S. Regnard

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.

Seven new archeointensity data are obtained through the analysis of groups of pottery and kiln fragments from ceramic workshops unearthed in France, precisely dated from the High Middle Ages. The measurements are carried out using the Triaxe magnetometer, following a dedicated experimental protocol that takes into account the effects of anisotropy and cooling rate (CR) on thermoremanent magnetization acquisition. The new data are consistent with the evolution of intensity variations described by our previous data obtained in France and Northern Italy, which display between the 5th and 10th c. a pronounced camel-back shape. In particular, they provide supporting evidence of an intensity minimum that occurred around the transition between the 7th and 8th century. These data, combined with a selection of previously published results within a 700 km radius of Beaune and re-examined based on CR correction, formed the basis of new regional mean intensity variation curves based on two independent modeling approaches. The first algorithm developed by Thébault and Gallet (2010) based on bootstrapping and now irregularly spaced knots according to the data distribution gives rather smooth intensity variations, while the second approach proposed by Livermore et al. (2018) based on a transdimensional Bayesian technique shows more abrupt variations with sometimes stronger amplitudes. We explore the dating potential of these two variations curves, which have an unprecedented resolution, by studying two medieval pottery workshops. Six fragment groups (three per workshop) are analyzed using the Triaxe protocol, providing mean archeointensity values for each of the two sites. Two different procedures are used for their dating, either by comparing the intensity value to be dated with the reference intensity variation curves obtained from the two modeling techniques or by analyzing the marginal posterior probability distribution of the age values derived from the method of Livermore et al. (2018). For France, the two techniques yield very similar results. The archeointensity dating results combined with archeological arguments and radiocarbon data, make it possible to better constrain the age of the end of activity of the two workshops. Archeointensity investigation of displaced materials thus appears as an effective means to obtain original chronological constraints on the age of their production, paving the way for a wide range of complementary research on Medieval pottery.

Abstract Gas shales are fine grained fissile detrital sedimentary rocks. But shale is often used as a catch-all term including different rocks with a non-negligible clay minerals content which leads to typical physical-chemical characteristics. Several properties are generally assessed for shale gas plays (TOC, porosity…). However, regarding the access to the reservoir, drilling into the formations implies a good knowledge of their mechanical and petrographic properties. As classical cores are quite difficult to collect from deep wells, unconventional techniques using small samples are useful (Tshibangu et al. 1999). When dealing with hydraulic fracturing, the formation brittleness is to be assessed. Several estimators exist among which we propose the so named plasticity index determined from punching tests. In the framework of a collaboration of more than fifteen years between the university and the drill bits manufacturer, samples coming from all over the World and associated with difficult drilling conditions have been collected and processed in the laboratory. This work involved thin section characterization and mechanical tests like FPMs abrasiveness, Shore hardness and punching tests. Recently, a database was then built in order to analyze the cumulated information (Descamps et al. 2013). In the context of gas shales, this database includes various fine grained rocks like shales, claystones, fine grained sandstones (i.e. grain or crystal size below 125 microns). In this paper, two main axes are developed. First, we describe typical properties of fine grained rocks, especially when they are associated to difficult drilling environments. Then, we look to how those properties can be linked together. Particular interest will be taken on abrasiveness regarding the selection of drilling bits and on brittleness assessment in relation to hydraulic fracturing.

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.

This thesis reports a study of Higgs boson production in proton-proton collisions at sqrt(s) = 13 TeV recorded with the CMS detector at the CERN Large Hadron Collider (LHC), exploiting the decay channel into a pair of Z bosons that in turn decay into pairs of electrons or muons (H->ZZ->4l, l = e,mu).This work is carried out in the context of the beginning of Run II of the LHC, a new data-taking period that started in 2015, following a two-year-long shutdown. This restart is marked by an increase of the centre-of-mass energy from 8 TeV to 13 TeV, and a narrowing of the spacing of proton bunches from 50 ns to 25 ns. These new parameters both increase the luminosity and set new constraints on the triggering, reconstruction and analysis of pp collision events. Therefore, considerable effort is devoted to the improvement and reoptimization of the CMS trigger system for Run II, focusing on the reconstruction and selection of electrons and on the preparation of multilepton trigger paths that preserve a maximal efficiency for the H->ZZ->4l channel.Secondly, the offline algorithms for electron and muon selection are optimized and their efficiencies are measured in data, while the selection logic of four-lepton candidates is improved. In order to extract rare production modes of the Higgs boson such as vector boson fusion, VH associated production and ttH associated production, a new classification of selected events into exclusive categories is introduced, using discriminants based on matrix-element calculations and jet flavour tagging.Results of the analysis of first 13 TeV data are presented for two data sets recorded in 2015 and early 2016, corresponding to integrated luminosities of 2.8 fb-1 and 12.9 fb-1, respectively. A standalone rediscovery of the Higgs boson in the four-lepton channel is achieved at the new energy. The signal strength relative to the standard model prediction, the mass and decay width of the boson, and a set of parameters describing the contributions of its main predicted production modes are measured. All results are in good agreement with standard model expectations for a 125 GeV Higgs boson within the incertainties, which are dominated by their statistical component with the current data set. Finally, a search for an additional high-mass resonance decaying to four leptons is performed, and no significant excess is observed.

