Search

The $s\to u$ weak decays of heavy flavor hadrons play a unique role in the field of heavy flavor physics. In this work, we investigate the $s\to u$ decays of singly heavy baryons. We first obtain the form factors in the light-front approach under the three-quark picture, and then apply them to give some predictions on the semileptonic decays. Due to the extremely small phase space, lepton flavor universality (LFU) is sensitive to the masses of leptons, and precise measurement of LFU is expected to be an important tool for testing the standard model. We find that a commonly used method for extracting form factors in the literature is no longer applicable at this time. We also point out the correct way to thoroughly discuss the heavy quark limit for these decays., Comment: 19 pages, no figures, 5 tables

In the literature, the neutrino $\mu$-$\tau$ reflection symmetry (which has the interesting predictions $\theta^{}_{23} =\pi/4$ and $\delta = \pm \pi/2$ for the atmospherical neutrino mixing angle and Dirac CP phase) is an attractive and widely studied candidate for the flavor symmetries in the neutrino sector. But it is known that, when the seesaw model is furnished with this symmetry, the leptogenesis mechanism (which provides an elegant explanation for the baryon-antibaryon asymmetry of the Universe) can only work in the two-flavor regime (which only holds for the right-handed neutrino masses in the range $10^9-10^{12}$ GeV). This prohibits us to have a low scale seesaw model (which has the potential to be directly accessed by running or upcoming collider experiments) that can have the $\mu$-$\tau$ reflection symmetry and successful leptogenesis simultaneously. In this paper, for the first time, we demonstrate that the successful leptogenesis may also be achieved in low scale seesaw models furnished with the $\mu$-$\tau$ reflection symmetry, by means of the flavor non-universality of the conversion efficiencies from the flavored lepton asymmetries to the baryon asymmetry via the sphaleron process. We perform the study in both the resonant leptogenesis regime and the leptogenesis via oscillations (ARS leptogenesis) regime., Comment: arXiv admin note: text overlap with arXiv:2407.18285, arXiv:2403.18630

In the literature, motivated by the observed peculiar neutrino mixing pattern and a preliminary experimental hint for maximal Dirac CP phase (i.e., $\delta \sim 3\pi/2$), a lot of flavor and CP symmetries have been proposed to help us understand and explain these experimental results. However, for some flavor-symmetry scenarios (see section~3.1), the leptogenesis mechanism is prohibited to work as usual. To tackle this problem, in this paper we have made an exhausitive study on the possibility that the renormalization group evolution effect may induce a successful leptogenesis for these particular scenarios. Our study provides some complementarities to the previous related studies in Refs. [26, 27, 28] (see section~3.2)., Comment: 42 pages, 14 figures. version accepted for publication in PRD. arXiv admin note: text overlap with arXiv:2405.02804, arXiv:2403.18630

In traditional QCD sum rules, the simple hadron spectral density model of ``delta-function-type ground state + theta-function-type continuous spectrum" determines that there is no perfect parameter selection. In recent years, inverse problem methods, especially the inverse matrix method, have shown better handling of QCD sum rules. This work continues to develop the inverse matrix method. Considering that the narrow-width approximation may still be a good approximation, we separate the contribution of the ground state from the spectral density. Then follow the general steps of the inverse matrix method to extract physical quantities such as decay constants that we are sometimes more interested in., Comment: 13 pages, 6 figures

We investigate the purely non-factorizable $\Lambda_{c}^{+}\to\Xi^{0}K^{+}$ decay using light-cone sum rules. To extract the decay amplitudes, a three-point correlation function is defined and calculated at hadron and quark-gluon level, respectively. Both the W-exchange and the W-inward emission diagrams are considered in the quark-gluon level calculation, where the two-particle light-cone distribution amplitudes (LCDAs) of kaon are used as non-perturbative input. We obtain the decay amplitudes contributed from the twist-2 and twist-3 kaon LCDAs, respectively. The obtained P-wave amplitude is consistent with those predicted in the literature, while the S-wave one is much smaller. This significant difference between the S- and P- wave amplitudes leads to small up-down spin asymmetry, closing to the experimental measurement., Comment: 13 pages, 6 figures, 3 tables

