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A detailed description is reported of the analysis used by the CMS Collaboration in the search for the standard model Higgs boson in pp collisions at the LHC, which led to the observation of a new boson. The data sample corresponds to integrated luminosities up to 5.1 fb −1 at √ s = 7 TeV, and up to 5.3 fb −1 at √ s = 8 TeV. The results for five Higgs boson decay modes γγ, ZZ, WW, τ τ , and bb, which show a combined local significance of 5 standard deviations near 125 GeV, are reviewed. A fit to the invariant mass of the two high resolution channels, γγ and ZZ → 4 , gives a mass estimate of 125.3 ± 0.4 (stat.) ± 0.5 (syst.) GeV. The measurements are interpreted in the context of the standard model Lagrangian for the scalar Higgs field interacting with fermions and vector bosons. The measured values of the corresponding couplings are compared to the standard model predictions. The hypothesis of custodial symmetry is tested through the measurement of the ratio of the couplings to the W and Z bosons. All the results are consistent, within their uncertainties, with the expectations for a standard model Higgs boson. The CMS collaboration 106 Keywords: Hadron-Hadron Scattering IntroductionThe standard model (SM) [1-3] of particle physics accurately describes many experimental results that probe elementary particles and their interactions up to an energy scale of a few hundred GeV [4]. In the SM, the building blocks of matter, the fermions, are comprised of quarks and leptons. The interactions are mediated through the exchange of force carriers: the photon for electromagnetic interactions, the W and Z bosons for weak interactions, and the gluons for strong interactions. All the elementary particles acquire mass through their interaction with the Higgs field [5][6][7][8][9][10][11][12][13]. This mechanism, called the "Higgs" or "BEH" mechanism [5][6][7][8][9][10], is the first coherent and the simplest solution for giving mass to W and Z bosons, while still preserving the symmetry of the Lagrangian. It is realized by introducing a new complex scalar field into the model. By construction, this field allows the W and Z bosons to acquire mass whilst the photon remains massless, and adds to the model one new scalar particle, the SM Higgs boson (H). The Higgs scalar field and its conjugate can also give mass to the fermions, through Yukawa interactions [11][12][13] The discovery or exclusion of the SM Higgs boson is one of the primary scientific goals of the LHC. Previous direct searches at the LHC were based on data from protonproton collisions corresponding to an integrated luminosity of 5.1 fb −1 collected at a centreof-mass energy of 7 TeV. The CMS experiment excluded at 95% CL masses from 127 to 600 GeV [20]. The ATLAS experiment excluded at 95% CL the ranges 111. . Within the remaining allowed mass region, an excess of events between 2 and 3 standard deviations (σ) near 125 GeV was reported by both experiments. In 2012, the proton-proton centre-of-mass energy was increased to 8 TeV, and by the end of June, an...

A search for supersymmetry with R-parity conservation in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data correspond to an integrated luminosity of 35 inverse picobarns collected by the CMS experiment at the LHC. The search is performed in events with jets and significant missing transverse energy, characteristic of the decays of heavy, pair-produced squarks and gluinos. The primary background, from standard model multijet production, is reduced by several orders of magnitude to a negligible level by the application of a set of robust kinematic requirements. With this selection, the data are consistent with the standard model backgrounds, namely t t-bar, W + jet and Z + jet production, which are estimated from data control samples. Limits are set on the parameters of the constrained minimal supersymmetric extension of the standard model. These limits extend those set previously by experiments at the Tevatron and LEP colliders

Spectra of identified charged hadrons are measured in pp collisions at the LHC for √ s = 0.9, 2.76, and 7 TeV. Charged pions, kaons, and protons in the transversemomentum range p T ≈ 0.1-1.7 GeV/c and for rapidities |y| < 1 are identified via their energy loss in the CMS silicon tracker. The average p T increases rapidly with the mass of the hadron and the event charged-particle multiplicity, independently of the center-of-mass energy. The fully corrected p T spectra and integrated yields are compared to various tunes of the PYTHIA 6 and PYTHIA 8 event generators.

A search for neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM) decaying to tau-lepton pairs in pp collisions is performed, using events recorded by the CMS experiment at the LHC. The dataset corresponds to an integrated luminosity of 24.6 fb −1 , with 4.9 fb −1 at 7 TeV and 19.7 fb −1 at 8 TeV. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes the case where the Higgs boson is produced in association with a b-quark jet. No excess is observed in the tau-lepton-pair invariant mass spectrum. Exclusion limits are presented in the MSSM parameter space for different benchmark scenarios, m max h , m mod+ h , m mod− h , light-stop, lightstau, τ -phobic, and low-m H . Upper limits on the cross section times branching fraction for gluon fusion and b-quark associated Higgs boson production are also given. A Exclusion limits 23The CMS collaboration 37 IntroductionA broad variety of precision measurements have shown the overwhelming success of the standard model (SM) [1][2][3] of fundamental interactions, which includes an explanation for the origin of the mass of the weak force carriers, as well as for the quark and lepton masses. In the SM, this is achieved via the Brout-Englert-Higgs mechanism [4][5][6][7][8][9], which predicts the existence of a scalar boson, the Higgs boson. However, the Higgs boson mass in the SM is not protected against quadratically divergent quantum-loop corrections at high energy, known as the hierarchy problem. In the model of supersymmetry (SUSY) [10,11], which postulates a symmetry between the fundamental bosons and fermions, a cancellation of these divergences occurs naturally. The Higgs sector of the minimal supersymmetric extension of the standard model (MSSM) [12,13] The dominant neutral MSSM Higgs boson production mechanism is the gluon fusion process for small and moderate values of tan β. At large values of tan β b-quark associated production is the dominant contribution, due to the enhanced Higgs boson Yukawa coupling to b quarks. Figure 1 shows the leading-order diagrams for the gluon fusion and b-quark associated Higgs boson production, in the four-flavor and in the five-flavor scheme. In the region of large tan β the branching fraction to tau leptons is also enhanced, making the search for neutral MSSM Higgs bosons in the τ τ final state particularly interesting. This paper reports a search for neutral MSSM Higgs bosons in pp collisions at √ s = 7 TeV and 8 TeV in the τ τ decay channel. The data were recorded with the CMS detector [14] at the CERN LHC and correspond to an integrated luminosity of 24.6 fb −1 , with 4.9 fb −1 at 7 TeV and 19.7 fb −1 at 8 TeV. Five different τ τ signatures are studied, eτ h , µτ h , eµ, µµ, and τ h τ h , where τ h denotes a hadronically decaying τ . These results are an extension of previous searches by the The results are interpreted in the context of the MSSM with different benchmark scenarios described in section 1.1 and also in a model independent way, in terms of upper...