Energy Loss Of Particles Research Articles

PPPC 4 DMν: a Poor Particle Physicist Cookbook for Neutrinos from Dark Matter annihilations in the Sun

We provide ingredients and recipes for computing neutrino signals of TeV-scale Dark Matter (DM) annihilations in the Sun.For each annihilation channel and DM mass we present the energy spectra of neutrinos at production, including: state-of-the-art energy losses of primary particles in solar matter, secondary neutrinos, electroweak radiation.We then present the spectra after propagation to the Earth, including (vacuum and matter) flavor oscillations and interactions in solar matter. We also provide a numerical computation of the capture rate of DM particles in the Sun.These results are available in numerical form.

Energy deposition of H and He ion beams in hydroxyapatite films: a study with implications for ion-beam cancer therapy.

Ion-beam cancer therapy is a promising technique to treat deep-seated tumors; however, for an accurate treatment planning, the energy deposition by the ions must be well known both in soft and hard human tissues. Although the energy loss of ions in water and other organic and biological materials is fairly well known, scarce information is available for the hard tissues (i.e., bone), for which the current stopping power information relies on the application of simple additivity rules to atomic data. Especially, more knowledge is needed for the main constituent of human bone, calcium hydroxyapatite (HAp), which constitutes 58% of its mass composition. In this work the energy loss of H and He ion beams in HAp films has been obtained experimentally. The experiments have been performed using the Rutherford backscattering technique in an energy range of 450-2000 keV for H and 400-5000 keV for He ions. These measurements are used as a benchmark for theoretical calculations (stopping power and mean excitation energy) based on the dielectric formalism together with the MELF-GOS (Mermin energy loss function-generalized oscillator strength) method to describe the electronic excitation spectrum of HAp. The stopping power calculations are in good agreement with the experiments. Even though these experimental data are obtained for low projectile energies compared with the ones used in hadron therapy, they validate the mean excitation energy obtained theoretically, which is the fundamental quantity to accurately assess energy deposition and depth-dose curves of ion beams at clinically relevant high energies. The effect of the mean excitation energy choice on the depth-dose profile is discussed on the basis of detailed simulations. Finally, implications of the present work on the energy loss of charged particles in human cortical bone are remarked.

Energy resolution of gas ionization chamber for high-energy heavy ions

The energy resolution is reported for high-energy heavy ions with energies of nearly 340 MeV/nucleon and was measured using a gas ionization chamber filled with a 90%Ar/10%CH4 gas mixture. We observed that the energy resolution is proportional to the inverse of the atomic number of incident ions and to the inverse-square-root of the gas thickness. These results are consistent with the Bethe–Bloch formula for the energy loss of charged particles and the Bohr expression for heavy ion energy straggling. In addition, the influence of high-energy δ-rays generated in the detector on the energy deposition is discussed.

Interaction of nonthermal muon beam with electron-positron-photon plasma: A thermal field theory approach

Interaction of a muon beam with hot dense QED plasma is investigated. Plasma system contains electrons and positrons with Fermi-Dirac distribution and Bose-Einstein distributed photons while the beam particles have nonthermal distribution. The energy loss of the beam particles during the interaction with plasma is calculated to complete leading order of interaction in terms of the QED coupling constant using thermal field theory approach. The screening effects of the plasma are computed consistently using resummation of perturbation theory with hard thermal loop approximation according to the Braaten-Pisarski method. Time evolution of the plasma characteristics and also plasma identifications during the interaction are investigated. Effects of the nonthermal parameter of the beam distribution on the energy exchange and the evolution of plasma-beam system are also explained.

Semi empirical formula for electronic stopping power determination of 24Mg, 27Al and 28Si ions crossing Formvar foil in the ion energy domain of LSS theory

We have determined continuous stopping power of heavy ions in thin Formvar foil for 28Si, 27Al and 24Mg ions over an energy range of (0.1–0.5)MeV/nucleon. Heavy Ions Elastic Recoil Detection Analysis (HI-ERDA) technique coupled with time of flight (ToF) spectrometer has been used to measure energy loss of charged particles in this thin absorber. Lindhard, Scharff and Schiott (LSS) theory compared with the corresponding determined stopping values in Formvar, shows significantly large deviations. However, a novel semi empirical expression has been proposed here and tested for better stopping power calculations at low velocity in the ion energy domain of LSS theory for 28Si, 27Al and 24Mg ions crossing thin Formvar foil. The results were compared to the obtained experimental stopping power data, predictions of LSS theory and also to those generated by SRIM-2010 computer code. The obtained results exhibit good agreement with experimental data.

