Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at root s=13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at root s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb(-1), collected in 2017-2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb(-1), collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.Peer reviewe

Combined searches for the production of supersymmetric top quark partners in proton-proton collisions at root s=13 TeV

A combination of searches for top squark pair production using proton-proton collision data at a center-of-mass energy of 13 TeV at the CERN LHC, corresponding to an integrated luminosity of 137 fb(-1) collected by the CMS experiment, is presented. Signatures with at least 2 jets and large missing transverse momentum are categorized into events with 0, 1, or 2 leptons. New results for regions of parameter space where the kinematical properties of top squark pair production and top quark pair production are very similar are presented. Depending on themodel, the combined result excludes a top squarkmass up to 1325 GeV for amassless neutralino, and a neutralinomass up to 700 GeV for a top squarkmass of 1150 GeV. Top squarks with masses from 145 to 295 GeV, for neutralino masses from 0 to 100 GeV, with a mass difference between the top squark and the neutralino in a window of 30 GeV around the mass of the top quark, are excluded for the first time with CMS data. The results of theses searches are also interpreted in an alternative signal model of dark matter production via a spin-0 mediator in association with a top quark pair. Upper limits are set on the cross section for mediator particle masses of up to 420 GeV

Probing effective field theory operators in the associated production of top quarks with a Z boson in multilepton final states at root s=13 TeV

Peer reviewe

Measurements of Higgs boson production cross sections and couplings in the diphoton decay channel at root s=13 TeV

Measurements of Higgs boson production cross sections and couplings in events where the Higgs boson decays into a pair of photons are reported. Events are selected from a sample of proton-proton collisions at root s = 13TeV collected by the CMS detector at the LHC from 2016 to 2018, corresponding to an integrated luminosity of 137 fb(-1). Analysis categories enriched in Higgs boson events produced via gluon fusion, vector boson fusion, vector boson associated production, and production associated with top quarks are constructed. The total Higgs boson signal strength, relative to the standard model (SM) prediction, is measured to be 1.12 +/- 0.09. Other properties of the Higgs boson are measured, including SM signal strength modifiers, production cross sections, and its couplings to other particles. These include the most precise measurements of gluon fusion and vector boson fusion Higgs boson production in several different kinematic regions, the first measurement of Higgs boson production in association with a top quark pair in five regions of the Higgs boson transverse momentum, and an upper limit on the rate of Higgs boson production in association with a single top quark. All results are found to be in agreement with the SM expectations.Peer reviewe

Observation of tW production in the single-lepton channel in pp collisions at root s=13 TeV

A measurement of the cross section of the associated production of a single top quark and a W boson in final states with a muon or electron and jets in proton-proton collisions at root s = 13 TeV is presented. The data correspond to an integrated luminosity of 36 fb(-1) collected with the CMS detector at the CERN LHC in 2016. A boosted decision tree is used to separate the tW signal from the dominant t (t) over bar background, whilst the subleading W+jets and multijet backgrounds are constrained using data-based estimates. This result is the first observation of the tW process in final states containing a muon or electron and jets, with a significance exceeding 5 standard deviations. The cross section is determined to be 89 +/- 4 (stat) +/- 12 (syst) pb, consistent with the standard model.Peer reviewe

Measurements of the Electroweak Diboson Production Cross Sections in Proton-Proton Collisions at root s=5.02 TeV Using Leptonic Decays

The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb(-1). Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as sigma(WW) = 37:0(-5.2)(+5.5) (stat)(-2.6)(+2.7) (syst) pb, sigma(WZ) = 6.4(-2.1)(+2.5) (stat)(-0.3)(+0.5)(syst) pb, and sigma(ZZ) = 5.3(-2.1)(+2.5)(stat)(-0.4)(+0.5) (syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy

Search for lepton-flavor violating decays of the Higgs boson in the mu tau and e tau final states in proton-proton collisions at root s=13 TeV

A search is presented for lepton-flavor violating decays of the Higgs boson to mu t and et. The dataset corresponds to an integrated luminosity of 137 fb(-1) collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, B(H -> mu t) e tau) < 0.22(0.16)% at 95% confidence level.Peer reviewe

Measurement of the top quark mass using events with a single reconstructed top quark in pp collisions at root s=13 TeV

