A. Baden

Measurement of bottom quark production in 1.8 TeV

We present a measurement of the [ital b]-quark cross section in 1.8 TeV [ital p]-[ital [bar p]] collisions recorded with the Collider Detector at Fermilab using muonic [ital b]-quark decays. In the central rapidity region ([vert bar][ital y][sup [ital b]][vert bar][lt]1.0), the cross section is 295[plus minus]21[plus minus]75 nb (59[plus minus]14[plus minus]15 nb) for [ital p][sub [ital T]][sup [ital b]][gt]21 GeV/[ital c] (29 GeV/[ital c]). Comparisons are made to previous measurements and next-to-leading order QCD calculations.

p\bar{p}

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.

collisions using semileptonic decay muons

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/

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

03.30

Upper limit on B0B0 mixing in e+e- annihilation at 29 GeV

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.

Refined measurement of the B-hadron lifetime

We present a measurement of jet shapes in [ital [bar p]p] collisions at [radical][ital s] =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab (CDF). Qualitative agreement is seen with the predictions of recent next-to-leading [[ital O]([alpha][sub [ital s]][sup 3])] calculations and with leading logarithm QCD based Monte Carlo simulations. The dependence of the jet shape on transverse energy is studied.

Measurement of jet shapes in p-barp collisions at sqrt s =1.8 TeV.

An analysis of {ital W}- and {ital Z}-boson production using data from the Collider Detector at Fermilab at {radical}{ital s} =1.8 TeV yields {sigma}({ital W}{r arrow}{ital ev})/{sigma}({ital Z}{r arrow}{ital ee})=10.2{plus minus}0.8(stat){plus minus}0.4(syst). The width of the {ital W} boson, {Gamma}({ital W}), and a limit on the top-quark mass independent of decay mode are extracted from this measurement.

Measurement of the ratio sigma (W-->e nu )/ sigma (Z-->ee) in p-barp collisions at sqrt s =1.8 TeV.

We present the dijet invariant-mass distribution in the region between 60 and 500 GeV, measured in 1.8-TeV {ital {bar p}p} collisions in the Collider Detector at Fermilab. Jets are restricted to the pseudorapidity interval {vert bar}{eta}{vert bar}{lt}0.7. Data are compared with QCD calculations; axigluons are excluded with 95% confidence in the region 120{lt}{ital M}{sub {ital A}}{lt}210 GeV for axigluon width {Gamma}{sub {ital A}}={ital N}{alpha}{sub s}{ital M}{sub {ital A}}/6, with {ital N}=5.

Two-jet invariant-mass distribution at sqrt s =1.8 TeV.

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.

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

The production rate of charged {ital D}{sup *} mesons in jets has been measured in 1.8-TeV {ital {bar p}p} collisions at the Fermilab Tevatron with the Collider Detector at Fermilab. In a sample of approximately 32 300 jets with a mean transverse energy of 47 GeV obtained from an exposure of 21.1 nb{sup {minus}1}, a signal corresponding to 25.0{plus minus}7.5(stat){plus minus}2.0(syst) {ital D}{sup *{plus minus}}{r arrow}K{sup {minus plus}}{pi}{sup {plus minus}}{pi}{sup {plus minus}} events is seen above background. This corresponds to a ratio {ital N}({ital D}{sup *+}+D{sup *{minus}})/N(jet) =0.10{plus minus}0.03{plus minus}0.03 for {ital D}{sup *} mesons with fractional momentum {ital z} greater than 0.1.