Search for and study of low-mass scalar mesons in reaction np → npπ+π− at neutron beam momentum P n = (5.20 ± 0.12) GeV/c

Abstract

We present the results of a search for and study of the resonance effects in the system of π + π -from the reaction np → npπ + π -at the momentum of quasi monochromatic neutrons P n = (5.20 ± 0.12) GeV/c from the data obtained in an exposure of the 1 m hydrogen bubble chamber of Veksler and Baldin Laboratory of High Energies, Joint Institute for Nuclear Research (VBLHE JINR). After the supplementary selection of the events where a secondary proton was emitted in the forward hemisphere in the general c.m.s. of the reac tion ( > 0) in the effective mass spectrum of π + π -combinations, we found nine peculiarities at the masses ± 11) MeV/c 2 with experimental widths of no more than several tens of MeV/c 2 . We carried out a direct measurement of the spins of resonances and also obtained other quantum numbers. All of these peculiarities have a similar set of quantum numbers I G (J PC ) = 0 + (0 ++ ). We investigated a sequence of scalar isoscalar resonances f 0 (σ 0 ) with masses in the range M ≤ 1200 MeV/c 2 . We found a phenomenological dependence of the resonance mass on its number. This dependence covered not only the resonances shown in this paper, but also those present in PDG tables with quantum numbers of f 0 (σ 0 ) mesons.

What do fractals learn us concerning the masses of fundamental particles, of hadrons, and of nuclei? Concerning also disintegration life-times?

“…Some very small mesonic structures close to M ≈ 700 MeV have been removed, since they were not observed in the measurement performed at JINR (Dubna) [23]. In the same way, the very small baryonic structure at M ≈ 953 MeV has been removed.…”

“…Fig. 10 shows in inserts (a) and (b) the log-log and successive mass ratios of the M π + π − invariant mass, from the np→npπ + π − reaction measured at Dubna [23]. Inserts (c) and (d) show the log-log and successive mass ratios of the M nK + invariant mass, from the np→npK + K − reaction measured at Dubna [24].…”

“…Several other excited excited level nuclei masses were studied through fractal presence [32]. These nuclei are: 16 O [33], 23 Na, 46 Ti, 62 Ni, 92 Zr, and 134 Ba. The corresponding results are omitted here.…”

Exotic Low Mass Unflavored Mesons: New Data Using Old Measurements

“…Several papers were published (with a small mass variation following the increase of statistics). The most recent paper [20] using the neutron p n = 5 GeV/c incident beam momentum allows to observe narrow structures at the following masses: M = 350 ± 3 MeV, 408 ± 3 MeV, 489 ± 3 MeV, 579 ± 5 MeV, 676 ± 7 MeV, 762 ± 11 MeV, 878 ± 7 MeV, 1036 ± 13 MeV, and 1170 ± 11 MeV. These structures are given with a number of standard deviations S.D.…”

“…Log of the exotic meson masses versus the log of the rank. The SPES3 data [8][9][10] are shown with solid red circles; the Dubna data [20] with empty purple crosses; the Lear data with p at rest [5] empty blue squares, the Lear data with p in movement [7] by blue star, the Uppsala data [13] with solid green triangles. The PDG masses [1] are also introduced, and are represented by black stars.…”