G. Di Cosimo

Construction and performance of the lead-scintillating fiber calorimeter prototypes for the KLOE detector

The KLOE detector is designed primarily for the study of direct CP violation in K0 decays. The electromagnetic calorimeter, EmC, is a most demanding element of the detector. Two prototypes of the EmC (one for the barrel and one for the end-cap region) have been built at Frascati and tested at PSI (Switzerland) using beams of electrons, muons and pions of 40 to 290 MeV/c momentum, and at the Frascati LADON facility using photons of 20 to 80 MeV. We observe excellent linearity from 20 to 290 MeV. The energy resolution is σ(E)/E ∼ 4.4% / ”E(GeV) and the time resolution is ∼ 34 ps/”E(GeV). We found little dependence on incidence angle and entry position. We also determined that some πμ identification is possible.

Measurements of light yield, attenuation length and time response of long samples of “blue” scintillating fibers

Abstract In connection with the design of the electromagnetic calorimeter of the KLOE detector, we have studied the performance of several samples of commercially available plastic scintillating fibers with a particle beam at the CERN PS. Results on light yield, attenuation length and time resolution measurements concerning 2–4.5 m long samples of those fibers are presented.

Scattering of thermal photons by a 46 GeV positron beam at LEP

Abstract The scattering of thermal photons present in the vacuum pipe of LEP against the high energy positron beam has been detected. The spectrum of the back-scattered photons is presented for a positron beam energy of 46.1 GeV. Measurements have been performed in the interaction region 1 with the LEP-5 experiment calorimeter.

Fast measurement of luminosity at LEP by detecting the single bremsstrahlung photons

Abstract Luminosity and beam angular divergence have been measured at LEP with a fast monitor based on the single bremsstrahlung process e + e − → e + e − γ. The photons emitted at the interaction point 1 are detected by an electromagnetic calorimeter: both the photon energy and the impact point are measured. The beam angular divergence and the luminosity are determined in few minutes with a statistical error of 1%. With the present experimental layout the systematic error is of few percent; it would be reduced by performing the measurement on an experimental interaction point.

Performance of fine mesh photomultiplier tubes in magnetic fields up to 0.3 T

We have studied the performance of fine mesh photomultiplier tubes (R2490-05, R2021, H5756, R3423-01) in magnetic fields up to 0.3 T. The tube gain and the average number of photoelectrons have been measured as a function of the magnetic field, of the angle between the field direction and the phototube axis, and of the rotation of the phototube around its axis. The reduction of the photocathode effective area in a magnetic field has also been measured.

Fast luminosity monitor at LEP

In 1990 the LEP-5 experiment measured luminosity at LEP by detecting the single bremsstrahlung photons emitted in the e+e− collisions. In 1991 the experiment was upgraded to exploit the intrinsic high speed of the method which allows luminosity measurement of the single bunches of LEP. In this paper the LEP-5 upgrade is described and the results of a test performed are discussed.

Performance of a highly segmented scintillating fibres electromagnetic calorimeter

Abstract A prototype of scintillating fibres electromagnetic calorimeter has been constructed and tested with 2, 4 and 8 GeV electron beams at the CERN PS. The calorimeter modules consist of a Bi-Pb-Sn alloy and scintillating fibres. The fibres are parallel to the modules longer axis, and nearly parallel to the incident electrons direction. The calorimeter has two different segmentation regions of 24 × 24 mm 2 and 8 × 24 mm 2 cross area respectively. Results on energy and impact point space resolution are obtained and compared for the two different granularities.

Thermal neutron radiation damage on light yield and attenuation length of scintillating fibres

Samples of blue scintillating fibres have been irradiated with thermal neutrons. The light yield and the attenuation length have been measured for a total integrated flux ranging from 3 to 60×1013 neutrons cm−2, and for two different fluxes (3.5 and 35×109 neutrons cm−2 s−1). The long term damage has been investigated for 2 m long samples with uniform irradiation along the fibre. Sizable deteriorations both in light yield and in attenuation length are found even at our lowest integrated neutron flux.

Space resolution obtained with a highly segmented SCIFI e.m. calorimeter

Abstract During the setting up of the LEP-5 experiment, we tested a longitudinal SCIFI e.m. calorimeter, having a module cross area 25 × 25 mm 2 and 12.5 × 12.5 mm 2 for large and small modules respectively. The results were obtained with 10 and 50 GeV electrons, and concern the impact point resolution and the transverse distribution of the e.m. shower energy inside the calorimeter.

Quality checks and first calibration of the KLOE electromagnetic calorimeter

Abstract The construction of the KLOE lead-scintillating fibres electromagnetic calorimeter has been completed. The final results of the extensive quality checks of all the calorimeter modules are presented here. The measurements have been done in the Frascati Laboratories at a cosmic ray test facility using minimum ionizing particles. The results show that all the calorimeter modules are well fulfilling the design specifications concerning time and energy resolutions. Furthermore, by using the same cosmic ray facility, all the calorimeter elements have been also pre-calibrated.