Search results for "pole [resonance]"
showing 10 items of 238 documents
Laser spectroscopy for nuclear structure physics
2016
High-resolution laser spectroscopy is an established powerful tool in the study of nuclear shape, size and multipole moments. Measurements of the hyperfine structures and isotope shifts in the atomic spectra of radioactive nuclei provide unique insight into the evolution of the nuclear macroscopic shape and microscopic structure. These measurements can be made with high precision and high sensitivity and applied directly on-line at radioactive nuclear beam facilities. Recent measurements, advances at facilities and the future direction of the field are reviewed. A summary of experimental data is presented. peerReviewed
Polarizability effects in electronic and muonic atoms
1983
TheS state polarizability shifts are derived from the virtual forward Compton scattering in the unretarded dipole approximation. In the non-relativistic limit ω N /2m≪1, the shift is proportional to the photonuclear sum rule σ−3/2, while in the relativistic limit ω N /2m≫1 it is proportional to a logarithmically weighted σ−2 sum rule. In both cases, the characteristic momentum transfer is (2mω N )1/2. The non-locality from the intermediate lepton propagation removes the divergence typical of the static limit. Explicit formulas for the shifts are given for both the relativistic and non-relativistic limits.
General Multipole Expansion of Polarization Observables in Deuteron Electrodisintegration
2002
Formal expressions are derived for the multipole expansion of the structure functions of a general polarization observable of exclusive electrodisintegration of the deuteron using a longitudinally polarized beam and/or an oriented target. This allows one to exhibit explicitly the angular dependence of the structure functions by expanding them in terms of the small rotation matrices $d^j_{m'm}(\theta)$, whose coefficients are given in terms of the electromagnetic multipole matrix elements. Furthermore, explicit expressions for the coefficients of the angular distributions of the differential cross section including multipoles up to $L_{max}=3$ are listed in tabular form.
Pygmy dipole resonance in208Pb
2012
Scattering of protons of several hundred MeV is a promising new spectroscopic tool for the study of electric dipole strength in nuclei. A case study of 208Pb shows that at very forward angles J^pi = 1- states are strongly populated via Coulomb excitation. A separation from nuclear excitation of other modes is achieved by a multipole decomposition analysis of the experimental cross sections based on theoretical angular distributions calculated within the quasiparticle-phonon model. The B(E1) transition strength distribution is extracted for excitation energies up to 9 MeV, i.e., in the region of the so-called pygmy dipole resonance (PDR). The Coulomb-nuclear interference shows sensitivity to…
High precision measurement of the11Li and9Li quadrupole moment ratio using zero-fieldβ-NQR
2013
The ratio of electric quadrupole moments of 11 Li and 9 Li was measured using the zero-field β-detected nuclear quadrupole resonance technique at TRIUMFISAC. The precision on the ratio Q11/Q9 = 1.0775(12) was improved by more than one order of magnitude and an absolute value for the quadrupole moment of 11 Li was inferred. Systematic effects, as argued here, are not expected to contribute to the ratio on this scale. The zero-field spin-lattice relaxation time for 8 Li implanted within SrTiO3 at 295K in zero-field was found to be T1 = 1.73(2)s. A comparison of the quadrupole moments of 9,11 Li and their ratio is made with the latest models, however, no conclusion may yet be drawn owing to th…
Role of theN*(1535)resonance and theπ−p→KYamplitudes in the OZI forbiddenπN→ϕNreaction
2008
We study the $\ensuremath{\pi}N\ensuremath{\rightarrow}\ensuremath{\phi}N$ reaction close to the $\ensuremath{\phi}N$ threshold within the chiral unitary approach, by combining the ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\Sigma}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\Sigma}}^{0}$, and ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{0}\ensuremath{\Lambda}$ amplitudes with the coupling of \ensuremath{\phi} to the $K$ components of the final states of these reactions via quantum loops. We obtain good agreement with experiment when the dominant ${\ensuremath{\pi}}^{\ensuremath{…
Dispersion Theory in Electromagnetic Interactions
2018
We review various applications of dispersion relations (DRs) to the electromagnetic structure of hadrons. We discuss the way DRs allow one to extract information on hadron structure constants by connecting information from complementary scattering processes. We consider the real and virtual Compton scattering processes off the proton, and summarize recent advances in the DR analysis of experimental data to extract the proton polarizabilities, in comparison with alternative studies based on chiral effective field theories. We discuss a multipole analysis of real Compton scattering data, along with a DR fit of the energy-dependent dynamical polarizabilities. Furthermore, we review new sum rul…
Truncated partial-wave analysis of a complete experiment for photoproduction of two pseudoscalar mesons on a nucleon
2013
A truncated partial wave analysis for the photoproduction of two pseudoscalar mesons on a nucleon is discussed with respect to the determination of a complete set of observables. For the selection of such a set we have applied a criterion previously developed for photo- and electrodisintegration of a deuteron, which allows one to find a 'minimal' set of observables for determining the partial wave amplitudes up to possible discrete ambiguities. The question of resolving the remaining ambiguities by invoking additional observables is discussed for the simplest case, when the partial wave expansion is truncated at the lowest total angular momentum of the final state $J_{max}=1/2$. The resulti…
Polarization observables in elastic electron deuteron scattering including parity and time reversal violating contributions
2000
The general formalism for polarization observables in elastic electron deuteron scattering is extended to incorporate parity and time reversal violating contributions. Parity violating effects arise from the interference of $\gamma$ and $Z$ exchange as well as from the hadronic sector via a small parity violating component in the deuteron. In addition we have allowed for time reversal invariance violating contributions in the hadronic sector. Formal expressions for the additional structure functions are derived, and their decomposition into the various multipole contributions are given explicitly.
Pole positions and residues from pion photoproduction using the Laurent-Pietarinen expansion method
2014
We have applied a new approach to determine the pole positions and residues from pion photoproduction multipoles. The method is based on a Laurent expansion of the partial wave T-matrices, with a Pietarinen series representing the regular part of energy-dependent and single-energy photoproduction solutions. The method has been applied to multipole fits generated by the MAID and GWU/SAID groups. We show that the number and properties of poles extracted from photoproduction data correspond very well to results from $\pi$N elastic data and values cited by Particle Data Group (PDG). The photoproduction residues provide new information for the electromagnetic current at the pole position, which …