Search

Faddeev calculations for the triton are performed with three two-body potentials (RSC, URG, and Paris) taking eighteen channels, $J<~2$, for an interacting pair. Using these wave functions, we calculate the first-order perturbation energy for the Tucson-Melbourne three-body interaction. For the usual dipole pionic form factor with the cutoff parameter of $\Lambda =800\mathrm{}$ MeV, we get 0.89 MeV (RSC), 0.50 MeV (URG), and 0.67 MeV (Paris). Thus, the calculated triton binding energies amount to 8.13 MeV (RSC), 8.00 MeV (URG), and 8.23 MeV (Paris). These values are very close to the experimental value of 8.482 MeV.

The $\varphi \text{−}\mathrm{\Lambda }(1520)$ interference effect in the $\gamma p\to K^{+}{K}^{-}p$ reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between $\varphi$ and $\mathrm{\Lambda }(1520)$ production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when $K^{+}{K}^{-}$ pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the $\sqrt{s}=2.1\mathrm{GeV}$ bump structure in forward differential cross sections for $\varphi$ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

The differential cross sections and decay angular distributions for coherent $\varphi$-meson photoproduction from helium-4 are measured for the first time at forward angles with linearly polarized photons in the energy range $E_{\gamma }=1.685–2.385\text{GeV}$. Thanks to the target with spin-parity $J^P=0^{+}$, unnatural-parity exchanges are absent, and thus natural-parity exchanges can be investigated clearly. The decay asymmetry with respect to photon polarization is shown to be very close to the maximal value. This ensures the strong dominance ($>94$%) of natural-parity exchanges in this reaction. To evaluate the contribution from natural-parity exchanges to the forward cross section ($\theta =0^{\circ }$) for the $\gamma p\to \varphi p$ reaction near threshold, the energy dependence of the forward cross section ($\theta =0^{\circ }$) for the $\gamma {}^4\mathrm{He}\to \varphi {}^4\mathrm{He}$ reaction is analyzed. The comparison to $\gamma p\to \varphi p$ data suggests that enhancement of the forward cross section arising from natural-parity exchanges and/or destructive interference between natural-parity and unnatural-parity exchanges is needed in the $\gamma p\to \varphi p$ reaction near threshold.

Differential cross sections and photon-beam asymmetries for the $\overrightarrow{\gamma }p\to {\pi }^{-}{\mathrm{\Delta }}^{++}(1232)$ reaction have been measured for $0.7<\cos {\theta }_{\pi }^{\mathrm{c}.\mathrm{m}.}<1$ and $E_{\gamma }=1.5–2.95\mathrm{GeV}$ at SPring-8/LEPS. The first-ever high statistics cross-section data are obtained in this kinematical region, and the asymmetry data for $1.5<E_{\gamma }(\mathrm{GeV})<2.8$ are obtained for the first time. This reaction has a unique feature for studying the production mechanisms of a pure $u\overline{u}$ quark pair in the final state from the proton. Although there is no distinct peak structure in the cross sections, a non-negligible excess over the theoretical predictions is observed at $E_{\gamma }=1.5–1.8\mathrm{GeV}$. The asymmetries are found to be negative in most of the present kinematical regions, suggesting the dominance of $\pi$ exchange in the $t$ channel. The negative asymmetries at forward meson production angles are different from the asymmetries previously measured for the photoproduction reactions producing a $d\overline{d}$ or an $s\overline{s}$ quark pair in the final state. Advanced theoretical models introducing nucleon resonances and additional unnatural-parity exchanges are needed to reproduce the present data.

The first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan (DY) process is reported. We use the CERN SPS $190\mathrm{GeV}/c$ ${\pi }^{-}$ beam and a transversely polarized ammonia target. Three azimuthal asymmetries giving access to different transverse-momentum-dependent (TMD) parton distribution functions (PDFs) are extracted using dimuon events with invariant mass between $4.3\mathrm{GeV}/c^2$ and $8.5\mathrm{GeV}/c^2$. Within the experimental uncertainties, the observed sign of the Sivers asymmetry is found to be consistent with the fundamental prediction of quantum chromodynamics (QCD) that the Sivers TMD PDFs extracted from DY have a sign opposite to the one extracted from semi-inclusive deep-inelastic scattering (SIDIS) data. We present two other asymmetries originating from the pion Boer-Mulders TMD PDFs convoluted with either the nucleon transversity or pretzelosity TMD PDFs. A recent COMPASS SIDIS measurement was obtained at a hard scale comparable to that of these DY results. This opens the way for possible tests of fundamental QCD universality predictions.