Radiative energy loss of relativistic charged particles in absorptive media

Abstract We determine the energy loss spectrum per time-interval of a relativistic charge traversing a dispersive medium. Polarization and absorption effects in the medium are modelled via a complex index of refraction. We find that the spectrum amplitude becomes exponentially damped due to absorption mechanisms. Taking explicitly the effect of multiple scatterings on the charge trajectory into account, we confirm results obtained in a previous work.

Profile functions to reproduce Bragg reflection shapes observed by a time-of-flight single-crystal diffractometer installed at a coupled moderator pulsed neutron source in J-PARC

We performed a time-of-flight (TOF) single-crystal neutron diffraction experiment with a diffractometer (the IBARAKI Biological Crystal Diffractometer (iBIX)) using single-crystal silicon, and we determined several candidates for fundamental fitting functions to faithfully reproduce the Bragg reflection profile with asymmetries in the TOF direction. The Vavilov and Landau distributions used to describe the energy loss of charged particles traversing a thin absorber were found to be in excellent agreement with the observed TOF profile. We have evaluated the obtained functions and the convolution of back-to-back exponentials with a Gaussian to determine which function provides the best fit to the data. Further, we have applied the obtained functions to the practical Bragg reflection profiles of proteins after subtraction of the background using the Statistics-sensitive Nonlinear Iterative Peak-clipping (SNIP) algorithm.

A search for correlation of ultra-high energy cosmic rays with IRAS-PSCz and 2MASS-6dF galaxies

We study the arrival directions of 69 ultra-high energy cosmic rays (UHECRs) observed at the Pierre Auger Observatory (PAO) with energies exceeding 55 EeV. We investigate whether the UHECRs exhibit the anisotropy signal expected if the primary particles are protons that originate in galaxies in the local universe, or in sources correlated with these galaxies. We cross-correlate the UHECR arrival directions with the positions of IRAS-PSCz and 2MASS-6dF galaxies taking into account particle energy losses during propagation. This is the first time that the 6dF survey is used in a search for the sources of UHECRs and the first time that the PSCz survey is used with the full 69 PAO events. The observed cross-correlation signal is larger for the PAO UHECRs than for 94% (98%) of realisations from an isotropic distribution when cross-correlated with the PSCz (6dF). On the other hand the observed cross-correlation signal is lower than that expected from ≳85% of realisations, had the UHECRs originated in galaxies in either survey. The observed cross-correlation signal does exceed that expected by 50% of the realisations if the UHECRs are randomly deflected by intervening magnetic fields by 5° or more. We propose a new method of analysing the expected anisotropy signal, by dividing the predicted UHECR source distribution into equal predicted flux radial shells, which can help localise and constrain the properties of UHECR sources. We find that the 69 PAO events are consistent with isotropy in the nearest of three shells we define, whereas there is weak evidence for correlation with the predicted source distribution in the two more distant shells in which the galaxy distribution is less anisotropic.

Ionization energy losses of relativistic electron in boundary layer of substance

Ionization energy losses of relativistic electron after its traversal of interface between two dielectric media are considered. The explicit dependence of the particle energy losses per unit of path in the boundary layer of the medium, which it enters, on the distance between the particle and the interface is obtained. It is demonstrated that the peculiarities of transformation of electron energy losses in the boundary layer significantly depend on the type of its stationary energy losses in each medium. The particular case, in which such transformation may occur on large macroscopic distances, is discussed.

Electron fluxes and pitch‐angle distributions at dipolarization fronts: THEMIS multipoint observations

AbstractTaking advantage of multipoint observations from a Cluster‐like Time History of Events and Macroscale Interactions during Substorms (THEMIS) probe configuration repeated in three events, we study pitch‐angle distributions (PAD) of lower energy (0.2–keV) electrons and omnidirectional energy‐time spectrograms of higher energy (30–500 keV) electrons observed at and near dipolarization fronts in the plasma sheet. Recent observations have shown that dipolarization fronts in the plasma sheet provide an impulsive electric field suggested to cause electron energization and dispersionless injections. Increase and decrease in energetic electron flux are equally probable at the fronts, however. Our case studies demonstrate increased energetic electron flux in the front's central region but decreased flux on its dusk side, where diverted plasma flow forms a vortex. An electric field associated with this vortex causes the electron flux decrease. We also find that shorter‐term energetic flux decreases, often observed before injections, coincide with a dip in the northward magnetic field ahead of the front. We attribute these decreases to particle energy loss via the inverse betatron effect. Our case studies reveal that pancake‐type (maximum at 90° pitch angle) and cigar‐type (maxima at 0 and 180°) PADs coexist at the same front. Our data analysis suggests that energetic electron PADs are mainly pancake type near the neutral sheet (|Bx| < 5 nt) and mainly cigar type at |Bx| > 10 nt. These results, to be confirmed in statistical studies, provide important constraints for further modeling of electron energization and transport toward the inner magnetosphere.

