M. Vivargent

Mean life of the neutral pion

High energy neutral mesons( rature of the d ) were produced in platinum foils of 3-60 micron thickness exposed to the 18-Bev internal proton beam of the CERN proton synchrotron, and the production of positrons relative to all heavier particles was measured in a secondary beam of 5-Bev/c. The momentum spectrum of rature of the d /sup o/, which is effective in producing 5Bev/c positrons, is obtained by weighting the rature of the d /sup o/ spectrum with the probability that a positron from a rature of the d /sup o/ has a momentum of 5-Bev/c. The momentum spectra of rature of the d /sup o/ and rature of the d /sup +/ are assumed to be of equal shape and the latter was measured. This effective rature of the d /sup o/ spectrum is narrow and is charactetized by an average momentum of 7.12-Bev/c and a rms momentum of 7.26-Bev/c. The mean life was determined to be (1.05 ction in DDT-C/ 0.18) x 10/sup -16/ sec. (C.E.S.)

A threshold gas Čerenkov counter

Abstract This note describes a type of conventional threshold gas Cerenkov counter, particularly well adapted for the use in high-energy beams. A very simple method has been found to obtain the best collection of the Cerenkov light. When utilized for the detection of 6 GeV/c electrons, its rejection against heavier particles is better than 10−4, and its efficiency better than 99 %.

Interference of KoL and KS amplitudes in the π+π- decay mode

Abstract The decay law of a coherent mixture of K o L and K o S has been measured over nine K o S mean lives in the π + π - mode. The relative phase between the interfering amplitudes was found to be ϕη +- ϕif 21 = (1.54 ±0.17) sign ( m L − m S ) rad and the K o L − K o S mass difference fΔm/Γ S ⋎ = 0.480 ± 0.024 .

SEARCH FOR DECAY OF NEUTRAL KAONS INTO CHARGED LEPTON PAIRS.

Abstract A search for decays of K L o and K S o into charged pairs is reported. No event has been found. Upper limits obtained with 90% confidence for the branching ratios are Λ (K L o → μ + μ − )/ Λ (K L o → all) −6 and Λ (K S o → μ + μ − )/ Λ (K S o → all) −5 .

Large aperture Čerenkov counter

Abstract Design and performance of a large, multi-cell treshold Cerenkov counter is described. Electrons from K 0 → e πν decays are detected with an efficiency of better than 0.99 over an angular range of ±50° in one plane and of ±15° in the other.

Experimental study of the ΔSΔQ rule in the time-dependent rate of Ko → πeν

Abstract The time-dependence of the decay rate of initially pure Ko into the final states ( π - e + ν) and (π + e - ν ) has been studied to investigate the validity of the ΔS ΔQ rule. In a sample of 4724 events no evidence for weak hadronic current with ΔS = − ΔQ is found. The ratio of the ΔS = ΔQmplitude and the ΔS = ΔQ amplitude is x = (0.04 ± 0.03) − i(0.06 ± 0.05).

Experimental study of the time-dependent rate of K0 → π+π−π0

Abstract The time-dependence of the decay rate of initially pure K 0 into the final state ( π + π − π 0 ) has been studied in search for the decay k S 0 → π + π − π 0 . No evidence is found in a sample of 384 observed events. The ratio of the CP -violating K S 0 amplitude and the K L 0 amplitude is η +−0 = (0.13 −0.20 +0.17 ) + i(0.17 −0.26 +0.27 ); the ratio of the CP -conserving K S 0 amplitude and the K L 0 amplitude is ∣ ϱ ∣ 0 → π + π − π 0 matrix element is found to be a +−0 = −0.31 ± 0.03.

Interference between KL0 and KS0 in the Kμ3 decay mode

Abstract The decay law of a coherent mixture of K L 0 and K S 0 has been studied in the K μ3 mode. The charge asymmetry is analysed as a function of the regeneration phase arg(i ƒ 21 ) and Re(ϵ). In addition arg(i ƒ 21 ) is estimated from recent measurements of K + and K − absorption cross sections in carbon.

Large-area wire spark chambers with two-coordinate read-out and ferrite core memory

Spark chambers with crossed wire planes and sensitive areas up to 240 x 130 cm 2 have been constructed for use in an electronics experiment at the CERN Proton Synchrotron. A two-coordinate read-out, which has the advantage of lower mass/cm 2 and compactness in space, has been achieved by special design of the high-voltage coupling, the ferrite core modules, and the read-out system. The spatial resolution for 1.5 mm wire spacing is ±0.5 mm and ±0.65 mm for the Iow- and for the high-voltage planes, respectively.

Production of an initially pure K0 beam of known momentum

Abstract Apparatus is described which selects electronically K + interactions in liquid hydrogen which produce K 0 in the reaction K + p→K 0 p π + . The directions of all 3 particles of the final state are measured in wire chambers. These measurements determine the K 0 production vertex and decay vertex and the K 0 momentum to a precision of ± 3 × 10 −2 , and thus the eigentime of K 0 . Calibration measurements using K 0 → π + π − decays are described. The apparatus has been designed for a study of the time dependent K 0 → π e v and K 0 → π + π − π 0 decay rates.