ππ pairs in nuclei and the σ meson

F. Bonutti, P. Camerini, E. Fragiacomo, N. Grion, R. Rui, J. T. Brack, L. Felawka, E. F. Gibson, G. Hofman, M. Kermani, E. L. Mathie, S. McFarland, R. Meier, K. Raywood, D. Ottewell, M. E. Sevior, G. R. Smith, and R. Tacik (The CHAOS Collaboration)
Phys. Rev. C 60, 018201 – Published 16 June 1999
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Abstract

In-medium pion-pion correlations were studied via their effect on experimental observables measured for the π+π+π± reaction in nuclei (A:12C,40Ca, and 208Pb) and in deuterium, from which it is inferred the observables for the nucleon (N: n and p). The measurements were performed at TRIUMF using a positive-pion flux with a bombarding energy of 283 MeV. The ππ invariant mass distributions Mππ were measured from the 2mπ threshold up to the kinematic maximum, and total cross sections σT deduced. The ππ medium modifications were investigated by forming the composite ratio CππA=(MππA/σTA)/(MππN/σTN) which proved to be only weakly affected by the (π,2π) reaction mechanism. In the I=J=0 channel the CππA distributions are peaked at the 2mπ threshold and increases with A. For pion pairs in the I=2, J=0 channel the CππA distributions are nearly independent of A. The distinctive behavior of CππA may be related to the appearance of the σ meson.

  • Received 10 December 1998

DOI:https://doi.org/10.1103/PhysRevC.60.018201

©1999 American Physical Society

Authors & Affiliations

F. Bonutti1,2, P. Camerini1,2, E. Fragiacomo1,2, N. Grion1,*, R. Rui1,2, J. T. Brack3, L. Felawka3, E. F. Gibson6, G. Hofman4, M. Kermani4, E. L. Mathie5, S. McFarland4, R. Meier3, K. Raywood3, D. Ottewell3, M. E. Sevior7, G. R. Smith3, and R. Tacik5

  • 1Istituto Nazionale di Fisica Nucleare, I-34127 Trieste, Italy
  • 2Dipartimento di Fisica dell’Universita’ di Trieste, I-34127 Trieste, Italy
  • 3TRIUMF, Vancouver, British Columbia, Canada V6T 2A3
  • 4Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada V6T 2A6
  • 5University of Regina, Regina, Saskatchewan, Canada S4S 0A2
  • 6California State University, Sacramento, California 95819
  • 7School of Physics, University of Melbourne, Parkville, Victoria, 3052, Australia

  • *Corresponding author. Electronic address: Grion@ts.INFN.it

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Vol. 60, Iss. 1 — July 1999

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