Higgs production at the LHC in warped extra-dimensional models

Abstract

The extra-dimensional model in which the bulk geometry is a slice of anti-de Sitter space is a particularly attractive extension of the Standard Model as it allows to address the gauge hierarchy problem, as well as the mass hierarchy prevailing among fermions. However, to allow for the masses of the Kaluza-Klein excitations of the known particles to be near the Terascale without conflicting with the high-precision electroweak data, one needs to promote the gauge symmetry to a left-right structure SU(2)_L x SU(2)_R x U(1) which incorporates a new quark b', the SU(2)_R doublet partner of the heavy top quark. We show that this new quark will contribute to the main production process of Higgs bosons at the LHC: the gluon-gluon fusion mechanism which proceeds through heavy quark triangular loops. In most of the parameter space in which the measured values of the heavy t,b quark masses are reproduced, the gg -> Higgs production cross section is significantly altered, even if the b' quark is too heavy to be directly accessible, m_b' > ~1TeV. Finally, we briefly discuss the new Higgs production and decay channels involving the b' quark.

Figures (3)

• Figure 1: Feynman diagram for the $gg\!\to\!H$ production process.
• Figure 2: Values of the ratio ${\cal R}=\sigma_H^{\rm RS}/\sigma_H^{\rm SM}$ in the plane $[c_t,c_Q]$ for a fixed value $c_b\!=\!0.6$. The filled regions correspond from white to darkest grey to, respectively, the intervals ${\cal R} \in [1,1.2]$, $[1.2,2]$, $[2,4]$ and ${\cal R}>4$. The green dotted--lines are the contour levels for $m_{b}\!=1\!$--4.5 GeV, the red solid--lines for $m_{t}\!=\!150$--200 GeV (both from right to left), while the blue dashed--lines are associated to $m_{b_2}= 200$--1000 GeV (from down to up). We have set $kR= 10.11$ and $k$ such that $M_{\rm KK}= 3$ TeV and restricted to values $\vert c \vert ={\cal O}(1)$.
• Figure 3: Main branching ratios for the Higgs boson decay channels [$H \to W^+W^-$; $ZZ$; $t_1 \bar{t}_1$; $b_2 \bar{b}_2$] as a function of the Higgs mass [in GeV], for the parameter set: $c_b\!=\!0.6$, $c_t\!=\!-0.55$, $c_Q\!=\!0.24$ which corresponds to $m_{t_1}\!=\!180$ GeV and $m_{b_2}\!=\!215$ GeV.