arXiv subjects

Wei-Shu Hou

Publications and source records attributed to Wei-Shu Hou.

136 records · Page 8Linked to original sources

arXiv1995

Magnetic Field Dependence of Muonium-antimuonium Conversion

We study the magnetic field dependence of muonium--antimuonium conversion induced by neutral (pseudo)scalar bosons. Only the $SS$ operator contributes to the conversion of polarized muonium, but it gets quenched by a magnetic field of strength 0.1 Gauss or stronger. Conversion induced by $SS$ couplings for unpolarized muonium is independent of magnetic field. Magnetic fields of 0.1 Tesla or stronger starts to suppress conversion induced by $PP$ interactions in the lowest Breit-Rabi level, but gets partially compensated by a rise in conversion probability in the other unpolarized level. The effects of $(S\mp P)(S\mp P)$ and $(S\mp P)(S\pm P)$ operators behave in the same way as $(V\mp A)(V\mp A)$ and $(V\mp A)(V\pm A)$ operators, respectively.

hep-ph↗

arXiv1995

$μ^+e^- <---> μ^- e^+$ Transitions via Neutral Scalar Bosons

With $μ\to eγ$ decay forbidden by multiplicative lepton number conservation, we study muonium--antimuonium transitions induced by neutral scalar bosons. Pseudoscalars do not induce conversion for triplet muonium, while for singlet muonium, pseudoscalar and scalar contributions add constructively. This is in contrast to the usual case of doubly charged scalar exchange, where the conversion rate is the same for both singlet and triplet muonium. Complementary to muonium conversion studies, high energy $μ^+e^- \to μ^- e^+$ and $e^-e^- \to μ^- μ^-$ collisions could reveal spectacular resonance peaks for the cases of neutral and doubly charged scalars, respectively.

hep-ph↗

arXiv1994

Perspective on Quark Mass and Mixing Relations

Recent data indicate that $V_{ub}\cong λ^4 \cong (0.22)^4$, while $m_t$ seems to be $174$ GeV. The relations $m_d/m_s\sim m_s/m_b \sim δ\sim λ^2 \simeq \vert V_{cb}\vert$ and $m_u/m_c\sim m_c/m_t \sim δ^2 \sim λ^4 \sim \vert V_{ub}\vert$ suggest that %a plausible clean separation of the %origin of the quark mixing matrix: the down type sector is responsible for $\vert V_{us}\vert$ and $\vert V_{cb}\vert$, while $V_{ub}$ comes from the up type sector. Five to six parameters might suffice to account for the ten quark mass and mixing parameters, resulting in specific power series representations for the mass matrices. In this picture, $δ$ seems to be the more sensible expansion parameter, while $λ\cong \sqrt{m_d/m_s} \sim \sqrtδ$ is tied empirically to $(M_d)_{11} = 0$.

hep-ph↗

arXiv1994

Singlet Charge $2/3$ Quark hiding the Top: Tevatron and LEP Implications

If $c$ and $t$ quarks are strongly mixed with a weak singlet charge $2/3$ quark, $BR(t\to \ellν+ X)$ could be suppressed via the $t\to cH^0$ mode, thereby the top quark could still hide below $M_W$, whereas the heavy quark signal observed at the Tevatron is due to the dominantly singlet quark $Q$. This may occur without affecting the small $m_c$ value. Demanding $m_Q \simeq 175$ GeV and $m_t \ltap M_W$, we find that $BR(t\to \ellν+ X)$ cannot be too suppressed. The heavy quark $Q$ decays via $W,\ H$, and $Z$ bosons. The latter can lead to $b$-tagged $Z + 4$ jet events, while the strong $c$--$Q$ mixing is reflected in sizable $Q\to sW$ fraction. $Z\to t\bar c$ decay occurs at tree level and may be at the $10^{-3}$ order, leading to the signature of $Z\to \ellνb\bar c$, all isolated and with large $p_T$, at $10^{-5}$ order.

hep-ph↗

arXiv1994

Limit on $Br(b\to s g)$ in Two Higgs Doublet Models

Using the recent CLEO measurement of $Br(b\to s γ)$, we find that the branching ratio of $b\to s g$ cannot be larger than $10\%$ in two Higgs doublet models. The small experimental value of $Br(b\to e\barνX)$ can no longer be explained by charged Higgs boson effects.

