Klein–Nishina formula and Monte Carlo method for evaluating the gamma attenuation properties of Zn, Ba, Te and Bi elements

In this work, the Klein–Nishina (K–N) approach was used to evaluate the electronic, atomic, and energy-transfer cross sections of four elements, namely, zinc (Zn), tellurium (Te), barium (Ba), and bismuth (Bi), for different photon energies (0.662 MeV, 0.835 MeV, 1.170 MeV, 1.330 MeV, and 1.600 MeV). The obtained results were compared with the Monte Carlo method (Geant4 simulation) in terms of mass attenuation and mass energy-transfer coefficients. The results show that the K–N approach and Geant4 simulations are in good agreement for the entire energy range considered. As the photon energy increased from 0.662 MeV to 1.600 MeV, the values of the energy-transfer cross sections decreased from 81.135 cm2 to 69.184 cm2 in the case of Bi, from 50.832 cm2 to 43.344 cm2 for Te, from 54.742 cm2 to 46.678 cm2 for Ba, and from 29.326 cm2 to 25.006 cm2 for Zn. The obtained results and the detailed information of the attenuation properties for the studied elements would be helpful in developing a new generation of shielding materials against gamma rays.

Energetic electron precipitation and their atmospheric effect

Energetic particle precipitation induces ionization of the atmosphere which initiates a chain of reaction cycles affecting atmospheric composition and dynamics potentially down to surface weather systems. Ionization rates are retrieved based on yield functions or pre-calculated monoenergetic electron flux and energy spectra of precipitated energetic particles. Usually, information about energy spectra is obtained from satellites, balloons, and various ground-based observations. In all cases, some assumptions about spectral distribution for the entire energy range have to be made. As ionization rates are widely used in chemistry-climate models to estimate the atmospheric response to particle forcing, evaluation of the energy spectra is a key task in the solar-terrestrial studies. In this paper, it is shown that possible uncertainties of the ionization rates retrieval based on different spectral functions can lead to large disagreements in the ionization rates, with implications for the modelled response of atmospheric composition and dynamics to electron precipitation.

Complex gamma-ray behavior of the radio galaxy M 87

Context. In recent years, non-blazar active galactic nuclei (AGN) such as radio galaxies have emerged as a highly instructive source class providing unique insights into high energy acceleration and radiation mechanisms. Aims. Here we aim to produce a detailed characterization of the high-energy (HE; >100 MeV) gamma-ray emission from the prominent radio galaxy M 87. Methods. We analyzed approximately eight years of Fermi-LAT data and derived the spectral energy distribution between 100 MeV and 300 GeV. We extracted lightcurves and investigated the variability behavior for the entire energy range as well as below and above 10 GeV. Results. Our analysis provides (i) evidence for HE gamma-ray flux variability and (ii) indications for a possible excess over the standard power-law model above Eb ∼ 10 GeV, similar to the earlier indications in the case of Cen A. When viewed in HE–VHE context, this is most naturally explained by an additional component dominating the highest-energy part of the spectrum. Investigation of the γ-ray lightcurves suggests that the lower-energy (<10 GeV) component is variable on timescales of (at least) a few months. The statistics of the high energy component (>10 GeV) does not allow significant constraints on variability. We do, however, find indications for spectral changes with time that support variability of the putative additional component and seem to favor jet-related scenarios for its origin capable of accommodating month-type variability. Conclusions. The current findings suggest that both the high-energy (>Eb) and the very high energy (VHE; >100 GeV) emission in M 87 are compatible with originating from the same physical component. The variability behavior at VHE then allows further constraints on the location and the nature of the second component. In particular, these considerations suggest that the VHE emission during the quiescent state originates in a similar region as during the flare.

Proposal for a photoelectron spectroscopy and microscopy beamline (0.5–11 keV) at the High Energy Photon Source

An optical design study of a beamline proposed for the new 6 GeV synchrotron, the High Energy Photon Source (HEPS), to be built in Beijing, China, is described. The beamline is designed to cover an energy range from 0.5 to 11 keV with two experimental stations, one for X-ray photoelectron spectroscopy (PES) experiments and the other for photoelectron emission microscopy (XPEEM) experiments. A 5 m APPLE II-type undulator with a relatively long magnetic period (55 mm) is used as the only radiation source. To optimize the optical efficiency for the full energy range, the beamline is split into a soft X-ray branch that is based on a variable-line-spacing plane-grating monochromator and a tender X-ray branch that uses a four-bounce monochromator with three Si channel-cut pairs. To allow both PES and XPEEM to be performed over the entire energy range, two toroidal mirrors and a bendable KB mirror pair are employed to deliver the soft and tender beams, respectively, to either of two experimental stations.

