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Application of the principle of maximum conformality to the top-quark forward-backward asymmetry at the Tevatron
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Diboson production at LHC and Tevatron
This is a report at the conference Physics In Collision 2013. The experimental results on physics of diboson production are reviewed. The measurements use pp collision at the LHC with center-of-mass energy [Formula: see text] and 8 TeV, and [Formula: see text] collision at the Tevatron with [Formula: see text]. These include measurements of Wγ, Zγ, WW, WZ and ZZ production. The results are compared with Standard Model predictions, and are interpreted in terms of constraints on charged and neutral anomalous triple gauge couplings.
Search for the Higgs Boson and for Anomalous Quartic Gauge Boson Couplings in the WW Channel with Dielectron Events with the D0 Experiment at the Tevatron; Recherche du boson de Higgs et de couplages de jauge quartiques anormaux dans le canal WW en électrons dans l'expérience D0 au Tevatron
Le paysage de la physique des particules a subi des changements majeurs entre le début de cette thèse, en septembre 2010, et sa n en juin 2013. On peut notamment qualier l'année 2012 de date-clé dans l'histoire de la physique des particules. En 2012, une nouvelle particule a été découverte au LHC [1, 2], dont la majeure partie de la communauté s'accorde aujourd'hui à dire qu'il s'agit très probablement du boson de Higgs. Cet événement est intervenu peu après une sorte de passage de relais entre le Tevatron, arrêté le 30 septembre 2011, et le LHC, dont les toutes premières collisions sont intervenues le 23 novembre 2009.
Recherche du boson de Higgs dans l'état final dimuonique et étude de l'asymétrie de production de la paire top antitop avec l'expérience DO auprès du Tevatron; Higgs boson search in the dimuonique final state and study of the top pair antitop production asymmetry with the DO experiment at the Tevatron.
Two high energy particle physics analyses are presented in this PhD report using events with two leptons oppositely charged and with missing transverse energy. These events are selected using 9.7 fb-1 of total pp collisions data collected with the DØ detector at the TeVatron at √s=1.96 TeV.The first analysis is the research of the Higgs boson decaying in the H→WW→μνμν channel. No significant excess above the background prediction is observed.Upper limits on Higgs boson production cross-section are computed in the standard model framework but also in the 4th generation of fermions and in the fermiophobic coupling to Higgs boson hypotheses. In order to validate the research methodology, the W boson pair production cross-section is measured.The second analysis is the measurement of the forward-backward asymmetry of the tt pair production. This is the first measurement in the dileptonic channel at DØ experiment. In this context, a new tt pair kinematic reconstruction is used (matrix element method) to give a raw measurement of the forward-backward asymmetry. Thanks to a dedicated calibration method, we give a final measurement of AFB=18.0 ± 6.0 (stat) ± 3.3 (syst).
Production of c and b quarks in $p\bar{p}$ collisions at the Tevatron collider at $\sqrt{s}$ = 1.96 ТеV; Народження $c$ та $b$ кварків в $p\bar{p}$ зіткненнях на колайдері Tevatron при $Е_{цм}$ = 1.96 ТеВ
The results of the measurements of c and b quarks productions in proton-antiproton collisions at the D0 experiment at the Tevatron are presented in this thesis. Measurements have been done in 2 aspects: measurement of the W +b-jet and W +c-jet differential production cross sections and a measurement of the fiducial cross sections of quarkonium productions of c quark, simultaneously production of two J/ψ mesons, simultaneously production of J/ψ and Υ mesons in the muon channel decay.
Combination of measurements of the top-quark pair production cross section from the Tevatron Collider
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Observation and studies of double J/psi production at the Tevatron
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Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from $t\bar t$ production at the Tevatron
We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in tt¯ production in dilepton final states using 9.7 fb –1 of proton-antiproton collisions at √s=1.96 TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible tt¯ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of A tt¯ =(15.0±6.4(stat)±4.9(syst))% and a top-quark polarization times spin analyzing power in the beam basis of κP=(7.2±10.5(stat)±4.2(syst))%, with a correlation of –56% between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of κP=(11.3±9.1(stat)±1.9(syst))%. If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of A tt¯ =(17.5±5.6(stat)±3.1(syst))%. A combination with the D0 A tt¯ measurement in the lepton+jets final state yields an asymmetry of Att¯=(11.8±2.5(stat)±1.3(syst))%. Within their respective uncertainties, all these results are consistent with the standard model expectations.
Tevatron Run II combination of the effective leptonic electroweak mixing angle
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Tevatron combination of single-top-quark cross sections and determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $\bf V_{tb}$
In this study, we present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb -1 per experiment. The t-channel cross section is measured to be σ t = 2.25$+0.29\atop{-0.31}$ pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ s+t = 3.30$+0.52\atop{-0.40}$ pb, without assuming the standard model value for the ratio σ s /σ t . The resulting value of the magnitude of the top-to-bottom quark coupling is |V tb |= 1.02$+0.06\atop{-0.05}$, corresponding to |V tb | > 0.92 at the 95% C.L.
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
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Light Gluinos in Hiding: Reconstructing R-Parity Violating Decays at the Tevatron
If gluinos exist with masses less than 200 GeV, they are copiously produced at the Tevatron, but still may not have been discovered if they decay through baryon number violating operators. We show that using cuts on jet substructure can enable a discovery with existing data and even determine the gluino's mass. This contribution has demonstrated that the Tevatron can discover new light colored particles that decay into complicated hadronic final states, by using events where these particles are produced at high p{sub T} and their boosted decay products are collimated. The recently developed techniques using jet substructure can effectively separate signal from background, allowing the new particle to appear as a jet-mass resonance. This work is a proof-of-principle, but there is significantly more work to be done. Neither of the Tevatron's two detectors have calorimetry that is as finely segmented as the LHC detectors, where most studies have been done so far, and this may reduce the jet mass resolution and restrict the Tevatron reach. Some of this resolution loss may be recovered by using tracking information, particularly at CDF [99]. On the theoretical side, the optimal cuts and jet-size for a given mass have not been determined, nor have other jet algorithms such as Cambridge/Aachen been studied. Switching to a more inclusive analysis may also improve sensitivity. The primary challenge is to keep signal efficiency high due to the low number of gluinos in the high p{sub T} tail, e.g. with m{sub {tilde g}} = 150 GeV we see 18% of gluinos with p{sub T} > 350 GeV reconstructed using R = 1.0. Therefore it may be beneficial to search for one narrow gluino candidate jet with tight constraints recoiling against another wide jet-size gluino candidate jet. The application of loose substructure cuts to the jets of the ordinary di-jet search is also interesting. If the squarks become light enough that associated squark-gluino production or squark pair production becomes sizable, then the dominant source of boosted gluinos may come from these secondary processes. This is qualitatively similar to the models studied in [65] where the hadronically decaying LSP was being produced in cascade decays of squarks and gluinos.
Measurement of top quark properties at the Tevatron and LHC
Almost two decades after its discovery at Fermilab's Tevatron collider experiments, the top quark is still under the spotlight due to its connections to some of the most interesting puzzles in the Standard Model. The Tevatron has been shut down two years ago, yet some interesting results are coming out of the CDF and D0 collaborations. The LHC collider at CERN produced two orders of magnitude more top quarks than Tevatron's, thus giving birth to a new era for top quark physics. While the LHC is also down at the time of this writing, many top quark physics results are being extracted out of the 7\,TeV and 8\,TeV proton proton collisions by the ATLAS and CMS collaborations, and many more are expected to appear before the LHC will be turned on again sometime in 2015. These proceedings cover a selection of recent results produced by the Tevatron and LHC experiments.