The Crystal Ball Collaboration has measured the energy spectrum of electrons from semileptonicB meson decays at thee+e− storage ring DORIS II. Branching ratios and weak mixing angles of the Kobayashi-Maskawa matrix are determined using several models for the hadronic matrix elements. We obtain the branching ratio for semileptonic.B decays to charmed states BR(B→evXc)=(11.7±0.4±1.0)%. Our result for the corresponding Kobayashi-Maskawa matrix element is |Vcb|=0.052±0.006. The model dependence of both results is included in the error. We have not observed semileptonicB decays to non-charmed mesons. Analyzing the measured electron spectrum above 2.4 GeV, where nob→c decays contribute, we find BR(B→evXu)/BR(B→evXc)<6.5% at the 90% confidence level. This corresponds to an upper limit |Vub/Vcb|<0.21.
The errors quoted are statistical only.
The analyzing power AN in inclusive π0 production has been measured with use of the new 185-GeV/c Fermilab polarized proton beam. We obtain the value AN=0.10±0.03 for π0's in the kinematic region 0.2
No description provided.
No description provided.
Individual polarisation measurements.
Inelastic p - 3 He events at 192.8 MeV/ c are detected with a self-shunted streamer chamber. The measured reaction cross section is 392±23.8mb. This result is briefly discussed and compared with other reaction cross sections for low-energy p with light nuclei.
Charged prong multiplicity distribution in annihilation events.
Measured inelastic cross section.
The energy dependence of the relative production rate of three-jet events is studied in hadronic e + e − annihilation events at center of mass energies between 22 and 46.7 GeV. Three-jet events are defined by a jet finding algorithm which is closely related to the definition of resolvable jets used in O( α s 2 ) perturbative QCD calculations, where the relative production rate of three-jet events is roughly proportional to the size of the strong coupling strength. The production rates of three-jet events in the data decrease significantly with increasing centre of mass energy. The experimental rates, which are independent of fragmentation model calculations, can be directly compared to theoretically calculated jet production rates and are in good agreement with the QCD expectations of a running coupling strength. The hypothesis of an energy independent coupling constant can be excluded with a significance of four standard derivations.
No description provided.
No description provided.
No description provided.
The NA 32 experiment at the CERN SPS has collected 38 million hadronic interactions with incident 200 GeV/c π−,K− andp beam. Using a segmented silicon active target and a telescope of high resolution silicon microstrip counters we have selected fully reconstructedD0→K−π+,D0→K−π+π+π−,D+→K−π+π+,Ds+→K−K+π+π+ and charge conjugate decays. The integrated cross-sections forDo,D+D*+ andDs+ meson production and the dependence of the cross-section on longitudinal and transverse momentum of theD are presented.
No description provided.
No description provided.
No description provided.
The effect of isospin-violating, charge-symmetry-breaking (CSB) terms in the np interaction has been observed at TRIUMF by measuring the difference in the zero-crossing angles of the neutron and proton analyzing powers, An and Ap, at a neutron energy of 477 MeV. The scattering asymmetries were measured with a neutron beam incident on a polarizable proton target. To reduce systematic errors, interleaved measurements of An and Ap were made using the same beam and target (apart from their respective polarization states). Neutrons and protons were detected in coincidence in the center-of-mass angle range from 59°–80°. The difference in zero-crossing angles was 0.340°±0.162° (±0.058°), which yields ΔA≡An-Ap=0.0047±0.0022 (±0.0008) using dA/dθc.m.=−0.01382 deg−1. The second errors represent systematic effects. This result is in good agreement with recent theoretical calculations which include CSB effects due to the np mass difference in π, ρ, and 2π exchange, electromagnetic coupling of the neutron anomalous magnetic moment to the proton current, ρ-ω-meson mixing, and short- and medium-range effects of the up- and down-quark mass difference.
No description provided.
We report new results on a precision measurement of the ratio R=σLσT and the structure function F2 for deep-inelastic electron-nucleon scattering in the kinematic range 0.2≤x≤0.5 and 1≤Q2≤10 (GeV/c)2. Our results show, for the first time, a clear falloff of R with increasing Q2. Our R and F2 results are in good agreement with QCD predictions only when corrections for target-mass effects are included.
2.6 pct rad length target.
2.6 pct rad length target.
2.6 pct rad length target.
We report the first observation of an orbitally excited baryon, the Λ(1520), in quark and gluon fragmentation. The production rate is found to be (1.15±0.21±0.16)×10 −2 and (0.80±0.17 −0.13 +0.10 )×10 −2 Λ (1520) hyperons per event in direct ϒ decays and in the continuum, respectively. In contrast to the observed situation for ground state baryons, the production of the Λ(1520) in direct ϒ decays shows little or no enhancement with respect to continuum production.
Full X range uses extrapolation from fit to dsig/dz distribution.
No description provided.
UPSI(1S) DECAYS.
A search for multihadronic events produced with two energetic leptons has been performed at PETRA using 130 pb −1 accumulated by the CELLO detector at 35 GeV ⩽ √ s ⩽46.8 GeV. Three μ + μ − , eleven e + e − and three eμ events were observed. The mesured yields an dthe event characteristics are in good agreement with the expectation for the α 4 QED processes e + e − → ℓ + ℓ − q q and from semileptonic decays of pairs of heavy quarks.
No description provided.
The final states K S 0 K S 0 π + π − and K S 0 K ∓ π 0 π ± , produced in two-photon reactions, have been studied using the ARGUS detector at the e + e − storage ring DORIS II at DESY. The reaction γγ→ K ∗+ K ∗− has been observed for the first time. Its cross section is about eight times larger than that for γγ→ K ∗0 K ∗0 , but it has a similar W γγ dependence.
No description provided.
Topological cross section.
Topological cross section.
Forum