b-tagging

Abstract: We present a measurement of the tt production cross section using events with one charged lepton and jets from pp collisions at a center-of-mass energy of 1.96 TeV. In these events, heavy flavor quarks from top quark decay are identified with a secondary vertex tagging algorithm. From 162 pb{sup -1} of data collected by the Collider Detector at Fermilab, a total of 48 candidate events are selected, where 13.5{+-}1.8 events are expected from background contributions. We measure a tt production cross section of 5.6{sub -1.1}{sup +1.2}(stat.){sub -0.6}{sup +0.9}(syst.) pb.

Abstract: An inclusive search for the standard model Higgs boson (H) produced with large transverse momentum (p_T) and decaying to a bottom quark-antiquark pair (bb) is performed using a data set of pp collisions at √s = 13 TeV collected with the CMS experiment at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb^(−1). A highly Lorentz-boosted Higgs boson decaying to bb is reconstructed as a single, large radius jet, and it is identified using jet substructure and dedicated b tagging techniques. The method is validated with Z → bb decays. The Z → bb process is observed for the first time in the single-jet topology with a local significance of 5.1 standard deviations (5.8 expected). For a Higgs boson mass of 125 GeV, an excess of events above the expected background is observed (expected) with a local significance of 1.5 (0.7) standard deviations. The measured cross section times branching fraction for production via gluon fusion of H → bb with reconstructed p_T > 450 GeV and in the pseudorapidity range −2.5 < η < 2.5 is 74 ± 48 (stat)^(+17)_(−10)(syst) fb, which is consistent within uncertainties with the standard model prediction.

Abstract: Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron p-pbar collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.

Abstract: This Note describes a b-tagging algorithm based on inclusive secondary vertex reconstruction in jets. Several topological and kinematical secondary vertex related variables as well as information from track impact parameters are combined into a single tagging variable to discriminate between jets originating from b-quarks and those from other sources. The performance of the algorithm is studied for several event topologies and as a function of jet kinematics. Effects of an imperfectly aligned tracking detector on the performance are also investigated.