D. K. Robinson

A study of inclusive vector meson production

Abstract Data are presented on the reactions π + n → ϱ 0 +X and K − p → K ∗ 0 (890)+ X at 6.0 and 7.3 GeV /c , respectively. Comparisons are made with related reactions at higher energies.

["Measurement of the Λ→n+γ branching ratio"]

The branching ratio for the {Lambda} weak radiative decay has been measured to be {ital B}({Lambda}{r arrow}{ital n}+{gamma})/({Lambda}{r arrow}anything) =(1.78{plus minus}0.24(stat){plus minus}{sub 0.16}{sup 0.14}(syst)){times}10{sup {minus}3}. A low-energy kaon beam was used to produce the {Lambda} hyperons via the reaction {ital K}{sup {minus}}+{ital p}{r arrow}{Lambda}+{pi}{sup 0} at rest. Photons from the signal channel and {pi}{sup 0} 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.

Measurement of the. Lambda. r arrow n +. gamma. branching ratio

The branching ratio for the {Lambda} weak radiative decay has been measured to be {ital B}({Lambda}{r arrow}{ital n}+{gamma})/({Lambda}{r arrow}anything) =(1.78{plus minus}0.24(stat){plus minus}{sub 0.16}{sup 0.14}(syst)){times}10{sup {minus}3}. A low-energy kaon beam was used to produce the {Lambda} hyperons via the reaction {ital K}{sup {minus}}+{ital p}{r arrow}{Lambda}+{pi}{sup 0} at rest. Photons from the signal channel and {pi}{sup 0} 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.

π − p → π 0 π 0 n near threshold and chiral symmetry breaking

Total cross sections, angular, and mass distributions for the reaction {pi}{sup {minus}}{ital p}{r arrow}{pi}{sup 0}{pi}{sup 0}{ital n} have been measured for {ital p}{sub {pi}}{sup {minus}}(lab)=7--140 MeV/{ital c} above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, {xi}, of {minus}0.98{plus minus}0.52. The {pi}{pi} scattering lengths {ital a}{sub {ital I}} for isospin {ital I}=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are {ital a}{sub 0}=(0.207{plus minus}0.028){ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub 2}=({minus}0.022{plus minus}0.011){ital m}{sub {pi}}{sup {minus}1}. These values are consistent with chiral symmetry broken by the Weinberg {pi}{pi} interaction and the effects of the {ital f}{sub 0}(975) scalar meson.

["π-p→π0π0n near threshold and chiral symmetry breaking"]

Total cross sections, angular, and mass distributions for the reaction {pi}{sup {minus}}{ital p}{r arrow}{pi}{sup 0}{pi}{sup 0}{ital n} have been measured for {ital p}{sub {pi}}{sup {minus}}(lab)=7--140 MeV/{ital c} above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, {xi}, of {minus}0.98{plus minus}0.52. The {pi}{pi} scattering lengths {ital a}{sub {ital I}} for isospin {ital I}=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are {ital a}{sub 0}=(0.207{plus minus}0.028){ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub 2}=({minus}0.022{plus minus}0.011){ital m}{sub {pi}}{sup {minus}1}. These values are consistent with chiral symmetry broken by the Weinberg {pi}{pi} interaction and the effects of the {ital f}{sub 0}(975) scalar meson.

π−p→π0π0nnear threshold and chiral symmetry breaking

Total cross sections, angular, and mass distributions for the reaction {pi}{sup {minus}}{ital p}{r arrow}{pi}{sup 0}{pi}{sup 0}{ital n} have been measured for {ital p}{sub {pi}}{sup {minus}}(lab)=7--140 MeV/{ital c} above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, {xi}, of {minus}0.98{plus minus}0.52. The {pi}{pi} scattering lengths {ital a}{sub {ital I}} for isospin {ital I}=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are {ital a}{sub 0}=(0.207{plus minus}0.028){ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub 2}=({minus}0.022{plus minus}0.011){ital m}{sub {pi}}{sup {minus}1}. These values are consistent with chiral symmetry broken by the Weinberg {pi}{pi} interaction and the effects of the {ital f}{sub 0}(975) scalar meson.

pi. sup minus p r arrow. pi. sup 0. pi. sup 0 n near threshold and chiral symmetry breaking

Total cross sections, angular, and mass distributions for the reaction {pi}{sup {minus}}{ital p}{r arrow}{pi}{sup 0}{pi}{sup 0}{ital n} have been measured for {ital p}{sub {pi}}{sup {minus}}(lab)=7--140 MeV/{ital c} above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, {xi}, of {minus}0.98{plus minus}0.52. The {pi}{pi} scattering lengths {ital a}{sub {ital I}} for isospin {ital I}=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are {ital a}{sub 0}=(0.207{plus minus}0.028){ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub 2}=({minus}0.022{plus minus}0.011){ital m}{sub {pi}}{sup {minus}1}. These values are consistent with chiral symmetry broken by the Weinberg {pi}{pi} interaction and the effects of the {ital f}{sub 0}(975) scalar meson.

pi- p ---> pi0 pi0 n near threshold and chiral symmetry breaking

Total cross sections, angular, and mass distributions for the reaction {pi}{sup {minus}}{ital p}{r arrow}{pi}{sup 0}{pi}{sup 0}{ital n} have been measured for {ital p}{sub {pi}}{sup {minus}}(lab)=7--140 MeV/{ital c} above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, {xi}, of {minus}0.98{plus minus}0.52. The {pi}{pi} scattering lengths {ital a}{sub {ital I}} for isospin {ital I}=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are {ital a}{sub 0}=(0.207{plus minus}0.028){ital m}{sub {pi}}{sup {minus}1} and {ital a}{sub 2}=({minus}0.022{plus minus}0.011){ital m}{sub {pi}}{sup {minus}1}. These values are consistent with chiral symmetry broken by the Weinberg {pi}{pi} interaction and the effects of the {ital f}{sub 0}(975) scalar meson.

Radiative kaon capture

Negative kaons were stopped in liquid hydrogen and liquid deuterium targets to study radiative capture rates. Branching ratios for the radiative kaon capture reactions K−p→Λγ and K−p→Σ0γ provide information about the quark structure of the Λ(1405). In the reaction K−d→Λnγ, the shape of the photon spectrum in the endpoint region provides information on the final state Λ‐n interaction. Superior photon resolution is needed to distinguish the signal photons from the background of π0 decay photons. Such resolution is provided by the B.U. NaI detector, which has a resolution of 1.3% (FWHM) near 300 MeV. A description of the experimental technique and data reduction is presented, along with preliminary branching ratio results.

Low energy antiproton interaction studies at Brookhaven

Results on antiproton quasielastic scattering on Al, Cu and Pb for two incident momenta 514 and 633 MeV/c are presented. Differential cross sections for these reactions were combined with other published data and analyzed with a nonrelativistic optical model. Absorption cross section results from our experiment are in good agreement with predictions from our optical model fits. Preliminary results are presented from p elastic scattering on hydrogen for the forward angular region in the momentum range from 360 to 652 MeV/c. We obtain small values of the ratio of the real to imaginary part of the forward scattering amplitude in this momentum interval.