Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

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LIFETIME MEASUREMENT OF CHARM MESONS PRODUCED IN pi- p AND p p INTERACTIONS AT 360-GeV/c

Results are presented on charm meson lifetimes. The sample of charm particle decays was obtained by exposing the high resolution rapid cycling hydrogen bubble chamber (LEBC) coupled with the European Hybrid Spectrometer to \u3c0 12 and p beams at 360 GeV/c from the CERN SPS. The analysis of 3c850 k pictures has yielded 77 events containing a total of 60 charm decays. From these, an unbiased sample of 31 D decays (15\ub1 and 16 D0) is issued in the lifetime analysis. The measured mean lifetimes for D\ub1 and D0 are (where the symbol D0 means D0 and D0):\u3c4(D\ub1)=8.4+3.5 122.2 7 10 1213s\u3c4(D0)=4.1+1.3 120.9 710 1213s. Three unambiguous examples of F\ub1 decay have also been observed and the corresponding lifetime, based on 2 decays, is \u3c4(F\ub1)=2.1 +3.6 120.8 7 10 1213

A SEARCH FOR F PRODUCTION IN 360-GeV/c pi- p INTERACTIONS

We present the results of a search for charm F mesons in 360 GeV/cπ̅p interactions. Several methods have been used; all yield no evidence for the F and are interpreted as 90% confidence level cross section upper limits

Neutral and charged D 17 production in 360 GeV/c \u3c0 12p interactions

The first data on the production of D 17(2010) are presented as observed in \u3c0 12 -proton interactions at 1as = 27 GeV. It is found that D 17(2010) dominates the total charm D-meson production, without a significant non-central component

THE EUROPEAN HYBRID SPECTROMETER

The final version of the European hybrid spectrometer (EHS) is described. EHS was used in the NA27 experiment to study charm particles produced in View the MathML source interactions. A rapid cycling, high resolution bubble chamber (LEBC) produced bubbles of 17 \u3bcm diameter which were measured with a precision of 2.5 \u3bcm. Short-lived charm particles are observed with an efficiency up to 90% (D\ub1). The spectrometer accepts 70% of all particles produced, including approximately 100% of those in the forward hemisphere and the momenta of charged particles are measured to better than 1% over the whole momentum range. The charged particle identification detectors give information on 84% of the spectrometer tracks, half of which obtain unique identification. Two lead glass detectors measure the energy of electromagnetic showers such that the \u3c00 mass distribution has a fwhm of View the MathML source. Hadronic showers are measured with two iron/scintillator calorimeters. The mass resolutions are 3.0, 0.9 and 11 View the MathML source for K0, \u39b0 and D 12 charged particles respectively. The D0 mass is measured to be (1865.1 \ub1 1.8 \ub1 0.8

INCLUSIVE PROPERTIES OF D MESONS PRODUCED IN 360-GeV pi- p INTERACTIONS

The inclusive cross sections for forward D meson production at √s = 26 Gev in π-p interactions have been measured to be: σ(π̅p→D<SUP>0</SUP>/D<SUP>−0</SUP>)X<SUB>F</SUB>&gt;0 = (10.1±2.2) μb, σ(π̅p→D<SUP>±</SUP> + X)X<SUB>F</SUB>&gt;0 = (5.7±1.6) μb . The distribution in X<SUB>F</SUB>for all D and for X<SUB>F</SUB> &gt; 0 has the form dσ/dX<SUB>F</SUB> = 107<SUP>+39</SUP><SUB>-37</SUB>(1-X<SUB>F</SUB>)7.5<SUP>+2.5</SUP><SUB>-1.7</SUB> + 5.4<SUP>+6.0</SUP><SUB>-3.8</SUB>(1-X<SUB>F</SUB>)0.7<SUP>1.0</SUP><SUB>-0.7</SUB>μb, with evidence for leading D production. The P<SUP>2</SUP><SUB>T</SUB> distribution is exponential with slope parameter [−1.18<SUP>+0.18</SUP><SUB>−0.16</SUB>](GeV/c)<SUP>−2</SUP>. The data are compared with predictions from first-order quark/gluon fusion calculations

NEUTRAL D MESON PROPERTIES IN 360-GeV/c pi- p INTERACTIONS

Based on a sample of 22 four-prong D<SUP>0</SUP>/D<SUP>-0</SUP>/ decays produced in hydrogen by 360 GeV/cπ−, we present the following new results: mean lifetime τ = (3.5<SUP>+1.4</SUP><SUB>-0.9</SUB>x 10<SUP>-13</SUP>s; production cross section for x<SUB>F</SUB>&#62; 0.0, σ = (10.3 ± 3.5) ωb; the D → K<SUP>± </SUP>π<SUP>± </SUP>π<SUP>-</SUP>π<SUP>-</SUP>branching ratio = (7.1 ± 2.5)%