arXiv subjects

Chun-Khiang Chua

Publications and source records attributed to Chun-Khiang Chua.

81 records · Page 5Linked to original sources

arXiv2001

Impact of a Light Strange-Beauty Squark on B_s Mixing and Direct Search

If one has Abelian flavor symmetry, $s_R$-$b_R$ mixing could be near maximal. This can drive a "strange-beauty" squark ($\widetilde{sb}_{1}$) to be rather light, but still evade the $b\to sγ$ constraint. Low energy constraints imply that all other superpartners are at TeV scale, except for a possibly light neutralino, $\widetilde χ_1^0$. Whether light or heavy, the $\widetilde{sb}_{1}$ can impact on the $B_s$ system: $Δm_{B_s}$ and indirect CP phase, even for $B_s \to ϕγ$. Direct search is similar to usual $\tilde b \to b\widetilde χ_1^0$, but existing bounds are weakened by $\widetilde{sb}_{1} \to s\widetilde χ_1^0$ possibility. All these effects could be studied soon at the Tevatron.

hep-ph↗

arXiv2001

Prediction of Three-body $B^0\to ρ^-p\bar{n}, π^-p\bar{n}$ Decay Rates

We predict the rates of the charmless three-body $B^0\to ρ^-p\bar{n}$ and $π^-p\bar{n}$ modes due to weak vector current contributions to be $\sim 4\times 10^{-6}$ and $2\times 10^{-6}$, respectively. The basis is a factorization approach of current produced nucleon pairs, together with an isospin transformation that relates nucleon weak vector form factors to electromagnetic form factors. Adding the axial vector current contribution, we find $B^0\to ρ^-p\bar{n}$ and $B^+\to ρ^0p\bar{n}$ to be at $10^{-5}$ order. The three-body modes appear to dominate over the two-body modes such as $B\to p\bar{p}$, $p\bar Λ$.

hep-ph↗

arXiv2001

Understanding $B\to D^{*-}N\bar{N}$ and Its Implications

The CLEO Collaboration recently reported the observation of the $B^0\to D^{*-}p\bar{n}$ mode at a rate only a factor of 4--5 lower than $B^0\to D^{*-}ρ^+$ and $D^{*-}π^+$. We try to understand this with a factorization approach of current produced nucleon pairs. The baryon weak vector current form factors are related by isospin rotation to nucleon electromagnetic form factors. By using $G^{p,n}_M$ measured from $e^+e^-\to \bar{N}N$ and $p\bar{p}\to e^+e^-$ processes, assuming factorization of the $B^0\to D^{*-}$ transition and the $p\bar n$ pair production, we are able to account for up to 60% of the observed rate. The remainder is argued to arise from the axial current. The model is then applied to B decays to other mesons plus $p\bar{n}$ modes and $D^{*-}$ plus strange baryon pairs.

hep-ph↗

arXiv2001

Supersymmetric Model Contributions to $B^0_d$--$\bar B^0_d$ Mixing and $B\toππ,ργ$ Decays

Recent results from Belle and BaBar Collaborations hint at a small $\sin2ϕ_1$, while the measured $B\toππ$ rate also seems to be on the low side. Supersymmetric (SUSY) models with down squark mixings can account for the deficits in both cases. By studying the origin of SUSY contributions that could impact on $B^0_d$--$\bar B^0_d$ mixing and $B\toππ$ decay, we find that the former would most likely arise from left-left or right-right squark mixings, while the latter would come from left-right squark mixings. These two processes in general are not much correlated in the Minimum Supersymmetric Standard Model. If the smallness of $B\toππ$ is due to SUSY models, one would likely have large $B\toργ$ from chiral enhancement, and the rate could be within present experimental reach. Even if $B\toργ$ is not greatly enhanced, it could have large mixing dependent CP violation.

hep-ph↗

arXiv2001

Phenomenological Consequences of Right-handed Down Squark Mixings

The mixings of $d_R$ quarks, hidden from view in Standard Model (SM), are naturally the largest if one has an Abelian flavor symmetry. With supersymmetry (SUSY) their effects can surface via $\tilde d_R$ squark loops. Squark and gluino masses are at TeV scale, but they can still induce effects comparable to SM in $B_d$ (or $B_s$) mixings, while $D^0$ mixing could be close to recent hints from data. In general, CP phases would be different from SM, as may be indicated by recent B Factory data. Presence of non-standard soft SUSY breakings with large $\tanβ$ could enhance $b\to dγ$ (or $sγ$) transitions.

hep-ph↗

arXiv2000

Equivalent Relations between Quantum Dynamics as Derived from a Gauge Transformation

Equivalent relations between quantum mechanical systems in the Robertson-Walker (RW) background metric and quantum dynamics with an induced quadratic background potential are derived in this work. Two elementary applications, which include an algebraic derivation of the evolution operator for a simple harmonic oscillator without using any special function or the path integral technique, and a moving soliton solution of a free particle in an oscillating universe, are presented to illustrate the use of these equivalent relations.

hep-th↗

arXiv2000

Neutrino mass induced radiatively by supersymmetric leptoquarks

We show how nonzero Majorana neutrino masses can be radiatively generated by extending the MSSM with leptoquark chiral multiplets without violating R-parity. It is found that, with these particles, the R-parity conservation does not imply lepton number conservation. Neutrino masses generated at a one-loop level are closely related to the down quark mass matrix. The ratio of neutrino mass-squared splittings $Δm^2_{ν_2-ν_1}/Δm^2_{ν_3-ν_2}$ obtained is naturally close to $Δm^2_{s-d}/Δm^2_{b-s}\sim 10^{-3}$ which is in the right region required to explain both the atmospheric neutrino data and the MSW solutions for the solar neutrino data.

hep-ph↗

arXiv1999

CP Violating B ---> s Gamma Decay in Supersymmetric Models

Supersymmetric models with nonuniversal down type squark masses can enrich the chiral structure and CP violating phenomena in $b\to sγ$ decays. Direct CP violation in $b\to s γ$, mixing induced CP violation in radiative $B_{d,s}$ decays (such as $B_s\to ϕγ$ and $B_d \to K^*_{1,2}γ$), and $Λ$ polarization in $Λ_b \to Λγ$ can be substantially different from the Standard Model. Future experiements at $e^+ e^-$ and hadronic B factories will give important information on the underlying theory for radiative $b$ decays.

hep-ph↗

arXiv1998

The Neutrino Magnetic Moment Induced by Leptoquarks

Allowing leptoquarks to interact with both right-handed and left-handed neutrinos (i.e., ``non-chiral'' leptoquarks), we show that a non-zero neutrino magnetic moment can arise naturally. Although the mass of the non-chiral vector leptoquark that couples to the first generation fermions is constrained severely by universality of the $π^+$ leptonic decays and is found to be greater than 50 TeV, the masses of the second and third generation non-chiral vector leptoquarks may evade such constraint and may in general be in the range of $1\sim 100$ TeV. With reasonable input mass and coupling values, we find that the neutrino magnetic moment due to the second generation leptoquarks is of the order of $10^{-12}\sim 10^{-16} μ_{\rm B}$ while that caused by the third generation leptoquarks, being enhanced significantly by the large top quark mass, is in the range of $10^{-10}\sim 10^{-14} μ_{\rm B}$.

hep-ph↗