Interference effects of neutral MSSM Higgs bosons with a generalised narrow-width approximation

• Published in: Nuclear and particle physics proceedings Vol. 273-275; pp. 863 - 869
• Main Author: Fuchs, Elina
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2016
• Subjects: Higgs bosons; higher order corrections; MSSM; Narrow-width approximation; higher order corrections; Narrow-width approximation; Higgs bosons; MSSM
• ISSN: 2405-6014; 2405-6022; 2405-6022
• DOI: 10.1016/j.nuclphysbps.2015.09.133

Mixing effects in the MSSM Higgs sector can give rise to a sizeable interference between the neutral Higgs bosons. On the other hand, factorising a more complicated process into production and decay parts by means of the narrow-width approximation (NWA) simplifies the calculation. The standard NWA, however, does not account for interference terms. Therefore, we introduce a generalisation of the NWA (gNWA) which allows for a consistent treatment of interference effects between nearly mass-degenerate particles. Furthermore, we apply the gNWA at the tree and 1-loop level to an example process where the neutral Higgs bosons h and H are produced in the decay of a heavy neutralino and subsequently decay into a fermion pair. The h – H propagator mixing is found to agree well with the approximation of Breit-Wigner propagators times finite wave-function normalisation factors, both leading to a significant interference contribution. The factorisation of the interference term based on on-shell matrix elements reproduces the full interference result within a precision of better than 1% for the considered process. The gNWA also enables the inclusion of contributions beyond the 1-loop order into the most precise prediction.