Ma Giorgi

Flavor physics of leptons and dipole moments

This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

The ALEPH minivertex detector

Abstract Vertex detectors allow high precision reconstruction of particle tracks and therefore make possible the investigation of the decay topology of short-lived particles in collider experiments. In the ALEPH experiment at LEP a minivertex detector will be installed. It consists of silicon microstrip detectors arranged on two concentric “cylindrical” surfaces around the interaction point. With this geometry it will be possible to measure the r − ϕ − z coordinates of particles traversing the detector. The expected position resolution is 10 μm in r − ϕ and 20 μm in r − z . For optimum signal processing monolithic CMOS readout electronics are under development. Each chip consists of 60 charge sensitive preamplifiers, multiplexed into one output channel. Fast power switching will reduce heat dissipation. Details about construction and expected device performance will be described.

Pion-deuteron coherent scattering at high-energy

Abstract The differential cross-section for π − d elastic scattering has been measured at 9.0, 13.0, and 15.2 GeV/ c for t -values up to 2.3 GeV 2 . The results are analysed by comparison with the Glauber scattering model.

ELASTIC SCATTERING OF PROTONS ON DEUTERONS AT HIGH ENERGY.

Abstract The differential cross-section for pd elastic scattering has been measured at 9.7, 12.8 and 15.8 GeV/ c for t -values up to −2 GeV 2 . The Glauber multiple scattering model has been used to analyse the data, the main interest being the double scattering region.

Test results on double sided readout silicon strip detectors

Several 5*5 cm/sup 2/ double-sided readout silicon strip detectors have been fabricated using planar technology. Electrical characteristics (I-V and C-V curves interstrip resistance versus bias voltage) have been measured. Some detectors have been tested with a scanning electron microscope to investigate defects due to the fabrication process. A few of them have been tested with a beta source and with a 50-GeV electron beam. A strong correlation is observed between charges collected on the ohmic side and on the junction side. Preliminary results on capacitive charge division studies are also presented. >

The total cross section for π+ electroproduction on hydrogen near threshold

Abstract The total cross section for the reaction ep → enπ+ at momentum transfers |k2| between 0.08 and 0.32 ( GeV c )2 and for centre of mass energies between threshold, at W = 1.078 GeV, and W = 1.106 GeV has been measured by detecting the electron and neutron in coincidence. Comparisons are made with both current algebra and dispersion relation theoretical models.

Pion-Deuteron coherent scattering at 895 MeV/c

Abstract The elastic scattering cross-section of π - on deuterium at 895 MeV/ c measured with counters and wire spark chambers is given in a region of momentum transfer between 0.16 and 0.96 (GeV/ c ) 2 .

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.

Elastic electron-proton scattering between 0.05 and 0.30 (GeV/c)2

Abstract Elastic electron proton scattering has been used to check the validity of the dipole fit of the proton form factors at momentum transfer between 0.05 and 0.30 (GeV/ c ) 2 . The general behaviour of the cross sections is in agreement with previous measurements and is close to the dipole predictions but there is the suggestion of some small amplitude deviations. It is speculated that these deviations may be related to similar effects in the proton formfactor derived from the ISR pp elastic scattering data via a Chou-Yang model.

On the separation of the elastic component in double-scattering collisions of high-energy hadrons in deuterium

Abstract In connection with an experiment on hadron-deuteron elastic scattering at high energy, we analyze the problem of selecting the elastic events xd → xd from the inelastic events xd → xpn. When this last reaction is contributed by double-scattering collisions, the proton is expected to have kinematics similar to those of the elastic deuteron. We apply the multiple scattering model to work out angle and momentum distribution both for the scattered hadron and the recoil proton. Also, we discuss some of the features of the model separately, for the two cases in which either single- or double-scattering collisions are predominant: the double-scattering process at variance with the single scattering one is well described as two successive collisions on two free nucleons. We show that for a given scattering angle of the hadron the proton from the inelastic double-scattering reaction is distributed around a cone of ≈ 10°, so that the selection of the elastic deuteron events can be achieved on the basis of the angular correlation between the scattered hadron and the recoil charged particle. We compare some of the distributions with the ones obtained experimentally for 9 GeV/ c negative pions.