Beam-beam design criteria for LHC

The nominal parameters of the LHC were chosen such as to 
provide simultaneously a luminosity of 10**34 cm-2s-1 in two
diametrically opposite experiments,around 10**32 in a third 
experiment and around 10**30 in a fourth one.The total beam-
beam tune spread(between 0 and 6 sigma amplitude particles)
is limited to 0.01 in these conditions.However,the machine 
components were designed with just enough safety margin to
allow operation with a beam intensity(and a resulting beam-
beam tune spread)1.5 times larger than nominal.
The beams cross at an angle of +-150 micro rads in order 
to keep the contribution of the long range parasitic 
interactions to the tune spread below 25%.