D ∗± production via e + e − → D ∗± X was studied at CM energies near 34 GeV. The charged particles produced in the hemisphere opposite to that of the D ∗ were used to investigate the fragmentation of charm jets. All spectra studied show a close similarity between the charm jet and the average jet obtained by summing over all quark flavours. The spectra of particles produced in the D ∗ hemisphere were used to study separately first rank and higher rank fragmentation.
THE C-JET IS THE JET IN THE HEMISPHERE OPPOSITE TO THAT CONTAINING THE D* MESON. DIVISION IS MADE BY A PLANE PERPENDICULAR TO THE THRUST AXIS.
No description provided.
We report on the exclusive production of π, K and proton pairs from photon-photon interactions at momentum transfers | t |⩾1 GeV 2 . Using the PLUTO detector at the e + e − storage ring PETRA, we have observed 15 events in an integrated luminosity of 41.7 pb −1 . The data lie far below the expectations for point-like hadrons, and are in reasonable agreement with the QCD-based predictions of Brodsky and Lepage.
THIS METHOD OF ANALYSIS OF THE OBSERVED RATIO OF HADRON TO MUON PAIRS, IS TIED TO THE SPECIFIC DETECTOR ACCEPTANCE, BUT HAS THE ADVANTAGE OF BEING VIRTUALLY INDEPENDENT OF THE HADRON MASSES.
SEE COMMENT IN PREVIOUS TABLE.
THIS METHOD OF ANALYSIS OF THE CROSS SECTION AT 90 DEG IN THE CM AS A FUNCTION OF PCM IS MORE EASILY COMPARED WITH THEORETICAL PREDICTIONS BUT MORE DEPENDENT ON THE SPECIFIC HADRON MASSES.
The production of prompt muons ine+e− annihilation has been studied at centre of mass energies near 34.5 GeV. The measured semi-muonic branching ratios ofb andc quarks areB(b»Xμv) =0.117±0.028±0.01 andB(c→Xμv)=0.082 ±0.012a−0.01+0.02. The fragmentation functions of heavy quarks are hard,
THE VALUE OF ASYMMETRY WAS DETERMINED USING A SAMPLE OF PROMPT MUONS.
Inelastic and elastic $J/\psi$ photoproduction on hydrogen are investigated at a mean energy of 105 GeV. The inelastic cross section with $E_{\psi} / E_{\gamma}$ < 0.9 is significantly lower than the corresponding result for muoproduction on iron targets, but is consistent with a second-order perturbative QCD calculation.
No description provided.
We have studied D* production mechanisms using data from a photoproduction experiment at the Fermilab Tagged Photon Spectrometer. A large sample of charged D*’s was selected via the clean signature of the cascade decay D*→D0π+ and subsequently D0→K−π+ or D0→K−π+π0. The cross section for the process γp→(D*++anything)p at an average energy of 105 GeV was measured to be 88±32 nb. Only (11±7)% of D*’s were found to be consistent with being accompanied solely by a D¯* or a D¯; the remaining events contain additional particles. The distribution of the production angle of the D* in the photon-fragmentation-system center of mass is strongly anisotropic and consistent with the form f(θ*)=cos4θ*. We set a limit on the associated-production-process cross section σ(γp→(D¯*−+anything)Λc) x)<60 nb (90% C.L.).
No description provided.
No description provided.
We report measurements made with the CLEO detector at the Cornell Electron Storage Ring (CESR) of the total cross section for e+e−→hadrons at the ϒ(1S), ϒ(2S), and ϒ(3S), and in the nearby nonresonant continuum. We find R=3.77±0.06 (statistical) ± 0.24 (systematic) for the ratio of the nonresonant hadronic cross section to the cross section for muon-pair production at a center-of-mass total energy W=10.4 GeV. For the leptonic decay widths Γee of the ϒ(1S), ϒ(2S), and ϒ(3S) we obtain 1.30±0.05±0.08, 0.52±0.03±0.04, and 0.42±0.04±0.03 keV, respectively.
No description provided.
The interference structure function xG 3 ( x ) has been measured for the first time scattering positive and negative muons of opposite helicity off a carbon target. The x dependence observed for Q 2 between 40 and 180 (GeV/c 2 ) is in good agreement with predictions of the quark-parton model. The measured ratio 2( a u Q u + a d Q d )/( Q u 2 + Q d 2 = 1.87 ± 0.25 (stat.) ± 0.24 (syst.) is consistent with the hypothesis of fractional quark charges and determines the sign of Q u − Q d to be positive.
No description provided.
No description provided.
No description provided.
A study is made of the ωπ 0 system produced near threshold in the reaction γ p→ π + π − π 0 π 0 p. A spin-parity analysis shows that the ωπ 0 enhancement is consistent with predominant 1 + B(1235) production, with ∼20% J P = 1 − background.
MEAN BEAM ENERGY IS 39 GEV.
ESTIMATE OF B(1235) PRODUCTION CROSS SECTION ASSUMING 1+ CROSS SECTION OF 0.63 +- 0.20 MUB AND THAT 20 PCT OF THIS IS DUE TO BACKGROUND S-WAVE CONTRIBUTIONS.
The EM form factor of the pion has been studied in the time-like region by measuring σ (e + e − → π + π − ) normalized to σ (e + e − → μ + μ − ). Results have been obtained for q 2 down to the physical threshold.
No description provided.
The two-jet cross section measured in the UA1 apparatus at the CERN p p Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x 1 and x 2 . The angular distribution d σ /d cos σ rises rapidly as cos → 1, independent of x 2 and x 2 , as expected in vector gluon theories (QCD). The differential cross section in x 1 and x 2 is consistent with factorization and provides a measurement of the proton structure function F(x) = G(x) + 4 9 [Q(x) + Q (x)] at values of the four-momentum transfer squared, -t̂ ≈ 2000 GeV 2 . Over the range x = 0.10−0.80 the structure function shows an exponential x dependence and may be parametrized by the form F ( x ) = 6.2 exp (−9.5 x ).
S(X1,X2) IS DEFINED BY X1*X2*D2(SIG)/DX1/DX2 NORMAISED APPROPRIATELY.
F(X) DEFINED AS G(X)+(4/9)*(Q(X)+QBAR(X)).
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