1. Beam-Gas Inelastic scattering in CEPC partial double ring
Sha Bai
CEPC AP meeting

2. CEPC beam loss effect on beam lifetime

3. Beam-Gas Inelastic scattering
We have to deal with two effects:
Bremsstrahlung scattering, where the particle emits a photon (and the nucleus is left unexcited).
Inelastic scattering from an electron of the atom in which the momentum transfer excites the atom.
Bremsstrahlung scattering at the nucleus:
The total differential cross section is given by the sum of both contributions:
Inelastic scattering off the electrons of the residual gas atom:

4. Beam-Gas Inelastic scattering generated events
Generator model:
particles energy change but direction no change.
Generate particles
~ energy spread

5. Lost particles statistic
Events generated in each ~1m region , tracking for one turn in SAD
Lost particles statistic in ~200m
Paticles lost little near IP region
Most particles lost in upstream
Put in detector to do next analysis

6. Conclusions and Prospects
Beam-Gas Inelastic scattering events are generated and lost particles information got after tracking in SAD.
With 1.7cm radius beam pipe aperture in final doublet, the lost particles after tracking in one turn upstream of IP1 are quite little near IP region.
Put lost particles in the detector and do simulation.