Nanostructured thin plastic foils have been used to enhance the mechanism of laser-driven proton beam acceleration. In particular, the presence of a monolayer of polystyrene nanospheres on the target front side has drastically enhanced the absorption of the incident 100 TW laser beam, leading to a consequent increase in the maximum proton energy and beam charge. The cutoff energy increased by about 60% for the optimal spheres' diameter of 535 nm in comparison to the planar foil. The total number of protons with energies higher than 1 MeV was increased approximately 5 times. To our knowledge this is the first experimental demonstration of such advanced target geometry. Experimental results are interpreted and discussed by means of 2(1/2)-dimensional particle-in-cell simulations.
Angular distributions of the decay B 0 → K * 0 µ + µ − are studied using a sample of proton-proton collisions at √ s = 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb −1 . An angular analysis is performed to determine the P 1 and P 5 parameters, where the P 5 parameter is of particular interest because of recent measurements that indicate a potential discrepancy with the standard model predictions. Based on a sample of 1397 signal events, the P 1 and P 5 parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with predictions based on the standard model.
A search is performed for anomalous interactions of the recently discovered Higgs boson using matrix element techniques with the information from its decay to four leptons and from associated Higgs boson production with two quark jets in either vector boson fusion or associated production with a vector boson. The data were recorded by the CMS experiment at the LHC at a center-of-mass energy of and correspond to an integrated luminosity of . They are combined with the data collected at center-of-mass energies of 7 and , corresponding to integrated luminosities of 5.1 and , respectively. All observations are consistent with the expectations for the standard model Higgs boson
A search for the production of Higgs boson pairs in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented, using a data sample corresponding to an integrated luminosity of 35.9 fb −1 collected with the CMS detector at the LHC. Events with one Higgs boson decaying into two bottom quarks and the other decaying into two τ leptons are explored to investigate both resonant and nonresonant production mechanisms. The data are found to be consistent, within uncertainties, with the standard model background predictions. For resonant production, upper limits at the 95% confidence level are set on the production cross section for Higgs boson pairs as a function of the hypothesized resonance mass and are interpreted in the context of the minimal supersymmetric standard model. For nonresonant production, upper limits on the production cross section constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to about 30 (25) times the prediction of the standard model.The discovery of the Higgs boson (H) by the ATLAS and CMS Collaborations [1-3] was a major step towards improving the understanding of the mechanism of electroweak symmetry breaking (EWSB). With the mass of the Higgs boson now precisely determined [4], the structure of the Higgs scalar field potential and the Higgs boson self-couplings are precisely predicted in the standard model (SM). While the measured properties of the Higgs boson are thus far consistent with the expectations from the SM [5], the measurement of the Higgs boson self-coupling provides an independent test of the SM and verification that the Higgs mechanism is truly responsible for the EWSB by giving access to the shape of the Higgs scalar field potential [6].The trilinear self-coupling of the Higgs boson (λ HHH ) can be extracted from the measurement of the Higgs boson pair (HH) production cross section. In the SM, for proton-proton (pp) collisions at the CERN LHC, this process occurs mainly via gluon-gluon fusion and involves either couplings of the Higgs boson to virtual fermions in a quantum loop, or the λ HHH coupling itself, with the two processes interfering destructively as illustrated in Fig. 1.The SM prediction for the cross section is σ HH = 33.49 +4.3% −6.0% (scale) ± 5.9% (theo) fb [7][8][9][10][11]. This value was computed at the next-to-next-to-leading order (NNLO) of the theoretical perturbative quantum chromodynamics (QCD) calculation, including next-to-next-to-leadinglogarithm (NNLL) corrections and finite top quark mass effects at next-to-leading order (NLO). The theoretical uncertainties in σ HH include uncertainties in the QCD factorization and renormalization scales, the strong coupling parameter α S , parton distribution functions (PDF), and unknown effects from the finite top quark mass at NNLO. * λ g g * g min 1 0 4π λ = √g min g * λ = g min IG. 1: Cartoon of the region in the plane (g ⇤ , /g ⇤ ), defined by Eqs. ( 13), (14), that can be probed y an analysis including only d...
A search is presented for additional scalar (H) or pseudoscalar (A) Higgs bosons decaying to a top quark pair in proton-proton collisions at a center-of-mass energy of 13 TeV. The data set analyzed corresponds to an integrated luminosity of 35.9 fb −1 collected by the CMS experiment at the LHC. Final states with one or two charged leptons are considered. The invariant mass of the reconstructed top quark pair system and variables that are sensitive to the spin of the particles decaying into the top quark pair are used to search for signatures of the H or A bosons. The interference with the standard model top quark pair background is taken into account. A moderate signal-like deviation compatible with an A boson with a mass of 400 GeV is observed with a global significance of 1.9 standard deviations. New stringent constraints are reported on the strength of the coupling of the hypothetical bosons to the top quark, with the mass of the bosons ranging from 400 to 750 GeV and their total relative width from 0.5 to 25%. The results of the search are also interpreted in a minimal supersymmetric standard model scenario. Values of m A from 400 to 700 GeV are probed, and a region with values of tan β below 1.0 to 1.5, depending on m A , is excluded at 95% confidence level.
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