Browsing by Author "CMS collaboration (2232 authors)"
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- Evidence for the direct decay of the 125 GeV Higgs boson to fermionsPublication . CMS collaboration (2232 authors); Hollar, Jonathan; Nayak, Aruna; Calpas, Betty; 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 discovery of a new boson with a mass of approximately 125 GeV in 2012 at the LHC has heralded a new era in understanding the nature of electroweak symmetry breaking and possibly completing the standard model of particle physics. Since the first observation in decays to gamma gamma, WW, and ZZ boson pairs, an extensive set of measurements of the mass and couplings to W and Z bosons, as well as multiple tests of the spin-parity quantum numbers, have revealed that the properties of the new boson are consistent with those of the long-sought agent responsible for electroweak symmetry breaking. An important open question is whether the new particle also couples to fermions, and in particular to down-type fermions, since the current measurements mainly constrain the couplings to the up-type top quark. Determination of the couplings to down-type fermions requires direct measurement of the corresponding Higgs boson decays, as recently reported by the CMS experiment in the study of Higgs decays to bottom quarks and tau leptons. In this paper we report the combination of these two channels which results, for the first time, in strong evidence for the direct coupling of the 125 GeV Higgs boson to down-type fermions, with an observed significance of 3.8 standard deviations, when 4.4 are expected.
- Measurement of the inclusive energy spectrum in the very forward direction in proton-proton collisions at $ \sqrt{s}=13 $ TeVPublication . CMS collaboration (2232 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Ferreira Parracho, Pedro Guilherme; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Rodrigues Antunes, Joao; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoThe differential cross section for inclusive particle production as a function of energy in proton-proton collisions at a center-of-mass energy of 13 TeV is measured in the very forward region of the CMS detector. The measurement is based on data collected with the CMS apparatus at the LHC, and corresponds to an integrated luminosity of 0.35 inverse microbarns. The energy is measured in the CASTOR calorimeter, which covers the pseudorapidity region -6.6 < eta < -5.2. The results are given as a function of the total energy deposited in CASTOR, as well as of its electromagnetic and hadronic components. The spectra are sensitive to the modeling of multiparton interactions in pp collisions, and provide new constraints for hadronic interaction models used in collider and in high energy cosmic ray physics.
- Search for electroweak production of charginos and neutralinos in WH events in proton-proton collisions at $ \sqrt{s}=13 $ TeVPublication . CMS collaboration (2232 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, PasqualeResults are reported from a search for physics beyond the standard model in proton-proton collision events with a charged lepton (electron or muon), two jets identified as originating from a bottom quark decay, and significant imbalance in the transverse momentum. The search was performed using a data sample corresponding to 35.9 fb$^{−1}$, collected by the CMS experiment in 2016 at $ \sqrt{s}=13 $ TeV. Events with this signature can arise, for example, from the electroweak production of gauginos, which are predicted in models based on supersymmetry. The event yields observed in data are consistent with the estimated standard model backgrounds. Limits are obtained on the cross sections for chargino-neutralino $ \left({\tilde{\chi}}_1^{\pm }{\tilde{\chi}}_2^0\right) $ production in a simplified model of supersymmetry with the decays $ {\chi}_1^{\pm}\to {\mathrm{W}}^{\pm }{\tilde{\chi}}_1^0\kern0.5em \mathrm{and}\kern0.5em {\tilde{\chi}}_2^0\to \mathrm{H}{\chi}_1^0 $ . Values of $ {m}_{{\tilde{\chi}}_1^{\pm }} $ between 220 and 490 GeV are excluded at 95% confidence level by this search when the $ {\tilde{\chi}}_1^0 $ is massless, and values of $ {m}_{{\tilde{\chi}}_1^0} $ are 1 excluded up to 110 GeV for $ {m}_{{\tilde{\chi}}_1^{\pm }}\approx 450 $ GeV.
- Search for the pair production of third-generation squarks with two-body decays to a bottom or charm quark and a neutralino in proton–proton collisions at $\sqrt{s}$ = 13 TeVPublication . CMS collaboration (2232 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, PasqualeResults are presented from a search for the pair production of third-generation squarks in proton–proton collision events with two-body decays to bottom or charm quarks and a neutralino, which produces a significant imbalance in the transverse momentum. The search is performed using a sample of proton–proton collision data at s=13TeV recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 35.9 fb−1 . No statistically significant excess of events is observed beyond the expected contribution from standard model processes. Exclusion limits are set in the context of simplified models of bottom or top squark pair production. Models with bottom squark masses up to 1220 GeV are excluded at 95% confidence level for light neutralinos, and models with top squark masses of 510 GeV are excluded assuming that the mass splitting between the top squark and the neutralino is small.
- Search for third-generation scalar leptoquarks and heavy right-handed neutrinos in final states with two tau leptons and two jets in proton-proton collisions at $ \sqrt{s}=13 $ TeVPublication . CMS collaboration (2232 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, Pasquale; Pela, JoaoA search is performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying τ lepton, and at least two jets, using a $ \sqrt{s}=13 $ TeV pp collision data sample corresponding to an integrated luminosity of 12.9 fb$^{-1}$ collected with the CMS detector at the LHC in 2016. The number of observed events is found to be in agreement with the standard model prediction. A limit is set at 95% confidence level on the product of the leptoquark pair production cross section and β$^{2}$, where β is the branching fraction of leptoquark decay to a τ lepton and a bottom quark. Assuming β = 1, third-generation leptoquarks with masses below 850 GeV are excluded at 95% confidence level. An additional search based on the same event topology involves heavy right-handed neutrinos, N$_{R}$, and right-handed W bosons, W$_{R}$, arising in a left-right symmetric extension of the standard model. In this search, W$_{R}$ bosons are assumed to decay to a tau lepton and N$_{R}$ followed by the decay of the N$_{R}$ to a tau lepton and an off-shell W$_{R}$ boson. Assuming the mass of the right-handed neutrino to be half of the mass of the right-handed W boson, W$_{R}$ boson masses below 2.9 TeV are excluded at 95% confidence level. These results improve on the limits from previous searches for third-generation leptoquarks and heavy right-handed neutrinos with τ leptons in the final state.
- Search for top squark pair production in pp collisions at $ \sqrt{s}=13 $ TeV using single lepton eventsPublication . CMS collaboration (2232 authors); Nayak, Aruna; Bargassa, Pedrame; Beirão Da Cruz E Silva, Cristóvão; Calpas, Betty; Di Francesco, Agostino; Faccioli, Pietro; Gallinaro, Michele; Hollar, Jonathan; Leonardo, Nuno; Lloret Iglesias, Lara; Seixas, Joao; Toldaiev, Oleksii; Vadruccio, Daniele; Varela, Joao; Vischia, Pietro; David Tinoco Mendes, Andre; Silva, Pedro; Musella, PasqualeA search for top squark pair production in pp collisions at $ \sqrt{s}=13 $ TeV is performed using events with a single isolated electron or muon, jets, and a large transverse momentum imbalance. The results are based on data collected in 2016 with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb$^{−1}$. No significant excess of events is observed above the expectation from standard model processes. Exclusion limits are set in the context of supersymmetric models of pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. Depending on the details of the model, we exclude top squarks with masses as high as 1120 GeV. Detailed information is also provided to facilitate theoretical interpretations in other scenarios of physics beyond the standard model.