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Register a new userEffects of non-minimal Universal Extra Dimension on $Brightarrow X_sgamma$
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Anindya Datta
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We estimate contributions from Kaluza-Klein excitations of third generation quarks and gauge bosons to the branching ratio of $Brightarrow X_sgamma$ decay process in 5-Dimensional Universal Extra Dimensional scenario with non-vanishing boundary localised terms. This model is conventionally known as non-minimal Universal Extra Dimensional model. We have derived the lower limit on the size of the extra dimension by comparing our theoretical estimation of the branching ratio which includes next-to-next-to leading order QCD corrections with its experimentally measured value. Coefficients of the boundary localised terms have also been constrained. 95 % C.L. lower limit on inverse of radius of compactification ($R^{-1}$) can be as large as 670 GeV for some choice of the value of coefficients of boundary localised terms.
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In this paper we consider an $S^{1}/mathbb{Z}_2$ compactified flat extra dimensional scenario where all the standard model states can access the bulk and have generalised brane localised kinetic terms. The flavour structure of brane kinetic terms for the standard model fermions are dictated by stringent flavour bounds on the first two generations implying an $U(2)_{Q_L} otimes U(2)_{u_R} otimes U(2)_{d_R}$ flavour symmetry. We consider the constraints on such a scenario arising from dark matter relic density and direct detection measurements, precision electroweak data, Higgs physics and LHC dilepton searches. We discuss the possibility of such a scenario providing an explanation of the recently measured anomaly in $R_{K^{(ast)}}$ within the allowed region of the parameter space.
Non-vanishing boundary localised terms significantly modify the mass spectrum and various interactions among the Kaluza-Klein excited states of 5-Dimensional Universal Extra Dimensional scenario. In this scenario we compute the contributions of Kaluza-Klein excitations of gauge bosons and third generation quarks for the decay process $Brightarrow X_sell^+ell^-$ incorporating next-to-leading order QCD corrections. We estimate branching ratio as well as Forward Backward asymmetry associated with this decay process. Considering the constraints from some other $b to s$ observables and electroweak precision data we show that significant amount of parameter space of this scenario has been able to explain the observed experimental data for this decay process. From our analysis we put lower limit on the size of the extra dimension by comparing our theoretical prediction for branching ratio with the corresponding experimental data. Depending on the values of free parameters of the present scenario, lower limit on the inverse of the radius of compactification ($R^{-1}$) can be as high as $geq 760$ GeV. {Even this value could slightly be higher if we project the upcoming measurement by Belle II experiment.} Unfortunately, the Forward Backward asymmetry of this decay process would not provide any significant limit on $R^{-1}$ in the present model.
We estimate contributions from Kaluza-Klein excitations of gauge bosons and physical charge scalar for the explanation of the lepton flavor universality violating excess in the ratios $mathcal{R}(D)$ and $mathcal{R}(D^*)$ in 5 dimensional Universal Extra Dimensional scenario with non-vanishing boundary localized terms. This model is conventionally known as non-minimal Universal Extra Dimensional model. We obtain the allowed parameter space in accordance with constraints coming from $B_c to tau u$ decay, as well as those from the electroweak precision tests.
Universal Extra Dimension (UED) is a well-motivated and well-studied scenario. One of the main motivations is the presence of a dark matter (DM) candidate namely, the lightest level-1 Kaluza-Klein (KK) particle (LKP), in the particle spectrum of UED. The minimal version of UED (mUED) scenario is highly predictive with only two parameters namely, the radius of compactification and cut-off scale, to determine the phenomenology. Therefore, stringent constraint results from the WMAP/PLANCK measurement of DM relic density (RD) of the universe. The production and decays of level-1 quarks and gluons in UED scenarios give rise to multijet final states at the Large Hadron Collider (LHC) experiment. We study the ATLAS search for multijet plus missing transverse energy signatures at the LHC with 13 TeV center of mass energy and 139 inverse femtobarn integrated luminosity. In view of the fact that the DM RD allowed part of mUED parameter-space has already been ruled out by the ATLAS multijet search, we move on to a less restricted version of UED namely, the non-minimal UED (nmUED), with non-vanishing boundary-localized terms (BLTs). The presence of BLTs significantly alters the dark matter as well as the collider phenomenology of nmUED. We obtain stringent bounds on the BLT parameters from the ATLAS multijet plus missing transverse energy search.
We discuss prospects of the $Z$ search at the LHC in non-minimal Universal Extra Dimensions with tree-level brane-local terms in five dimensions. In this scenario, we find two major differences from the usual $Z$ physics: (i) two $Z$ candidates close-by in mass exist; (ii) the effective couplings to the SM fermions could be very large due to drastic overlapping of their profiles along the extra dimension. To evaluate the actual situation precisely, we reconsider the important issues of resonant processes, i.e., treatment of resonant propagators and including interference effects.
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