  In the case of underground experiments for neutrino physics or rare event
searches, the background caused by cosmic muons contributes significantly and
therefore must be identified and rejected. We proposed and optimized a new
detector using liquid scintillator with wavelenghth-shifting fibers which can
be employed as a veto detector for cosmic muons background rejection. From the
prototype study, it has been found that the detector has good performances and
is capable of discriminating between muons induced signals and environmental
radiation background. Its muons detection efficiency is greater than 98$\%$,
and on average, 58 photo-electrons (p.e.) are collected when a muon passes
through the detector. To optimize the design and enhance the collection of
light, the reflectivity of the coating materials has been studied in detail. A
Monte Carlo simulation of the detector has been developed and compared to the
performed measurements showing a good agreement between data and simulation
results.

Instrumentation and Detectors;High Energy Physics - Experiment