arXiv subjects

Eri Asakawa

Publications and source records attributed to Eri Asakawa.

26 records · Page 2Linked to original sources

arXiv2000

Probing the MSSM Higgs Boson Sector with Explicit CP Violation through Third Generation Fermion Pair Production at Muon Colliders

We perform a systematic study of the production of a third-generation fermion-pair, $μ^+μ^-\to f\bar{f}$ for $f=τ^-,b$, and t in the minimal supersymmetric standard model (MSSM) with explicit CP violation, which is induced radiatively by soft trilinear interactions related to squarks of the third generation. We classify all the observables for probing the CP property of the Higgs bosons constructed by the initial muon beam polarization along with the unpolarized final fermions and with the final-fermion polarization configuration of equal helicity, respectively. The observables allow for complete determination of CP property of the neutral Higgs bosons. The interference between the Higgs boson and gauge boson contributions also could provide a powerful method for the determination of the CP property of two heavy Higgs bosons in the top-quark pair production near the energy region of the Higgs-boson resonances. For the lightest Higgs-boson mass there is no sizable interference between scalar and vector contributions for the determination of the CP property of the lightest Higgs boson. We give a detailed numerical analysis to show how the radiatively-induced CP violation in the Higgs sector of the MSSM can be measured.

hep-ph↗

arXiv2000

Contributions of vector-like quarks to radiative B meson decay

We study the decay B\to X_sγin a minimal extension of the standard model with extra up- and down-type quarks whose left- and right-handed components are both SU(2) singlets. Constraints on the extended Cabibbo-Kobayashi-Maskawa matrix are obtained from the experimental results for the branching ratio. Even if the extra quarks are too heavy to be detected in near-future colliders, the branching ratio could have a value which is non-trivially different from the prediction of the standard model.

hep-ph↗

arXiv2000

Measuring the Higgs CP Property through Top Quark Pair Production at Photon Linear Colliders

We present a model-independent study of the effects of a neutral Higgs boson without definite CP-parity in the process $γγ\to t\bar{t}$ around the mass pole of the Higgs boson. Near the resonance pole, the interference between the Higgs-exchange and the continuum amplitudes can be sizable if the photon beams are polarized and helicities of the top and anti-top quarks are measured. Study of these interference effects enables one to determine the CP property of the Higgs boson completely. An example of the complete determination is demonstrated in the context of the minimal supersymmetric standard model.

hep-ph↗

arXiv2000

Production of CP-even and CP-odd Higgs bosons at Muon colliders

In the $s$-channel Higgs-boson-exchange processes, the interference between the amplitudes for CP-even and CP-odd Higgs bosons is sizable, if the helicities of initial and final particles are properly fixed and if the mass difference between these bosons is not much larger than their decay widths. We discuss this interference effect in the process $μ^+ μ^-$ $\to t\bar{t}$. Examining the effects gives us information on CP-parity for Higgs bosons and on the sign of a product of the coupling constants for $Hμ^-μ^+$, $Ht\bar{t}$, $Aμ^-μ^+$ and $At\bar{t}$ vertices. The feasibility of observing the interference effect in future muon colliders is evaluated in the framework of the minimal supersymmetric extension of the standard model as an example.

hep-ph↗

arXiv2000

Production of Scalar Higgs and Pseudoscalar Higgs in Multi-Higgs Doublet Models at $γγ$ Colliders

We present the effects of heavy CP-even (H) and CP-odd (A) Higgs bosons on the production cross section of the process $γγ$ $\to t\bar{t}$ at the energy around the mass poles of the Higgs bosons. It is found that the interference between H and A with the small mass gap, as well as the ones between Higgs bosons and the continuum, contributes to the cross section, if the photon beams are polarized and if we observe the helicity of the top quarks. It is demonstrated in the framework of the minimal supersymmetric extension of the standard model that the H and A contributions can be sizable at future $γγ$ colliders for small value of $\tanβ$. The methods to measure the CP-parity of the Higgs boson are also presented. The statistical significances of detecting the Higgs signals and measuring the Higgs CP-parity are evaluated.

hep-ph↗

arXiv1999

Heavy Higgs Productions at $γγ$ Colliders

Multi-Higgs doublet models include more than one neutral Higgs bosons, some of which have different properties under a CP transformation. We examine their productions at $γγ$ colliders. It is found that helicity observations of final top-pairs can be powerful tools to distinguish their CP properties, especially when masses of the Higgs bosons are almost degenerate.

hep-ph↗

arXiv1999

CP-odd WWZ couplings induced by vector-like quarks

A minimal extension of the standard model includes extra quarks with charges 2/3 and/or -1/3, whose left-handed and right-handed components are both SU(2) singlets. This model predicts new interactions of flavor-changing neutral current at the tree level, which also violate CP invariance. We study CP-odd anomalous couplings for the gauge bosons W, W, and Z induced by the new interactions at the one-loop level. These couplings become nonnegligible only if both an up-type and a down-type extra quarks are incorporated. Their form factors are estimated to be maximally of order $10^{-5}$. Such magnitudes are larger than those predicted in the standard model, though smaller than those in certain other models.

hep-ph↗

arXiv1998

Current constraints on squark production scenarios for the excess of high $Q^2$ events at HERA

We examine the stop production scenario for the anomalous excess of high $Q^2$ events observed at HERA, by taking into account the constraints coming from the leptoquark search at Tevatron and the atomic parity violation experiments. This scenario is shown to survive persistently even under the severe constraints from the other experiments. In the analysis, the branching ratios $B_{\stp_j}$ of the decay modes $\stp_j\to ed$ $(j=1,2)$ are found to be useful parameters, representing a number of unknown parameters in the SUSY models. By expressing the stop contribution to the cross section of deep inelastic $ep$ scattering $σ(ep\to eX)$ in terms of $B_{\stp_1}$ and $B_{\stp_2}$, the allowed region is successfully identified in the parameter space of $B_{\stp_1}$ and $B_{\stp_2}$.

hep-ph↗