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

Wen-Xin Lai, Huajia Wang, Yongjiang Xu

Abstract Turning on the $$T\overline{T }$$ -deformation in a two-dimensional CFT provides a unique window to study explicitly how non-local features arise in the UV as a result of the deformation. A sharp signature is the dynamical emergence of an effective length-scale ∝ $$\sqrt{\mu }$$ that separates the local and non-local regimes of the deformed theory, effectively serving as a UV cut-off for computing observables in the local regime. In this paper, we study this phenomenon through the entanglement structures of the deformed theory. We focus on computing the Renyi entropies of single-interval sub-regions in the deformed vacuum states. We pay particular attention to the interplay between the bare entanglement cut-off inherited from the CFT computation and the effects from the $$T\overline{T }$$ deformations. Applying the general replica trick to the string theory formulation of $$T\overline{T }$$ -deformed CFTs, we derive an explicit representation of the deformed replica partition function as a weighted integral of the CFT results evaluated at a dynamical cut-off, which is integrated over. We computed in detail the kernel functions of the integral representation, and performed the saddle-point analysis in the semi-classical limit of small μ. We found that in addition to the perturbative saddle-point which identifies the dynamical cut-off with the bare entanglement cut-off, there exists another non-perturbative saddle-point that identifies the dynamical cut-off with the $$T\overline{T }$$ length-scale ∝ $$\sqrt{\mu }$$ , but whose contribution is exponentially small. We discuss how these non-perturbative effects can shed lights on the mechanism through which the $$T\overline{T }$$ length-scale may eventually replace the bare counter-part and become the effective entanglement cut-off.

Zi-Li Yue, Cheng-Jian Xiao, H. García-Tecocoatzi et al.

Abstract Inspired by the abundant structure near the threshold of the $$D^{(*)}K^{(*)}/\bar{D}^{(*)}K^{(*)},$$ D ( ∗ ) K ( ∗ ) / D ¯ ( ∗ ) K ( ∗ ) , we estimate the strong decay properties of the $$T_{c\bar{s}1}^{f/a}$$ T c s ¯ 1 f / a and $$T_{\bar{c}\bar{s}1}^{f/a}$$ T c ¯ s ¯ 1 f / a with $$I(J^{P})=0/1(1^{+})$$ I ( J P ) = 0 / 1 ( 1 + ) in $$DK^{*}$$ D K ∗ and $$\bar{D}K^{*}$$ D ¯ K ∗ molecular scenarios in the present paper. By employing the effective Lagrangian approach, the widths of the processes $$T_{c\bar{s}1}^{f}\rightarrow D^{*}K, D_{s}^{*}\eta , DK\pi ,$$ T c s ¯ 1 f → D ∗ K , D s ∗ η , D K π , $$T_{c\bar{s}1}^{a}\rightarrow D^{*}K, D_{s}^{*}\pi , DK\pi ,$$ T c s ¯ 1 a → D ∗ K , D s ∗ π , D K π , and $$T_{\bar{c}\bar{s}1}^{f/a}\rightarrow \bar{D}^{*}K, \bar{D}K\pi $$ T c ¯ s ¯ 1 f / a → D ¯ ∗ K , D ¯ K π are estimated. Considering the present estimations, we propose to search for $$T_{c\bar{s}1}^{f/a}$$ T c s ¯ 1 f / a states in $$D^{*}K$$ D ∗ K and $$D_{s}^{*}\pi /D_{s}^{*}\eta $$ D s ∗ π / D s ∗ η mass invariant spectra. Their ratios may serve as an important test of the molecular scenario.

The PADME collaboration, S. Bertelli, F. Bossi et al.

Abstract The PADME experiment at the Frascati DAΦNE LINAC has performed a search for the hypothetical X17 particle, with a mass of around 17 MeV, by scanning the energy of a positron beam striking a fixed target. The X17 should be produced from the resulting e + e − annihilation. Since the expected mass of this particle is only roughly known, data sidebands cannot be clearly defined. Furthermore, the need to keep the analysis blind to potentially sizable signal contributions prevents a clear assessment even of the quality of the data sample in this search. In light of these challenges, this paper presents an innovative strategy adopted by the PADME Collaboration to perform data quality checks without disclosing the X17 sample. Moreover, the procedure designed to eventually unblind the data is described, together with the statistical approach adopted to extract the limits on the coupling between the X17 and the Standard Model.