In this paper, we have studied the consequences of some representative modular symmetry neutrino models for tri-resonant leptogenesis (which is realized by having three nearly degenerate right-handed neutrinos). To be specific, we have considered modular ${\rm A}^{}_4$, ${\rm S}^{}_4$ and ${\rm A}^{}_5$ symmetry models that have a right-handed neutrino mass matrix $M^{}_{\rm R}$ as shown in Eq.~(\ref{5}) which gives three degenerate right-handed neutrino masses and consequently prohibits the leptogenesis mechanism to work. For these models, we have considered two minimal ways to generate the desired small mass splittings among the three right-handed neutrinos: one scenario is to modify $M^{}_{\rm R}$ to a form as shown in Eq.~(\ref{7}), while another scenario is to consider the renormalization-group corrections for the right-handed neutrino masses. In the former scenario, for the considered models, the observed value of $\eta^{}_{\rm B}$ can always be successfully reproduced for appropriate values of $\mu$. But in the latter scenario not all the considered models can successfully reproduce the observed value of $\eta^{}_{\rm B}$.

In this paper, we have studied the consequences of the $\mu$-$\tau$ reflection symmetry for leptogenesis in the type-I seesaw model with diagonal Dirac neutrino mass matrix. We have first obtained the phenomenologically allowed values of the model parameters, which show that there may exist zero or equal entries in the Majorana mass matrix for the right-handed neutrinos, and then studied their predictions for three right-handed neutrino masses, which show that there may exist two nearly degenerate right-handed neutrinos. Then, we have studied the consequences of the model for leptogenesis. Due to the $\mu$-$\tau$ reflection symmetry, leptogenesis can only work in the two-flavor regime. Furthermore, leptogenesis cannot work for the particular case of $r=1$. Accordingly, for some benchmark values of $r \neq 1$, we have given the constraints of leptogenesis for relevant parameters. Furthermore, we have investigated the possibilities of leptogenesis being induced by the renormalization group evolution effects for two particular scenarios. For the particular case of $r=1$, the renormalization group evolution effects will break the orthogonality relations among different columns of $M^{}_{\rm D}$ and consequently induce leptogenesis to work. For the low-scale resonant leptogenesis scenario which is realized for nearly degenerate right-handed neutrinos, the renormalization group evolution effects can break the $\mu$-$\tau$ reflection symmetry and consequently induce leptogenesis to work., Comment: 26 pages, 10 figures, version accepted for publication in PRD

In this paper, we would like to point out that in the scenario that the right-handed neutrinos suddenly gain some masses much larger than the temperature of the Universe at that time so that the washout effects for the lepton asymmetry generated from their decays can be neglected safely, the purely flavored leptogenesis scenario (in which the total CP asymmetries for the decays of the right-handed neutrinos are vanishing and the successful leptogenesis is realized by virtue of the flavor non-universality of the washout effects) cannot work in the usual way any more. For this problem, we put forward that the flavor non-universality of the conversion efficiencies from the flavored lepton asymmetries to the baryon asymmetry via the sphaleron processes may play a crucial role. And we will study if the requisite baryon asymmetry can be successfully reproduced from such a mechanism in the scenarios that the right-handed neutrino masses are hierarchical and nearly degenerate, respectively. A detailed study shows that this mechanism can be viable in both these two scenarios., Comment: 16 pages, 4 figures, version accepted for publication in JHEP

In this paper we have studied the realizations of the popular TM1 neutrino mixing and neutrino $\mu$-$\tau$ reflection symmetry (which are well motivated from the neutrino oscillation data and lead to interesting phenomenological consequences) in the most minimal seesaw model with a pseudo-Dirac pair of right-handed neutrinos, and their consequences for leptogenesis. In order to realize the low-scale resonant leptogenesis scenario, we have considered two possible ways of generating the tiny mass splitting between the two right-handed neutrinos: one way is to modify their Majorana mass matrix to a form as shown in Eq. (25); the other way is to consider the renormalization-group corrections for their masses. For the $\mu$-$\tau$ reflection symmetry, in order for leptogenesis to work, we have further considered the flavor-dependent conversion efficiencies from the lepton asymmetry to the baryon asymmetry during the sphaleron processes, and its breaking via the renormalization-group corrections., Comment: 24 pages, 10 figures, version accepted for publication in PRD

