Angular distributions of the differential cross section for the reaction γ +p→ π 0 +p have been measured at the Bonn 2.5 GeV Synchrotron at c.m. angles between 0° and 65° in the energy range from 1.3 GeV to 2.2 GeV. The π 0 mesons were detected by their two decay photons. The data are compared with data of other laboratories and the Metcalf-Walker analysis.
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THE ERRORS INCLUDE THE UNCERTAINTIES IN THE FIT PARAMETERS SLOPE AND SIG, WHILE THE PURELY STATISTICAL ERRORS ARE ALSO GIVEN.
Differential cross sections have been measured at Fermilab with a focusing spectrometer for π±p, K±p, and p±p elastic scattering at 50-, 70-, 100-, 140-, and 175-GeV/c incident momentum over the |t| range 0.03 to 0.8 GeV2. The results are smooth in t and are parametrized by quadratic exponential fits.
DATA PRESENTED AGAIN IN LATER PAPER.
We have studied backward baryon and meson production in π−p→pπ+π−π− at 8.0 GeV/c using a streamer chamber triggered by the detection of a fast forward proton. Our data sample (1227 events) displays prominent N*ρ and N*f quasi-two-body production. These states are investigated with regard to the peripheral nature of the production mechanism and sequential decay of the excited baryon and meson systems. The quasi-two-body production of N*ρ and N*f intermediate states is consistent with u-channel proton exchange as the dominant production mechanism. In the π+π−π− mass distribution we observe a 3- to 4- standard-deviation enhancement at M3π=1897±17 MeV/c2 with full width at half maximum = 110 ± 82 MeV/c2, but find no but find no evidence for backward A1 or A2 production. We observe Δ++(1232) production in the pπ+ effective mass distribution.
THESE VALUES ASSUME ONLY RHO(11) IS NON-ZERO. VALUES FOR OTHER RHO(MM) ARE QUOTED IN PAPER. SIG ERRORS INCLUDE OVER-ALL NORMALIZATION UNCERTAINTY, BUT NO BACKGROUND CORRECTIONS HAVE BEEN MADE.
STATISTICAL ERRORS ONLY, NO BACKGROUND CORRECTION.
STATISTICAL ERRORS ONLY, NO BACKGROUND CORRECTION.
New data from a 600 000 picture exposure of the BNL 31 inch hydrogen bubble chamber to a separated antiproton beam have been analyzed to try to determine if the π + π − π + π − or π + π − π + π − π 0 final states contribute any broad or narrow structure in the T(2190) region. The resonance channel fractions determined by maximum likelihood fits are all consistent with smooth behavior through the T-region and therefore there is no significant evidence that any of these resonance channels contributes to the broad bump in the total cross section. The errors on some of the fractions, however, limit the sensitivity to ∼ 0.5 mb for enhancements in these channels.
RESONANCE CHANNEL PERCENTAGES FROM FIT TO PI+ PI- PI+ PI- FINAL STATE.
RESONANCE CHANNEL PERCENTAGES FROM FIT TO PI+ PI- PI+ PI- PI0 FINAL STATE.
The cross section e + e − → π + π − π o has been measured in the φ energy region and at three other energies (915, 990, 1076 MeV) chosen outside the ω and φ resonances. In the same experiment the energy position and the width of the φ resonance have been determined from the φ →K S o K L o channel. It is found that the magnitude and energy dependence of the experimental cross section are well described by coherent production of ω and φ in the whole energy range 770 to 1076 MeV. Our data clearly show an interference effect which corresponds to an opposite sign between the two products g γω g ω →3 π and g γφ g φ →3 π of the coupling constants.
EXPERIMENTAL CROSS SECTIONS - RADIATIVE CORRECTIONS CAN BE SIGNIFICANT.
The radiative decay models of the φ-meson have been studied: e + e − → φ → ηγ →3 γ ; e + e − → φ → π o γ →3 γ . Cross sections σ φ → ηγ →3 γ and σ φ → π o γ →3 γ have been measured at five energies in the φ-meson energy region and clearly show the φ-resonance in the ηγ → 3 γ mode as well as in the π o γ → 3 γ mode. From a Breit-Wigner fit to the experimental data the values of the branching ratios are deduced: B φ → ηγ = (1.5 ± 0.4) × 10 −2 ; B φ → π o γ = (1.4 ± 0.5) × 10 −3 .
REMOVING RADIATIVE CORRECTIONS, THE PHI PEAK CROSS SECTIONS ARE 66 NB +- 25 PCT <ETA GAMMA> AND 6.5 NB +- 30 PCT <PI0 GAMMA>.
Proton-deuteron elastic scattering has been measured in the four-momentum transfer squared region 0.013<|t|<0.14 (GeV/c)2 and for incident proton beam momenta from 50 to 400 GeV/c. The data can be fitted with the Bethe interference formula. We observe shrinkage of the diffraction cone with increasing energy equal to (0.94±0.04)ln(s1 GeV2) (GeV/c)−2. This shrinkage is greater than that observed in pp elastic scattering. The ratio of the elastic to the total cross section is approximately 0.1 and independent of energy above ∼ 150 GeV. In order to extract information on pn scattering we fit our data using the Glauber approach and a form factor which is the sum of exponentials. The values we obtain for the slope parameter in pn scattering are sensitive to the details of the inelastic double-scattering term.
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The possible existence of new vector mesons above the ρ is investigated. The conclusion is that our data are compatible with the existence of the ρ′-meson only if we assume as a firm theoretical prediction the Gounaris-Sakurai tail of the standard ρ-meson. Furthermore our data are compatible with the existence of the ρ″-meson if we assume the validity of the\(\bar p\)p model for the calculation of the multihadron cross-section.
THESE MEASUREMENTS OF THE PION FORM FACTOR ARE GIVEN IN D. BOLLINI ET AL., NCL 14, 418 (1975).
THESE MEASUREMENTS OF THE FOUR CHARGED PION CROSS SECTION ARE GIVEN IN M. BERNARDINI ET AL., PL 53B, 384 (1974).
THESE MEASUREMENTS OF THE TOTAL HADRONIC CROSS SECTION ARE GIVEN IN M. BERNARDINI ET AL., PL 51B, 200 (1974).
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