L. T. Hue, Khiem Hong Phan, T. T. Hong et al.

Abstract General expressions for one-loop contributions associated with lepton-flavor violating decays of the standard model-like Higgs boson $$h\rightarrow e_b^\pm e_a^\mp $$ h → e b ± e a ∓ and gauge boson $$Z\rightarrow e^\pm _b e_a^\mp $$ Z → e b ± e a ∓ are introduced in the unitary gauge. The results are used to discuss these decays as new physics signals in a minimal left-right symmetric model containing only one bidoublet Higgs and a $$SU(2)_R$$ S U ( 2 ) R Higgs doublet accommodating data of neutrino oscillations and $$(g-2)_{\mu }$$ ( g - 2 ) μ . The numerical investigation indicates that some of these decay rates can reach near future experimental sensitivities.

F. A. Barone, L. H. C. Borges, G. Flores-Hidalgo et al.

Abstract In this paper we propose a coupling between the complex scalar field and an external Dirac delta-like planar potential. The coupling is achieved through the Klein–Gordon current normal to the plane where the potential is concentrated. The results are obtained exactly and exhibit many peculiarities. We show that a complex scalar charge does not interact with the potential, but the potential modifies the interaction between two scalar charges if they are placed on opposite sides of the planar potential. When the coupling constant between the potential and the field goes to infinity, the classical field solutions satisfy a kind of MIT boundary conditions along the plane where the potential is concentrated.

Pietro Capuozzo, John Estes, Brandon Robinson et al.

Abstract In this note, we study 1/4- and 1/2-BPS co-dimension two superconformal defects in the 6d N $$ \mathcal{N} $$ = (2, 0) A N−1 SCFT at large N using their holographic descriptions as solutions of 11d supergravity. In this regime, we are able to compute the defect contribution to the sphere entanglement entropy and the change in the stress-energy tensor one-point function due to the presence of the defect using holography. From these quantities, we are then able to unambiguously compute the values for two of the twenty-nine total Weyl anomaly coefficients that characterize 4d conformal defects in six and higher dimensions. We are able to demonstrate the consistency of the supergravity description of the defect theories with the average null energy condition on the field theory side. For each class of defects that we consider, we also show that the A-type Weyl anomaly coefficient is non-negative. Lastly, we uncover and resolve a discrepancy between the on-shell action of the 7d 1/4-BPS domain wall solutions and that of their 11d uplift.

Nanrui Yang, Zhouyu Zhao, Heting Li

The fast polarization switching of undulator radiation has attracted more and more attention in recent years. In this paper, a new method is proposed for fast polarization switching of undulator radiation by using magnetic field modulation generated from low-current electromagnetic coils. The key point is that we propose to use the coils with a period length of an integral multiple of the undulator period, which can significantly reduce the required coil field. Through fast switching the power of coils, the radiation spectra of two undulators can be rapidly shifted into and out of the bandpass of a monochromator, enabling fast polarization switching for the user beamline. Based on this advantage, this method has strong potential to be implemented in a storage ring and a high switching frequency up to kilohertz can be expected.

Zhanbin Chen

This paper reports the development of a novel distorted wave approach based on the relativistic configuration interaction theory for calculating atomic structures, radiative properties, and collision dynamics of atoms or ions under external confinement. Due to its physical interpretations, the Hulthén potential, valid for many important areas (widely plasma environments) in physics and chemistry, such as atomic physics, solid-state physics, nuclear physics, particle physics, and astrophysics, is used to include the effect of plasma background. The Breit interaction and quantum electromagnetic dynamics effects are perturbatively included in the multi-electron Hamiltonian. Wave functions of bound and continuous states are obtained, which are analyzed by means of the Dirac equations. Interparticle interactions in the scattering matrix element of the system are described by the screened Coulomb interactions. As a test desk, the present approach is applied to the calculation of atomic structures and collision dynamics of an exemplary He-like S14+ ion embedded in a plasma. The energy eigenvalues, transition probabilities, and excitation cross sections are analyzed in detail in terms of the screening parameter. The results of the verification cases are compared to references from the literature, which show a good agreement. The present study not only opens up an opportunity to provide a simple and effective way for understanding the plasma shielding models for many-electron systems but also has important implications for a wide range of applications in astrophysics and laboratory plasma experiments.

Euclid Collaboration M. Schirmer, K. Thurmer, B. Bras et al.

