Browsing by Author "CMS collaboration (2146 authors)"
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- Measurement of electroweak production of two jets in association with a Z boson in proton-proton collisions at $\sqrt{s}=8\,\text {TeV}$Publication . CMS collaboration (2146 authors); Hollar, Jonathan; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Varela, Joao; Vischia, Pietro; Lloret Iglesias, Lara; David Tinoco Mendes, Andre; Musella, Pasquale; Silva, Pedro; Pela, Joao; Leonardo, NunoThe purely electroweak (EW) cross section for the production of two jets in association with a Z boson, in proton–proton collisions at $\sqrt{s}=8\,\text {TeV}$ , is measured using data recorded by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 19.7 $\,\text {fb}^\text {-1}$ . The electroweak cross section for the $\ell \ell \mathrm {jj}$ final state (with $\ell = \mathrm {e}$ or $\mu $ and j representing the quarks produced in the hard interaction) in the kinematic region defined by $M_{\ell \ell } >50$ $\,\text {GeV}$ , $M_\mathrm {jj} >120$ $\,\text {GeV}$ , transverse momentum $p_\mathrm {T j}> 25$ $\,\text {GeV}$ , and pseudorapidity $|\eta _\mathrm {j} |< 5$ , is found to be $\sigma _\mathrm {EW}(\ell \ell \mathrm {jj})=174 \pm 15\,\text {(stat)}\pm 40\,\text {(syst)}\text {\,fb}$ , in agreement with the standard model prediction. The associated jet activity of the selected events is studied, in particular in a signal-enriched region of phase space, and the measurements are found to be in agreement with QCD predictions.
- Measurement of the inclusive 3-jet production differential cross section in proton–proton collisions at 7 TeV and determination of the strong coupling constant in the TeV rangePublication . CMS collaboration (2146 authors); Hollar, Jonathan; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Musella, Pasquale; Silva, Pedro; Pela, Joao; Leonardo, NunoThis paper presents a measurement of the inclusive 3-jet production differential cross section at a proton–proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5 $\,\mathrm{fb}^{-1}$ collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445–3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant $\alpha _\mathrm {S}$ is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of $\alpha _S(M_\mathrm{Z}) = 0.1171 \pm 0.0013\,\text {(exp)} \,^{+0.0073-0.0047}\,\text {(theo)} $ .
- Search for resonant pair production of Higgs bosons decaying to two bottom quark–antiquark pairs in proton–proton collisions at 8 TeVPublication . CMS collaboration (2146 authors); Hollar, Jonathan; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, Joao; Leonardo, NunoA model-independent search for a narrow resonance produced in proton–proton collisions at s=8 TeV and decaying to a pair of 125 GeV Higgs bosons that in turn each decays into a bottom quark–antiquark pair is performed by the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 17.9 fb −1 . No evidence for a signal is observed. Upper limits at a 95% confidence level on the production cross section for such a resonance, in the mass range from 270 to 1100 GeV, are reported. Using these results, a radion with decay constant of 1 TeV and mass from 300 to 1100 GeV, and a Kaluza–Klein graviton with mass from 380 to 830 GeV are excluded at a 95% confidence level.
- Search for Standard Model Production of Four Top Quarks in the Lepton + Jets Channel in pp Collisions at $\sqrt{s}$ = 8 TeVPublication . CMS collaboration (2146 authors); Hollar, Jonathan; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Lloret Iglesias, Lara; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Musella, Pasquale; Silva, Pedro; Pela, Joao; Leonardo, NunoA search is presented for standard model (SM) production of four top quarks $ \left(t\overline{t}t\overline{t}\right) $ in pp collisions in the lepton + jets channel. The data correspond to an integrated luminosity of 19.6 fb$^{−1}$ recorded at a centre-of-mass energy of 8 TeV with the CMS detector at the CERN LHC. The expected cross section for SM $ t\overline{t}t\overline{t} $ production is $ {\sigma}_{t\overline{t}t\overline{t}}^{\mathrm{SM}}\approx 1\,\mathrm{f}\mathrm{b} $ . A combination of kinematic reconstruction and multivariate techniques is used to distinguish between the small signal and large background. The data are consistent with expectations of the SM, and an upper limit of 32 fb is set at a 95% confidence level on the cross section for producing four top quarks in the SM, where a limit of 32 ± 17 fb is expected.
- Searches for heavy Higgs bosons in two-Higgs-doublet models and for $t→ch$ decay using multilepton and diphoton final states in $pp$ collisions at 8 TeVPublication . CMS collaboration (2146 authors); Hollar, Jonathan; Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Nguyen, Federico; Rodrigues Antunes, Joao; Seixas, Joao; Varela, Joao; Vischia, Pietro; Lloret Iglesias, Lara; David Tinoco Mendes, Andre; Musella, Pasquale; Silva, Pedro; Pela, Joao; Leonardo, NunoSearches are presented for heavy scalar ($\mathrm{H}$) and pseudoscalar ($\mathrm{A}$) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of $\mathrm{p}\mathrm{p}$ collisions collected with the CMS experiment at the LHC at a center-of-mass energy of $\sqrt{s} = 8~\mathrm{TeV}$ and corresponding to an integrated luminosity of $19.5~\mathrm{fb}^{-1}$. The decays $\mathrm{H} \rightarrow \mathrm{h} \mathrm{h}$ and $\mathrm{A} \rightarrow \mathrm{Z} \mathrm{h}$, where $\mathrm{h}$ denotes an SM-like Higgs boson, lead to events with three or more isolated charged leptons or with a photon pair accompanied by one or more isolated leptons. The search results are presented in terms of the $\mathrm{H}$ and $\mathrm{A}$ production cross sections times branching fractions and are further interpreted in terms of 2HDM parameters. We place 95% CL cross section upper limits of approximately $7~\mathrm{pb}$ on $\sigma \mathcal{B}$ for $\mathrm{H} \rightarrow \mathrm{h} \mathrm{h}$ and $2~\mathrm{pb}$ for $\mathrm{A} \rightarrow \mathrm{Z} \mathrm{h}$. Also presented are the results of a search for the rare decay of the top quark that results in a charm quark and an SM Higgs boson, $\mathrm{t} \rightarrow \mathrm{c} \mathrm{h}$, the existence of which would indicate a nonzero flavor-changing Yukawa coupling of the top quark to the Higgs boson. We place a 95% CL upper limit of 0.56% on $\mathcal{B}(\mathrm{t} \rightarrow \mathrm{c} \mathrm{h})$.