Publications (15)6.62 Total impact
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Article: Precision Pion-Proton Elastic Differential Cross Sections at Energies Spanning the Delta Resonance
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ABSTRACT: A precision measurement of absolute pi+p and pi-p elastic differential cross sections at incident pion laboratory kinetic energies from T_pi= 141.15 to 267.3 MeV is described. Data were obtained detecting the scattered pion and recoil proton in coincidence at 12 laboratory pion angles from 55 to 155 degrees for pi+p, and six angles from 60 to 155 degrees for pi-p. Single arm measurements were also obtained for pi+p energies up to 218.1 MeV, with the scattered pi+ detected at six angles from 20 to 70 degrees. A flat-walled, super-cooled liquid hydrogen target as well as solid CH2 targets were used. The data are characterized by small uncertainties, ~1-2% statistical and ~1-1.5% normalization. The reliability of the cross section results was ensured by carrying out the measurements under a variety of experimental conditions to identify and quantify the sources of instrumental uncertainty. Our lowest and highest energy data are consistent with overlapping results from TRIUMF and LAMPF. In general, the Virginia Polytechnic Institute SM95 partial wave analysis solution describes our data well, but the older Karlsruhe-Helsinki PWA solution KH80 does not. Comment: 39 pages, 22 figures (some with quality reduced to satisfy ArXiv requirements. Contact M.M. Pavan for originals). Submitted to Physical Review C03/2001; -
Article: Study of Two-Step Mechanisms in Pion Absorption on 6Li, 12C via Deuteron Emission
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ABSTRACT: The (pi+,pd), and (pi+,dd) reactions were investigated with pions of 100 and 165 MeV kinetic energy on 6Li and 12C targets. In comparison with previously published (pi+,pp) data on the same targets and at the same beam energies, kinematic regions were identified in which the neutron pickup process n+p->d dominated the observed deuteron yield. The importance of this mechanism increases with energy, contributing half of the observed cross section at 165 MeV. The contribution of direct quasi-triton absorption is significant only at 100 MeV. Comment: 23 pages, 12 figures09/2000; -
Article: Determination of the π+/-p-->π+/-π+n cross section near threshold
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ABSTRACT: The total cross section for the π-p-->π-π+n reaction has been measured at incident pion kinetic energies of 200, 190, 184, 180, and 176 MeV, and cross sections for the π+p-->π+π+n reaction were obtained at 200 and 184 MeV. A fit of these cross sections by heavy baryon chiral perturbation theory yields values of 8.5+/-0.6(m-3π) and 2.5+/-0.1(m-3π) for the reaction matrix elements A10 and A32, and, for the s-wave isospin-0 and isospin-2 π-π scattering lengths, the values a0=0.23+/-0.08(m-1π) and a2=-0.031+/-0.008(m-1π), respectively.Physical Review C 01/2000; 61(2):25201. · 3.31 Impact Factor -
Conference Proceeding: Energy dependence of T/sub 20/ and tau/sub 21/ in. pi. d-italic-arrow-right elastic scattering
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ABSTRACT: Angular distributions of the tensor analyzing powers T/sub 20/ and tau/sub 21/ have been measured for ..pi..d-italic-arrow-right elastic scattering, in a single scattering experiment employing a tensor polarized deuteron target. Measurements of T/sub 20/ were obtained for pion bombarding energies of 134, 151, 180, 220, and 256 MeV. Measurements of tau/sub 21/ were obtained for pion bombarding energies of 134, 180, and 220 MeV. The results are compared with three-body calculations where effects relating to pion absorption are seen to play an important role.11/1988 -
Article: Measurement of the tensor analyzing power T21in πd elastic scattering
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ABSTRACT: The first measurements of the tensor analyzing power T21 in the πd elastic scattering reaction have been made using a tensor polarized deuteron target. Eleven angles were studied at a pion bombarding energy of 180 MeV. The results are shown to be in agreement with Faddeev calculations.Physical Review C 05/1987; 35:2343-2346. · 3.31 Impact Factor -
Article: Differential cross section and analyzing power for backward pions in 2H(p, π+)3H
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ABSTRACT: Cross sections and analyzing powers are presented for the reaction at 400, 425, 443 and 470 MeV, and laboratory pion angles of 120°, 130°, 140°, 150° and 160°. The cross sections have flat angular distributions, are in contradiction with an earlier experiment which indicated a backward peak at 470 MeV, but are in quantitative agreement with a calculation based on the two-nucleon model.Physics Letters B. -
Article: Analyzing power of the p [over→] p→ π^{+} d reaction at 375, 450, and 500 MeV incident proton energies
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ABSTRACT: The analyzing power AN0 of the p⃗p→π+d reaction was measured to a statistical precision of better than ±0.01 at incident proton beam energies of 375, 450, and 500 MeV, for center-of-mass angles from 20° to 150°. The polarization-dependent differential cross sections were fitted by associated Legendre functions (using published data for the shapes of the unpolarized differential cross sections). The energy dependence of the resulting bkN0 coefficients were compared with existing data and theoretical expectations.NUCLEAR REACTIONS p⃗p→π+d; polarized protons; E=375, 450, 500 MeV; measured AN0(E, θ); θ=20-150° c.m.; deduced b1N0(E)-b5N0(E).Phys. Rev. C. 28(6). -
Article: Search for deeply bound pionic states in^{208} Pb via radiative atomic capture of negative pions
