A. Stefanini

A Measurement of the Space - Like Pion Electromagnetic Form-Factor

Abstract The pion form factor has been measured in the space-like q 2 region 0.014 to 0.26 (GeV/ c ) 2 by scattering 300 GeV pions from the electrons of a liquid hydrogen target. A detailed description is given of the apparatus, data analysis and corrections to the data. The mean square charge radius extracted from the data is model-dependent. We find that a form which includes a realistic description of the form factor phase gives a similar results to the naive pole form, and conclude 〈r 2 π 〉 = 0.438±0.008 fm 2 .

A measurement of the pion charge radius

Abstract We report a measurement of the negative pion electromagnetic form factor in the range of space-like four-momentum transfer 0.014 q 2 c ) 2 . The measurement was made by the NA7 collaboration at the CERN SPS, by observing the interaction of 300 GeV pions with the electrons of a liquid hydrogen target. The form factor is fitted by a pole form with a pion radius of 〈r 2 〈 1 2 = 0.657 ± 0.012 fm.

Measurement of the pion form factor in the time-like region for q2 values between 0.1 (GeV/c)2 and 0.18 (GeV/c)2

Abstract The EM form factor of the pion has been studied in the time-like region by measuring σ (e + e − → π + π − ) normalized to σ (e + e − → μ + μ − ). Results have been obtained for q 2 down to the physical threshold.

A MULTI-ELECTRODE SILICON DETECTOR FOR HIGH-ENERGY EXPERIMENTS

Abstract A detector has been developed in our laboratory for proposed use in high energy experiments. It works as a MWPC in which the ionizing medium consists of a thin layer of silicon crystal. The results of the test carried out at CERN show that the detector is ideally suited for the detection of minimum ionizing particles and can provide very high spatial resolution.

Electronic measurement of the lifetime of D± mesons

Abstract Charmed meson pairs have been photoproduced coherently on an active silicon target. Ninety-eight decays have been analyzed and the lifetime of charged Ds has been measured.

Construction and performance of a silicon target for the decay-path measurement of long-lived mesons

Abstract A telescope made up of thin silicon detectors was built and used as a live target in a high-energy photoproduction experiment at the CERN Super Proton Synchrotron. Its working principles, construction technique, and the results of tests are reported. This telescope will allow measurement of the decay path in the range 300–10000 μm.

A new fast and programmable trigger logic

Abstract The NAl (FRAMM) experiment, under construction for the CERN-SPS North Area, deals with more than 1000 counter signals which have to be combined together in order to build sophisticated and highly selective triggers. These requirements have led to the development of a low cost, combinatorial, fast electronics which can replace, in an advantageous way, the standard NIM electronics at the trigger level. The essential performances of the basic circuit are: 1. 1) programmability of any desired logical expression; 2. 2) trigger time independent of the chosen expression; 3. 3) reduced cost and compactness due to the use of commercial RAMs, PROMs, and PLAs; 4. 4) short delay, less than 20 ns, between input and output pulses.

First measurement of the reaction π−e → π−π0e

Abstract The first observation of neutral pion production in π e inelastic scattering is presented. The cross section at 300 GeV for | t ‖>62;10 −3 (GeV / c ) 2 is 2.11 ± 0.47 nb, in good agreement with the theory of PCAC anomalies with 3 quark colours.

Λ c Photoproduction and lifetime measurement

A measurement of the lifetime of theΛc baryon photoproduced coherently off a Germanium-Silicon target is presented. A signal ofΛc→ΔK*→pKππ0 has been observed and the two different decay diagrams for this process are compared. A sample of 9Λc decays gives a lifetime of 1.1−0.4+0.810−13 s.

A set of drift chambers built for the FRAMM-NA1 spectrometer

Abstract This paper describes the module of the drift chamber system used at CERN in a multiparticle magnetic spectrometer (FRAMM-NA1). Details are given about a new construction procedure which allows the quick and easy assembly of the chambers. Tests have been performed to check the construction accuracy, the detection efficiency and the final spatial resolutions, the results are reported. agger;