Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the pi- pi- pi+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data show a significant natural parity exchange production of a resonance with spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The resonant nature of this wave is evident from the mass-dependent phase differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2 is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged; version 3 updated authors, text shortened, data unchange

Experimental antiproton nuclear stopping power in H2 and D2

Data about antiprotons slowing down in gaseous targets at very low energies (E<1 keV) show that the stopping power in D2 is lower than in H2; the right way to explain this behavior seems to be through a nuclear stopping power derived from the classical Rutherford formula

Antiproton stopping power in He in the energy range 1-900 keV and the Barkas effect

The p stopping power in helium from 1 keV kinetic energy is evaluated. Contrary to the effect observed around and below the maximum, Obelix data indicate a p stopping power higher than that for proton, the difference being of the order of 15 ± 5% at ≈ 700 keV. The result contributes to assert the fundamental difference between p stoppings in the simplest gases (He, H2 ) and in solid targets below some MeV

(p)over-barD and (p)over-bar He-4 annihilation cross sections at very low energy

The (p) over bar D and (p) over bar(4) He total annihilation cross sections have been measured with the Obelix apparatus at LEAR at, respectively, three and two values of the (p) over bar incident momentum between 70 MeV/c and 36 MeV/c. The values of the (p) over bar D annihilation cross section, at such low energies, are in agreement with a surprising result obtained in a recent low statistics measurement of the antiprotonic deuterium K-alpha X-rays [M. Augsburger et al., Phys. Lett. B 461 (1999) 417] (see following article), concerning the unexpected narrow width of the antiprotonic deuterium Is level. (C) 1999 Published by Elsevier Science B.V. All rights reserved

(p)over-barD and (p)over-bar He-4 annihilation cross sections at very low energy

72nonenoneZENONI A; BIANCONI A; BONOMI G; CORRADINI M; DONZELLA A; E. LODI RIZZINI; VENTURELLI L; BERTIN A; BRUSCHI M; CAPPONI M; DE CASTRO S; DONA R; GALLI D; GIACOBBE B; MARCONI U; MASSA I; PICCININI M; CESARI NS; SPIGHI R; VAGNONI V; VECCHI S; VILLA M; VITALE A; ZOCCOLI A; POLI M; CICALO C; MASONI A; MAURO S; PUDDU G; SERCI S; USAI G; GORCHAKOV OE; PRAKHOV SN; ROZHDESTVENSKY AM; TRETYAK VI; GIANOTTI P; GUARALDO C; LANARO A; LUCHERINI V; PETRASCU C; GASTALDI U; VANNUCCI L; RICCI RA; BENDISCIOLI G; FONTANA A; MONTAGNA P; ROTONDI A; SALVINI P; MIRFAKHRAI N; BALESTRA F; BUSSA MP; BUSSO L; CERELLO P; DENISOV OY; FERRERO L; GARFAGNINI R; GRASSO A; PANZARASA A; PANZIERI D; TOSELLO F; BOTTA E; BRESSANI T; CALVO D; COSTA S; D'ISEP F; FELICIELLO A; FILIPPI A; MARCELLO S; AGNELLO M; IAZZI F; MINETTI B; TESSARO SZenoni, Aldo; Bianconi, Andrea; Bonomi, Germano; Corradini, Maurizio; Donzella, Antonietta; LODI RIZZINI, Evandro; Venturelli, Luca; Bertin, A; Bruschi, M; Capponi, M; DE CASTRO, S; Dona, R; Galli, D; Giacobbe, B; Marconi, U; Massa, I; Piccinini, M; Cesari, Ns; Spighi, R; Vagnoni, V; Vecchi, S; Villa, M; Vitale, A; Zoccoli, A; Poli, M; Cicalo, C; Masoni, A; Mauro, S; Puddu, G; Serci, S; Usai, G; Gorchakov, Oe; Prakhov, Sn; Rozhdestvensky, Am; Tretyak, Vi; Gianotti, P; Guaraldo, C; Lanaro, A; Lucherini, V; Petrascu, C; Gastaldi, U; Vannucci, L; Ricci, Ra; Bendiscioli, G; Fontana, A; Montagna, P; Rotondi, A; Salvini, P; Mirfakhrai, N; Balestra, F; Bussa, Mp; Busso, L; Cerello, P; Denisov, Oy; Ferrero, L; Garfagnini, R; Grasso, A; Panzarasa, A; Panzieri, D; Tosello, F; Botta, E; Bressani, T; Calvo, D; Costa, S; D'Isep, F; Feliciello, A; Filippi, A; Marcello, S; Agnello, M; Iazzi, F; Minetti, B; Tessaro, S