The reaction K − p → ηη(Λ/Σ0) at a momentum of 32.5 GeV/c was studied for the first time. The experiment was performed by using the GAMS-4π spectrometer at the 70-GeV accelerator of the Institute for High Energy Physics (IHEP, Protvino). The f 2(1525) resonance was observed in the effective-mass spectrum of the ηη system at a low background level. The cross section for f 2(1525) production was measured. The branching ratio for f 2(1525)-meson decay to ηη and K \(\bar K\) was found to be R = 0.119 ± 0.015(stat.) ± 0.036(syst.), which is in agreement with the world-average value.

A search for the rare and forbidden neutral decays of eta-meson with the GAMS-4 pi setup has been performed. The charge-exchange reaction at 32.5 GeV/c was used as a source of 3.7 center dot 10(6) eta-mesons. At the 90% confidence level the following upper limits were obtained: BR(eta -> 3 gamma) < 1.6 center dot 10(-4), BR(eta -> 4 gamma) < 2.8 center dot 10(-4), BR(eta -> pi(0)pi(0)) < 3.5 center dot 10(-4); BR(eta -> pi(0)pi(0)gamma) < 1.7 center dot 10(-3), BR(eta -> pi(0)pi(0)gamma gamma) < 4.0 center dot 10(-3), BR(eta -> 3 pi(0)gamma) < 2.4 center dot 10(-4), BR(eta -> 4 pi(0)) < 2.0 center dot 10(-5).

The ηη system produced in charge-exchange π−p interaction at a momentum of 32.5 GeV/c is studied in an experiment performed with the GAMS-4π spectrometer at the 70-GeV accelerator of the Institute for High-Energy Physics (IHEP, Protvino). A partial-wave analysis is performed in the mass range between 1.1 and 3.9 GeV for −t <0.2 (GeV/c)2, S, D, G, and J waves being taken into account in this analysis. The S wave has a complicated structure, displaying peaks at about 1.5 and 1.7 GeV. These peaks are associated with the f0(1500) and f0(1710) mesons. One of the solutions (preferable one) involves the f0(2200) and f2(1950) resonances. The mass region above 2.4 GeV is dominated by the G wave. A broad state of mass about 3 GeV and width 0.7 GeV is found in the J wave. The parameters of the resonances in question and their production cross sections are measured.

A study has been made of the etaeta system produced in the pi(-)p charge exchange reaction at 32 GeV/c. The experiment was performed at the IHEP 70-GeV proton synchrotron with the GAMS-4pi spectrometer. A partial wave analysis has been carried out in the mass range from 1.1 to 3.9 GeV with -t < 0.2 (GeV/c)(2) including the waves S, D-0, D-, D+, G(0), G(-) and G(+). Three states are unambiguously observed in the S-wave: f(0)(1370) f(0)(1500), and f(0)(1710). The large accumulated statistic allows to resolve the G(1590) structure into two separate states the f(0)(1500) and the f(0)(17 10). Two states f(0)(2100) and f(2)(1950) are observed in one solution. The f(4)(2050) is seen in the G(0)-wave, A new spin 4 structure observed in the region above 2.7 GeV/c(2). This state needs further investigation due to the possible influence of a spin 6 state.

A new measurement of the F-18(p,alpha) reaction was undertaken in order to resolve previous contradictory results regarding the 7.07 MeV state in Ne-19. Recoil protons and a-particles were detected in the LEDA multistrip silicon detector. Consistent results were obtained for the resonance energy, resonance strength and total width.

A new measurement of the F-18(p,alpha) reaction and the F-18(p,p) elastic scattering was performed at the Radioactive Ion Beam facility in Louvain-la-Neuve. Values were deduced for the resonance energy, total width, partial width, and resonance strength of the 7.07 MeV level in Ne-19, confirming and increasing the precision of a first result obtained several years ago in the same lab.

The reaction N-13 + B-11 has been investigated at two 13N beam energies: 29.5 and 45 MeV, Charged particles and gamma rays emitted in the reactions have been detected using a large array of silicon strip detectors and BaF2 scintillators, respectively. Several reaction channels have been analysed with different aims.The proton transfer reaction B-11(N-13, C-12)C-12 to various excited states of C-12 has been studied to obtain information on the N-13(g.s.) structure.The excitation energy of the Mg-24 compound nucleus was in the region where several resonances occur in the C-12 + C-12 system. The six-alpha decay of the Mg-24 intermediate system has been studied. Some of these events have been identified as coming from the break-up of two C-12* in the 3(1)(-)-3(1)(-) and 3(1)(-)-0(2)(+) states.The total fusion cross section has also been extracted from the data. In order to extract information on the isospin purity/mixing in Mg-24 at high excitation energy (E-x similar to 47 MeV), the GDR gamma emission from this self-conjugate nucleus has been studied. A comparison of gamma spectra has been undertaken for the reactions N-13 + B-11 and N-14 + B-10. (C) 2001 Elsevier Science B.V, Ail rights reserved.

