The study of the spin-parity and tensor structure of the interactions of the recently discovered Higgs boson is performed using the H → ZZ; Zγ Ã ; γ Ã γ Ã → 4l, H → WW → lνlν, and H → γγ decay modes. The full data set recorded by the CMS experiment during the LHC run 1 is used, corresponding to an integrated luminosity of up to 5.1 fb −1 at a center-of-mass energy of 7 TeV and up to 19.7 fb −1 at 8 TeV. A wide range of spin-two models is excluded at a 99% confidence level or higher, or at a 99.87% confidence level for the minimal gravitylike couplings, regardless of whether assumptions are made on the production mechanism. Any mixed-parity spin-one state is excluded in the ZZ and WW modes at a greater than 99.999% confidence level. Under the hypothesis that the resonance is a spin-zero boson, the tensor structure of the interactions of the Higgs boson with two vector bosons ZZ, Zγ, γγ, and WW is investigated and limits on eleven anomalous contributions are set. Tighter constraints on anomalous HVV interactions are obtained by combining the HZZ and HWW measurements. All observations are consistent with the expectations for the standard model Higgs boson with the quantum numbers J PC ¼ 0 þþ .
AbstracL W O new methods for madelling Kolmogomv phase fluctuations oyer a finite apenure are described. Ihe firs1 method relies on the incorporation of subharmonim in order to model accurately the low frequencies of the Kolmogomv SpeclNm. Ihc second method provides a less accurate, but much faster method for simulating the Kolmogorw spectrum ty using a midpoint displacement algorithm used in computer graphics. BackgroundThe simulation of atmospherically distorted wavefronts is an important tool for studying light propagation and imaging. The work in this paper is motivated by the need to develop efficient and effective methods of imaging astronomical objects through the turbulent atmosphere. Although the true test of any imaging algorithm is always provided by actual data, a good simulation is needed to be able to test different algorithms both in a controlled manner and under a wide variety of conditions. This paper outlines new methods for simulating the effects of static atmospheric turbulence, which is an essential component of any atmospheric imaging simulation.The starting point for nearly all analyses of atmospheric turbulence has been the assumption that atmospheric turbulence follows a Kolmogorov spectrum and has a phase that is statistically uniform Over the interval -T to T . The fluctuations induced by the turbulence then cause a distortion of both the magnitude and phase of the wavefront incident on the atmosphere. In practice the phase distortion has considerably more effect on the quality of images formed from light passing through the turbulence than those effects due to the magnitude distortion. In many situations, an adequate approximation is a single phase screen located at the entrance pupil of the optical system, although this can not account for non-isoplanatic effects [l].A typical short exposure image formed by viewing a point source through turbulence does not consist of a single diffraction pattern with a diameter fixed by the diffraction limit of the telescope, but rather the image consists of a number of superimposed speckles distributed over a diameter determined by the severity of the turbulence. Each individual bright speckle has a diameter given approximately by the diffraction limit of the telescope. It is important that in addition to the production of a speckled distortion of the image, the simulated turbulence should also shift the centroid of the image formed. This effect of centroid motion is primarily due to the low frequencies in the Kolmogorov spectrum, which are often not modelled well in conventional F F l procedures.Whilst it has been proposed that the centroid motion can be compensated after the generation of the speckles, this is not the only part of the information present
A measurement of the H → ττ signal strength is performed using events recorded in proton-proton collisions by the CMS experiment at the LHC in 2016 at a centerof-mass energy of 13 TeV. The data set corresponds to an integrated luminosity of 35.9 fb −1 . The H → ττ signal is established with a significance of 4.9 standard deviations, to be compared to an expected significance of 4.7 standard deviations. The best fit of the product of the observed H → ττ signal production cross section and branching fraction is 1.09 +0.27 −0.26 times the standard model expectation. The combination with the corresponding measurement performed with data collected by the CMS experiment at center-of-mass energies of 7 and 8 TeV leads to an observed significance of 5.9 standard deviations, equal to the expected significance. This is the first observation of Higgs boson decays to τ leptons by a single experiment.The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing a magnetic field of 3.8 T. Within the solenoid volume, there are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity coverage provided by the barrel and endcap detectors. Muons are detected in gas-ionization chambers embedded in the steel flux-return yoke outside the solenoid.Events of interest are selected using a two-tiered trigger system [29]. The first level (L1), composed of custom hardware processors, uses information from the calorimeters and muon detectors to select events at a rate of around 100 kHz within a time interval of less than 4 µs. The 4 Event reconstruction second level, known as the high-level trigger (HLT), consists of a farm of processors running a version of the full event reconstruction software optimized for fast processing, and reduces the event rate to about 1 kHz before data storage.Significant upgrades of the L1 trigger during the first long shutdown of the LHC have benefitted this analysis, especially in the τ h τ h channel. These upgrades improved the τ h identification at L1 by giving more flexibility to object isolation, allowing new techniques to suppress the contribution from additional pp interactions per bunch crossing, and to reconstruct the L1 τ h object in a fiducial region that matches more closely that of a true hadronic τ decay. The flexibility is achieved by employing high bandwidth optical links for data communication and large field-programmable gate arrays (FPGAs) for data processing.A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [30]. Simulated samplesSignal and background processes are modeled with samples of simulated events. The signal samples with a Higgs boson produced through gluon fusion (ggH), vector boson fusion (VBF), or in association with a W or Z boson (W...
The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.
A search for heavy, right-handed neutrinos, (), and right-handed bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8 corresponding to an integrated luminosity of 19.7 . For models with strict left-right symmetry, and assuming only one flavor contributes significantly to the decay width, the region in the two-dimensional mass plane excluded at a 95 % confidence level extends to approximately and covers a large range of neutrino masses below the boson mass, depending on the value of . This search significantly extends the exclusion region beyond previous results.Electronic supplementary materialThe online version of this article (doi:10.1140/epjc/s10052-014-3149-z) contains supplementary material, which is available to authorized users.
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