The large sample of W→eν events collected by the UA2 experiment at the CERN pp̄ collider between 1988 and 1990 has been used to determine the strong coupling constant α s . From a measurement of the ratio of the production rate of W events with one jet to that with no jets, α s has been extracted to second order in the MS ̄ scheme: α s (M 2 w )=0.123±0.0.18( stat .)±0.017 ( syst .) .
ALP_S extracted to second order in the MSbar scheme.
The analyzing power in inclusive charged pion production has been measured using the 200 GeV Fermilab polarized proton beam. A striking dependence in x F is observed in which A N increases from 0 to 0.42 with increasing x F for the π + data and decreases from 0 to −0.38 with increasing x F for π − data. The kinematic range covered is 0.2⩽ x F ⩽0.9 and 0.2⩽ p T ⩽2.0 GeV / c . In a simple model our data indicate that at large x F the transverse spin of the proton is correlated with that of its quark constituents.
Integrated over all PT.
Integrated over all PT.
No description provided.
Using the CLEO detector at the Cornell Electron Storage Ring, we observe B-meson decays to Λc+ and report on improved measurements of inclusive branching fractions and momentum spectra of other baryons. For the inclusive decay B¯→Λc+X with Λc+→pK−π+, we find that the product branching fraction B(B¯→Λc+X)B(Λc+→pK−π+)=(0.273±0.051±0.039)%. Our measured inclusive branching fractions to noncharmed baryons are B(B→pX)=(8.0±0.5±0.3)%, B(B→ΛX)=(3.8±0.4±0.6)%, and B(B→Ξ−X)=(0.27±0.05±0.04)%. From these rates and studies of baryon-lepton and baryon-antibaryon correlations in B decays, we have estimated the branching fraction B(B¯→Λc+X) to be (6.4±0.8±0.8)%. Combining these results, we calculate B(Λc+→pK−π+) to be (4.3±1.0±0.8)%.
No description provided.
No description provided.
No description provided.
A measurement of the inclusive cross-section for production of direct photons in p̄p collisions at a centre of mass energy of 630 GeV is presented as a function of the photon transverse momentum. The data correspond to a total integrated luminosity of 7.4 pb −1 . The results support predictions from QCD theory.
No description provided.
We present a study of 43 000 3-jet events from Z 0 boson decays. Both the measured jet energy distributions and the event orientation are reproduced by second order QCD. An alternative model with scalar gluons fails to describe the data.
Jets are ordered according their energy: E1 > E2 > E3.
The production of K 0 mesons in e + e − interactions at center of mass energies in the region of the Z 0 mass has been investigated with the OPAL detector at LEP. The rate is found to be 2.10±0.02±0.14 K 0 , Z 0 per hadronic event. The predictions from the JETSET and HERWIG generators agree very well with both the rate and the scale invariant cross section (1/σ had β) (dσ/d x E ) for K 0 production. Comparisons of the inclusive momentum spectrum with predictions of an analytical QCD formula and with data from lower center of mass energies are presented.
No description provided.
No description provided.
K0 multiplicity per hadronic event.
An analysis of the forward-backward asymmetry in Z0 decays using data from the Collider Detector at Fermilab at √s =1.8 TeV yields AFB=[5.2±5.9(stat)±0.4(syst)]% and sin2θ¯W =0.228−0.015+0.017(stat)±0.002(syst).
Asymmetry after background and QCD corrections.
SIN2TW derived from asymmetry measurement fully corrected for background and radiative corrections.
The production rate of final state photons in hadronic Z 0 decays is measured as a function of y cut = M ij 2 / E cm 2 the jet resolution parameter and minimum mass of the photon-jet system. Good agreement with the theoretical expectation from an O( αα s ) matrix element calculation is observed. Comparing the measurement and the prediction for y cut = 0.06, where the experimental systematic and statistical errors and the theoretical uncertainties are small, and combining this measurement with our result for the hadronic width of the Z 0 , we derived partial widths of up and down type quarks to be Γ u = 333 ± 55 ± 72 MeV and Γ d = 358 ± 37 ± 48 MeV in agreement with the standard model expectations. We compare our yield with the QCD shower models including photon radiation. At low γ cut JETSET underestimates the photon yield, and ARIADNE describes the production rate well.
It is assumed that the couplings of various up quarks to be the same.
It is assumed that the couplings of various down type quarks to be the same.
The ratio of the branching fractions for p p →K + K − and p p →π + π − was determined with the CPLEAR detector, by stopping antiprotons in a gaseous hydrogen target at 15 bar pressure. It was found to be BR(K + K − )/BR( π + π − )=0.205± 0.016. The fraction of P-wave annihilation at rest at this target density was deduced to be (38±9)%.
CONST is the fraction of P-wave annihilation in gaseous hydrogen at pressu re of 15 bar. In the SIG/SIG the statistical and systematic errors are added qu adratically.
Using the CLEO II detector at the Cornell Electron Storage Ring, we have determined the inclusive B* cross section above the Υ(4S) resonance in the energy range from 10.61 to 10.70 GeV. We also report a new measurement of the energy of the B*→Bγ transition photon of 46.2±0.3±0.8 MeV.
Hadronic cross section above the continuum. The final state is an unknown mixture of B BBAR + B* BBAR + B B*BAR (+ B* B*BAR only at the highest energy).
Inclusive B* cross section.
Forum