Setup of a Drift Tube Muon Tracker and Calibration of Muon ...

zyI 1I 2d Ixµ 2µ 1Figure 5.24: Example of relative positions of the reconstruction of a muon track byboth the CMT and Borexino in the coordinate system of the SSS. I is the impactparameter of each track. For the determination of the lateral resolution, the distanced I (green line) between the points closest to the center for each track is calculated.trackings does not take into account their relative position. To study this effect, theclosest point to the center of the SSS of the tracks reconstructed by Borexino andthe CMT have been determined as shown in Fig. 5.24 and the distances d I betweenthem have been calculated. The distribution of d I is depicted in Fig. 5.25 for theBorexino global tracking. A clear peak can be seen with a mean value of ¯d I givinga measure of the lateral resolution. All methods lead to a lateral resolution around50 cm with the results using the impact parameter comparison being slightly betterand more consistent than the other ones.5.5 CNGS Rock MuonsThe CMT is based on the drift tube technology developed for the OPERA detector.OPERA searches for ν τ appearance in a ν µ beam [79]. The CNGS 2 ν µ -beam isgenerated as described in Section 2.4.6 at a distance of 732 km from Gran Sasso atCERN, focused on the Hall C where both OPERA and Borexino are located. Thebeam travels through the Earth before it arrives at Gran Sasso at an inclinationof approximately -3.5 ◦ [80]. Neutrinos in the CNGS beam have a mean energy of17 GeV. Although the cross section for neutrino interactions is rather small, some2 CNGS CERN Neutrinos to Gran Sasso91