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Measurement of the Sigma pi photoproduction line shapes near the Lambda(1405)
Moriya, K. Schumacher, R. A. Bellis, M. Griffioen, K. A.
Moriya, K.
Schumacher, R. A.
Bellis, M.
Griffioen, K. A.
Abstract
The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant mass distributions or "line shapes" of the Sigma(+) pi-, Sigma - pi(+), and Sigma(0)pi(0) final states, from threshold at 1328 MeV/c(2) through the mass range of the Lambda(1405) and the Lambda(1520). The measurements were made with the CLAS system at Jefferson Lab using tagged real photons, for center-of-mass energies 1.95 < W < 2.85 GeV. The three mass distributions differ strongly in the vicinity of the I = 0 Lambda(1405), indicating the presence of substantial I = 1 strength in the reaction. Background contributions to the data from the Sigma(0)(1385) and from K*Sigma production were studied and shown to have negligible influence. To separate the isospin amplitudes, Breit-Wigner model fits were made that included channel-coupling distortions due to the N (K) over bar threshold. A best fit to all the data was obtained after including a phenomenological I = 1, J(P) = 1/2(-) amplitude with a centroid at 1394 +/- 20 MeV/c(2) and a second I = 1 amplitude at 1413 +/- 10 MeV/c(2). The centroid of the I = 0 Lambda(1405) strength was found at the Sigma pi threshold, with the observed shape determined largely by channel coupling, leading to an apparent overall peak near 1405 MeV/c(2).
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2013-01-01
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Moriya, K., Schumacher, R. A., Adhikari, K. P., Adikaram, D., Aghasyan, M., Anderson, M. D., ... & Batourine, V. (2013). Measurement of the Σ π photoproduction line shapes near the Λ (1405). Physical Review C, 87(3), 035206.
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Physics
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https://doi.org/10.1103/PhysRevC.87.035206