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ABSTRACT: A search for narrow, deeply bound pionic atom states via atomic radiative capture of negative pions in a target of 208Pb was carried out for pion kinetic energies of 20 and 25 MeV. Although no clear signature of any such gamma ray emission could be observed in the data, fits of the gamma ray spectra between the energies of 12 and 42 MeV involving a quadratic background together with a pair of peaks (1s, 2p) whose relative intensity was taken from theory yielded an overall strength for the peaks which are consistent (to a 67% confidence level) with radiative capture whose integrated cross section is 20.0 ± 10.0 μb/sr at 90° for 20 MeV incident pions. A lower probability (40% confidence level) result was obtained when the fit was carried out without the peaks included, just the continuum background.Phys. Rev. C. 55(5). -
Article: Energy dependence of T_ {20} and τ_ {21} in πd→ elastic scattering
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ABSTRACT: Angular distributions of the tensor analyzing powers T20 and τ21 have been measured for πd elastic scattering, in a single scattering experiment employing a tensor polarized deuteron target. Measurements of T20 were obtained for pion bombarding energies of 134, 151, 180, 220, and 256 MeV. Measurements of τ21 were obtained for pion bombarding energies of 134, 180, and 220 MeV. The results are compared with three-body calculations where effects relating to pion absorption are seen to play an important role.Phys. Rev. C. 38(1). -
Article: Spin-transfer measurements of the πd→→ p→ p reaction at energies spanning the Δ resonance
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ABSTRACT: The first spin-transfer experiment performed for the πd→→p→p reaction is described. Three spin-transfer parameters for this π-absorption process were determined, KLSa, KSSa, and KNNa, which correspond to the π-production parameters, KSLp, KSSp, and KNNp, of the time-reversed p→p→d→π process. Each observable was measured at a single angle for a number of energies spanning the Δ resonance of this system. The results are compared with the predictions of published partial wave amplitude fits which are primarily based on existing data for the time-reversed pp→dπ reaction, and also with the predictions of two current theories. The failure of these theories to describe the fundamental features of the data clearly demonstrates the need for further theoretical work in this area.Phys. Rev. C. 55(1). -
Article: Measurements of cross sections and analyzing powers for the inclusive pp→ pnπ^{+} reaction at 400 and 450 MeV
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ABSTRACT: Single arm spectrometer measurements of the differential cross sections and analyzing powers of the pp→pnπ+ reaction have been performed at 400 and 450 MeV incident proton energy. The measurements covering an angular range from 46° to 90° (lab) spanned pion energies corresponding to production of the np system with relative energies between 0 and 30 MeV, a region where the influence of the np final state interaction is particularly important. The trend of the measured analyzing power is very similar to that of the pp→dπ+ reaction, and is well explained by calculations that use this latter data as input. Dominance of the triplet pn final state is implied by these results.Phys. Rev. C. 32(6). -
Article: Pion production from hydrogen bombarded by polarized protons at intermediate energies
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ABSTRACT: Angular distributions of differential cross sections and polarization analyzing powers are presented for the reaction for incident proton energies between 305 and 425 MeV. The pions were detected in a single-arm configuration employing a magnetic spectrograph. Pions associated with both bound (deuteron) and unbound final nucleon states were detected simultaneously. These data provide the first indication of the contribution of d-wave pions in this energy region. Some data concerning the analyzing power for the inclusive pions from the reaction are also presented. An interesting feature of these results is the similarity of the analyzing power for the reaction (when the relative kinetic energy in the pn system is 10–20 MeV) to that for .Nuclear Physics A. -
Article: Multinucleon contributions to the 12C(π+, pp) reaction at 100 and 165 MeV incident pion energies
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ABSTRACT: Differential and total cross sections for π+ absorption on 12C are presented at incident pion energies of 100 and 165 MeV. This is the first time that this reaction has been measured with a combination of good energy and angle information over an extensive region of phase space. Results are compared to extensive Monte Carlo simulations in order to investigate the role of two- and multinucleon absorption processes in this nucleus. Signatures of ISI and FSI in the pion absorption process are also investigated, in order to explain the complex reaction mechanism implied by the data.Nuclear Physics A. -
Article: Pion production from deuterium bombarded with polarized protons of 277 and 500 MeV
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ABSTRACT: Analyzing power measurements of the reaction are reported at incident proton energies of 277 and 500 MeV. The 277 MeV results span the angular range from 70° to 130° in the centre of mass while the two 500 MeV measurements at large angles were taken as a check of published results. With the angular distribution of the analyzing power at 277 MeV now known, it is possible to show that the energy dependence of the analyzing power exhibits characteristics closely resembling the shape and magnitude of the analyzing power distribution observed for 1p shell nuclei of similar excitation energies.Nuclear Physics A. -
Article: POLARIZATION MEASUREMENTS IN PION DEUTERON BREAKUP AND ABSORPTION
http://dx.doi.org/10.1051/jphyscol:1990634.
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2001
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University of British Columbia - Vancouver
Vancouver, British Columbia, Canada
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