First collisions occured on 17.4.2002 with 35 mA p and 3 mA e+
Hans-Christian Schultz-Coulon found the first DIS candidate, see HyperNews:
Claus Kleinwort analyzed the z-vertex distribution:
(The z axis is inverted such that protons enter from the right).
The peak around 0 is due to ep collisions.
The continuous background is due to beam-gas interactions.
The peaks at -z=80 and 150 cm are due to interactions with the
fixed synchrotron radiation (1 cm tungsten, coated with Ag and Cu)
at these positions.
They are either caused by off-momentum particles
that scattered several meters upstream, or due to beam halo particles.
In the first case better vacuum will help, in the second the proton
and positron collimators and scrapers might help.