P-wave Resonance Research Articles

A0(1710)−f0(1710) mixing effect in the Ds+→KS0KS0π+ decay

With the measurements of the decay Ds+→KS0KS0π+ by the BESIII collaboration, we investigate this three-body weak decay via the chiral unitary approach for the final state interaction, where the resonances S(980) and S(1710) are dynamically reproduced with the interaction of eleven coupled channels, and the W-external and W-internal emission mechanisms are considered at the quark level. Besides, we also take into account the contribution from the P-wave resonance K*(892)+ and make a combined fit of the KS0KS0 and KS0π+ invariant mass spectra measured by the BESIII collaboration. The fitted results show that the enhancement around 1.7 GeV in KS0KS0 mass spectrum is overlapped with two visible peaks, indicating the mixing signal originated from the resonances a0(1710) and f0(1710) due to their different poles (masses). Thus, the decay Ds+→KS0KS0π+ is helpful to reveal their molecular nature with the mixing signal, which can be more precisely measured in the future. Published by the American Physical Society 2024

P-wave resonances in the exponential cosine screened Coulomb potential* *This work was supported by the National Natural Science Foundation of China (Grant No. 12174147) and the Chinese Scholarship Council (Grant Nos. 202108210152 and 202006175016).

We perform benchmark calculations of the p-wave resonances in the exponentially cosine screened Coulomb potential using the uniform complex-scaling generalized pseudo-spectral method. The present results show significant improvement in calculation accuracy compared to previous predictions and correct the misidentification of resonance electron configuration in previous works. It is found that the resonance states approximately follow an n 2-scaling law which is similar to the bound counterparts. The birth of a new resonance would distort the trajectory of an adjacent higher-lying resonance.

Controlling the interactions in a cold atom quantum impurity system

We implement an experimental architecture in which a single atom of K is trapped in an optical tweezer, and is immersed in a bath of Rb atoms at ultralow temperatures. In this regime, the motion of the single trapped atom is confined to the lowest quantum vibrational levels. This realizes an elementary and fully controllable quantum impurity system. For the trapping of the K atom, we use a species-selective dipole potential, that allows us to independently manipulate the quantum impurity and the bath. We concentrate on the characterization and control of the interactions between the two subsystems. To this end, we perform Feshbach spectroscopy, detecting several inter-dimensional confinement-induced Feshbach resonances for the KRb interspecies scattering length, that parametrizes the strength of the interactions. We compare our data to a theory for inter-dimensional scattering, finding good agreement. Notably, we also detect a series of p-wave resonances stemming from the underlying free-space s-wave interactions. We further determine how the resonances behave as the temperature of the bath and the dimensionality of the interactions change. Additionally, we are able to screen the quantum impurity from the bath by finely tuning the wavelength of the light that produces the optical tweezer, providing us with a new effective tool to control and minimize the interactions. Our results open a range of new possibilities in quantum simulations of quantum impurity models, quantum information, and quantum thermodynamics, where the interactions between a quantized system and the bath is a powerful yet largely underutilized resource.

Status of experimental knowledge on the unbound nucleus 13Be

The structure of the unbound nucleus 13Be is important for understanding the Borromean, two-neutron halo nucleus 14Be. The experimental studies conducted over the last four decades are reviewed in the context of the beryllium chain of isotopes and some significant theoretical studies. The focus of this paper is the comparison of new data from a 12Be(d,p) reaction in inverse kinematics, which was analyzed using Geant4 simulations and a Bayesian fitting procedure, with previous measurements. Two possible scenarios to explain the strength below 1 MeV above the neutron separation energy were proposed in that study: a single p-wave resonance or a mixture of an s-wave virtual state with a weaker p- or d-wave resonance. Comparisons of recent invariant mass and the (d,p) experiments show good agreement between the transfer measurement and the two most recent high-energy nucleon removal measurements.

Theoretical study of elastic electron scattering by zinc atoms in the framework of relativistic optical potential model

A theoretical study of integral and differential cross sections as well as of spin-polarization effects is reported for elastic electron scattering by zinc atoms at collision energies up to 3 keV. It has been shown that a P-wave shape resonance appears in the low-energy range of the integral cross sections. Its energy is about 0.19 and 0.20 eV, while its width is about 0.309 and 0.356 eV for the j = 3/2 and j = 1/2 total angular momentum of the electron, respectively. The differential cross sections of scattering and the Sherman-functions S(E,θ) are computed by the parameter-free complex optical potential method. The calculated data are in a good overall agreement with the available experimental and theoretical data in the literature. The energy and angular positions have been located for five critical minima in the differential cross sections. The low-energy minimum is located at [6.63 eV; 102.34°], while the high-energy minimum is at [347.53 eV; 124.11°]. Ten points for the scattered electrons' total spin-polarization (S=±1) have been found in the vicinity of the critical minima along with the energy and the angular widths of the spin-polarization peaks (where |S|≥0.9).

