Charmed baryon semileptonic decays

Ting Miao, Purdue University

Abstract

Results of a systematic study of the charmed baryon semileptonic decays using the CLEO II detector are reported. We make the most precise measurement to date of ${\cal B}(\Lambda\sbsp{c}{+}\to\Lambda\ell\sp+\nu\sb l)\cdot \sigma(e\sp+e\sp-\to\Lambda\sbsp{c}{+}X)=4.77\pm0.25\pm0.66$ pb. We obtain the first model independent upper limit of $\Lambda\sb c$ absolute decay branching ratio ${\cal B}(\Lambda\sbsp{c}{+}\to pK\sp-\pi\sp+).$ A large polarization in $\Lambda\sbsp{c}{+}\to \Lambda e\sp+\nu\sb e$ is observed for the first time in a charmed baryon semileptonic decay and the decay asymmetry parameter is measured to be $\alpha\sb{\Lambda\sb c}=0.89\sbsp{-0.11}{+0.17}\sbsp{-0.05}{+0.09}.$ We make the first observation of $\Xi\sbsp{c}{+}\to\Xi\sp0e\sp+\nu\sb e$ and find ${\cal B}(\Xi\sbsp{c}{+}\to\Xi\sp0e\sp+\nu\sb e)\cdot \sigma(e\sp+e\sp-\to\Xi\sbsp{c}{+}X)=(1.55\pm0.33\pm0.25)$pb and ${\cal B}(\Xi\sbsp{c}{0}\to\Xi\sp-e\sp+\nu\sb e)\cdot \sigma(e\sp+e\sp-\to\Xi\sbsp{c}{0}X)=(0.63\pm0.12\pm0.10)$pb. We give the first charmed cascade hadronic branching ratio upper bounds, ${\cal B}(\Xi\sbsp{c}{+}\to\Xi\sp-\pi\sp+\pi\sp+)\leq (1.4\pm0.3\sbsp{-0.4}{+0.5})\times10\sp{-2}$ and ${\cal B}(\Xi\sbsp{c}{0}\to\Xi\sp-\pi\sp+)\leq (4.3\pm1.3\sbsp{-0.4}{+0.5})\times10\sp{-3}.$ Assuming the $\Xi\sbsp{c}{+}$ and $\Xi\sbsp{c}{0}$ are equally produced in $e\sp+e\sp-$ annihilation events at 10 GeV, the lifetime ratio of $\Xi\sbsp{c}{+}$/$\Xi\sbsp{c}{0}$ is estimated to be $2.46\pm0.7\sbsp{-0.23}{+0.33}.$ Finally from a study of the 3-dimensional angular distributions, the form factor ratio in $\Lambda\sbsp{c}{+}\to\Lambda e\sp+\nu\sb e$ is extracted for the first time to be $R=f\sb2/f\sb1={-}0.25\pm0.14\pm0.08.$

Degree

Ph.D.

Advisors

Shipsey, Purdue University.

Subject Area

Particle physics

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