In this paper, we study the lepton number violation processes of $B_c$ meson induced by possible doubly-charged scalars. Both the three-body decay channels and the four-body decay channels are considered. For the former, $Br\times\left(\frac{s_Δh_{ij}}{M_Δ^2}\right)^{-2}$ is of the order of $10^{-7}\sim 10^{-9}$, and for the later channels, $Br\times\left(\frac{s_Δh_{ij}}{M_Δ^2}\right)^{-2}$ is of the order of $10^{-12}\sim 10^{-20}$, where $s_Δ$, $h_{ij}$, $M_Δ$ are the constants related to the doubly-charged boson.
Using the most general form of the interpolating current for baryons, the strong electric and magnetic coupling constants of light vector mesons $ ρ$ and $ K^* $ with doubly heavy baryons are computed within the light-cone sum rules. We consider 2- and 3-particle distribution amplitudes of the aforementioned vector mesons. The obtained results can be useful in the analysis of experimental data on the properties of doubly heavy baryons conducted at LHC.
The strong coupling constant of doubly heavy baryons with light pseudoscalar mesons $ π$ and $ K $ are computed within the light cone sum rules. We take into account two-particle and three-particle distribution amplitudes of the said pseudoscalar mesons. We compare our result with the one existing in the literature.
In the paper we discuss contribution of the doubly intrinsic heavy mechanism into the production of $B_c$ meson, the doubly heavy baryons and the all-charm tetraquark at a future fixed-target experiment at the LHC (AFTER@LHC). The production cross sections and the mean values of Feynman-x for the finale states are presented.
In this paper, we analyze the doubly heavy spin-3/2--spin-1/2 baryons and light meson vertices within the method of light-cone QCD sum rules. These vertices are parametrized in terms of one (three) coupling constant(s) for the pseudoscalar (vector) mesons. The said coupling constants are calculated for all possible transitions. The results presented here can serve to be useful information in experimental as well as theoretical studies of the properties of doubly heavy baryons.
The lepton-number-violating decays of $B^+, D^+$ and $D_s^+$ mesons induced by the doubly charged Higgs boson have been studied. It is found that although the yielded results of the branch ratio are much smaller than the present limits from the data they are consistent with the previous conclusions calculated in the framwork of relativistic quark model where the processes happened via the light Majorana neutrinos.
Several observed states close to the $D\bar{D}^*$ and $D^*_{(s)}\bar{D}^*_{(s)}$ thresholds, as the X(3872) and some XYZ particles can be described in terms of a two-meson molecule. Furthermore, doubly charmed states are also predicted. These new states are near the $D^*D^*$ and $D^*D^*_s$ thresholds, % Therefore, if the previous XYZ are molecules, then, there should be doubly charmed mesons with $J^P=1^+$ around the $D^*D^*$ threshold. %For this reason, it is important to evaluate observables related to them. Because of the spin$=1$, they do not decay into $DD$. In this article we compute dec…
In the presented article we consider exclusive weak decays of doubly heavy baryons with spin $J=1/2$ with production of leptonic pair or a set of light mesons. Using QCD factorization theorem and spectral functions approach we obtain theoretical predictions for the partial probabilities of these decays and distributions over various kinematic variables. According to the obtaining results partial probabilities of some of researched decays are large enough to be observed experimentally.
We prove a U-spin amplitude triangle relation among doubly Cabibbo-suppressed (DCS) charmed meson decays, $D^0\to K^+π^-, D^0 \to K^0π^0$ and $D^+_s \to K^0 K^+$, congruent to an isospin relation among corresponding Cabibbo-favored (CF) decays. U-spin breaking in relative phases between CF and DCS amplitudes affects time-dependent studies of $D^0-\od$ mixing. Comparison of final state phase patterns in DCS and CF amplitude triangles, which can shed some light on these phases, is carried out in a phenomenological framework incorporating resonance contributions.