The CMS experiment has been designed with a two-level trigger system. The first level is implemented on custom-designed electronics. The second level is the so-called High Level Trigger (HLT), a streamlined version of the CMS offline reconstruction software running on a computer farm. For Run II of the Large Hadron Collider, the increase in center-of-mass energy and luminosity will raise the event rate to a level challenging for the HLT algorithms. New approaches have been studied to contain the HLT rate within the available bandwidth while keeping thresholds low enough to cover the requirements of the physics analyses. The strategy mainly relies on porting online the improvements that have been applied to the offline reconstruction, thus allowing to move HLT selection closer to offline cuts. We present such changes in the definitions of HLT electrons and photons, focusing in particular on the deployment of a new clustering algorithm allowing pileup mitigation, a new Particle-Flow based isolation replacing the detector based method used in Run I, and an electron-dedicated track fitting algorithm based on a Gaussian Sum Filter.

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.

Measurements of Higgs boson properties using the H → ZZ → 4 ( = e, µ) decay channel are presented, based on a data sample corresponding to an integrated luminosity of 12.9 fb -1 of pp collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC during 2016.The observed significance for the standard model Higgs boson is 6.2σ at a mass of m H = 125.09GeV, where the expected significance is 6.5σ .The signal strength µ, defined as the ratio of the Higgs boson production cross section times branching fraction to four leptons to the standard model expectation, is measured to be µ = 0.99 +0.33 -0.26 .Individual strength parameters for four Higgs boson production modes are constrained for the first time using this channel.The Higgs boson mass is measured to be m H = 124.50+0.48 -0.46 GeV.The model-independent fiducial cross section is measured to be 2.29 +0.74 -0.64 (stat.)+0.30 -0.23 (sys.)+0.01 -0.05 (model dep.) fb, and differential cross sections as a function of the transverse momentum of the Higgs boson and the number of associated jets are measured.

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.

A summary of searches for heavy resonances decaying to a pair of bosons is presented, using pp collision data at $\sqrt{s} =$ 13 TeV collected by the CMS detector at the LHC during 2016. A striking feature common to most of these analyses is their boosted topology, in which the decay products of the considered bosons (both electroweak W and Z bosons and the Higgs boson) are expected to be highly energetic and close in angle, requiring a non-trivial identification of the final-state particles. The exploitation of jet substructure techniques allows an increase of the sensitivity of the searches where at least one boson decays hadronically. Various background estimation techniques are utilized, either based on hybrid data-simulation approaches or only relying on control regions in data. The data are found to be consistent with the background expectations, and the results are interpreted in the context of the bulk graviton and heavy vector triplet models.

The Barrel Muon Track finder of the CMS experiment at the Large Hadron Collider uses custom processors to identify muons and measure their momenta in the central region of the CMS detector. An upgrade of the L1 tracking algorithm is presented, featuring a Kalman Filter in FPGAs, implemented using High Level Synthesis tools. The matrix operations are mapped to the DSP cores reducing resource utilization to a level that allows the new algorithm to fit in the same FPGA as the legacy one, thus enabling studies during nominal CMS data taking. The algorithm performance has been verified in CMS collisions during 2018 operations. The algorithm is also proposed for standalone muon tracking at the High Luminosity LHC. The algorithm development is complemented by ATCA processor R&D featuring a large ZYNQ Ultrascale+ SoC with high speed optical links.