hep-ph↗

arXiv1994

Possibility of $m_t < M_W + m_b$ for SUSY-type of Two Higgs Doublet Model

Allowing for realistic uncertainties in input parameters, we demonstrate that the present CLEO limit of $5.4\times 10^{-4}$ for inclusive $b\to sγ$ decay does not yet fully exclude the $t\to bH^+$ decay possibility in supersymmetric type of two Higgs doublet models. Combined with direct search for $t\to bH^+$ via $H^+\to τ^+ν$ at the Tevatron, we conclude that $\tanβ\sim 1$ is the ``allowed" window for $m_{H^+} < m_t < M_W$. The possibility becomes excluded, however, {\it if} the CLEO limit is pushed below $4\times 10^{-4}$.

hep-ph↗

arXiv1994

Radiative Majorana Neutrino Masses

We present new radiative mechanisms for generating Majorana neutrino masses, within an extension of the standard model that successfully generates radiative charged lepton masses, order by order, from heavy sequential leptons. Only the new sequential neutral lepton has a right-handed partner, and its Majorana mass provides the seed for Majorana neutrino mass generation. Saturating the cosmological bound of $50$ eV with $m_{ν_τ}$, we find that $m_{ν_μ}$ and $m_{ν_e}$ could be at most $10^{-2}$, and $10^{-3}$ eV, respectively. The electron neutrino mass may vanish in the limit of degenerate charged Higgs bosons. Unfortunately, $ν_e - ν_τ$ mixing is also radiatively induced, and is too small for sake of solving the solar neutrino problem via the Mikheyev--Smirnov--Wolfenstein effect.

hep-ph↗

arXiv1994

Radiative Lepton Masses with Heavy Lepton Seed

We construct a $Z_8$ model for leptons where all Yukawa couplings are of order unity, but known lepton masses are generated radiatively, {\it order by order}. The seed is provided by fourth generation leptons $E$ and $N$, which receive (Dirac) mass in usual way. Two additional Higgs doublets with nontrivial $Z_8$ charge are introduced to give nearest neighbor Yukawa couplings. Hence, nonstandard Higgs bosons are flavor changing in an unusual way. Loop masses are generated when $Z_8$ is {\it softly} broken down to $Z_2$. However, $e$ and $μ$ mass generation require new Higgs bosons to be at weak scale. Neutral scalar mixing underlies $m_μ/m_τ\gg m_e/m_μ$, $m_τ/m_E$. The $Z_2$ symmetry forbids $μ\to eγ$ and $τ\to μγ$. The most stringent bound comes from $τ\to μμ^\pm e^\mp$. The model has interesting implications for $τ\to eγ$, $μ\bar e \to \barμe$ conversion, $μ\to eν_e\barν_μ$, and FCNC decays of $E$ and $N$ (such as $E\to τe^\pmμ^\mp$).

hep-ph↗

arXiv1993

Is the Top Quark Really Heavier than the $W$ Boson?

Scalar induced top decays may drastically suppress $B(t\to \ellν+ jet)$ and still hide the top below $M_W$. The $p\bar p$ collider experiments should enlarge the scope and study the $m_t - B(t\to\ellνj)$ plane. Specific model signatures such as $t\to ch^0\to cb\bar b$ (multiple high $p_T$ $b$-jets) and $t\to bH^+\to bc\bar s$, $bτ^+ν$ (with $B(t\to bτν) \ \raisebox{-.5ex}{\rlap{$\sim$}} \raisebox{.4ex}{$<$}\ 1/3$) should be explored. Without ruling out these possibilities, isolated lepton signals in the future might actually be due to the 4th generation $t^\prime$ or $b^\prime$ quark, while top quark and toponium physics could still turn up at LEP-II.

hep-ph↗

arXiv1993

Experimental and Theoretical Implications of New Sequential Leptons

If new sequential leptons $E^\pm$ and $N^0$ exist, the LEP bound implies $m_E$, $m_N > M_Z/2$. The heaviness of the neutral lepton breaks away from the pattern of the first three generations. The minimal model is to have 4 left-handed lepton doublets and 4 right-handed charged lepton singlets, but only one right-handed neutral lepton singlet. Since in general the 3rd and 4th generation should mix, and since $\vert m_N - m_E\vert$ should not be too large, neither $E$ nor $N$ would be stable, and both tend to decay via the Cabibbo suppressed $E\to ν_τ$ or $N\to τ$ charged currents. This leads to the interesting signature of like-sign $W$ pair production via $E^+N \to \barν_ττ^- W^+W^+$ at the SSC and LHC. The popular seesaw mechanism cannot plausibly accommodate the near masslessness of the light neutrinos and the heaviness of $N^0$ simultaneously. The representation structure poses a difficulty to the traditional approach of $SO(10)$-based grand unified theories. The discovery of such new heavy leptons would thus have rather wide ranging and far reaching implications.

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