respectively. Again, the cumulative meta-analysis showed a statistically significant timely trend in favor of IA. No differences were found in term of operative time, conversion rate, ileus, bleeding, reoperation, 30-day readmission, and 30-day mortality. Conclusions: Compared with EA, IA seems to be associated with reduced postoperative infectious and overall complications. The time to first flatus, time to defecation, time to liquid diet, and hospital length of stay were estimated to be lower. A statistically significant timely trend favoring IA was noticed for postoperative infectious complications, overall complications, and recovery parameters. Further studies are warranted to confirm these results and to deeply investigate the supposed timely tendency convergence in favor of IA

Correction: Advice of General Practitioner, of Surgeon, of Endocrinologist, and Self-Determination: the Italian Road to Bariatric Surgery

Purpose Bariatric surgery (BS) is considered the most efcient treatment for severe obesity. International guidelines recommend multidisciplinary approach to BS (general practitioners, endocrinologists, surgeons, psychologists, or psychiatrists), and access to BS should be the fnal part of a protocol of treatment of obesity. However, there are indications that general practitioners (GPs) are not fully aware of the possible benefts of BS, that specialty physicians are reluctant to refer their patients to surgeons, and that patients with obesity choose self-management of their own obesity, including internet-based choices. There are no data on the pathways chosen by physicians and patients to undergo BS in the real world in Italy. Methods An exploratory exam was performed for 6 months in three pilot regions (Lombardy, Lazio, Campania) in twentythree tertiary centers for the treatment of morbid obesity, to describe the real pathways to BS in Italy. Results Charts of 2686 patients (788 men and 1895 women, 75.5% in the age range 30–59 years) were evaluated by physicians and surgeons of the participating centers. A chronic condition of obesity was evident for the majority of patients, as indicated by duration of obesity, by presence of several associated medical problems, and by frequency of previous dietary attempts to weight loss. The vast majority (75.8%) patients were self-presenting or referred by bariatric surgeons, 24.2% patients referred by GPs and other specialists. Self-presenting patients were younger, more educated, more professional, and more mobile than patients referred by other physicians. Patients above the age of 40 years or with a duration of obesity greater than 10 years had a higher prevalence of all associated medical problems. Conclusions The majority of patients referred to a tertiary center for the treatment of morbid obesity have a valid indication for BS. Most patients self-refer to the centers, with a minority referred by a GP or by specialists. Self-presenting patient