Through numerical simulations, it is predicted that the gravitational waves (GWs) reflect the characteristics of the core-collapse supernova (CCSN) explosion mechanism. There are multiple GW excitation processes that occur inside a star before its explosion, and it is suggested that the GWs originating from the CCSN have a mode for each excitation process in terms of time-frequency representation. Therefore, we propose an application of the Hilbert-Huang transform (HHT), which is a high-resolution time-frequency analysis method, to analyze these GW modes for theoretically probing and increasing our understanding of the explosion mechanism. The HHT defines frequency as a function of time, and is not bound by the trade-off between time and frequency resolutions. In this study, we analyze a gravitational waveform obtained from a three-dimensional general-relativistic CCSN model that showed a vigorous activity of the standing-accretion-shock-instability (SASI). We succeed in extracting the SASI induced GWs with high resolution on a time-frequency representation using the HHT and we examine their instantaneous frequencies.

The angular distribution of gravitational-wave power from persistent sources may exhibit anisotropies arising from the large-scale structure of the Universe. This motivates directional searches for astrophysical and cosmological gravitational-wave backgrounds, as well as continuous-wave emitters. We present results of such a search using data from the first observing run through the first portion of the fourth observing run of the LIGO-Virgo-KAGRA Collaborations. We apply gravitational-wave radiometer techniques to generate skymaps and search for both narrowband and broadband persistent gravitational-wave sources. Additionally, we use spherical harmonic decomposition to probe spatially extended sources. No evidence of persistent gravitational-wave signals is found, and we set the most stringent constraints to date on such emissions. For narrowband point sources, our sensitivity estimate to effective strain amplitude lies in the range $(0.03–8.4)\times {10}^{-24}$ across all-sky and frequency range ($20-160$) Hz. For targeted sources—Scorpius X-1, SN 1987A, the Galactic Center, Terzan 5, and NGC 6397—we constrain the strain amplitude with best limits ranging from $\sim 1.1\times {10}^{-25}$ to $6.5\times {10}^{-24}$. For persistent broadband sources, we constrain the gravitational-wave flux $F_{\alpha ,\widehat{n}}^{95\%,\mathrm{UL}}(25\mathrm{Hz})<(0.008–5.5)\times {10}^{-8}\mathrm{erg}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{Hz}}^{-1}$, depending on the sky direction $\widehat{n}$ and spectral index $\alpha =0,2/3$, 3. Finally, for extended sources, we place upper limits on the angular power spectrum $C_{\ell }^{1/2}<(0.63–17)\times {10}^{-10}{\mathrm{sr}}^{-1}$.

We report on the population properties of compact binary mergers inferred from gravitational-wave observations of these systems during the first three LIGO-Virgo observing runs. The Gravitational-Wave Transient Catalog 3 (GWTC-3) contains signals consistent with three classes of binary mergers: binary black hole, binary neutron star, and neutron star–black hole mergers. We infer the binary neutron star merger rate to be between 10 and $1700{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ and the neutron star–black hole merger rate to be between 7.8 and $140{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$, assuming a constant rate density in the comoving frame and taking the union of 90% credible intervals for methods used in this work. We infer the binary black hole merger rate, allowing for evolution with redshift, to be between 17.9 and $44{\mathrm{Gpc}}^{-3}{\mathrm{yr}}^{-1}$ at a fiducial redshift ($z=0.2$). The rate of binary black hole mergers is observed to increase with redshift at a rate proportional to $(1+z{)}^{\kappa }$ with $\kappa =2.9_{-1.8}^{+1.7}$ for $z\lesssim 1$. Using both binary neutron star and neutron star–black hole binaries, we obtain a broad, relatively flat neutron star mass distribution extending from ${1.2}_{-0.2}^{+0.1}$ to ${2.0}_{-0.3}^{+0.3}{M}_{\odot }$. We confidently determine that the merger rate as a function of mass sharply declines after the expected maximum neutron star mass, but cannot yet confirm or rule out the existence of a lower mass gap between neutron stars and black holes. We also find the binary black hole mass distribution has localized over- and underdensities relative to a power-law distribution, with peaks emerging at chirp masses of ${8.3}_{-0.5}^{+0.3}$ and ${27.9}_{-1.8}^{+1.9}{M}_{\odot }$. While we continue to find that the mass distribution of a binary’s more massive component strongly decreases as a function of primary mass, we observe no evidence of a strongly suppressed merger rate above approximately $60M_{\odot }$, which would indicate the presence of a upper mass gap. Observed black hole spins are small, with half of spin magnitudes below ${\chi }_i\approx 0.25$. While the majority of spins are preferentially aligned with the orbital angular momentum, we infer evidence of antialigned spins among the binary population. We observe an increase in spin magnitude for systems with more unequal-mass ratio. We also observe evidence of misalignment of spins relative to the orbital angular momentum.

