Hasil untuk "Nuclear and particle physics. Atomic energy. Radioactivity"

S. Mironov, A. Shtennikova, M. Valencia-Villegas

Abstract We analyze the generalizations of Kaluza–Klein compactifications of 5D Horndeski theory. They are Scalar–Vector–Tensor (SVT) theories with higher derivatives in the action, but with second order equations of motion. The vector field is invariant under a U(1) gauge transformation and the Scalar–Tensor sector corresponds to Horndeski theory. A subclass of these SVT theories is such that the Horndeski functions $$G_4(\pi ,X)$$ G 4 ( π , X ) and $$G_5(\pi )$$ G 5 ( π ) remain free, while the speed of the tensor and vector modes is exactly the same. We show a subclass where the vector sector retains freedom through new functions of $$\pi ,\, X$$ π , X while the speed of the vector modes still tracks the speed of the tensor modes.

Sergio E. Aguilar-Gutierrez, Yichao Fu, Kuntal Pal et al.

Abstract We study SU(N) spin systems that mimic the behavior of particles in N-dimensional de Sitter space for N = 2, 3. Their Hamiltonians describe a dynamical system with hyperbolic fixed points, leading to emergent quasinormal modes at the quantum level. These manifest as quasiparticle peaks in the density of states. For a particle in 2-dimensional de Sitter, we find both principal and complementary series densities of states from a PT-symmetric version of the Lipkin-Meshkov-Glick model, having two hyperbolic fixed points in the classical phase space. We then study different spectral and dynamical properties of this class of models, including level spacing statistics, two-point functions, squared commutators, spectral form factor, Krylov operator and state complexity. We find that, even though the early-time properties of these quantities are governed by the saddle points — thereby in some cases mimicking corresponding properties of chaotic systems, a close look at the late-time behavior reveals the integrable nature of the system.

Montague King, Sara Benitez, Alexander Christie et al.

Optical Beam-Loss Monitors (oBLMs) allow for cost-efficient and spatially continuous measurements of beam losses at accelerator facilities. A standard oBLM consists of several tens of metres of optical fibre aligned parallel to a beamline, coupled to photosensors at either or both ends. Using the timing information from loss signals, the loss positions can be reconstructed. This paper presents a novel oBLM system recently deployed at the CERN Linear Electron Accelerator for Research (CLEAR). Multiple methods of extracting timing and position information from measured waveforms with silicon photomultipliers (SiPM) and photomultiplier tubes (PMT) are investigated. For this installation, the optimal approach is determined to be applying a constant fraction discrimination (CFD) on the upstream readout. The position resolution is found to be similar for the tested SiPM and PMT. This work has resulted in the development of a user interface to aid operations by visualising the beam losses and their positions in real time.

WANG Mengqi, ZHENG Zheng, MEI Qiliang, PENG Chao, GAO Jing, ZHOU Yan

This study is dedicated to exploring an advanced intelligent multi-objective shielding optimization method based on the third generation non-dominated sorting genetic algorithm (NSGA-Ⅲ). The program’s functionality was tested and validated to improve the efficiency and effectiveness of shielding design for spent fuel transport ship. The study employed a sophisticated multi-objective intelligent optimization procedure and designed a one-dimensional discrete ordinates scale computational model. The model played a key role in optimizing the shielding structure above the hatch cover, paying particular attention to the dimensions of the concrete and polyethylene layers. This meticulous process resulted in the selection of a series of improved shielding solutions. In addition, a realistic 3D Monte-Carlo computational model was built to rigorously evaluate the shielding effectiveness of these optimized solutions. This model was used for evaluating the effectiveness of the optimized solutions compared to conventional solutions (materials based on concrete, polyethylene or borosilicate-containing resins). The evaluation metrics are comprehensive and include parameters such as shield thickness, total weight, cumulative dose rate and economic cost. The results of the study show that the solutions optimized by the intelligent multi-objective shielding optimization method exhibit unique properties. These solutions stand out from the crowd, providing designers with richer and more varied options. The optimization technique skillfully navigates between ensuring optimal radiation protection and conserving material usage, culminating in a series of Pareto-optimal solutions that demonstrate the effectiveness of the method. The intelligent optimization procedure based on the NSGA-Ⅲ was successfully applied to the optimization of shielding solutions for the hatch region of a spent fuel transport ship. The derived optimization scheme proves a lightweight design concept and does not compromise the strict radiation protection standards. The multi-objective optimization algorithm outperforms traditional radiation shielding design methods in quickly finding a solution that meets the shielding requirements while simultaneously weighing multiple objectives, such as the dose rate, volume and weight of the shielding material. This approach significantly improves the efficiency of shielding design. The methodology described in this paper has broad applicability and is particularly suitable for scenarios involving optimization of photon shielding in major shielding geometries. However, the methodology encounters certain limitations when dealing with complex geometries such as localized shielding challenges with penetrating members, and it is recommended that 3D Monte-Carlo method is used to optimize the design in such cases.

