Jet physics at CMS

Measurements of the high momentum jet production in protonproton collisions at √s = 7TeV and 8TeV with the CMS experiment at the LHC are summarized. The CMS experimental program in this domain is, on the one hand, oriented toward the observables which may help to constrain the QCD parameters: strong coupling constant and evolution and proton PDF. On the other hand, a large effort is dedicated to the understanding of the conditions under which the soft gluon radiation plays an important role in the LHC physics. Different MC parton showering models are studied and measurements are provided to improve them

“Introduction. «L’ingénieur dans tous ses états»: l’essor d’un champ de recherche pluridisciplinaire et transnational”

En octobre 1980, se tenait à l’Ecomusée du Creusot, ce haut lieu symbolique d’histoire industrielle française, un colloque intitulé « Ingénieurs et société » , une grande première dans le genre. Réunie sur l’initiative du directeur de l’Ecomusée, Marcel Evrard, sous la présidence de l’historien André Thépot, une assemblée pluridisciplinaire d’experts a été invitée à réfléchir sur les origines et la nature du groupe professionnel des ingénieurs qui, malgré le nombre de travaux les mentionnant, demeuraient, selon le constat collectif des experts, d’illustres inconnus de l’histoire. Ainsi, les organisateurs ont-ils souhaité dresser le bilan des travaux sur les ingénieurs menés jusqu’alors « en ordre dispersé » à l’occasion et/ou dans le cadre d’études aux thématiques historiques connexes ciblant un domaine des techniques, un secteur de l’industrie, un champ de recherche scientifique, une aire géographique, une administration, une institution, une entreprise, une biographie d’exception, pour ne citer que les cadrages les plus fréquents. En revanche, tout symbolique que fût son rôle dans l’industrialisation aux XIXe et XXe siècles, le groupe professionnel des ingénieurs ne pouvait pas se prévaloir de référer son histoire « à un domaine historique et sociologique constitué » : il demeurait donc très difficile à catégoriser . La démarche a été sous-tendue par une prise de conscience importante, celle d’appréhender la perte de cohérence qui menaçait ce groupe professionnel sous l’impact de l’éclatement de plus en plus prononcé des domaines d’intervention, de la diversification des modes d’action et des fonctions assimilées. Désenclaver les recherches sur les ingénieurs en tant que groupe professionnel et phénomène de société, les sortir de leur confinement, leur imprimer une dynamique propre, – telle était l’ambition des promoteurs du colloque. Et l’ouvrage Ingénieurs dans la société française qui en est issu (1982), a posé les fondements d’un nouveau champ d’investigations, tant au point de vue des problématiques que des approches méthodologiques..

High rate, fast timing Glass RPC for the high {\eta} CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to $6.10^{34} cm^{-2} s^{-1}$ . The region of the forward muon spectrometer ($|{\eta}| > 1.6$) is not equipped with RPC stations. The increase of the expected particles rate up to $2 kHz/cm^{2}$ (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provides a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity (LR) glass is proposed to equip at least the two most far away of the four high ${\eta}$ muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux is presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.Comment: 14 pages, 11 figures, Conference proceeding for the 2016 Resistive Plate Chambers and Related Detector

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets