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

Hao Geng

Abstract The Karch-Randall braneworld provides a natural set-up to study the Hawking radiation from a black hole using holographic tools. Such a black hole lives on a brane and is highly quantum yet has a holographic dual as a higher dimensional classical theory that lives in the ambient space. Moreover, such a black hole is coupled to a nongravitational bath which is absorbing its Hawking radiation. This allows us to compute the entropy of the Hawking radiation by studying the bath using the quantum extremal surface prescription. The quantum extremal surface geometrizes into a Ryu-Takayanagi surface in the ambient space. The topological phase transition of the Ryu-Takayanagi surface in time from connecting different portions of the bath to the one connecting the bath and the brane gives the Page curve of the Hawking radiation that is consistent with unitarity. Nevertheless, there doesn’t exit a derivation of the quantum extremal surface prescription and its geometrization in the Karch-Randall braneworld. In this paper, we fill this gap. We mainly focus on the case that the ambient space is (2+1)-dimensional for which explicit computations can be done in each description of the set-up. We show that the topological phase transition of the Ryu-Takayanagi surface corresponds to the formation of the replica wormhole on the Karch-Randall brane as the dominant contribution to the replica path integral. For higher dimensional situations, we show that the geometry of the brane satisfies Einstein’s equation coupled with conformal matter. We comment on possible implications to the general rule of gravitational path integral from this equation.

Oscar Fuentealba, Iva Lovrekovic, David Tempo et al.

Abstract An enhanced version of the conformal BMS3 algebra is presented. It is shown to emerge from the asymptotic structure of an extension of conformal gravity in 3D by Pope and Townsend that consistently accommodates an additional spin-2 field, once it is endowed with a suitable set of boundary conditions. The canonical generators of the asymptotic symmetries then span a precise nonlinear W(2,2,2,2,1,1,1) algebra, whose central extensions and coefficients of the nonlinear terms are completely determined by the central charge of the Virasoro subalgebra. The wedge algebra corresponds to the conformal group in four dimensions SO(4, 2) and therefore, enhanced conformal BMS3 can also be regarded as an infinite-dimensional nonlinear extension of the AdS5 algebra with nontrivial central extensions. It is worth mentioning that our boundary conditions might be considered as a starting point in order to consistently incorporate either a finite or an infinite number of conformal higher spin fields.

Fei Gao, Julia Harz, Chandan Hati et al.

Abstract A large primordial lepton asymmetry can lead to successful baryogenesis by preventing the restoration of electroweak symmetry at high temperatures, thereby suppressing the sphaleron rate. This asymmetry can also lead to a first-order cosmic QCD transition, accompanied by detectable gravitational wave (GW) signals. By employing next-to-leading order dimensional reduction we determine that the necessary lepton asymmetry is approximately one order of magnitude smaller than previously estimated. Incorporating an updated QCD equation of state that harmonizes lattice and functional QCD outcomes, we pinpoint the range of lepton flavor asymmetries capable of inducing a first-order cosmic QCD transition. To maintain consistency with observational constraints from the Cosmic Microwave Background and Big Bang Nucleosynthesis, achieving the correct baryon asymmetry requires entropy dilution by approximately a factor of ten. However, the first-order QCD transition itself can occur independently of entropy dilution. We propose that the sphaleron freeze-in mechanism can be investigated through forthcoming GW experiments such as μAres.

Isomiddin Nishonov, Javlon Rayimbaev, Saeed Ullah Khan et al.

Abstract Testing dark matter effects on gravity around black holes in the framework of gravity theories through observational data is an essential task of relativistic astrophysical studies. In this work, we first obtain a new spacetime solution for a black hole surrounded by perfect fluid dark matter (PFDM) in modified gravity (MOG). The MOG field is assumed to be a gravitational vector field. We investigate the vector fields with combined effects of PFDM on spacetime properties: event horizon radius, scalar invariants such as the Ricci scalar, the square of the Ricci tensor, and Kretchman scalars. We investigate the circular motion of test particles in the spacetime of the black hole, taking into account the MOG field interaction on the particle geodesics. The energy and angular momentum of the particles corresponding to circular orbits are studied. In addition, we explore how the PFDM and MOG fields change the position of innermost stable circular orbits (ISCOs) and their corresponding energy and angular momentum values. Moreover, we study the energy efficiency rate around the black hole in the Novikov and Thorns thin accretion disc model. We analyze collisional cases of the particles near the black hole and study the effects of the fields on the critical angular momentum in which particles can collide near the black hole and the center-of-mass energy of the colliding particles.

M. Beccaria

We consider 4d N=4 U(N) SYM and the leading giant graviton correction at large N to the Schur defect 2-point functions of 12-BPS Wilson lines in rank-k symmetric and antisymmetric representations. We study in particular the large k limit for the symmetric case and the regime 1≪k≪N in the antisymmetric one. In both cases we present exact results for the correction. Wilson lines in symmetric/antisymmetric representations admit a description in terms of D3k and D5k brane probes representing a collection of k fundamental strings. In this picture, giant graviton corrections come from fluctuations of brane probes in the presence of a wrapped D3 brane giant graviton. In the antisymmetric case, our leading correction matches the half-index of the 4d N=4 Maxwell theory living on the disk which is a part of the giant graviton divided out by the D5k probe, as recently proposed in arXiv:2404.08302. For the symmetric case at large k, we derive an explicit exact residue formula for the leading large N correction.

Maria Manuela Saez

Core-collapse supernovae (SNe) are one of the most powerful cosmic sources of neutrinos, with energies of several MeV. The emission of neutrinos and antineutrinos of all flavors carries away the gravitational binding energy of the compact remnant and drives its evolution from the hot initial to the cold final states. Detecting these neutrinos from Earth and analyzing the emitted signals present a unique opportunity to explore the neutrino mass ordering problem. This research outlines the detection of neutrinos from SNe and their relevance in understanding the neutrino mass ordering. The focus is on developing a model-independent analysis strategy, achieved by comparing distinct detection channels in large underground detectors. The objective is to identify potential indicators of mass ordering within the neutrino sector. Additionally, a thorough statistical analysis is performed on the anticipated neutrino signals for both mass orderings. Despite uncertainties in supernova explosion parameters, an exploration of the parameter space reveals an extensive array of models with significant sensitivity to differentiate between mass orderings. The assessment of various observables and their combinations underscores the potential of forthcoming supernova observations in addressing the neutrino mass ordering problem.

Christoph Dlapa, Martin Helmer, Georgios Papathanasiou et al.

Abstract We provide evidence through two loops, that rational letters of polylogarithmic Feynman integrals are captured by the Landau equations, when the latter are recast as a polynomial of the kinematic variables of the integral, known as the principal A-determinant. Focusing on one loop, we further show that all square-root letters may also be obtained, by re-factorizing the principal A-determinant with the help of Jacobi identities. We verify our findings by explicitly constructing canonical differential equations for the one-loop integrals in both odd and even dimensions of loop momenta, also finding agreement with earlier results in the literature for the latter case. We provide a computer implementation of our results for the principal A-determinants, symbol alphabets and canonical differential equations in an accompanying Mathematica file. Finally, we study the question of when a one-loop integral satisfies the Cohen-Macaulay property and show that for almost all choices of kinematics the Cohen-Macaulay property holds. Throughout, in our approach to Feynman integrals, we make extensive use of the Gel’fand, Graev, Kapranov and Zelevinskiĭ theory on what are now commonly called GKZ-hypergeometric systems whose singularities are described by the principal A-determinant.

Artem A. Kotov, Dmitry A. Glazov, Aleksei V. Malyshev et al.

The rigorous two-center approach based on the dual-kinetically balanced finite-basis-set expansion is applied to one-electron, heteronuclear diatomic Bi-Au, U-Pb, and Cf-U quasimolecules. The obtained <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mi>σ</mi></mrow></semantics></math></inline-formula> ground-state energies are compared with previous calculations, when possible. Upon analysis of three different placements of the coordinate system’s origin in the monopole approximation of the two-center potential: (1) in the middle, between the nuclei, (2) in the center of the heavy nucleus, and (3) in the center of the light nucleus, a substantial difference between the results is found. The leading contributions of one-electron quantum electrodynamics (self-energy and vacuum polarization) are evaluated within the monopole approximation as well.

ZHOU Tao;TANG Jianyu;ZHANG Fan;LIU Wenbin

The movement and deposition of nanoparticles in supercritical carbon dioxide is a current international frontier subject. In the development of new nuclear reactors, using supercritical carbon dioxide Brayton cycle instead of traditional steam Rankine cycle can greatly improve the cycle efficiency, reduce equipment size and improve safety. In this new cycle, the movement and deposition of nanoparticles play a significant role under normal and abnormal operating conditions in nuclear power plants. Nanoparticles, due to their small particle size and higher relative surface energy, are more penetrable. When it under the thermophoresis force will emerge the thermophoresis deposition, causing collision and erosion to the pipeline. And it may be more destructive to supercritical devices or systems. To study the movement and deposition characteristics of nanoparticles in supercritical media, then further explore the factors affecting nanoparticles deposition, and find their qualitative and even quantitative relationship. This paper studies this problem from the aspects of particle size, wall temperature difference, incoming flow velocity, and so on to try to clarify the motion mechanism of nanoparticle deposition. In specific studies, stainless steel nanoparticles and supercritical carbon dioxide were selected as the objects, a 1 meter long horizontal straight pipe was taken as the flow geometric channel, based on the control single variable method, the factors affecting the thermophoresis deposition of nanoparticles were calculated and analyzed by Fluent software. According to the calculation to obtain the curve picture, the results show that the higher the fluid temperature, the greater the temperature gradient, and the greater the thermophoresis force on nanoparticles, which increases the dimensionless thermophoresis deposition velocity and the thermophoresis deposition rate. In addition, the increase of fluid temperature leads to the decrease of fluid viscosity and viscous resistance of particle movement, which also promotes the movement of particles and increases their deposition rate to a certain extent. In terms of particle size, the change of thermophoresis deposition rate caused by the change of particle size on a small scale (1100 nm) is more obvious than that on a large scale. With the increase of particle size, the thermophoresis force increases, but the increasing speed slows down. At the same time, the viscous resistance and lift increase in geometric multiples with the particle size. Under the combined action of these forces, the thermophoresis deposition efficiency decreases. The pipe diameter and flow velocity do not directly affect the thermophoresis deposition rate. The pipe diameter increases the average distance and reduces the thermophoresis gradient, while the flow velocity affects the heat transfer coefficient. In addition, the increase of external flow velocity enhances the carrying capacity of fluid, and nanoparticles are easier to be coerced out of the channel, thus reducing their thermophoresis deposition. Totally, for thermophoresis deposition, the temperature difference between the fluid and the wall is the most important factor affecting the deposition rate, and there is a positive correlation. The flow velocity, particle size, and pipe diameter are negatively correlated with deposition rate.

José Guilherme Milhano, Korinna Zapp

Abstract Interactions of hard partons in the Quark Gluon Plasma (QGP) created with relativistic heavy ion collisions lead to characteristic modifications of the internal structure of reconstructed jets. A large part of the observed jet sub-structure modifications stem from the QGP’s response to energy and momentum deposited by hard partons. Good control over medium response in theoretical calculations is thus instrumental to a quantitative understanding of medium modified (quenched) jets in heavy ion collisions. We present an improved way of handling the medium response in the jet quenching model Jewel and present results for a variety of jet sub-structure observables. The new recoil handling is more versatile and robust than the old scheme, giving a better control over many observables and, in particular, greatly improves the description of the jet mass.

Marieke Postma, Jorinde van de Vis

Abstract In electroweak baryogenesis the baryon asymmetry of the universe is created during the electroweak phase transition. The quantum transport equations governing the dynamics of the plasma particles can be derived in the vev-insertion approximation, which treats the vev-dependent part of the particle masses as a perturbation. We calculate the next-to-leading order (NLO) contribution to the CP-violating source term and CP-conserving relaxation rate, corresponding to Feynman diagrams for the self-energies with four mass insertions. We consider both a pair of Weyl fermions and a pair of complex scalars, that scatter off the bubble wall. We find: (i) The NLO correction becomes large for O $$ \mathcal{O} $$ (1) couplings. If only the Standard Model (SM) Higgs obtains a vev during the phase transition, this implies the vev-insertion approximation breaks down for top quarks. (ii) The resonant enhancement of the source term and relaxation rate, that exists at leading order in the limit of degenerate thermal masses for the fermions/scalars, persists at NLO.

Daniel Baumann, Carlos Duaso Pueyo, Austin Joyce et al.

