Abstract: We present the detailed derivation of the longitudinal part of the three-gluon vertex from the Slavnov-Taylor identities that it satisfies, by means of a nonperturbative implementation of the Ball-Chiu construction; the latter, in its original form, involves the inverse gluon propagator, the ghost dressing function, and certain form factors of the ghost-gluon kernel. The main conceptual subtlety that renders this endeavor nontrivial is the infrared finiteness of the gluon propagator, and the resulting need to separate the vertex into two pieces, one that is intimately connected with the emergence of a gluonic mass scale, and one that satisfies the original set of Slavnov-Taylor identities, but with the inverse gluon propagator replaced by its “kinetic” term. The longitudinal form factors obtained by this construction are presented for arbitrary Euclidean momenta, as well as special kinematic configurations, parametrized by a single momentum. A particularly preeminent feature of the components comprising the tree-level vertex is their considerable suppression for momenta below 1 GeV, and the appearance of the characteristic “zero-crossing” in the vicinity of 100-200 MeV. Special combinations of the form factors derived with this method are compared with the results of recent large-volume lattice simulations, and are found to capture faithfully the rather complicated curves formed by the data. A similar comparison with results obtained from Schwinger-Dyson equations reveals a fair overall agreement, but with appreciable differences at intermediate energies. A variety of issues related to the distribution of the pole terms responsible for the gluon mass generation are discussed in detail, and their impact on the structure of the transverse parts is elucidated. In addition, a brief account of several theoretical and phenomenological possibilities involving these newly acquired results is presented.

Abstract: We have made a study of the J/psi -> eta'h(1), eta h(1) [with h(1) being /11(1170) and h(1)(1380)1 and P/psi ->pi(0)b(1) 171(1235)(0) assuming the axial vector mesons to be dynamically generated from the pseudoscalar-vectormeson interaction. We have taken the needed input from previous studies of the J/psi -> phi pi pi, omega pi pi reactions. We obtain fair agreement with experimental data and provide an explanation on why the recent experiment on J/psi -> eta'h(1)(1380), h(1)(1380) -> K*K-+(-) + c.c. observed in the K+K-pi(0) mode observes the peak of the h(1)(1380) at a higher energy than its nominal mass.

Abstract: A measurement of the associated production of a top-quark pair (t (t) over bar) with a vector boson (W, Z) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented, using 36.1 fb(-1) of integrated luminosity collected by the ATLAS detector at the Large Hadron Collider. Events are selected in channels with two same- or opposite-sign leptons (electrons or muons), three leptons or four leptons, and each channel is further divided into multiple regions to maximize the sensitivity of the measurement. The t (t) over barZ and t (t) over barW production cross sections are simultaneously measured using a combined fit to all regions. The best-fit values of the production cross sections are sigma(t (t) over barZ) = 0.95 +/- 0.08(stat )+/- 0.10(syst) pb and sigma(t (t) over barW) = 0.87 +/- 0.13(stat) +/- 0.14(syst) pb in agreement with the Standard Model predictions. The measurement of the t (t) over barZ cross section is used to set constraints on effective field theory operators which modify the t (t) over barZ vertex.

Abstract: A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb(-1) of protonproton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks (R-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived R-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop R-hadrons, as well as staus and charginos of 2000, 1250, 1340, 430, and 1090 GeV, respectively.

Abstract: Proton decay is usually discussed in the context of grand unified theories. However, as is well known, in the standard model effective theory proton decay appears in the form of higher-dimensional non-renormalizable operators. Here, we study systematically the one-loop decomposition of the d = 6 B + L violating operators. We exhaustively list the possible one-loop ultraviolet completions of these operators and discuss that, in general, two distinct classes of models appear. Models in the first class need an additional symmetry in order to avoid tree-level proton decay. These models necessarily contain a neutral particle, which could act as a dark matter candidate. For models in the second class the loop contribution dominates automatically over the tree-level proton decay, without the need for additional symmetries. We also discuss possible phenomenology of two example models, one from each class, and their possible connections to neutrino masses, LHC searches and dark matter.