The production of Z bosons associated with jets is measured in pp collisions at s=13TeV with data recorded with the CMS experiment at the LHC corresponding to an integrated luminosity of 36.3 fb-1 . The multiplicity of jets with transverse momentum pT>30GeV is measured for different regions of the Z boson's pT(Z) , from lower than 10 GeV to higher than 100 GeV . The azimuthal correlation ?? between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of pT(Z) . The measurements are compared with several predictions at leading and next-to-leading orders, interfaced with parton showers. Predictions based on transverse-momentum dependent parton distributions and corresponding parton showers give a good description of the measurement in the regions where multiple parton interactions and higher jet multiplicities are not important. The effects of multiple parton interactions are shown to be important to correctly describe the measured spectra in the low pT(Z) regions.

A search for nonresonant Higgs boson (H) pair production via gluon and vector boson (V) fusion is performed in the four-bottom-quark final state, using proton-proton collision data at 13 TeV corresponding to 138 fb^{-1} collected by the CMS experiment at the LHC. The analysis targets Lorentz-boosted H pairs identified using a graph neural network. It constrains the strengths relative to the standard model of the H self-coupling and the quartic VVHH couplings, ?_{2V}, excluding ?_{2V}=0 for the first time, with a significance of 6.3 standard deviations when other H couplings are fixed to their standard model values.

Decays of the Higgs boson into a [Formula presented] boson and a [Formula presented] or [Formula presented] meson are searched for in four-lepton final states with the CMS detector at the LHC. A data set of proton-proton collisions corresponding to an integrated luminosity of 138fb is used. Using the same data set, decays of the Higgs and [Formula presented] boson into quarkonium pairs are also searched for. An observation of such decays with this sample would indicate the presence of physics beyond the standard model. No evidence for these decays has been observed and upper limits at the 95% confidence level are placed on the corresponding branching fractions (B). Assuming longitudinal polarization of the Higgs boson decay products, 95% confidence level observed upper limits for [Formula presented] and [Formula presented] are 1.9×10 and 6.6×10, respectively.

A precise measurement of the invisible width of the Z boson produced in proton-proton collisions at a center-of-mass energy of 13 TeV is presented using data recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 36.3fb. The result is obtained from a simultaneous fit to kinematic distributions for two data samples of Z boson plus jets: one dominated by Z boson decays to invisible particles and the other by Z boson decays to muon and electron pairs. The invisible width is measured to be 523±3(stat)±16(syst)MeV. This result is the first precise measurement of the invisible width of the Z boson at a hadron collider, and is the single most precise direct measurement to date, competitive with the combined result of the direct measurements from the LEP experiments.

Measurements are presented of the B->?? branching fraction and effective lifetime, as well as results of a search for the B->?? decay in proton-proton collisions at s=13TeV at the LHC. The analysis is based on data collected with the CMS detector in 2016-2018 corresponding to an integrated luminosity of 140fb. The branching fraction of the B->?? decay and the effective B meson lifetime are the most precise single measurements to date. No evidence for the B->?? decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.

We search for new massive scalar particles X and Y through the resonant process X->YH->bb¯bb¯, where H is the standard model Higgs boson. Data from CERN LHC proton-proton collisions are used, collected at a centre-of-mass energy of 13 TeV in 2016-2018 and corresponding to an integrated luminosity of 138fb. The search is performed in mass ranges of 0.9-4 TeV for X and 60-600 GeV for Y, where both Y and H are reconstructed as Lorentz-boosted single large-area jets. The results are interpreted in the context of the next-to-minimal supersymmetric standard model and also in an extension of the standard model with two additional singlet scalar fields. The 95% confidence level upper limits for the production cross section vary between 0.1 and 150 fb depending on the X and Y masses, and represent a significant improvement over results from previous searches.