Abstract A key insight of the bootstrap approach to cosmological correlations is the fact that all correlators of slow-roll inflation can be reduced to a unique building block — the four-point function of conformally coupled scalars, arising from the exchange of a massive scalar. Correlators corresponding to the exchange of particles with spin are then obtained by applying a spin-raising operator to the scalar-exchange solution. Similarly, the correlators of massless external fields can be derived by acting with a suitable weight-raising operator. In this paper, we present a systematic and highly streamlined derivation of these operators (and their generalizations) using tools of conformal field theory. Our results greatly simplify the theoretical foundations of the cosmological bootstrap program.

Sebastian Macaluso, David Shih

Abstract We apply computer vision with deep learning — in the form of a convolutional neural network (CNN) — to build a highly effective boosted top tagger. Previous work (the “DeepTop” tagger of Kasieczka et al) has shown that a CNN-based top tagger can achieve comparable performance to state-of-the-art conventional top taggers based on high-level inputs. Here, we introduce a number of improvements to the DeepTop tagger, including architecture, training, image preprocessing, sample size and color pixels. Our final CNN top tagger outperforms BDTs based on high-level inputs by a factor of ∼ 2-3 or more in background rejection, over a wide range of tagging efficiencies and fiducial jet selections. As reference points, we achieve a QCD background rejection factor of 500 (60) at 50% top tagging efficiency for fully-merged (non-merged) top jets with p T in the 800-900 GeV (350-450 GeV) range. Our CNN can also be straightforwardly extended to the classification of other types of jets, and the lessons learned here may be useful to others designing their own deep NNs for LHC applications.

Matthew Buican, Zoltan Laczko, Takahiro Nishinaka

Abstract Using the chiral algebra bootstrap, we revisit the simplest Argyres-Douglas (AD) generalization of Argyres-Seiberg S-duality. We argue that the exotic AD superconformal field theory (SCFT), T 3 , 3 2 $$ {\mathcal{T}}_{3,\frac{3}{2}} $$ , emerging in this duality splits into a free piece and an interacting piece, T X $$ {\mathcal{T}}_X $$ , even though this factorization seems invisible in the Seiberg-Witten (SW) curve derived from the corresponding M5-brane construction. Without a Lagrangian, an associated topological field theory, a BPS spectrum, or even an SW curve, we nonetheless obtain exact information about T X $$ {\mathcal{T}}_X $$ by bootstrapping its chiral algebra, X T X $$ {}_{\mathcal{X}}\left({\mathcal{T}}_X\right) $$ , and finding the corresponding vacuum character in terms of Affine Kac-Moody characters. By a standard 4D/2D correspondence, this result gives us the Schur index for T X $$ {\mathcal{T}}_X $$ and, by studying this quantity in the limit of small S 1, we make contact with a proposed S 1 reduction. Along the way, we discuss various properties of T X $$ {\mathcal{T}}_X $$ : as an N $$ \mathcal{N} $$ = 1 theory, it has flavor symmetry SU(3) × SU(2) × U(1), the central charge of X T X $$ {}_{\mathcal{X}}\left({\mathcal{T}}_X\right) $$ matches the central charge of the bc ghosts in bosonic string theory, and its global SU(2) symmetry has a Witten anomaly. This anomaly does not prevent us from building conformal manifolds out of arbitrary numbers of T X $$ {\mathcal{T}}_X $$ theories (giving us a surprisingly close AD relative of Gaiotto’s T N theories), but it does lead to some open questions in the context of the chiral algebra/4D N $$ \mathcal{N} $$ =2SCFT correspondence.

Massimiliano Grazzini, Stefan Kallweit, Dirk Rathlev et al.

Abstract We report on the first fully differential calculation for W ± Z production in hadron collisions up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. Leptonic decays of the W and Z bosons are consistently taken into account, i.e. we include all resonant and non-resonant diagrams that contribute to the process pp → ℓ ′± ν ℓ ′ ℓ + ℓ − +X both in the same-flavour (ℓ ′ = ℓ) and the different-flavour (ℓ ′ ≠ ℓ) channel. Fiducial cross sections and distributions are presented in the presence of standard selection cuts applied in the experimental W ± Z analyses by ATLAS and CMS at centre-of-mass energies of 8 and 13 TeV. As previously shown for the inclusive cross section, NNLO corrections increase the NNLO result by about 10%, thereby leading to an improved agreement with experimental data. The importance of NNLO accurate predictions is also shown in the case of new-physics scenarios, where, especially in high-p T categories, their impact can reach O 20 % $$ \mathcal{O}\left(20\%\right) $$ . The availability of differential NNLO predictions will play a crucial role in the rich physics programme that is based on precision studies of W ± Z signatures at the LHC.

