Institute of Nuclear Physics

This work presents an analysis of the physical mechanisms of radiation-induced changes in the structural parameters, morphology, and properties of ZnS and ZnSe crystals irradiated with 2 MeV electrons at fluences ranging from 0.5 × 1017to 4.0 × 1017electrons cm-2. The processes of defect formation (vacancies, interstitials, and dislocations) resulting from elastic (nuclear) and inelastic (electronic) collisions are analyzed. These processes lead to lattice compression, bandgap narrowing, and an increase in the Urbach energy with rising electron fluence, reflecting enhanced structural disorder, as well as to surface smoothing, higher microhardness, and intensification of the longitudinal optical phonon mode in the Raman spectra. Differences between ZnS and ZnSe are discussed with respect to the ionicity of chemical bonds and the defect dynamics influencing lattice relaxation. A conceptual physical model is proposed to explain the observed effects in ZnS and ZnSe, based on electron-phonon interactions and defect annihilation processes.

We aim to characterize the nearby (23.78 pc), low-mass planetary system GJ,7 (TOI-198), which consists of an M0-type star and a terrestrial planet. Using photometric data from three sectors of the Transiting Exoplanet Survey Satellite TESS ) and a follow-up on the planetary transit observed by the Characterizing ExOPlanets Satellite ( CHEOPS ), along with 87 precise radial velocities obtained with the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph, we confidently confirm the planet and infer its properties. Planet GJ,7,b has a mass of M_p = 3.17 ^ +0.64 _ -0.65 M_⊕ and a radius of R_p = 1.36 ± 0.13 R_⊕. It orbits at a distance of a = 0.0675 ^ +0.0067 _ -0.0082 au from its host star with an orbital period of P = 10.215213 ^ +0.000011 _ -0.000010 d. We impose a 3σ upper limit on the planetary eccentricity of e łe 0.15. These parameters imply that GJ,7,b has a high density, ̊ho_p = 6.89 ^ +4.27 _ -2.78 g,cm -3 $, positioning it within the region of the rocky, Earth-like planets on the mass--radius diagram and interior to the inner edge of the habitable zone around its parent star. Additionally, we find that the host star is a slow rotator and is slightly metal-depleted ( Fe/H = -0.66 ± 0.10 dex), making GJ,7 one of the few planetary systems accurately characterized in the domain of subsolar iron abundances. TESS photometry does not show additional transit-like features attributable to planets with radii greater than ≈90,% that of Earth. The high number of radial velocity measurements enables us to determine that possible transiting and non-transiting planet candidates with masses lower than half the mass of GJ,7,b would have eluded detection in our in-depth study. The stellar activity, although moderate, shows a significant radial velocity amplitude of about 4 m,s$^ -1 and poses a challenge for detecting planets with masses lower than Earth around GJ,7.

Abstract The differential cross sections of the proton transfer in the 7 Li( d , 3 He) 6 He reaction were measured at deuteron energies of 14.5 and 25 MeV. These data, as well as data on the reaction 7 Li( d, t ) 6 Li at an energy of 14.5 MeV, were analyzed within the framework of a Modified Distorted-Wave Method. The values of the asymptotic normalization coefficients for the 7 Li → 6 He + p when the 6 He nucleus is formed in the ground (0 + ) and excited 1.797 MeV (2 + ) states as well as 7 Li → 6 Li g.s. + n were obtained.

Measurements of beam single-spin asymmetries in semi-inclusive deep-inelastic electron scattering (SIDIS) with positively charged kaons off protons have been performed with 10.6 and 10.2 GeV incident electron beams using the CLAS12 spectrometer at Jefferson Lab. We report an analysis of the electroproduction of positively charged kaons over a large kinematic range of fractional energy, Bjorken x , transverse momentum, and photon virtualities Q 2 ranging from 1 GeV 2 up to 6 GeV 2 . This is the first published multidimensionally binned CLAS12 measurement of a kaon SIDIS single-spin asymmetry in the valence quark regime. The data provide constraints on the structure function ratio F L U sin ϕ / F U U , where F L U sin ϕ is a quantity with a leading twist of twist-3 that can reveal novel aspects of the quark-gluon correlations within the nucleon. The impact of the data on understanding the underlying reaction mechanisms and their kinematic variation is explored using theoretical models for the different contributing twist-3 parton-distribution functions (PDFs) and fragmentation functions (FFs).

We have investigated the relationship of variations in >0.7 and >2 MeV electron fluxes of Earth's outer radiation belt in a circular polar orbit with solar wind and interplanetary magnetic field parameters, as well as with geomagnetic indices and the logarithmic electron flux in the geostationary orbit in order to explore the possibility of predicting them. We have selected the optimal input features for predicting electron fluxes in low polar orbits, which is important for ensuring the radiation safety of future space missions. We have examined integral and maximum electron fluxes of these energies over the span of a day. We have obtained forecasts with a horizon of 1 and 2 days for an interval of 2 months in 2020 for daily maximum and integral fluxes based on linear regression.

We calculate cross sections for the production of different neutron classes <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mn>0</a:mn><a:mi>n</a:mi><a:mn>0</a:mn><a:mi>n</a:mi></a:math>, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mn>0</c:mn><c:mi>n</c:mi><c:mi>X</c:mi><c:mi>n</c:mi><c:mo>+</c:mo><c:mi>X</c:mi><c:mi>n</c:mi><c:mn>0</c:mn><c:mi>n</c:mi></c:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>X</e:mi><e:mi>n</e:mi><e:mi>X</e:mi><e:mi>n</e:mi></e:math>, possible to measure in Zero Degree Calorimeters (ZDCs), associated with photon-photon scattering in ultraperipheral collisions (UPC) of lead on lead. The calculations are performed for the ATLAS kinematics. Our calculations for neutron classes are tested against existing data for <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msup><g:mi>ρ</g:mi><g:mn>0</g:mn></g:msup></g:math> production in UPC. We get a good agreement for absolute cross section as well as very good results for fractional cross section which gives confidence to the analogous calculation for diphoton production, corresponding to <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mi>γ</i:mi><i:mi>γ</i:mi><i:mo stretchy="false">→</i:mo><i:mi>γ</i:mi><i:mi>γ</i:mi></i:math> scattering. We present both absolute as well as fractional cross sections for the different neutron classes. We also show different distributions in impact parameter, photon rapidity, transverse momentum, diphoton invariant mass, and photon rapidity difference. The shapes of the photon distributions depend on the neutron classes which we quantify in this paper. It would be valuable to test our predictions using the ATLAS main detector and the ATLAS ZDCs.