Emergence of 4H Jπ = 1− resonance in contact theories

We obtain the s- and p-wave low-energy scattering parameters for n3H elastic scattering and the position of the 4H Jπ=1− resonance using the pionless effective field theory at leading order. Results are extracted with three numerical techniques: confining the system in a harmonic oscillator trap, solving the Faddeev-Yakubovsky equations in configuration space, and using an effective two-body cluster approach. The renormalization of the theory for the relevant amplitudes is assessed in a cutoff-regulator range between 1fm−1 and 10fm−1.Most remarkably, we find a cutoff-stable/RG-invariant resonance in the 4H Jπ=1− system. This p-wave resonance is a universal consequence of a shallow two-body state and the introduction of a three-body s-wave scale set by the triton binding energy. The stabilization of a resonant state in a few-fermion system through pure contact interactions has a significant consequence for the powercounting of the pionless theory. Specifically, it suggests the appearance of similar resonant states also in larger nuclei, like 16-oxygen, in which the theory's leading order does not predict stable states. Those resonances would provide a starting state to be moved to the correct physical position by the perturbative insertion of sub-leading orders, possibly resolving the discrepancy between data and contact EFT.

Lagrange-mesh calculations of P-wave resonances in three-body atomic systems

The resonance energies and widths of the P-wave states of helium and of the positronium ion are studied under the hypothesis that their constituting particles interact trough pure or screened Coulomb forces. The resonances are investigated by combining the Lagrange-mesh method and the complex scaling method. This approach is proved to be efficient: rather simple to implement, fast, and accurate. The obtained results improve by several orders of magnitude the best literature results.

Low-energy scatterings and pseudopotential of polarized quadrupoles

We investigate the low-energy scattering properties of two identical particles interacting via the polarized quadrupolar interaction. It is shown that a series of s- and p-wave resonances appear for identical bosons and fermions, respectively, as the strength of the quadrupolar interaction increases. Interestingly, scattering resonances also appear on the generalized scattering length corresponding to the coupling between the s and d waves. This observation inspires us to propose a new pseudopotential for the quadrupolar interaction. We also explore the bound-state properties of two particles in both free space and harmonic traps.

Dynamics of atoms within atoms

Recent experiments with Bose–Einstein condensates have entered a regime in which thousands of ground-state condensate atoms fill the Rydberg-electron orbit. After the excitation of a single atom into a highly excited Rydberg state, scattering off the Rydberg electron sets ground-state atoms into motion, such that one can study the quantum-many-body dynamics of atoms moving within the Rydberg atom. Here we study this many-body dynamics using Gross–Pitaevskii and truncated Wigner theory. Our simulations focus in particular on the scenario of multiple sequential Rydberg excitations on the same rubidium condensate which has become the standard tool to observe quantum impurity dynamics in Rydberg experiments. We investigate to what extent such experiments can be sensitive to details in the electron–atom interaction potential, such as the rapid radial modulation of the Rydberg molecular potential, or p-wave shape resonance. We demonstrate that both effects are crucial for the initial condensate response within the Rydberg orbit, but become less relevant for the density waves emerging outside the Rydberg excitation region at later times. Finally we explore the local dynamics of condensate heating. We find that it provides only minor corrections to the mean-field dynamics. Combining all these insights, our results suggest Bose–Einstein condensates as a viable platform for the in situ and real time interrogation of ultra-cold chemistry dynamics involving Rydberg states.

Semiempirical Calculations on Low-Energy Electron Scattering by Zn and Cd Atoms

Since total cross section measurements for electron scattering by Zn and Cd performed in the 1970s, the existence of p-wave shape resonances below 1 eV are well established in the literature. It was suggested that a second d-wave shape resonance could exist in both systems at an energy slightly higher than the one recorded for the p-wave but still below the inelastic threshold. We report elastic scattering calculations for electron collisions with Zn and Cd atoms below 4 eV using a semiempirical approach, as well the scattering length for both targets. Our results show that, indeed, the d-wave shape resonance is found in Zn but absent in Cd. In fact, our cross sections and the few other ones available for this energy range are in discrepancy with the available experimental total cross sections for Cd.

