Debenham, Nicholas Charles
Pion-Proton Scattering
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Pion-Proton Charge-Exchange Scattering from 500 to 1300 MeV

Chiu, Charles B. ; Eandi, Richard D. ; Helmholz, A.Carl ; et al.
Phys.Rev. 156 (1967) 1415-1426, 1967.
Inspire Record 52278 DOI 10.17182/hepdata.750

Differential cross sections for the reaction π−p→π0n were measured at nine incident-pion kinetic energies in the interval from 500 to 1300 MeV. The negative pion beam from the bevatron was focused on a liquidhydrogen target completely surrounded by a cubic array of six steel-plate spark chambers. The spark chambers were triggered on events with neutral final states. Charge-exchange events were identified from the one-shower and two-shower events in the spark-chamber pictures. By the Monte Carlo technique, the π0 distributions were calculated from the bisector distributions of the two-shower π0 events together with the observed γ-ray distributions of the one-shower π0 events. These π0 distributions were fitted with both Legendre-polynomial expansions and power-series expansions by the method of least squares. The extrapolated forward differential cross sections are in good agreement with the dispersion calculations. The Legendre coefficients for the differential cross sections in isospin state T=12 were obtained by combining our results with available data on π±p elastic scattering. In the light of existing phase-shift solutions, the behavior of these coefficients is discussed. The D5F5 interference term that peaks near 900 MeV is verified to be in isospin state T=12 only. We report here also the total neutral cross sections and the cross sections for the production of neutral multipion final states 2π0n and 3π0n. The 4π solid angle and the calibrated energy response of the spark chambers contribute to the accuracy of the results.

19 data tables
Table 1

No description provided.

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A resolution study of backward $\pi^- p$ reactions between 0.6 and 1.0 GeV/c

Debenham, Nicholas Charles ;
PhD Thesis, Imperial Coll., London, 1973.
Inspire Record 1499121 DOI 10.17182/hepdata.75616

None

312 data tables
Table 1

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Search for neutral mesons near 1 gev/c-squared

Binnie, D.M. ; Camilleri, L. ; Carr, J. ; et al.
Phys.Rev.Lett. 32 (1974) 392-395, 1974.
Inspire Record 94572 DOI 10.17182/hepdata.21308

In a study of the missing-mass spectrum near 1 GeV in the reaction π−+p→MM+n at three incident momenta near 2 GeV, we find no evidence for the recently reported narrow neutral mesons at 940, 963, and 1033 MeV.

1 data table
Table 1

No description provided.


Direct evidence for the s* meson near the k anti-k threshold

Binnie, D.M. ; Carr, J. ; Debenham, N.C. ; et al.
Phys.Rev.Lett. 31 (1973) 1534-1537, 1973.
Inspire Record 94702 DOI 10.17182/hepdata.48037

We report observation of the S* meson in the reaction π−+p→S*+n. The S* decays into ππ and KK and is seen most clearly in the 2π0 channel. A fit to the data gives a sheet-II pole at 987±7−i(24±7) MeV and a relative coupling gS→KKgS→ππ of 3.8 ± 1.0.

1 data table
Table 1

AT AROUND K+ K- THRESHOLD.


Study of narrow mesons near their thresholds

Binnie, D.M. ; Camilleri, L. ; Debenham, N.C. ; et al.
Phys.Rev.D 8 (1973) 2789-2813, 1973.
Inspire Record 93328 DOI 10.17182/hepdata.47579

A novel form of mass spectrometer has been used to measure the masses, widths, and cross sections of the η, ω, X0(958), and φ mesons near their respective thresholds in the reaction π−+p→missingmass+n. The incident momentum is varied in small steps through the threshold while neutrons of a given momentum are detected near zero degrees. The lower limit of the c.m. momentum P* at which measurements have been made ranges from about 50 MeV/c at the φ to about 30 MeV/c at the η. A somewhat low value for the ω mass, 782.3 ± 0.6 MeV, is found. The width of the X0 is < 1.9 MeV (95% confidence level). All four mesons show evidence of S-wave production, with values of σP* of 21.2 ± 1.8, 0.35 ± 0.03, and 0.29 ± 0.06 μb/(MeV/c) for the η, X0, and φ, respectively. A rapid rise in the ω cross section appears to be modified by a final-state interaction. The effect of this rise can probably be seen in some S11 pion-nucleon phase-shift solutions. Evidence is also presented of a sudden drop in the π+π− mass spectrum just above the threshold for the production of a K+K− pair. The paper includes a comprehensive discussion of the method and of the details of the spectrometer.

1 data table
Table 1

CROSS SECTIONS NEAR THRESHOLD.


