W.-Y. Chen

A search for exclusive penguin decays of B mesons

Abstract We have measured upper limits on branching fractions for rare exclusive decays of B mesons arising from one-loop diagrams in the standard model of electroweak interactions. We also obtain an upper limit for the lepton-number-violating decay B 0 → μ ± e ∓ .

Measurement of the isospin mass splitting Ξ+cΞ0c

Abstract Using the CLEO detector, we present a measurement of the mass of the charged charmed strange baryon Ξ + c and its neutral counterpart the Ξ 0 c . The Ξ + c is observed through its decay to Ξ - π + π + , and its mass is measured to be (2467±3±4) MeV. The isospin mass splitting of the Ξ c system is found to be M ( Ξ + c )- M ( Ξ 0 c )=(−5±4±1)MeV.

Determination of B(Ds+) via observation of Ds+l+1/2

Using the CLEO detector at the Cornell Electron Storage Ring (CESR), we have determined the ratio {Gamma}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{ital l}{sup +}{nu})/{Gamma}({ital D}{sub {ital s}}{sup +} {r arrow}{phi}{pi}{sup +})=0.49{plus minus}0.10{sub {minus}0.14}{sup +0.10}. We use this measurement to derive {ital B}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{pi}{sup +}).

Measurement of γγ widths of charmonium states

Abstract Using the CLEO detector at the Cornell Electron Storage Ring, we have searched for two-photon production of charmonium in four-track final states. We have measured Γ γγ ( η c )=5.9 +2.1 −1.8 ±1.9 keV, and we have obtained 95% CL upper limits of Γ γγ ( X c 0 ) Γ γγ ( X c 2 )

First observation of inclusive ψ production in ψ decays

The branching ratio for inclusive ψ production in ψ(1S) decays is measured to be (0.11 ± 0.04 ± 0.02)%.

Measurement of Ds decay modes

Abstract Using the CLEO detector, we have measured the branching ratios for the exclusive decays of the D s + meson into K ∗0 K + , K 0 K + , and K ∗+ K 0 relative to the decay D s + →φπ + to be close to unity. We have also measured the mass diference between the D s + and D + meson to be 98.5±1.5 MeV/ c 2 .

Study of the decays D sup 0 r arrow K K ,. pi. pi

Using the CLEO detector we have observed the Cabibbo-suppressed decays {ital D}{sup 0}{r arrow}{ital K}{sup 0}{ital {bar K}0}, {ital K}{sup +}{ital K}{sup {minus}}, and {pi}{sup +}{pi}{sup {minus}}. We determine {ital B}({ital D}{sup 0}{r arrow}{ital K}{sup 0}{ital {bar K}0})= (0.13{sup +0.07}{sub {minus}0.05}{sup +0.02}{sub {minus}0.02})%. Our measurement {ital B}({ital D}{sup 0}{r arrow}{ital K}{sup +}{ital K}{sup {minus}})/{ital B}({ital D}{sup 0}{r arrow}{pi}{sup +}{pi}{sup {minus}})=2.35{plus minus}0.37{plus minus}0.28 represents asubstantial improvement over previous results. We find no evidence for the decay {ital D}{sup 0}{r arrow}{pi}{sup 0}{pi}{sup 0}, and place a 90%-confidence-level upper limit of {ital B}({ital D}{sup 0}{r arrow}{pi}{sup 0}{pi}{sup 0}){lt}0.46%.

Determination of B ( D sub s sup + r arrow. phi. pi. sup + ) via observation of D sub s sup + r arrow. phi. l sup +. nu

Using the CLEO detector at the Cornell Electron Storage Ring (CESR), we have determined the ratio {Gamma}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{ital l}{sup +}{nu})/{Gamma}({ital D}{sub {ital s}}{sup +} {r arrow}{phi}{pi}{sup +})=0.49{plus minus}0.10{sub {minus}0.14}{sup +0.10}. We use this measurement to derive {ital B}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{pi}{sup +}).

Study of the Decay

Using a sample of 484 000 {ital B} mesons collected with the CLEO detector at the Cornell Electron Storage Ring, we have measured {ital B}({ital {bar B}}{sup 0}{r arrow}D{sup *+}l{sup {minus}}{nu}) and found that the polarization of the {ital D}{sup *+} is small. These results are compared with models of semileptonic {ital B} decay.