[en] An amplitude analysis of an exclusive sample of 5765 events from the reaction π^- p → η(prime)π^- p at 18 GeV/c is described. The η(prime)π^- production is dominated by natural parity exchange and by three partial waves: those with J^PC = 1^-+, 2⁺⁺, and 4⁺⁺. A mass-dependent analysis of the partial-wave amplitudes indicates the production of the a₂(1320) meson as well as the a₄(2040) meson, observed for the first time decaying to η(prime)π^-. The dominant, exotic (non-q(bar q)) 1^-+ partial wave is shown to be resonant with a mass of 1.597 ± 0.010_-0.010^+0.045 GeV/c² and a width of 0.340 ± 0.040 ± 0.050 GeV/c². This exotic state, the π₁(1600), is produced with a t dependence which is different from that of the a₂(1320) meson, indicating differences between the production mechanisms for the two states

[en] The reaction π^- p → ωπ^- p, ω → π⁺ π^- π⁰ has been studied at 18 GeV/c. The ωπ^- mass spectrum is found to be dominated by the b₁(1235). Partial Wave Analysis shows that b₁ production is dominated by natural parity exchange. The S-wave and D-wave amplitudes for b₁(1235) → ωπ have been determined, and it is found that the amplitude ratio, |D/S| = 0.269 ± (0.009)_stat ± (0.01)_sys and the phase difference, φ(D-S) = 10.54^o ± (2.4^o)_stat ± (3.9)_sys

[en] This Letter reports results from the partial wave analysis of the π^-π^-π⁺η final state in π^-p collisions at 18 GeV/c. Strong evidence is observed for production of two mesons with exotic quantum numbers of spin, parity and charge conjugation, J^PC=1^-+ in the decay channel f₁(1285)π^-. The mass M=1709±24±41 MeV/c² and width Γ=403±80±115 MeV/c² of the first state are consistent with the parameters of the previously observed π₁(1600). The second resonance with mass M=2001±30±92 MeV/c² and width Γ=333±52±49 MeV/c² agrees very well with predictions from theoretical models. In addition, the presence of π₂(1900) is confirmed with mass M=2003±88±148 MeV/c² and width Γ=306±132±121 MeV/c² and a new state, a₁(2096), is observed with mass M=2096±17±121 MeV/c² and width Γ=451±41±81 MeV/c². The decay properties of these last two states are consistent with flux tube model predictions for hybrid mesons with non-exotic quantum numbers

[en] A partial-wave analysis of the reaction π^-p→π⁺π^-π^-p at 18 GeV/c has been performed on a data sample of 250,000 events obtained in the Brookhaven experiment E852. The well-known a₁(1260), a₂(1320) and π₂(1670) resonant states are observed. The existence of the π(1800), a₁(1700) and a₄(2040) states is confirmed. The a₃(1874) state is also observed. The exotic 1^-+ π₁(1600) state produced in the natural parity exchange process is found to decay in the ρ(770)π^- channel. A mass-dependent fit results in a resonance mass of 1593±8_-47⁺²⁹ MeV/c² and a width of 168±20_-12⁺¹⁵⁰ MeV/c²

[en] The ηπ^- system has been studied in the reaction π^-p→ηπ^-p at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The a₂(1320) is observed in the J^PC=2⁺⁺ wave, as is a broad enhancement between 1.2 and 1.6 GeV/c² in the 1^-+ wave. The observed phase difference between these waves shows that there is phase motion in addition to that due to a₂(1320) decay. The data can be fitted by interference between the a₂(1320) and an exotic 1^-+ resonance with M=(1370±16⁺⁵⁰_-30) MeV/c² and Γ=(385±40 ⁺⁶⁵_-105) MeV/c² . copyright 1997 The American Physical Society

[en] A cylindrical multiwire drift chamber with axial charge-division has been constructed and used in experiment E852 at Brookhaven National Laboratory. It serves as a trigger element and as a tracking device for recoil protons in π^-p interactions. We describe the chamber's design considerations, details of its construction, electronics, and performance characteristics. (orig.)

[en] A 3045 element lead glass calorimeter and an associated fast trigger processor have been constructed, tested and implemented in BNL experiment E852 in conjunction with the multi-particle spectrometer (MPS). Approximately, 10⁹ all-neutral and neutral plus charged triggers were recorded with this apparatus during data runs in 1994 and 1995. This paper reports on the construction, testing and performance of this lead glass calorimeter and the associated trigger processor. (orig.)

[en] A partial-wave analysis of the reaction π^-p→π⁺π^- π^-p at 18 GeV/c has been performed on a data sample of 250000 events obtained by Brookhaven experiment E852. The expected J^PC=1⁺⁺a₁(1260) , 2⁺⁺a₂(1320) , and 2^-+π₂(1670) resonant states are clearly observed. The exotic J^PC=1^-+ wave produced in the natural parity exchange processes shows distinct resonancelike phase motion at about 1.6 GeV/c² in the ρπ channel. A mass-dependent fit results in a resonance mass of 1593±8⁺²⁹_-47 MeV /c² and a width of 168±20⁺¹⁵⁰_-12 MeV /c² . copyright 1998 The American Physical Society

[en] Events of the type π^-p→nηπ⁺π^- and π^-p→nηπ⁰ at 18GeV/c are analyzed. The mass and width of the neutral and charged a₀(980) were determined. The neutral a₀ is found to have a mass of (0.991±0.0025)GeV/c² and a width of (0.069±0.011)GeV/c². A partial wave analysis technique yields (0.9983±0.0040) and (0.072±0.010)GeV/c² for the mass and width of the charged a₀. copyright 1998 The American Physical Society

[en] Two prototype lead glass calorimeters have been constructed and tested at the AGS at Brookhaven National Lab. The first is a 25-element prototype (P1) which was tested in the A2 beam line using electrons and pions ranging in energy from 0.5 to 5.0 GeV. Results were obtained on energy resolution, the effect on energy resolution of pre-radiators and non-normal incidence, and on e/π separation. The second prototype (P2) has 319 elements and was tested in the A3 beam line using 3.0 and 5.0 GeV electrons and 15.0 GeV negative pions. Results were obtained on position resolution and effective mass resolution. Data were collected requiring multi-photon signatures in the calorimeter. The design, construction, monitoring, readout electronics (including a custom-built fast-encoding ADC system) and testing of the prototypes are described. These calorimeters are prototypes for a 3053-element lead glass calorimeter being built for Brookhaven Experiment 852: A search for mesons with unusual quantum numbers. Quality control procedures are also discussed. (orig.)