Construction of the muon veto detector for the NA62 experiment

The rare decay K+ →π+νanti ν is an excellent process to study the physics of flavor because of its very clean nature. The NA62 experiment at the CERN SPS aims to collect about 100 K+ →π+νanti ν events in two years of data taking with a signal-to-background ratio of 10:1. To suppress events from the main decay channel K+ →μ+ν (BR = 68%), a nearly perfect muon-pion separation of 1:1011 is needed. The electromagnetic and hadronic calorimeters need to provide a muon suppression of 10-5. In the calorimeters, rare K+ →μ+ν events with a catastrophic energy loss of the muon are of particular concern. These events can only be separated from the signal by distinguishing electromagnetic showers from hadronic showers. For this, a muon veto detector (MUV) as a standard iron-scintillator sandwich calorimeter with fine segmentation is being constructed. Each scintillator strip is read out by wave length shifter (WLS) fibers. For the MUV construction, the quality of each of the 1100 scintillating strips is tested on an automatic test line. Several samples of WLS fibers and several PMTs have been tested. This talk reports about all the elements used in the construction of the detector and its main characteristics (scintillator properties, grove, gluing, wrapping, choosing WLS fibers and test of considered PMTs).