Measurement of Branching Ratios for Non-leptonic Cabibbo-suppressed Decays of the Charmed-Strange Baryon Ξ_c⁺

Thesis/Dissertation · Fri Aug 01 04:00:00 EDT 2008

DOI:https://doi.org/10.2172/937240· OSTI ID:937240

Vazquez Jauregui, Eric ^[1]

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1. The Autonomous Univ. of San Luis Potosí (Mexico)

We studied several Ξ_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 Σ^-, π^-) 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, Ξ_c⁺ → Σ⁺π^-π⁺ and Ξ_c⁺ → Σ^-π⁺π⁺. The branching ratios of the decays relative to the Cabibbo-favored Ξ_c⁺ → Σ^-π⁺π⁺ are measured to be: Γ(Ξ_c⁺ → Σ^-π⁺π⁺)/Γ(Ξ_c⁺ → Ξ^-π⁺π⁺) = 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 Λ_c⁺ are measured to check the methodology of the analysis. The branching ratio of the decay mode Λ_c⁺ → Σ⁺π^-π⁺ is measured relative to Λ_c⁺ → pK^- π⁺, while the one of the decay mode Λ_c⁺ → Σ^-π⁺π⁺is relative to Λ_c⁺→ Σ⁺π^-π⁺, as they have been reported earlier. The results for the control modes are: Γ(Λ_c⁺→ Σ⁺π^-π⁺)/Γ(Λ_c⁺ → pK^- π⁺) = 0.716 ± 0.144 and Γ(Λ_c⁺→ Σ^-π⁺π⁺)/Γ(Λ_c⁺ → Σ⁺π^-π⁺) = 0.382 ± 0.104. The branching ratio of the decay mode Ξ_c⁺ → pK^- π⁺ relative to Ξ_c⁺ → Ξ^-π⁺π⁺ is considered as another control mode, the measured value is Γ(Ξ_c⁺ → pK^-π⁺)/Γ(Ξ_c⁺ → Ξ^-π⁺π⁺) = 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 Ξ_c⁺ → Σ^- K⁺π⁺ and the doubly Cabibbo-suppressed decay Ξ_c⁺ → Σ⁺K⁺π^-, but their branching ratios have not been measured up to now.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 937240
• Report Number(s): FERMILAB-THESIS--2008-40
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BARYONS
BRANCHING RATIO
CARBON
COPPER
DATA
DECAY
Experiment-HEP
FERMILAB
HYPERONS
QUADRATURES
SPECTROMETERS
STABILITY
TARGETS