General Properties of Higher-Spin Fermion Interaction Currents and Their Test in πN-Scattering

The currents of higher-spin fermion interactions with zero- and half-spin particles are derived. They can be used for the N*(J) ↔ Nπ-transitions (N*(J) is thenucleon resonance with the J spin). In accordance with the theorem on currents and fields, the spin-tensors of these currents are traceless, and their products with the γ-matrices and the higher-spin fermion momentum vanish, similarly to the field spin-tensors. Such currents are derived explicitly for J=3/2and 5/2. It is shown that, in the present approach, the scale dimension of a higher spin fermion propagator equals to –1 for any J ≥ 1/2. The calculations indicate that the off-mass-shell N* contributions to the s-channel amplitudes correspond to J = JπN only ( JπN is the total angular momentum of the πN-system). As contrast, in the usually exploited approaches, such non-zero amplitudes correspond to 1/2 ≤ JπN ≤ J. In particular, the usually exploited approaches give non-zero off-mass-shell contributions of the ∆(1232)-resonance to the amplitudes S31, P31( JπN = 1/2) and P33, D33(JπN = 3/2), but our approach – to P33 and D33 only. The comparison of these results with the data of the partial wave analysis on the S31-amplitude in the ∆(1232)-region shows the better agreement for the present approach.

Monaural Musical Octave Sound Separation Using Relaxed Extended Common Amplitude Modulation

Monaural music sound separation isolates individual instrument sources from a mono-channel polyphonic mixture. The primary challenge is to separate the source partials overlapped in time-frequency regions, especially for the full overlapping cases that at least one source does not have any nonoverlapping partial. Due to the lack of effective methods to separate the sources with full overlapping partials, this paper put forward a relaxed extended common amplitude modulation (RECAM) approach to deal with the octave sound separation, one of the most difficult cases. Our strategy uses a multi-band co-processing way for each short-time partial wave segment. Extensive experiments are conducted on octave mixture samples drawn from the Iowa University Musical Instrument Database. Results confirm that our RECAM achieves the best separation performance. For nonvibrato and vibrato mixtures, the average improvement of RECAM in each measure exceeds [Formula: see text]dB and [Formula: see text]dB, respectively.

Probing anomalous γγγZ couplings through γZ production in γγ collisions at the CLIC

We have estimated the sensitivity to the anomalous couplings of the γγγZ vertex in the γγ → γZ scattering of the Compton backscattered photons at the CLIC. Both polarized and unpolarized collisions at the e+e− energies 1500 GeV and 3000 GeV are addressed, and anomalous contributions to helicity amplitudes are derived. The differential and total cross sections are calculated. We have obtained 95% C.L. exclusion limits on the anomalous quartic gauge couplings (QGCs). They are compared with corresponding bounds derived for the γγγZ couplings via γZ production at the LHC. The constraints on the anomalous QGCs are one to two orders of magnitude more stringent that at the HL-LHC. The partial-wave unitarity constraints on the anomalous couplings are examined. It is shown that the unitarity is not violated in the region of the anomalous QGCs studied in the paper.

Two-particle scattering from finite-volume quantization conditions using the plane wave basis

We propose an alternative approach to Lüscher’s formula for extracting two-body scattering phase shifts from finite volume spectra with no reliance on the partial wave expansion. We use an effective-field-theory-based Hamiltonian method in the plane wave basis and decompose the corresponding matrix elements of operators into irreducible representations of the relevant point groups. The proposed approach allows one to benefit from the knowledge of the long-range interaction and avoids complications from partial wave mixing in a finite volume. We consider spin-singlet channels in the two-nucleon system and pion-pion scattering in the ρ-meson channel in the rest and moving frames to illustrate the method for non-relativistic and relativistic systems, respectively. For the two-nucleon system, the long-range interaction due to the one-pion exchange is found to make the single-channel Lüscher formula unreliable at the physical pion mass. For S-wave dominated states, the single-channel Lüscher method suffers from significant finite-volume artifacts for a L = 3 fm box, but it works well for boxes with L > 5 fm. However, for P-wave dominated states, significant partial wave mixing effects prevent the application of the single-channel Lüscher formula regardless of the box size (except for the near-threshold region). Using a toy model to generate synthetic data for finite-volume energies, we show that our effective-field-theory-based approach in the plane wave basis is capable of a reliable extraction of the phase shifts. For pion-pion scattering, we employ a phenomenological model to fit lattice QCD results at the physical pion mass. The extracted P-wave phase shifts are found to be in a good agreement with the experimental results.

Degeneracy of light scattering and absorption by a single nanowire

We theoretically and numerically prove that under an electromagnetic plane wave with linear polarization incident normally to a single nanowire, there exists a power diagram that could indicate scattering properties for any system configurations, material parameters, and operating wavelength. We demonstrate the distinct power distribution boundary in absorption, scattering, and extinction for a generalized nanowire with any partial wave modes dominant. In the boundary, each dominant scattering coefficients remain constant, and its energy performance would display superabsorbers or superscatterers. Interestingly, for a system with larger partial wave modes dominant, the occupied domain in the power diagram could completely cover that with lower ones. Hence, a system with different levels of partial wave modes can display the same power results, reflecting the degeneracy. This degenerate property could release more degrees of freedom in design of energy harvesting devices and sensors. We demonstrate several systems based on realistic materials to support our findings.

Symmetry resolved atomic photoionization phase shift by attosecond coincidence metrology

Attosecond chronoscopy is central to the understanding of ultrafast electron dynamics from gas to condensed phase with attosecond temporal resolution. It has, however, not yet been able to determine the timing of individual partial waves, and steering their contribution has been a substantial challenge. Here, we develop a polarization-skewed attosecond chronoscopy to reveal their roles from the angle-resolved photoionization phase shifts in rare gas atoms. By scanning the relative polarization angle between an extreme-ultraviolet attosecond pulse train and a phase-locked near-infrared laser field serving as a partial wave meter, we break the cylindrical symmetry and observe an emission direction dependent phase shift in the photoionized electron momenta. The experimental observations are well supported by numerical simulations using the R-matrix with time-dependence method, and by analytical analysis using the soft-photon approximation. Our symmetry-resolved, partial-wave analysis identifies the transition rate and phase shifts of each individual ionization pathway in the attosecond photoelectron emission dynamics. Our findings provide critical insights into the ubiquitous attosecond optical timer and the underlying attosecond photoionization dynamics, thereby offer new perspectives for the control, manipulation, and exploration of ultrafast electron dynamics in complex systems.