Speaker
Description
The interaction between a 120 GeV/c electron beam and a 4 mm thick lead tungstate scintillator was investigated at H4 beamline of SPS, in CERN North Area. The high Z target material was chosen in order to provide intense fields (E≈10^11 V/cm). In the beam rest frame, the internal electric fields are enhanced by a Lorentz factor. Thus, the effective field perceived by electrons exceeded Schwinger critical field limit (E0≈1.32x10^16 V/cm). In this condition, the electromagnetic shower process is supposed to be accelerated inside the medium. In this experiment, evidences of faster shower development were probed by measurements of the scintillation light produced by the crystal. A reflective coating was applied to the sample, a SiPM was coupled to the base of the sample to collect signal intensity. Measures were performed in condition of alignment with [001] axis and in condition on misalignment with major crystallographic axes and planes. A clear enhancement of scintillation light intensity was measured in case of axial alignment. This effect could prove of great interest for future electromagnetic calorimeters with improved features of signal intensity and maximum measurable energy, provided a flux of incoming particles with small angular spread (i.e. forward physics, astrophysics sources)
