The pion electromagnetic form factor has been measured at the VEPP-2M collider in the c.m. energy range 360 MeV–1400 MeV with the detectors OLYA and CMD. On the basis of all available data for the pion form factor collected in the timelike region, the following values for ρ-meson parameters were obtained: m ρ = 775.9 ± 1.1 MeV, σ ρ = 150.5 ± 3.0 MeV. The ω-meson branching ratio into π + π − pair, electromagnetic radius of the pion, ππ scattering length in the P-wave and the strong interaction contribution to the muon ( g − 2) value were found to be B ωππ = (2.3 ± 0.4)%, 〈 r π 2 〉 = 0.422 ± 0.013 fm 2 , a 1 1 = 0.033 ± 0.033m π −3 , a H = (68.4 ± 1.1) × 10 −9 .
Experimental data from the OLYA detector
Experimental data from the CMD detector
We present a measurement of the production of muon pairs in 194 GeV/c π−-tungsten interactions. A sample of 155,000 events with mass higher than 4.07 GeV/c2 has been used to determine the differential cross-section as a function of the scaling variables\(\sqrt \tau\) andxF.
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.21-0.24. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.24-0.27. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.27-0.30. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
We have measured the coherent nuclear production of π+ω systems at 202.5 GeV. This final state is dominated by the B+(1235) meson with a measured mass and full width of 1.271 ± 0.011 GeV and 0.232 ± 0.029 GeV, respectively. A radiative width of 230 ± 60 keV was extracted for the process B+(1235)→π+γ.
DATA REQUESTED FROM THE AUTHORS.
The inclusive process π++P→K¯ *0(890)+X is studied at 16 GeV/c using a 2-m streamer chamber containing a central liquid hydrogen target. From photographs triggered by detection of a forward K− meson, the signal K¯ K−*0π+ is extracted. The inclusive rate for K¯ * production into the forward hemisphere σ(xF>0.3) is 115±27 μb; the pT2 distribution is found to have a slope constant of 3.3±0.6 (GeV/c)2. The Feynman-x distribution for K¯ *0 is consistent with a Kuti-Weisskopf model in which the valence and sea quarks of the incident pion interact with only the sea quarks of the target proton.
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We have measured the K0+K¯ 0 inclusive cross section in e+e− annihilation at 29 GeV with the Mark II detector SLAC PEP. We find 1.27±0.03±0.15 K0+K¯ 0 per hadronic event. We have also used time-of-flight particle identification to measure the K± rate over the momentum range 300–900 MeV/c.
Extrapolated to full momentum range by Monte-Carlo.
Statistical errors only.
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DATA WERE EXTRACTED FROM ADEUT-BREAKUP EVENTS,SEE R=PR D10, 3573 FOR EXAMPLE.
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Using the ARGUS detector at DORIS, we have observed the production of F ± mesons in e + e − annihilation at a centre of mass energy of 10 GeV through their subsequent decays into φπ ± and φπ + π − π ± . The values obtained for [ R (e + e − →FX). Branching Ratio] are (1.47 ± 0.32 ± 0.20)% and (1.63 ± 0.42 ± 0.41)% respectively. The observed mass is (1973.6 ± 2.6 ± 3.0) MeV c 2 . The F momentum spectrum is as expected for the fragmentation of c quarks into charmed mesons, but is somewhat softer than for fragmentation into D ∗ mesons. The relevant angular distributions are consistent with a spin-zero assignment of the F meson.
RESULTS OF FITS FOR SPECIFIED DECAY CHANNELS.
ACCEPTANCE CORRECTED FRAGMENTATION FUNCTION FOR THE TWO DECAY CHANNELS COMBINED. X IS PF/PMAX. DATA HAVE BEEN READ FROM THE GRAPH.