- fra (x)
- Robinson, D. K. (x)
- Search results
Search results
Show moreA novel method of analysis which eliminates the combinatorial background in searches for states produced in p¯n annihilations and in association with a recoil π- is presented. The difference between π- and π+ spectra on p¯n annihilations is the spectrum of the recoiling π- or difference spectrum. We applied this analysis to the exclusive channels p¯n→2π-π+, 2π-π+π0, 3π-2π+. A new prominent state of mass and width ≃1480 and 100 MeV/c2 is present in the first and dominates the third channel. These three channels are interpreted in terms of two-body intermediate states only. The suppression or absence of ‘‘direct’’ annihilation is consistent with theoretical models which view the annihilation as a short-range (0.1 fm) phenomenon.
Phys. Rev. Lett. 56, 215–218 (1986)
http://link.aps.org/doi/10.1103/PhysRevLett.56.215
Show less
Show moreInclusive production of Λ and K0 in pp interactions at 12 GeV/c has been studied in an exposure of the Argonne National Laboratory 12-foot bubble chamber to a 50% transversely polarized proton beam. Beam-polarization-induced asymmetries are observed for both K0 and Λ production in the forward direction.
Phys. Rev. D 21, 10–11 (1980)
http://link.aps.org/doi/10.1103/PhysRevD.21.10
Show less
Show moreInclusive charged-pion spectra from p¯d annihilations at rest have been measured in a high-statistics experiment in search of broad states. Analysis of these spectra reveals an enhancement of the π- spectrum at 315 MeV/c. This may be interpreted as a production of a new state of mass 1485 MeV/c2 and width at most 200 MeV/c2 recoiling against the π-. This quasi two-body final state accounts for a large fraction of the p¯n annihilations.
Phys. Rev. Lett. 56, 211–214 (1986)
http://link.aps.org/doi/10.1103/PhysRevLett.56.211
Show less
http://link.aps.org/doi/10.1103/PhysRevLett.10.457
Show moreWe present evidence for the decay A20→ωπ+π0 with a branching ratio Γ(A2→ωππ)/Γ(A2→ρπ)=0.28±0.09 and for the decay ω(1675)→ωπ+π- with a branching ratio Γ(ω(1975)→ωπ+π-)/Γ(ω(1675)→ρπ)=0.47±0.18. Evidence is given for an intermediate B(1235)π state in the ω(1675) decay.
Phys. Rev. Lett. 32, 260–264 (1974)
http://link.aps.org/doi/10.1103/PhysRevLett.32.260
Show less
Show moreWe have studied antiproton elastic scattering on Al, Cu, and Pb for two incident momenta: 514 and 633 MeV/c. The angular region covered extends from the forward Coulomb region to approximately 30 deg. The differential cross sections were analyzed using a nonrelativistic optical potential of the Woods-Saxon form, with the imaginary shape taken from electron scattering data. We obtained fits for the strengths of the real and imaginary parts of the potential, (V0, W0), of (51, 116) MeV for Al, (12, 71) MeV for Cu, and (12, 278) MeV for Pb.
Phys. Rev. C 30, 1080–1083 (1984)
http://link.aps.org/doi/10.1103/PhysRevC.30.1080
Show less
Show moreWe have measured the ratio of the real to the imaginary parts of the p̅ p forward-scattering amplitude in the incident-momentum range 360 to 650 MeV/c. These results are in good agreement with predictions of the Paris nucleon-antinucleon potential model which include spin-flip effects.
Phys. Rev. Lett. 54, 518–521 (1985)
http://link.aps.org/doi/10.1103/PhysRevLett.54.518
Show less
Show moreThe branching ratio for the Λ weak radiative decay has been measured to be B(Λ→n+γ)/(Λ→anything) =[1.78±0.24(stat)±0.160.14(syst)]×10-3. A low-energy kaon beam was used to produce the Λ hyperons via the reaction K-+p→Λ+π0 at rest. Photons from the signal channel and π0 decay were detected with a NaI(Tl) array. The final spectrum contains 287 events after background subtraction, an order of magnitude more events than from the only previous measurement.
Phys. Rev. Lett. 69, 414–417 (1992)
http://link.aps.org/doi/10.1103/PhysRevLett.69.414
Show less
Phys. Rev. Lett. 31, 562–565 (
Show moreWe have observed the decay mode f0→π+π+π-π- and determined the branching ratio Γ(f0→π+π+π-π-)/Γ(f0→π+π-)=(5.5±1.0)×10-2.
Phys. Rev. Lett. 31, 562–565 (1973)
http://link.aps.org/doi/10.1103/PhysRevLett.31.562
Show less
http://link.aps.org/doi/10.1103/PhysRevLett.7.196
Show more3600 two-pronged events, obtained in p-p interactions at 2 Bev in the BNL 20-in. hydrogen bubble chamber, have been analyzed. Cross sections have been measured for elastic scattering, for the two modes of single-pion production, p+p→p+n+π+, p+p→p+p+π0, and for strange-particle production. The branching ratio for the two one-pion production reactions is σ(pnπ+)/σ(ppπ0)=4.17±0.25. Momentum distributions and Q values indicate that single-pion production proceeds almost entirely through the (3/2, 3/2) resonant state. The data have been considered in terms of the extended isobar model and also a one-pion exchange model for production. The branching ratio and momentum distributions can be explained by including a small effect from the I=1/2 resonant state in addition to the dominant I=3/2 resonance. The c.m. angular distribution of the nucleons in single-pion production shows very marked backward-forward peaking indicating a one-pion exchange mechanism. Absolute differential cross sections as a function of laboratory kinetic energy have been calculated from Selleri's equation for the pnπ+ reaction. There is good agreement with the data for low four-momentum transfers [q2<0.15(Bev/c)2], but for higher momentum transfers the theoretical cross sections are larger than the experimental cross sections.
