27 research outputs found
Calculation Of Secondary Particles In Atmosphere And Hadronic Interactions
Calculation of secondary particles produced by the interaction of cosmic rays
with the nuclei of Earth's atmosphere pose important requirements to particle
production models. Here we summarize the important features of hadronic
simulations, stressing the importance of the so called ``microscopic''
approach, making explicit reference to the case of the FLUKA code. Some
benchmarks are also presented.Comment: 10 pages, 4 figures. Extended version of report given at the IInd
Workshop on Matter and anti-Matter, Trento, Oct. 200
The decay pi0 to gamma gamma to next to leading order in Chiral Perturbation Theory
The two photon decay width of the neutral pion is analyzed within the
combined framework of Chiral Perturbation Theory and the 1/Nc expansion up to
order p^6 and p^4 times 1/Nc in the decay amplitude. The eta' is explicitly
included in the analysis. It is found that the decay width is enhanced by about
4.5% due to the isospin-breaking induced mixing of the pure U(3) states. This
effect, which is of leading order in the low energy expansion, is shown to
persist nearly unchanged at next to leading order. The chief prediction for the
width with its estimated uncertainty is 8.10+-0.08 eV. This prediction at the
1% level makes the upcomming precision measurement of the decay width even more
urgent.
Observations on the eta and eta' can also be made, especially about their
mixing, which is shown to be significantly affected by next to leading order
corrections.Comment: 21 pages, two figure
Relating the Lorentzian and exponential: Fermi's approximation,the Fourier transform and causality
The Fourier transform is often used to connect the Lorentzian energy
distribution for resonance scattering to the exponential time dependence for
decaying states. However, to apply the Fourier transform, one has to bend the
rules of standard quantum mechanics; the Lorentzian energy distribution must be
extended to the full real axis instead of being bounded from
below (``Fermi's approximation''). Then the Fourier transform
of the extended Lorentzian becomes the exponential, but only for times , a time asymmetry which is in conflict with the unitary group time evolution
of standard quantum mechanics. Extending the Fourier transform from
distributions to generalized vectors, we are led to Gamow kets, which possess a
Lorentzian energy distribution with and have exponential
time evolution for only. This leads to probability predictions
that do not violate causality.Comment: 23 pages, no figures, accepted by Phys. Rev.
The beam and detector of the NA62 experiment at CERN
NA62 is a fixed-target experiment at the CERN SPS dedicated to measurements of rare kaon decays. Such measurements, like the branching fraction of the K+ → π+ ν bar nu decay, have the potential to bring significant insights into new physics processes when comparison is made with precise theoretical predictions. For this purpose, innovative techniques have been developed, in particular, in the domain of low-mass tracking devices. Detector construction spanned several years from 2009 to 2014. The collaboration started detector commissioning in 2014 and will collect data until the end of 2018. The beam line and detector components are described together with their early performance obtained from 2014 and 2015 data