Molecular contamination is a well-known problem in space flight. Water is the most common contaminant and alters numerous properties of a cryogenic optical system. Too much ice means that Euclid's calibration requirements and science goals cannot be met. Euclid must then be thermally decontaminated, a long and risky process. We need to understand how iced optics affect the data and when a decontamination is required. This is essential to build adequate calibration and survey plans, yet a comprehensive analysis in the context of an astrophysical space survey has not been done before. In this paper we look at other spacecraft with well-documented outgassing records, and we review the formation of thin ice films. A mix of amorphous and crystalline ices is expected for Euclid. Their surface topography depends on the competing energetic needs of the substrate-water and the water-water interfaces, and is hard to predict with current theories. We illustrate that with scanning-tunnelling and atomic-force microscope images. Industrial tools exist to estimate contamination, and we must understand their uncertainties. We find considerable knowledge errors on the diffusion and sublimation coefficients, limiting the accuracy of these tools. We developed a water transport model to compute contamination rates in Euclid, and find general agreement with industry estimates. Tests of the Euclid flight hardware in space simulators did not pick up contamination signals; our in-flight calibrations observations will be much more sensitive. We must understand the link between the amount of ice on the optics and its effect on Euclid's data. Little research is available about this link, possibly because other spacecraft can decontaminate easily, quenching the need for a deeper understanding. In our second paper we quantify the various effects of iced optics on spectrophotometric data.

Ke-Fan Wang, Tao Yang, Chen Fu et al.

Silicon-based fast timing detectors have been widely used in high-energy physics, nuclear physics, space exploration and other fields in recent years. However, silicon detectors often require complex low-temperature systems when operating in irradiation environment, and their detection performance decreases with the increase in the irradiation dose. Compared with silicon, silicon carbide (SiC) has a wider band gap, higher atomic displacement energy, saturated electron drift velocity and thermal conductivity. Simultaneously, the low-gain avalanche detector avoids cross talk and high noise from high multiplication due to its moderate gain, and thus can maintain a high detector signal without increasing noise. Thus, the 4H-SiC particle detector, especially the low-gain avalanche detector, has the potential to detect the minimal ionizing particles under extreme irradiation and high-temperature environments. In this work, the emphasis was placed on the design of a 4H-SiC low-gain avalanche detector (LGAD), especially the epitaxial structure and technical process which play main roles. In addition, a simulation tool—RASER (RAdiation SEmiconductoR)—was developed to simulate the performances including the electrical properties and time resolution of the 4H-SiC LGAD we proposed. The working voltage and gain effectiveness of the LGAD were verified by the simulation of electrical performances. The time resolution of the LGAD is (35.0 ± 0.2) ps under the electrical field of −800 V, which is better than that of the 4H-SiC PIN detector.

Zhe Zhao, Leonardo Modesto

Abstract In a large class of nonlocal as well as local higher derivative theories minimally coupled to the matter sector, we investigate the exactness of two different classes of homogeneous Gödel-type solutions, which may or may not allow closed time-like curves (CTC). Our analysis is limited to spacetimes solving the Einstein’s EoM, thus we can not exclude the presence of other Gödel-type solutions solving the EoM of local and nonlocal higher derivative theories but not the Einstein’s EoM. It turns out that the homogeneous Gödel spacetimes without CTC are basically exact solutions for all theories, while the metrics with CTC are not exact solutions of (super-)renormalizable local or nonlocal gravitational theories. Hence, the quantum renormalizability property excludes theories suffering of the Gödel’s causality violation. We also comment about nonlocal gravity non-minimally coupled to matter. In this class of theories, all the Gödel’s spacetimes, with or without CTC, are exact solutions at classical level. However, the quantum corrections, although perturbative, very likely spoil the exactness of such solutions. Therefore, we can state that the Gödel’s Universes with CTC and the super-renormalizability are mutually exclusive.

Takeshi Fukuyama, Toru Sato

Abstract The neutrinoless double beta decay is studied in the framework of left-right symmetric model. The coexistence of left and right handed currents induces rather complicated interactions between the lepton and hadron sectors, called < λ > mechanism and < η > mechanism in addition to the conventional effective neutrino mass < m ν > mechanism. In this letter, we study the possible magnification of < η > mechanism and the relatively vanishing of < λ > mechanism. The importance to survey 0νββ decay of different nuclei for specifying new physics beyond the Standard Model is also discussed.