Satyanarayan Bramha, S. Chandrasekaran

Studies and evaluations of the detector characteristics of a high-resolution multichamber alpha spectrometer and its calibration using certified mixed standard sources of 239Pu, 241Am, and 244Cm for measuring alpha-emitting radionuclides dedicated to environmental samples. The efficiency and resolution were evaluated for each potential distance between the source and the detector across all four solid-state ORTEC-ULTRA AS detectors. The results obtained from the characteristics performance of the alpha from the standard alpha sources are described in detail in the paper, and also a case study for the environmental application shows very good recovery using the alpha spectrometer.

Pei-Hong Gu

The QCD Lagrangian contains a CP violating gluon density term with a physical coefficient θ¯. The upper bound on the electric dipole moment of neutron requires the value of θ¯ to be extremely small. The tiny θ¯ is commonly known as the strong CP problem. In order to solve this puzzle, we construct a θ¯-characterized mirror symmetry between a pair of twin dark sectors with respective discrete symmetries. By taking a proper phase rotation of dark fields, we can perfectly remove the parameter θ¯ from the full Lagrangian. In our scenario, the discrete symmetry breaking, which are responsible for the mass generation of dark colored fermions and dark matter fermions, can be allowed near the TeV scale. This means different phenomena from the popular axion models with high scale Peccei-Quinn global symmetry breaking.

N. Ackermann, S. Armbruster, H. Bonet et al.

Abstract The CONUS+ experiment aims to detect coherent elastic neutrino-nucleus scattering (CE $$\nu $$ ν NS) of reactor antineutrinos on germanium nuclei in the fully coherent regime, continuing on this way the CONUS physics program started at the Brokdorf nuclear power plant, Germany. The CONUS+ setup is installed in the nuclear power plant in Leibstadt, Switzerland, at a distance of 20.7 m from the 3.6 GW thermal power reactor core. The CE $$\nu $$ ν NS signature will be measured with the same four point-contact high-purity germanium (HPGe) detectors produced for the former experiment, however refurbished and with optimized low energy thresholds of about 160  $$\hbox {eV}_{ee}$$ eV ee . To suppress the background in the CONUS+ detectors, the passive and active layers of the original CONUS shield were modified such to fit better to the significantly changed background conditions at the new experimental location. New data acquisition and monitoring systems were developed. A direct network connection between the experiment and the Max-Planck-Institut für Kernphysik (MPIK) makes it possible to control and monitor data acquisition in real time. The impact of all these modifications is discussed with particular emphasis on the resulting CE $$\nu $$ ν NS signal prediction for the first data collection phase of CONUS+. Prospects of the planned upgrade in a second phase integrating new larger HPGe detectors are also discussed.

T. Enoto, M. Tsurumi, Y. Ikkatai et al.

Teruaki Enoto,a,b,∗ Miwa Tsurumi, Yuko Ikkatai, Ting Wu, Daohong Wang, Taro Shinoda, f Kazuhiro Nakazawa, Naoki Tsuji, Gabriel Sousa Diniz, Jun Kataoka, Masashi Kamogawa, Toru Takagaki, j Shoko Miyake, Takeshi Morimoto, Yoshitaka Nakamura and Harufumi Tsuchiya Department of Physics, Graduate School of Science, Kyoto University, Kyoto, Japan Extreme Natural Phenomena RIKEN Hakubi Research Team, Cluster of Pioneering Research, RIKEN, Saitama, Japan Graduate School of Science and Engineering, Aoyama Gakuin University, Kanagawa, Japan Institute of Human and Social Sciences, Kanazawa University, Ishikawa, Japan Department of Electrical, Electronic and Computer Engineering, Gifu University, Gifu, Japan f Institute for Space-Earth Environmental Research, Nagoya University, Aichi, Japan Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Aichi, Japan Faculty of Science and Engineering, Waseda University, Tokyo, Japan Global Center for Asian and Regional Research, University of Shizuoka, Shizuoka, Japan TAC Inc., Kyoto, Japan National Institute of Technology (KOSEN), Ibaraki College, Ibaraki, Japan Faculty of Science and Engineering, Kindai University, Osaka, Japan Department of Electrical Engineering, Kobe City College of Technology, Hyogo, Japan Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, Japan

The BESIII collaboration, M. Ablikim, M. N. Achasov et al.

