Absolute measurements of the elastic electron-proton cross section have been made with a precision of about 4% for values of the square of the four-momentum transfer, q2, in the range 6.0 to 30.0 F−2 and for electron scattering angles in the range 45° to 145°. To within the experimental errors, it is found that the charge and magnetic form factors of the proton have a common dependence on q2 when normalized to unity at q2=0, and that an accurate representation of the behavior of the form factor and that of the cross sections themselves can be given in terms of a three-pole approximation to the dispersion theory of nucleon form factors.
Axis error includes +- 2./2. contribution (RANDOM ERROR).
Axis error includes +- 2./2. contribution (RANDOM ERROR).
Axis error includes +- 2./2. contribution (RANDOM ERROR).
We present results on the inclusive distributions of final-state hadrons created in deep-inelastic electron scattering from protons and deuterons. Data were taken from all portions of the kinematic range simultaneously in an apparatus which had equal detection efficiency for both charge signs. A subset of the produced hadrons were identified with a threshold-type Čerenkov counter. We find that the charge ratio h+h− is a strong function of Q2, xF, and pT2, with little dependence on s. The ratio of production of h− from deuterium to that from hydrogen as a function of φ is flat. The invariant cross section for each charge sign and each target exhibits the seagull effect (a correlation in 〈pT〉 and 〈xF〉). The value of 〈pT〉 for data in the range 0.4<xF<0.85 increases slightly as Q2 increases. The exponential dropoff in pT for production of protons and kaons is similar to that for pions. The dropoff in xF for production of pions shows a definite dependence on Q2, but this effect is largely caused by the decay products of the exclusive ρ0 final state. Finally, f(xF) for π+, π−, K+, K−, p, and p¯ is presented for each target type.
No description provided.
No description provided.
No description provided.
The inclusive production cross section of ω 0 and η′ were measured at transverse momenta of 3 to 7GeV/ c at 90° in the centre of mass. The ω 0 /π 0 and η′/π 0 production ratios were found to be 0.87 ± 0.17 and 0.9 ± 0.25, respectively, at 3.5 GeV and constant up to 7 GeV/ c . The large meson/ π 0 production ratio supports the hypothesis that high- p T mesons are the leading fragments of the basic constituent jet. The η ′/ η ratio exemplifies the SU(3) singlet nature of the η ′.
OMEGA DECAY TO PI0 GAMMA IS DETECTED.
ETAPRIME DECAY TO GAMMA GAMMA IS DETECTED.
Two-photon interactions have been studied with the SLAC-LBL Mark II magnetic detector at SPEAR. The cross section for η′ production by the reaction e+e−→e+e−η′ has been measured at beam energies from 2.0 to 3.7 GeV. The radiative width Γγγ(η′) has been determined to be 5.8±1.1 keV (±20% systematic uncertainty). Upper limits on the radiative widths of the f(1270), A2(1310), and f′(1515) tensor mesons have been determined. A search has been made for production of the E(1420) by γγ collisions, but no signal is observed.
No description provided.
NO SIGNAL ABOVE BACKGROUND SEEN. UPPER LIMITS AT 95 PCT CL GIVEN.
We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
No description provided.
No description provided.
We report on the first search with virtual photon-photon collisions for narrow, neutral resonances with even C parity in the mass range 4.5<W<19 GeV. The data were obtained via the process e+e−→e+e−γ*γ*→e e−+R with both the scattered e+ and e− detected. We find upper limits (95% confidence level) for the partial decay width of a resonance into two photons, ranging from 50 keV at W=4.5 GeV to 10 MeV at W=19 GeV. These limits constrain theoretical models involving neutral composite bosons.
No description provided.
The photon structure function F 2 has been measured at average Q 2 values of 73,160 and 390 ( GeV c ) 2 . We compare the x dependence of the Q 2 = 73 ( GeV c ) 2 data with theoretical expectations based on QCD. In addition we present results on the Q 2 evolution of the structure function for the intermediate x range (0.3⩽ x ⩽0.8). The results are consistent with QCD.
X dependence at Q**2 = 73 GeV**2 for light quark data.
X dependence at Q**2 = 73 GeV**2 for total data.
Photon structure function F2 for total data.
From 2540 Z 0 → τ + τ − events, we determine the inclusive decay branching fractions of the τ -lepton into one and three charged particles to be 0.856 ± 0.006 (stat.) ± 0.003 (syst.) and 0.144 ± 0.006 (stat.) ± 0.003 (syst.), respectively. The leptonic branching fractions are measured to be 0.175 ± 0.008 (stat.) ± 0.005 (syst.) for τ → μν μ ντ and 0.177 ± 0.007 (stat.) ± 0.006 (syst.) for τ → eν e ν τ . We determined the τ lifetime both from three-prong decays using the decay length and from one-prong decays using the impact parameter. The results from the two independent methods agree and yield a combined value of [0.309 ± 0.023 (stat.) ± 0.030 (syst.)] × 10 −12 s.
ALPHAS extracted from the ratio of the branching fractions.
The inclusive production cross sections of η′ (958) andfo (975) mesons are measured ine+e− annihilation in the nonresonant continuum around\(\sqrt s= 10\) GeV and in decays of the υ resonances using the ARGUS detector. For η′ (958) mesons, a production ratio of η′ (958)/ηdir=0.35±0.24, with ηdir=η−BR(η′→ηX)·η′, is determined in direct υ(1S) decays, which can be partially explained by the pseudoscalar singlet/octet mixing. Forfo(975) production, we obtain a production ratio offo(975)/p(770)°=0.17±0.030 in direct υ(1S) decays. In its production features, thefo(975) behaves like an ordinary meson, though aK\(\bar K\) molecule nature cannot be excluded. The substantial production yield of thefo(975) meson demonstrates the important effect of feeddown from mesons beyond the basic multiples on pseudoscalar and vector meson production.
Direct etaprime rates per event for the continuum region (9.36 to 10.45 GeV), the UPSI(1S) (9.46 GeV), UPSI(2S)(10.02 GeV) and UPSI(4S)(10.58 GeV) regions. Data is extrapolated to the full z region.
Radiation corrected normalized cross section for F0(975) production in the continuum events.
Normalized cross section for F0(975) production in direct UPSI(1S) decays.
Cross sections are presented for the inclusive production of charged particles measured in electron-proton collisions at low Q 2 with the H1 detector at HERA. The transverse momentum distribution extends up to 8 GeV/ c . Its shape is found to be harder than that observed in p p collisions at comparable centre-of-mass energies √S γp ≈ √S p p ≈ 200 GeV , and also harder than in γp collisions at lower energies √ S γp ≈ 18 GeV. Results from quantum chromodynamics (QCD) calculations agree with the measured transverse momentum and pseudorapidity cross sections.
No description provided.
No description provided.
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