61 research outputs found
K -> pi vector form factor with N_f=2+1+1 Twisted Mass fermions
We present a lattice QCD determination of the vector form factor of the kaon
semileptonic decay K -> pi l nu which is relevant for the extraction of the CKM
matrix element |V_{us}| from experimental data. Our result is based on the
gauge configurations produced by the European Twisted Mass Collaboration with
N_f=2+1+1 dynamical fermions. We simulated at three different values of the
lattice spacing and with pion masses as small as 210 MeV. Our preliminary
estimate for the vector form factor at zero momentum transfer is
f_+(0)=0.9683(65), where the uncertainty is both statistical and systematic. By
combining our result with the experimental value of f_+(0)|V_{us}| we obtain
|V_{us}|=0.2234(16), which satisfies the unitarity constraint of the Standard
Model at the permille level
Cultural and socio-economic impacts of Mediterranean marine protected areas
Marine protected areas (MPAs) may be important for protecting the marine environment, but they may also have substantial socio-cultural impacts about which very little is currently known, or acknowledged. In the Mediterranean, few data are available on the socio-economic consequences of MPAs. The present study reviews the existing data on MPAs in Spain, France, Italy and Greece. A general increase in tourist activities in Mediterranean MPAs is evident, as are increases in the abundances of larger fish species, although there are no data indicating yields for fisheries increase adjacent to MPAs. A large increase in the number of divers and vessels using MPAs has already had impacts on natural benthic communities as a result of diver damage, mooring and the feeding of large fish by divers. Emphasis has been given in only a few MPAs to promoting public awareness of these impacts. Although the conservation of nature should be considered the fundamental objective of MPAs, neglecting their social, cultural and economic impacts has at times led to poor local consensus, if not hostility. We believe that planning and managing MPAs should be conducted on a multidisciplinary basis. Nonetheless, no single model can be considered valid for the whole Mediterranean. The very variable characteristics of coastal areas, from those of small uninhabited islands to those of cities, require different weightings to be assigned for each factor in order to achieve a durable equilibrium and realize the original objectives of each MPA. Only with such flexibility of management will it be possible to reach a greater understanding of the MPA system and create a lasting consensus in favour of conservation, a consensus which would mean an overwhelming majority of people actively avoiding damaging nature and preventing others from doing so.This paper was realized with funds from the EU CEC DGXII–MAST III contract number: MAS3-ct97–0155
Tensor form factor for the D
We present a preliminary lattice calculation of the and
tensor form factors as a function of the squared 4-momentum transfer
. ETMC recently computed the vector and scalar form factors and
describing semileptonic decays analyzing the
vector current and the scalar density. The study of the weak tensor current,
which is directly related to the tensor form factor, completes the set of
hadronic matrix element regulating the transition between these two
pseudoscalar mesons within and beyond the Standard Model where a non-zero
tensor coupling is possible. Our analysis is based on the gauge configurations
produced by the European Twisted Mass Collaboration with
flavors of dynamical quarks. We simulated at three different values of the
lattice spacing and with pion masses as small as 210 MeV and with the valence
heavy quark in the mass range from to .
The matrix element of the tensor current are determined for a plethora of
kinematical conditions in which parent and child mesons are either moving or at
rest. As for the vector and scalar form factors, Lorentz symmetry breaking due
to hypercubic effects is clearly observed in the data. We will present
preliminary results on the removal of such hypercubic lattice effects.Comment: 8 pages, 5 figures, talk delivered at Lattice 2017 - 35th
International Symposium on Lattice Field Theory, 18th-24th June 2017, Granada
(Spain
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