Abstract:A measurement of the top quark mass is performed using a data sample en-riched with single top quark events produced in thetchannel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb−1, recorded at√s= 13TeV by the CMS experiment at the LHC in 2016. Candidate events are selectedby requiring an isolated high-momentum lepton (muon or electron) and exactly two jets,of which one is identified as originating from a bottom quark. Multivariate discriminantsare designed to separate the signal from the background. Optimized thresholds are placedon the discriminant outputs to obtain an event sample with high signal purity. The topquark mass is found to be172.13+0.76−0.77GeV, where the uncertainty includes both the sta-tistical and systematic components, reaching sub-GeV precision for the first time in thisevent topology. The masses of the top quark and antiquark are also determined separatelyusing the lepton charge in the final state, from which the mass ratio and difference aredetermined to be0.9952+0.0079−0.0104and0.83+1.79−1.35GeV, respectively. The results are consistentwithCPTinvariance

Search for a heavy Higgs boson decaying into two lighter Higgs bosons in the tau tau bb final state at 13 TeV

A search for a heavy Higgs boson H decaying into the observed Higgs boson h with a mass of 125 GeV and another Higgs boson h(S) is presented. The h and h(S) bosons are required to decay into a pair of tau leptons and a pair of b quarks, respectively. The search uses a sample of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137 fb(-1). Mass ranges of 240-3000 GeV for m(H) and 60-2800 GeV for m(hS) are explored in the search. No signal has been observed. Model independent 95% confidence level upper limits on the product of the production cross section and the branching fractions of the signal process are set with a sensitivity ranging from 125 fb (for m(H) = 240 GeV) to 2.7 fb (for m(H) = 1000 GeV). These limits are compared to maximally allowed products of the production cross section and the branching fractions of the signal process in the next-to-minimal supersymmetric extension of the standard model.Peer reviewe

Cholesterol als negativer post-transkriptioneller Regulator der Selenoprotein-Expression

