======= FPCCDPixelhit ==========
A class represents one FPCCD pixel hit
PixelHit ID is given by ( layer, ladder, xi, zeta ).

xi and zeta are pixel address in a coordinate system local to a ladder. zeta is along Z axis, xi is in the ladder plain and eta is perpendicular to the plain of ladder.

cellID convension for FPCCD layer ID is from 0 to 5 ( for 6 layers configuration ) ladder ID is from 0 to ( number of ladders - 1 ), depending on the layer ID. Pixel IDs start from 0. (xi, zeta) is a local coordinate attached to a ladder. xi is coordinate along shorter axix of ladder zeta is coordinate along longer axis of ladder. the direction of xi axis is same as X axis of laboratory coordinate when a ladder is at phi=90 degree. the direction of zeta axis is same as Z axis of laboratory coordinate. the eta axis is perpendicular to a ladder. when phi=90 degree, it matched Y axis. The origin of local coordinate system, (xi, eta, zeta) is placed at the intersection of the line from IP and perpendicular to the ladder.

See also comment in FPCCDDigitizer::encodeFPCCDID(...)

Author

Akiya Miyamoto, KEK: 2010-04-19