Study of the four-body decays BS0→ππππ in the perturbative QCD approach

In this work, we analyse the CP-averaged branching ratios and direct CP-violating asymmetries of the four-body decays B_{S} \rightarrow \pi\pi\pi\pi decay from the S-wave resonances, f_{0}(980) and f_{0}(500) and P-wave resonances, \rho(770) by introducing the S-wave and P-wave \pi\pi distribution amplitudes within the framework of the perturbative QCD approach. We also calculate branching ratios of the two-body decays B^{0}_{S}\rightarrow\rho^{0}\rho^{0}, B^{0}_{S}\rightarrow\rho^{+}\rho^{-} from the corresponding quasi-two-body decays models and compare our results with those obtained in previous perturbative QCD approach, QCD factorization approach and FAT approach, it is found that the predictions are consistent with present data within errors. The branching ratios of our calculations for the four-body decays B_{S}\rightarrow \pi\pi\pi\pi are at the order of the 10^{-7}. For the CP-violating asymmetries, we found that CP-violating asymmetry can be enhanced largely by the \rho-\omega mixing resonances when \pi\pi pairs masses are in the vicinity of \omega resonance.

On the Energy Dependence of the Rate of Muon Transfer from Proton to Oxygen

The results of calculations of the muon transfer rate from the 1S state of muonic hydrogen to the nucleus of a free oxygen atom are presented in the interval of collision energies from 10^(-4) to 10 eV. The calculations were performed within a version of the perturbed stationary states method proposed earlier. The electron screening in the entrance channel of the transfer reaction was taken into account. A p-wave resonance in the transfer rate is predicted at collision energies of about 0.1 eV. This result is of interest in the context of the planned laser experiment on precise measurements of the hyperfine splitting energy of the 1S state of muonic hydrogen.

Probing open- and closed-channel p -wave resonances

We study the near-threshold molecular and collisional physics of a strong $^{40}$K p-wave Feshbach resonance through a combination of measurements, numerical calculations, and modeling. Dimer spectroscopy employs both radio-frequency spin-flip association in the MHz band and resonant association in the kHz band. Systematic uncertainty in the measured binding energy is reduced by a model that includes both the Franck-Condon overlap amplitude and inhomogeneous broadening. Coupled-channels calculations based on mass-scaled $^{39}$K potentials compare well to the observed binding energies and also reveal a low-energy p-wave shape resonance in the open channel. Contrary to conventional expectation, we observe a nonlinear variation of the binding energy with magnetic field, and explain how this arises from the interplay of the closed-channel ramping state with the near-threshold shape resonance in the open channel. We develop an analytic two-channel model that includes both resonances as well as the dipole-dipole interactions which, we show, become important at low energy. Using this parameterization of the energy dependence of the scattering phase, we can classify the studied $^{40}$K resonance as broad. Throughout the paper, we compare to the well understood s-wave case, and discuss the significant role played by van der Waals physics. The resulting understanding of the dimer physics of p-wave resonances provides a solid foundation for future exploration of few- and many-body orbital physics.

The [formula omitted]P[formula omitted] states of exponential cosine-screened heliumlike atoms

We investigate the singly-excited and doubly-excited 1,3Po states of screened-heliumlike atoms (Z=3-10), starting from Li+ to Ne8+ under the influence of exponential cosine-screened (ECS) Coulomb potentials. Pseudo-random-parameters dependent correlated exponential wave functions are used to represent the correlation effects between the charged particles. The singly-excited 1s2p 1,3P states are also estimated based on the Ritz variational method. The doubly excited resonance energies and widths are determined using the stabilization method. A total of 9 P-wave resonances including four members in the 2snp+ (2 ≤n≤ 5) series, three members in the 2snp−(3 ≤n≤ 5) series, and two members in the 2pnd (n=3, 4) series for each screened-systems below the 2s 2S thresholds of the respective one-electron subsystems are reported. The singly-excited state energies for each system and each screening parameter below the n=1 thresholds of the respective subsystems are also reported. The singly-excited states of ECS-heliumlike systems (Z= 6–10) and the doubly-excited 1,3Po states of the ECS-heliumlike systems are presented for the first time in the literature.

Pseudogap in a crystalline insulator doped by disordered metals

Key to our understanding of how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber. Even in phases of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still has a band structure. Theoretical models for the band structure of liquid metals were formulated more than five decades ago1-15, but, so far, band-structure renormalization and the pseudogap induced by resonance scattering have remained unobserved. Here we report the observation of the unusual band structure at the interface of a crystalline insulator (black phosphorus) and disordered dopants (alkali metals). We find that a conventional parabolic band structure of free electrons bends back towards zero wavenumber with a pseudogap of 30-240millielectronvolts from the Fermi level. This is wavenumber renormalization caused by resonance scattering, leading to the formation of quasi-bound states in the scattering potential of alkali-metal ions. The depth of this potential tuned by different kinds of disordered alkali metal (sodium, potassium, rubidium and caesium) allows the classification of the pseudogap of p-wave and d-wave resonance. Our results may provide a clue to the puzzling spectrum of various crystalline insulators doped by disordered dopants16-20, such as the waterfall dispersion observed in copper oxides.