Doubly heavy mesons and baryons provide a good platform for testing pQCD. Two generators BCVEGPY and GENXICC for simulating the hadronic production of the doubly heavy mesons and baryons have been developed in recent years. In this talk, we present their main idea and their recent progresses. The dominant gluon-gluon fusion mechanism programmed in those two generators are written based on the improved helicity amplitude approach, in which the hard scattering amplitude are dealt with directly at the amplitude level and the numerical efficiency are greatly improved by properly decomposing the Fe…
On the basis of the perturbative QCD and the relativistic quark model we investigate the relativistic and bound state effects in the production processes of a pair of $S$-wave doubly heavy mesons with opposite charge conjugation consisting of $b$ and $c$ quarks. All possible relativistic corrections in the production amplitude including the terms connected with the transformation law of the bound state wave function to the reference frame of the moving pseudoscalar ${\cal P}-$ and vector ${\cal V}-$ mesons are taken into account. We obtain a growth of the cross section for the reaction $e^++e^…
Cabibbo-favored nonleptonic charmed particle decays exhibit large final-state phase differences in $\bar K π$ and $\bar K^* π$ but not $\bar K ρ$ channels. It is of interest to know the corresponding pattern of final-state phases in doubly-Cabibbo-suppressed decays, governed by the $c \to d u \bar s$ subprocess. An experimental program is outlined for determining such phases via measurements of rates for $D \to K^* π$ and $K (ρ, ω,ϕ)$ channels, and determination of interference between bands in Dalitz plots. Such a program is feasible at planned high-intensity sources of charmed particles.
Doubly charmed mesons are studied within a quark model framework. We solve the four-quark Schordinger equation by means of a variational approach by using different interacting potentials. Our results point to the existence of a stable isoscalar doubly charmed four-quark meson with quantum numbers $J^P=1^+$.
In the framework of the chiral quark model along with complex scaling range, we perform a dynamical study on the low-lying $S$-wave doubly-heavy tetraquark states ($QQ\bar{q}\bar{q}$, $Q=c, b$ and $q=u, d$) with an accurate computing approach, Gaussian expansion method. The meson-meson and diquark-antidiquark configurations within all possible color structures for spin-parity quantum numbers $J^P=0^+$, $1^+$ and $2^+$, and in the $0$ and $1$ isospin sectors are considered. Possible tightly bound and narrow resonance states are obtained for doubly-charm and doubly-bottom tetraquarks with $IJ^P=…
Inspired by the observation of the doubly charmed tetraquark state $T_{cc}^+$ at the LHCb Collaboration, we systematically study the $S$-wave interactions between a pair of charmed mesons ($D_{1},\,D_{2}^{\ast}$) in the $T$-doublet, where we adopt the one-boson-exchange model and consider both the $S$-$D$ wave mixing and coupled channel effects. Our numerical results suggest that the prime doubly charmed molecular tetraquark candidates are the $S$-wave $D_1D_1$ state with $I(J^P)=0(1^+)$, the $S$-wave $D_1{D}_2^{\ast}$ states with $I(J^P)=0(1^+,\,2^+,\,3^+)$, and the $S$-wave ${D}_2^{\ast}{D}_…
In this paper, we study the four-body decay processes of neutral flavored mesons, including $\bar K^0$, $D^0$, $\bar B^0$, and $\bar B_s^0$. These processes, which induced by a hypothetical doubly-charged scalar particle, violate the lepton number. The quantity $Br\times\left(\frac{s_Δh_{ij}}{m_Δ^2}\right)^{-2}$ of different channels are calculated, where $s_Δ$, $h_{ij}$, and $M_Δ$ are parameters related to the doubly-charged scalar. For $\bar K^0\rightarrow h_1^+h_2^+l_1^-l_2^-$, $D^0\rightarrow h_1^-h_2^-l_1^+l_2^+$, and $\bar B_{d,s}^0\rightarrow h_1^+h_2^+l_1^-l_2^-$, it is of the order of…
Rates for productions of neutral and doubly charged partners of D_{s0}^+(2317) in B meson decays are studied by using a hard D meson approximation in the infinite momentum frame, and the results are of the same order of magnitude as that of D_{s0}^+(2317). Because the bottom-strange X^{+-}(5568) which can be interpreted as iso-triplet bottom partners of D_{s0}^+(2317) have recently been discovered, observations of neutral and doubly charged partners of D_{s0}^+(2317) are strongly desired.
