Browsing by Issue Date, starting with "2015-08-26"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Angular distributions in $t \overline{t}H(H → b \overline{b})$ reconstructed events at the LHCPublication . Amor dos Santos, S. P.; Araque, J.P.; Cantrill, R.; Castro, N.F.; Fiolhais, M.C.N.; Frederix, R.; Gonçalo, R.; Martins, R.; Santos, R.; Silva, J.; Onofre, A.; Peixoto, H.; Reigoto, A.The associated production of a Higgs boson and a top-quark pair, $t{\bar t} H$, in proton-proton collisions is addressed in this paper for a center of mass energy of 13TeV at the LHC. Dileptonic final states of $t{\bar t}H$ events with two oppositely charged leptons and four jets from the decays $t\rightarrow bW^+ \rightarrow b \ell^+\nu_\ell$, $\bar{t}\rightarrow \bar{b}W^- \rightarrow \bar{b} \ell^-\bar{\nu}_\ell$ and $h\rightarrow b\bar{b}$, are used. Signal events, generated with MadGraph5_aMC@NLO, are fully reconstructed by applying a kinematic fit. New angular distributions of the decay products as well as angular asymmetries are explored in order to improve discrimination of $t{\bar t} H$ signal events over the dominant irreducible background contribution, $t{\bar t}b{\bar b}$. Even after the full kinematic fit reconstruction of the events, the proposed angular distributions and asymmetries are still quite different in the $t\bar{t}H$ signal and the dominant background ($t\bar{t}b\bar{b}$).
- Measurement of the Cosmic Ray Spectrum above 4 $\times$ 10$^{18}$ eV Using Inclined Events Detected with the Pierre Auger ObservatoryPublication . Pierre Auger collaboration (463 authors); Abreu, Pedro; Andringa, Sofia; Assis, Pedro; Blanco, Alberto; Brogueira, Pedro; Cazon, Lorenzo; Conceição, Ruben; Diogo, Francisco; Espadanal, Joao; Lopes, Luis; Pimenta, Mário; Santos, Eva; Sarmento, Raul; Tomé, BernardoA measurement of the cosmic-ray spectrum for energies exceeding 4×10(18) eV is presented, which is based on the analysis of showers with zenith angles greater than 60° detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above 5.3×10(18) eV, the ``ankle'', the flux can be described by a power law E(−)(γ) with index γ=2.70 ± 0.02 (stat) ± 0.1 (sys) followed by a smooth suppression region. For the energy (E(s)) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find E(s)=(5.12±0.25 (stat)(+1.0)(−)(1.2) (sys))×10(19) eV.
- Measurements of the Total and Differential Higgs Boson Production Cross Sections Combining the H→γγ and H→ZZ*→4ℓ Decay Channels at $\sqrt{s}$=8 TeV with the ATLAS DetectorPublication . ATLAS collaboration (2822 authors); Aguilar-Saavedra, Juan Antonio; Amor Dos Santos, Susana Patricia; Anjos, Nuno; Araque, Juan Pedro; Cantrill, Robert; Carvalho, João; Castro, Nuno Filipe; Conde Muiño, Patricia; Da Cunha Sargedas De Sousa, Mario Jose; Fiolhais, Miguel; Galhardo, Bruno; Gomes, Agostinho; Gonçalo, Ricardo; Jorge, Pedro; Lopes, Lourenco; Machado Miguens, Joana; Maio, Amélia; Maneira, José; Onofre, António; Palma, Alberto; Pedro, Rute; Pina, João Antonio; Pinto, Belmiro; Santos, Helena; Saraiva, João; Silva, José; Tavares Delgado, Ademar; Veloso, Filipe; Wolters, HelmutMeasurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb-1 of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of s=8 TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H→γγ and H→ZZ*→4ℓ event yields, which are combined accounting for detector efficiencies, fiducial acceptances, and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be σpp→H=33.0±5.3 (stat)±1.6 (syst) pb. The measurements are compared to state-of-the-art predictions.