5D perspective on Higgs production at the boundary of a warped extra dimension

Abstract

A comprehensive, five-dimensional calculation of Higgs-boson production in gluon fusion is performed for both the minimal and the custodially protected RandallSundrum (RS) model, with Standard Model fields propagating in the bulk and the scalar sector confined on or near the IR brane. For the first time, an exact expression for the gg → h amplitude in terms of the five-dimensional fermion propagator is derived, which includes the full dependence on the Higgs-boson mass. Various results in the literature are reconciled and shown to correspond to different incarnations of the RS model, in which the Higgs field is either localized on the IR brane or is described in terms of a narrow bulk state. The results in the two scenarios differ in a qualitative way: the gg → h amplitude is suppressed in models where the scalar sector is localized on the IR brane, while it tends to be enhanced in bulk Higgs models. In both cases, effects of higher-dimensional operators contributing to the gg → h amplitude at tree level are shown to be numerically suppressed under reasonable assumptions. There is no smooth cross-over between the two scenarios, since the effective field-theory description breaks down in the transition region. A detailed phenomenological analysis of Higgs production in various RS scenarios is presented, and for each scenario the regions of parameter space already excluded by LHC data are derived.

Impact of warped extra dimensions on the dipole coefficients in b → sγ transitions

“…It is well known that quantum fields can be strictly localized on orbifold fixed points, and in such a scenario the quantity ∆ h can indeed be infinite or arbitrarily large. Similar to the case of Higgs production via gluon fusion [29,[35][36][37][38][39][40][41][42][43][44][45], we will find that our results for the Higgs contributions to the b → sγ and b → sg dipole coefficients are sensitive to details of the localization mechanism. For these contributions we sometimes extend our results to the case of a so-called narrow bulk-Higgs scenario, where the Higgs field lives in the bulk with an inverse width such that M KK ∆ h Λ TeV [29].…”

“…It is instructive to discuss the calculation of the function T d RL (k 2 E ) in more detail, since it exhibits a sensitivity on the regulator η, which is similar to that observed in the calculation of the loop-induced Higgs coupling to two gluons [29,[35][36][37][38][39][40][41][42][43][44][45]. Applying the δ-function regulator (3.12) and inserting the solutions for the external quark profiles (3.17) into (3.14), we obtain…”

“…Nevertheless, one usually considers RS models with a built-in protection for the T parameter by implementing a custodial symmetry via the gauge group SU(3) c × SU(2) L × SU(2) R × U(1) X × P LR [23][24][25]. Then the bound from electroweak precision observables reduces to M g (1) > 4.8 TeV at 95% CL [29]. But on the other hand, the sensitivity of Higgs physics on virtual effects from heavy KK excitations is strongly increased in the model with custodial symmetry, due to the enlarged fermion multiplicity for each KK level.…”

“…The functionsS(t),C(t) are given by (3.16) with X q replaced byX q = (Y † q Y q ) 1/2 . The derivation of the 5D quark propagator in the region near the IR brane has been discussed in detail in [29]. Appendix B contains all solutions that are relevant for the present work.…”

Novel Randall-Sundrum model withS3flavor symmetry

“…For recent studies on Higgs production and decay in multi-Higgs models (some of which are embedded into 5D warped models), see for instance Ref. [98,[117][118][119][120][121][122][123].…”