Abstract Using e + e − collision datasets corresponding to a total integrated luminosity of 21.7 fb −1 collected with the BESIII detector at the BEPCII collider at center-of-mass energies ranging from 4.009 GeV to 4.951 GeV, the energy-dependent cross sections of e + e − → p K − Λ ¯ + c . c . $$ {e}^{+}{e}^{-}\to p{K}^{-}\overline{\Lambda}+c.c. $$ are measured for the first time. By fitting these energy-dependent cross sections, we search for the excited ψ states ψ(4160) and ψ(4415), and the vector charmonium-like states ψ(4230), ψ(4360), and ψ(4660). No evidence for these is observed and the upper limits on the branching fractions of these states decaying into p K − Λ ¯ + c . c . $$ p{K}^{-}\overline{\Lambda}+c.c. $$ are set at the 90% confidence level.

Zhi-Jie Sun, Si-Yang Wang, Zhi-Qing Zhang et al.

Abstract In this work, we investigate the semileptonic decays of $$B_{c}$$ B c meson to $$\eta _{c}(1S,2S,3S)$$ η c ( 1 S , 2 S , 3 S ) , $$\psi (1S,2S,3S)$$ ψ ( 1 S , 2 S , 3 S ) and X(3872) within the framework of covariant light-front quark model (CLFQM). We combine the helicity amplitudes via the corresponding form factors to obtain the branching ratios of the semileptonic decays $$B_{c}\rightarrow \eta _{c}(1S, 2S, 3S)\ell \nu _{\ell }$$ B c → η c ( 1 S , 2 S , 3 S ) ℓ ν ℓ , $$B_{c}\rightarrow \psi (1S, 2S, 3S))\ell \nu _{\ell }$$ B c → ψ ( 1 S , 2 S , 3 S ) ) ℓ ν ℓ and $$B_{c}\rightarrow X(3872)\ell \nu _{\ell }$$ B c → X ( 3872 ) ℓ ν ℓ , with $$\ell =e,\mu ,\tau $$ ℓ = e , μ , τ . In view of the $$R_{J/\Psi }$$ R J / Ψ anomaly released by the LHCb collaboration, it is necessary to systematically calculate the ratios $$R_X$$ R X with $$X=\psi (1S,2S,3S),\eta _c(1S,2S,3S),X(3872)$$ X = ψ ( 1 S , 2 S , 3 S ) , η c ( 1 S , 2 S , 3 S ) , X ( 3872 ) , which are helpful for checking the lepton flavor universality (LFU). We also take into account another two physical observables, the longitudinal polarization fraction $$f_{L}$$ f L and the forward–backward asymmetry $$A_{FB}$$ A FB , which can provide new clues for understanding the $$R_{J /\Psi }$$ R J / Ψ anomaly. Such theoretical predictions are necessary and interesting, and can be tested in future LHCb experiments.

M. Tsurumi

Miwa Tsurumi,a,b,∗ Teruaki Enoto, Yuko Ikkatai, Ting Wu, Daohong Wang, Taro Shinoda, f Kazuhiro Nakazawa, Noki Tsuji, Diniz Gabriel, Jun Kaoataoka, Ryoji Iwashita, Nanase Koshikawa, Masashi Kamogawa, Toru Takagaki, j Shoko Miyake, Dai Tomioka, Takeshi Morimoto, Yoshitaka Nakamura and Harufumi Tsuchiya Department of Physics, Graduate School of Science, Kyoto University, Kyoto, Japan Graduate School of Science and Engineering, Aoyama Gakuin University, Kanagawa, Japan Extreme Natural Phenomena RIKEN Hakubi Research Team, Cluster of Pioneering Research, RIKEN, Saitama, Japan Institute of Human and Social Sciences, Kanazawa University, Ishikawa, Japan Department of Electrical, Electronic and Computer Engineering, Gifu University, Gifu, Japan f Institute for Space-Earth Environmental Research, Nagoya University, Aichi, Japan Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Aichi, Japan Faculty of Science and Engineering, Waseda University, Tokyo, Japan Global Center for Asian and Regional Research, University of Shizuoka, Shizuoka, Japan TAC Inc., Kyoto, Japan National Institute of Technology (KOSEN), Ibaraki College, Ibaraki, Japan Faculty of Science and Engineering, Kindai University, Osaka, Japan Department of Electrical Engineering, Kobe City College of Technology, Hyogo, Japan Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki, Japan