Marzia Bordone, Mario Fernández Navarro

Abstract Several new physics scenarios that address anomalies in B-physics predict an enhancement of $$b \rightarrow s \tau \tau $$ b → s τ τ with respect to its Standard Model prediction. Such scenarios necessarily imply modifications of the lifetime ratio $$\tau _{B_{s}}/\tau _{B_{d}}$$ τ B s / τ B d and the lifetime difference $$\Delta \Gamma _{s}$$ Δ Γ s . In this work, we explore indirect bounds provided by these observables over new physics scenarios. We also estimate future projections, showing that future experimental and theoretical improvements on both $$\tau _{B_{s}}/\tau _{B_{d}}$$ τ B s / τ B d and $$\Delta \Gamma _{s}$$ Δ Γ s have the potential to provide bounds competitive with those directly extracted from $$b\rightarrow s \tau \tau $$ b → s τ τ transitions. After performing a model-independent analysis, we apply our results to the particular case of leptoquark mediators proposed to address the $$R_{D^{(*)}}$$ R D ( ∗ ) anomalies.

Martin Cederwall, Jakob Palmkvist

Abstract We formalise the teleparallel version of extended geometry (including gravity) by the introduction of a complex, the differential of which provides the linearised dynamics. The main point is the natural replacement of the two-derivative equations of motion by a differential which only contains terms of order 0 and 1 in derivatives. Second derivatives arise from homotopy transfer (elimination of fields with algebraic equations of motion). The formalism has the advantage of providing a clear consistency relation for the algebraic part of the differential, the “dualisation”, which then defines the dynamics of physical fields. It remains unmodified in the interacting BV theory, and the full non-linear models arise from covariantisation. A consequence of the use of the complex is that symmetry under local rotations becomes as good as manifest, instead of arising for a specific combination of tensorial terms, for less obvious reasons. We illustrate with a derivation of teleparallel Ehlers geometry, where the extended coordinate module is the adjoint module of a finite-dimensional simple Lie group.

Phung Van Dong, Tran Ngoc Hung, Duong Van Loi

Abstract Quark has an electric charge either $$-1/3$$ - 1 / 3 or 2/3 and a baryon number 1/3, where the divisions 3’s match the color number. Although the electric charge and the baryon number have a nature distinct from the color charge, the matching is necessary for the standard model or a relevant $$B-L$$ B - L extension consistent at quantum level, since the relevant anomaly $$[SU(2)_L]^2U(1)_A$$ [ S U ( 2 ) L ] 2 U ( 1 ) A for $$A=Y$$ A = Y or $$B-L$$ B - L must vanish. If elementary particles have a new U(1) charge differently from A, such anomaly is not cancelled for each family. However, if we demand that the anomaly is cancelled over all families, this relates the color number to the family number instead of the electric charge and baryon number, and interestingly the family number guides us to a novel U(1) theory. We will discuss the implication of this theory for neutrino mass, recent W-boson mass anomaly, FCNC, and particle colliders.

D. Carney, T. Cecil, J. Ellis et al.

A wide range of quantum sensing technologies are rapidly being integrated into the experimental portfolio of the high energy physics community. Here we focus on sensing with atomic interferometers; mechanical devices read out with optical or microwave fields; precision spectroscopic methods with atomic, nuclear, and molecular systems; and trapped atoms and ions. We give a variety of detection targets relevant to particle physics for which these systems are uniquely poised to contribute. This includes experiments at the precision frontier like measurements of the electron dipole moment and electromagnetic fine structure constant and searches for fifth forces and modifications of Newton's law of gravity at micron-to-millimeter scales. It also includes experiments relevant to the cosmic frontier, especially searches for gravitional waves and a wide variety of dark matter candidates spanning heavy, WIMP-scale, light, and ultra-light mass ranges. We emphasize here the need for more developments both in sensor technology and integration into the broader particle physics community.

Sebastian Mizera, Sabrina Pasterski

Abstract Celestial holography expresses S $$ \mathcal{S} $$ -matrix elements as correlators in a CFT living on the night sky. Poincaré invariance imposes additional selection rules on the allowed positions of operators. As a consequence, n-point correlators are only supported on certain patches of the celestial sphere, depending on the labeling of each operator as incoming/outgoing. Here we initiate a study of the celestial geometry, examining the kinematic support of celestial amplitudes for different crossing channels. We give simple geometric rules for determining this support. For n ≥ 5, we can view these channels as tiling together to form a covering of the celestial sphere. Our analysis serves as a stepping off point to better understand the analyticity of celestial correlators and illuminate the connection between the 4D kinematic and 2D CFT notions of crossing symmetry.

