10 - H1 - Desy

42 The H1 experiment at HERA
y
θ
z
φ
x
p
e
SpaCal
Figure 3.3: The H1 detector with its major components and the reference system.
The right-handed reference frame at H1 is defined such that the positive z-axis points
into the proton direction, positive x-axis point horizontally to the centre of the storage
rings and positive y-axis points vertically upwards. The polar angle θ is measured with
respect to the z-axis and the azimuthal angle φ lies in the xy-plane, referred to as a
transverse plane, with φ = 0 indicating the x-axis. The radial distance r lays also in the