Search results for "Isospin"
showing 10 items of 264 documents
First observation of the isospin violating decayJ/ψ→ΛΣ¯0+c.c.
2012
Using a sample of (225.2 +/- 2.8) x 10(6) J/psi events collected with the BESIII detector, we present results of a study of J/psi -> gamma Lambda(Lambda) over bar and report the first observation of the isospin violating decay J/psi -> Lambda(Sigma) over bar (0) + c.c., in which (Sigma) over bar (0) decays to gamma (Lambda) over bar. The measured branching fractions are B(J/psi -> (Lambda) over bar Sigma(0)) = (1.46 +/- 0.11 +/- 0.12) x 10(-5) and B(J/psi -> Lambda(Sigma) over bar (0)) = (1.37 +/- 0.12 +/- 0.11) x 10(-5). We search for Lambda(1520) -> gamma Lambda decay, and find no evident signal, and an upper limit for the product branching fraction B(J/psi -> Lambda(Lambda) over bar (152…
The S01 − Λ(1405) and − Λ(1670) resonances in meson-baryon unitarized coupled channel chiral perturbation theory
2003
Abstract The s-wave meson-baryon system with strangeness S = −1 and isospin I = 0 is studied using the Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry. The needed two particle irreducible potential is taken from lowest order Chiral Perturbation Theory in a relativistic formalism. The K N, πΣ, νΛ , and KΞ two-body channels have been included. Off-shell behavior is parameterized in terms of low energy constants, which outnumber those assumed in previous works and provide a better fit to the data. The masses, widths and branching ratios of the Λ(1405) and Λ(1670) resonances are determined. In our model, we find no one but two resonances in the Λ(1405) region.
PREDICTION OF HIDDEN CHARM BARYONS WITH HEAVY QUARK SPIN AND LOCAL HIDDEN GAUGE SYMMETRIES
2014
In our talk, we explore a coupled channel unitary approach to investigate the meson baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge, we find four basic states which are bound by about 50 MeV with respect to the corresponding [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] thresholds respectively and decay mostly into ηcN and J/ψN. All the states appear in isospin I = 1/2, some of which are degenerated in different momentum J.
Multimeson model for the D+→K+K−K+ decay amplitude
2018
We propose an approach to describe the ${D}^{+}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}^{+}{K}^{+}$ decay amplitude, based on chiral effective Lagrangians, which can be used to extract information about $K\overline{K}$ scattering. It relies on factorization and its main novel feature is the role played by multimeson interactions characteristic of chiral symmetry. Our trial function is an alternative to the widely used isobar model and includes both nonresonant three-body interactions and two-body rescattering amplitudes, based on coupled channels and resonances, for S- and P-waves with isospin 0 and 1. The latter are unitarized in the $K$-matrix approximation and represent the only s…
Local nuclear energy density functional at next-to-next-to-next-to-leading order
2008
We construct nuclear energy density functionals in terms of derivatives of densities up to sixth, next-to-next-to-next-to-leading order (N3LO). A phenomenological functional built in this way conforms to the ideas of the density matrix expansion and is rooted in the expansions characteristic to effective theories. It builds on the standard functionals related to the contact and Skyrme forces, which constitute the zero-order (LO) and second-order (NLO) expansions, respectively. At N3LO, the full functional with density-independent coupling constants, and with the isospin degree of freedom taken into account, contains 376 terms, while the functionals restricted by the Galilean and gauge symme…
Coherent $\eta$-photoproduction on $^4$He and $^{12}$C in the near-threshold region
1997
Coherent $\eta$ meson photoproduction on $^4$He and $^{12}$C is considered in the near-threshold region. The elementary $\eta$ photoproduction operator includes contributions from the $S_{11}(1535)$ and $D_{13}(1520)$ resonances as well as $t$-channel vector meson exchange and the nucleon pole terms. Due to the suppression of the dominant $S_{11}(1535)$ resonance for spin and isospin saturated nuclei, the reaction is mainly governed by $\omega$ exchange. Furthermore, the influence of Fermi motion and of different prescriptions for the choice of the invariant reaction energy $W_{\gamma N}$ in the elementary amplitude is studied.
Strong-interaction Isospin-symmetry Breaking Within the Density Functional Theory
2015
The conventional Skyrme interaction is generalized by adding zero-range charge-symmetry-breaking and charge-independence-breaking terms, and the corresponding energy density functional is derived. It is shown that the extended model accounts for experimental values of mirror and triplet displacement energies (MDEs and TDEs) in sd-shell isospin triplets with, on average, about 100~keV precision using only two additional adjustable coupling constants. Moreover, the model is able to reproduce, for the first time, the A=4n versus A=4n+2 staggering of the TDEs.
Isospin Character of Low-Lying Pygmy Dipole States inPb208via Inelastic Scattering ofO17Ions
2014
The properties of pygmy dipole states in Pb-208 were investigated using the Pb-208(O-17, O-17'gamma) reaction at 340 MeV and measuring the gamma decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted gamma rays and of the scattered particles were measured. The results are compared with (gamma, gamma') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2(+) and 3(-) states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first t…
Parity-violating asymmetry in elastic electron-nucleus scattering due to weak neutral currents
1980
Parity-violating asymmetries are calculated for elastic scattering of electrons on nuclei of arbitrary spin and isospin. Possible dependences on nuclear-model input are shown to be weak. Elastic electron scattering at intermediate energies may become an important tool in studying the structure of hadronic weak neutral currents.
Observation of a Neutral Structure near theDD¯*Mass Threshold ine+e−→(DD¯*)0π0ats=4.226and 4.257 GeV
2015
A neutral structure in the D (D) over bar* system around the D (D) over bar* mass threshold is observed with a statistical significance greater than 10 sigma in the processes e(+)e(-) -> D+D*(-)pi(0) + c.c. and e(+)e(-) -> D-0(D) over bar*(0)pi(0) + c.c. at root s = 4.226 and 4.257 GeV in the BESIII experiment. The structure is denoted as Z(c)(3885)(0). Assuming the presence of a resonance, its pole mass and width are determined to be [3885.7(-5.7)(+4.3) (stat) +/- 8.4(syst)] MeV/c(2) and [35(-12)(+11) (stat) +/- 15(syst)] MeV, respectively. The Born cross sections are measured to be sigma[e(+)e(-) -> Z(c)(3885)(0)pi(0); Z(c)(3885)(0) -> D (D) over bar*] = [77 +/- 13(stat) +/- 17(syst)] pb …