D. L. Burke

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/

Refined measurement of the B-hadron lifetime

03.30

Inclusive charged hadron and K0 production in two-photon interactions

We report a new measurement of the average lifetime of hadrons containing bottom quarks. The B hadron decays are tagged by identifying leptons at high transverse momentum. From a fit to the lepton impact parameter distribution, the average B hadron lifetime is found to be (0.98 f 0.12 f 0.13) x lo-l2 sec. The lifetime of hadrons containing bottom quarks is a measure of the strength of the weak transitions between the bottom quark and the charm and up quarks. In terms of the 3 x 3 quark mixing matrix proposed by Kobayashi and Maskawaf the B hadron lifetime depends on the magnitude of the matrix elements Vub and &b. Studies of B semileptonic decay’ have shown that Iv&l is small compared to I&l, and therefore the B lifetime essentially measures II&l and limits lvUbl. The data used in this measurement were collected with the Mark II detector at the e+estorage ring PEP (EC, = 29 GeV). We have previously reported a B lifetime measurement3 based on a data sample of 80 pb-l. The present work: based on a data sample of 204 pb-l, includes the previous data and supersedes our earlier analysis. We use the same procedure of measuring the impact parameters of leptons produced in B decay. However, we have improved upon the previous result through direct measurement of the experimental resolution function, a more precise determination of the B production point, and a comprehensive analysis of inclusive lepton production. These improvements combined with the increased statistics make this measurement of the B lifetime the most precise from any experiment to date. The Mark II detector has been described in detail elsewhere.5 A high resolution drift chamber, known as the vertex chamber, is situated inside the main tracking chamber. The two drift chambers are immersed in a solenoidal magnetic field of 2.3 kG. Particle trajectories are measured with high precision in the (2, y) plane perpendicular to th e b earns, and the impact parameter is accurately determined in that plane. Electrons are identified over 64 % of the solid angle with a lead-liquid-argon calorimeter. Muons are identified over 44 % of the solid angle by-a system of hadron absorbers and proportional tubes.

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

Abstract The inclusive transverse momentum distributions of charged hadrons and K 0 s produced in tagged photon-photon collisions, are measured and compared to model calculations up to a p T of 5 GeV/ c . The relative abundance of K 0 s favor the inclusion of charm.

Upper limit on the branching ratio for the decay τ-→Π-ηvτ

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.

Limit on the decay D0e

We have searched for the decay τ-→Π-ηvτ using the MARK II detector at the PEP e+e- storage ring. No evidence for the decay is found; the upper limit for the branching ratio is B(τ-→Π-ηvτ)<1.0% at the 95% confidence level.

Measurement of the branching fraction for -5(0) and an upper limit on the mass

We have searched for the lepton-flavor-violating decay D/sup 0/..-->..e/sup +- /..mu../sup minus-or-plus/ in 204 pb/sup -1/ of e/sup +/e/sup -/ annihilation data at E/sub c.m./ = 29 GeV from the Mark II detector. No candidates were found; we estimate an upper limit on the cross section times branching ratio of sigma(e/sup +/e/sup -/..-->..D/sup 0/,D-bar/sup 0/; inclusive)B(D/sup 0/..-->..e/sup +- /..mu../sup minus-or-plus/) ..e/sup +- /..mu../sup minus-or-plus/)<2.1 x 10/sup -3/. AE.

Limits on J ψ and Υ{hooked} production in e+e-interactions at s = 29 GeV

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.

Limits on Jψ and ϒ production in e+e− interactions at s = 29 GeV

A search has been made for the inclusive production of Jψ (3.1) and ϒ (9.4) mesons in e+e− interactions at 29 GeV, via their decay into two leptons. No signal is observed in the Jψ region, nor in the ϒ region. The limits on the cross sections are σ(e+e− → ψX) < 4.4 × 10−36cm2, and σ(e+e− → ϒX) < 4.7 × 10−36 cm2. The same data yield limits on the branching ratios for the b quark BR (b → ψX) < 4.9% and BR (b → l+l−X) < 0.8%.Volume 129, number 1,2 PHYSICS LETTERS 15 September 1983 LIMITS ON J / ~ A N D T PRODUCTION IN e+e - INTERACTIONS AT X/s= 29 GeV ~ C. MATTEUZZI, G.S. ABRAMS, D. AMIDEI, C.A. BLOCKER, A.M. BOYARSKI, M. BREIDENBACH, D.L. BURKE, W. CHINOWSKY, W.E. D1ETERLE 1, J.B. DILLON, J.M. DORFAN, M.W. EATON, G.J. FELDMAN, M.E.B. FRANKLIN, G. GIDAL, L. GLADNEY, M.S. GOLD, G. GOLDHABER, L.J. GOLDING, G. HANSON, R.J. HOLLEBEEK, W.R. INNES, J.A. JAROS, A.D. JOHNSON, J.A. KADYK, A.J. LANKFORD, R.R. LARSEN, B. LeCLAIRE, M. LEVI, N. LOCKYER, V. LI]TH, M.E. NELSON, J.F. PATRICK 2, M.L. PERL, B. RICHTER, P.C. ROWSON, T. SCHAAD, H. SCHELLMAN, D. SCHLATTER, R.F. SCHWITTERS, P.D. SHELDON, J. STRAIT 3, G.H. TRILLING, C. de la VAISSIERE, J.M. YELTON and C. ZAISER Stanford Linear Accelerator Center, Stanford UniversiO,, Stanford, CA 94305, USA Lawrence Berkeley Laboratory and Department o f Physies, University of California, Berkeley. CA 94720, USA Department o f Physics, Harvard University, Cambridge, MA 02138, USA Received 29 April 1983 A search has been made for the inclusive production of J/¢, (3.1) and T (9.4) mesons in e+e - interactions at 29 GeV, via their decay into two leptons. No signal is observed in the J/O region, nor in the r region. The limits on the cross sec- tions are o (e+e - ~ ~X) 15 GeV. Very high statistics experiments are needed in order to check these calculations and to identify the differ- ent mechanisms which are involved. The perturbative calculations are however the minimal expected con- tribution to

Measurement of the lifetime of bottom hadrons

inclusive production: a large uncer- tainty comes from possible non-perturbative contribu- tions. Some calculations [3] predict a cross section larger than 10 -1 ouu , which would imply a large prob- ability to observe