The reaction e+e~e+e m. m has been analyzed using 97 pb ' of data taken with the Crystal Ball detector at the DESY e e+ storage ring DORIS II at beam energies around 5.3 GeV. For the first time we have measured the cross section for yy~m. m. for n m invariant masses ranging from threshold to about 2 GeV. We measure an approximately flat cross section of about 10 nb for 8'=m 0 0 (0.8 GeV, which is below 0.6 GeV, in good agreement with a theoretical prediction 'tr n' based on an unitarized Born-term model. At higher invariant masses we observe formation of the ft(1270) resonance and a hint of the fo(975). We deduce the following two-photon widths: I rr(f, (1270)) =3.19+0. 1620 z, keV and I "(fo( 975)) (0.53 keV at 90% CL. The decayangular distributions show the m~system to be dominantly spin 0 for W &0.7 GeV and spin 2, helicity 2 in the f, (1270) region, with helicity 0 contributing at most 22% (90% C.L.).

Sox8 belongs to a family of transcription regulators characterized by a unique DNA-binding domain known as the high mobility group box. Many Sox proteins play fundamental roles in vertebrate development and differentiation processes. Expression of Sox8 is strong during embryonic muscle development and gradually declines postnatally. In this study, we report that in adult skeletal muscle Sox8 is confined to satellite cells. Downregulation during myogenic differentiation was also detected in cell culture systems and occurred in parallel with down-regulation of the related Sox9. Overexpression of Sox8 or Sox9 on the other hand disrupted myoblasts in their ability to form myotubes. Concomitantly, expression of MyoD and myogenin decreased and basal as well as MyoD-induced activities of the myogenin promoter were strongly reduced in a Sox8-dependent manner. Our data suggest that Sox8 acts as a specific negative regulator of skeletal muscle differentiation, possibly by interfering with the function of myogenic basic helix-loop-helix proteins.

Sox10 belongs to a family of transcription regulators characterized by a DNA-binding domain known as the HMG box. It plays fundamental roles in neural crest development, peripheral gliogenesis, and terminal differentiation of oligodendrocytes. In accord with its function as transcription factor, Sox10 contains two nuclear localization signals and is most frequently detected in the nucleus. In this study, we report that Sox10 is an active nucleocytoplasmic shuttle protein, competent of both entering and exiting the nucleus. We identified a functional Rev-type nuclear export signal within the DNA-binding domain of Sox10. Mutational inactivation of this nuclear export signal or treatment of cells with the CRM1-specific export inhibitor leptomycin B inhibited nuclear export and consequently nucleocytoplasmic shuttling of Sox10. Importantly, the inhibition of the nuclear export of Sox10 led to decreased transactivation of transfected reporters and endogenous target genes, arguing that continuous nucleocytoplasmic shuttling is essential for the function of Sox10. To our knowledge this is the first time that nuclear export has been reported and shown to be functionally relevant for any Sox protein.

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100 and 3000 MeV. Formation of~, g, and g' mesons is observed, and the following meson partial widths are obtained: I 0-7.7+0.5+0.5 eV, I "»-0.514+0.017+0.035 keV, and 'tl I "yy=4. 7+0.5+0.5 keV. No other narrow resonances are observed, and upper limits are given for the product I p yyB& yy. 38 1365 Q~1988 The American Physical Society 1366 D. A. WILLIAMS et al. 38 the range 10 '-10 ' sec which is difficult to measure: they have both a short decay length and a small natural width. The best determinations of the q and g' lifetimes are obtained by using measurements of I & and the branching ratio for X~yy to derive the full width. ' A precise measurement of the m. lifetime using the decaylength technique was recently achieved by Atherton et al. In this paper we describe a study of the reaction e+e~e+e yy~e+e yy, where each y* is a quasireal photon radiated from one of the beam particles. The virtual photons scatter to produce a final state consisting of two real photons. The final-state leptons scatter at very small angles and are not detected. The sum of the transverse momenta of the final-state photons with respect to the beam axis is essentially zero. %e observe three peaks in the invariant-yy-mass spectrum corresponding to the formation of m, g, and g' mesons. This is the first observation of n. production using this technique, first suggested by Low in 1960. The data used for this analysis were collected with the Crystal Ball detector running at the DORIS II e+e storage ring at DESY. The e+e center-of-mass energy varied from 9.4 to 10.6 GeV, with most of the data taken on the Y(1S), Y(2S), and Y(4S) resonances. The sample used for the study of g and g' production has an integrated luminosity of 114 pb ', of which about 40% has

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Using the Crystal Ball detector at the e+e-storage ring DORIS II, we have measured the energy spectrum of direct photons from "f(IS) decays. According to QCD, these photons result from the decays of the "f(IS) resonance into one photon and two gluons, T (1 S)-'l'gg-* T + hadrons. The shape of our spectrum does not agree with that calculated in lowest order QCD, but can be described well by a prediction incorporating gluon self-interaction. Using this fit, the ratio Rv=F('f-,'tgg)/F(F~ggg) is determined to be (2.7+0.2+0.4)%. From this ratio we deduce the strong coupling constant in the MS scheme at Q2=2.2 GeV 2 and find cq= 0.25 + 0.02 + 0.04.

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