The ALEPH detector at LEP is used to study single photon events in e+e- collisions at the Z resonance. In a total data sample of 15.7 pb-1 taken in 1990 and 1991 scanning the resonance, 400 events were recorded where each has a single deposition of more than 1.5 GeV measured in the polar angular region \costheta(gamma)\ < 0.74 of the electromagnetic calorimeter. It is shown that this number of events can be accounted for by known processes. After subtraction of background events, the invisible width of the Z is determined to be 450 +/- 34(stat.) +/- 34(syst.) MeV. Using Z resonance parameters derived by ALEPH, the corresponding number of light neutrino generations is found to be 2.68 +/- 0.20(stat.) +/- 0.20(syst.).
|Autori interni:||CREANZA, Donato Maria|
MAGGI, Giorgio Pietro
|Titolo:||A DIRECT MEASUREMENT OF THE INVISIBLE WIDTH OF THE Z FROM SINGLE-PHOTON COUNTING|
|Rivista:||PHYSICS LETTERS. SECTION B|
|Data di pubblicazione:||1993|
|Digital Object Identifier (DOI):||10.1016/0370-2693(93)90027-F|
|Appare nelle tipologie:||1.1 Articolo in rivista|