Modeling of the emittance growth due to decoherence in collision at the Large Hadron Collider

The transverse emittance growth rate of colliding hadron beams driven by external sources of noise is investigated based on existing analytical model as well as on macro-particle simulations and comparison to experimental data at the Large Hadron Collider (LHC). It is shown that an analytical description of the emittance growth rate neglecting the existence coherent beam-beam mode can nevertheless provide accurate estimate for operational conditions, featuring notably a high chromaticity. The model is used to investigate the level of noise experienced by the LHC beams. The results indicate that a significant reduction of the noise floor of the transverse feedback's beam position monitor is required for operation with a large beam-beam tune shift, as the one anticipated for the High Luminosity LHC (HL-LHC).