ΛΛˉ\Lambda\bar{\Lambda} Production in Two-Photon Interactions at CLEO

Using the CLEO detector at the Cornell $e^+e^-$ storage ring, CESR, we study the two-photon production of $\Lambda \bar{\Lambda}$, making the first observation of $\gamma \gamma \to \Lambda \bar{\Lambda}$. We present the cross-section for $\gamma \gamma \to \Lambda \bar{\Lambda}$ as a function of the $\gamma \gamma$ center of mass energy and compare it to that predicted by the quark-diquark model.Comment: 10 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLN

Study of gluon versus quark fragmentation in Y → ggγ and e+e- → qq̄γ events at √s=10 GeV

Using data collected with the CLEO II detector at the Cornell Electron Storage Ring, we determine the ratio Rchrg for the mean charged multiplicity observed in Y(1S)→ggγ events, 〈n±gluon〉, to the mean charged multiplicity observed in e+e-→qq̄γ events, 〈n±quark〉. We find Rchrg≡〈n±gluon〉/〈n±quark〉=1.04 ±0.02(stat)±0.05(syst) for jet-jet masses less than 7 GeV

Experimental tests of lepton universality in tau decay (vol 55 D, pg 2559, 1997)

The branching fractions for τ→eνντ, μνντ, and hντ are measured using data collected with the CLEO detector at the CESR e+e- collider: Be=0.1776±0.0006±0.0017, Bμ=0.1737±0.0008±0.0018, and Bh=0.1152±0.0005±0.0012, where the first error is statistical, the second systematic, and h refers to either a charged π or K. Also measured is the τ mass, mτ=(1778.2±1.4) MeV. Lepton universality is affirmed by the relative branching fractions (Bμ/Be=0.9777±0.0063±0.0087, Bh/Be=0.6484±0.0041±0.0060) and the charged-current gauge coupling-constant ratios (gμ/ge=1.0026±0.0055, gτ/gμ=0.9990±0.0098). The τ mass result may be recast as a τ neutrino mass limit, mντ<60 MeV at 95% C.L

Search for neutrinoless τ decays: τ→e γ and τ→μ γ

A search for the lepton-family-number-violating decays gt;ey and has been performed using II data. Nr&gt; p.virlenrp nf a sipnal ha&lt;; hppn fnnnH anH thp. mrrp.snnnHincr nnnpr limit; are (T-ey)&lt;2.7× 10-6 and B(T-&gt;r)&lt;3.0X IQ-6 at 90% C.L. © 1997 The American Physical Society