Revisiting the decoupling effects in the running of the Cosmological Constant

We revisit the decoupling effects associated with heavy particles in the renormalization group running of the vacuum energy in a mass-dependent renormalization scheme. We find the running of the vacuum energy stemming from the Higgs condensate in the entire energy range and show that it behaves as expected from the simple dimensional arguments, meaning that it exhibits the quadratic sensitivity to the mass of the heavy particles in the infrared regime. The consequence of such a running to the fine-tuning problem with the measured value of the Cosmological Constant is analyzed and the constraint on the mass spectrum of a given model is derived. We show that in the Standard Model (SM) this fine-tuning constraint is not satisfied while in the massless theories this constraint formally coincides with the well-known Veltman condition. We also provide a remarkably simple extension of the SM where saturation of this constraint enables us to predict the radiative Higgs mass correctly. Generalization to constant curvature spaces is also given.

Study of the cosmogenic activation in NaI(Tl) crystals within the ANAIS experiment

The direct detection of galactic dark matter particles requires ultra-low background conditions. NaI(Tl) crystals are applied in the search for these dark matter particles through their interactions in the detector by measuring the scintillation signal produced. The production of long-lived isotopes in materials due to the exposure to cosmic rays on Earth’s surface can be an hazard for these ultra-low background demanding experiments, typically performed underground. Therefore, production rates of cosmogenic isotopes in all the materials present in the experimental set-up, as well as the corresponding cosmic rays exposure history, must be both well-known in order to assess the relevance of this effect in the achievable sensitivity of a given experiment. Here, analysis of the cosmogenic studies developed from the ANAIS experiment NaI(Tl) detectors are presented. Installed inside a convenient shielding at the Canfranc Underground Laboratory just after finishing surface exposure to cosmic rays and thanks to the prompt data taking developed, identification and quantification of isotopes with half-lives of the order of tens of days were allowed, and thanks to the long-term operation of the detectors long-lived isotopes have been also identified and quantified. Main results for the activation yields of iodine and tellurium isotopes, [Formula: see text]Na, [Formula: see text]Sn, [Formula: see text]Cd, and tritium are presented in this work, together with the estimate of the production rates for their activation by cosmic nucleons while on Earth’s surface based on a selection of excitation functions over the entire energy range of cosmic nucleons.

Cosmic ray particles from exploding massive stars with winds

The origin of cosmic rays is still unsettled. Many sources have been proposed over the years, and exploding stars still provide the most promising candidates. Here we examine one of these scenarios, and compare the resulting predictions with data: Massive stars have winds, and when these stars explode, the resulting shock runs through the wind. The observable phenomenon is called radio-supernova, and many have been observed in non-thermal radio emission. This emission allows to determine the magnetic field in the wind as a function of radius, and so allows to check, whether such explosions can achieve the high energies required and also explain the flux and the spectra of cosmic rays. The observations show this to be the case, and so we conclude that radio supernovae can explain the high-energy Galactic cosmic rays over the entire energy range, and that the spectral predictions are compatible with observations.

Microcanonical Entropy of the Infinite-State Potts Model

In this investigation we show that the entropy of the two-dimensional infinite-state Potts model is linear in configurational energy in the thermodynamic limit. This is a direct consequence of the local convexity of the microcanonical entropy, associated with a finite system undergoing a first-order transition. For a sufficiently large number of states , this convexity spans the entire energy range of the model. In the thermodynamic limit, the convexity becomes insignificant, and the microcanonical entropy (the logarithm of the density of states) tends to a straight line. In order to demonstrate the behaviour of the convexity, we use the Wang-Landau Monte-Carlo technique to numerically calculate the density of states for a few finite but high values of . Finally, we calculate the free energy and discuss the generality of our results.