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Hidden Strangeness in the Proton? Determination of the Real Part of the Isospin Even - Forward Scattering Amplitude of Pion Nucleon Scattering at 54.3-{MeV}

Wiedner, U. ; Goring, K. ; Jaki, J. ; et al.

Phys.Rev.D 40 (1989) 3568-3581, 1989.

Inspire Record 287810 DOI 10.17182/hepdata.23079

The contradiction of the σ term of pion-nucleon scattering as deduced from the Karlsruhe-Helsinki phase shifts with the smaller value calculated by the chiral perturbation theory of QCD is well known. In an effort to clarify the discrepancy we have determined the real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering at a pion energy Tπ=54.3 MeV by measurement of the elastic scattering of positive and negative pions on protons in the Coulomb-nuclear interference region. The deduced value is in agreement with the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. The resulting large value of the σ term may be interpreted as being due to the influence of s¯s sea pairs even at large distances (small Q2) as previously suggested by the European Muon Collaboration measurement of deep-inelastic scattering of polarized muons on polarized protons.

1 data table match query

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A measurement of elastic pion-proton scattering at 50 gev

Derevchekov, A.A. ; Golovin, N.I. ; Khodirev, Y.C. ; et al.

Phys.Lett.B 48 (1974) 367-370, 1974.

Inspire Record 95356 DOI 10.17182/hepdata.27998

We have measured elastic pion-proton scattering in a 50 GeV/ c π − beam at the 76 GeV proton synchrotron in Serpukhov. Data are presented for four-momenta transfer squared in the range 0.03 < t < 0.4 (GeV/ c ) 2 .

1 data table match query

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SLOPE IS 9.1, +0.2, -0.4 GEV**-2 (INCLUDING SYSTEMATIC ERRORS).

Forward angle pi+- p elastic scattering differential cross-sections at T(pi) = 87-MeV to 139-MeV

Brack, J.T. ; Amaudruz, P.A. ; Ottewell, D.F. ; et al.

Phys.Rev.C 51 (1995) 929-936, 1995.

Inspire Record 400646 DOI 10.17182/hepdata.25894

Absolute π±p elastic scattering differential cross sections have been measured at five incident pion energies between 87 and 139 MeV. An active target of scintillator material (CH1.1) was used to detect recoil protons in coincidence with scattered pions. Pions were detected at forward angles between 27 and 98°c.m. where the low-energy recoil protons stop in the target. The cross sections, typically 5–10% lower than phase shift predictions for π+p and 10–20% lower for the π−p cross sections, are consistent with earlier measurements by this group.

5 data tables match query

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Elastic Backward Scattering of Negative Pions on Protons at 25-GeV/c and 38-GeV/c

Babaev, A. ; Brakhman, E. ; Danilov, M. ; et al.

Phys.Lett.B 67 (1977) 351, 1977.

Inspire Record 109000 DOI 10.17182/hepdata.39798

The backward elastic scattering reaction π − p → p π − at momenta 25 and 38 GeV/ c have been measured using a magnetic spectrometer with hybrid chambers. The experimental data on the dependence of the cross section d σ /d u on the momentum transfer u as well as the energy dependence d σ /d u at u = 0 are given.

2 data tables match query

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Operation and Performance of a System for $\pi p$ and $\pi D$ Backward Scattering

Stanovnik, A. ; Kernel, G. ; Tanner, N.W. ; et al.

Nucl.Instrum.Meth. 177 (1980) 369, 1980.

Inspire Record 152948 DOI 10.17182/hepdata.41451

A simple, large-solid-angle apparatus, specially suited for the measurement of backward elastic scattering of medium-energy pions on protons and deuterons, is described. The method of analysis which reduces background and determines elastic events from a data sample of 185 MeV negative pions incident on a D 2 O target is discussed. Results for 141 MeV π + p and 185 MeV π − p backward cross-sections are also presented and compared with cross-sections calculated from known phase shifts.

2 data tables match query

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$K^- p$ elastic scattering at 2.24 GeV/c

Dickinson, M. ; Miyashita, S. ; Libby, L.Marshall ; et al.

Phys.Lett.B 24 (1967) 596-598, 1967.

Inspire Record 1389623 DOI 10.17182/hepdata.29569

The differential elastic scattering cross section for 2.24 GeV/ c K − p collisions has been measured in film from the Brookhaven 20″ bubble chamber. The total elastic cross section is found to be 6.2 ± 0.7 mb. The exponential dependence on square of the momentum t in (GeV/ c ) 2 is fitted by ( d σ d Ω elastic = (12.4 ± 1.0 mb/sr) exp (7.81 ± 0.25)t . A A fit to a black disc model requires a radius of 0.95 ± 0.05 fm.

1 data table match query

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D(SIG)/D(T) was fitted to CONST*EXP(-SLOPE*T).

Measurements of pi- p elastic scattering from 1.71 to 5.53 gev/c

Fellinger, M. ; Gutman, E. ; Lamb, R.C. ; et al.

Phys.Rev.D 2 (1970) 1777-1782, 1970.

Inspire Record 61322 DOI 10.17182/hepdata.47092

The π−p elastic scattering differential cross section has been obtained at 18 incident momenta from 1.71 to 5.53 GeV/c. The measurements were taken over a limited range of squared four-momentum transfer t near the forward direction. The statistical accuracy and resolution of these data are comparable to, or better than, existing data. The parameter b in the expression dσdt=Aebt has been determined at each of our incident momenta, and a large (∼25%) enhancement in b as a function of momentum is observed at a c.m. energy of ∼2290 MeV. The relation of this bump in b with the well-established bump in the total π−p cross section at ∼2200 MeV is discussed.

18 data tables match query

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Determination of the Real Part of the Isospin Even Forward Scattering Amplitude of Pion Nucleon Scattering at 55-{MeV} as a Test of Low-energy Quantum Chromodynamics

Wiedner, U. ; Goring, K. ; Jaki, J. ; et al.

Phys.Rev.Lett. 58 (1987) 648-650, 1987.

Inspire Record 246624 DOI 10.17182/hepdata.20153

The real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering has been determined at a pion energy of Tπ=55 MeV by measurement of the elastic scattering of positive and negative pions on protons within the Coulomb-nuclear interference region. The value confirms the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. These phases have been used to determine the σ term of pion-nucleon scattering by means of dispersion relations, resulting in a value for σ which is in contradiction with chiral perturbation theory of QCD.

1 data table match query

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PI- P cross sections normalised to the Coulomb cross section taken from the Karlesruhe-Helsinki phase shift analysis (R. Koch, E. Pietarinen (NP A336(80)331).

Backward pi- p elastic scattering at 3 and 4 gev/c

Brabson, A. ; Calvelli, G. ; Cittolin, S. ; et al.

Phys.Lett.B 42 (1972) 283-286, 1972.

Inspire Record 85009 DOI 10.17182/hepdata.28198

We have measured dσ du for π − p elastic scattering at 3 and 4 GeV c in the ranges −0.119⩽ u ⩽0.113 and −0.233⩽ u ⩽0.088, respectively. A fit of the form d σ /d u = A exp ( Bu + Cu 2 ) gives B = 4.34±0.42 and C = 7.0±3.5 at 4 GeV c with χ 2 = 5.7 for 9 degrees of freedom; the simpler form d σ /d u = A exp( Bu ) gives B = 3.7 ± 0.3 with χ 2 = 9.6. At 3 GeV c we confirm with high statistics the structures already observed.

2 data tables match query

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