S. Youssef

Semileptonic decay of the B meson

Abstract Using the CUSB detector we have measured the production of electrons from the decay B→eνX. We obtain a branching ratio for B→eνX of (13.2±0.8±1.4)%. The observed energy spectrum of the electrons implies that the coupling (bc)W dominates over (bu)W. An upper limit Γ( B → e ν X u ) Γ( B → e ν X c ) at 90% confidence level is obtained, where Xc contains a c-quark and Xu contains no charmed particles.

A measurement of the semileptonic decay of B mesons into muons

Abstract We have observed muons from the semileptonic decay B → Xμν where B meson are produced in e+e− annihilations into hadrons at the γ(4S) resonance (10.58 GeV). We obtain a branching ratio of (11.2 ± 0.9 ± 1.0)% for B → Xμν. We have also measured the production of energetic muons in hadronic e+e− annihilations in the energy region above the γ(4S) from 10.6 GeV to 11.2 GeV.

Observation of direct photons in ϒ and ϒ′ decays and determination of the QCD scale parameter

Abstract Using the CUSB detector, we have measured the high energy direct photon spectrum from ϒ and ϒ′ decays. These photons are assumed to arise from the decays ϒ,ϒ′ → γgg. We determine the ration >(gggg/>(ggg) to be 0.0299 ± 0.0059 for the ϒ and 0.0337 ± 0.0114 for the ϒ′. From these results we obtain: αs = 0.226−0.042+0.067, λ MS = 116 −57 +105 MeV for ϒ → γgg, and αS = 0.197−0.055+0.123, λ MS = 80 −59 +195 MeV for ϒ′ → gggg.

Search for Higgs scalars in upsilon decays

Abstract We have searched for the decay of ϒs into a monochromatic photon accompanied by other particles as a signal for the reaction ϒ → γ +Higgs. Two different methods are presented both with null result. While we are not sensitive to the branching ratios predicted by the standard model with a minimal Higgs content, we can put limits on the possible values of the lowest Higgs mass and the ratio of the vacuum expectation values for more complex models. Our results are also of interest with respect to the ξ(2.2) being a Higgs in the context of such models.

A study of hadronic decays of the ϒ

Abstract We present a detailed study of the decays ϒ ′ → π + π − ϒ and ϒ ′ → π 0 π 0 ϒ , where the ϒ decays subsequently to e + e − or μ + μ − . The results are obtained from a sample of 146 000 ϒ′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ϒ ′ → π ′ π − ϒ and (10.3 ± 2.3)% for ϒ ′ → π 0 π 0 ϒ , and determined partial widths for these decays. Invariant mass and angular distributions of both the π + π − and π 0 π 0 systems are presented. We also set a limit on the branching fraction for ϒ ′ → ηϒ of less than 0.2% at the 90% confidence level.

Search for light gluinos

Abstract A study of radiative decays from 400 000 ϒ (9460)s in the partially upgraded CUSB detector is presented. We find evidence against the existence of gluinos of mass 0 6(GeV/ c 2 ) c 2 ) from a search for radiative ϒ (9460) decays into bound states of gluinos.

Observation of χb production in the exclusive reaction ϒ′→γγχb→γγϒ→γγ(e+e−orμ+μ−)

Abstract We report on the observation of 1 3 P J ( χ b ) production in the reaction ϒ ′→ γχ b → γγϒ → γγ (e + e − or μ + μ − ). The data were recorded with the nonmagnetic CUSB detector at the Cornell Electron Storage Ring, CESR. We observe 124 γγ events with either an electron or muon pair in the final state. In the γγ correlation plot about 40% of the events cluster around (120, 430) MeV.

Measurement of the branching ratio for Υ ’ ’ →μμ

Using the CUSB-II detector at the Cornell Electron Storage Ring, we have measured B..mu mu.., the branching fraction into muons, of the UPSILON meson. We find B/sub ..mu..//sub ..mu../(UPSILON) = (1.53 +- 0.33 +- 0.21)%, from which the UPSILON total decay width is 25.5 +- 5.0 keV. From this result we obtain ..cap alpha../sub s/ = 0.170/sub -0.012//sup +0.015/, ..lambda../sub M//sub S-bar/ = 148/sub -39//sup +56/ MeV. (MS-bar denotes the modified minimal-subtraction scheme).

Measurement of the branching ratio forΥ’’→μμ

Using the CUSB-II detector at the Cornell Electron Storage Ring, we have measured B..mu mu.., the branching fraction into muons, of the UPSILON meson. We find B/sub ..mu..//sub ..mu../(UPSILON) = (1.53 +- 0.33 +- 0.21)%, from which the UPSILON total decay width is 25.5 +- 5.0 keV. From this result we obtain ..cap alpha../sub s/ = 0.170/sub -0.012//sup +0.015/, ..lambda../sub M//sub S-bar/ = 148/sub -39//sup +56/ MeV. (MS-bar denotes the modified minimal-subtraction scheme).