The $s$-wave asymptotic normalization constants $C_0$(${}_{}{}^3{}_{}{}^{}\mathrm{H}$) and $C_0$(${}_{}{}^3{}_{}{}^{}\mathrm{H}$) are calculated for the Reid soft-core potential. The Coulomb effect is taken into account for ${}_{}{}^3{}_{}{}^{}\mathrm{He}$. $C_0\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=1.765\mathrm{}$ and $C_0\left({}_{}{}^3{}_{}{}^{}\mathrm{H}\right)=1.706\mathrm{}$ have been obtained. In ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ (${}_{}{}^3{}_{}{}^{}\mathrm{H}$), about 60% of the contribution is due to the transition from the $\mathrm{pp}$ ($\mathrm{nn}$) ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state of a pair in one set of coordinates to the $\mathrm{np}{}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ state of another set.

The ever-increasing number of detections of gravitational waves from compact binaries by the Advanced LIGO and Advanced Virgo detectors allows us to perform ever-more sensitive tests of general relativity (GR) in the dynamical and strong-field regime of gravity. We perform a suite of tests of GR using the compact binary signals observed during the second half of the third observing run of those detectors. We restrict our analysis to the 15 confident signals that have false alarm rates $\le {10}^{-3}{\mathrm{yr}}^{-1}$. In addition to signals consistent with binary black hole mergers, the new events include GW200115_042309, a signal consistent with a neutron star–black hole merger. We find the residual power, after subtracting the best fit waveform from the data for each event, to be consistent with the detector noise. Additionally, we find all the post-Newtonian deformation coefficients to be consistent with the predictions from GR, with an improvement by a factor of $\sim 2$ in the $-1\mathrm{PN}$ parameter. We also find that the spin-induced quadrupole moments of the binary black hole constituents are consistent with those of Kerr black holes in GR. We find no evidence for dispersion of gravitational waves, non-GR modes of polarization, or post-merger echoes in the events that were analyzed. We update the bound on the mass of the graviton, at 90% credibility, to $m_g\le 2.42\times {10}^{-23}\mathrm{eV}/c^2$. The final mass and final spin as inferred from the premerger and postmerger parts of the waveform are consistent with each other. The studies of the properties of the remnant black holes, including deviations of the quasinormal mode frequencies and damping times, show consistency with the predictions of GR. In addition to considering signals individually, we also combine results from the catalog of gravitational waves signals to calculate more precise population constraints. We find no evidence in support of physics beyond general relativity.

We present a search for gravitational waves from inspiraling, planetary-mass ultracompact binaries using data from the first part of the fourth observing run of LIGO, Virgo, and KAGRA. Finding no evidence of such systems, we determine the maximum distance reach for such objects and their merger rate densities. Then, we identify classes of primordial black hole mass distributions for which these rate limits can be translated into relevant constraints on the mass distribution of primordial black holes, assuming that they are all composed of dark matter, in the mass range $[{10}^{-6},{10}^{-3}]M_{\odot }$. Our constraints for the class of primordial black hole mass distribution functions $f(m)$ we consider reach down to $f(m)\sim 0.1$. They are consistent with existing microlensing results in the planetary-mass range, provide a complementary probe to subsolar mass objects, and are publicly available [1].

A distorted-wave formulation with exchange is given for the electron-impact excitation of atoms from ${\left(n_0{l}_0\right)}^N$ to ${\left(n_0{l}_0\right)}^{N-1\mathrm{}}\mathrm{nl}$ configurations using the $\mathrm{LS}$-coupling scheme. Phenomenologically determined independent-particle models and distorted-wave potentials are utilized to compute angular distributions and integrated cross sections for $2p\to 3s,3p$, and $4p$ excitations of atomic oxygen over wide ranges of energy and momentum transfer. The results are compared with the Born-approximation limit as well as the experimental integrated cross section of Stone and Zipf.

By reexamining the energy-momentum balance of a charged particle and radiation fields, an extra condition as well as the Lorentz-Dirac equation are derived. The extra condition enables us to eliminate the runaway solutions. It also implies a new boundary condition to be satisfied when a charged particle fuses with another particle of opposite charge.

A method for expanding a nonlocal, nonsymmetric potential as the sum of separable terms is presented. The method of calculating the bound state and the scattering amplitude is described. A numerical example of the nonlocal potential related to $n-d$ elastic scattering is given.

The perturbational approach to the Faddeev equation proposed by us is applied to the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ bound state. The perturbation iteration is found to converge beautifully, leaving no question about its usefulness. Using the Reid soft-core potential, we obtain the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ binding energy at 6.62 MeV, $P\left(S\right)=90.28\%$, $P\left(S^{\prime }\right)=1.70\%$, and $P\left(D\right)=8.02\%$, for the three-body state consisting of the two-body pair in the ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and the ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}={}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ state with the third particle in the $s$-state relative to the center-of-mass of the pair. The contribution from the third particle in the $d$-state adds to the binding energy only a small fraction (∼0.05 MeV). The one-body charge form factor of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has a dip at $q^2\sim 16$ ${\mathrm{fm}}^{-2\mathrm{}}$, and the height of the second peak is about an order of magnitude too low compared to the data. Each Faddeev component of the triton wave function as a function of the relative distance of a pair has a node near the core radius in its ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ and ${}_{}{}^3{}_{}{}^{}S_1^{}{}_{}{}^{}$ components, but no node is found in the ${}_{}{}^3{}_{}{}^{}D_1^{}{}_{}{}^{}$ component. The wave function as a function of the spectator coordinate extends over quite large distances without a node in any component. The nodes are attributed to the strong soft-core and the particle exchange effects.

