128 Search Results

Abstract A minimal non-thermal dark matter model that can explain both the existence of dark matter and the baryon asymmetry in the universe is studied. It requires two color-triplet, iso-singlet scalars with$$$$ \mathcal{O}\left(\textrm{TeV}\right) $$$$ $O\left(\mathrm{TeV}\right)$ masses and a singlet Majorana fermion with a mass of$$$$ \mathcal{O}\left(\textrm{GeV}\right) $$$$ $O\left(\mathrm{GeV}\right)$ . The fermion becomes stable and can play the role of the dark matter candidate. We consider the fermion to interact with a top quark via the exchange of QCD-charged scalar fields coupled dominantly to third generation fermions. The signature of a single topmore » quark production associated with a bottom quark and large missing transverse momentum opens up the possibility to search for this type of model at the LHC in a way complementary to existing monotop searches.« less

For the first time at LHC energies, the forward rapidity gap spectra from proton-lead collisions for both proton and lead dissociation processes are presented. The analysis is performed over 10.4 units of pseudorapidity at a center-of-mass energy per nucleon pair of $$\sqrt{s_{NN}}$$ = 8.16 TeV , almost 300 times higher than in previous measurements of diffractive production in proton-nucleus collisions. For lead dissociation processes, which correspond to the pomeron-lead event topology, the EPOS-LHC generator predictions are a factor of 2 below the data, but the model gives a reasonable description of the rapidity gap spectrum shape. For the pomeron-proton topology,more » the EPOS-LHC, QGSJET II, and HIJING predictions are all at least a factor of 5 lower than the data. The latter effect might be explained by a significant contribution of ultraperipheral photoproduction events mimicking the signature of diffractive processes. These data may be of significant help in understanding the high energy limit of quantum chromodynamics and for modeling cosmic ray air showers.« less

A measurement is presented of the production of Z bosons that decay into two electrons or muons in association with jets, in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data were recorded by the CMS Collaboration at the LHC with an integrated luminosity of 35.9 fb$$^{-1}$$. The differential cross sections are measured as a function of the transverse momentum ($$p_\mathrm{T}$$) of the Z boson and the transverse momentum and rapidities of the five jets with largest $$p_\mathrm{T}$$. The jet multiplicity distribution is measured for up to eight jets. The hadronic activity in the events is estimated usingmore » the scalar sum of the $$p_\mathrm{T}$$ of all the jets. All measurements are unfolded to the stable particle-level and compared with predictions from various Monte Carlo event generators, as well as with expectations at leading and next-to-leading orders in perturbative quantum chromodynamics.« less

Multijet events at large transverse momentum ($$p$$_T) are measured at $$\sqrt{s}$$ = 13 TeV using data recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 36.3 fb^-1. The multiplicity of jets with $$p$$_T > 50 GeV that are produced in association with a high-$$p$$_T dijet system is measured in various ranges of the $$p$$_T of the jet with the highest transverse momentum and as a function of the azimuthal angle difference Δ$$\phi$$_1,2 between the two highest $$p$$_T jets in the dijet system. The differential production cross sections are measured as a function of the transversemore » momenta of the four highest $$p$$_T jets. The measurements are compared with leading and next-to-leading order matrix element calculations supplemented with simula tions 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.« less

A study of anomalous couplings of the Higgs boson to vector bosons and fermions is presented. The data were recorded by the CMS experiment at a center-of-mass energy of pp collisions at the LHC of 13 TeV and correspond to an integrated luminosity of 138 fb⁻¹. The study uses Higgs boson candidates produced mainly in gluon fusion or electroweak vector boson fusion at the LHC that subsequently decay to a pair of 𝜏 leptons. Matrix-element and machine-learning techniques were employed in a search for anomalous interactions. The results are combined with those from the four-lepton and two-photon decay channels tomore » yield the most stringent constraints on anomalous Higgs boson couplings to date. The pure 𝐶⁢𝑃-odd scenario of the Higgs boson coupling to gluons is excluded at 2.4 standard deviations. The results are consistent with the standard model predictions.« less

The production of Z bosons associated with jets is measured in pp collisions at $$\sqrt{s}=13\,\text {TeV}$$ 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 $$p$$_T > 30 GeV is measured for different regions of the Z boson’s $$p$$_T (Z ), from lower than 10 GeV to higher than 100 GeV. The azimuthal correlation $$Δ\phi$$ between the Z boson and the leading jet, as well as the correlations between the two leading jets are measured in three regions of $$p$$_T(Z ). The measurements aremore » 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 $$p$$_T(Z ) regions.« less

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at