Formation lengths of hadrons in lepto-production

The average formation lengths of the hadrons produced during the deep inelastic scattering (DIS) of leptons on protons are studied in the framework of the symmetric Lund model. It is shown that these formation lengths essentially depend on the electric charges of the hadron. For electro-production and charged current (CC) neutrino-production, the average formation lengths of positively charged particles are larger than those of negatively charged antiparticles. This situation is reversed for CC antineutrino-production. In all the mentioned cases, the main mechanism is the direct production of hadrons. The additional mechanism of hadron production, through the decay of resonances, is essential only for pions and leads to a decrease in the average formation lengths.Comment: 6 pages, 2 figure

Did BICEP2 see vector modes? First B-mode constraints on cosmic defects

Scaling networks of cosmic defects, such as strings and textures, actively generate scalar, vector and tensor metric perturbations throughout the history of the universe. In particular, {\em vector} modes sourced by defects are an efficient source of the CMB B-mode polarization. We use the recently released BICEP2 and POLARBEAR B-mode polarization spectra to constrain properties of a wide range of different types of cosmic strings networks. We find that in order for strings to provide a satisfactory fit on their own, the effective inter-string distance needs to be extremely large -- spectra that fit the data best are more representative of global strings and textures. When a local string contribution is considered together with the inflationary B-mode spectrum, the fit is improved. We discuss implications of these results for theories that predict cosmic defects.Comment: 5 pages, 3 figures; a reference added; matches the version published in Phys Rev Let

Decidability of the Clark's Completion Semantics for Monadic Programs and Queries

There are many different semantics for general logic programs (i.e. programs that use negation in the bodies of clauses). Most of these semantics are Turing complete (in a sense that can be made precise), implying that they are undecidable. To obtain decidability one needs to put additional restrictions on programs and queries. In logic programming it is natural to put restrictions on the underlying first-order language. In this note we show the decidability of the Clark's completion semantics for monadic general programs and queries. To appear in Theory and Practice of Logic Programming (TPLP