The analysis of singly charmed hadrons has been extended to the case of doubly charmed baryons, $Ξ_{cc}^{++}$, $Ξ_{cc}^{+}$ and $Ω_{cc}^{+}$. Doubly charmed baryons are described as a system containing a heavy $cc$-diquark and a light quark, similarly as in a heavy-light meson. This leads to preasymptotic effects in semileptonic and nonleptonic decays which are essentially proportional to the meson wave function. Interplay between preasymptotic effects in semileptonic and/or nonleptonic decay rates leads to very clear predictions for semileptonic branching ratios and lifetimes of doubly charme…
Stimulated by the new experimental LHCb findings associated with the $Ω_c$ states, some of which we have described in a previous work as being dynamically generated through meson-baryon interaction, we have extended this approach to make predictions for new $Ξ_{cc}$ molecular states in the $C=2$, $S=0$ and $I=1/2$ sector. These states manifest themselves as poles in the solution of the Bethe-Salpeter equation in coupled channels. The kernels of this equation were obtained using the Lagrangians coming from the hidden local gauge symmetry, where the interactions are dominated by the exchange of …
Inspired by the recent observation of a very narrow state, called $T_{cc}^+$, by the LHCb collaboration, the possible bound states and low-lying resonance states of the doubly heavy tetraquark states $cc\bar{u}\bar{d}$ ($T_{cc}$) and $bb\bar{u}\bar{d}$ ($T_{bb}$) are searched in the framework of chiral quark model with an accurate few body method, Gaussian expansion method. The real scaling method is also applied to identify the genuine resonance states. In the calculation, the meson-meson structure, diquark-antidiquark structure, as well as their coupling are all considered. The numerical res…
The three pentaquark states, $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, discovered by the LHCb Collaboration in 2019, can be arranged into a complete heavy quark spin symmetry multiplet of hadronic molecules of $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$. In the heavy quark mass limit, the $Σ_{c}^{(\ast)}$ baryons can be related to the doubly charmed tetraquark states of isospin 1, i.e., $T_{\bar{c}\bar{c}}^{(\ast)}$( $T_{\bar{c}\bar{c}}^{0}$, $T_{\bar{c}\bar{c}}^{1}$, $T_{\bar{c}\bar{c}}^{2}$), via heavy antiquark diquark symmetry, which dictates that the $\bar{D}^{(\ast)}Σ_{c}^{(\ast)}$ interactions are…
Rare decays of the B-meson that arise due to loop-mediated FCNC transitions are known to provide important constraints on beyond-SM theories. Basic properties of several such decays are reviewed here.
Stimulated by the newly reported doubly-charmed tetraquark state $T_{cc}^+$ by LHCb, we carry out a systematic investigation of the $S$-wave interactions between the charmed meson ($D,\,D^{*}$) in $H$-doublet and the charmed meson ($D_{1},\,D_{2}^{*}$) in $T$-doublet by adopting the one-boson-exchange model. Both the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. By performing a quantitative calculation, we suggest that the $S$-wave $D^{*} D_{1}$ states with $I(J^{P})=0(0^{-},\,1^{-})$ and the $S$-wave $D^{*}D_{2}^{*}$ state with $I(J^{P})=0(1^{-})$ should be…
The problem of $ρ$- and $ω$- mesons contributions to the background for $η\to π^0 e^+e^-$ decay and to the asymmetries in the decays $η\to π^+π^-π^0$ and $η\to π^+π^-γ$ is considered.
