The CMS collaboration, V. Chekhovsky, A. Hayrapetyan
et al.
Abstract A search for nonresonant new physics phenomena in high-mass dilepton events produced in association with b-tagged jets is performed using proton-proton collision data collected in 2016–2018 by the CMS experiment at the CERN LHC, at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb −1. The analysis considers two effective field theory models with dimension-six operators; involving four-fermion contact interactions between two leptons (ℓℓ, electrons or muons) and b or s quarks (bbℓℓ and bsℓℓ). Two lepton flavor combinations (ee and μμ) are required and events are classified as having 0, 1, or ≥2 b-tagged jets in the final state. No significant excess is observed over the standard model backgrounds. Upper limits are set on the production cross section of the new physics signals. These translate into lower limits on the energy scale Λ of 6.9 to 9.0 TeV in the bbℓℓ model, depending on model parameters, and on the ratio of energy scale and effective coupling, Λ/g *, of 2.0 to 2.6 TeV in the bsℓℓ model. Lepton flavor universality is also tested by comparing the dielectron (ee) and dimuon (μμ) mass spectra for different b-tagged jet multiplicities. No significant deviation from the standard model expectation of unity is observed.
Nuclear and particle physics. Atomic energy. Radioactivity
Abstract Determining the bubble wall velocity in first-order phase transitions is a challenging task, requiring the solution of (coupled) equations of motion for the scalar field and Boltzmann equations for the particles in the plasma. The collision terms appearing in the Boltzmann equation present a prominent source of uncertainty as they are often known only at leading log accuracy. In this paper, we derive upper and lower bounds on the wall velocity, corresponding to the local thermal equilibrium and ballistic limits. These bounds are completely independent of the collision terms. For the ballistic approximation, we argue that the inhomogeneous plasma temperature and velocity distributions across the bubble wall should be taken into account. This way, the hydrodynamic obstruction previously observed in local thermal equilibrium is also present for the ballistic approximation. This is essential for the ballistic approximation to provide a lower bound on the wall velocity. We use a model-independent approach to study the behaviour of the limiting wall velocities as a function of a few generic parameters, and we test our developments in the singlet extended Standard Model.
Nuclear and particle physics. Atomic energy. Radioactivity
The Belle II collaboration, I. Adachi, L. Aggarwal
et al.
Abstract We present measurements of B → K *(892)γ decays using 365 fb −1 of data collected from 2019 to 2022 by the Belle II experiment at the SuperKEKB asymmetric-energy e + e − collider. The data sample contains (387 ± 6) × 106 Υ(4S) events. We measure branching fractions ( $$\mathcal{B}$$ ) and CP asymmetries ( $${\mathcal{A}}_{CP}$$ ) for both B 0 → K *0 γ and B + → K *+ γ decays. The difference in CP asymmetries ( $$\Delta {\mathcal{A}}_{CP}$$ ) and the isospin asymmetry (∆0+) between these neutral and charged channels are also measured. We obtain the following branching fractions and CP asymmetries: $$\mathcal{B}\left({B}^{0}\to {K}^{*0}\gamma \right)=\left(4.14\pm 0.10\pm 0.11\right)\times {10}^{-5}$$ , $$\mathcal{B}\left({B}^{+}\to {K}^{*+}\gamma \right)=\left(4.04\pm {0.13}_{-0.15}^{+0.13}\right)\times {10}^{-5}$$ , $${\mathcal{A}}_{CP}\left({B}^{0}\to {K}^{*0}\gamma \right)=\left(-3.3\pm 2.3\pm 0.4\right)\%$$ , and $${\Delta}{\mathcal{A}}_{CP}\left({B}^{+}\to {K}^{*+}\gamma \right)=\left(-0.7\pm 2.9\pm 0.5\right)\%$$ . The measured difference in CP asymmetries is $${\Delta}{\mathcal{A}}_{CP}=\left(+{2}.{6}\pm {3}.{8}\pm 0.{6}\right)\%$$ , and the measured isospin asymmetry is ∆0+ = (+4.8 ± 2.0 ± 1.8)%. The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.
Nuclear and particle physics. Atomic energy. Radioactivity
Abstract The Dirac equation with mass and axial chemical potential is solved analytically, obtaining the mode spinors and the corresponding projection operators, giving the spectral representations of the principal conserved operators. In this framework, the odd partner of the Pryce spin operator is defined for the first time, showing how these operators may be combined for defining the particle and antiparticle spin and polarization operators of Dirac’s theory of massive fermions, either in the free case or in the presence of the axial chemical potential. The quantization procedure is applied in both these cases, obtaining two distinct operator algebras in which the particle and antiparticle spin and polarization operators take canonical forms. In this approach, statistical operators with independent particle and antiparticle vortical chemical potentials may be constructed.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We extend the construction of Alcubierre–Natário class of warp drives to an infinite class of spacetimes with similar properties. This is achieved by utilising the Martel–Poisson charts which closely resembles the Weak Painlevé–Gullstrand form for various background metrics (Mink, AdS, dS). The highlight of this construction is the non-flat intrinsic metric which in three dimensional spacetimes introduce conical singularities at the origin and in higher dimensions generates non-zero Ricci scalar for the spatial hypersurfaces away from the origin. We analyse the expansion/contraction of space and the (NEC) violations associated with these warp drives and find interesting scalings due to the global imprints of the conical defects. Other properties like tilting of light cones, event horizons and several generalisations are also discussed.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Utilizing the databases from the European Pulsar Network (EPN), the Australia Telescope National Facility (ATNF), and published literature data, a geometric method was used to investigate the multifrequency emission altitude of 104 pulsars. We found that the evolution of emission altitudes with frequency for the majority of pulsars can be fitted using a power-law function with a normalization constant. In this work, it is found that the frequency evolution of pulsar emission altitude can be divided into three groups according to their different frequency dependencies of emission altitude (emission altitude decreases with frequency (Group A, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo>≤</mo><mo>−</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>), keeps relatively constant with frequency (Group B, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>−</mo><mn>0.1</mn><mo><</mo><mi>η</mi><mo>≤</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>), and increases with frequency (Group C, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo>≥</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>)), where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>η</mi></semantics></math></inline-formula> is the emission altitude variation rate. We also computed the emission altitudes across multiple frequency bands for these pulsars, thereby estimating the approximate range of the pulsar emission regions. We found that most pulsar emissions occur at altitudes of tens to hundreds of kilometers above the polar cap, with differences in emission altitude between the three groups becoming more clear at lower frequencies.
Nonevaporable getter (NEG) coating is widely required in the new generation of light sources and circular e^{+}e^{-} colliders for small vacuum pipes to improve the vacuum level, which, however, also enhances the high-frequency resistive-wall impedance and often generates a resonator-like peak in the terahertz frequency region. In this paper, we will use the parameters of the planned Hefei Advanced Light Facility storage ring to study the impact of NEG-coating resistive-wall impedance on the longitudinal microwave instability via particle tracking simulation. Using different NEG-coating parameters (resistivity and thickness) as examples, we find that the impedance with a narrow and strong peak in the terahertz frequency region can cause terahertz scale microbunching instability, which has a low instability threshold current and contributes to a large energy spread widening above the threshold. In order to obtain a convergent simulation of the beam dynamics, one must properly resolve such a peak. The coating with a lower resistivity has a less sharp peak in its impedance spectrum, and there is a regime that it is helpful to suppress the terahertz scale microbunching instability and in return contributes to a higher instability threshold current.
Nuclear and particle physics. Atomic energy. Radioactivity
L. Cimino, Clara Tourbez, Cyrille Chevalier
et al.
Many-body forces, and specially three-body forces, are sometimes a relevant ingredient in various fields, such as atomic, nuclear or hadronic physics. As their precise structure is generally difficult to uncover or to implement, phenomenological effective forces are often used in practice. A form commonly used for a many-body variable is the square-root of the sum of two-body variables. Even in this case, the problem can be very difficult to treat numerically. But this kind of many-body forces can be handled at the same level of difficulty than two-body forces by the envelope theory. The envelope theory is a very efficient technique to compute approximate, but reliable, solutions of many-body systems, specially for identical particles. The quality of this technique is tested here for various three-body forces with non-relativistic systems composed of three identical particles. The energies, the eigenfunctions, and some observables are compared with the corresponding accurate results computed with a numerical variational method.
A. E. Cárcamo Hernández, K. N. Vishnudath, José W. F. Valle
Abstract We propose a minimal model where a dark sector seeds neutrino mass generation radiatively within the linear seesaw mechanism. Neutrino masses are calculable, since tree-level contributions are forbidden by symmetry. They arise from spontaneous lepton number violation by a small Higgs triplet vacuum expectation value. Lepton flavour violating processes e.g. μ → eγ can be sizeable, despite the tiny neutrino masses. We comment also on dark-matter and collider implications.
Nuclear and particle physics. Atomic energy. Radioactivity
Nanotechnology is helping to considerably improve, even revolutionize, many technology and industry sectors: information technology, energy, environmental science, medicine, homeland security, food safety, and transportation, among many others. Today's nanotechnology harnesses current progress in chemistry, physics, materials science, and biotechnology to create novel materials that have unique properties because their structures are determined on the nanometer scale. This paper study the various applications of nanotechnology in recent decades. “Nanotechnology”. It gives a brief description about Nanotechnology and its application in various field’s viz. medicine, computing, Robotics, food technology and Solar cells etc. It also deals with the future perspectives of Nanotechnology. Nanotechnology is the study of minuscule particles. The nanotechnology imagines a world wherein new items are planned at the nuclear and atomic level; give sensible, savvy techniques for lashing sustainable power sources and keeping the climate clean.
A cosmic muon imaging system is essentially a particle tracking detector as known from experimental High Energy Physics. The Multiwire Proportional Chamber (MWPC) once revolutionized this field of science, and as such it is a viable choice as the core element of an imaging system. Long term construction and operation experience was gathered from a Japanese–Hungarian collaboration that gave rise to the MWPC-based Muon Observatory System (MMOS), and is being used in Japan at the Sakurajima volcano. The present paper attempts to draw conclusions on the thermal and mechanical limits of the system, based on controlled measurements and detailed simulations. High temperature behavior and effects of thermal cycling and conditioning are presented, which appear to consistently allow one to propose quality control criteria. Regarding mechanical stability, the relation between gluing quality (tensile strength) and expected stress from vibration (during transportation) determines the safety factor to avoid damages. Both of these are presented and quantified in the paper using a conservative and austere approach, with mechanical simulations validated with experimental modal testing data. One can conclude that mechanical stress during industrial standard air freight shipping conditions is nearly a factor of three below the calculated maximum stress.
Physics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We study the consistency of the cubic couplings of a (partially-)massless spinning field to two scalars in (d + 1)-dimensional de Sitter space. Gauge invariance of observables with external (partially)-massless spinning fields translates into Ward-Takahashi identities on the boundary. Using the Mellin-Barnes representation for boundary correlators in momentum space, we give a systematic study of Ward-Takahashi identities for tree-level 3- and 4-point processes involving a single external (partially-)massless field of arbitrary integer spin-J. 3-point Ward-Takahashi identities constrain the mass of the scalar fields to which a (partially-)massless spin-J field can couple. 4-point Ward-Takahashi identities then constrain the corresponding cubic couplings. For massless spinning fields, we show that Weinberg’s flat space results carry over to (d+1)-dimensional de Sitter space: for spins J = 1, 2 gauge-invariance implies charge-conservation and the equivalence principle while, assuming locality, higher-spins J > 2 cannot couple consistently to scalar matter. This result also applies to anti-de Sitter space. For partially-massless fields, restricting for simplicity to those of depth-2, we show that there is no consistent coupling to scalar matter in local theories. Along the way we also give a detailed account of how contact amplitudes with and without derivatives are represented in the Mellin-Barnes representation. Various new explicit expressions for 3- and 4-point functions involving (partially-)massless fields and conformally coupled scalars in dS4 are given.
Nuclear and particle physics. Atomic energy. Radioactivity
Abstract Quintessence fields, introduced to explain the speed-up of the Universe, might affect the geometry of spacetime surrounding black holes, as compared to the standard Schwarzschild and Kerr geometries. In this framework, we study the neutrino pairs annihilation into electron-positron pairs ( $$\nu {\bar{\nu }}\rightarrow e^-e^+$$ ν ν ¯ → e - e + ) near the surface of a neutron star, focusing, in particular, on the Schwarzschild-like geometry in presence of quintessence fields. The effect of the latter is to increase the photon-sphere radius ( $$R_{ph}$$ R ph ), increasing in such a way the maximum energy deposition rate near to $$R_{ph}$$ R ph . The rate turns out to be several orders of magnitude greater than the rate computed in the framework of General Relativity. These results might provide a rising in the GRBs energy emitted from a close binary neutron star system and might be used to constraints the parameters of the quintessence model. Finally we theoretically study the effects of rotation on the neutrino energy deposition.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Carla R. Almeida, Olesya Galkina, Julio César Fabris
In this paper, we discuss classical and quantum aspects of cosmological models in the Brans–Dicke theory. First, we review cosmological bounce solutions in the Brans–Dicke theory that obeys energy conditions (without ghost) for a universe filled with radiative fluid. Then, we quantize this classical model in a canonical way, establishing the corresponding Wheeler–DeWitt equation in the minisuperspace, and analyze the quantum solutions. When the energy conditions are violated, corresponding to the case <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo><</mo><mo>−</mo><mfrac><mn>3</mn><mn>2</mn></mfrac></mrow></semantics></math></inline-formula>, the energy is bounded from below and singularity-free solutions are found. However, in the case <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>ω</mi><mo>></mo><mo>−</mo><mfrac><mn>3</mn><mn>2</mn></mfrac></mrow></semantics></math></inline-formula>, we cannot compute the evolution of the scale factor by evaluating the expectation values because the wave function is not finite (energy spectrum is not bounded from below). However, we can analyze this case using Bohmian mechanics and the de Broglie–Bohm interpretation of quantum mechanics. Using this approach, the classical and quantum results can be compared for any value of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ω</mi></semantics></math></inline-formula>.