arXiv subjects
Publications and source records attributed to C. Q. Geng.
We demonstrate that the extension of the Zee-Babu model can generate not only the small neutrino masses but also the baryon number asymmetry in the universe. In particular, we show that the scale of the singlet scalar responsible for the leptogenesis can be of order 1 TeV, that can be tested at the LHC and ILC. We also considered the possible minimal extension of this model to generate the dark matter.
We discuss the generation of large-scale magnetic fields due to the breaking of the conformal invariance in the electromagnetic field through the $CPT$-even dimension-six Chern-Simons-like effective interaction with a fermion current in inflationary cosmology. It is shown that the magnetic fields on 1Mpc scale with the field strength of $\sim 10^{-9}$G at the present time can be generated even for the scale of the effective interaction being the Planck scale.
We study the charmful three-body baryonic B decays with $D^{(*)}$ or $J/Ψ$ in the final state. We explain the measured rates of $\bar B^0\to n\bar p D^{*+}$, $\bar B^0\to p\bar p D^{(*)0}$, and $B^-\to Λ\bar p J/Ψ$ and predict the branching fractions of $\bar B^0\to Λ\bar p D^{*+}$, $\bar B^0\to Σ^0\bar p D^{*+}$, $B^-\toΛ\bar p D^{0}$, and $B^-\toΛ\bar p D^{*0}$ to be of order $(1.2, 1.1, 1.1, 3.9)\times 10^{-5}$, respectively. They are readily accessible to the $B$ factories.
We study the models with radiative neutrino mass generation and explore the relation between the neutrino masses and dark energy. In these models, the pseudo-Nambu-Goldston bosons (pNGBs) arise at two-loop level via the Majorana neutrino masses. In particular, we demonstrate that the potential energy of the pNGB can be the dark energy potential and the observed value of the equation of state (EoS) parameter of the universe, $i.e.$, $w\simeq -1$, can be realized.
We study a new scenario for baryogenesis due to the spontaneous breaking of the $CPT$ invariance through the interaction between a baryon current and a hypermagnetic helicity. The hypermagnetic helicity (Chern-Simons number) of $U(1)_Y$ provides a $CPT$ violation background for the generation of baryons via sphaleron processes, which protects these baryons from the sphaleron wash-out effect in thermal equilibrium. It is shown that if the present amplitude of the resultant magnetic fields are sufficiently large, for a wide range mass scale (from TeV to the Planck scale), the observational magnitude of the baryon asymmetry of the Universe can be realized.
The form factors of the $K^+ \to γ$ transition are studied in the light-front quark model and chiral perturbation theory of $O(p^6)$. The decay spectrum of $K^+ \to e^+ ν_{e}γ$, dominated by the structure dependent contribution, is illustrated in both models.
We review the direct CP and T violation in the three-body baryonic B decays in the standard model. In particular, we emphasize that the direct CP violating asymmetry in $B^\pm\to p\bar p K^{*\pm}$ is around 22% and the direct $T$ violating asymmetry in $\bar B^0 \ra Λ\bar p π^+$ can be as large as 12%, which are accessible to the current B factories at KEK and SLAC as well as SuperB and LHCb.
We demonstrate that the cosmological birefringence can arise from CPT conserving effect, originated from the CPT-even dimension-six Chern-Simons-like term. We show that a sizable rotation polarization angle in the data of the cosmic microwave background radiation polarization can be induced.
We review our recent work on the cosmological birefringence. We propose a new type of effective interactions in terms of the $CPT$-even dimension-six Chern-Simons-like term to generate the cosmological birefringence. We use the neutrino number asymmetry to induce a non-zero rotation polarization angle in the data of the cosmic microwave background radiation polarization.
We study a new type of effective interactions in terms of the $CPT$-even dimension-six Chern-Simons-like term, which could originate from superstring theory, to generate the cosmological birefringence. We use the neutrino number asymmetry to induce a sizable rotation polarization angle in the data of the cosmic microwave background radiation polarization. The combined effect of the new term and the neutrino asymmetry provides an alternative way to understand the birefringence.
We have investigated in detail a model that contains an additional SU(2) singlet and triplet scalar fields than the Standard Model (SM). This allows the radiative generation of Majorana neutrino masses at two-loop order with the help of doubly charged Higgs bosons that arise from the extended Higgs sector. We studied in detail the phenomenology of the Higgs and neutrino sectors of the model. We give the analytical form of the masses of scalar and pseudoscalar bosons and their mixings, and the structure of the active neutrino mass matrix. It is found that the model accommodates only normal neutrino mass hierarchy, and that there is a large parameter space where the doubly charged Higgs can be observed at the LHC, thereby making it testable at the LHC. Furthermore, the neutrino-less double beta ($\nonu$) decays arise predominantly from exchange processes involving the doubly charged Higgs, whose existence is thus unmistakable if $\nonu$ decays are observed. The production and decays of the doubly charged Higgs are analyzed, and distinct and distinguishing signals are discussed.
