R. F. Schwitters

Pion pair production in photon-photon collisions at spear

Abstract We report a measurement of the cross section for the process γγ → π + π − at invariant masses 500 MeV/ c 2 m ππ c 2 . A value for the radiative width of the f(1270) tensor meson Γ f→ γγ = 3.6 ± 0.3 ± 0.5 KeV (helicity λ = 2) has been obtained from a fit to the observed ππ mass spectrum.

Observation of the Decay 00

The prompt photon decay psi(3095)..--> gamma pi../sup +/..pi../sup -/..pi../sup +/..pi../sup -/ has been studied with the Mark II detector at SPEAR. This channel is found to contain a ..gamma..rho/sup 0/rho/sup 0/ component with rho/sup 0/rho/sup 0/ masses concentrated between 1.4 and 2.0 GeV/c/sup 2/. The branching fraction for the psi..--> gamma..rho/sup 0/rho/sup 0/ decay with masses less than 2.0 GeV/c/sup 2/ is measured to be (1.25 +- 0.35 +- 0.40) x 10/sup -3/.The prompt photon decay (3095)+-+- has been studied with the Mark II detector at SPEAR. This channel is found to contain a 00 component with 00 masses concentrated between 1.4 and 2.0 GeV/c2. The branching fraction for the 00 decay with masses less than 2.0 GeV/c2 is measured to be (1.25±0.35±0.40)×10-3.

Limits on strength of neutral currents from e/sup +/e/sup -/. -->. mu. /sup +/. mu. /sup -/

The reaction e/sup +/e/sup -/ ..-->.. ..mu../sup +/..mu../sup -/ has been measured in the center-of-mass energy range 5.8--7.4 GeV. The polar-angle asymmetry agrees with second-order quantum electrodynamics. From this a 95% confidence limit of M/sub z/ > 53g/sub a//e GeV is placed on the mass to coupling constant ratio for a neutral vector boson.

Elementary Particle Physics and the Superconducting Super Collider

The present status and future prospects of elementary particle physics are reviewed, and some of the scientific questions that motivate the construction of a major new accelerator complex in the United States are summarized.

Upper Limit of B0 anti-B0 Mixing in e+ e- Annihilation at 29-GeV

V o l u m e 160B, n u m b e r 1,2,3 PHYSICS LETTERS 3 October 1985 UPPER LIMIT O N B°B ° MIXING IN e + e - ANNIHILATION AT 29 GeV ~ T. SCHAAD, M.E. NELSON 1, G. ABRAMS, D. AMIDEI 2, A.R. BADEN, T. BARKLOW, A.M. BOYARSKI, J. BOYER, M. BREIDENBACH, P.R. BURCHAT, D.L. BURKE, F. BUTLER, J.M. D O R F A N , G.J. FELDMAN, G. GIDAL, L. G L A D N E Y 3, M.S. GOLD, G. GOLDHABER, L. G O L D I N G 4, j. HAGGERTY, G. HANSON, K. HAYES, D. HERRUP, R.J. HOLLEBEEK, W.R. INNES, J.A. JAROS, I. JURICIC, J.A. K A D Y K , D. KARLEN, S.R. KLEIN, A.J. L A N K F O R D , R.R. LARSEN, B.W. LECLAIRE, M. LEVI 5, N.S. LOCKYER 3, V. LIJTH, C. MATTEUZZI 5, R.A. ONG, M.L. PERL, B. RICHTER, K. RILES, M.C. ROSS, P.C. ROWSON, H. SCHELLMAN 2, W.B. SCHMIDKE, R. SCHWITTERS, P.D. SHELDON, G.H. TRILLING, C. DE LA VAISSIERE 6, D.R. WOOD, J.M. YELTON 7 and C. ZAISER Stanford Linear Accelerator Center, Stanford Unwerslty, Stanford, CA 94305, USA Lawrence Berkeley Laboratory and Department of Physws, Umverstty of Cahforma, Berkeley, CA 94720, USA Department of Physws, Harvard Unwerstty, Cambridge, MA 02138, USA Recewed 21 June 1985 The rate of ddepton production m the process e+e - --* hadrons at Vs- = 29 GeV is found to be m good agreement with predictions based on semdeptomc decays of bottom and charm hadrons. We determine that the average probability for a semdeptonlc decay of a hadron lnmally containing a b quark to produce a positive lepton is less than 0 12 at the 90% confidence level and set upper hmlts on B°B ° rmxing. New knowledge of the weak mixing angles, im- posed by the long B lifetime [1,2], a lower bound on the t quark mass [3], and a small ratio [4] of F(b-*u)/ P(b ~ c), has led to predictions that B 0 mesons and, to a much lesser extent, B 0 mesons should exhibit mixing [5,6]. B 0 ~0 mixing can lead to the production of like- sign dileptons in the process e+e - ~ BOBX -> BOBX l This work was supported in part by the Department of Energy, contracts DE-AC03-76SF00515 (SLAC), DE-AC03- 76SF00098 (LBL), and DE-AC02-76ER03064 (Harvard) Present address: California Institute of Technology, Pasadena, CA 91125, USA Present address Umverslty of Chicago, Clucago, IL 60637, USA. Present address University of Pennsylvania, Pluladelptua, PA 19104, USA. Present address Therma-Wave, Inc., Fremont, CA 94539, USA. Present address: CERN, CH-1211 Geneva 23, Switzerland. Present address: LPNHE, Umverslt6 Pierre et M a n e Cune, F-75230 Pans, France Present address Oxford Umverslty, Oxford, England £ - £ - X ,1. Recently, the CLEO collaboration ,2 has reported an upper limit on B0B 0 mixing from the rate of like.sign dileptons produced in the decay of the T(4s). The UA1 collaboration [8] has observed like-sign dimuon events, leading to speculations in the literature [9] that these events could arise from B s 0 - B - 0 s mixing. In this letter, we report a measurement of dflepton rates in e+e - annihilation at an energy above the B 0 production threshold. Here, we always imply the charge conjugate reaction. We use t h e Particle Data Group convention that B (B) hadrons in t h e absence of mixing decay into positive (negative) lep- tons. The t~pes_of neutral B m e s o n s are denoted by B~ = bd and B~ = bs. The CLEO collaboration has set an upper limit on the di- lepton ratio Y n q = ( N n q n q + N~O=O)/N~O~O = N~±/N +- ~a va~a nd~d ndDd The limit set isYB~ < 0.30 at 90% C L under the assump- tion of equal semileptortic branching ratios. Since the B m e s o n s are in an l = 1 state, mixing is suppressed by inter- ference effects (see ref. [12]) a n d Y B ~ = rd, where r d = 0370-2693/85/

Results on two-photon interactions from Mark II at SPEAR

03.30

Total Cross Section for Hadron Production by Electron-Positron Annihilation between 2.4 and 5.0 GeV Center-of-Mass Energy

Two-photon interactions have been studied with the SLAC-LBL Mark II magnetic detector at SPEAR. The cross-section for η′ production by the reaction e+e− → e+e−η′ has been measured over the beam energy range from 2 to 4 GeV. The radiative width Tγγ(η′) has been determined to be 5.8 ± 1.1 keV (±20% systematic uncertainty). Upper limits on the radiative widths of the f(1270), A2(1310), and f′(1515) mesons have been determined. The two-prong final state events show a signal for the f(1270) decaying into η+π− . The current status of this analysis has been discussed.