http://link.aps.org/doi/10.1103/PhysRev.125.2082
Phys. Rev. 125, 2082–2090 (1962)
Show less
Show moreThe photon spectrum from K- stopping in liquid hydrogen has been measured with a high-resolution (1.5% FWHM at 300 MeV) NaI(Tl) detector. The branching ratios for K-p→Λγ (Eγ=281.4 MeV) and K-p→Σ0γ (Eγ=219.5 MEV) were obtained. The results are RΛγ=(0.86±0.07-0.08+0.1)×10-3 and RΣ0γ=(1.44±0.20-0.10±0.12)×10-3 where the first error is statistical and the second systematic. These results are not in good agreement with published predictions or with previous Λγ measurements.
Phys. Rev. Lett. 63, 1352–1355 (1989)
http://link.aps.org/doi/10.1103/PhysRevLett.63.1352
Show less
Show moreThe photon spectrum from K-d→Λnγ at rest has been measured for the first time. We obtained the branching ratio, in the end-point region, of (1.89±0.12±0.28)×10-3 where the first error is statistical and the second is systematic. We have found that the shape of the photon energy spectrum is consistent with the distribution calculated by Workman and Fearing with Λn scattering lengths and effective ranges predicted by the Nijmegen group.
Phys. Rev. C 42, R475–R478 (1990)
http://link.aps.org/doi/10.1103/PhysRevC.42.R475
Show less
Show moreResonant structure is studied in the 1.5-to-1.9-GeV mass region of the neutral four-pion system in the reaction π+n→pπ+π+π-π- at 6 GeV/c incident momentum. The ρ0 and A2± content are determined as a function of the four-pion mass. The 4π mass spectrum is best fitted by two resonances, both of which decay predominantly into ρ0π+π-, each with evidence for an appreciable A2π component.
Phys. Rev. D 23, 595–599 (1981)
http://link.aps.org/doi/10.1103/PhysRevD.23.595
Show less
Show moreThe interaction between antiprotons and protons has been studied in the range 1910 to 1990 MeV center-of-mass energy in a drift-chamber experiment at the Brookhaven Alternating Gradient Synchrotron. The total cross section has been determined at eleven different incident momenta, and the elastic cross section between 8 and 30 deg in the laboratory has been measured with an energy resolution of about 5 MeV. The cross section for annihilation into charged mesons has also been measured, with the same resolution. There is no evidence in any of these channels for the existence of a narrow resonance.
Phys. Rev. D 34, 3332–3342 (1986)
http://link.aps.org/doi/10.1103/PhysRevD.34.3332
Show less
Show moreMeson production in π-p and π+n interactions at 1.7 GeV/c has been studied in two bubble-chamber exposures. Combined results are presented with emphasis on single-pion production (4300 events) which is dominated by the formation of the ρ0 meson in peripheral interactions, and on double-pion production (1100 events) which shows strong formation of the ω meson. These data are compared with the predictions of particle-exchange models, including absorption, and the effects of competing channels are discussed. Evidence for a two-pion decay mode of the ω is examined quantitatively. Processes with higher meson multiplicities are described.
Phys. Rev. 157, 1263–1278 (1967)
http://link.aps.org/doi/10.1103/PhysRev.157.1263
Show less
Show moreWe have studied the reaction p↑p→nΔ++ at 6 GeV/c incident momentum in which the incident protons are 60% transversely polarized. The experiment used the Argonne National Laboratory Zero Gradient Synchrotron polarized beam and the 12-foot hydrogen bubble chamber. We report on about 6000 Δ++ events, with the Δ++ produced in the backward hemisphere in the c.m. system. Spin-density matrix elements as a function of momentum transfer are presented and small beam-polarization-induced effects are described.
Phys. Rev. D 20, 596–600 (1979)
http://link.aps.org/doi/10.1103/PhysRevD.20.596
Show less
Show moreAn analysis of the reaction π+n -> wp in a 6.0 GeV/c bubble chamber experiment is presented. The production differential cross section and spin density matrix elements are compared with Regge exchange models.
Physics Letters, Vol. 45B no. 2 (1973) 165-169
Show less
Show moreThe branching ratio for the Λ weak radiative decay Λ→nγ has been measured. Three statistically independent results from the same experiment (Brookhaven E811) are reported here. They are combined with a previously published measurement, also from Brookhaven E811, to yield a result of (Λ→nγ)/(Λ→anything)=(1.75±0.15)×10-3, based on 1800 events after background subtraction. This represents a factor of 75 increase in statistics over the previous world total. A comparison with recent theoretical papers shows that no existing model provides a completely satisfactory description of all data on weak radiative decays. A search is also reported for the radiative capture process K-p→Σ(1385)γ at rest. No signal was observed and an upper limit on the branching ratio of [K-p→Σ(1385)γ]/[K-p→anything] <4×10-4 (90% C.L.) was determined.
Phys. Rev. D 47, 799–810 (1993)
http://link.aps.org/doi/10.1103/PhysRevD.47.799
Show less
Show moreResults on K0 and Λ production in p↑p interactions at 6 GeV are presented. The data are from an exposure of the Argonne 12 ft bubble chamber to a 60% transversely polarized proton beam. Results include data on Λ and K0 inclusive production, and on the reactions p↑p → pΛK+(pΣ0K+). The beam asymmetry parameter for Image is determined to be (−0.52 ± 0.12).
Nucl. Phys. B123 361 (1977)
Show less