[en] We discuss the flavor asymmetry and the strangeness content of the proton in an unquenched quark model. It is shown that the inclusion of hadron loops leads automatically to an excess of d-bar over ū, but gives very small contributions to the strange magnetic moment and strangeness radius of the proton, both of which are in agreement with experimental data.

[en] Even though physicists have established the presumed correct theory of strong interactions, QCD, calculation of the partonic structure of hadrons remains beyond our present capability. Those of us who measure these partonic distributions are anxious to learn at this workshop, of the progress being made in carrying out the theory in the light cone reference frame. In this talk I will present results from a direct measurement (FNAL/E866/BUSEA) of the relative d-bar,u-bar content of nucleon sea and discuss perspectives on the origin of the observed flavor asymmetry. (AIP)

[en] Experiment E866, conducted at the Fermi National Accelerator Laboratory, is a high statistics experiment to measure u-bar(x)/d-bar(x) in the proton over a wide range of x. Preliminary results are shown for the ratio of the Drell-Yan cross sections σ^pd/2σ^pp. These results confirm the conclusions of both the NMC and NA51 collaborations that there is an u-bar/d-bar asymmetry in the proton sea

[en] In this talk we present recent next-to-leading order results relevant for LHC phenomenology obtained with the GOLEM method. After reviewing the status of this Feynman diagrammatic approach for multi-leg one-loop calculations we discuss three applications: the loop-induced process gg→Z*Z* and the virtual corrections to the five and six point processes qq→ZZg and uu-bar →ss-bar cc-bar . We demonstrate that our method leads to representations of such amplitudes which allow for efficient phase space integration. In this context we propose a reweighting technique of the leading order unweighted events by local K-factors

[en] The light flavor antiquark distributions of the nucleon sea are calculated in the effective chiral quark model and compared with experimental results. The contributions of the flavor-symmetric sea-quark distributions and the nuclear EMC effect are taken into account to obtain the ratio of Drell-Yan cross sections σ^pD/2σ^pp, which can match well with the results measured in the FermiLab E866/NuSea experiment. The calculated results also match the anti d(x)- anti u(x) measured in different experiments, but unmatch the behavior of anti d(x)/ anti u(x) derived indirectly from the measurable quantity σ^pD/2σ^pp by the FermiLab E866/NuSea Collaboration at large x. We suggest to measure again anti d(x)/ anti u(x) at large x from precision experiments with careful treatment of the experimental data. We also propose an alternative procedure for experimental data treatment. (orig.)

[en] The NuSea (E866) experiment at Fermilab has been using Drell-Yan scattering to study the u-bar/d-bar quark content of the proton by comparing of the yield between liquid hydrogen and liquid deuterium targets. A preliminary ratio of Drell-Yan yields, σ^pd/2σ^pp as a function of x is shown. This data confirms the previous indications from the NMC and NA51 experiments that u-bar≠d-bar

[en] Lepton flavour violation is not allowed by the Standard Model (SM), yet it has been observed in neutrinos. The physics responsible for neutrino oscillations and masses is still unknown and it may allow charged lepton flavour violation (CLFV). Evidence for CLFV processes, strongly suppressed according to the SM, would shed light on the nature of New Physics. Studies towards a search for CLFV will be presented using 13 TeV data collected between 2015 and 2017 by the ATLAS detector. The analysis investigates the decay of a top quark into a pair of opposite-sign different-flavour leptons and a up-type quark. The search, never performed before in this channel, benefits from the clear signature and the large top-quark pair production cross section in proton-proton collision at the Large Hadron Collider. The theoretical description is given in the framework of an effective field theory, allowing for a model-independent search.

[en] I present results of the NLO corrections for u+u to b+b+d+d in massless QCD. Along with this calculation a Feynman diagram based, general matrix element generator for one-loop amplitudes (GOLEM) is being developed, the status of which is also outlined in my talk. (author)

[en] The current status of carlomat, a program for automatic computation of the lowest order cross sections of multiparticle reactions is described, the results of comparisons with other multipurpose Monte Carlo programs are shown and some new results on e⁺e^-→bb-bar bb-bar ud-bar du-bar are presented

[en] The amount of u-bar and that of d-bar in the proton were assumed to be the same based on the flavor symmetry. However, previous experiments found that d-bar is dominant in the proton. In particular, d-bar/u-bar is as asymmetric as 1.7 at Bjorken x ∼ 0.2. The SeaQuest experiment at Fermilab aims to measure the flavor asymmetry at higher x region (0.15 < x < 0.45). The ratio d-bar/u-bar is derived from the cross section ratio of proton-deuteron to proton-proton Drell-Yan processes. We analyzed the data taken in 2015 and obtained the preliminary result. We found that the d-bar/u-bar > 1 at higher x. (author)