# Impact of CP-violating interference effects on MSSM Higgs searches

## TL;DR

This paper investigates how CP-violating interference and mixing effects between neutral Higgs bosons in the MSSM with complex parameters significantly influence LHC search interpretations, especially near degenerate states.

## Contribution

It demonstrates the importance of including interference effects in MSSM Higgs searches, revealing that neglecting them can lead to incorrect exclusion regions.

## Key findings

- Interference effects can be strongly destructive, reducing observable signals.
- Mixing increases individual Higgs production cross sections.
- Parameter regions previously considered excluded remain viable when interference is considered.

## Abstract

Interference and mixing effects between neutral Higgs bosons in the MSSM with complex parameters are shown to have a significant impact on the interpretation of LHC searches for additional Higgs bosons. Complex MSSM parameters introduce mixing between the CP-even and CP-odd Higgs states and generate CP-violating interference terms. Both effects are enhanced in the case of almost degenerate states. Employing as an example an extension of a frequently used benchmark scenario by a non-zero phase $\phi_{A_t}$, the interference contributions are obtained for the production of neutral Higgs bosons in gluon-fusion and in association with b-quarks followed by the decay into a pair of $\tau$-leptons. While the resonant mixing increases the individual cross sections for the two heavy Higgs bosons $h_2$ and $h_3$, strongly destructive interference effects between the contributions involving $h_2$ and $h_3$ leave a considerable parameter region unexcluded that would appear to be ruled out if the interference effects were neglected.