Motivated by recent experimental data on $\Sigma^+\to p\gamma$ at BESIII, we investigate a class of hyperon weak radiative decays. To estimate these processes, in our research, we employ a new type of light-front quark model with a three-quark picture for octet baryons. In the three-quark picture, with the use of $SU(3)_f$ and spin symmetries, we present a general form of the light front wave function for each octet baryon. By including contributions from the penguin diagram and W exchange diagram, we perform a complete calculation on the branching ratios ($Br$) and the asymmetry parameter ($\alpha$) for hyperon weak radiative decay processes. Our results are helpful for discovering additional hyperon weak radiative decay processes in experimental facilities, and our research will promote the theoretical study of baryons., Comment: 15 pages, 2 figures, 5 tables

In this work, we perform a QCD sum rules analysis on the $\Xi_{Q}-\Xi_{Q}^{\prime}$ mixing. Contributions from up to dimension-6 four-quark operators are considered. However, it turns out that, only dimension-4 and dimension-5 operators contribute, which reveals the non-perturbative nature of mixing. Especially we notice that only the diagrams with the two light quarks participating in gluon exchange contribute to the mixing. Our results indicate that the mixing angle $\theta_{c}=(1.2\sim2.8)^{\circ}$ for the $Q=c$ case and $\theta_{b}=(0.28\sim0.34)^{\circ}$ for the $Q=b$ case. Our prediction of $\theta_{c}$ is consistent with the most recent Lattice QCD result within error. Such a small mixing angle seems unlikely to resolve the tension between the recent experimental measurement from Belle and Lattice QCD calculation for the semileptonic decay $\Xi_{c}^{0}\to\Xi^{-} e^{+}\nu_{e}$., Comment: 13 pages, 4 figures; version accepted by EPJC

In this work, a three-quark picture is constructed using a bottom-up approach for baryons in light-front quark model. The shape parameters, which characterize the momentum distribution inside a baryon, are determined with the help of the pole residue of the baryon. The relation between the three-quark picture and the diquark picture is clarified. When building the model, we find that Lorentz boost plays a crucial role, and the bottom-up modeling approach can be generalized to multiquark states. Based on this, a unified theoretical framework for describing multiquark states may be established. As a by-product of model construction, we can easily obtain a newly improved definition of baryon interpolating current. The hadron interpolating currents are the starting point of Lattice QCD and QCD sum rules, and therefore are of great importance., Comment: 13 pages; version accepted by PRD

We calculate the W-exchange contribution to the $\Xi_{cc}^{++}\to\Xi_{c}^{+(\prime)}\pi^{+}$ decay using light-cone sum rules. The two-particle light-cone distribution amplitudes of the pion are used as non-perturbative input for the sum rules calculation, and the perturbative kernel is calculated at the leading order. We obtain the corresponding decay branching fractions by combining our W-exchange amplitudes with the factorizable amplitudes given by various theoretical methods from the literature. It is shown that with the factorizable amplitudes from heavy quark effective theory, we obtain the branching fraction ratio ${\cal B}(\Xi_{cc}^{++}\to\Xi_{c}^{+\prime}\pi^{+})/{\cal B}(\Xi_{cc}^{++}\to\Xi_{c}^{+}\pi^{+})= 1.42\pm 0.78$, which is consistent with the experimental value of $1.41\pm 0.17\pm 0.1$., Comment: 18 pages, 4 figures, 4 tables

