arXiv subjects

Ryoutaro Watanabe

Publications and source records attributed to Ryoutaro Watanabe.

40 records · Page 3Linked to original sources

arXiv2012

Higgs at ILC in Universal Extra Dimensions in Light of Recent LHC Data

We present bounds on all the known universal extra dimension models from the latest Higgs search data at the Large Hadron Collider, taking into account the Kaluza-Klein (KK) loop effects on the dominant gluon-fusion production and on the diphoton/digluon decay. The lower bound on the KK scale is from 500GeV to 1TeV depending on the model. We find that the Higgs production cross section with subsequent diphoton decay can be enhanced by a factor 1.5 within this experimental bound, with little dependence on the Higgs mass in between 115GeV and 130GeV. We also show that in such a case the Higgs decay branching ratio into a diphoton final state can be suppressed by a factor 80%, which is marginally observable at a high energy/luminosity option at the International Linear Collider. The Higgs production cross section at a photon-photon collider can also be suppressed by a similar factor 90%, being well within the expected experimental reach.

hep-ph↗

arXiv2012

Heavy Higgs at Tevatron and LHC in Universal Extra Dimension Models

Universal Extra Dimension (UED) models tend to favor a distinctively heavier Higgs mass than in the Standard Model (SM) and its supersymmetric extensions when the Kaluza-Klein (KK) scale is not much higher than the electroweak one, which we call the weak scale UED, in order to cancel the KK top contributions to the T-parameter. Such a heavy Higgs, whose production through the gluon fusion process is enhanced by the KK top loops, is fairly model independent prediction of the weak scale UED models regardless of the brane-localized mass structure at the ultraviolet cutoff scale. We study its cleanest possible signature, the Higgs decay into a Z boson pair and subsequently into four electrons and/or muons, in which all the four-momenta of the final states can be measured and both the Z boson masses can be checked. We show that the weak scale UED model may account for the 2sigma excess of this event at ATLAS at the ZZ pair invariant mass around 250GeV, at which scale SM background is sufficiently small and the SM Higgs predicts too few events. We have also studied the Higgs mass 500GeV (and also 700GeV with \sqrt{s}=14TeV) and have found that we can observe significant resonance with the integrated luminosity 10fb^{-1} for six dimensional UED models.

hep-ph↗

arXiv2011

A bound on Universal Extra Dimension Models from up to 2fb^{-1} of LHC Data at 7TeV

The recent up to 2fb^{-1} of data from the ATLAS and CMS experiments at the CERN Large Hadron Collider at 7TeV put an upper bound on the production cross section of a Higgs-like particle. We translate the results of the H -> WW -> l nu l nu and H -> gamma gamma as well as the combined analysis by the ATLAS and CMS into an allowed region for the Kaluza-Klein (KK) mass M_{KK} and the Higgs mass $M_H$ for all the known Universal Extra Dimension (UED) models in five and six dimensions. Our bound is insensitive to the detailed KK mass splitting and mixing and hence complementary to all other known signatures.

hep-ph↗

arXiv2010

Tau longitudinal polarization in B -> D tau nu and its role in the search for charged Higgs boson

We study the longitudinal polarization of the tau lepton in B -> D tau nu decay. After discussing possible sensitivities of tau decay modes to the tau polarization, we examine the effect of charged Higgs boson on the tau polarization in B -> D tau nu. We find a relation between the decay rate and the tau polarization, and clarify the role of the tau polarization measurement in the search for the charged Higgs boson.

hep-ph↗