Cholesterol ist eine essentielle Substanz im tierischen und menschlichen Organismus. Cholesterol wird in jeder Zelle durch den Mevalonatweg produziert und ist als Membranbestandteil für die Funktion und das Wachstum der Zellen von großer Bedeutung. Es existiert ein komplexes Netzwerk für die Regulation der Cholesterolsynthese, indem Cholesterol selbst und mehrere seiner Metabolite potente Inhibitoren der eigenen Synthese sind. Der Mevalonatweg liefert neben Cholesterol viele Zwischenprodukte für andere essentielle Zwecke. Eines dieser Zwischenprodukte, Isopentenylpyrophsophat, wird zur Reifung der Selenocystein-tRNA und somit zur Expression der Selenoproteine benötigt. Das Fehlen dieser Modifikation resultiert in einer reduzierten Expression speziell der stressinduzierbaren Selenoproteine wie der Glutathionperoxidasen (GPx). Die Ergebnisse in dieser Arbeit belegen einen funktionellen Zusammenhang zwischen Cholesterol- und Selenoprotein-Synthese und zeigen eine Unterdrückung der Selenoprotein-Expression durch Cholesterol und Oxysterole über einen post-transkriptionellen Mechanismus auf. Dieser Effekt ließ sich sowohl in vitro als auch in vivo beobachten. Zwei von vier in vitro untersuchten Oxysterolen, nämlich 22-Hydroxycholesterol und 25-Hydroxycholesterol, erwiesen sich in klonalen humanen Hepatozyten und T-Zellen als potente Supressoren der Expression der Phospholipid-Hydroperoxid-Glutathionperoxidase GPx4. Mildere Effekte wurden bezüglich der Cytosolischen Glutathionperoxidase GPx1 beobachtet. Das essentielle Haushalts-Selenoprotein Thioredoxin-Reduktase 1 (TrxR1) blieb bei Behandlung mit allen vier Hydroxysterolen in beiden Zelllinien konstant. Eine negative Kopplung zwischen Cholesterol und bestimmten Selenoproteinen konnte auch in vivo verifiziert werden. In zwei etablierten Mausmodellen der Hypercholsterolämie wurde eine deutliche Veränderung der hepatischen Selenoprotein-Expression festgestellt, wobei wiederum die GPx1 und die GPx4 von einer signifikant verringerten Expression betroffen waren. Die reduzierte Expression der beiden Glutathionperoxidasen in der Leber korrelierte mit einem erhöhten Gewebs-Cholesterol in diesen Tieren. In den Lebern von nicht-transgenen Mäusen, die aufgrund einer Fütterung mit einer Hochfett-Diät übergewichtig und prädiabetisch waren, aber keine erhöhten hepatischen Cholesterolwerte aufwiesen, konnte hingegen kein negativer Effekt auf die GPx1- und GPx4-Expression festgestellt werden. Diese Befunde deuten darauf hin, dass der negative Selenoprotein-Effekt einer Hypercholesterolämie auch in vivo als cholesterolspezifisch zu betrachten ist. Mechanistisch ergaben Messungen der Selenoprotein-Transkription in den untersuchten Tiermodellen sowie in den Zellkultur-Experimenten keinerlei Unterschiede, so dass ein post-transkriptioneller Effekt vorgelegen haben muss. Die Möglichkeit einer Selenocystein-tRNA-Reifungsstörung durch einen Mangel an Isopentenylpyrophosphat wird als wohl plausibelster Mechanismus der beobachteten Selenoprotein-Suppression diskutiert. Der Mangel an Isopentenylpyrophosphat wäre dabei durch die negative Hemmung des Mevalonatwegs durch Cholesterol zustande gekommen. Die in dieser Arbeit gewonnenen Erkenntnisse könnten einen Beitrag zur Erklärung der Arterioskleroseentstehung im Menschen leisten. Diese Erkrankung sowie andere mit erhöhten Cholesterolkonzentrationen assoziierte Pathologien können mechanistisch durch eine chronische Unterdrückung der Selenoprotein-Synthese mitverursacht sein. Inwieweit diese Befunde quantitativ auf den Menschen übertragbar sind, muss in nachfolgenden Untersuchungen überprüft werden. Dennoch sprechen mehrere große epidemiologische und Interventionsstudien, die einen inversen Zusammenhang zwischen dem Plasma-Selenspiegel und dem Cholesterolspiegel gezeigt haben, klar dafür, dass auch im Menschen eine gegenseitige Regulation von Cholesterol und Selenoproteinen existiert.Cholesterol is an essential substance in animals and humans. Cholesterol is produced in each cell by the mevalonate pathway and is of great importance as a membrane component essential for cell function and growth. There is a complex network for the regulation of cholesterol synthesis consisting of multiple feedback loops by which the products of the mevalonate pathway inhibit their exceeding synthesis. Besides cholesterol, the mevalonate pathway provides many other indispensable products like isopentenyl pyrophosphate, an isoprenoid which is required for the maturation of the selenocysteine tRNA and, thus, for the expression of the selenoproteins. Absence of this modification results in a specifically reduced expression of stress-inducible selenoproteins such as the glutathione peroxidases (GPx). The results in this work demonstrate a functional relationship between cholesterol and selenoprotein synthesis and show a suppression of selenoprotein expression by cholesterol and oxysterols via a post-transcriptional mechanism. This effect was observed both in vitro and in vivo. Two of the four oxysterols investigated in this work, namely 22-hydroxy-cholesterol und 25-hydroxy-cholesterol, acted as potent suppressors of phospholipid hydroperoxide glutathione peroxidase (GPx4) expression in clonal human hepatocytes clonal human T cells. Cytosolic glutathione peroxidase (GPx1) was also negatively affected, but to a lesser degree. The indispensable household selenoprotein thioredoxin reductase 1 (TrxR1), in contrast, remained constant with all four oxysterols in both cell lines. This cell-specific negative coupling between oxysterols and certain selenoproteins could also be observed in vivo. In the liver of two transgenic mouse models of hypercholesterolemia, a similar change in selenoprotein expression was observed, with GPx1 and GPx4 being significantly affected. In parallel, increased tissue cho-lesterol concentrations were observed in the analyzed livers. In the livers of non-transgenic, but obese and prediabetic mice being fed a high-fat diet, the levels of both glutathione peroxidases were unaltered, as were hepatic tissue cholesterol concentrations. This suggests that the supressive effect on selenoprotein expression may indeed have been cholesterol-specific. Mechanistically, measurements of selenoprotein transcription in the investigated animal models showed no differences, as was the case for the cell culture experiments. These data indicate the relevance of a post-transcriptional mechanism to account for the observed selenoprotein modulation. Most likely, the elevated cholesterol levels led to negative feedback inhibition of the mevalonate pathway and thereby to a lack of isopentenyl pyrophosphate. The latter compound would have then been insufficient for the complete maturation of the cellular selenocystein tRNA. The insight gained in this work may contribute to a better understanding of the etiology of arteriosclerosis and other cholesterol-associated diseases in humans. In fact, a variety of pathologies related to heightened cholesterol levels may be explained at least in part by a suppression of selenoprotein synthesis. In how far these findings can be translated to the clinical situation has yet to be determined. Nevertheless, several large epidemiological and intervention studies which have shown an inverse relationship between plasma selenium levels and cholesterol levels clearly indicate that a reciprocal regulation of cholesterol and selenoproteins is also operable in humans