EFFECTS OF DUST GROWTH AND SETTLING ON THE IONIZATION BY RADIONUCLIDES. I. FORMULATION AND RESULTS IN A QUIESCENT STATE OF PROTOPLANETARY DISKS

We investigate the evolution of the ionization rates by the decay of radionuclides in protoplanetary disks at the early stage of planet formation where size growth and settling of dust particles proceed extensively. Because most of the nuclides to ionize gas, such as short-lived nuclide 26Al and long-lived one 40K, are refractory elements, they are contained in the solid material of dust particles. Thus, the ionization by these nuclides is affected by the following three processes: (1) the change of the relative abundance of dust particles due to the settling toward the midplane of the disk, (2) the energy loss of emitted energetic particles inside the solid material of dust particles, and (3) the absorption of energetic particles by the other dust particles located nearby. In this series of papers we comprehensively investigate the basic physical processes, calculate the settling and size growth of dust particles numerically, and clarify the evolution of the ionization rates relative to their initial values in various disk models at this stage. In this paper we investigate the energy-loss processes concerning dust particles, formulate the coalescence equation for settling particles, and apply them to quiescent disk models that are similar to the solar nebula. For simplicity, dust particles are assumed to be compact spheres that remain perfect sticking for mutual collisions. Because the settling of dust particles is not appreciable in the first 103 yr, the ionization rate varies little except in the outermost part near the disk surface. As the settling proceeds, the rate around the midplane increases considerably. The maximum ionization rates by 26Al in the minimum mass solar nebula are about 100, 51, and 14 times larger than their initial values for the orbits R = 0.5, 1, and 5 AU, respectively, which are close to or exceed the ionization rate by cosmic ray in the interstellar medium. The rates by 40K also increase by factors of about 36, 19, and 5 at the same orbits. In the inner orbital regions, these rates exceed the rates by the attenuated cosmic rays by an order of magnitude. The rates in the residual parts decrease extensively as time goes by, because amounts of the floating dust particles decrease continuously.

On the pressure dependence of thermal rebound

Based on direct measurements of the critical velocity for nanoparticle rebound, vcr, the possibility of thermal rebound is revisited. The thermal velocity, vtherm, for Ag and NaCl particles in the size range between 10nm and 100nm is calculated and compared to the respective value of vcr. Thermal rebound is impossible for dense spherical silver particles and porous NaCl particles. For dense NaCl particles vtherm exceeds the measured values for vcr for particles between 20nm and 60nm in diameter, proving the possibility of thermal rebound in a size-range much larger than expected. This result is in disagreement with the work of other researchers that did not observe thermal rebound in this size-range for NaCl particles. As these studies were performed under ambient pressure, while the direct measurement of vcr was performed at reduced pressure around 10mbar, thermal rebound must be pressure dependent for nanoparticles. This conclusion is confirmed with a simple model calculation, showing that at ambient pressure gas friction contributes significantly to the particle energy loss before the particle leaves a surface completely. This necessitates a redefinition of the term ‘critical velocity’.

Sensitivity of ICF ignition conditions to non-Maxwellian DT fusion reactivity

The hotspot ignition conditions in ICF are determined by considering the power balance between fusion energy deposition and energy loss terms. Uncertainty in any of these terms has potential to modify the ignition conditions, changing the optimum ignition capsule design. This paper considers the impact of changes to the DT fusion reaction rate due to non-thermal ion energy distributions. The DT fusion reactivity has been evaluated for a class of non-Maxwellian distributions representing a perturbation to the tail of a thermal distribution. The resulting reactivity has been used to determine hotspot ignition conditions as a function of the characteristic parameter of the modified distribution. The hotspot ignition conditions in ICF can be determined by considering the power balance between fusion alpha particle energy deposition, hydrodynamic work and energy loss via radiation and electron thermal conduction (1). The resulting conditions may be sensitive to uncertainties in any of the key plasma physics models or assumptions. This paper considers the impact of changes to the DT fusion reaction rate due to the presence of non-thermal ion energy distributions. The reactivity,� v� , for thermonuclear fusion reactions is conventionally derived by averaging cross- section data over a Maxwell-Boltzmann energy distribution. In many situations, such as when plasmas are strongly shocked or rapidly heated by energetic particles, reacting ions may be better characterised by a non-Maxwellian distribution. Since the self-relaxation time is longer for ions at higher energies (2), such effects typically produce an enhancement or depletion within the tail of the distribution. At temperatures where the reactivity is dominated by the contribution of particles in the tail, even small changes to the distribution may have a potentially significant impact on the fusion reaction rate. The DT fusion reactivity has been evaluated for a class of non-Maxwellian distributions, the q-Gaussian distribution (3), which represent a perturbation to the tail of a thermal distribution. The resulting reactivity has been used to calculate a revised ideal ignition temperature (4) and to determine hotspot ignition conditions as a function of the characteristic parameter of the distribution. This initial assessment does not consider in detail the physical development of non-Maxwellian distributions. If conditions are found to show significant sensitivity, then the generation of distributions may be explored in future work via kinetic simulation.

