M. Lethuillier

The result of a search at the LHC for heavy stable charged particles produced in pp collisions at $ \sqrt {s} = 7\;{\text{TeV}} $ is described. The data sample was collected with the CMS detector and corresponds to an integrated luminosity of 3.1 pb−1. Momentum and ionization-energy-loss measurements in the inner tracker detector are used to identify tracks compatible with heavy slow-moving particles. Additionally, tracks passing muon identification requirements are also analyzed for the same signature. In each case, no candidate passes the selection, with an expected background of less than 0.1 events. A lower limit at the 95% confidence level on the mass of a stable gluino is set at 398GeV/c 2, using a conventional model of nuclear interactions that allows charged hadrons containing this particle to reach the muon detectors. A lower limit of 311 GeV/c 2 is also set for a stable gluino in a conservative scenario of complete charge suppression, where any hadron containing this particle becomes neutral before reaching the muon detectors.

Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.

A measurement of the top-antitop production cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV has been performed at the LHC with the CMS detector. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns and is based on the reconstruction of the final state with one isolated, high transverse-momentum electron or muon and three or more hadronic jets. The kinematic properties of the events are used to separate the top-antitop signal from W+jets and QCD multijet background events. The measured cross section is 173 + 39 - 32 (stat. + syst.) pb, consistent with standard model expectations.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

We consider present constraints on Two Higgs Doublet Models, both from the LHC at Run 1 and from other sources in order to explore the possibility of constraining a neutral scalar or pseudo-scalar particle lighter than the 125 GeV Higgs boson. Such a lighter particle is not yet completely excluded by present data. We show with a simplified analysis that some new constraints could be obtained at the LHC if such a search is performed by the experimental collaborations, which we therefore encourage to continue carrying out light diphoton resonance searches at $\sqrt{s}=$ 13 TeV in the context of Two Higgs Doublet Models.

The CMS and ATLAS experiments at the LHC have announced the discovery of a Higgs boson with mass at approximately 125 GeV/c2 in the search for the Standard Model Higgs boson via, notably, the γγ and ZZ to four leptons final states. Considering the recent results of the Higgs boson searches from the LHC, we study the lightest scalar Higgs boson h1 in the Next-to-Minimal Supersymmetric Standard Model by restricting the next-to-lightest scalar Higgs boson h2 to be the observed to the 125 GeV/c2 state. We perform a scan over the relevant NMSSM parameter space that is favoured by low fine-tuning considerations. Moreover, we also take the experimental constraints from direct searches, B-physics observables, relic density, and anomalous magnetic moment of the muon measurements, as well as the theoretical considerations, into account in our specific scan. We find that the signal rate in the two-photon final state for the NMSSM Higgs boson h1 with the mass range from about 80 GeV/c2 to about 122 GeV/c2 can be enhanced by a factor of up to 3.5 when the Higgs boson h2 is required to be compatible with the excess from latest LHC results. This motivates the extension of the search at the LHC for the Higgs boson h1 in the diphoton final state down to masses of 80 GeV/c2, particularly with the upcoming proton-proton collision data to be taken at center-of-mass energies of 13–14 TeV.

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

After the discovery of the Higgs boson with mass at approximately 125 $GeV$ at the LHC, many studies both from the theoretical and experimental sides have been performed to search for a new Higgs Boson lighter than the 125 $GeV$ Higgs boson. We explore the possibility of constraining a lighter neutral scalar Higgs boson $h_{1}$ and a lighter pseudo-scalar Higgs boson $a_{1}$ in the Next-to-Minimal Supersymmetric Standard Model by restricting the next-to-lightest scalar Higgs boson $h_{2}$ to be the LHC observed Higgs boson after the phenomenological constraints and the constraints from experimental measurements. Such lighter particles are not yet completely excluded by the latest results of the search for a lighter Higgs boson with the diphoton decay channel from LHC data. Our results show that for a lighter scalar Higgs boson some new constraints on the Next-to-Minimal Supersymmetric Standard Model could be obtained at the LHC if such a search is performed by the experimental collaborations with more data. The discovery potential of other interesting decay channels of such a lighter neutral scalar and a pseudo-scalar particle are also discussed.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”, one for each of the 61 200 channels. We present the calibration results and performance statistics obtained for more than 5000 production capsules.

A prospective analysis for the discovery of a light Higgs boson in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) is presented.The associated production channels WH and ZH of a Higgs boson decaying into a photon pair are studied using a full detector simulation.The method of analysis here employed should permit the utilisation of real data once they become available in order to optimise the analysis performance and to estimate background rates.Minimising in this way reliance on simulated data should allow a significant reduction in systematic errors.One year of LHC running at high luminosity (integrated luminosity of 100 fb -1 ) should allow an observation at 3σ of the Standard Model Higgs boson from the LEP lower limit of 114.4 GeV/c 2 up to 146 GeV/c 2 .Three years of running at high luminosity should allow a 5σ discovery from the LEP lower limit up to 148 GeV/c 2 .In the context of supersymmetric models, the dominant gluon fusion Higgs boson production process could be strongly suppressed.This light Higgs gluophobic scenario could occur when the mixing in the stop sector is maximal.In such a case, the associated production channels WH and ZH may be recovery channels.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps. These are made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”. Each of the 61,200 channels must be equipped with a capsule, the reliability of which must be assured since they will be inaccessible during the life of the experiment. The capsule production is now finished. We present the final calibration and performance statistics.