The ZEUS Micro-Vertex Detector

The ZEUS experiment has installed a silicon detector for the HERA-II running period. In fig.52 a sketch of the barrel region of the ZEUS micro vertex detector (MVD) is shown [235]. The barrel detector is made up of three layers each consisting of two single sided silicon strip wavers glued together back-to-back with perpendicular strip orientation. It provides a hit resolution of 7.5 $\mu$m and a hit efficiency of larger than 95%. The barrel detector is complemented with a forward micro-vertex detector which consists of 4 planes (wheels) perpendicular to the beam axis. The MVD system provides a polar angular coverage for charged tracks coming from the $ep$ interaction point between $10^{\circ}$ and $150^{\circ}$.

Figure: Display of the barrel of the ZEUS Microvertex Detector (MVD) in the $r$-$\phi$ and $r$-$z$ view (taken from [235]).

Figure 53 shows the impact parameter distribution of muon tracks in a dijet event sample recorded in the years 2003 and 2004. The solid line indicates the number of entries in the corresponding bin for negative values on the negative side of the $\delta$ distribution. The difference between the points and the solid line shows the lifetime effect. The corresponding distribution based on HERA-I data from the H1 experiment was shown in fig.15 in section 5.5.1.

Figure: Impact parameter distribution of muon tracks in $\mu +$dijet events as measured by ZEUS using data recorded in 2003 and 2004.