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We report new time-resolved laser-induced fluorescence lifetime measurements for 22 highly excited even-parity levels in singly ionized yttrium (Y II). To populate these levels belonging to the configurations 4d6s, 5s6s 4d5d, 5p2, 4d7s and 4d6d, a two-step laser excitation technique was used. Our previous pseudo-relativistic Hartree-Fock model (Biémont et al. 2011) was improved by extending the co

This note provides an interim summary of the current recommendations of thePDF4LHC working group for the use of parton distribution functions (PDFs)and of PDF uncertainties at the LHC, for cross section and cross section uncer-tainty calculations. It also contains a succinct user guideto the computation ofPDFs, uncertainties and correlations using available PDF sets.A companion note (the PDF4LHC W

If a leptoquark is produced at HERA as a narrow resonance, various effects tend to broaden the measurable mass distribution considerably. These effects are discussed here, with special emphasis on initial- and final-state QCD radiation. A proper understanding is important to assess the significance of data and to devise strategies for better mass reconstruction.

Several distinct color flow topologies are possible in multiparton configurations. A method is proposed to find the correct topology, based on a minimization of the total transverse momentum of produced particles. This method is studied for three-jet [Formula presented] and four-jet [Formula presented] events. It is shown how the basic picture is smeared, especially by parton-shower activity. The

All currently available QCD-inspired models/Monte Carlos for the event structure in high-p T physics are described. Included is information on hard interactions, initial and final state radiation, structure functions, beam jets and fragmentation. Results from a number of comparative Monte Carlo runs are presented, which help to illuminate how the physics content in Monte Carlos may be tested. Spec

Phenomenological models of multiparticle production have become increasingly important for the interpretation of experimental data in high energy physics. The evolution of these models fills a gap left open by the present limited theoretical understanding of the hadronization process, i.e. the transformation of outgoing colored partons into color singlet hadrons. The three main schools of thought,

The present status of Chiral Perturbation Theory in the meson sector is discussed concentrating on recent developments. This write-up contains short discussions on a listing of a few historical papers, the principles behind ChPT, two-flavour ChPT including some comments about the Pion polarizability, three-flavour ChPT with a discussion of the recently found relations as tests of ChPT and prelimin