Photon emission and electron-positron photoproduction processes in the planar field of a bent single crystal

The process of photon emission by a high-energy electron or positron moving in a bent single crystal with a constant curvature is considered. The relations for differential energy losses of particles and polarization of emitted photons are obtained. Corrections due to multiphoton production are found. The comparison of calculations with existing experimental data is carried out. The process of photoproduction of electron-positron pairs in a bent single crystal is also studied. The differential probabilities of the process taking into account the photon polarization are presented. Equations are obtained which determine the variation of the Stokes parameters of $\ensuremath{\gamma}$ quanta, and their solutions are given.

Erratum: Plasma Damping Effects on the Radiative Energy Loss of Relativistic Particles [Phys. Rev. Lett.107, 265004 (2011)

Received 17 September 2012DOI:https://doi.org/10.1103/PhysRevLett.109.169902© 2012 American Physical Society

Energy distribution of metal and noble gas ions traversing single-crystal copper films

A comparative investigation of the energy distribution of ions that traversed single-crystal cooper films reveals that the energy loss of channeled and nonchanneled particles depends not only on the mass but also on the radius of bombarding ions. It is established that the energy spectra of transmitted ions are highly sensitive to a change in the composition and structure of the films. From the change in these spectra, one can estimate the degree of disordering in thin films under various applied forces.

D3/D7 quark-gluon plasma with magnetically induced anisotropy

We study the effects of the temperature and of a magnetic field in the setup of an intersection of D3/D7 branes, where a large number of D7 branes is smeared in the transverse directions to allow for a perturbative solution in a backreaction parameter. The magnetic field sources an anisotropy in the plasma, and we investigate its physical consequences for the thermodynamics and energy loss of particles probing the system. In particular we comment on the stress-energy tensor of the plasma, the propagation of sound in the directions parallel and orthogonal to the magnetic field, the drag force of a quark moving through the medium and jet quenching.

General Cause of Sheath Instability Identified for Low Collisionality Plasmas in Devices with Secondary Electron Emission

A condition for sheath instability due to secondary electron emission (SEE) is derived for low collisionality plasmas. When the SEE coefficient of the electrons bordering the depleted loss cone in energy space exceeds unity, the sheath potential is unstable to a negative perturbation. This result explains three different instability phenomena observed in Hall thruster simulations including a newly found state with spontaneous ∼20 MHz oscillations. When instabilities occur, the SEE propagating between the walls becomes the dominant contribution to the particle flux, energy loss and axial transport.

Energy loss of charged particles interacting with conducting structures of spheroidal shape

We study the interaction of charged particles with a spheroidal conductor. Energy losses upon the excitation of polarization fields when a particle flies past the conducting spheroid are calculated within the simplest single-mode model of the dielectric function of the conductor. The results are compared to the limiting cases of a sphere and cylinder.

SYNCHROTRON EMISSION FROM VERY HIGH ENERGY GAMMA-RAY-INDUCED PAIR CASCADES IN ACTIVE GALACTIC NUCLEUS ENVIRONMENTS

The discovery of very-high-energy (VHE, E > 100 GeV) gamma-ray emission from intermediate- and low-frequency peaked blazars suggests that gamma-gamma absorption and pair cascading might occur in those objects. In previous papers, we investigated the Compton emission from VHE gamma-ray induced pair cascades, deflected by moderate magnetic fields, in a largely model-independent way, and demonstrated that this emission can explain the Fermi fluxes and spectra of the radio galaxies Cen A and NGC 1275. In this paper, we describe a generalization of our Monte-Carlo cascade code to include the angle-dependent synchrotron output from the cascades, allowing for the application to situations with non-negligible magnetic fields, leading to potentially observable synchrotron signatures, but still not dominating the radiative energy loss of cascade particles. We confirm that the synchrotron radiation from the cascades in NGC 1275 and Cen A are negligible for the parameters used in our previous works. We demonstrate that the magnetic field can not be determined from a fit of the cascade emission to the gamma-ray spectrum alone, and the degeneracy can only be lifted if the synchrotron emission from the cascades is observed as well. We illustrate this fact with the example of NGC 1275. We point out that the cascade synchrotron emission may produce spectral features in the same energy range in which the big blue bump is observed in the spectral energy distributions of several blazars, and may make a non-negligible contribution to this feature. We illustrate this idea with the example of 3C 279.