2002/10/17 by M. Svec, M. Švec, Svec, M.
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph) #Nuclear physics research studies #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex #hep-ph
paper · pdf · doi:10.48550/arxiv.hep-ph/0210249
29 pages (RevTex), 13 figures
arxiv created 2002/10/17 · openalex publication_date 2002/10/17 · arxiv updated 2009/11/30 · openalex created_date 2024/04/11 · openalex updated_date 2026/07/28
We present a new model independent amplitude analysis of reaction pi(-)p->pi(-) pi(+)n measured at CERN at 17.2 GeV/c on polarized target using a Monte Carlo method for dipion mass 580-1080 MeV. The two solutions for measured moduli |Sbar|2 and |S|2 of the two S-wave transversity amplitudes Sbar and S show res onant behaviour below 800 MeV corresponding to a scalar resonance sigma(770). Simultaneous fits to |Sbar|2 and |S|2 include f0(980). The CERN data on polar ized target supplemented by the assumption of analyticity of production amplitud es in dipion mass allow to determine the helicity amplitudes S0 (a1 exchange) and S1 (pi exchange) from fitted transversity amplitudes. The sign ambiguity in sigma(770) contribution leads to 2 solutions. In the "down" solution sigma(770) is suppressed in the helicity flip amplitude S1 and thus also in pi(-)pi(+)-> pi(-)pi(+) scattering. Most contribution of sigma(770) to pion production is in the nonflip amplitude S0, or in pi(-)a1(+)->pi(-)pi(+) scattering. In the "up" solution the situation is reversed. The "up" solution is excluded by unitarity in pipi scattering. The "down" solution, and thus the evidence for sigma(770), is in agreement with unitarity in both pi(-)pi(+)->pi(-)pi(+) and pi(-)a1(+)-> pi(-)pi(+) scattering. There are 4 "down" solutions (1, 1bar), (2, 1bar), (1, 2bar) and (2, 2bar). The sigma(770) resonance manifests itself as a broad resonant structure at ~ 720 MeV in the flip amplitude |S1|2 in solutions (1, 1bar) and (2, 1bar). The contribution of sigma(770) to |S1|2 is small in solutions (1, 2bar) and (2, 2bar). The metamorphosis of a narrow sigma(770) in the nonflip amplitude S0 into a broad resonant structure in the flip amplitude S1 is a new phenomenon related to breaking of scale and chiral symmetry in QCD.