R.N. Krasnokutsky

Absorption cross sections for pions, kaons, protons, and antiprotons on complex nuclei in the 6 to 60 GeV/c momentum range

Absorption cross sections for pi /sup plus or minus /, K/sup plus or minus mesons, protons andantiprotons on Li, Be, C, Al, Cu, Sn, Pb and V in the momentum range from 6.65 to 60 GeV/c are measured at the 70 GeV IHEP accelerator. The cross sections are compared with calculations using the Glauber multiple- scattering model. Nucleus radii are found to be described by a power dependence on atomic weight R = r/sub o/A/sup 1/3/, where r/sub o/= 1.05 plus or minus 0.02 fm. (auth)

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.

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)°.

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.

The measurement of the spatial coordinates of high energy photons with a scintillation hodoscope spectrometer

Abstract A scintillation counter hodoscope was used to study the characteristics of electromagnetic showers with energies up to 40 GeV. The energy release in the shower is found to decrease exponentially with distance from the axis of the shower and to be localized within a radius of 1 cm. The position of the photon at the face of a scintillation counter hodoscope spectrometer can be determined with an accuracy of a few millimeters, using the center of gravity of the amplitudes from the counters.

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.

Particle identification in a hodoscope Cherenkov spectrometer

Abstract A method was proposed and studied experimentally to separate hadrons and photons (electrons) in a hodoscope spectrometer, which is based on the difference of the transverse dimensions of hadron and electromagnetic showers.

Measurements of π− p → πo n reaction cross-section in the momentum range up to 50 GeV/c

Abstract Cross-section data are presented for pion proton charge-exchange scattering in the momentum range 20 to 50 GeV/ c . The experiments were performed at 70 GeV IHEP accelerator.

High resolution differential Čerenkov counters

Abstract The paper describes differential Cerenkov counters detecting Cerenkov light at the angles of 23 and 12 mrad. The counter lengths are 5 m (θ = 23 mrad) and 10 m (θ = 12 mrad). The spectrum band of the counters is 2500–6000 A. The counter characteristics have been investigated in 35 to 45 GeV/c beams of the 70 GeV accelerator. The velocity resolutions measured are equal to 2×10−6 for a 10 m counter and 6×10−6 for a 5 m counter. The 10 m counter can separate pions and kaons up to 200 GeV/c and kaons and protons (antiprotons) up to 350 GeV/c.