M. Breidenbach

Study of the decay tau/sup -/. --> pi. /sup -/. pi. /sup -/. pi. /sup +/. nu. /sub tau/

The branching ratios for tau/sup -/..--> pi../sup -/..pi../sup -/..pi../sup +/..nu../sub tau/ and tau/sup -/..--> pi../sup -/..pi../sup -/..pi../sup +/(n..pi../sup 0/)..nu.. /sub tau/, ngreater than or equal to1, have been measured to be 0.078 +- 0.005 +- 0.008 and 0.047 +- 0.005 +- 0.008, respectively. The total three-prong tau branching ratio is 0.128 +- 0.005 +- 0.008. Study of the 3..pi../sup +- /..nu../sub tau/ decay indicates that the three pions are predominantly from a J/sup P/ = 1/sup +/ state which decays through a rho/sup 0/..pi../sup +- / intermediate state in a relative s wave. The rho..pi.. mass spectrum is suggestive of a resonance.

Upper limit on B0B0 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/

Observation of the Decay 00

03.30

THE CASE FOR A 500 GEV E+E- LINEAR COLLIDER

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.

Inclusive production of D-mesons in e+e− annihilation at 7 GeV☆

Several proposals are being developed around the world for an e+e- linear collider with an initial center of mass energy of 500 GeV. In this paper, we will discuss why a project of this type deserves priority as the next major initiative in high energy physics.

Tests of scaling of the proton electromagnetic structure functions

Abstract Inclusive momentum and energy spectra of neutral and charged D-mesons produced in e+e− annihilation at energies near 7 GeV are presented. The slope of the energy spectrum is similar to the charged pion spectrum at the same energy. The inclusive cross section σ(e+e−→ D or D + anything) at 7 GeV is 4.8±1.3 nb.

Measurement of the branching fraction for tau --->5 pi +/-( pi 0) nu tau and an upper limit on the nu tau mass.

Abstract Deep-inelastic structure functions W 1 and W 2 have been extracted from electron-proton scattering cross sections that were measured in recent experiments at SLAC. The structure functions display deviations from scaling in the variable ω in the kinetic range 1.5 ⩽ ω ⩽ 3.0 and 2 ⩽ Q 2 ⩽ 15 GeV 2 .

Some observations on the inelastic electron-nucleon scattering data

The branching fraction for tau/sup -/..-->..5..pi../sup + -/(..pi../sup 0/)..nu../sub tau/ is measured from data accumulated with the Mark II detector at PEP. Four events are observed with an estimated hadronic background of (0.03/sub -0.02//sup +0.04/) events and a background from tau/sup -/..-->..e..pi../sup + -/..pi../sup 0/..nu../sub tau/ of (0.05/sub -0.04//sup +0.07/) events. This results in a measured branching fraction of (0.16 +- 0.08 +- 0.04)%. The candidate events are used to establish an upper limit of 125 MeV/c/sup 2/ on the ..nu../sub tau/ mass at the 95% confidence level.

Variation of the strong coupling constant from a measurement of the jet energy spread in e+e− annihilation

Abstract A compact phenomenological description of the proton data in inelastic electron-nucleon scattering is suggested here. The practical applications of our data analysis are briefly discussed.

The Case for a 500 GeV e+e- Linear Collider

Abstract A measurement of jet energy spread in the reaction e+e− → hadrons is presented. Using a jet calculus model for the jet development we determine the variation of the strong coupling constant with respect to momentum transfer. The observed variation is consistent with that expected for QCD over a wide range of momentum transfers. This method alone is not sufficient to distinguish QCD from simple limited transverse momentum models.