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Interference effects in BSM processes with a generalised narrow-width approximation.

Fuchs E, Thewes S, Weiglein G - Eur Phys J C Part Fields (2015)

Bottom Line: It is demonstrated that interference effects of this kind arising in BSM models can be very large, leading to drastic modifications of predictions based on the standard NWA.The generalised NWA, based on on-shell matrix elements or their approximations leading to simple weight factors, is shown to produce UV- and IR-finite results which are numerically close to the result of the full process at tree level and at one-loop order, where an agreement of better than [Formula: see text] is found for the considered process.The most accurate prediction for this process based on the generalised NWA, taking into account also corrections that are formally of higher orders, is briefly discussed.

View Article: PubMed Central - PubMed

Affiliation: DESY, Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany.

ABSTRACT

A generalisation of the narrow-width approximation (NWA) is formulated which allows for a consistent treatment of interference effects between nearly mass-degenerate particles in the factorisation of a more complicated process into production and decay parts. It is demonstrated that interference effects of this kind arising in BSM models can be very large, leading to drastic modifications of predictions based on the standard NWA. The application of the generalised NWA is demonstrated both at tree level and at one-loop order for an example process where the neutral Higgs bosons h and H of the MSSM are produced in the decay of a heavy neutralino and subsequently decay into a fermion pair. The generalised NWA, based on on-shell matrix elements or their approximations leading to simple weight factors, is shown to produce UV- and IR-finite results which are numerically close to the result of the full process at tree level and at one-loop order, where an agreement of better than [Formula: see text] is found for the considered process. The most accurate prediction for this process based on the generalised NWA, taking into account also corrections that are formally of higher orders, is briefly discussed.

No MeSH data available.


Related in: MedlinePlus

Example diagrams of the 2-body decays for a Higgs production in  at NLO and b Higgs decay in  at NLO with virtual and real corrections
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Fig11: Example diagrams of the 2-body decays for a Higgs production in at NLO and b Higgs decay in at NLO with virtual and real corrections

Mentions: The gNWA at NLO requires the 1-loop contributions to the 2-body decays as subprocesses. For the production, we calculate the full 1-loop corrections to in the NNN on-shell renormalisation scheme, see Refs. [56, 64, 65], with the same choice of on-shell states as in the 3-body-decay described in Sect. 8.1.1. Higgs mixing is taken into account by -factors, but mixing with G-/Z-bosons is generated explicitly, which, however, vanishes in this -conserving scenario. Some example diagrams for vertex corrections are shown in Fig. 11a. Figure 12a presents the resulting 2-body decay widths for the production of h (blue) and H (green) at the tree level (dashed) and the 1-loop level (solid). While the 1-loop corrections increase , they decrease the production of H from the decay of . The substantial relative effect can be seen in Fig. 12c.Fig. 11


Interference effects in BSM processes with a generalised narrow-width approximation.

Fuchs E, Thewes S, Weiglein G - Eur Phys J C Part Fields (2015)

Example diagrams of the 2-body decays for a Higgs production in  at NLO and b Higgs decay in  at NLO with virtual and real corrections
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4464706&req=5

Fig11: Example diagrams of the 2-body decays for a Higgs production in at NLO and b Higgs decay in at NLO with virtual and real corrections
Mentions: The gNWA at NLO requires the 1-loop contributions to the 2-body decays as subprocesses. For the production, we calculate the full 1-loop corrections to in the NNN on-shell renormalisation scheme, see Refs. [56, 64, 65], with the same choice of on-shell states as in the 3-body-decay described in Sect. 8.1.1. Higgs mixing is taken into account by -factors, but mixing with G-/Z-bosons is generated explicitly, which, however, vanishes in this -conserving scenario. Some example diagrams for vertex corrections are shown in Fig. 11a. Figure 12a presents the resulting 2-body decay widths for the production of h (blue) and H (green) at the tree level (dashed) and the 1-loop level (solid). While the 1-loop corrections increase , they decrease the production of H from the decay of . The substantial relative effect can be seen in Fig. 12c.Fig. 11

Bottom Line: It is demonstrated that interference effects of this kind arising in BSM models can be very large, leading to drastic modifications of predictions based on the standard NWA.The generalised NWA, based on on-shell matrix elements or their approximations leading to simple weight factors, is shown to produce UV- and IR-finite results which are numerically close to the result of the full process at tree level and at one-loop order, where an agreement of better than [Formula: see text] is found for the considered process.The most accurate prediction for this process based on the generalised NWA, taking into account also corrections that are formally of higher orders, is briefly discussed.

View Article: PubMed Central - PubMed

Affiliation: DESY, Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany.

ABSTRACT

A generalisation of the narrow-width approximation (NWA) is formulated which allows for a consistent treatment of interference effects between nearly mass-degenerate particles in the factorisation of a more complicated process into production and decay parts. It is demonstrated that interference effects of this kind arising in BSM models can be very large, leading to drastic modifications of predictions based on the standard NWA. The application of the generalised NWA is demonstrated both at tree level and at one-loop order for an example process where the neutral Higgs bosons h and H of the MSSM are produced in the decay of a heavy neutralino and subsequently decay into a fermion pair. The generalised NWA, based on on-shell matrix elements or their approximations leading to simple weight factors, is shown to produce UV- and IR-finite results which are numerically close to the result of the full process at tree level and at one-loop order, where an agreement of better than [Formula: see text] is found for the considered process. The most accurate prediction for this process based on the generalised NWA, taking into account also corrections that are formally of higher orders, is briefly discussed.

No MeSH data available.


Related in: MedlinePlus