Diffusive shock acceleration in extragalactic jets

We calculate the temporal evolution of distributions of relativistic electrons subject to synchrotron and adiabatic processes and Fermi-like acceleration in shocks. The shocks result from Kelvin-Helmholtz instabilities in the jet. Shock formation and particle acceleration are treated in a self-consistent way by means of a numerical hydrocode. We show that in our model the number of relativistic particles is conserved during the evolution, with no need of further injections of supra-thermal particles after the initial one. From our calculations, we derive predictions for values and trends of quantities like the spectral index and the cutoff frequency that can be compared with observations.Comment: 12 pages containing 7 postscript figures; uses A&A macros. Accepted for publication in Astronomy and Astrophysic

A new Monte Carlo muon generator for cosmic-ray muon applications

Cosmic rays, thanks to their ubiquity and high penetration capability, have been successfully used in scientific research ever since their discovery. As soon as their knowledge improved, applications in the civil/environmental field were also developed: muon radiography (or muography, based on the flux attenuation) and muon tomography (based on the scattering angle) have been used to study the inner structure of volcanoes, to seek hidden rooms in Egyptian pyramids, to search for heavy metals in containers, and so on. And besides these imaging techniques, cosmic ray muons are also widely used for detector testing and alignment practically in every Nuclear Physics or Particle Physics experiment. Since most of these applications are sensitive to the angular and momentum distribution of cosmic muons, an accurate modelling of these distributions is a key feature for any generation tool conceived to simulate the cosmic muon flux. This can make the generator quite time-consuming, which is a strong limit when one needs to reach high statistics or to study large structures. A new Monte Carlo generator for cosmic-ray muons, named Efficient COsmic MUon Generator (EcoMug for short), especially designed to be fast (≳ 10^5 muons generated per second on a standard machine) without losing accuracy, is presented here. It is written as a header-only C++11 library, ready to be integrated into whatever C++ code, in particular C++ code based on Geant4 simulation tool. By default, EcoMug relies on a simple and effective parametrisation of the experimental data of cosmic ray differential flux at sea level, taken from the literature, but the library is written in such a way that every user can easily replace it with his own user-defined parametrisation. Unlike other tools, EcoMug is able to generate muons from different kind of surfaces (plane, cylinder and half-sphere), while keeping the correct angular and momentum distribution of generated tracks inside a fiducial volume. This allows to optimise the generation surface according to the system under study, and leads to a further improvement of the overall simulation efficiency. In this contribution we will present the main features of EcoMug, starting from its mathematical foundation, and eventually showing some interesting applications

Experimental evidence of antiproton reflection by a solid surface

We report here experimental evidence of the reflection of a large fraction of a beam of low energy antiprotons by an aluminum wall. This derives from the analysis of a set of annihilations of antiprotons that come to rest in rarefied helium gas after hitting the end wall of the apparatus. A Monte Carlo simulation of the antiproton path in aluminum indicates that the observed reflection occurs primarily via a multiple Rutherford-style scattering on Al nuclei, at least in the energy range 1-10 keV where the phenomenon is most visible in the analyzed data. These results contradict the common belief according to which the interactions between matter and antimatter are dominated by the reciprocally destructive phenomenon of annihilation.Comment: 5 pages with 5 figure

Preliminary study on Alpine ibex (Capra ibex ibex, L.) and livestock distribution in Gran Paradiso National Park