The massless Dirac equation in two dimensions: zero-energy obstructions and dispersive estimates

We investigate $L^1\\to L^\\infty$ dispersive estimates for the massless two dimensional Dirac equation with a potential. In particular, we show that the Dirac evolution satisfies the natural $t^{-\\frac{1}{2}}$ decay rate, which may be improved to $t^{-\\frac{1}{2} - \\gamma}$ for any $0\\leq \\gamma<\\frac{3}{2}$ at the cost of spatial weights. We classify the structure of threshold obstructions as being composed of a two dimensional space of p-wave resonances and a finite dimensional space of eigenfunctions at zero energy. We show that, in the presence of a threshold resonance, the Dirac evolution satisfies the natural decay rate except for a finite-rank piece. While in the case of a threshold eigenvalue only, the natural decay rate is preserved. In both cases we show that the decay rate may be improved at the cost of spatial weights.

Energy-dependent angular distribution of individual γ rays in the La139(n,γ)La140* reaction

Neutron energy-dependent angular distributions were observed for individual $\gamma$-rays from the 0.74 eV p-wave resonance of $^{139}$La+$n$ to several lower excited states of $^{140}$La. The $\gamma$-ray signals were analyzed in a two dimensional histogram of the $\gamma$-ray energy, measured with distributed germanium detectors, and neutron energy, determined with the time-of-flight of pulsed neutrons, to identify the neutron energy dependence of the angular distribution for each individual $\gamma$-rays. The angular distribution was also found for a photopeak accompanied with a faint p-wave resonance component in the neutron energy spectrum. Our results can be interpreted as interference between s- and p-wave amplitudes which may be used to study discrete symmetries of fundamental interactions.

First Results of the 140Ce(n,γ)141Ce Cross-Section Measurement at n_TOF

An accurate measurement of the 140Ce(n,γ) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the 140Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in 140Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the 140Ce Maxwellian-averaged cross-section.

Four-body decays B(s) \u2192 (K\u03c0)S/P(K\u03c0)S/P in the perturbative QCD approach

We investigate the four-body decays B(s) → (Kπ)S/P(Kπ)S/P in the Kπ-pair invariant mass region around the K*(892) resonance in the perturbative QCD (PQCD) approach, where (Kπ)S/P denotes a S- or P-wave Kπ configuration. The contributions from the P-wave resonance K*(892) and from possible S-wave components are included into the parametrization of the Kπ two-meson distribution amplitudes, which are the non-perturbative inputs in this formalism. We calculate the branching ratio for each resonance and observe sizable S-wave contributions to the Bs modes, well consistent with recently available LHCb data. We also deduce the polarization fractions for the {K}^{ast }{overline{K}}^{ast } final states, and compare our predictions to those in previous PQCD analyses of the corresponding two-body B → {K}^{ast }{overline{K}}^{ast } decays. The polarization puzzle associated with the two U-spin related channels B0 → {K}^{ast 0}{overline{K}}^{ast 0} and {B}_s^0to {K}^{ast 0}{overline{K}}^{ast 0} still exists. In addition to direct CP asymmetries, triple-product asymmetries and S-wave induced direct CP asymmetries originating from the interference among various helicity amplitudes, are presented. It is shown that true triple-product asymmetries are rather small, while direct CP asymmetries and S-wave-induced direct CP asymmetries are significant in some decays. Our results will be subject to stringent tests with precise data from B factories in the near future.

Triplet P states in Ps− using correlated exponential wave functions

We calculate the resonance parameters (energy and width) for the doubly excited 3Po and 3Pe states in Ps− using correlated exponential wave functions. The calculations are based on the method of complex-coordinate rotation. The resonance energies and widths for the triplet P-wave Feshbach and shape resonances with both even and odd parities in Ps− ion associated with the N = 2, 3, 4, 5 Ps thresholds are reported. Our predications are in agreement with the available results. Few Feshbach and shape resonance parameters are reported for the first time in the literature. In view of a recent experiment on a singlet P-wave shape resonance state in Ps−, it is highly expected that the predications obtained from this study for the triplet P-wave resonance states will provide useful information for the future resonance experiments in Ps−. Furthermore, our findings could be found useful for the research communities of atomic physics, nuclear physics, and semiconductor quantum dots including excitons.