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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

Higgs masses and widths from FeynHiggs [48–51] including dominant 2-loop corrections in the modified  scenario. a Higgs masses  (blue, dotted) and  (green, dashed). b Mass difference  (red) compared to total widths  (blue, dotted) and  (green, dashed). c Mass difference  divided by total width of h (blue, dotted), H (green, dashed) and sum of both widths (orange). d Ratio  for h (blue, dotted) and H (green, dashed)
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Fig3: Higgs masses and widths from FeynHiggs [48–51] including dominant 2-loop corrections in the modified scenario. a Higgs masses (blue, dotted) and (green, dashed). b Mass difference (red) compared to total widths (blue, dotted) and (green, dashed). c Mass difference divided by total width of h (blue, dotted), H (green, dashed) and sum of both widths (orange). d Ratio for h (blue, dotted) and H (green, dashed)

Mentions: Under variation of the input Higgs mass , the resulting masses and widths of the interfering neutral Higgs bosons h, H change as shown in Fig. 3 with results from FeynHiggs [48–51] including dominant 2-loop corrections. Figure 3(a) displays the dependence of the masses of h (blue, dotted) and H (green, dashed) on . Within the analysed parameter range of GeV, their mass difference (red) in Fig. 3b is around its minimum at GeV smaller than both total widths (blue, dotted) and (green, dashed). While decreases, increases with increasing . This is caused by a change of the predominantly diagonal or off-diagonal structure of the -matrix which has a cross-over around  GeV in this scenario. Since both widths contribute to the overlap of the two resonances, the ratio gives a good indication of the parameter region of most significant interference. This is visualised (in orange) in Fig. 3c and compared to the ratios (blue, dotted) and (green, dashed), which only take one of the widths into account and are therefore a less suitable criterion for the importance of the interference term. Figure 3d presents the ratio for (blue, dotted) and H (green, dashed) as a criterion for a narrow width. Both ratios lie in the range of about 0.5–, and this represents the expected order of the NWA uncertainty.Fig. 3


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

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

Higgs masses and widths from FeynHiggs [48–51] including dominant 2-loop corrections in the modified  scenario. a Higgs masses  (blue, dotted) and  (green, dashed). b Mass difference  (red) compared to total widths  (blue, dotted) and  (green, dashed). c Mass difference  divided by total width of h (blue, dotted), H (green, dashed) and sum of both widths (orange). d Ratio  for h (blue, dotted) and H (green, dashed)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig3: Higgs masses and widths from FeynHiggs [48–51] including dominant 2-loop corrections in the modified scenario. a Higgs masses (blue, dotted) and (green, dashed). b Mass difference (red) compared to total widths (blue, dotted) and (green, dashed). c Mass difference divided by total width of h (blue, dotted), H (green, dashed) and sum of both widths (orange). d Ratio for h (blue, dotted) and H (green, dashed)
Mentions: Under variation of the input Higgs mass , the resulting masses and widths of the interfering neutral Higgs bosons h, H change as shown in Fig. 3 with results from FeynHiggs [48–51] including dominant 2-loop corrections. Figure 3(a) displays the dependence of the masses of h (blue, dotted) and H (green, dashed) on . Within the analysed parameter range of GeV, their mass difference (red) in Fig. 3b is around its minimum at GeV smaller than both total widths (blue, dotted) and (green, dashed). While decreases, increases with increasing . This is caused by a change of the predominantly diagonal or off-diagonal structure of the -matrix which has a cross-over around  GeV in this scenario. Since both widths contribute to the overlap of the two resonances, the ratio gives a good indication of the parameter region of most significant interference. This is visualised (in orange) in Fig. 3c and compared to the ratios (blue, dotted) and (green, dashed), which only take one of the widths into account and are therefore a less suitable criterion for the importance of the interference term. Figure 3d presents the ratio for (blue, dotted) and H (green, dashed) as a criterion for a narrow width. Both ratios lie in the range of about 0.5–, and this represents the expected order of the NWA uncertainty.Fig. 3

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