In the last decades there was a drastic decrease in Gran Paradiso National Park ibex population linked with a reduction of stable occupied territories. Causes are still not completely clear but drastic decline is in partly related to recent climate changes. The objectives of this work are: (1) understand ibex distribution in GPNP in 1985-2009 period and describe livestock distribution in the same area in 2000-2009; (2) assess relation between distribution pattern and ibex population trend in 2000-2009. To understand distribution patterns 5 landscape ecology metrics are been selected to assess the composition and spatial configuration of occupied areas. Spearman\u2019s rank correlation coefficient was used to test composition and configuration metric trends and their relation with ibex population size. Results showed a reduction of ibex occupied territories from 4,587.50 hectares in 1985 to 2,331.25 ha in 2009 (r =-0,818; P<0,001). Number of patches increased from 130 to 224 units (r s s =0,784; P<0,001). Livestock distribution didn\u2019t show a particular trend (r s 2 S), ammonia (NH 3 ), carbon monoxide (CO), and carbon dioxide (CO 4 types of floating covers were tested: light expanded clay aggregate (leca), peat, sunflower oil, sawdust, straw, and plastic film. The manure was stored at 5, 15, and 25 \ub0C for 37 d. Gaseous emissions were measured from headspaces of dynamic chambers. The results of our study showed that both the covering and temperature have a noticeable impact on gas emission from pig liquid manure. The plastic film cover was the most efficient at all temperatures tested, because it reduced the emissions of all measured gases. In this instance, average emission reductions were: CH 4 91.5% (P<0.01), NO 92.0% (P<0.05), H 2 480 or P>0,05). The relation between changes in ibex population trend and distribution patterns was not proven (all P>0,005). These results suggest that probably ibex distribution was influenced by different combined factors (landscape changes, climate change, anthropic activities) and they show how landscape ecology approach may become an useful tool to understand the degree of fragmentation and connectivity of landscape defined on species distribution. In conclusion, the understanding of processes behind Alpine ungulates distribution have to consider the influence of landscape patterns on environmental processes to improve the conservation efforts at management level

Monotonicity of quantum ground state energies: Bosonic atoms and stars

The N-dependence of the non-relativistic bosonic ground state energy is studied for quantum N-body systems with either Coulomb or Newton interactions. The Coulomb systems are "bosonic atoms," with their nucleus fixed, and the Newton systems are "bosonic stars". In either case there exists some third order polynomial in N such that the ratio of the ground state energy to the respective polynomial grows monotonically in N. Some applications of these new monotonicity results are discussed

Measurement of the antiproton–nucleus annihilation cross section at 5.3 MeV

n/

Evidence For The Production Of Slow Antiprotonic Hydrogen In Vacuum

We present evidence showing how antiprotonic hydrogen, the quasistable antiproton-proton (pbar-p) bound system, has been synthesized following the interaction of antiprotons with the hydrogen molecular ion (H2+) in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events, evidence is presented for antiprotonic hydrogen production with sub-eV kinetic energies in states around n=70, and with low angular momenta. The slow antiprotonic hydrogen may be studied using laser spectroscopic techniques.Comment: 5 pages with 4 figures. Published as Phys. Rev. Letters 97, 153401 (2006), in slightly different for

Exploration of jet substructure using iterative declustering in pp and Pb–Pb collisions at LHC energies

Zhe ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at √s= 7 TeV and central Pb-Pb collisions at √sNN = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, th

Measurement of prompt D0, D+, D*+, and D+S production in p–Pb collisions at √sNN = 5.02 TeV

The measurement of the production of prompt D0, D+, D*+, and D+S mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of √sNN = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb−1, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 &lt; ycms&lt; 0.04) as a function of transverse momentum (pT) in the intervals 0 &lt; pT&lt; 36 GeV/c for D0, 1 &lt; pT&lt; 36 GeV/c for D+ and D*+, and 2 &lt; pT&lt; 24 GeV/c for D+ mesons. For each species, the nuclear modification factor RpPb is calculated as a function of pT using a proton-proton (pp) ref- erence measured at the same collision energy. The results are compatible with unity in the whole pT range. The average of the non-strange D mesons RpPb is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The pT dependence of the D0, D+, and D*+ nuclear modification factors is also reported in the interval 1 &lt; pT&lt; 36 GeV/c as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the pT-differential cross sections of D0, D+, D*+, and D+S mesons are also reported. The D+S and D+ yields are compared as a function of the charged-particle multiplicity for several pT intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties