In physics and nuclear chemistry, nuclear fusion is the process by which multiple atomic particles join together to form a heavier nucleus. It is accompanied by the release or absorption of energy. Iron and nickel nuclei have the largest binding energies per nucleon of all nuclei and therefore are the most stable. The fusion of two nuclei lighter than iron or nickel generally releases energy while the fusion of nuclei heavier than iron or nickel absorbs energy; vice-versa for the reverse process, nuclear fission. Nuclear Fission is the process of splitting an atom to create an explosion. This process is less powerful than the fusion bombs such as the hydrogen bomb. A uranium bomb is a form of a fission bomb when a neutron is shot through the nucleus of the atom, the atom breaks up into 2 separate elements: Krypton and Barium. These are called the "daughters" of the nucleus.
High-energy nuclear collisions have recently emerged as a promising ‘imaging-by-smashing’ approach to reveal the intrinsic shapes of atomic nuclei. Here, I outline a conceptual framework for this technique, explaining how nuclear shapes are encoded during quark–gluon plasma (QGP) formation and evolution, and how they can be decoded from final-state particle distributions. I highlight the method’s potential to advance our understanding of both nuclear structure and QGP physics.
When two non-relativistic particles interact resonantly in three dimensions, an infinite tower of three-body bound states emerges, exhibiting a discrete scale invariance. This universal phenomenon, known as the Efimov effect, has garnered extensive attention across various fields, including atomic, nuclear, condensed matter, and particle physics. In this letter, we demonstrate that the Efimov effect also manifests in long-range quantum spin chains. The long-range coupling modifies the low-energy dispersion of magnons, enabling the emergence of continuous scale invariance for two-magnon states at resonance. This invariance is subsequently broken to discrete scale invariance upon imposing short-range boundary conditions for the three-magnon problem, leading to the celebrated Efimov bound states. Using effective field theory, we theoretically determine how the ratio of two successive binding energies depends on the interaction range, which agrees with the numerical solution of the bound-state problem. We further discuss generalizations to arbitrary spatial dimensions, where the traditional Efimov effect serves as a special case. Our results reveal universal physics in dilute quantum gases of magnons that can be experimentally tested in trapped-ion systems.
Whether <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>126</mn></mrow></semantics></math></inline-formula> is a proton magic number has been controversial in nuclear physics. The even-even <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mmultiscripts><mi>Ubh</mi><none></none><none></none><mprescripts></mprescripts><mn>126</mn><none></none></mmultiscripts></semantics></math></inline-formula> isotopes are calculated based on the DRHBc calculations with PC-PK1. The evolutions of quadrupole deformation and pairing energies for neutron and proton are analyzed to study the possible nuclear magicity. Spherical shape occurs and neutron pairing energy vanishes at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>N</mi><mo>=</mo><mn>258</mn></mrow></semantics></math></inline-formula> and 350, which are the results of possible neutron magicity, while the proton pairing energy never vanishes in Ubh isotopes, which does not support the proton magicity at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>126</mn></mrow></semantics></math></inline-formula>. In the single-proton spectrum, there is no discernible gap at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>126</mn></mrow></semantics></math></inline-formula>, while significant gaps appear at <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>120</mn></mrow></semantics></math></inline-formula> and 138. Therefore, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>126</mn></mrow></semantics></math></inline-formula> is not supported as a proton magic number, while <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>Z</mi><mo>=</mo><mn>120</mn></mrow></semantics></math></inline-formula> and 138 are suggested as candidates of proton magic numbers.
Nuclear and particle physics. Atomic energy. Radioactivity
Thiago L. M. Guedes, Guillermo A. Mena Marugán, Francesca Vidotto
et al.
In loop quantum gravity (LQG), states of the gravitational field are represented by labeled graphs called spin networks. Their dynamics can be described by a Hamiltonian constraint, which acts on the spin network states, modifying both spins and graphs. Fixed-graph approximations of the dynamics have been extensively studied, but its full graph-changing action so far remains elusive. The latter, alongside the solutions of its constraint, are arguably the missing features in canonical LQG to access phenomenology in all its richness. Here, we discuss a recently developed numerical tool that, for the first time, implements graph-changing dynamics via the Hamiltonian constraint. We explain how it is used to find new solutions to that constraint and to show that some quantum geometric observables behave differently than in the graph-preserving truncation. We also point out that these new numerical methods can find applications in other domains.
Astrophysical observations of the cosmos allow us to probe extreme physics and answer foundational questions on our universe. Modern astronomy is increasingly operating under a holistic approach, probing the same question with multiple diagnostics including how sources vary over time, how they appear across the electromagnetic spectrum, and through their other signatures, including gravitational waves, neutrinos, cosmic rays, and dust on Earth. Astrophysical observations are now reaching the point where approximate physics models are insufficient. Key sources of interest are explosive transients, whose understanding requires multidisciplinary studies at the intersection of astrophysics, gravity, nuclear science, plasma physics, fluid dynamics and turbulence, computation, particle physics, atomic, molecular, and optical science, condensed matter and materials science, radiation transport, and high energy density physics. This white paper provides an overview of the major scientific advances that lay at the intersection of physics and astronomy and are best probed through time-domain and multimessenger astrophysics, an exploration of how multidisciplinary science can be fostered, and introductory descriptions of the relevant scientific disciplines and key astrophysical sources of interest.
Transport models are the main method to obtain physics information from low to relativistic-energy heavy-ion collisions. The Transport Model Evaluation Project (TMEP) has been pursued to test the robustness of transport model predictions in reaching consistent conclusions from the same type of physical model. Calculations under controlled conditions of physical input and set-up were performed with various participating codes. These included both calculations of nuclear matter in a box with periodic boundary conditions, and more realistic calculations of heavy-ion collisions. In this intermediate review, we summarize and discuss the present status of the project. We also provide condensed descriptions of the 26 participating codes, which contributed to some part of the project. These include the major codes in use today. We review the main results of the studies completed so far. They show, that in box calculations the differences between the codes can be well understood and a convergence of the results can be reached. These studies also highlight the systematic differences between the two families of transport codes, known as BUU and QMD type codes. However, when the codes were compared in full heavy-ion collisions using different physical models, as recently for pion production, they still yielded substantially different results. This calls for further comparisons of heavy-ion collisions with controlled models and of box comparisons of important ingredients, like momentum-dependent fields, which are currently underway. We often indicate improved strategies in performing transport simulations and thus provide guidance to code developers. Results of transport simulations of heavy-ion collisions from a given code will have more significance if the code can be validated against benchmark calculations such as the ones summarized in this review.
Abstract Following a recent proposal to describe inelastic eikonal scattering processes in terms of gravitationally dressed elastic eikonal amplitudes, we motivate a collinear double graviton dressing and investigate its properties. This is derived from a generalized Wilson line operator in the worldline formalism by integrating over fluctuations of the eikonal trajectories of external particles in gravitationally interacting theories. The dressing can be expressed as a product of exponential terms — a coherent piece with contributions to all odd orders in the gravitational coupling constant and a term quadratic in graviton modes, with the former providing classical gravitational wave observables. In particular, the coherent dressing involves O κ 3 $$ \mathcal{O}\left({\kappa}^3\right) $$ subleading double graviton corrections to the Weinberg soft factor. We use this dressing to derive expressions for the waveform, radiative momentum spectrum and angular momentum. In a limiting case of the waveform, we derive the nonlinear memory effect resulting from the emission of nearly soft gravitons from a scattering process.
Nuclear and particle physics. Atomic energy. Radioactivity
Abstract We present the analytic total cross section of top quark pair production in electron-positron annihilation at next-to-next-to-leading order (NNLO) in Quantum Chromodynamics (QCD). By utilizing the optical theorem, the NNLO corrections are related to the imaginary parts of three-loop self-energy Feynman diagrams, of which the master integrals are calculated with canonical differential equations. The analytic results for the NNLO corrections are expressed in terms of multiple polylogarithms as well as elliptic functions. We discuss the asymptotic expansions near the threshold and in the high energy limit in detail. Numerical results are provided for the total cross section of top quark pair production at future lepton colliders.
Nuclear and particle physics. Atomic energy. Radioactivity
While experimental physics progressed tremendously since the 1970s, the neutron model has remained essentially unchanged. Motivated by developments in both experiments and theory, which we briefly review in section 1, we propose that the initial neutron decay step is not the emission of an 80 GeV mass boson particle, but the emission of a much lighter lepton particle. On the basis of well-known neutron data, in section 2 we estimate that this new lepton’s mass is 1.5 MeV. Historically, investigations of deuteron photo-dissociation led nuclear scientists to assume that no electron-like particle is associated with neutron decay. We therefore re-examine these experiments in section 3. We demonstrate that deuteron photo-dissociation leads to 2p + + e − products at high photon energies. Our calculations show why a deuteron always breaks up into p + n particles at <3 MeV photon energy. Sections 4 - 7 discuss the properties and interactions of the 1.5 MeV lepton particle. Numerous investigations, including our own experiments, demonstrate the presence of negative elementary charges within atomic nuclei. The emission or absorption of negative nuclear charges involves the emission or absorption of a new lepton particle, which always decays into an electron. Various mass measurement methods converge to the same result: the emitted or absorbed lepton is approximately three times heavier than an ordinary electron. Specifically, we measure its mass to be 1553.5 keV. Our work demonstrates that, despite being a single particle, the neutron comprises a positive and a negative elementary charge. To make sense of the neutron structure, it is necessary to firstly understand the proton’s and the newly discovered 1.5 MeV lepton’s internal structures. In section 9, we apply our results to better understand the neutron’s properties.
The investigation of the magnetic activity of different types of variable stars holds significant implications for our understanding of the physical processes and evolution of stars. This study’s International Variable Star Index (VSX) variable star catalog was cross-matched with Transiting Exoplanet Survey Satellite (TESS) data, resulting in 26,276 labeled targets from 76,187 light curves. A total of 25,327 stellar flare events were detected, including 245 eclipsing binaries, 2324 rotating stars, 111 pulsating stars, and 629 eruptive stars. The results showed that flares from eclipsing binaries, rotating stars, eruptive stars, and pulsating stars have durations such that 90% are less than 2 h, and 91% of their amplitudes are less than 0.3. Flare events mainly occurred in the temperature range of 2000 K to 3000 K. The power-law indices of different types of variable stars were <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.72</mn><mo>±</mo><mn>0.025</mn></mrow></semantics></math></inline-formula> (eclipsing binaries), <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.82</mn><mo>±</mo><mn>0.062</mn></mrow></semantics></math></inline-formula> (rotating stars), <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.80</mn><mo>±</mo><mn>0.0116</mn></mrow></semantics></math></inline-formula> (eruptive stars), and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1.73</mn><mo>±</mo><mn>0.060</mn></mrow></semantics></math></inline-formula> (pulsating stars). Among them, the flare energy of pulsating stars is more concentrated in the high-energy range. In all samples, flare energies were distributed from <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>3.99</mn><mo>×</mo><msup><mn>10</mn><mn>31</mn></msup></mrow></semantics></math></inline-formula> erg to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>6.18</mn><mo>×</mo><msup><mn>10</mn><mn>38</mn></msup></mrow></semantics></math></inline-formula> erg. The LAMOST DR9 low-resolution spectral survey has provided H<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> equivalent widths for 398 variable stars. By utilizing these H<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> equivalent widths, we have determined the stellar activity of the variable stars and confirmed a positive correlation between the flare energy and H<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula> equivalent width.
Abstract We consider generic freeze-in processes for generation of Dark Matter, together with the consequent re-thermalization of the Standard Model fluid. We find that Dark Matter inherits the Standard Model adiabatic inhomogeneities on the cosmological scales probed by current observations, that were super-horizon during freeze-in. Thereby, freeze-in satisfies the bounds on iso-curvature perturbations.
Nuclear and particle physics. Atomic energy. Radioactivity
Most atomic nuclei are deformed with a quadrupole shape described by its overall strength β 2 and triaxiality γ . The deformation can be accessed in high-energy heavy-ion collisions by measuring the collective flow response of the produced quark-gluon plasma to the eccentricity ε 2 and the density gradient d ⊥ in the initial state. Using an analytical estimate and a Glauber model, I show that the variances, ⟨ ε 22 ⟩ or ⟨( δd ⊥ / d ⊥ ) 2 ⟩ , and skewnesses, ⟨ ε 22 δd ⊥ / d ⊥ ⟩ or ⟨( δd ⊥ / d ⊥ ) 3 ⟩ , have a simple analytical form of a ′ + b ′ β 22 and a ′ +( b ′ + c ′ cos ( 3 γ )) β 32 , respectively. From these, I constructed several normalized skewnesses to isolate the γ dependence from that of β 2 , and show that the correlations between a normalized skewness and a variance can constrain simultaneously the β 2 and γ . Assuming a linear relation with elliptic flow v 2 and mean-transverse momentum [ p T ] of final-state particles, v 2 ∝ ε 2 and δ [ p T ]/[ p T ] ∝ δd ⊥ / d ⊥ , similar conclusions are also expected for the variances and skewnesses of v 2 and [ p T ] , i.e. a + bβ 22 for ⟨ v 22 ⟩ and ⟨( δ [ p T ]/[ p T ]) 2 ⟩ and a +( b + c cos ( 3 γ )) β 32 for ⟨ v 22 δ [ p T ]/[ p T ]⟩ or ⟨( δ [ p T ]/[ p T ]) 3 ⟩ . These findings motivate a dedicated system scan of high-energy heavy-ion collisions at RHIC and LHC to measure triaxiality of atomic nuclei: one first determines the coefficients b and c by collisions of isobaric near prolate nuclei, cos ( 3 γ ) ≈ 1, and near oblate nuclei, cos ( 3 γ ) ≈ − 1, with known β 2 values, followed by collisions of other species of interest with similar mass number. The ( β 2 ,γ ) values for this species can be inferred directly from the measured variance and skewness observables from these collisions. The results demonstrate the unique opportunities offered by high-energy collisions as a tool to perform interdisciplinary nuclear physics studies.
Theories that extend the Standard Model of particle physics often introduce new interactions that violate charge-parity (CP) symmetry. Charge-parity-violating effects within an atomic nucleus can be probed by measuring its nuclear magnetic quadrupole moment (MQM). The sensitivity of such a measurement is enhanced when using a heavy polar molecule containing a nucleus with quadrupole deformation. We determine how the energy levels of a molecule are shifted by the magnetic quadrupole moment and how those shifts can be measured. The measurement scheme requires molecules in a superposition of magnetic sub-levels that differ by many units of angular momentum. We develop a generic scheme for preparing these states. Finally, we consider the sensitivity that can be reached, showing that this method can reduce the current uncertainties on several charge-parity-violating parameters.
Background: Precise measurements of atomic transitions affected by electron-nucleus hyperfine interactions offer sensitivity to explore basic properties of the atomic nucleus and study fundamental symmetries, including the search for new physics beyond the Standard Model of particle physics. Such measurements impose higher precision requirements on a theoretical description. Purpose: The nuclear charge density is composed of the proton point distribution folded with the nucleonic charge distributions. The latter induce subtle relativistic corrections due to the coupling of nucleon magnetic moments with the nuclear spin-orbit density. We assess the precision of nuclear charge density calculations by studying the behavior of relativistic corrections. Methods: The calculations are performed using Skyrme energy density functionals and density-dependent pairing force. We used the general expression for the spin-orbit form factor that is valid for spherical and deformed nuclei. Results: We studied the impact of various correction terms on the charge radii, fourth radial moments, diffraction radii, and surface thickness of spherical and deformed nuclei. The spin-orbit corrections to charge radial moments and surface thickness show strong shell fluctuations which impact high-precision predictions of isotopic shifts. Conclusions: To establish reliable constraints on the existence of new forces from isotope shift measurements,precise calculations of nuclear charge densities of deformed nuclei are needed. The proper inclusion of the spin-orbit charge density and other correction terms is essential when aiming at extraction of subtle effects which become particularly visible in isotopic trends.
