S.V. Sergeev

Measurements of the K+→π0e+ν form factors

Abstract The q2 dependence of the vector form factor has been investigated using 3.2 × 104 K+ → π0e+ν decays. The usual linear parametrization. ƒ + (q 2 ) = ƒ(0)(1+λ + q 2 /m π 0 0 ) gives λ+ = 0.0284±0.0027. An analysis of the Dalitz plot density distribution for Ke3+ decays yields the values for the scalar and tensor couplings ƒs and ƒt, and their relative phase angle ost.

Characteristics of a mini Drift chamber

Abstract The characteristics of a drift chamber with 3 mm drift gap were investigated at a particle beam momentum of 10 GeV/ c . The chamber has good linearity of the drift characteristics. It was tested and could reliably work in a particle flux of ∼ 3 × 10 5 s −1 cm −2 . A spatial resolution of ∼ 45 μm in the centre of the drift gap has been achieved.

A new upper limit for the branching ratio of the decay K0S → e+e−

Abstract A new value of the upper limit for the branching ratio of the decay of K 0 S into e + e − has been experimentally obtained using a lead glass detector. The value is BR (K 0 S → e + e − ) −4 (90% CL).

Electrodeless drift chamber in a flux of more than 105 particles per second per wire

Abstract Electrodeless drift chambers with drift lengths of 50 and 100 mm have been tested at a particle flux from 10 3 to 1.5 × 10 5 /s per wire. The efficiency remains high (>99%) up to a flux of 7 × 10 4 /s, but at a rate 1.5 × 10 5 /s it drops to 70%. The space-time linearity and spatial resolution do not change with the count rate. The recovery time after a high particle intensity is about 20 min. The characteristics do not change within many days of operation, even after large changes in the particle flux.

Reconstruction of the coordinate and energy of the electromagnetic shower in the lead-glass hodoscope calorimeter at different entrance angles of 5 GeV positrons

Abstract Energy deposition as a function of entrance angles and coordinates for 5 GeV e + is studied experimentally in 10×10×35 cm 3 blocks of the lead-glass shower hodoscope detector (SHD); the radiation length is X 0 = 2.5 cm. A method for the reconstruction of electromagnetic shower coordinates ( σ ⋍ 11 mm ) and energies ( σ E /E ⋍ 6% ) is developed for the positron entrance angles 0°–30°.

Characteristics of hadronic showers detected by Cherenkov radiation in lead glass

Abstract Spatial and energy characteristics of hadron showers were studied for the first time with the help of a total hadron absorption detector made from lead glass. The calorimeter model having a longitudinal and transverse hodoscopic structure with 10 cm step width is exposed to a particle beam of e + , μ + , π + , K + , p at 5, 10 and 13 GeV/ c . Data on the energy and coordinate resolution, hadron and electromagnetic shower separation have been obtained.

A-dependence of η-meson inclusive production at 10.5 GeV/c

Abstract The experimental results are presented for ratios of ν-meson inclusive differential cross sections in 10.5 GeV/c π+p, π+D and π+A collisions, RD/p=(dσ/dxF)(π+D→ηX)/ (dσ/dxF)π+p→ηX), RA=(dσ/dxF)(π+D→ηX) in the beam fragmentation region. The results are based on the statistics of ≈ 5 × 104 detected η → 2γ decays. It is shown that the power α in the parametrisation RA ≈ Aα(xf) does not change significantly with xF and its mean value is 0.50±0.02. The lower limit is obtained for the effective coefficient with string tension in the colour string model, κ ⩾ 3 GeV/fm. The observed growth of RA with xF can be explained by an assumption of a neutron halo with the factor H ≈ 4 in the nuclei.

Measurement of electromagnetic shower position with an electrodeless drift chamber

Abstract Spatial resolution of a lead-glass shower detector was considerably improved by means of a converter and an electrodeless drift chamber as a coordinate detector. The coordinate of an electromagnetic shower was measured without a flash ADC; only a multi-hit TDC was used. A spatial resolution of 1.95 mm (r.m.s.) at an energy of 3 GeV was achieved. The efficiency in a relatively high shower count rate was checked.

How to use electrodeless drift chambers in experiments at accelerators

Abstract Several types of wide-gap electrodeless drift chambers, including those with dimensions 1×1 m2, have been tested at accelerator beams. The chambers work with high efficiency (>99%), good spatial resolution (σ = 0.2−0.4 mm) and good linearity at flux rates up to 2×105 particles−1 per wire in spill, which corresponds to 3×106 particles/s m2 on colliders. It is shown that at the proper mode of operation beam intensity oscillations within the range of up to 4×105 particles/spill per wire do not affect the chamber efficiency.

Accuracy of electromagnetic shower position determination by a wide-gap drift chamber

The electromagnetic shower position was measured by a wide-gap drift chamber placed behind an active converter. Different methods for the shower-position determination based on MHTDC and flash ADC were used. A spatial resolution of 1.9 mm (rms) at an energy of 3 GeV and a converter thickness of 3X0 was achieved. The transverse charge distribution at different depths of the e.m. shower in the lead-glass was measured.