Higgs mediated flavor changing neutral currents in warped extra dimensions

Abstract

In the context of a warped extra-dimension with Standard Model fields in the bulk, we obtain the general flavor structure of the Higgs couplings to fermions. These couplings will be generically misaligned with respect to the fermion mass matrix, producing large and potentially dangerous flavor changing neutral currents (FCNC's). As recently pointed out in [arXiv:0906.1542], a similar effect is expected from the point of view of a composite Higgs sector, which corresponds to a 4D theory dual to the 5D setup by the AdS-CFT correspondence. We also point out that the effect is independent of the geographical nature of the Higgs (bulk or brane localized), and specifically that it does not go away as the Higgs is pushed towards the IR boundary. The FCNC's mediated by a light enough Higgs (specially their contribution to ǫK ) could become of comparable size as the ones coming from the exchange of Kaluza-Klein (KK) gluons. Moreover, both sources of flavor violation are complementary since they have inverse dependence on the 5D Yukawa couplings, such that we cannot decouple the flavor violation effects by increasing or decreasing these couplings. We also find that for KK scales of a few TeV, the Higgs couplings to third generation fermions could experience suppressions of up to 40% while the rest of diagonal couplings would suffer much milder corrections. Potential LHC signatures like the Higgs flavor violating decays h → µτ or h → tc, or the exotic top decay channel t → ch, are finally addressed.

Enhancing thj production from top-Higgs FCNC couplings

“…mechanism [15][16][17][18]. But they can be greatly enhanced by the extended flavor structures in many new physics models, for example the minimal supersymmetric model (MSSM) with/without R-parity [19][20][21][22][23][24][25][26][27][28][29][30][31][32], two-Higgsdoublet model (2HDM) type-III [33][34][35][36][37][38][39][40][41][42][43][44][45], and the other miscellaneous models [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60]. So the study of top-Higgs FCNC interactions is a common interest of the theory and experiment communities [61][62][6...…”

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

“…In a recent paper [23], it was shown that the discrepancy between the two sets of results can be traced back to a subtlety in the calculation of the loop-induced Higgs couplings to gluons and photons. In order to compute the relevant overlap integrals of fermion wave functions with the brane-localized Higgs field, it is necessary to regularize the Higgs profile in an intermediate step and give it an infinitesimal width η [24]. When the calculation of the gluon fusion amplitude is performed in a naive way, the limits of sending the regulator to zero (η → 0) and including an infinite number of KK modes (N → ∞) in the sum over virtual states do not commute.…”

FCNC effects in a minimal theory of fermion masses

“…We then introduce FN messengers U c 4,3,2,1,0 , D c 4,3,2,1,0 , Q 2,1,0 plus conjugates which we labeled by their U(1) charge. In addition we have to add a certain number of JHEP08 (2011)028 these messenger fields with the same U(1) quantum numbers in order to reproduce SM masses [1][2][3][4], so that the total number of messengers with u c (d c ) SM quantum numbers is at least 12 (17). It turns out that the minimal number of additional messenger fields are two copies of D c 2,1,0 and one copy of U c 1,0 , D c 3 and Q 1,0 .…”