Rico G. Fausch, Janis A. Schertenleib, Peter Wurz

Spacecraft flybys provide access to the chemical composition of the gaseous envelope of the planetary object. Typical relative encounter velocities range from km/s to tens of km/s in flybys. For speeds exceeding about 5 km/s, modern mass spectrometers analyzing the rapidly encountering gas suffer from intrinsic hypervelocity impact-induced fragmentation processes causing ambiguous results when analyzing complex molecules. In this case, instruments use an antechamber, inside which the incoming species collide many times with the chamber wall. These collisions cause the desired deceleration and thermalization of the gas molecules. However, these collisions also dissociate molecular bonds, thus fragmenting the molecules, and possibly forming new ones precluding scientists from inferring the actual chemical composition of the sampled gas. We developed a novel time-of-flight mass spectrometer that handles relative encounter velocities of up to 20 km/s omitting an antechamber and its related fragmentation. It analyzes the complete mass range of <i>m/z</i> 1 to 1000 at an instance. This innovation leads to unambiguous analysis of complex (organic) molecules. Applied to Enceladus, Europa or Io, it will provide reliable chemical composition datasets for exploration of the Solar System to determine its status, origin and evolution.

Zikang Chen, Jiajun Liao, Jiajie Ling et al.

Abstract The presence of a super-light sterile neutrino can lead to a dip in the survival probability of solar neutrinos, and explain the suppression of the upturn in the low energy solar neutrino data. In this work, we systematically study the survival probabilities in the 3+1 framework by taking into account of the non-adiabatic transitions and the coherence effect. We obtain an analytic equation that can predict the position of the dip. We also place constraints on the parameter space of sterile neutrinos by using the latest Borexino and KamLAND data. We find that the low and high energy neutrino data at Borexino are sensitive to different regions in the sterile neutrino parameter space. In the case with only θ 01 being nonzero, the 8B data sets the strongest bounds at ∆ m 01 2 $$ \Delta {m}_{01}^2 $$ ≈ (1.1 ∼ 2.2) ∆ m 21 2 $$ \Delta {m}_{21}^2 $$ , while the low energy neutrino data is more sensitive to other mass-squared regions. The lowest bounds on ∆ m 01 2 $$ \Delta {m}_{01}^2 $$ from the pp data can reach 10 −12 eV2 because of the coherence effect. Also, due to the presence of non-adiabatic transitions, the bounds in the range of 10 −9 eV2 ≲ ∆ m 01 2 $$ \Delta {m}_{01}^2 $$ ≲ 10 −5 eV2 become weaker as ∆ m 01 2 $$ \Delta {m}_{01}^2 $$ or sin2 2θ 01 decreases. We also find that in the case with only θ 02 or θ 03 being nonzero, the low energy solar neutrino data set similar but weaker bounds as compared to the case with only θ 01 being nonzero. However, the bounds from the high energy solar data and the KamLAND data are largely affected by the sterile mixing angles.

Alexandre M. R. Almeida, Júlio C. Fabris, Mahamadou Hamani Daouda et al.

We propose a unimodular version of the Brans–Dicke theory designed with a constrained Lagrangian formulation. The resulting field equations are traceless. The vacuum solutions in the cosmological background reproduce the corresponding solutions of the usual Brans–Dicke theory but with a cosmological constant term. A perturbative analysis of the scalar modes is performed and stable and unstable configurations appear, in contrast with the Brans–Dicke case for which only stable configurations occur. On the other hand, tensorial modes in this theory remain the same as in the traditional Brans–Dicke theory.

Leonardo Fernández-Jambrina

Due to the accelerated expansion of the universe, the possibilities for the formation of singularities has changed from the classical Big Bang and Big Crunch singularities to include a number of new scenarios. In recent papers it has been shown that such singularities may appear in inflationary cosmological models with a fractional power scalar field potential. In this paper we enlarge the analysis of singularities in scalar field cosmological models by the use of generalised power expansions of their Hubble scalars and their scalar fields in order to describe all possible models leading to a singularity, finding other possible cases. Unless a negative scalar field potential is considered, all singularities are weak and of type IV.

