Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, we have made two measurements of the mixing parameter χ d using kaons as flavour tags. Using D ∗+ K ± correlations we found χ d = 0.20 ± 0.13 ± 0.12 and from the study of (D ∗+ ℓ − ) K ± correlations we obtained χ d = 0.19 ± 0.07 ± 0.09. The branching ratio for B → D ∗+ X has been updated: Br( B → D ∗+ X) = (19.6 ± 1.9) %. We have also determined the average multiplicity of charged kaons in B 0 decays to be 0.78 ± 0.08.
Mixing parameter from counting kaon events. First (...,C=D*+K+-) and second(...,C=(D*+LEPTON-)K+-) value are obtained from a study of D*+K+- and (D*+LEPTO N-)K+- correlations respectively. Second value and the value, reported in Phys.Lett. 324B (1994) 249, were averaged, result third value (...,C=COMBINED) of the mixing parameter in the table (see text for details). In the second value (...,C=(D*+LEPTON-)K+-) the first systematic error is due to the background estimation, the branching ratio for the process B --> K+(K-) X, experimental cuts, and the second one is due to to the uncertainty on the branching ratio for the processes D0 --> K+- X.
No description provided.
We present a direct measurement of Ac=2vcac(vc2+ac2) from the left-right forward-backward asymmetry of D*+ and D+ mesons in Z0 events produced with the longitudinally polarized SLAC Linear Collider beam. These Z0→cc¯ events are tagged on the basis of event kinematics and decay topology from a sample of hadronic Z0 decays recorded by the SLAC Large Detector. We measure Ac0=0.73±0.22(stat)±0.10(syst).
No description provided.
Properties of the hadronic final state in photoproduction events with large transverse energy are studied at the electron-proton collider HERA. Distributions of the transverse energy, jets and underlying event energy are compared to $\overline{p}p$ data and QCD calculations. The comparisons show that the $\gamma p$ events can be consistently described by QCD models including -- in addition to the primary hard scattering process -- interactions between the two beam remnants. The differential jet cross sections $d\sigma/dE_T~{jet}$ and $d\sigma/d\eta~{jet}$ are measured.
No description provided.
Additional overall systematic error of 26 pct.
Additional overall systematic error of 26 pct.
A maximum likelihood analysis of ARGUS data on two-photon production of π + π + π 0 π 0 π − π − is presented. A small fraction of events is due to the production of omega pairs. The γγ → ωω cross section has its maximum value close to threshold.
Results of maximum liklihood analysis.
A measurement of inclusive charged particle distributions in deep inelastic $ep$ scattering for $\gamma~* p$ centre-of-mass energies $75< W < 175$GeV and momentum transfer squared $10< Q~2 < 160$GeV$~2$ from the ZEUS detector at HERA is presented. The differential charged particle rates in the $\gamma~* p$ centre-of-mass system as a function of the scaled longitudinal momentum, $x_F$, and of the transverse momentum, $p_t~*$ and $<\!\!p_t~{*\,2}\!\!>\,\,$ , as a function of $x_F$, $W$ and $Q~2$ are given. Separate distributions are shown for events with (LRG) and without (NRG) a rapidity gap with respect to the proton direction. The data are compared with results from experiments at lower beam energies, with the naive quark parton model and with parton models including perturbative QCD corrections. The comparison shows the importance of the higher order QCD processes. Significant differences of the inclusive charged particle rates between NRG and LRG events at the same $W$ are observed. The value of $<\!\!p_t~{*\,2}\!\!>\,\,$ for LRG events with a hadronic mass $M_X$, which excludes the forward produced baryonic system, is similar to the $<\!\!p_t~{*\,2}\!\!>\,\,$ value observed in fixed target experiments at $W \approx M_X$.
Differential multiplicites for NRG events.. XL is parallel to the virtual photon axis.
Differential multiplicites for NRG events.. PT is relative to the virtual photon axis.
Mean PT**2 for NRG events.. PT is relative to the virtual photon axis.
The Λ b polarization in hadronic Z decays is measured in semileptonic decays from the average energies of the charged lepton and the neutrino. In a data sample of approximately 3 million hadronic Z decays collected by the ALEPH detector at LEP between 1991 and 1994, 462 ± 31 Λ b candidates are selected using ( Λπ + )-lepton correlations. From this event sample, the Λ b polarization is measured to be P Λ b = −0.23 −0.20 +0.24 (stat.) −0.07 +0.08 (syst.).
No description provided.
We have analysed a sample of 2.36 million minimum bias events produced in p p collisions at s =630 GeV in the UA1 experiment at the CERN Sp p S collider. We have studied the production of K S 0 , Λ and Λ particles with transverse momenta ( p t ) up to 7 GeV/c and K ± up to 2 GeV/c. The kaon data are compared with a recent QCD prediction and are found to be in good agreement. The < p t > for K S 0 , Λ and Λ is seen to increase as a function of the charged particle multiplicity and is compared with charged particle production.
No description provided.
K0S Distribution parametrised in the form E*D3SIG/DP**3 = A / (1+ pT/pT0)**N. Best fit values for A, pT0 and N are given here.
No description provided.
Three jet events arising from decays of the Z boson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is $$< r >=1.241 pm 0.015 (stat.)pm 0.025 (syst.).$$ Gluon jets are broader and produce fragments with a softer energy spectrum than quark jets of equivalent energy. The string effect has been observed in fully symmetric three jet events. The measured ratio Rγ of the charged particle flow in the qq̅ inter-jet region of the qq̅g and qq̅γ samples agrees with the perturbative QCD expectation. The dependence of the mean charged multiplicity on the hadronic center-of-mass energy was analysed in photon plus n-jet events. The value for αs(MZ) determined from these data using a QCD prediction with corrections at leading and next-to-leading order is $$←pha_s(M_Z)=0.116pm 0.003 (stat.)pm 03009 (syst.).$$
No description provided.
Durham and JADE algoritms were used.
We have analysed a sample of 2.36 million minimum bias events produced in p p collisions at s =630 GeV in the UA1 experiment at the CERN collider. We have studied the production of charged particles with transverse momenta ( p T ) up to 25 GeV/c. The results are in agreement with QCD predictions. The rise of 〈 p T 〉 with charged particle multiplicity may be related to changing production of low p T particles.
No description provided.
No description provided.
No description provided.
The reaction pd→3Heη has been studied with the SPES2 spectrometer, for proton energies between 0.2 MeV and 11 MeV above threshold. The total cross section rises from 0.25 to 0.40 μb in this region. The observed energy dependence can be attributed to the strong final state interaction. The angular distribution is nearly isotropic, consistent with S wave production. A measurement of the pd→3Heπ+π− cross section in the threshold region is also presented. The setup, which is capable of producing 105 tagged η/s with only a few percent background, is used to investigate rare η decays. © 1996 The American Physical Society.
Threshold energy = 891.37 MeV.
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