In the standard model (SM), we re-investigate the rare decay $B\to ϕπ$, which has been viewed as an ideal probe to detect the new physics signals beyond the SM. Contributions in the naive factorization method, the radiative corrections, the long-distance contributions, and the contributions due to the $ω$-$ϕ$ mixing are taken into account. We find that the tiny branching ratio in the naive factorization can be dramatically enhanced by the radiative corrections and the $ω$-$ϕ$ mixing effect, while the long-distance contributions are negligibly small. Assuming the Cabibbo-Kobayashi-Maskawa angle $γ=(58.6\pm 10)^\circ$ and the mixing angle $θ= -(3.0\pm 1.0)^\circ$, we obtain the branching ratios of $B\to ϕπ$ as $ {\rm Br}(B^\pm\to ϕπ^\pm)= (3.2 ^{+0.8-1.2}_{-0.7+1.8}) \times 10^{-8}$ and $ {\rm Br}(B^0 \to ϕπ^0) = (6.8 ^{+0.3-0.7}_{-0.3+1.0}) \times 10^{-9}$. If the future experiment reports a branching ratio of order $10^{-7}$ for $B^-\to ϕπ^-$ decay, it may not be a clear signal for any new physics scenario. In order to discriminate the large new physics contributions and those due to the $ω$-$ϕ$ mixing, we propose to measure the ratio of branching fractions of the charged and neutral B decay channel. We also study the direct CP asymmetries of these two channels, and the results are about $(-8.0^{+0.9+1.5}_{-1.0-0.1})%$ and $(-6.3^{-0.5+2.5}_{+0.7-2.5})%$ for $B^\pm\to ϕπ^\pm$ and $B^0 \to ϕπ^0$, respectively.
The theoretical calculation for pseudo--scalars hadronic decays $K \to πa$ is reviewed. %with the Axion-Like-Particle escaping the detection, While one-loop penguin contributions are usually considered, tree-level processes have most often been overlooked in literature. Following the Lepage--Brodsky approach the tree-level contribution to the charged and neutral pseudo--scalar decay in ALP is estimated. Assuming generic ALP couplings to SM fermions, the latest NA62/E949 results for the $K^+ \to π^+ a$ decay and the present/future KOTO results for the $K^0_L \to π^0 a$ decay are used to provide…
An exact calculation of the Higgs boson decays $H\to q_i q_j$ mediated by flavor changing neutral currents is presented in the context of the Standard Model. Using up-to-date experimental data, branching ratios of the order of $10^{-7}$, $10^{-8}$, $10^{-8}$, and $10^{-15}$ are found for the $\bar{b}s+\bar{s}b$, $\bar{b}d+\bar{d}b$, $\bar{s}d+\bar{d}s$, and $\bar{c}u+\bar{u}c$ decay modes, respectively.
Some discrepancies between theory and experiment in the B -> pi K decays suggest the possibility of a new physics contribution with the structure of an electroweak penguin amplitude. If such a scenario is realised in nature, the branching ratios of the decays B_s -> phi pi and B_s -> phi rho can be enhanced by about one order of magnitude. We review and update the current status of the B -> pi K puzzle and its implications for the decays B_s -> phi pi and B_s -> phi rho.