The strong coupling constants are basic quantities that carry information of the strong interactions among the baryon and meson multiplets as well as information on the natures and internal structures of the involved hadrons. These parameters enter to the transition matrix elements of various decays as main inputs and they play key roles in analyses of the experimental data including various hadrons. We determine the strong coupling constants among the doubly heavy spin-$ 3/2 $ baryons, $Ξ^*_{QQ'} $ and $Ω^*_{QQ'}$, and light pseudoscalar mesons, $π$, $K$ and $η$, using the light-cone QCD. The…
The interaction between pseudoscalar and/or vector mesons can be studied using hidden gauge Lagrangians. In this framework, the interaction between charmed mesons has been studied. Furthermore, doubly charmed states are also predicted. These new states are near the $D^*D^*$ and $D^*D^*_s$ thresholds, and have spin-parity $J^P=1^+$. We evaluate the decay widths of these states, named as $R_{cc}(3970)$ and $S_{cc}(4100)$ (with strangeness), and obtain $44$ MeV for the non-strangeness, and $24$ MeV for the doubly charm-strange state. Essentially, the decay modes are $DD_{(s)}π$ and $DD_{(s)}γ$, b…
By studying the decays D_{s0}^+(2317) --> D_s^+ pi^0 and D_s^{*+} gamma, It is shown that its assignment to the I_3=0 component of iso-triplet scalar four-quark mesons is favored. Productions of its neutral and doubly charged partners are also studied. As the result, it is concluded that they could be observed in B decays. Their iso-singlet partner might have been observed in the radiative channels of B decays by the BELLE Collaboration.
In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decays B => πl nu and B => K l+ l-. The present calculation extends a previous analysis of B meson decays into light vector mesons. We find results in agreement with the data, when available, and with the theoretical constraints imposed by the Callan-Treiman relation and the infinite heavy quark mass limit.
Some semileptonic weak decays of vector mesons are considered in the framework of the most popular quark models. The predicted branching ratios are unfortunately too small to make a study of these decays realistic at meson factories under construction.
We study the contribution of 2nd generation of quarks in NSIs. We investigate it through the rare decays of mesons involving neutrinos in the final state. We show the C and s quarks can effect NSIs just like u and s. We explore constraints on free parameter of NSIs. For this purpose we select 6 FCNC semi-leptonic processes of B, D and K mesons having neutrinos in the final state
We calculate the strong coupling constants among the doubly heavy spin-$ \frac{3}{2} $ baryons $Ξ^*_{QQ}$ and $Ω^*_{QQ}$, with $ Q $ and $ Q' $ being $ c$ or $ b $ quark, with light vector meson by means of the light-cone QCD sum rules. The matrix elements defining these vertices are described by four coupling constants $ g_1$, $ g_2$, $ g_3$, and $ g_4 $. The unwanted pollution coming from the doubly heavy spin-$ \frac{1}{2} $ baryons are removed by a special ordering of Dirac matrices and selection of appropriate Lorentz structures. The strong coupling constants are basic parameters that car…
The strong coupling constants of hadronic multiplets are fundamental parameters which carry information of the strong interactions among participating particles. These parameters can help us construct the hadron-hadron strong potential and gain information about the structure of the involved hadrons. Motivated by the recent observation of the doubly charmed $Ξ_{cc}$ state by LHCb, we determine the strong coupling constants among the doubly heavy spin-1/2 baryons, $ Ξ^{(\prime)}_{QQ^\prime }$, $ Ω^{(\prime)}_{QQ^\prime}$ and light pseudoscalar mesons, $ π$, $ K $, $η$ and $ η^\prime $ within th…
We discuss questions related to the application of OPE for the long-lived systems with two heavy flavors. The values of quark masses entering such calulations are constrained by use of currently available data on the lifetimes of $B_d$ and $B_c$-mesons. The lifetimes of doubly charmed baryons at these values of parameters are evaluated. The necessary comments on the difference in the results obtained previously are made.
We predict several new exotic doubly-heavy hadronic resonances, inferring from the observed exotic bottomonium-like and charmonium-like narrow states $X(3872)$, $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$, and $Z_c(4020/4025)$. We interpret the binding mechanism as mostly molecular-like isospin-exchange attraction between two heavy-light mesons in a relative S-wave state. We then generalize it to other systems containing two heavy hadrons which can couple through isospin exchange. The new predicted states include resonances in meson-meson, meson-baryon, baryon-baryon, and baryon-antibaryon channel…
We study the $B_C$ meson rare decay in order to search for the Majorana neutrino signal. It is found that the the corresponding decay rate is sensitive to the Majorana neutrino mass and mixing angles. The signal of $B_C^\pm\to l_1^\pm l_2^\pm M^\mp $ induced by the Majorana neutrino within the mass region $m_π<m_n<m_B$ may be observed at LHCb.