Laur Järv, Joosep Lember

We construct global phase portraits of inflationary dynamics in teleparallel gravity models with a scalar field nonminimally coupled to torsion scalar. The adopted set of variables can clearly distinguish between different asymptotic states as fixed points, including the kinetic and inflationary regimes. The key role in the description of inflation is played by the heteroclinic orbits that run from the asymptotic saddle points to the late time attractor point and are approximated by nonminimal slow roll conditions. To seek the asymptotic fixed points, we outline a heuristic method in terms of the “effective potential” and “effective mass”, which can be applied for any nonminimally coupled theories. As particular examples, we study positive quadratic nonminimal couplings with quadratic and quartic potentials and note how the portraits differ qualitatively from the known scalar-curvature counterparts. For quadratic models, inflation can only occur at small nonminimal coupling to torsion, as for larger coupling, the asymptotic de Sitter saddle point disappears from the physical phase space. Teleparallel models with quartic potentials are not viable for inflation at all, since for small nonminimal coupling, the asymptotic saddle point exhibits weaker than exponential expansion, and for larger coupling, it also disappears.

I. V. Mednikov, V. V. Vasilyev, A. S. Busygin et al.

The article provides a brief description of organizational and technical measures aimed at ensuring radiation safety during the decommissioning of the heavy-water research nuclear reactor of Institute for Theoretical and Experimental Physics after A.I. Alikhanov of National Research Centre «Kurchatov Institute». Information is provided on the history and features of the operation of the reactor, including parameters and characteristics that are significant for planning and conducting work. The peculiarities of legal regulation in the field of ensuring radiation safety are given; regulatory acts and rules accompanying other activities during decommissioning and directly related to radiation safety are also considered. The paper describes the work done in preparation for dismantling, the initial and current state of the installation, forthcoming work with examples of dismantled equipment. Methods for handling radioactive waste arising during decommissioning are considered, including methods for fragmentation of large structural elements (examples of mechanical devices are given), methods for sorting according to different specific activity (high activity, low activity), radionuclide composition and physical properties (solid, metallic, non-metallic, liquid). A special method for handling liquid radioactive waste is described, which includes the collection and temporary storage system. To assess the radiation situation at workplaces during the dismantling of the reactor structures, calculations of radiation transfer were carried out on the running and shutdown reactor, during which it was established that the expected dose to the personnel when performing activities on decommissioning of TBR is much lower than the limit values, established by regulatory documents. In accordance with the estimated radiation doses, rules and instructions for personnel were determined, including the procedure for using personal protective equipment, the necessary measures for surface decontamination, etc. Information is given on the procedure for radiation monitoring at all stages of dismantling and at the final stages of decommissioning including control of premises, personnel, equipment, waste of various types, atmospheric air.

Binbin Qi, Yang Li, Danyang Zhu et al.

The Back-n white neutron beam line, which uses back-streaming white neutrons from the spallation target of the China Spallation Neutron Source, is used for nuclear data measurements. A Micromegas-based neutron detector with two variants was specially developed to measure the beam spot distribution for this beam line. In this article, the design, fabrication, and characterization of the detector are described. The results of the detector performance tests are presented, which include the relative electron transparency, the gain and the gain uniformity, and the neutron beam profile reconstruction capability. The result of the first measurement of the Back-n neutron beam spot distribution is also presented.

H. Dimov, M. Radomirov, R.C. Rashkov et al.

Abstract According to AdS/CFT duality semi-classical strings in the Schrodinger space­ time is conjectured to be a holographic dual to dipole CFT. In this paper we consider pulsating strings in five-dimensional Schrodinger space times five-sphere. We have found classical string solutions pulsating entirely in the Schrodinger part of the background. We quantize the theory semi-classically and obtain the wave function of the problem. We have found the corrections to the energy, which by duality are supposed to give anomalous dimensions of certain operators in the dipole CFT.

Nikita Blinov, Sebastian A. R. Ellis, Anson Hook

Abstract Light bosonic fields mediate long range forces between objects. If these fields have self-interactions, i.e., non-quadratic terms in the potential, the experimental constraints on such forces can be drastically altered due to a screening (chameleon) or enhancement effect. We explore how technically natural values for such self-interaction coupling constants modify the existing constraints. We point out that assuming the existence of these natural interactions leads to new constraints, contrary to the usual expectation that screening leads to gaps in coverage. We discuss how screening can turn fundamentally equivalence principle (EP)-preserving forces into EP-violating ones. This means that when natural screening is present, searches for EP violation can be used to constrain EP-preserving forces. We show how this effect enables the recently discovered stellar triple system PSR J0337+1715 to place a powerful constraint on EP-preserving fifth forces. Finally, we demonstrate that technically natural cubic self-interactions modify the vacuum structure of the scalar potential, leading to new constraints from spontaneous and induced vacuum decay.