Search for Dark Matter and Supersymmetry with a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at root s=8 TeV

Peer reviewe

A Deep Neural Network for Simultaneous Estimation of b Jet Energy and Resolution

We describe a method to obtain point and dispersion estimates for the energies of jets arising from b quarks produced in proton-proton collisions at an energy of s = 13 TeV at the CERN LHC. The algorithm is trained on a large sample of simulated b jets and validated on data recorded by the CMS detector in 2017 corresponding to an integrated luminosity of 41 fb - 1 . A multivariate regression algorithm based on a deep feed-forward neural network employs jet composition and shape information, and the properties of reconstructed secondary vertices associated with the jet. The results of the algorithm are used to improve the sensitivity of analyses that make use of b jets in the final state, such as the observation of Higgs boson decay to b b ¯

Search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks in proton-proton collisions at root s=13TeV

A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is performed in proton-proton collisions at a center-of-mass energy of 13 TeV collected with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9 fb(-1). The signal is characterized by a large missing transverse momentum recoiling against a bottom quark-antiquark system that has a large Lorentz boost. The number of events observed in the data is consistent with the standard model background prediction. Results are interpreted in terms of limits both on parameters of the type-2 two-Higgs doublet model extended by an additional light pseudoscalar boson a (2HDM+a) and on parameters of a baryonic Z simplified model. The 2HDM+a model is tested experimentally for the first time. For the baryonic Z model, the presented results constitute the most stringent constraints to date.Peer reviewe

Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at s = 13 TeV

A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 16.1 fb - 1 , collected with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100 GeV are excluded and further sensitivity is explored towards higher masses

Search for new physics with a monojet and missing transverse energy in pp collisions at √s=7 TeV

This is the pre-print version of the Published Article which can be accessed at the link below.A study of events with missing transverse energy and an energetic jet is performed using pp collision data at a center-of-mass energy of 7 TeV. The data were collected by the CMS detector at the LHC, and correspond to an integrated luminosity of 36  pb-1. An excess of these events over standard model contributions is a signature of new physics such as large extra dimensions and unparticles. The number of observed events is in good agreement with the prediction of the standard model, and significant extension of the current limits on parameters of new physics benchmark models is achieved

Search for lepton flavour violating decays of the Higgs boson to eτand eμin proton–proton collisions at √s=8TeV

A direct search for lepton flavour violating decays of the Higgs boson (H) in the H →eτand H →eμchannels is described. The data sample used in the search was collected in proton–proton collisions at √s=8TeVwith the CMS detector at the LHC and corresponds to an integrated luminosity of 19.7fb−1. No evidence is found for lepton flavour violating decays in either final state. Upper limits on the branching fractions, B(H →eτ) <0.69%and B(H →eμ) <0.035%, are set at the 95% confidence level. The constraint set on B(H →eτ)is an order of magnitude more stringent than the existing indirect limits. The limits are used to constrain the corresponding flavour violating Yukawa couplings, absent in the standard model

Measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections in pp collisions at root s=7 TeV

Peer reviewe

Measurements of the t(t)over-bar production cross section in lepton plus jets final states in pp collisions at 8 and ratio of 8 to 7 TeV cross sections

Peer reviewe

Search for the X(5568) State Decaying into B-s(0)pi(+/-) in Proton-Proton Collisions at root s=8 TeV

A search for resonancelike structures in the B-s(0)pi(+/-) invariant mass spectrum is performed using proton-proton collision data collected by the CMS experiment at the LHC at root s = 8 TeV, corresponding to an integrated luminosity of 19.7 fb(-1). The B-s(0) mesons are reconstructed in the decay chain B-s(0) -> J/Psi phi, with J/Psi -> mu(+) mu(-) and phi -> K+K-. The B-s(0)pi(+/-) invariant mass distribution shows no statistically significant peaks for different selection requirements on the reconstructed B-s(0) and pi(+/-) candidates. Upper limits are set on the relative production rates of the X(5568) and B-s(0) states times the branching fraction of the decay X(5568)(+/-) -> B-s(0)pi(+/-). In addition, upper limits are obtained as a function of the mass and the natural width of possible exotic states decaying into B-s(0)pi(+/-).Peer reviewe

Mesoporous silica nanoparticles with tunable pore size for tailored gold nanoparticles

The aim of this paper was to verify a possible correlation between the pore-size of meso- porous silica nanoparticles (MSNs) and the sizes of gold nanoparticles (AuNPs) obtained by an impreg- nation of gold(III) chloride hydrate solution in the MSNs, followed by a specific thermal treatment. Mesoporous silica nanoparticles with tunable pore diameter were synthesized via a surfactant-assisted method. Tetraethoxysilane as silica precursor, cetyl- trimethylammonium bromide (CTAB) as surfactant and toluene as swelling agent were used. By varying the CTAB–toluene molar ratio, the average dimension of the pores could be tuned from 2.8 to 5.5 nm. Successively, thiol groups were grafted on the surface of the MSNs. Finally, the thermal evolution of the gold salt, followed by ‘‘in situ’’ X-ray powder diffraction (XRPD) and thermogravimetric analysis (TGA), revealed an evident correlation among the degradation of the thiol groups, the pore dimension of the MSNs and the size of the AuNPs. The samples were characterized by means of nitrogen adsorption– desorption, transmission electron microscopy, small- angle X-ray scattering, XRPD ‘‘in situ’’ by synchro- tron radiation, and ‘‘ex situ’’ by conventional tech- niques, diffuse reflectance infrared Fourier transform spectroscopy, and TGA