In a paper by Asaka, Ishida and Tanaka \cite{hiding}, they proposed a novel possibility (which will be referred to as the AIT ansatz) that, in spite of the Majorana nature of neutrinos, the neutrinoless double beta ($0\nu \beta\beta$) decay can be hidden. In the original AIT model, the AIT ansatz is realized in the minimal seesaw model with two right-handed neutrinos which have a hierarchical mass structure: the lighter and heavier right-handed neutrinos are respectively much lighter and heavier than the typical Fermi-momentum scale of nuclei. However, the original AIT model does not accommodate a successful leptogenesis. For this problem, in this paper we study a split seesaw model with one lighter right-handed neutrino but two heavier right-handed neutrinos which can realize the AIT ansatz and accommodate a successful leptogenesis simultaneously. We first give the condition on the neutrino Yukawa couplings for realizing the AIT ansatz, discuss its realization by employing an Abelian flavor symmetry, and study its implications for the mixing of the lighter right-handed neutrino with three left-handed neutrinos. We then successively study the implications for leptogenesis of the interesting scenarios where $M^{}_{\rm D}$ is a triangular matrix (which has maximally-restricted texture zeros, in line with the simplicity principle) or respects the $\mu$-$\tau$ reflection symmetry (which is well motivated by the experimental results), on top of the AIT ansatz., Comment: 20 pages, 9 figures, version accepted for publication in EPJC

In this work, we investigate the weak decays of ground-state triply heavy baryons. We first obtain the form factors using the light-front quark model in the three-quark picture, and then apply them to arrive at some phenomenological predictions, including the decay widths of semileptonic decays and nonleptonic decays. Our results are expected to be helpful for the experimental search for triply heavy baryons., Comment: 26 pages, no figures; version 2: diquark to three-quark, more processes are considered, overlap factors are corrected

In this paper, we make an attempt to combine the neutrino trimaximal (TM1 and TM2) mixings and $\mu$-$\tau$ reflection symmetry in the type-I seesaw model. Such a scenario is highly restrictive and predictive: in addition to three right-handed neutrino masses, there are only five real parameters; all the lepton flavor mixing parameters except for $\theta^{}_{13}$ will be predicted. The relations between the model parameters and the measurable neutrino parameters will be derived. The implications of this scenario for leptogenesis will be explored in detail. A further reduction of this scenario to the more restrictive and predictive minimal seesaw model with only two right-handed neutrinos will also be considered. In addition, we will also discuss a possible approach to get the desired mass matrices and study the compatibility of the trimaximal $\mu$-$\tau$ reflection symmetry with texture zeros., Comment: 25 pages, 10 figures, minor revisions, version accepted for publication in EPJC

In this work, we study the resonance contributions to the decay $B^-\to K^+K^-\pi^-$, which is dominated by the scalar $f_0(980), K_0^*(1430)$, vector $\rho(1450), \phi(1020), K^*(892)$ and tensor $f_2(1270)$ resonances. The three-body decay is reduced to various quasi two-body decays, where the $B$ meson firstly decays into a resonance and a pion or a kaon, subsequently the resonance decays into the other two final-state mesons. The quasi two-body decays are calculated within the light-cone sum rule approach utilizing the leading twist $B$ meson light-cone distribution amplitudes. Finally, the decay branching fraction contribution from each resonance are calculated. Some of them are compatible with experiment or previous theoretical works. Including the effects of non-resonant and final-state interactions, we also evaluate the total branching fraction., Comment: 29 pages, 1 figure

A comprehensive study of $b\to c$ weak decays of doubly heavy baryons is presented in this paper. The transition form factors as well as the pole residues of the initial and final states are respectively obtained by investigating the three-point and two-point correlation functions in QCD sum rules. Contributions from up to dimension-6 operators are respectively considered for the two-point and three-point correlation functions. The obtained form factors are then applied to a phenomenological analysis of semi-leptonic decays., Comment: 13 pages, 5 figures

The anomalous dimensions for the interpolating currents of baryons are indispensable inputs in a serious QCD analysis of baryon. However, the results in the literature are vague. In view of this, in this work, we investigate the one-loop anomalous dimensions for some interpolating currents such as those of $\Lambda_{Q}$ and proton. Under the requirement of precise testing the Standard Model, this study is essential and significant for the QCD analysis in the future., Comment: 7 pages, 1 figure

