Browsing by Author "CMS collaboration (2307 authors)"
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- Measurement of differential cross sections for Z boson production in association with jets in proton-proton collisions at $\sqrt{s} =$ 13 TeVPublication . CMS collaboration (2307 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Galinhas, Bruno; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Seixas, Joao; Strong, Giles; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, PasqualeThe production of a ${\text {Z}}$ boson, decaying to two charged leptons, in association with jets in proton-proton collisions at a centre-of-mass energy of 13 $\,\text {TeV}$ is measured. Data recorded with the CMS detector at the LHC are used that correspond to an integrated luminosity of 2.19 $\,\text {fb}^\text {-1}$ . The cross section is measured as a function of the jet multiplicity and its dependence on the transverse momentum of the ${\text {Z}}$ boson, the jet kinematic variables (transverse momentum and rapidity), the scalar sum of the jet momenta, which quantifies the hadronic activity, and the balance in transverse momentum between the reconstructed jet recoil and the ${\text {Z}}$ boson. The measurements are compared with predictions from four different calculations. The first two merge matrix elements with different parton multiplicities in the final state and parton showering, one of which includes one-loop corrections. The third is a fixed-order calculation with next-to-next-to-leading order accuracy for the process with a ${\text {Z}}$ boson and one parton in the final state. The fourth combines the fully differential next-to-next-to-leading order calculation of the process with no parton in the final state with next-to-next-to-leading logarithm resummation and parton showering.
- Observation of top quark pairs produced in association with a vector boson in pp collisions at $ \sqrt{s}=8 $ TeVPublication . CMS collaboration (2307 authors); Hollar, Jonathan; Calpas, Betty; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Leonardo, Nuno; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoMeasurements of the cross sections for top quark pairs produced in association with a W or Z boson are presented, using 8 TeV pp collision data corresponding to an integrated luminosity of 19.5 fb$^{−1}$, collected by the CMS experiment at the LHC. Final states are selected in which the associated W boson decays to a charged lepton and a neutrino or the Z boson decays to two charged leptons. Signal events are identified by matching reconstructed objects in the detector to specific final state particles from $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ or $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ decays. The $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ cross section is measured to be 382$_{− 102}^{+ 117}$ fb with a significance of 4.8 standard deviations from the background-only hypothesis. The $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ cross section is measured to be 242$_{− 55}^{+ 65}$ fb with a significance of 6.4 standard deviations from the background-only hypothesis. These measurements are used to set bounds on five anomalous dimension-six operators that would affect the $ \mathrm{t}\overline{\mathrm{t}}\mathrm{W} $ and $ \mathrm{t}\overline{\mathrm{t}}\mathrm{Z} $ cross sections.
- Search for a charged Higgs boson in pp collisions at $ \sqrt{s}=8 $ TeVPublication . CMS collaboration (2307 authors); Hollar, Jonathan; Calpas, Betty; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Leonardo, Nuno; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoA search for a charged Higgs boson is performed with a data sample corresponding to an integrated luminosity of 19.7 ± 0.5 fb$^{−1}$ collected with the CMS detector in proton-proton collisions at $ \sqrt{s}=8 $ ,TeV. The charged Higgs boson is searched for in top quark decays for m$_{H}$± < m$_{t}$ − m$_{b}$, and in the direct production pp → t(b)H$^{±}$ for m$_{H}$± > m$_{t}$ − m$_{b}$. The H$^{±}$ → τ$^{±}$ ν$_{τ}$ and H$^{±}$ → tb decay modes in the final states τ$_{h}$+jets, μτ$_{h}$, ℓ+jets, and ℓℓ’ (ℓ =e, μ) are considered in the search. No signal is observed and 95% confidence level upper limits are set on the charged Higgs boson production. A model-independent upper limit on the product branching fraction $ \mathrm{\mathcal{B}}\left(\mathrm{t}\to {\mathrm{H}}^{\pm}\mathrm{b}\right)\mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to {\tau}^{\pm }{\nu}_{\tau}\right)=1.2-0.15\% $ is obtained in the mass range m$_{H}$± = 80–160 GeV, while the upper limit on the cross section times branching fraction $ \sigma \left(\mathrm{pp}\to \mathrm{t}\left(\mathrm{b}\right){\mathrm{H}}^{\pm}\right)\mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to\ {\tau}^{\pm }{\nu}_{\tau}\right)=0.38-0.025 $ pb is set in the mass range m$_{H}$+ = 180–600 GeV. Here, σ(pp → t(b)H$^{±}$) stands for the cross section sum $ \sigma \left(\mathrm{pp}\to \overline{\mathrm{t}}\left(\mathrm{b}\right){\mathrm{H}}^{+}\right)+\sigma \left(\mathrm{pp}\to \mathrm{t}\left(\overline{\mathrm{b}}\right){\mathrm{H}}^{-}\right) $ . Assuming $ \mathrm{\mathcal{B}}\left({\mathrm{H}}^{\pm}\to \mathrm{t}\mathrm{b}\right)=1 $ , an upper limit on σ(pp → t(b)H$^{±}$) of 2.0–0.13 pb is set for m$_{H}$± = 180–600 GeV. The combination of all considered decay modes and final states is used to set exclusion limits in the m$_{H}$±−tan β parameter space in different MSSM benchmark scenarios.
