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We report on measurements of the differential π±p cross section at pion energies Tπ=32.7, 45.1, and 68.6 MeV. The measurements, covering the angular range 25°≤θlab≤123°, have been carried out at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland, employing the magnet spectrometer LEPS. The absolute normalization of the π±p cross sections have been achieved by relating them to the electromagnetic cross sections of μ±12C scattering. The results are in agreement with those of our preceding measurements at Tπ=32.2 and 45.1 MeV insofar as they overlap with the region of the Coulomb nuclear interference investigated there. A comparison with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, which has formed the basis for the determination of the ‘‘experimental’’ σ term, reveals considerable deviations. These are most pronounced for the π+p cross sections at Tπ=32.7 and 45.1 MeV. Single energy partial wave fits result in S-wave contributions, which are about 1° lower in magnitude then those specified by the KH80 solution. The data at 68.6 MeV are in good agreement with the phase shift analysis.

3 data tables

Table 1

Statistical and systematic errors are addet in quadrature.

Table 2

Statistical and systematic errors are addet in quadrature.

Table 3

Statistical and systematic errors are addet in quadrature.

Low-energy differential cross-sections of pion proton (pi+- p) scattering. 1: The Isospin even forward scattering amplitude at T(pi) = 32.2-MeV and 44.6-MeV

Joram, C. ; Metzler, M. ; Jaki, J. ; et al.

Phys.Rev.C 51 (1995) 2144-2158, 1995.

Inspire Record 404658 DOI 10.17182/hepdata.25972

The values of the pion nucleon (πN) σ term, as determined, on the one hand, from experimental pion nucleon scattering by means of dispersion relations and, on the other hand, from baryon masses by means of chiral perturbation theory, differ by 10 to 15 MeV. The origin of this discrepancy is not yet understood. If the difference between the two values is attributed to the scalar current of strange sea quark pairs within the proton, the contribution to the proton mass would be of the order of 120 MeV. The discrepancy may hint at either theoretical deficiencies or an inadequate πN database. In order to provide reliable experimental data we have measured angular distributions of elastic pion proton scattering at pion energies Tπ=32.2 and 44.6 MeV using the magnet spectrometer LEPS located at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland. From the data covering the region of the Coulomb nuclear interference, the real parts of the isospin-even forward scattering amplitude ReD+(t=0), have been determined as a function of energy. The results have been compared with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, revealing discrepancies most pronounced for the π+p data. The experimentally determined values for ReD+(t=0), however, support the KH80 prediction (which is based on πN data available in 1979).

2 data tables

Table 1

Statistical and systematic errors are addet in quadrature.

Table 2

Statistical and systematic errors are addet in quadrature.

Further studies of the x (1910) meson

The IHEP-IISN-KEK-LANL-LAPP collaboration Alde, D. ; Binon, F.G. ; Boutemeur, M. ; et al.

Phys.Lett.B 276 (1992) 375-378, 1992.

Inspire Record 322740 DOI 10.17182/hepdata.48134

New data on the ν ′ ν system produced in the π − p charge exchange at 38 GeV c momentum confirm the existence of the narrow ν ′ ν resonance X(1910). The hypothesis of the X(1910) quantum numbers being a J PC = 1 −+ , forbidden for the q[ovbar|q] meson, is proposed to explain the extremely low limits obtained for X(1910) decays through π 0 π 0 , νν and K 0 s K 0 s channels and the flat t -dependence of the X(1910) production cross section.

4 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

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Evidence for a 1.9-{GeV} Meson Decaying Into $\eta \eta^\prime$

The IFVE-Brussels-Annecy-Los Alamos collaboration Alde, D. ; Binon, F.G. ; Bricman, C. ; et al.

Phys.Lett.B 216 (1989) 447, 1989.

Inspire Record 267048 DOI 10.17182/hepdata.29856

Evidence for a new meson decaying into ηη′ has been found in 38 GeV π − p charge-exchange interactions. The mass and the width of this meson are (1917 ± 15) MeV and (90 −50 +35 ) MeV, respectively. Possible spin and parity assignments are J PC = 0 ++ , 1 −+ or 2 ++ , isospin and G -parity are I G = 0 + . The t -dependence of the differential cross section follows an exponential behaviour exp( bt with a small slope: b = (2±1) (GeV/ c ) −2 .Upper limits on its decay into ππ, ηη and K K exotic interpretation of this meson.

