CERN Accelerating science

Preprint
Report number	E1-2002-214 ; JINR-E1-2002-214
Title	Resonances in the System of \pi^{+}\pi^{-}-Mesons from np\to np\pi^{+}\pi^{-} Reaction at P_{n}=5.20 GeV\/c : Search, Results of Direct Observations, Interpretation
Author(s)	Troyan, Yu A ; Plekhanov, E B ; Pechenov, V N ; Troyan, Yu A ; Belyaev, A V ; Jerusalimov, A P ; Arakelian, S G
Affiliation	(Veksler and Baldin Laboratory of High Energies, Dubna)
Publication	2002
Imprint	18 Sep 2002
Number of pages	7
Published in:	Part. Nucl. Lett.
Subject category	Particle Physics - Experiment
Abstract	Ten resonances were found in the mass spectrum of \pi^{+}\pi^{-} system based on 66075 events from np\to np\pi^{+}\pi^{-} reaction in np-interactions at P_{n}=(5.20\pm0.16) GeV/c in the one-meter hydrogen bubble chamber of the LHE (JINR) by using the criterion cos\Theta^{*}p>0. These masses are the following: (347\pm12), (418\pm6), (511\pm12), (610\pm5), (678\pm17), (757\pm5), (880\pm12), (987\pm12), (1133\pm15), and (1285\pm22) MeV/c^{2}; their excesses above the background are 2.9, 5.2, 3.5, 1.4, 2.0, 8.5, 4.8, 3.8, 5.2, and 6.0 standard deviations, respectively. The experimental widths of the resonances vary within the region from 16 to 94 MeV/c^{2}. Such effects were not found in \pi^{-}\pi^{0} combinations from np\to pp\pi^{-}\pi^0 reaction. Therefore, it is necessary to attribute the value of isotopic spin I=0 to the resonances found in the mass spectrum of the \pi^{+}\pi^{-} system. The spin was estimated for the most statistically provided resonances at masses of 418, 511 and 757 MeV/c^{2}. We determine with a high degree of confidence that J=0 for the resonances at M_{R}=757 MeV/c^{2} and M_{R}=418 MeV/c^{2} and the most probable value of J=0 for the resonance at M_{R}=511 MeV/c^{2}. Therefore, it can be affirmed that at least 3 states with quantum numbers of \sigma_{0}-meson 0^{+}(0^{++}) have been found at masses of 418, 511 and 757 MeV/c^{2}. The fact that low-mass \sigma_{0}-mesons are glueballs is one of the possible interpretations. The comparison with the data of other papers has also been made.
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