Backward pi- p Reactions Between 0.6-GeV/c and 1-GeV/c

Debenham, N.C. ; Binnie, D.M. ; Camilleri, L. ; et al.
Phys.Rev.D 12 (1975) 2545-2556, 1975.
Inspire Record 104820 DOI 10.17182/hepdata.24845

Measurements are reported of the differential cross section for the reaction π−p→π−p,π0n,andηn at three angles close to 180° and for incident momenta in the range 0.6 to 1.0 GeV/c. The three measurements were made simultaneously at 1% intervals of beam momentum. The data on elastic scattering resolve a discrepancy between two earlier experiments. They also show clearly the effect of the opening of the ηn channel. The charge-exchange data show that I-spin bounds are not violated in the kinematic region covered. The ηn data can be adequately described with known s-channel resonances. No evidence for narrow N*'s is seen in any channel.

2 data tables
Table 1

No description provided.

Table 2

No description provided.


Study of omega Production Near Threshold in the Reaction pi- p --> omega n

Keyne, J. ; Binnie, D.M. ; Carr, J. ; et al.
Phys.Rev.D 14 (1976) 28-41, 1976.
Inspire Record 115718 DOI 10.17182/hepdata.24698

We have investigated ω production in the reaction π−p→ωn very close to threshold. The dependence of the mass, width, branching ratio, and cross section upon the final-state c.m. momentum, P*, were studied. The mass and width were independent of P* with values of 782.4 ± 0.5 and 10.22 ± 0.43 MeV, respectively. The branching ratio Γ(ω→π0γ)Γ(ω→π+π−π0) was also constant, having a value of 0.084 ± 0.013. An upper limit of 0.18 was set on the branching ratio Γ(ω→π0π0γ)Γ(ω→π0γ). We observed a rapid fall in the cross section below P*=100 MeV/c. This could not be explained in terms of S-wave production alone, but could be fitted by a resonant P wave plus a noninterfering S wave.

1 data table
Table 1

CROSS SECTION DEPENDENCE ON FINAL STATE CENTRE OF MASS MOMENTUM. TABULATED VALUES TAKEN FROM TABLE 1 OF H. KARAMI ET AL., NP B154, 503 (1979).


ELASTIC SCATTERING AND OMEGA MESON PRODUCTION NEAR THE THRESHOLD OF PI- P ---> OMEGA N

Karami, H. ; Carr, J. ; Debenham, N.C. ; et al.
Nucl.Phys.B 154 (1979) 503-518, 1979.
Inspire Record 146573 DOI 10.17182/hepdata.34745

Measurements are reported of the differential cross section for the reaction π − +p→ ω +n from threshold to a final-state c.m. momentum P ∗ of 200 MeV /c . The previously reported fall in total cross section σ/P ∗ below about 100 MeV/ c is again seen. The differential cross section remains close to isotropic over the entire range. A paralle experiment on the variation in the elastic differential cross section across the threshold shows evidence of this threshold. The elastic data cover a range of incident moments from 1010 to 1180 MeV/ c in steps of 5 MeV/ c .

4 data tables
Table 1

CROSS SECTION DEPENDENCE ON FINAL STATE CENTRE OF MASS MOMENTUM.

Table 2

ANGULAR DISTRIBUTIONS ARE ALMOST ISOTROPIC.

Table 3

LEGENDRE POLYNOMIAL COEFFICIENTS NORMALIZED SUCH THAT SIG = 4*PI*LEG(L=0).

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CUSP IN PI- P ELASTIC SCATTERING AT THE ETA THRESHOLD

Sarma, H.N.K. ; Binnie, D.M. ; Carr, J. ; et al.
Nucl.Phys.B 161 (1979) 1-13, 1979.
Inspire Record 147683 DOI 10.17182/hepdata.34612

We present results from a high momentum resolution measurement of the π − p elastic differential cross section near the η production threshold. By analysing the cusp discontinuity in the elastic cross section we deduce the non-spin-flip elastic amplitude and compare it with solutions from phase-shift analyses.

601 data tables
Table 1

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Table 3

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PI- P ELASTIC SCATTERING IN THE REGION OF THE X0 (957.6) THRESHOLD

Moissidis, P.G. ; Sarma, H.N.K. ; Carr, J. ; et al.
Nuovo Cim.A 75 (1983) 123-162, 1983.
Inspire Record 196214 DOI 10.17182/hepdata.8694

We present results from a high-momentum-resolution measurement of the π-p elastic differential and total cross-sections-at values of cos θ* between — 0.60 and 0.85 in the centre-of-mass system and at incident-beam momenta between 1.34GeV/c and 1.49 GeV/c—close to the X0 production threshold. There is no significant enhancement near the X0 production threshold. However, a small effect of ~ 3 standard deviations is present, having mass 1898.8 MeV and width ~5MeV, and appearing at an incident-pion momentum of 1435 MeV/c. In addition, a narrow ~ 5-standard-deviation effect atEc.m.= 1876 MeV appeared at an incident-pion momentum of 1389 MeV/c.

10 data tables
Table 1

No description provided.

Table 2

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Table 3

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