Collider implications of a nonuniversal Higgs boson

Abstract

We consider in detail the possibility that the Higgs is wholly or partially excluded from propagating into one otherwise universal extra dimension. This exclusion of the Higgs from propagating into an otherwise universal extra dimension violates treelevel KaluzaKlein number conservation in the Yukawa interactions. As a consequence, there is intermode mixing between fermions. For example, zero mode fermions mix with their associated KaluzaKlein excitations. This is in contrast to the original universal extra dimensions scenario, in which conservation of KaluzaKlein number prohibits such inter mode mixing. Intermode mixing is especially significant for the top quark, since its mass (171.4 ± 2.1 GeV) is approximately onehalf the current Tevatron mass bound (~350400 GeV) for KaluzaKlein excitations of quarks propagating into universal extra dimensions. We compute the effects that mixing among the zeromodes and lowestlying KaluzaKlein excitations has on the lightest thirdgeneration charge 2/3 quark mass eigenvalue in the nonuniversal Higgs model with one otherwise universal extra dimension. Another consequence of the intermode mixing is that the KaluzaKlein excitations of the fermions can decay to a zeromode Higgs and a corresponding zeromode fermion. As a result, the pair production of KaluzaKlein excitations of the top quark would lead to two zeromode Higgs bosons plus a zeromode top quark/antiquark pair. We compute the cross section that the nonuniversal Higgs model contributes to Higgs production at the Large Hadron Collider. The effect is quite large: For example, the KaluzaKlein contribution to Higgs production is comparable to or larger than the Standard Model contribution, depending on the Higgs mass, for compactification scales up to about 600 GeV.

Top pair invariant mass distribution: a window on new physics

“…In addition, in many such models gauge interactions exist whose coupling with the third generation quarks and in particular to the top quark are enhanced. These include Kaluza-Klein (KK) excitations of the graviton [19,20,21] as well as the weak [22] and the strong gauge bosons [23,24,25,26,19,27,28,29,30] which couple to top quarks. Such particles could show up as resonances in the pp → X → t t production channel and not in other channels, like di-jets or di-leptons, due to their small couplings to light particles.…”

A mechanism for Kaluza–Klein number violation in UED and implications for LHC

“…We allow for both the simple case in which the Higgs either does not propagate into any extra dimensions or propagates into a different extra dimension, and for generality we also allow for the possibility that the Higgs may propagate partway into the OUED. The 5D quark multiplets consist of fourcomponent vectorlike quark fields, which can be decomposed into 4D twocomponent Weyl spinors via Fourier expansion about the OUED coordinate y : The truncated mass matrix for the weak eigenstate zeromode top quark and its lowestlying KK excitations is [6] ( ) invariance, and the other offdiagonal elements arise from treelevel violation of KK number conservation. There is a corresponding mass matrix for the Hermitian conjugate terms:…”

“…Thus, one unique feature of the NUH, as compared to quark mixing in the SM, is that the biunitary transformation that diagonalizes the 5D mass matrix does not also diagonalize the corresponding effective 4D Yukawa coupling matrix. This leads to off ( ) 4 ( ) 5 ( ) 6 diagonal Yukawa interactions between the top quark, its lowestlying KK excitations, and the Higgs boson.…”

“…plots, we use the values of 33 y that correspond to the central allowed region -found by demanding that the lightest mass eigenvalue correspond to the observed top quark mass -ofFig. 's 12 of Ref [6]…”

Searching fortt¯resonances at the CERN Large Hadron Collider

“…The masses of these particles are typically in the TeV range. For example, topcolor [2,3] and Little Higgs [4][5][6][7][8] models predict weakly coupled new vector bosons, models with extra dimensions [9][10][11] can have Kaluza-Klein (KK) excitations of the graviton [12,13], the weak [11,14,15], and the strong gauge bosons [16][17][18][19][20][21][22][23] which couple to top quarks, while massive axial vector bosons appear in torsion gravity models [24]. Resonances in the t " t channel also occur in technicolor [25,26], chiral color [27], and models with a strong SUð3Þ Â SUð3Þ gauge symmetry [28,29].…”