Dimension-six top-Higgs interaction and its effect in collider phenomenology

Measurement of the Yukawa interaction between the top quark and the Higgs boson should be useful to clarify the mechanism of fermion mass generation. We discuss the impact of non-standard interactions characterized by dimension-six operators on the effective top Yukawa coupling. The cross section of the process $e^-e^+ \to W^-W^+ \nu \bar \nu \to t \bar t \nu \bar \nu$ is calculated including these operators, and possible deviation from the standard model prediction is evaluated under the constraint from perturbative unitarity and current experimental data. We find that if the new physics scale is in a TeV region, the cross section can be significantly enhanced due to the non-standard interactions. Such a large effect should be detectable at the International Linear Collider.Comment: 22 pages, RevTex4, 20 eps figure

Integral representations of q-analogues of the Hurwitz zeta function

Two integral representations of q-analogues of the Hurwitz zeta function are established. Each integral representation allows us to obtain an analytic continuation including also a full description of poles and special values at non-positive integers of the q-analogue of the Hurwitz zeta function, and to study the classical limit of this q-analogue. All the discussion developed here is entirely different from the previous work in [4]Comment: 14 page

Suboptimal quantum-error-correcting procedure based on semidefinite programming

In this paper, we consider a simplified error-correcting problem: for a fixed encoding process, to find a cascade connected quantum channel such that the worst fidelity between the input and the output becomes maximum. With the use of the one-to-one parametrization of quantum channels, a procedure finding a suboptimal error-correcting channel based on a semidefinite programming is proposed. The effectiveness of our method is verified by an example of the bit-flip channel decoding.Comment: 6 pages, no figure, Some notations differ from those in the PRA versio

Search for doubly charged Higgs bosons using the same-sign diboson mode at the LHC

Doubly charged Higgs bosons are predicted in many new physics models with an extended Higgs sector that contains a Higgs triplet field. Current experimental searches have been focusing mainly on the scenario in which the same-sign dilepton decay modes are the dominant ones. We study the scenario where the vacuum expectation value of the triplet field is sufficiently large so that the associated charged Higgs bosons decay dominantly to a pair of weak gauge bosons instead. A detailed simulation of the signal and the backgrounds is performed for the CERN Large Hadron Collider at the collision energy of 8 TeV and 14 TeV. We find that different cuts should be imposed for the events, depending on whether the doubly charged Higgs boson mass is greater than about 200 GeV. In the higher mass region, the forward jet tagging proves to be useful in enhancing the signal significance. We show the discovery reach of the LHC running at 8 and 14 TeV, with two benchmark triplet vacuum expectation values. With an integrated luminosity of 10 fb${}^{-1}$ at 8 TeV, the doubly charged Higgs boson with a mass of $\sim 180$ GeV can be tested at $5\sigma$ level in such a scenario.Comment: 18 pages, 10 figures; published in Physical Review

A Higgs Quadruplet for Type III Seesaw and Implications for μ→eγ\mu \to e\gamma and μ−e\mu - e Conversion

In Type III seesaw model the heavy neutrinos are contained in leptonic triplet representations. The Yukawa couplings of the triplet fermion and the left-handed neutrinos with the doublet Higgs field produce the Dirac mass terms. Together with the Majorana masses for the leptonic triplets, the light neutrinos obtain non-zero seesaw masses. We point out that it is also possible to have a quadruplet Higgs field to produce the Dirac mass terms to facilitate the seesaw mechanism. The vacuum expectation value of the quadruplet Higgs is constrained to be small by electroweak precision data. Therefore the Yukawa couplings of a quadruplet can be much larger than those for a doublet. We also find that unlike the usual Type III seesaw model where at least two copies of leptonic triplets are needed, with both doublet and quadruplet Higgs representations, just one leptonic triplet is possible to have a phenomenologically acceptable model because light neutrino masses can receive sizable contributions at both tree and one loop levels. Large Yukawa couplings of the quadruplet can induce observable effects for lepton flavor violating processes $\mu \to e \gamma$ and $\mu - e$ conversion. Implications of the recent $\mu \to e\gamma$ limit from MEG and also limit on $\mu - e$ conversion on Au are also given. Some interesting collider signatures for the doubly charged Higgs boson in the quadruplet are discussed.Comment: Latex 11 pages, 1 figure. A few references adde

On Witten multiple zeta-functions associated with semisimple Lie algebras IV

In our previous work, we established the theory of multi-variable Witten zeta-functions, which are called the zeta-functions of root systems. We have already considered the cases of types $A_2$, $A_3$, $B_2$, $B_3$ and $C_3$. In this paper, we consider the case of $G_2$-type. We define certain analogues of Bernoulli polynomials of $G_2$-type and study the generating functions of them to determine the coefficients of Witten's volume formulas of $G_2$-type. Next we consider the meromorphic continuation of the zeta-function of $G_2$-type and determine its possible singularities. Finally, by using our previous method, we give explicit functional relations for them which include Witten's volume formulas.Comment: 22 pag

Phenomenology in the Zee Model with the A_4 Symmetry

The Zee model generates neutrino masses at the one-loop level by adding charged SU(2)_L-singlet and extra SU(2)_L-doublet scalars to the standard model of particle physics. As the origin of the nontrivial structure of the lepton flavor mixing, we introduce the softly broken A_4 symmetry to the Zee model. This model is compatible with the tribimaximal mixing which agrees well with neutrino oscillation measurements. Then, a sum rule m_1 e^{i alpha_12} + 2 m_2 + 3 m_3 e^{i alpha_32} = 0 is obtained and it results in Delta m^2_31 < 0 and m_3 > 1.8*10^{-2}eV. The effective mass |(M_nu)_{ee}| for the neutrinoless double beta decay is predicted as | (M_\nu)_{ee} | > 1.7*10^{-2}eV. The characteristic particles in this model are SU(2)_L-singlet charged Higgs bosons s^+_alpha (alpha=xi,eta,zeta) which are made from a 3-representation of A_4. Contributions of s^+_alpha to the lepton flavor violating decays of charged leptons are almost forbidden by an approximately remaining Z_3 symmetry; only BR(tau to ebar mu mu) can be sizable by the flavor changing neutral current interaction with SU(2)_L-doublet scalars. Therefore, s^+_alpha can be easily light enough to be discovered at the LHC with satisfying current constraints. The flavor structures of BR(s^-_alpha to ell nu) are also discussed.Comment: 26 pages, 4 figures, version accepted by PR