Diphoton Higgs signal strength in universal extra dimensions.

The signal strength of the gg → H → γγ reaction in pp collisions at the Large Hadron Collider is studied within the context of the standard model with universal extra dimensions (UED). The impact of an arbitrary number n of UED on both the gg → H and H → γγ subprocesses is studied. The one-loop contribution of Kaluza–Klein excitations on these subprocesses are proportional to discrete and continuous sums, , which can diverge. By implementing the dimensional regularization scheme, it is shown that discrete regularized sums can naturally be expressed as multidimensional Epstein functions, and that divergences, if exist, emerge through the poles of these functions. It is found that continuous sums converge, but the discrete ones diverge, with the exception of the n = 1 case, in which the one-dimensional Epstein function converges. It is argued that divergences that arise from discrete sums for n ⩾ 2 are genuine ultraviolet divergences, since they correspond to short-distance effects in the compact manifold. Then, the amplitudes are renormalized in a modern sense by incorporating interactions of canonical dimension higher than four that allow us to generate the required counterterms, which are determined using a -like renormalization scheme. We find that the gg → H subprocess is quite sensitive to both the size and the dimension of the compact manifold, but the Standard Model prediction for H → γγ subprocess is practically unchanged. It is found that the experimental limit on leads to lower bounds for the compactification scale given by R−1 ⩾ 1.26, 1.55, 2.45, 3.57, 5.10, 7.25 TeVs for n = 1, 2, 4, 6, 8, 10, respectively. [ABSTRACT FROM AUTHOR]