Gary J. Feldman

A Unified approach to the classical statistical analysis of small signals

We give a classical confidence belt construction which unifies the treatment of upper confidence limits for null results and two-sided confidence intervals for non-null results. The unified treatment solves a problem (apparently not previously recognized) that the choice of upper limit or two-sided intervals leads to intervals which are not confidence intervals if the choice is based on the data. We apply the construction to two related problems which have recently been a battle-ground between classical and Bayesian statistics: Poisson processes with background, and Gaussian errors with a bounded physical region. In contrast with the usual classical construction for upper limits, our construction avoids unphysical confidence intervals. In contrast with some popular Bayesian intervals, our intervals eliminate conservatism (frequentist coverage greater than the stated confidence) in the Gaussian case and reduce it to a level dictated by discreteness in the Poisson case. We generalize the method in order to apply it to analysis of experiments searching for neutrino oscillations. We show that this technique both gives correct coverage and is powerful, while other classical techniques that have been used by neutrino oscillation search experiments fail one or both of these criteria.

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

Forward Neutron Production at the Fermilab Main Injector

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.

Charged kaon mass measurement using the Cherenkov effect

We have measured cross sections for forward neutron production from a variety of targets using proton beams from the Fermilab Main Injector. Measurements were performed for proton beam momenta of 58, 84, and 120 GeV/c. The cross section dependence on the atomic weight (A) of the targets was found to vary as A{sup {alpha}}, where {alpha} is 0.46{+-}0.06 for a beam momentum of 58 GeV/c and 0.54{+-}0.05 for 120 GeV/c. The cross sections show reasonable agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made with the LAQGSM Monte Carlo.

Inclusive charged hadron and K0 production in two-photon interactions

The two most recent and precise measurements of the charged kaon mass use X-rays from kaonic atoms and report uncertainties of 14 ppm and 22 ppm yet dier from each other by 122 ppm. We describe the possibility of an independent mass measurement using the measurement of Cherenkov light from a narrow-band beam of kaons, pions, and protons. This technique was demonstrated using data taken opportunistically by the Main Injector Particle Production experiment at Fermi National Accelerator Laboratory which recorded beams of protons, kaons, and pions ranging in momentum from +37 GeV/c to +63 GeV/c. The measured value is 491.3 1.7 MeV/c 2 , which is within 1.4 of the world average. An improvement of two orders of magnitude in precision would make this technique useful for resolving the ambiguity in the X-ray data and may be achievable in a dedicated experiment.

SIMULTANEOUS MEASUREMENT OF THE (GAMMA ,P)/(GAMMA ,N) CROSS-SECTION RATIO IN 4HE AS A TEST OF CHARGE SYMMETRY

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.

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

We have measured ([gamma],[ital p]) and ([gamma],[ital n]) differential yields at 90[degree] for the two-body photodisintegration of [sup 4]He using tagged photons of energy [ital E][sub [gamma]]=25--60 MeV. Data for both channels were obtained simultaneously using windowless [Delta][ital E]-[ital E] telescopes to detect the [sup 3]He and [sup 3]H recoils. The ration of our angle-integrated yields, which is insensitive to systematic uncertainies due to the simultaneity of the measurements, agrees with calculations employing only charge-symmetric nuclear interactions. Thus, within the present errors, our data show no evidence of a significant charge-symmetry violation in [sup 4]He in this energy range.

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.

Reaction mechanisms in {sup 12}C({gamma},{ital pp}) near 200 MeV

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.