Precision electroweak constraints on universal extra dimensions revisited

Abstract

We reconsider the constraints on Universal Extra Dimensions (UED) models arising from precision electroweak data. We take into account the subleading contributions from new physics (expressed in terms of the X, Y . . . variables), as well as two loop corrections to the Standard Model ρ parameter. For the case of one extra dimension, we obtain a lower bound on the inverse compactification scale M = R −1 of 600 GeV (at 90% confidence level), with a Higgs mass of 115 GeV. However, in contradiction to recent claims, we find that this constraint is significantly relaxed with increasing Higgs mass, allowing for compactification scales as low as 300 GeV. LEP II data does not affect significantly these results. * On a leave of absence from:

Search for Higgs bosons of the universal extra dimensions at the large Hadron collider

“…This finding was later shown to be consistent with observations in the B-physics sector [17] and with the experimental results on anomalous magnetic moments [18,19]. However, in later years, with more data and newer analyses it has been observed that the lower bound on R −1 can surpass the earlier value and can be as high as 700 GeV [27,39,59] at 99% confidence level. Also, similar to R-parity in SUSY scenarios, KK-parity ensures that the lightest n = 1 KK-paricle (the LKP, with odd KK-parity) is an absolutely stable (like the lightest SUSY particle, the LSP) weakly interacting massive particle (WIMP) and is a good dark matter candidate that could provide the right amount of cosmological relic-density [31] 5 .…”

“…The presence of KK-towers for charged and neutral CP-odd Higgs bosons provides a concrete example of this. The phenomenology of KK-excitations has been studied in great detail in recent times which covers its implications at colliders [3,4,5,6,7,8,9,10,11,12,13,14,15,16], in electroweak/flavour sector via various low-energy observables [17,18,19,20,21,22,23,24,25,26,27,28] and for dark matter/cosmology [5,13,29,30,31,32,33,34,35,36,37,38,39,40] In MUED there are only two extra free parameters when compared to the SM. These are the radius of compactification R (or, alternately R −1 , the scale of compactification) and the cutoff scale Λ of the theory.…”

Analysis of the radiativeΛb→Λγtransition in the standard model and scenarios with one or two universal extra dimensions

“…1, we see that there are distinctive differences between the SM predictions and those of the UED models, especially the UED6 for N KK ¼ 15, at small values of the [55] ð0:63 À 0:73Þ Â 10 À5 Three-point QCD sum rule [56] ð3:1 AE 0:6Þ Â 10 À5 QCD sum rule [57] ð3:7 AE 0:5Þ Â 10 À5 COQM [58] 0:23 Â 10 À5 Special current [59] ð1:99 þ0:34 À0:31 Þ Â 10 À5 Ioffe current [59] ð0:61 þ0:14 À0:13 Þ Â 10 À6 Pole model [60] ð1:0 À 4:5Þ Â 10 À5 PDG [54] <1:3 Â 10 À3 (CL ¼ 90%Þ compactification factor 1=R. These differences exist in the lower limits obtained by different FCNC transitions in the UED5 and UED6, cosmological constraints, electroweak precision tests [25,29,31,32], and the latest results of the Higgs search at the LHC and of the electroweak precision data for the S and T parameters [34]; however, they become small when 1=R approaches 1 TeV. Our analysis show that the UED scenarios give close results to the SM for 1=R !…”

Mixed dark matter in Universal Extra Dimension models with TeV scaleWRandZ′

“…It has been shown that in the minimal universal extra dimension (MUED) the KK contributions to the T parameter almost cancel for heavier standard model Higgs [9,15]. However, it was found that in the MUED for Higgs mass heavier than 300 GeV the lightest Kaluza-Klein particle is the charged KK Higgs [16].…”