1 data table

Table 1

No description provided.

Study of $\omega \omega$ Systems Produced in 38-{GeV}/$c \pi^- p$ Collisions

The IHEP-IISN-LANL-LAPP-TSUIHEP collaboration Alde, D. ; Binon, F.G. ; Bricman, C. ; et al.

Phys.Lett.B 216 (1989) 451, 1989.

Inspire Record 267049 DOI 10.17182/hepdata.29857

The π − p→ ωω n reaction has studied for the first time at the 70 GeV IHEP accelerator. The six photons from the decay of the two ω mesons were detected in GAMS-2000, a hodoscope multi-photon spectometer. Two resonances decaying into ωω,X (1640) and X(1960), have been observed. Their quantum numbers are J PC =2 ++ , I G =0 + . The reaction is dominated by the one-pion exchange mechanism. The production cross sections σ. BR(X→ ωω ) are 0.65±0.15 μ b and 1.0±0.2 μ b, respectively.

2 data tables

Table 1

X(1640) IS A JPC - 2++, IG - 0+ MESON WITH MASS 1643+-7 MEV.

Table 2

X(1960) IS A JPC - 2++, IG - 0+ MESON WITH MASS 1956+-20 MEV.

OBSERVATION OF AN EXOTIC MESON OF 1.9-GeV MASS DECAYING INTO eta-prime eta

The IFVE-Brussels-Annecy-Los-Alamos collaboration Alde, D. ; Binon, F.G. ; Bricman, C. ; et al.

Sov.J.Nucl.Phys. 48 (1988) 1035, 1988.

Inspire Record 264474 DOI 10.17182/hepdata.40730

None

2 data tables

Table 1

No description provided.

Table 2

No description provided.

Observation of a 1750-{MeV} Narrow Meson Decaying Into $\eta \eta$

The Serpukhov-Brussels-Los Alamos-Annecy(LAPP) collaboration Alde, D. ; Binon, F. ; Bricman, C. ; et al.

Phys.Lett.B 182 (1986) 105, 1986.

Inspire Record 233596 DOI 10.17182/hepdata.30211

A narrow meson which decays into ηη is observed in 38 GeV/ c π − p collisions at large momentum transfer. The experiment has been performed at the Serpukhov accelerator with the GAMS-2000 spectrometer. The mass of this new meson is (1755 ± 8) MeV, its width is less than 50 MeV. Its spin-parity is J PC =0 ++ or less probably 2 ++ .

1 data table

Table 1

No description provided.

OBSERVATION OF A NARROW MESON WITH A MASS OF 1750-MeV DECAYING INTO eta eta PAIR

The Serpukhov-Brussels-Annecy(LAPP) collaboration Alde, D. ; Binon, F.G. ; Bricman, C. ; et al.

IFVE-86-155, 1986.

Inspire Record 234608 DOI 10.17182/hepdata.10523

None

3 data tables

Table 1

No description provided.

Table 2

No description provided.

Table 3

No description provided.

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A secondary peak at t = −1 (GeV/c)2 in high energy π-p charge exchange scattering

π−+p→π0+n Charge-Exchange Scattering at High Energies

Low-energy differential cross-sections of pion proton (pi+- p) scattering. 2: Phase shifts at T(pi) = 32.7-MeV, 45.1-MeV, and 68.6-MeV

Low-energy differential cross-sections of pion proton (pi+- p) scattering. 1: The Isospin even forward scattering amplitude at T(pi) = 32.2-MeV and 44.6-MeV

Further studies of the x (1910) meson

Evidence for a 1.9-{GeV} Meson Decaying Into $\eta \eta^\prime$

Study of $\omega \omega$ Systems Produced in 38-{GeV}/$c \pi^- p$ Collisions

OBSERVATION OF AN EXOTIC MESON OF 1.9-GeV MASS DECAYING INTO eta-prime eta

Observation of a 1750-{MeV} Narrow Meson Decaying Into $\eta \eta$

OBSERVATION OF A NARROW MESON WITH A MASS OF 1750-MeV DECAYING INTO eta eta PAIR