H. Goutte, A. Navin

Caen, in Normandy, France, is famous as the home of William the Conqueror. Equally well known in the field of nuclear physics is the Grand Accélérateur National d’Ions Lourds (GANIL) laboratory and its major upgrade of the existing infrastructure, Système de Production d’Ions RAdioactifs en Ligne de 2e génération (SPIRAL2) facility. GANIL is primarily focused on cutting edge research in fundamental nuclear physics using ion beams and is supplemented by strong programs in acceleratorbased atomic physics, condensed matter physics, radiobiology, and industrial applications. For many decades, GANIL has provided Highintensity stable beams (12C to 238U), beams of short-lived nuclei (Radioactive Ion Beams), produced both by in-flight separation (lifetimes ~ μs) and isotope separation on-line (ISOL) technique (lifetimes ~ ms). The five-cyclotron complex delivers stable beams from energies ~1 MeV to 95 MeV per mass unit with currents up to 10 μA, fragmentation beams up to ~ 50 MeV/A, and reaccelerated beams (SPIRAL1) from 1.2 MeV/A to 25 MeV/A (~40 isotopes). The intensities of the radioactive beams range from a few particles/s to ~107 p/s. The new superconducting linear accelerator (LINAC), in addition to very highintensity light beams, also provides a fourth type of beam, namely neutrons, to the already available arsenal of beams. These numerous types of beams are coupled to versatile detection facilities that allow the exploration of the behavior of nuclei in the phase space of excitation energy, angular momentum, and isospin. The first volume of Nuclear News (1991) portrayed the nuclear physics activities at GANIL, followed by the SPIRAL1 project (1995) and interdisciplinary physics (2000). In this article we present the evolution of the facility starting with the cyclotrons, the various associated detectors, and the current status of SPIRAL2. Figures 1 and 2 illustrate the cyclotron and LINAC complexes and their associated experimental halls. These complexes will be connected through a planned future project. GANIL, a multibeam facility, has been delivering a wide spectrum of stable and radioactive ion beams since 1983. Between 1983 and 1990, the facility relied on a cascade of three warm cyclotrons (KC0 = 30, KCSS1 = 380, KCSS2 = 380). Subsequently, a second injector was added. Various techniques were developed to increase the beam intensities, the number of isotopes, and the reliability of these beams. A major upgrade, in 2001, was the availability of reaccelerated radioactive ions from the SPIRAL1 facility. The cyclotrons serve as the driver for the production of radioactive atoms in a thick carbon target that can be reaccelerated by the new Cyclotron pour Ions de Moyenne Energie (CIME) (K = 265) up to a maximum energy of 25MeV/u (the highest in the world today). A review of the work done using SPIRAL1 beams till 2010 can be found in Ref. [1]. An upgrade, started in 2014, for increasing the number of reaccelerated beams using a Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source coupled with a charge breeder, extends those available with the existing Electron Cyclotron Resonance (ECR) ion source. This, added to the already available secondary beams by using the inflight method and stable beams, makes GANIL the only facility with this variety of beams. A continuous development of new and more intense stable beams, post-accelerated radioactive beams where GANIL has a niche, is ongoing. In parallel, there has been a continuous evolution in the detection systems, including the addition of various new detectors (discussed below). The functioning of the cyclotrons that has decreased in the last few years as a result of sharing the resources for construction of SPIRAL2, is being ramped up.

D. Pantelica, C. Niţă, R. Ionescu et al.

Ion accelerators have a fundamental role in atomic and nuclear studies as well as in applied physics, including the modification and characterization of materials. The precise knowledge of the energy of accelerated ions is of utmost importance, especially for cross-section measurements or for accurate depth profiling using narrow resonances. The 3 MV Cockcroft–Walton tandem accelerator of IFIN-HH from HVEC was installed in 2012. The machine is mainly dedicated to ion beam analysis, ion implantation, and astrophysics studies at low energy. In this work, we report on the first calibration for alpha particles of the terminal voltage using a technique based on Rutherford backscattering spectrometry measurements. The energies of the α particles from a mixed spectroscopic 239Pu + 241Am α source are compared with the energies of 4He projectiles backscattered into a silicon detector by carbon and gold layers. The position of the 16O(α,α) 16O resonance around 3.038 MeV at backscattering angles of 145° and 165° was remeasured. Our results are compared with recent results reported in the literature.

R. R. Metsaev

Abstract Massive arbitrary spin supermultiplets and massless (scalar and spin one-half) supermultiplets of the N = 2 Poincaré superalgebra in three-dimensional flat space are considered. Both the integer spin and half-integer spin supermultiplets are studied. For such massive and massless supermultiplets, a formulation in terms of light-cone gauge unconstrained superfields defined in a momentum superspace is developed. For the supermultiplets under consideration a superspace first derivative representation for all cubic interaction vertices is obtained. A superspace representation for dynamical generators of the N = 2 Poincaré superalgebra is also found.