NUCLEAR STRUCTURE Triton bound state. Exact solution of the Faddeev equation by a perturbative approach. Binding energy; 6.62 MeV. Node of the wave function near the core radius.

We examine a number of features and questions related to realistic one-boson-exchange-potential models for the $N-N$ interaction, mainly from a phenomenological viewpoint. They include (i) the validity of the one-pion-exchange region concept and the classical impact-parameter formula, (ii) the effect of a discrete versus continuous mass for the $I=0\mathrm{}$, $J=0\mathrm{}$ meson field used to simulate the $2\pi$ continuum, (iii) the effect of an unconstrained versus constrained vector-meson field, (iv) the influence of "double regularization" upon phase shifts, and (v) the extension of effective-range theory to velocity-dependent interactions. The objectives are to obtain a physical understanding of the $N-N$ interaction and to provide heuristic guides to the further development of a quantitative theory of the fundamental nuclear force.

Differential cross sections and photon-beam asymmetries for the $\vec{\gamma }p\to {\pi }^{+}n$ reaction have been measured for $0.6<cos{\theta }_{\pi }<1$ and $E_{\gamma }=1.5\text{–}2.95\mathrm{GeV}$ at SPring-8/LEPS. The cross sections monotonically decrease as the photon beam energy increases for $0.6<cos{\theta }_{\pi }<0.9$. However, the energy dependence of the cross sections for $0.9<cos{\theta }_{\pi }<1$ and $E_{\gamma }=1.5\text{–}2.2\mathrm{GeV}$ ($W=1.9\text{–}2.2\mathrm{GeV}$) is different, which may be due to a nucleon or $\mathrm{\Delta }$ resonance. The present cross sections agree well with the previous cross sections measured by other groups and show forward peaking, suggesting significant $t$-channel contributions in this kinematical region. The asymmetries are found to be positive, which can be explained by $\rho$ exchange in the $t$ channel. Large positive asymmetries in the small-$\left|t\right|$ region, where the $\rho$-exchange contribution becomes small, could be explained by introducing $\pi$-exchange interference with the $s$ channel.

One-boson-exchange interactions are derived for pseudoscalar ($P$), vector ($V$), scalar ($S$), axial vector ($A$), and antisymmetric tensor ($T$) mesons. The Schrödinger-Pauli-Breit limit is obtained for a combination of such Diracian OBE interactions. We calculate the phase shifts for purely relativistic $\pi -5\mathrm{}\omega$ model and find it possible to fit the $S$-wave phase shifts by adjusting one coupling constant and one regularization parameter. Then by breaking this model slightly we develop several accurate representations of the $N-N$ interaction for all waves with a moderate number of adjustable parameters, several of which are fixed by external considerations. We present a physical interpretation of the results particularly the velocity-dependent interactions. Finally we discuss the results in relationship to other $\mathrm{PVS}$ models.

A distorted-wave (DW) formulation with exchange is given for the electron impact excitation of the rare gases from ${\left(n_{0}p\right)}^6$ to ${\left(n_{0}p\right)}^5\mathrm{nl}$ configurations. A practical form employing the pure $\mathrm{LS}$-coupling scheme is used in conjunction with the phenomenologically determined independent-particle model (IPM) and the DW potentials of real central forms to compute cross sections averaged over fine structures. Numerical work is carried out for $\mathrm{Ne} 2p\to 3s$ and $\mathrm{Ar} 3p\to 4s$ electron impact excitations. The distorted generalized oscillator strengths (DGOS), which converge to the generalized oscillator strengths (GOS) in the limit of the Born approximation, as well as integrated cross sections, are obtained over a wide range of energies, so that the systematic variation of the cross sections in relation to the results of the Born approximation can be studied. The results of the angular distributions at lower energies are in reasonable agreement with the data by Nicoll and Mohr.

A formulation for the elastic scattering of electrons from molecules is presented based on an independent-particle model (IPM) and a fixed-nuclei approximation. Numerical computations are carried out for $e^{-}+{\mathrm{N}}_2$ scattering. A phenomenological, energy-independent IPM potential is found to be capable of qualitatively reproducing the total and differential cross sections over a wide range of energy from 10 to 500 eV.