We study the three-body baryonic B decays of $B\to p\bar{p}(K^{*},ρ)$ in the standard model. The baryonic matrix elements are calculated in terms of the SU(3) flavor symmetry and the QCD power counting rules within the the perturbative QCD. We find that the decay branching ratios, angular and direct CP asymmetries of ($B^{-}\to p\bar{p}K^{*-}, \bar{B}^{0}\to p\bar{p}K^{*0}, B^{-}\to p\bar{p}ρ^{-}$) are around $(6,1,30)\times 10^{-6}$, $(13,-27,11)%$ and $(22,1,-3)%$, which are consistent with the current BaBar and Belle data, respectively. The large values of the branching ratio in $B^{-}\to p\bar{p}ρ^{-}$ and the direct CP asymmetry in $B^{\pm}\to p\bar{p}K^{*\pm}$ are useful to test the standard model and search for new physics.
It is the first time that the study of three-body baryonic B decays offers an independent determination of the nucleon form factors for the time-like four momentum transfer $(t>0)$ region, such as $G^{p,n}_M(t)$ of vector currents and those of axial ones. Explicitly, from the data of $\bar B^0\to n\bar p D^{*+}$ and $Λ\bar pπ^+$ we find a constant ratio of $G^n_M(t)/G^p_M(t)=-1.3\pm0.4$, which supports the FENICE experimental result. The vector and axial-vector form factors of $p\bar n$, $p\bar p$ and $n\bar n$ pairs due to weak currents are also presented, which can be tested in future experiments.
We study a model in which lepton number violation is solely triggered by a dimension 4 hard breaking term in the scalar potential. A minimal model which contains a SU(2) triplet with hypercharge Y=2, and a pair of singlet doubly charged scalar fields in addition to the Standard Model (SM) Higgs doublet is constructed. The model is technically natural in the sense that lepton number is preserved in the limit that the hard term vanishes. SM phenomenology restricts the vacuum expectation value of the triplet scalar field $v_T<5.78$ GeV. Neutrino masses controlled by $v_T$ are generated at the two loop level and are naturally to the sub-eV range. In general they exhibit normal hierarchy structure. Here the neutrino mass term does not dominate neutrinoless double beta decays of nuclei. Instead the short distance physics with doubly charged Higgs exchange gives the leading contribution. We expect weak scale singly and doubly charged Higgs bosons to make their appearances at the LHC and the ILC.
We study the direct CP violation in $B^\pm\to p\bar p K^{(*)\pm}$ decays in the standard model. We point out that these three-body baryonic B decays can be important tools for detecting the direct CP violation in the charged $B$ system, in which there are no conclusive signatures yet. In particular, we show that the direct CP violating asymmetry in $B^\pm\to p\bar p K^{*\pm}$ is around 22% which supports the recent data by the BABAR Collaboration.
We study the angular distributions of the baryon-antibaryon low-mass enhancements in the three-body baryonic B decays of $B\to p\bar{p}M$ (M=K and $π$) in the framework of the perturbative QCD. By writing the most general forms for the transition form factors of $B\to p\bar{p}$, we find that the angular distribution asymmetry in $B^-\to p\bar{p}K^-$ measured by the Belle Collaboration can be explained. We give a quantitative description on the Dalitz plot asymmetry in $B^-\to p\bar{p}K^-$ shown by the BaBar Collaboration and demonstrate that it is equivalent to the angular asymmetry. In addition, we present our results on $\bar B^0\to p\bar{p}K_S$ and $B^-\to p\bar{p}π^-$ and we obtain that their angular asymmetries are $-0.35\pm0.11$ and $0.45\pm0.10$, respectively, which can be tested by the ongoing experiments at the B factories.
The HyperCP collaboration has presented the branching ratio of $Σ^+\to pμ^+μ^-$ to be $(8.6^{+6.6}_{-5.4}\pm 5.5)\times 10^{-8}$ and suggested a new boson $P^0$ with a mass of $214.3\pm 0.5$ MeV to induce the flavor changing transition of $s\to dμ^+μ^-$. We demonstrate that to explain the data, the new particle cannot be a scalar but pseudoscalar based on the direct constraints from $K^+\toπ^+μ^+μ^-$ and $K_L\toμ^+μ^-$, respectively. Moreover, we determine that the decay width of the pseudoscalar should be in the range of $10^{-7}$ MeV with the lifetime of $10^{-14}$ sec.
We study $T$ violation in the three-body charmless baryonic decay of $\bar B^0 \ra Λ\bar p π^+$ through the $T$-odd triple product correlation in the standard model. We find that the $T$ violating asymmetry is 10%, which is accessible to the current B factories at KEK and SLAC, while the CP violating one 1.1%. We emphasize that this triple product correlation would be the first measurable direct $T$ violating effect predicted in the standard model.