Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMixing effects of $Sigma^0-Lambda^0$ in $Lambda_c^+$ decays
108
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We analyze the mixing between $Sigma^0$ and $Lambda^0$ based on the baryon masses. We distinguish the contributions from QCD and QED in the baryon mass splittings. We find that the mixing angle between $Sigma^0$ and $Lambda^0$ is $(2.07pm 0.03)times 10^{-2} $, which leads to the decay branching fraction and up-down asymmetry of $Lambda_c^+ to Sigma^0 e^+ u_e$ to be ${cal B}(Lambda_c^+ to Sigma^0 e^+ u_e)=(1.5pm 0.2)times 10^{-5}$ and $alpha(Lambda_c^+ to Sigma^0 e^+ u_e)=-0.86pm 0.04$, respectively. Moreover, we obtain that $Delta {cal B}equiv {cal B}(Lambda_c^+to Sigma^0 pi^+) - {cal B}(Lambda_c^+to Sigma^+pi^0)=(3.8pm 0.5)times 10^{-4}$ and $Delta alpha equivalpha(Lambda_c^+to Sigma^0 pi^+) -alpha(Lambda_c^+to Sigma^+pi^0)=(-1.6pm 0.7)times10^{-2}$, which should vanish without the mixing.
rate research
Read More
We calculate the on-shell $Sigma^0$-$Lambda$ mixing parameter $theta$ with the method of QCD sum rule. Our result is $theta (m^2_{Sigma^0}) =(-)(0.5pm 0.1)$MeV. The electromagnetic interaction is not included.
Properties of hypernuclei are studied in the context of a chiral Lagrangian which successfully describes ordinary nuclei. Lambda-Sigma^0 mixing arises from nondiagonal vertices in flavor space induced by the vector mesons and by the electromagnetic field. The set of Dirac equations for the coupled hyperon system is discussed. Results are presented for energy spectra and electromagnetic properties of hyperons in the nuclear environment. Simple estimates suggest that flavor mixing can lead to sizable changes in the lifetimes of Lambda hypernuclei.
We study the effect of the meson cloud dressing in the octet baryon to decuplet baryon electromagnetic transitions. Combining the valence quark contributions from the covariant spectator quark model with those of the meson cloud estimated based on the flavor SU(3) cloudy bag model, we calculate the transition magnetic form factors at $Q^2=0$ ($Q^2=-q^2$ and $q$ the four-momentum transfer), and also the decuplet baryon electromagnetic decay widths. The result for the $gamma^ast Lambda to Sigma^{ast 0}$ decay width is in complete agreement with the data, while that for the $gamma^ast Sigma^+ to Sigma^{ast +}$ is underestimated the data by 1.4 standard deviations. This achievement may be regarded as a significant advance in the present theoretical situation.
We investigate $S=-1$ hyperon production from the $Lambda_c^+to K^-ppi^+$ and $Lambda_c^+to K^0_Sppi^0$ decays within the effective Lagrangian approach. We consider the $Sigma/Lambda$ ground states, $Lambda(1520)$, $Lambda(1670)(J^p=1/2^-)$, $Lambda(1890)(J^p=3/2^+)$; $Lambda/Sigma$-pole contributions from the combined resonances between 1800 MeV and 2100 MeV; and $N/Delta$-pole and $K^ast$-pole contributions, which include the proton, $Delta(1232)$, and $K(892)$. We calculate the Dalitz plot density $(d^2Gamma/dM_{K^-p}dM_{K^-pi^+}$) for the $Lambda_c^+to K^-ppi^+$ decay. The calculated result is in good agreement with experimental data from the Belle Collaboration. Using the parameters from the fit, we present the Dalitz plot density for the $Lambda_c^+to K^0_Sppi^0$ decay. In our calculation, a sharp peak-like structure near 1665 MeV is predicted in the $Lambda_c^+to K^-ppi^+$ decay because of the interference effects between the $Lambda(1670)$ resonance and $eta$-$Lambda$ loop channels. We also demonstrate that we can access direct information regarding the weak couplings of $Lambda(1670)$ and $Sigma(1670)$ from the $Lambda_c^+to K^0_Sppi^0$ decay. Finally, a possible interpretation for the 1665 MeV structure beyond our prediction is briefly discussed.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
