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: A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of root s = 13 TeV corresponding to an integrated luminosity of 36.1 fb(-1). Events consistent with top-quark pair production and the fully hadronic decay mode of the top quarks are selected by requiring multiple high transverse momentum jets including those containing b-hadrons. Two analysis techniques, exploiting dedicated top-quark pair reconstruction in different kinematic regimes, are used to optimize the search sensitivity to new hypothetical particles over a wide mass range. The invariant mass distribution of the two reconstructed top-quark candidates is examined for resonant production of new particles with various spins and decay widths. No significant deviation from the Standard Model prediction is observed and limits are set on the production cross-section times branching fraction for new hypothetical Z' bosons, dark-matter mediators, Kaluza-Klein gravitons and Kaluza-Klein gluons. By comparing with the predicted production cross sections, the Z' boson in the topcolor-assisted-technicolor model is excluded for masses up to 3.1-3.6 TeV, the dark-matter mediators in a simplified framework are excluded in the mass ranges from 0.8 to 0.9 TeV and from 2.0 to 2.2 TeV, and the Kaluza-Klein gluon is excluded for masses up to 3.4 TeV, depending on the decay widths of the particles.

Abstract: It is well known that a quantized two-dimensional Weyl fermion coupled to gravity spoils general covariance and breaks the covariant conservation of the energy-momentum tensor. In this brief article, we point out that the quantum conservation of the momentum can also fail in flat spacetime, provided the Weyl fermion is coupled to a time-varying homogeneous electric field. This signals a quantum anomaly of the space-translation symmetry, which has not been highlighted in the literature so far.

Abstract: A search for charge-parity (CP) violation in Cabibbo-suppressed D-s(+) -> K-S(0)pi(+), D+ -> (KSK+)-K-0, and D+ -> phi pi(+) decays is reported using proton-proton collision data, corresponding to an integrated luminosity of 3.8 fb(-1), collected at a center-of-mass energy of 13 TeV with the LHCb detector. High-yield samples of kinematically and topologically similar Cabibbo-favored D-(s())+ decays are analyzed to subtract nuisance asymmetries due to production and detection effects, including those induced by CP violation in the neutral kaon system. The results are A(CP)(D-s(+) -> K-S(0)pi(+)) = (1.3 +/- 1.9 +/- 0.5) x 10(-3), A(CP)(D+ -> (KSK+)-K-0) = (-0.09 +/- 0.65 +/- 0.48) x 10(-3), A(CP)(D+ -> phi pi(+)) = (0.05 +/- 0.42 +/- 0.29) x 10(-3), where the first uncertainties are statistical and the second systematic. They are the most precise measurements of these quantities to date, and are consistent with CP symmetry. A combination with previous LHCb measurements, based on data collected at 7 and 8 TeV, is also reported.

Abstract: We study the implications for bc=c(2595) and c(2625)] decays that can be deduced from heavy quark spin symmetry (HQSS). Identifying the odd parity c(2595) and c(2625) resonances as HQSS partners, with total angular momentum-parity jqP=1- for the light degrees of freedom, we find that the ratios (bc(2595)-)/(bc(2625)-) and (bc(2595)) agree, within errors, with the experimental values given in the Review of Particle Physics. We discuss how future, and more precise, measurements of the above branching fractions could be used to shed light into the inner HQSS structure of the narrow c(2595) odd-parity resonance. Namely, we show that such studies would constrain the existence of a sizable jqP</mml:msubsup>=0- component in its wave-function, and/or of a two-pole pattern, in analogy to the case of the similar (1405) resonance in the strange sector, as suggested by most of the approaches that describe the c(2595) as a hadron molecule. We also investigate the lepton flavor universality ratios R[c]=B( may be affected by a new source of potentially large systematic errors if there are two) poles.