Rare flavour-changing neutral-current transitions of the type $s \to d \ell^+\ell^-(ν\barν)$ and $b \to s \ell^+\ell^-(ν\barν)$ are analysed in supersymmetric extensions of the Standard Model with generic flavour couplings. It is shown that these processes are particularly sensitive to the left--right mixing of the squarks and that, in the presence of non-universal $A$ terms, they could lead to unambiguous signatures of new physics in exclusive $K$ and $B$ meson decays.
In this article we study the rare B-meson decay via two on-shell almost-degenerate Majorana Heavy Neutrinos, into two charged leptons and two pseudoscalar mesons ($B^{\pm} \to D^0 \ell^{\pm}_1 \ell^{\pm}_2 π^{\mp}$). We consider the scenario where the heavy neutrino masses are $\sim 2$ GeV and the heavy-light mixing coefficients are $|B_{\ell N}|^2 \sim 10^{-5}$, and evaluate the possibility to measure the CP-asymmetry at Belle II. We present some realistic conditions under which the asymmetry could be detected.
Some recent progress in China in the study of charmless B decays with QCD factorization is reviewed. Chirally enhanced power corrections and infrared divergence problem are stressed.
We present the first complete results for the semileptonic and rare radiative form factors of B-mesons weak decay into a light vector-meson (rho, omega, K*, phi) in the light-cone sum-rule approach. The calculation includes radiative corrections, higher-twist corrections and SU(3)-breaking effects. The theoretical uncertainty is investigated in detail. A simple parametrization of the form factors is given in terms of three parameters each. We find that the form factors observe several relations inspired by heavy-quark symmetry.
The doubly charmed $Ξ_{cc}^{++} (ccu)$ state is the only listed baryon in PDG, which was discovered in the experiment. The LHCb collaboration gets closer to discovering the second doubly charmed baryon $Ξ_{cc}^{+} (ccd)$, hence the investigation of the doubly charmed/bottom baryons from many aspects is of great importance that may help us not only get valuable knowledge on the nature of the newly discovered states, but also in the search for other members of the doubly heavy baryons predicted by the quark model. In this context, we investigate the strong coupling constants among the $Ξ_{cc}^{+…
Anomalous couplings of the $Z$ boson to top quarks are only marginally constrained by direct searches and are still sensitive to new particle dynamics at the TeV scale. Employing an effective field theory approach we consider the dimension-six operators which generate deviations from the standard-model vector and axial-vector interactions. We show that rare $B$ and $K$ meson decays together with electroweak precision observables provide strong constraints on these couplings. We also consider constraints from t-channel single-top production.
In this paper we study the scattering amplitudes of $D^{0}D^{0}π^+$-$D^{*+}D^{0}$ coupled channels based on $K$-matrix within the Chew-Mandelstam formalism. The $D^{0}D^{0}π^{+}$ invariant mass spectrum of LHCb is fitted and the pole parameters of the $T_{cc}^+$ are extracted. The analysis of pole behavior suggests that the $T_{cc}^+$ may originate from a $D^{*+}D^{0}$ virtual state and is formed as a result of an interplay between an attractive interaction between $D^0$ and $D^{*+}$ and coupling to $D^{0}D^0π^+$ channel.