A search for the nonresonant production of Higgs boson pairs (HH ) via gluon-gluon and vector boson fusion processes in final states with two bottom quarks and two tau leptons is presented. The search uses data from proton-proton collisions at a center-of-mass energy of s=13TeV recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 138fb. Events in which at least one tau lepton decays hadronically are considered and multiple machine learning techniques are used to identify and extract the signal. The data are found to be consistent, within uncertainties, with the standard model (SM) predictions. Upper limits on the HH production cross section are set to constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to 3.3 (5.2) times the SM prediction for the inclusive HH cross section and to 124 (154) times the SM prediction for the vector boson fusion HH cross section. At 95% confidence level, the Higgs field self-coupling is constrained to be within -1.7 and 8.7 times the SM expectation, and the coupling of two Higgs bosons to two vector bosons is constrained to be within -0.4 and 2.6 times the SM expectation.

This Letter presents a search for direct production of charginos and neutralinos via electroweak interactions. The results are based on data from proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb. The search considers final states with large missing transverse momentum and pairs of hadronically decaying bosons WW, WZ, and WH, where H is the Higgs boson. These bosons are identified using novel algorithms. No significant excess of events is observed relative to the expectations from the standard model. Limits at the 95% confidence level are placed on the cross section for production of mass-degenerate wino-like supersymmetric particles ?~ and ?~, and mass-degenerate higgsino-like supersymmetric particles ?~, ?~, and ?~. In the limit of a nearly-massless lightest supersymmetric particle ?~, wino-like particles with masses up to 870 and 960 GeV are excluded in the cases of ?~->Z?~ and ?~->H?~, respectively, and higgsino-like particles are excluded between 300 and 650 GeV.

The first search exploiting the vector boson fusion process to probe heavy Majorana neutrinos and the Weinberg operator at the LHC is presented. The search is performed in the same-sign dimuon final state using a proton-proton collision dataset recorded at sqrt[s]=13 TeV, collected with the CMS detector and corresponding to a total integrated luminosity of 138 fb^{-1}. The results are found to agree with the predictions of the standard model. For heavy Majorana neutrinos, constraints on the squared mixing element between the muon and the heavy neutrino are derived in the heavy neutrino mass range 50 GeV-25 TeV; for masses above 650 GeV these are the most stringent constraints from searches at the LHC to date. A first test of the Weinberg operator at colliders provides an observed upper limit at 95% confidence level on the effective ?? Majorana neutrino mass of 10.8 GeV.

The double differential cross sections of the Drell-Yan lepton pair (ll , dielectron or dimuon) production are measured as functions of the invariant mass m , transverse momentum p(ll) , and ??* . The ??* observable, derived from angular measurements of the leptons and highly correlated with p(ll) , is used to probe the low- p(ll) region in a complementary way. Dilepton masses up to 1 TeV are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various m ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3 fb-1 of proton-proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 TeV . Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.

New sets of parameter tunes for two of the colour reconnection models, quantum chromodynamics-inspired and gluon-move, implemented in the pythia 8 event generator, are obtained based on the default CMS pythia 8 underlying-event tune, CP5. Measurements sensitive to the underlying event performed by the CMS experiment at centre-of-mass energies s=7 and 13 TeV , and by the CDF experiment at 1.96 TeV are used to constrain the parameters of colour reconnection models and multiple-parton interactions simultaneously. The new colour reconnection tunes are compared with various measurements at 1.96, 7, 8, and 13 TeV including measurements of the underlying-event, strange-particle multiplicities, jet substructure observables, jet shapes, and colour flow in top quark pair (t t ¯) events. The new tunes are also used to estimate the uncertainty related to colour reconnection modelling in the top quark mass measurement using the decay products of t t ¯ events in the semileptonic channel at 13 TeV .

Results are presented from a search for CP violation in top quark pair production, using proton-proton collisions at a center-of-mass energy of 13 TeV. The data used for this analysis consist of final states with two charged leptons collected by the CMS experiment, and correspond to an integrated luminosity of 35.9 fb. The search uses two observables, O and O, which are Lorentz scalars. The observable O is constructed from the four-momenta of the charged leptons and the reconstructed top quarks, while O consists of the four-momenta of the charged leptons and the b quarks originating from the top quarks. Asymmetries in these observables are sensitive to CP violation, and their measurement is used to determine the chromoelectric dipole moment of the top quark. The results are consistent with the expectation from the standard model. [Figure not available: see fulltext.].

