The dissipative linear Boltzmann equation for hard spheres

We prove the existence and uniqueness of an equilibrium state with unit mass to the dissipative linear Boltzmann equation with hard--spheres collision kernel describing inelastic interactions of a gas particles with a fixed background. The equilibrium state is a universal Maxwellian distribution function with the same velocity as field particles and with a non--zero temperature lower than the background one, which depends on the details of the binary collision. Thanks to the H--theorem we then prove strong convergence of the solution to the Boltzmann equation towards the equilibrium.Comment: 17 pages, submitted to Journal of Statistical Physic

Integral representation of the linear Boltzmann operator for granular gas dynamics with applications

We investigate the properties of the collision operator associated to the linear Boltzmann equation for dissipative hard-spheres arising in granular gas dynamics. We establish that, as in the case of non-dissipative interactions, the gain collision operator is an integral operator whose kernel is made explicit. One deduces from this result a complete picture of the spectrum of the collision operator in an Hilbert space setting, generalizing results from T. Carleman to granular gases. In the same way, we obtain from this integral representation of the gain operator that the semigroup in L^1(\R \times \R,\d \x \otimes \d\v) associated to the linear Boltzmann equation for dissipative hard spheres is honest generalizing known results from the first author.Comment: 19 pages, to appear in Journal of Statistical Physic

Charged particle jet measurements with the ALICE experiment in proton-proton collisions at the LHC

We present preliminary results of measurements of charged particle jet properties in proton-proton collisions at $\sqrt{s}$ = 7 TeV using the ALICE detector. Jets are reconstructed using $\rm anti-k_{T}, k_{T}$ and SISCone jet finding algorithms with resolution parameter $R=0.4$ in the range of transverse momentum from 20 to 100 GeV/$c$ in the midrapidity region (\mid\eta\mid\textless 0.5). The uncorrected charged jet spectra obtained using the three different jet finders show good agreement. The data are compared to predictions from PYTHIA-Perugia0, PYTHIA-Perugia2011, and PHOJET. The mean charged particle multiplicity in leading jets increases with increasing jet $p_{\rm T}$ and is consistent with model predictions. The radial distributions of transverse momentum about the jet direction and the distributions of the average radius containing 80% of the total jet $p_{\rm T}$ found in the jet cone ($R = 0.4$ in this analysis), indicate that high $p_{\rm T}$ jets are more collimated than low $p_{\rm T}$ jets.Comment: 6 pages, 6 figures, Conference Proceedings submitted for the 28th Winter Workshop on Nuclear Dynamics, Puerto Rico, April 7-14, 201

Acta Societatis pro fauna et flora Fennica

Kielet saksa ja ruotsi

XUV digital in-line holography using high-order harmonics

A step towards a successful implementation of timeresolved digital in-line holography with extreme ultraviolet radiation is presented. Ultrashort XUV pulses are produced as high-order harmonics of a femtosecond laser and a Schwarzschild objective is used to focus harmonic radiation at 38 nm and to produce a strongly divergent reference beam for holographic recording. Experimental holograms of thin wires are recorded and the objects reconstructed. Descriptions of the simulation and reconstruction theory and algorithms are also given. Spatial resolution of few hundreds of nm is potentially achievable, and micrometer resolution range is demonstrated.Comment: 8 pages, 8 figure

Mass measurements in the vicinity of the doubly-magic waiting point 56Ni

Masses of 56,57Fe, 53Co^m, 53,56Co, 55,56,57Ni, 57,58Cu, and 59,60Zn have been determined with the JYFLTRAP Penning trap mass spectrometer at IGISOL with a precision of dm/m \le 3 x 10^{-8}. The QEC values for 53Co, 55Ni, 56Ni, 57Cu, 58Cu, and 59Zn have been measured directly with a typical precision of better than 0.7 keV and Coulomb displacement energies have been determined. The Q values for proton captures on 55Co, 56Ni, 58Cu, and 59Cu have been measured directly. The precision of the proton-capture Q value for 56Ni(p,gamma)57Cu, Q(p,gamma) = 689.69(51) keV, crucial for astrophysical rp-process calculations, has been improved by a factor of 37. The excitation energy of the proton emitting spin-gap isomer 53Co^m has been measured precisely, Ex = 3174.3(10) keV, and a Coulomb energy difference of 133.9(10) keV for the 19/2- state has been obtained. Except for 53Co, the mass values have been adjusted within a network of 17 frequency ratio measurements between 13 nuclides which allowed also a determination of the reference masses 55Co, 58Ni, and 59Cu.Comment: 14 pages, 13 figures, submitted to Phys. Rev.

MesonNet 2013 International Workshop. Mini-proceedings

The mini-proceedings of the MesonNet 2013 International Workshop held in Prague from June 17th to 19th, 2013, are presented. MesonNet is a research network within EU HadronPhysics3 project (1/2012 -- 12/2014). The web page of the conference, which contains all talks, can be found at http://ipnp.mff.cuni.cz/mesonnet13Comment: 106 pages, 53 contributions. Mini-proceedings of the MesonNet 2013 International Workshop. Editors: K. Kampf, A. Kupsc, and P. Masjua

Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements

The ABC effect - a puzzling low-mass enhancement in the $\pi\pi$ invariant mass spectrum - is well-known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on first exclusive and kinematically complete measurements of the most basic double pionic fusion reaction $pn \to d \pi^0\pi^0$ at 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a $(\pi\pi)_{I=L=0}$ channel phenomenon associated with both a resonance-like energy dependence in the integral cross section and the formation of a $\Delta\Delta$ system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data

Effects of undercutting and sliding on calving: a global approach applied to Kronebreen, Svalbard

In this paper, we study the effects of basal friction, sub-aqueous undercutting and glacier geometry on the calving process by combining six different models in an offline-coupled workflow: a continuum–mechanical ice flow model (Elmer/Ice), a climatic mass balance model, a simple subglacial hydrology model, a plume model, an undercutting model and a discrete particle model to investigate fracture dynamics (Helsinki Discrete Element Model, HiDEM). We demonstrate the feasibility of reproducing the observed calving retreat at the front of Kronebreen, a tidewater glacier in Svalbard, during a melt season by using the output from the first five models as input to HiDEM. Basal sliding and glacier motion are addressed using Elmer/Ice, while calving is modelled by HiDEM. A hydrology model calculates subglacial drainage paths and indicates two main outlets with different discharges. Depending on the discharge, the plume model computes frontal melt rates, which are iteratively projected to the actual front of the glacier at subglacial discharge locations. This produces undercutting of different sizes, as melt is concentrated close to the surface for high discharge and is more diffuse for low discharge. By testing different configurations, we show that undercutting plays a key role in glacier retreat and is necessary to reproduce observed retreat in the vicinity of the discharge locations during the melting season. Calving rates are also influenced by basal friction, through its effects on near-terminus strain rates and ice velocity

X ray absorption spectroscopy and X ray Raman scattering of water and ice; an experimental view

Here we present a review of X-ray absorption spectroscopy and X-ray Raman scattering with the perspective to understand the spectra of water including changes with temperature, mass of the water molecule and presence of monovalent ions. The different detection schemes are discussed and it is concluded that transmission X-ray absorption measurements, using a small area where the thickness is uniform, and X-ray Raman scattering give the most reliable spectra. Different model systems are discussed such as the surface and bulk of ice and various adsorbed monolayer structures on metal surfaces.</p