We describe a project that brings together researchers from atomic physics, nuclear physics and sub-atomic particle physics, to develop a high-precision laboratory-scale experiment able to search for very weakly coupled sterile neutrinos in the mass range extending from 5–10 keV/c 2 to several 100 keV/c 2. Observed neutrino flavor eigenstates are known to be quantum mixtures of at least three sub-eV/c 2 mass eigenstates. There is a strong theoretical belief that there may exist further neutrino mass eigenstates at higher mass levels, and which, if in the keV/c 2 mass range, might form all or part of the galactic dark matter. This has led to many searches for anomalous events in both astrophysical and particle physics experiments, and searches for distortions in beta decay spectra. The present experiment will utilize K-capture events in a population of 131Cs atoms suspended in vacuum by a magneto-optical trap (MOT). Using AMO and nuclear physics techniques, individual events will be fully reconstructed kinematically. Normally each event would be consistent with an emitted neutrino mass close to zero, but the existence of a sterile neutrino of keV/c 2 mass that mixes with the electron type neutrino produced in the decay would result in a separated population of events with non-zero reconstructed missing mass (up to the Q = 352 keV available energy of the reaction). Detailed calculations and simulations of all significant background processes have been made, in particular for scattering in the source itself, radiative K-capture, local radioactivity, cosmic ray muons, and knock-out of electrons by x-rays. A phase 1 of the experiment, under construction with funding from the W M Keck Foundation, has the potential to reach sterile neutrino mixing angles down to sin2 θ ∼ 10−4. With further upgrades this technique could be progressively improved to eventually reach much lower coupling levels ∼10−10, in particular reaching the level needed to be consistent with galactic dark matter below the astrophysical x-ray limits.
Abstract In this paper, we formulate two new classes of black hole solutions in higher curvature quartic quasitopological gravity with nonabelian Yang–Mills theory. At first step, we consider the SO(n) and $$SO(n-1,1)$$ S O ( n - 1 , 1 ) semisimple gauge groups. We obtain the analytic quartic quasitopological Yang–Mills black hole solutions. Real solutions are only accessible for the positive value of the redefined quartic quasitopological gravity coefficient, $$\mu _{4}$$ μ 4 . These solutions have a finite value and an essential singularity at the origin, $$r=0$$ r = 0 for space dimension higher than 8. We also probe the thermodynamic and critical behavior of the quasitopological Yang–Mills black hole. The obtained solutions may be thermally stable only in the canonical ensemble. They may also show a first order phase transition from a small to a large black hole. In the second step, we obtain the pure quasitopological Yang–Mills black hole solutions. For the positive cosmological constant and the space dimensions greater than eight, the pure quasitopological Yang–Mills solutions have the ability to produce both the asymptotically AdS and dS black holes for respectively the negative and positive constant curvatures, $$k=-1$$ k = - 1 and $$k=+1$$ k = + 1 . This is unlike the quasitopological Yang–Mills theory which can lead to just the asymptotically dS solutions for $$\Lambda >0$$ Λ > 0 . The pure quasitopological Yang–Mills black hole is not thermally stable.
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity
Abstract In a model for leptogenesis based on spontaneous breaking of Lorentz and $$\mathcal {CPT}$$ CPT symmetry [1–3], we examine the consistency of using the approximation of plane-wave solutions for a free spin-$$\frac{1}{2}$$ 12 Dirac (or Majorana) fermion field propagating in a Friedmann–Lema$$\hat{\mathrm{i}}$$ i^ tre–Robertson–Walker space time augmented with a cosmic time-dependent (or, equivalently, a temperature-dependent) Kalb–Ramond (KR) background. For the range of parameters relevant for leptogenesis, our analysis fully justifies the use of plane-wave solutions in our study of leptogenesis with Boltzmann equations; any corrections induced by space-time-curvature are negligible. We also elaborate further on how the lepton asymmetry is communicated to the Baryon sector. We demonstrate that the KR background (KRB) does not contribute to the anomaly equations that determine the baryon asymmetry (a) through an explicit evaluation of a triangle Feynman graph and (b) indirectly, on topological grounds, by identifying the KRB as torsion (in the effective string-inspired low energy gravitational field theory).
Astrophysics, Nuclear and particle physics. Atomic energy. Radioactivity