These lectures describe CP violation and rare decays of K and B mesons and consist of ten chapters: i) Grand view of the field including CKM matrix and the unitarity triangle, ii) General aspects of the theoretical framework, iii) Particle-antiparticle mixing and CP violation, iv) Standard analysis of the unitarity triangle, v) The ratio epsilon'/epsilon including most recent developments, vi) Rare decays K^+ -> pi^+ nu barnu and K_L -> pi^0 nu barnu, vii) Express review of other rare decays, viii) Express review of CP violation in B decays, ix) A brief look beyond the Standard Model including…
We study some rare decays of $B_s$ meson governed by the quark level transitions $ b \to s$, in the fourth generation model popularly known as SM4. Recently it has been shown that SM4, which is a simple extension of the SM3, can successfully explain several anomalies observed in the CP violation parameters of $B$ and $B_s$ mesons. We find that in this model due to the additional contributions coming from the heavy $t'$ quark in the loop, the branching ratios and other observables in rare $B_s$ decays deviate significantly from their SM values. Some of these modes are within the reach of LHCb e…
We discuss rare meson decays $K^ + \to π^ - \ell ^ + \ell '^ + $ and $D^ + \to K^ - \ell ^ + \ell '^ +$ ($\ell, \ell'=e, μ$) in a supersymmetric extension of the Standard Model with R-parity violation. Estimates of the branching ratios for these decays are presented.
We consider a scenario of Low Scale Seesaw where the masses of its heavy Majorana neutrinos are arranged in a pattern of three pairs of quasi degenerate ones, in the range of O(1-6 GeV). Since they can violate lepton number by two units, they contribute to rare decays of Ds and Bc mesons, providing, besides, conditions for maximal CP violation. We found that new phenomenology is possible depending on how many of on-shell pairs mediate these decays. In particular, we present new constraints on muon-heavy neutrinos mixing parameters.
The rare decays of mesons are higher order effects in weak interactions. The main contributions to such decay processes are from the Z-penguin, the photonpenguin and the box diagram. At the quark level, these contributions are well known. However, when considering the corresponding physical hadronic processes, a knowledge of how hadronic states are expressed in terms of quarks. In this paper, we suggest a simplistic way to relate the quark level process to the hadronic process. For simplicity, we consider here only the decays of pseudoscalar mesons. The meson-quark coupling is described in ter…
We analyze the dominant decay mechanisms in the radiative decays D -> V gamma, D -> P(V) l+ l-, D -> gamma gamma, D -> l+ l- gamma, and we discuss possible chances to observe the effects of new physics in these decays. Then we comment on Cabibbo allowed D -> K pi gamma decays with nonresonant K pi and we probe the role of light vector mesons in these decays.
We analyze the rare semileptonic $B_s \to (η, η') l^+ l^-$, $(l=e, μ, τ)$ and $B_s \to (η, η') ν\barν$ transitions probing the $\bar s s$ content of the $η$ and $η'$ mesons via three--point QCD sum rules. We calculate responsible form factors for these transitions in full theory. Using the obtained form factors, we also estimate the related branching fractions and longitudinal lepton polarization asymmetries. Our results are in a good consistency with the predictions of the other existing nonperturbative approaches.
We discuss the extension of the superflavor symmetry of doubly heavy baryons to states which contain an excited heavy diquark, and we examine some of the consequences of this symmetry for the spectra of doubly heavy baryons and heavy mesons. We explore the ramifications of a proposed symmetry that relates heavy diquarks to doubly heavy mesons. We present a method for determining how the excitation energy of a system containing two heavy quarks will scale as one changes the strength of the interactions and the reduced mass of the system. We use this to derive consequences of the heavy diquark-d…
In this work, we use the QCD sum rule method to study the radiative decays of the vector and axial-vector $B_c$ mesons to each of three charmed strange mesons, $D_s$, $D^*_s$ and $D_{s1}$, through their dominant weak annihilation channels. We calculate all relevant transition form factors, which are used to estimate the branching fractions at different channels. The order of branching ratios are obtained to be in the order of $ 10^{-6} - 10^{-5} $, which may be checked via differnet experiments.
We discuss rare meson decays $K^ + \to π^ - \ell ^ + \ell '^ +$ and $D^ + \to K^ - \ell ^ + \ell '^ +$ ($\ell ,\ell ' = e,μ$) in a supersymmetric extension of the standard model with explicit breaking of R-parity by bilinear Yukawa couplings in the superpotential. Estimates of the branching ratios for these decays are given. We also compare our numerical results with analogous ones previously obtained for two other mechanisms of lepton number violation: exchange by massive Majorana neutrinos and trilinear R-parity violation.