- Search for Anomalous Single Top Quark Production in Association with a Photon in $pp$ Collisions at $ \sqrt{s}=8 $ TeVPublication . CMS collaboration (2307 authors); Hollar, Jonathan; Calpas, Betty; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Leonardo, Nuno; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoThe result of a search for flavor changing neutral currents (FCNC) through single top quark production in association with a photon is presented. The study is based on proton-proton collisions at a center-of-mass energy of 8 TeV using data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fb$^{−1}$. The search for tγ events where t → Wb and W → μν is conducted in final states with a muon, a photon, at least one hadronic jet with at most one being consistent with originating from a bottom quark, and missing transverse momentum. No evidence of single top quark production in association with a photon through a FCNC is observed. Upper limits at the 95% confidence level are set on the tuγ and tcγ anomalous couplings and translated into upper limits on the branching fraction of the FCNC top quark decays: ℬ(t → uγ) < 1.3 × 10$^{− 4}$ and ℬ(t → cγ) < 1.7 × 10$^{− 3}$. Upper limits are also set on the cross section of associated tγ production in a restricted phase-space region. These are the most stringent limits currently available.
- Search for the associated production of a Higgs boson with a single top quark in proton-proton collisions at $ \sqrt{s}=8 $ TeVPublication . CMS collaboration (2307 authors); Hollar, Jonathan; Calpas, Betty; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Leonardo, Nuno; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoThis paper presents the search for the production of a Higgs boson in association with a single top quark (tHq), using data collected in proton-proton collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb$^{−1}$. The search exploits a variety of Higgs boson decay modes resulting in final states with photons, bottom quarks, and multiple charged leptons, including tau leptons, and employs a variety of multivariate techniques to maximize sensitivity to the signal. The analysis is optimized for the opposite sign of the Yukawa coupling to that in the standard model, corresponding to a large enhancement of the signal cross section. In the absence of an excess of candidate signal events over the background predictions, 95% confidence level observed (expected) upper limits on anomalous tHq production are set, ranging between 600 (450) fb and 1000 (700) fb depending on the assumed diphoton branching fraction of the Higgs boson. This is the first time that results on anomalous tHq production have been reported.
- Search for the standard model Higgs boson produced through vector boson fusion and decaying to $b \overline{b}$Publication . CMS collaboration (2307 authors); Hollar, Jonathan; Calpas, Betty; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, Joao; Leonardo, NunoA first search is reported for a standard model Higgs boson (H) that is produced through vector boson fusion and decays to a bottom-quark pair. Two data samples, corresponding to integrated luminosities of 19.8 fb-1 and 18.3 fb−1 of proton-proton collisions at s=8 TeV were selected for this channel at the CERN LHC. The observed significance in these data samples for a H→bb¯ signal at a mass of 125 GeV is 2.2 standard deviations, while the expected significance is 0.8 standard deviations. The fitted signal strength μ=σ/σSM=2.8-1.4+1.6. The combination of this result with other CMS searches for the Higgs boson decaying to a b-quark pair yields a signal strength of 1.0±0.4, corresponding to a signal significance of 2.6 standard deviations for a Higgs boson mass of 125 GeV.