Measurement of Branching Ratios for Non-leptonic Cabibbo-suppressed Decays of the Charmed-Strange Baryon [Xi]c PDF Download

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Languages : en
Pages : 190

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Book Description
We studied several [Xi]c+ decay modes, most of them with a hyperon in the final state, and determined their branching ratios. The data used in this analysis come from the fixed target experiment SELEX, a multi-stage spectrometer with high acceptance for forward interactions, that took data during 1996 and 1997 at Fermilab with 600 GeV=c (mainly [Sigma]-, [pi]- ) and 540 GeV/c (mainly p) beams incident on copper and carbon targets. The thesis mainly details the first observation of two Cabibbo-suppressed decay modes, [Xi]c+ 2![Sigma]+[pi]-[pi]+ and [Xi]c+ 2![Sigma]-[pi]+[pi]+. The branching ratios of the decays relative to the Cabibbo-favored [Xi]c+ 2![Sigma]-[pi]+[pi]+ are measured to be: [Gamma]([Xi]c+ 2![Sigma]-[pi]+[pi]+)/[Gamma]([Xi]c+ 2![Xi]-[pi]+[pi]+) = 0.184 ± 0.086. Systematic studies have been performed in order to check the stability of the measurements varying all cuts used in the selection of events over a wide interval and we do not observe evidence of any trend, so the systematic error is negligible in the final results because the quadrature sum of the total error is not affected. The branching ratios for the same decay modes of the [Lambda]c+ are measured to check the methodology of the analysis. The branching ratio of the decay mode [Lambda]c+ 2![Sigma]+[pi]-[pi]+ is measured relative to [Lambda]c+ 2!pK- [pi]+, while the one of the decay mode [Lambda]c+ 2![Sigma]-[pi]+[pi]+is relative to [Lambda]c+2![Sigma]+[pi]-[pi]+, as they have been reported earlier. The results for the control modes are: [Gamma]([Lambda]c+2![Sigma]+[pi]-[pi]+)/[Gamma]([Lambda]c+ 2!pK- [pi]+) = 0.716 ± 0.144 and [Gamma]([Lambda]c+2![Sigma]-[pi]+[pi]+)/[Gamma]([Lambda]c+ 2![Sigma]+[pi]-[pi]+) = 0.382 ± 0.104. The branching ratio of the decay mode [Xi]c+ 2!pK- [pi]+ relative to [Xi]c+ 2![Xi]-[pi]+[pi]+ is considered as another control mode, the measured value is [Gamma]([Xi]c+ 2!pK-[pi]+)/[Gamma]([Xi]c+ 2![Xi]-[pi]+[pi]+) = 0.194 ± 0.054. Systematic studies have been also performed for the control modes and all systematic variations are also small compared to the statistical error. We also report the first observation of two more decay modes, the Cabibbo-suppressed decay [Xi]c+ 2![Sigma]- K+[pi]+ and the doubly Cabibbo-suppressed decay [Xi]c+ 2![Sigma]+K+[pi]-, but their branching ratios have not been measured up to now.