Objective. Microbeam radiation therapy (MRT) is an alternative emerging radiotherapy treatment modality which has demonstrated effective radioresistant tumour control while sparing surrounding healthy tissue in preclinical trials. This apparent selectivity is achieved through MRT combining ultra-high dose rates with micron-scale spatial fractionation of the delivered x-ray treatment field. Quality assurance dosimetry for MRT must therefore overcome a significant challenge, as detectors require both a high dynamic range and a high spatial resolution to perform accurately. Approach. In this work, a series of radiation hard a-Si:H diodes, with different thicknesses and carrier selective contact configurations, have been characterised for x-ray dosimetry and real-time beam monitoring applications in extremely high flux beamlines utilised for MRT at the Australian Synchrotron. Results. These devices displayed superior radiation hardness under constant high dose-rate irradiations on the order of 6000 Gy s, with a variation in response of 10% over a delivered dose range of approximately 600 kGy. Dose linearity of each detector to x-rays with a peak energy of 117 keV is reported, with sensitivities ranging from (2.74 ± 0.02) nC/Gy to (4.96 ± 0.02) nC/Gy. For detectors with 0.8 ?m thick active a-Si:H layer, their operation in an edge-on orientation allows for the reconstruction of micron-size beam profiles (microbeams). The microbeams, with a nominal full-width-half-max of 50 ?m and a peak-to-peak separation of 400 ?m, were reconstructed with extreme accuracy. The full-width-half-max was observed as 55 ± 1 ?m. Evaluation of the peak-to-valley dose ratio and dose-rate dependence of the devices, as well as an x-ray induced charge (XBIC) map of a single pixel is also reported. Significance. These devices based on novel a-Si:H technology possess a unique combination of accurate dosimetric performance and radiation resistance, making them an ideal candidate for x-ray dosimetry in high dose-rate environments such as FLASH and MRT.

The charge-parity (CP) structure of the Yukawa interaction between the Higgs (H) boson and the top quark is measured in a data sample enriched in the t t ¯ H and tH associated production, using 138 fb of data collected in proton-proton collisions at s = 13 TeV by the CMS experiment at the CERN LHC. The study targets events where the H boson decays via H -> WW or H -> ?? and the top quarks decay via t -> Wb: the W bosons decay either leptonically or hadronically, and final states characterized by the presence of at least two leptons are studied. Machine learning techniques are applied to these final states to enhance the separation of CP -even from CP -odd scenarios. Two-dimensional confidence regions are set on ? and ?~ , which are respectively defined as the CP -even and CP -odd top-Higgs Yukawa coupling modifiers. No significant fractional CP -odd contributions, parameterized by the quantity | fCPHtt | are observed; the parameter is determined to be | fCPHtt | = 0.59 with an interval of (0.24, 0.81) at 68% confidence level. The results are combined with previous results covering the H -> ZZ and H -> ?? decay modes, yielding two- and one-dimensional confidence regions on ? and ?~ , while | fCPHtt | is determined to be | fCPHtt | = 0.28 with an interval of | fCPHtt | < 0.55 at 68% confidence level, in agreement with the standard model CP -even prediction of | fCPHtt | = 0. [Figure not available: see fulltext.].

Multijet events at large transverse momentum (p) are measured at s=13TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3fb-1 . The multiplicity of jets with pT>50GeV that are produced in association with a high- p dijet system is measured in various ranges of the p of the jet with the highest transverse momentum and as a function of the azimuthal angle difference ?? between the two highest p jets in the dijet system. The differential production cross sections are measured as a function of the transverse momenta of the four highest p jets. The measurements are compared with leading and next-to-leading order matrix element calculations supplemented with simulations of parton shower, hadronization, and multiparton interactions. In addition, the measurements are compared with next-to-leading order matrix element calculations combined with transverse-momentum dependent parton densities and transverse-momentum dependent parton shower.