We revisit the rare decays of the Higgs boson to two different quarks in the Standard Model, which arise at the one-loop level. We perform Taylor series expansions to the complete form factors of the decay amplitudes, according to their different mass hierarchies, this allow us to take full advantage of the GIM mechanism to eliminate spurious contributions and retain those that truly contribute. We found that Br$(H\to uc)$=$5.00\times10^{-20}$, Br$(H\to ds)$=$1.19\times10^{-11}$, Br$(H\to db)$=$5.16\times10^{-9}$ and Br$(H\to sb)$=$1.15\times10^{-7}$. Our predictions for the $H\to uc,ds$ decay…
We revisit the current experimental bounds on fourth-generation Majorana neutrino masses, including the effects of right handed neutrinos. Current bounds from LEPII are significantly altered by a global analysis. We show that the current bounds on fourth generation neutrinos decaying to eW and mu W can be reduced to about 80 GeV (from the current bound of 90 GeV), while a neutrino decaying to tau W can be as light as 62.1 GeV. The weakened bound opens up a neutrino decay channel for intermediate mass Higgs, and interesting multi-particle final states for Higgs and fourth generation lepton deca…
The semileptonic decays of $Λ_{b}\toΛ_{c}^{(*)}\ellν_\ell$ and $Λ_{c}\toΛ^{(*)}\ellν_\ell$ are studied in the light-front quark model in this work. Instead of the quark-diquark approximation, we use the three-body wave functions obtained by baryon spectroscopy. The ground states $(1/2^{+})$, the $λ$-mode orbital excited states $(1/2^{-})$, and the first radial excited states $(1/2^{+})$ of $Λ_{(c)}^{(*)}$ are considered. The discussions are given for the form factors, partial widths, branching fractions, leptonic forward-backward asymmetries, hadron polarizations, lepton polarizations, and the…
Triggered by experimentally driven renewed interest in hyperon properties we address the subject of weak radiative hyperon decays (WRHD). We start with the issue of Hara's theorem and briefly discuss the question of its possible evasion. Then, we give a short review of the story of vector-meson-dominance (VMD) approach to WRHD. We stress the shift from the Hara's-theorem-violating to Hara's-theorem-satisfying version of the VMD approach that did occur over time. Finally, spurred by a recent theoretical paper, we discuss the pole model description of WRHD, putting special attention to the issue…
We study the $ρπ$ and $b_1π$ decay modes of the $1^{-+}$ light hybrid state within the framework of light-cone QCD sum rules. We use both the tensor current $\barψσ_{μν}ψ$ and the derivative current $\barψ\overleftrightarrow{D}_μγ_5ψ$ as interpolating currents to calculate the partial decay width of the $b_1π$ decay mode. Comparing the sum rules obtained by using different currents, we obtain $Γ(π_1\to b_1π)$ = 8--23, 32--86 and 52--151\,MeV for $m_{1^{-+}}$ = 1.6, 1.8 and 2.0\,GeV respectively, which favour the results from the flux tube models and lattice simulations. We also use the tensor …
We recalculate the branching ratio and CP asymmetry for $\bar{B}^{0} (B^{0})\to π^{0}π^{0}$ decays in the Perturbative QCD approach. In this approach, we consider all the possible diagrams including non-factorizable contributions and annihilation contributions. We obtain $Br(\bar{B}^{0} (B^{0})\to π^{0}π^{0})=(1.17_{-0.12}^{+0.11})\times 10^{-6}$. Our result is in agreement with the latest measured branching ratio of $B^{0}\toπ^{0}π^{0}$ by the Belle and HFAG Collaborations. We also predict large direct CP asymmetry and mixing CP asymmetry in $B^{0}\toπ^{0}π^{0}$ decays, which can be tested by…
We revisit the calculation of nonfactorizable corrections induced by charm-quark loops in exclusive FCNC $B$-decays. For the sake of clarity, we make use of a field theory with scalar particles: this allows us to focus on the conceptual issues and to avoid technical complications related to particle spins in QCD. We perform a straightforward calculation of the appropriate correlation function and show that it requires the knowledge of the full generic three-particle distribution amplitude with non-aligned arguments, $\langle 0|\bar s(y)G_{μν}(x)b(0)|B(p)\rangle$. Moreover, the dependence of th…
Large Isospin mixing in phi radiative decay and the spatial size of the f0(980)- a0(980) meson
测量到的phi到gamma f0（980）的速率似乎大于一般情况下允许的速率。我们发现，f0（980）和a0（980）之间的混合，由于其与附近的KKbar阈值的动力学相互作用，从根本上影响了一些现有的预测其生产的phi辐射衰变。我们预测Gamma（phi to gamma f0）/Gamma（phi to gamma a_0）约为3; (phi至γ f0）+ b.r. (phi与γ a_0））< 5 x 10^-4，可能的单个分支比分别为2 x 10^-4和0.7 x 10^-4。
We study lifetimes of heavy mesons in the 't Hooft model, a large-$N_c$ theory of strong interaction in two-dimensional spacetime. Since this model is solvable, one can evaluate the total decay widths through hadronic amplitudes that are determined unambiguously within the formalism. We investigate quark-hadron duality by numerically comparing the exclusive result and one from the heavy quark expansion, with the contribution of Pauli interference being consistently incorporated. Within certain numerical accuracy, we find that the maximal difference between inclusive and exclusive rates for $τ[…
