R.S. Shuvalov

Determination of photon coordinates in a hodoscope cherenkov spectrometer

Abstract The characteristics of a hodoscope (cell-type) Cherenkov spectrometer made of TF-1 lead glass have been studied in a 25 GeV electron beam. It is shown that with cell dimensions of about 3.5 cm one can achieve an accuracy of about 1.5 mm in measuring the coordinates of high energy photons. The experiments are a continuation of analogous investigations performed earlier with a spectrometer made of TF-5 lead glass.

Energy dependence of π−, K− and p to tal cross-sections on protons in the momentum range up to 65 GeV/c

Abstract π − p , K − p and p p total cross-sections are measured at momenta up to 65GeV/ c with statistical accuracy 0.3 ÷ 0.6% and systematical (scale) error ≈ 0.4%.

Reaction π−p→ηn in the 15 to 40 GeV/c momentum range

A high statistics measurement of the reaction π−p → π0n has been performed at the Serpukhov accelerator for 15, 20, 25, 30 and 40 GeV/c incident pion momentum using the NICE set-up with its associated 648-channel hodoscope spectrometer for γ-ray detection. More than 3 million charge-exchange events have been recorded in total. It is found that the spin-flip and non-spin-flip amplitudes can be parametrized, for small |t|, as exponentials with the same slopes to within a few percent. Also the behaviour of the differential cross section for small and medium |t| agrees with the prediction of a geometrical s-channel model which describes binary reactions in terms of a complex pole b0(s). The imaginary part of this universal pole, Im b0(s), has been determined and found to be growing logarithmically with s.

Reaction π− p → η′n in the 15–40 GeV/c momentum range☆

Abstract Measurements were made of the cross section of the reactions π−p → ν′(958)n, η′ → 2γ at momenta at 15, 20, 25, 30 and 40 GeV/c. The experiment was carried out on the IHEP 70 GeV accelerator using the 648 channel hodoscope spectrometer NICE for γ-ray detection. A total of 6000 η′ mesons were recorded. A sharp drop is seen in the differential cross section for t → 0. The dependences of the differential cross sections for the π−p → η′n and π−p → η n on t are identical. On the basis of the ratio of the cross sections for these reactions at t = 0, i.e. R( η′ n ) t=0 = 0.55 ± 0.06 , the singlet-octet mixing angle for pseudoscalar mesons was determined to be β = −(18.2 ± 1.4)°.

Negative particle production at the 70 GeV IHEP accelerator

Abstract Data are presented on the yields of π − , K − , and p produced at small angles by 70 GeV proton-aluminium interactions. The momenta of the secondaries studied were greater than 40 GeV/ c . Upper limits have been obtained on the production of antideuterons and possible new particles up to a mass of 2.2 GeV in this new energy region.

Further measurements on the production of π− and K− mesons and antiprotons at the 70 GeV IHEP accelerator

Abstract Measurements on the production of intermediate momenta negative pions, negative kaons, and antiprotons by protons of 43 GeV, 52 GeV and 70 GeV on aluminium nuclei are reported.

Observation of a spin 4 neutral meson with 2 GeV mass decaying in π° π°

Abstract The invariant mass spectrum of neutral meson states from π − p interactions at 40 GeV/ c incident momentum has been investigated in a high statistics experiment performed at the 70 GeV IHEP accelerator. To detect the high energy photons coming from the produced neutral states, a hodoscope spectrometer with a computer on-line was used. A clear structure on the mass spectrum of dipions produced in the reaction π − p→π°π°n is observed at 2 GeV. The decay angular distributions show in this mass region the variation with mass typical of a state with a spin J = 4. The mass of the observed meson is found to be M = (2020±30)MeV and the estimate of the full width is (180±60) MeV.

A hodoscope spectrometer for high-energy photons

Abstract A scintillation-counter hodoscope spectrometer developed at IHEP to detect high-energy photons is described. The detector can simultaneously measure the position (to 2 mm) and energy (5–10%) of several photons. The device is made with 648 scintillation counters, arranged to form hodoscopes and sandwiched between layers of iron converter. The useful area of the spectrometer is about 1 m 2 . Pulse-height analysis is performed on each of the 648 counters with 12-bit ADCs. Photon position is determined using the center of gravity of the shower amplitudes in the hodoscope counters. To eliminate ambiguities in multi-photon events, the showers are measured in three 120° projections. The total thickness of the spectrometer is 20 r.l. of steel in the beam direction. This provides total absorption of photons and electrons with an energy up to 1000 GeV. The characteristics of the spectrometer as used in experiments at the 70 GeV IHEP accelerator are described.

Production of antideuterons by 43 GeV, 52 GeV and 70 GeV protons

Abstract The production of antideuterons on aluminium nuclei by 43 GeV, 52 GeV and 70 GeV protons has been measured.

Analysis of the reaction π−p → π0ηn at 40 GeV/c beam momentum

The reaction π−p→π0ηn↳2y↳2y has been analyzed using data of an experimental performed at the 70 GeV accelerator, with the NICE 648 channel hodoscope spectrometer for γ ray detection. Events with 4γ seen are used for the analysis. A method is applied, which allows the determination of the number of π0η events for each mass, cosθGJ and t bin. Mass spectra, t distributions and decay angular distributions for the π0η system are presented. The cross section for the production of A20 is found to be 2.7 ± 1.1 μb at 40 GeV/c beam momentum. No indication of a resonant 1− state in the π0η system is observed, in spite of the fact that this state is allowed for the π0η system on the same footing as the observed 0+ and 2+ resonances.