M. V. Vedernikova, I. A. Pron, M. N. Savkin et al.

This paper focuses on occupational and public exposure during operation of disposal facilities receiving liquid and solid radioactive waste of various classes and provides a comparative analysis of the relevant doses: actual and calculated at the design stage. Occupational and public exposure study presented in this paper covers normal operations of a radioactive waste disposal facility receiving waste. Results: Analysis of individual and collective occupational doses was performed based on data collected during operation of near-surface disposal facilities for short-lived intermediate-, lowand very low-level waste in France, as well as nearsurface disposal facilities for long-lived waste in Russia. Further analysis of occupational and public doses calculated at the design stage was completed covering a near-surface disposal facility in Belgium and deep disposal facilities in the United Kingdom and the Nizhne-Kansk rock massive (Russia). The results show that engineering and technical solutions enable almost complete elimination of internal occupational exposure, whereas external exposure doses would fall within the range of values typical for a basic nuclear facility. Conclusion: radioactive waste disposal facilities being developed, constructed and operated meet the safety requirements effective in the Russian Federation and consistent with relevant international recommendations. It has been found that individual occupational exposure doses commensurate with those received by personnel of similar facilities abroad. Furthermore, according to the forecasts, mean individual doses for personnel during radioactive waste disposal would be an order of magnitude lower than the dose limit of 20 mSv/year. As for the public exposure, during normal operation, potential impact is virtually impossible by delaminating boundaries of a nuclear facility sanitary protection zone inside which the disposal facility is located and can be solely attributed to the use of public roads during radioactive waste transportation to the disposal facility site.

A. Burov

Typically x/y optical coupling is considered as unwanted and thus suppressed; particular exclusions are electron and ionization coolers. Could some special coupled modes be effectively applied for the LHC complex? Perhaps, the answer is positive: use of the circular modes in the injectors with their transformation into planar modes in the LHC allows both the space charge and beam-beam luminosity limitations to be significantly reduced, if not practically eliminated.

The ATLAS Collaboration, G. Aad, B. Abbott et al.

Abstract A search for top quark pair resonances in final states containing at least one electron or muon has been performed with the ATLAS experiment at the CERN Large Hadron Collider. The search uses a data sample corresponding to an integrated luminosity of 2.05 fb−1, which was recorded in 2011 at a proton-proton centre-of-mass energy of 7 TeV. No evidence for a resonance is found and limits are set on the production cross-section times branching ratio to $t\bar{t}$ for narrow and wide resonances. For narrow Z′ bosons, the observed 95 % Bayesian credibility level limits range from 9.3 pb to 0.95 pb for masses in the range of m Z′=500 GeV to m Z′=1300 GeV. The corresponding excluded mass region for a leptophobic topcolour Z′ boson (Kaluza-Klein gluon excitation in the Randall-Sundrum model) is m Z′<880 GeV ( $m_{g_{\mathrm{KK}}} < 1130~ \mathrm{GeV}$ ).

S. Becker, M. Bussmann, S. Raith et al.

The application of quadrupole devices with high field gradients and small apertures requires precise control over higher order multipole field components. We present a new scheme for performance control and tuning, which allows the illumination of most of the quadrupole device aperture because of the reduction of higher order field components. Consequently, the size of the aperture can be minimized to match the beam size achieving field gradients of up to 500  T m^{-1} at good imaging quality. The characterization method based on a Hall probe measurement and a Fourier analysis was confirmed using the high quality electron beam at the Mainz Microtron MAMI.

P. A. Seidl, C. M. Celata, A. Faltens et al.

Transverse beam combining is a cost-saving option employed in many designs for heavy ion fusion drivers. However, the resultant transverse phase space dilution must be minimized so as not to sacrifice focusability at the target. A prototype combining experiment has been completed employing four 3-mA Cs^{+} beams injected at 160 keV. The focusing elements upstream of the merge consist of four quadrupoles and a final combined-function element (quadrupole and dipole). Following the merge, the resultant single beam is transported in a single alternating gradient channel where the subsequent evolution of the distribution function is diagnosed. The results are in fair agreement with particle-in-cell simulations. They indicate that for some heavy ion fusion driver designs, the phase space dilution from merging is acceptable.