Nuclear Theory·nucl-th

Tuesday·March 10, 2015

12 papers—5 primary·7 cross-listed

01
Nonmesonic Weak Decay Dynamics from proton spectra of $Λ$ -Hypernuclei
Franjo Krmpotic🇦🇷 · Cláudio De Conti🇧🇷
A novel comparison between the data and the theory is proposed for the nonmesonic (NM) weak decay of hypernuclei. Instead of confronting the primary decay rates, as is usually done, we focus attention on the effective decay rates that are straightforwardly related with the number of emitted particles. Proton kinetic energy spectra of $_{Λ}^{5}$ He, $_{Λ}^{7}$ Li, $_{Λ}^{9}$ Be, $_{Λ}^{11}$ B, $_{Λ}^{12}$ C, $_{Λ}^{13}$ C, $_{Λ}^{15}$ N and $_{Λ}^{16}$ O, measured by FINUDA, are evaluated theoretically. The Independent Particle Shell Model (IPSM) is used as the nuclear structure framework, while the dynamics is described by the One-Meson-Exchange (OME) potential. Only for the $_{Λ}^{5}$ He, $_{Λ}^{7}$ Li, and $_{Λ}^{12}$ C hypernuclei is it possible to make a comparison with the data, since for the rest there is no published experimental information on number of produced hypernuclei. Considering solely the one-nucleon-induced ( $1 N$ -NM) decay channel, the theory reproduces correctly the shapes of all three spectra at medium and high energies ( $E_{p} \geq 40$ MeV). Yet, it greatly overestimates their magnitudes, as well as the corresponding transition rates when the full OME ( $π + K + η + ρ + ω + K^{*}$ ) model is used. The agreement is much improved when only the $π + K$ mesons with soft dipole cutoff parameters participate in the decay process. We find that the IPSM is a fair first order approximation to disentangle the dynamics of the $1 N$ -NM decay, the knowledge of which is indispensable to inquire about the baryon-baryon strangeness-flipping interaction. It is shown that the IPSM provides very useful insights regarding the determination the $2 N$ -NM decay rate. In a new analysis of the FINUDA data, we derive two results for this quantity with one of them close to that obtained previously.
nucl-thIJMPE(2014)·2 citations
02
Periodic interference structures in the time-like proton form factor
Andrea Bianconi🇮🇹 · Egle Tomasi-Gustafsson🇫🇷
An intriguing and elusive feature of the timelike hadron form factor is the possible presence of an imaginary part associated to rescattering processes. We find evidence of that in the recent and precise data on the proton timelike form factor measured by the BABAR collaboration. By plotting these data as a function of the 3-momentum of the relative motion of the final proton and antiproton, a systematic sinusoidal modulation is highlighted in the near-threshold region. Our analysis attributes this pattern to rescattering processes at a relative distance of 0.7-1.5 fm between the centers of the forming hadrons. This distance implies a large fraction of inelastic processes in $p ˉ p$ interactions, and a large imaginary part in the related $e^{+} e^{-} \to p ˉ p$ reaction because of unitarity.
nucl-thhep-phPRL(2015)·88 citations
03
Determination of the neutrino mass by electron capture in 163 Holmium and the role of the three-hole states in 163 Dysprosium
Amand Faessler🇩🇪 · Christian Enss🇩🇪 · Loredana Gastaldo🇩🇪 · F. Simkovic🇷🇺
163 Holmium to 163 Dysprosium is probably due to the small Q value of about 2.5 keV the best case to determine the neutrino mass by electron capture. The energy of the Q value is distributed between the excitation of Dysprosium (and the neglected small recoil of Holmium) and the relativistic energy of the emitted neutrino including the restmass. The reduction of the upper end of the deexcitation spectrum of Dysprosium below the Q value allows to determine the neutrino mass. The excitation of Dysprosium can be calculated in the sudden approximation of the overlap of the electron wave functions of Holmium minus the captured electron and one-, two-, three- and multiple hole-excitations in Dysprosium. Robertson and the author have calculated the influence of the two-hole states on the Dysprosium deexitation spectrum. Here for the first time the influence of the three-hole states on the deexcitation bolometer spectrum of 163 Dysprosium is presented. The electron wave functions and the overlaps are calculated selfconsitently in a fully relativistic and antisymmetrized Dirac-Hartree-Fock approach in Holmium and in Dysprosium. The electron orbitals in Dysprosium are determined including the one-hole states in the selfconsistent iteration. The influence of the three-hole states on the deexcitation (by X-rays and Auger electrons) spectrum is hardly visible. The three-hole states seem not to be important for the determination of the neutrino mass.
nucl-thphysics.atom-phPRC(2015)·39 citations
04
Higher-rank discrete symmetries in the IBM. I Octahedral shapes: general Hamiltonian
P. Van Isacker (GANIL)🇫🇷 · A. Bouldjedri🇩🇿 · S. Zerguine🇩🇿
In the context of the interacting boson model with $s$ , $d$ and $g$ bosons, the conditions for obtaining an intrinsic shape with octahedral symmetry are derived for a general Hamiltonian with up to two-body interactions.
nucl-thNPA(2015)·8 citations
05
A study of $d^{*} (2380) \to d π π$ decay width
Yubing Dong🇨🇳 · Pengnian Shen🇨🇳 · Fei Huang🇨🇳 · Zongye Zhang🇨🇳
The decay widths of the $\ds \to d π^{0} π^{0}$ and $\ds \to d π^{+} π^{-}$ processes are explicitly calculated in terms of our chiral quark model. By using the experimental ratios of cross sections between various decay channels, the partial widths of the $\ds \to p n π^{0} π^{0}$ , $\ds \to p n π^{+} π^{-}$ , $\ds \to pp π^{0} π^{-}$ , and $\ds \to nn π^{+} π^{0}$ channels are also extracted. Further including the estimated partial width for the $\ds \to p n$ process, the total width of the $\ds$ resonance is obtained. In the first step of the practical calculation, the effect of the dynamical structure on the width of $\ds$ is studied in the single $ΔΔ$ channel approximation. It is found that the width is reduced by few tens of MeV, in comparison with the one obtained by considering the effect of the kinematics only. This presents the importance of such effect from the dynamical structure. However, the obtained width with the single $ΔΔ$ channel wave function is still too large to explain the data. It implies that the $\ds$ resonance will not consist of the $ΔΔ$ structure only, and instead there should be enough room for other structure such as the hidden-color (CC) component. Thus, in the second step, the width of $\ds$ is further evaluated by using a wave function obtained in the coupled $ΔΔ$ and CC channel calculation in the framework of the Resonating Group Method (RGM). It is shown that the resultant total width for $\ds$ is about 69 MeV, which is compatible with the experimental observation of about 75 MeV and justifies our assertion that the $\ds$ resonance is a hexaquark-dominated exotic state.
nucl-thhep-phPRC(2015)·54 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nonmesonic Weak Decay Dynamics from proton spectra of Λ-Hypernuclei

Periodic interference structures in the time-like proton form factor

Determination of the neutrino mass by electron capture in 163 Holmium and the role of the three-hole states in 163 Dysprosium

Higher-rank discrete symmetries in the IBM. I Octahedral shapes: general Hamiltonian

A study of d∗(2380)→dππ decay width

Affiliations

Nonmesonic Weak Decay Dynamics from proton spectra of $Λ$ -Hypernuclei

A study of $d^{*} (2380) \to d π π$ decay width