In this paper, we summarize the existing methods of solving the evolution equation of the leading-twist $B$-meson LCDA. Then, in the Mellin space, we derive a factorization formula with next-to-leading-logarithmic (NLL) resummation for the form factors $F_{A,V}$ in the $B \to γ\ellν$ decay at leading power in $Λ/m_b$. Furthermore, we investigate the power suppressed local contributions, factorizable non-local contributions (which are suppressed by $1/E_γ$ and $1/m_b$), and soft contributions to the form factors. In the numerical analysis, which employs the two-loop-level hard function and the …
We revisit the calculation of the width for the radiative decay of a $1^{+-}$ heavy $Q \bar Q$ meson via the channel $1^{+-} \to 0^{-+} +γ$ in the covariant light-front quark model. We carry out the reduction of the light-front amplitude in the non-relativistic limit, explicitly computing the leading and next-to-leading order relativistic corrections. This shows the consistency of the light-front approach with the non-relativistic formula for this electric dipole transition. Furthermore, the theoretical uncertainty in the predicted width is studied as a function of the inputs for the heavy qua…
We calculate the branching ratios and CP asymmetries of the $B \to πρ$, $πω$ decays in the perturbative QCD factorization approach up to the next-to-leading-order contributions. We find that the next-to-leading-order contributions can interfere with the leading-order part constructively or destructively for different decay modes. Our numerical results have a much better agreement with current available data than previous leading-order calculations, e.g., the next-to-leading-order corrections enhance the $B^0\rightarrow π^0ρ^0$ branching ratios by a factor 2.5, which is helpful to narrow the ga…
Motivated by the large rates of $B\rightarrow (χ_{c0}, χ_{c2}, h_c)K$ decays observed by the $BABAR$ and Belle collaborations, we investigate the nonfactorizable contributions to these factorization-forbidden decays, which can occur through a gluon exchange between the $c\bar c$ system and the spectator quark. Our numerical results demonstrate that the spectator contributions are capable of producing a large branching ratio consistent with the experiments. As a by-product, we also study the Cabibbo-suppressed decays, such as $B\rightarrow (χ_{c0}, χ_{c2}, h_c)π$ and the U-spin-related $B_s$ de…
We reinvestigate the scenario that the amount of the baryons and the gravitino dark matter is naturally explained by the decay of the Q balls in the gauge-mediated SUSY breaking. Equipped by the more correct decay rates into gravitinos and baryons recently derived, we find that the scenario with the direct production of the gravitino dark matter from the Q-ball decay works naturally.
Motivated by the reported discrepancies between experimental data and Standard Model predictions for the branching ratios of the color-allowed decays $\overline{B}^0 \to D^{(*)+}K^-$ and $\overline{B}^0_s \to D^{(*)+}_s π^-$, we study final-state rescattering effects on $\overline{B}_{(s)}\to D^{(*)}_{(s)} P$ and $\overline{B}_{(s)}\to D_{(s)} V$, where $P$ ($V$) is a light pseudoscalar (vector) meson. We consider quasi-elastic rescatterings in the framework of $SU(3)$ and $U(3)$ flavor symmetries, and find that the effects cannot explain the measured branching ratios of the color-allowed and …
Determining for the first time the Darwin operator contribution for the non-leptonic charm-quark decays and using new non-perturbative results for the matrix elements of $ΔC=0$ four-quark operators, including eye-contractions, we present a comprehensive study of the lifetimes of charmed mesons and inclusive semileptonic decay rates as well as the ratios, within the framework of the Heavy Quark Expansion (HQE). We find good agreement with experiment for the ratio $τ(D^+)/τ(D^0)$, for the total $D_s^+$-meson decay rate, for the semileptonic rates of all three mesons $D^0$, $D^+$ and $D_s^+$, and…
The discovery of a light, singlet-like pseudoscalar Higgs boson, $A_1$, of the Next-to-Minimal Supersymmetric Standard Model (NMSSM) could provide a hallmark signature of non-minimal supersymmetry. We review here the potential of the LHC to probe such a light $A_1$ in the decays of one of the heavier scalar Higgs bosons of the NMSSM. We find the production of pairs of the $A_1$, with a mass below 60 GeV or so, via decays of the two lightest scalar states to be especially promising, for an integrated luminosity as low as 30/fb. For heavier masses, the decay of the heaviest scalar into a $Z$ bos…
