Search

The radiative decay Λ ( 1520 ) → Λ γ was measured directly in the study of the exclusive diffractive-like reaction p + N → Λ ( 1520 ) K + + N , Λ ( 1520 ) → Λ γ with the SPHINX spectrometer. The values of the branching and partial width of this radiative decay were obtained: BR [ Λ ( 1520 ) → Λ γ ] = ( 1.02 ± 0.21 ( stat ) ± 0.15 ( syst ) ) × 10 −2 and Γ [ Λ ( 1520 ) → Λ γ ] = 159 ± 33 ( stat ) ± 26 ( syst ) keV .

The design of the drift tubes with flat and with wire field shaping electrodes is described. The physical characteristics of the tubes are studied in the beam of Serpukhov accelerator. The optical measurements of wires displacements are made for a long (7.4 m) drift tube with wire field shaping. The comparison of two drift tube options is presented.

The inclusive cross sections of backward proton production in π − ( K − , p ) -Be, Al, Cu, Pb interactions at 40 GeV/ c are presented. Protons have been detected in the angular range 150°–165° and kinetic energy region 0.1–0.3 GeV. The invariant cross-section ratios for various beam particles are independent of the values of kinetic energy and of the nuclear target type: 〈ƒ K − /ƒ π − 〉= 0.87 ± 0.03 stat ± 0.03 syst , 〈ƒ p /ƒ π − 〉 = 1.82 ± 0.10 stat ± 0.05 syst . The A -dependence of the cross-section slope parameter for A ⩾27 is less than ∼2%.

Invariant mass spectrum of μ + μ − pairs produced by 70 GeV/ c protons in Be target are presented. Distinct enhancements in the mass regions of ϱ, ω mesons, φ meson and J/ψ particle are observed. For J/ψ production x and p ⊥ 2 distributions are given. The total cross section for the reaction p + Be → ( J ψ → μ + μ − ) + … is equal to 9.5 ± 2.5 nb/nucleus .

Total cross sections for π − , K − and p on protons and deutrons have been measured in the momentum range 15 to 60 GeV/c. Total cross sections for particle interactions with neutrons have been determined with an energy dependent Glauber correction. Using the positive particle data obtained earlier with the same experimental apparatus, the differences of total cross sections for particles and antiparticles as well as for particles belonging to the same isospin multiplet have been calculated. The differences of total cross sections for particles and antiparticles decrease with momentum following a power law. The differences between the pure isospin state cross sections are either close to zero or continue to decrease. The measured total cross sections and their differences are in agreement with relations predicted by quark and Regge-pole models.

The reaction π−p→Ks0Ks0n was studied at the incident momentum 40 GeV/c making use of the 6 m magnetic spark spectrometer MSS ITEP. Partial wave analysis was carried out using ∼ 6700 events of this reaction with t′

The performances of the TOF scintillation counters used in the SIGMA-AIAKS spectrometer are presented. The counters, made of NE110, are 150, 65 and 10 cm long, 10 cm wide and 1.5 cm thick. The time resolutions for minimum ionizing particles have been measured to be σ t = 0.18 ns, 0.14 ns and 0.11 ns respectively. The main contribution to the resolution is given by the photoe collection statistics determined by the decay time of the scintillator and the difference of the optical paths in the counter. The scintillation counters, assembled into hodoscopes of 1.5 × 3.2 m 2 and 0.65 × 0.8 m 2 are used for identification of particles through the TOF. The algorithms of off-line data processing are also presented.

About 7 × 10 3 events of Compton effect on pion in the reaction π − A → A π − γ st 40 GeV/ c were detected and for the first time the charged pion polarizability was obtained α π = (6.8 ± 1.4) × 10 −43 cm 3 .

The absorption cross sections of antideuterons with the momentum P = 13.3 GeV/c by Li, C, Al, Cu and Pb nuclei have been measured. Antiproton stripping of antideuterons has been registered and its cross section for C, Al and Cu has been defined. The binding energy of antideuteron is found to be ed = 2.4 ± 0.6 MeV by measuring the angular distribution of antiprotons from stripping.

Total cross-section data are presented for negative pions, kaons, and antiprotons on protons and deuterons in the momentum range 20 GeV/c to 65 GeV/c in 5 GeV/c steps.

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.

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%.

This paper describes a 5 m gas Cerenkov threshold counter with a velocity resolution δ = 6.5 × 10 −6 . Resolution of δ = = 3.6 × 10 −6 has been achieved as the result of summarizing the signals from two counters. High velocity resolution has been obtained due to the effective registration of Cerenkov light in the short-wave region (counter spectral range: 1800–6000 A). The threshold counter characteristics have been investigated in 5 to 60 GeV/c beams of the 70 GeV accelerator. The particle registration efficiency on the plateau is more than 99.99994%. The probability of the particle registration below the threshold is less than 3 × 10 −4 .

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)

The A -dependence of J/ψ inclusive production by 43 GeV/ c π − -mesons was measured to be σ = (18 ± 6) A (0.92±0.06) nb/nucleus for x > 0.

Results of the experimental study of inclusive φ meson production off berillium nuclei by 70 GeV/ c protons in the beam fragmentation region x > 0.41 are presented. Fitting of the measured differential cross sections to the forms d σ d x ∼ (1 − x) n x and d σ d p 2 t ∼ exp (−bp 2 t ) gives the parameters n = 6.0 ± 1.7 and b = (2.4 ± 0.7) (GeV/ c ) −2 . In the framework of a quark-parton model the measured φ meson x -distribution suggests that in the region of x > 0.41 nearly 90% of the φ mesons are produced via a strange sea quark fusion. The ratio of the OZI-forbidden and OZI-allowed transition coupling constants has been found to be ten times smaller than the same ratio calculated from the partial decay widths. The total inclusive cross section is estimated to be σ (pN → φ X) = (0.7 ± 0.2) × 10 −27 cm 2 .

d p and p d total cross-sections have been measured at 13.3 and 6.65 GeV/c respectively to check CPT-invariance. The standard transmission technique was used. The difference of d p and p d total cross-sections appeared to be equal 0.2 ± 2.6 mb. In addition d d and p p total cross-sections have been obtained. The experimental data allowed us to derive the total cross-section of antineutrons on protons, neutrons and deutrons.

The yields of pions, kaons, antiprotons and antideuterons, produced by the 70 GeV protons on Al and Be nuclei at the momenta 10 and 13.3 GeV/ c have been measured. Gas Cerenkov counters and time-of-flight spectrometers were used for particle identification.

The differential cross sections d σ d x and d σ d p t 2 of inclusive J/ψ production by 43 GeV/ c π − off Be, Cu and W nuclei have been measured. Fitting d σ d p t 2 ∼ A α (p t 2 ) we observed the increase of α with p t 2 .