A new measurement of the ${}^{18}\mathrm{F}(p,\ensuremath{\alpha})$ reaction and the ${}^{18}\mathrm{F}(p,p)$ elastic scattering was performed at the Radioactive Ion Beam facility in Louvain-la-Neuve. Values were deduced for the resonance energy, total width, partial width, and resonance strength of the 7.07 MeV level in ${}^{19}\mathrm{Ne},$ confirming and increasing the precision of a first result obtained several years ago in the same lab.

The reaction π-p → ηπ0n at primary π- meson momenta of 32, 38, and 100 GeV/c has been studied by using the GAMS facilities. A partial-wave analysis has been performed in the effective-mass range 0.77 ≤ Mηπ0

The pi(0)pi(0) system produced in charge-exchange pi(-)p interactions at a primary momentum of 100 GeV/c has been studied. The data employed come from the experiment that was performed at the CERN SPS accelerator and which recorded photons from pi(0) decays with the aid of the hodoscopic multiphoton GAMS-4000 spectrometer. A partial-wave analysis of the pi(0)pi(0) system in the mass interval between 0.8 and 3 GeV has been performed with allowance for the S, D, G, and J waves. The S wave has a rather complicated structure, displaying a series of four bumps separated by three dips at about 1, 1.5, and 2 GeV. This suggests the existence of several scalar resonances. The higher waves show clear peaks corresponding to the f(2)(1270), f(4)(2050), and f(6)(2510) mesons, which are produced predominantly via one-pion exchange. The parameters of these mesons and their production cross sections have been determined.

A coupled channel analysis of the centrally produced K+K− and π+π− final states has been performed in pp collisions at an incident beam momentum of 450 GeV/c. The pole positions and branching ratios to ππ and KK of the f0(980), f0(1370), f0(1500) and f0(1710) have been determined. A systematic study of the production properties of all the resonances observed in the π+π− and K+K− channels has been performed. Submitted to Physics Letters 1 LAPP-IN2P3, Annecy, France. 2 Athens University, Physics Department, Athens, Greece. 3 School of Physics and Astronomy, University of Birmingham, Birmingham, U.K. 4 CERN European Organization for Nuclear Research, Geneva, Switzerland. 5 IHEP, Protvino, Russia. 6 IISN, Belgium. 7 JINR, Dubna, Russia. 8 High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan. 9 Faculty of Engineering, Miyazaki University, Miyazaki 889-2192, Japan. 10 RCNP, Osaka University, Ibaraki, Osaka 567-0047, Japan. 11 Oslo University, Oslo, Norway. 12 Faculty of Science, Tohoku University, Aoba-ku, Sendai 980-8577, Japan. Recently the WA102 collaboration has published the results of partial wave analyses of the centrally produced K+K− , K SK 0 S [1], π +π− [2] and ππ [3] channels. A striking feature of these analyses was the result that the fJ(1710) has J = 0 (we shall refer to it as the f0(1710) hereafter). In these papers the S-wave from each channel was fitted independently using interfering Breit-Wigners and a background. In this present paper we will first show how the resulting parameters change if a different method of fitting is used, namely, a TMatrix analysis and a K-Matrix analysis using the methods described in ref. [4]. Next we will perform a coupled channel fit to the K+K− and π+π− final states in order to determine the pole positions and branching ratios of the observed mesons. Finally we will present information on the production kinematics of these resonances. In our previous publication a fit has been performed to the π+π− S-wave using a coherent sum of relativistic Breit-Wigner functions and a background of the form: A(Mππ) = Bgd(Mππ) + Nres ∑

New results on meson spectroscopy that were obtained by the GAMS collaboration over the years 1997 and 1998 are presented. A partial-wave analysis of the pi(0)pi(0) system formed in charge-exchange pi(-)p interaction at a momentum of 100 GeV/c has been performed. The eta eta system produced in the reaction pi(-)p --> eta eta n at a momentum of 38 GeV/c has been studied. The results of a partial-wave analysis of the pi(0)pi(0) system formed in central proton-proton collisions at a momentum of 450 GeV/c have been discussed.

The reaction pi(-)p --> eta pi(0)n at primary pi(-) meson momenta of 32, 38, and 100 GeV/c has been studied by using the GAMS facilities. A partial-wave analysis has been performed in the effective-mass range 0.77 less than or equal to M-eta pi 0 < 1.82 GeV/c(2). A peak associated with the a(2) meson is clearly seen in the P+-wave. The difference of the D+- and P+-wave phases changes abruptly in the region of the a(2) mass. A significant contribution of the P+ wave is observed at the a(2) mass value and above, but this wave does not show a clear-cut resonance behavior. No significant contribution from exchanges of unnatural spin-parity are observed with the exception of the S-wave contribution in the region of the a(0) mass and the D-0-wave contribution in the region of the a(2) mass.