Hydrogenated amorphous silicon is a well-known detector material for its radiation resistance. For this reason it has been used in particle beam flux measurements and in solar panels designed for space applications. This study concern 10?m thickness, p-i-n and charge selective contacts planar diode detectors which were irradiated with neutrons to two fluence values: 10 n/cm and 5 × 10 n/cm. In order to evaluate their radiation resistance, detector leakage current and response to x-ray photons have been measured. The effect of annealing for performance recovery at 100 °C for 12 and 24 h has also been studied. The results for the 10 n/cm irradiation show a factor 2 increase in leakage current that is completely recovered after annealing for p-i-n devices while charge selective contacts devices show an overall decrease of the leakage current at the end of the annealing process compared to the measurement before the irradiation. X-ray dosimetric sensitivity degrades, for this fluence, at the end of irradiation, but partially recovers for charge selective contact devices and increases for p-i-n devices at the end of the annealing process. Concerning the 5 × 10 n/cm irradiation test (for p-i-n structures only), due to the activation that occurred during the irradiation phase, the measurements were taken after 146 days of storage at around 0 °C, during this period, a self-annealing effect may have occurred. Therefore, the results after irradiation and storage show a noticeable degradation in leakage current and x-ray sensitivity with a small recovery after annealing.

The Large Hadron Collider (LHC) at CERN will undergo major upgrades to increase the instantaneous luminosity up to 5-7.5×1034 cm-2s-1. This High Luminosity upgrade of the LHC (HL-LHC) will deliver a total of 3000-4000 fb-1 of proton-proton collisions at a center-of-mass energy of 13-14 TeV. To cope with these challenging environmental conditions, the strip tracker of the CMS experiment will be upgraded using modules with two closely-spaced silicon sensors to provide information to include tracking in the Level-1 trigger selection. This paper describes the performance, in a test beam experiment, of the first prototype module based on the final version of the CMS Binary Chip front-end ASIC before and after the module was irradiated with neutrons. Results demonstrate that the prototype module satisfies the requirements, providing efficient tracking information, after being irradiated with a total fluence comparable to the one expected through the lifetime of the experiment.

The MIUR PRIN 4DInSiDe collaboration aims at developing the next generation of 4D (i.e., position and time) silicon detectors based on Low-Gain Avalanche Diodes (LGAD) that guarantee to operate efficiently in the future high-energy physics experiments. To this purpose, different areas of research have been identified, involving the development, design, fabrication and test of radiation-hard devices. This research has been enabled thanks to ad-hoc advanced TCAD modelling of LGAD devices, accounting for both technological issues as well as physical aspects, e.g. different avalanche generation models and combined surface and bulk radiation damage effects modelling. In this contribution, it is reviewed the progress and the relevant detector developments obtained during the research activities in the framework of the 4DInSiDe project.

The next generation of high-energy physics experiments at future hadronic colliders will require tracking detectors able to efficiently operate in extreme radiation environments, where expected fluences will exceed 1 × 10 n/cm. This new operating scenario imposes many efforts on the design of effective and radiation-resistant particle detectors. Low-Gain Avalanche Diode (LGAD) represents a remarkable advance because the radiation damage effects can be mitigated by exploiting its charge multiplication mechanism after heavy irradiation. To obtain the desired gain (about 10-20) on the sensor output signal, a careful implementation of the "multiplication" region is needed (i.e. the high-field junction implant). Moreover, a proper design of the peripheral region (namely, the guard-ring structure) is crucial to prevent premature breakdown and large leakage currents at very high fluences, when the bias voltage applied creates an electric field higher than 15 V/?m. In this contribution, the design of LGAD sensors for extreme fluence applications is discussed, addressing the critical technological aspects such as the choice of the active substrate thickness, the gain layer design and the optimization of the sensor periphery. The impact of several design strategies is evaluated with the aid of Technology-CAD (TCAD) simulations based on a recently proposed model for the numerical simulation of radiation damage effects on LGAD devices.

A search for new long-lived particles decaying to leptons using proton-proton collision data produced by the CERN LHC at s=13Te is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10cm and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113)fb-1 in the ee channel (e? and ? ? channels). The search is designed to be sensitive to a wide range of models with displaced e?, ee, and ? ? final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.