In the seesaw framework, in the basis of $M^{}_{\rm R}$ being diagonal, we explore the simplified textures of $M^{}_{\rm D}$ that can naturally yield the trimaximal neutrino mixings and their consequences for the neutrino parameters and leptogenesis. We first formulate the generic textures of $M^{}_{\rm D}$ that can naturally yield the trimaximal mixings and then examine if their parameters can be further reduced. Our analysis is restricted to the simple but instructive scenario that there is only one phase parameter $\phi$ responsible for both the CP violating effects at low energies and leptogenesis. Our attention is paid to the textures of $M^{}_{\rm D}$ that possess some vanishing or equal elements. On the basis of these results, we further examine if $\phi$ can also take a particular value. The consequences of the phenomenologically-viable simplified textures for the neutrino parameters and leptogenesis are studied. A concrete flavor-symmetry model that can realize one representation of them is given., Comment: 27 pages, 5 figures, 10 tables, version accepted for publication in PRD

There exists a significant deviation between the most recent Lattice QCD simulation and experimental measurement by Belle for $\Xi_{c}^{0}\to\Xi^{-}\ell^{+}\nu_{\ell}$. In this work, we investigate the $\Xi_{c}\to\Xi$ form factors in QCD sum rules. To this end, the two-point correlation functions of $\Xi_{c}$ and $\Xi$, and the three-point correlation functions of $\Xi_{c}\to\Xi$ are calculated. At the QCD level, contributions from up to dimension-6 four-quark operators are considered, and the leading order results of the Wilson coefficients are obtained. For the form factors, relatively stable Borel windows can be found. Our form factors are comparable with those of Lattice QCD, except for $f_{\perp}$. The obtained form factors are then used to predict the branching ratios of $\Xi_{c}\to\Xi \ell^{+}\nu_{\ell}$, and our predictions are consistent with the most recent data of ALICE and Belle, and those of Lattice QCD within error. Given that the branching ratios only contain limited information, we suggest the experimentalists directly measure the form factors of $\Xi_{c}\to\Xi$., Comment: 18 pages, 7 figures; version accepted by PRD

Following the Occam's razor principle, we explore the particular textures (featuring texture zeros and equalities) of the Dirac neutrino mass matrix in the minimal seesaw model (where only two right-handed neutrinos $N^{}_1$ and $N^{}_2$ are responsible for the generation of the light neutrino masses), in light of current neutrino experimental results and leptogenesis. The study will be performed for two particular patterns of the Majorana mass matrix $M^{}_{\rm R}$ for $N^{}_1$ and $N^{}_2$: (A) $M^{}_{\rm R}$ being diagonal $ \left( \begin{array}{cc} M^{}_1 & 0 \cr 0 & M^{}_2 \cr \end{array} \right)$; (B) $M^{}_{\rm R}$ being of the form $\left( \begin{array}{cc} 0 & M \cr M & 0 \cr \end{array} \right)$., Comment: typos corrected and some references added

Heavy quark expansion can nicely explain the lifetime of $\Lambda_{b}$. However, there still exist sizable uncertainties from the four-quark operator matrix elements of $\Lambda_{b}$ in $1/m_{b}^{3}$ corrections, which describe the spectator effects. In this work, these four-quark operator matrix elements are investigated using full QCD sum rules for the first time. At the QCD level, contributions from up to dimension-6 four-quark operators are considered. Our method of calculating high-dimensional operator matrix elements is promising to be used to resolve the $\Omega_{c}$ lifetime puzzle., Comment: 13 pages, 4 figures; version accepted by EPJC

We perform a SU(3) analysis for both semi-leptonic and non-leptonic heavy meson weak decays into a pseudoscalar meson and a fully-light tetraquark in 10 or 27 representation. A reduction of the SU(3) representation tensor for the fully-light tetraquarks is produced and all the flavor components for each representation tensor are listed. The decay channels we analysis include $B/D \to U/T~P~l\nu$, $B/D \to U/T~P $ and $B_c \to U/T~P/D$, with $U/T$ represents a fully-light tetraquark in 10 or 27 representation and $P$ is a pseudoscalar meson. Finally, among these results we list all the golden decay channels which are expected to have more possibilities to be observed in experiments., Comment: 32 pages, 5 figures

In this work, the full leading order results of the form factors for $\Xi_{b}\to\Xi_{c}$ and $\Lambda_{b}\to\Lambda_{c}$ are obtained in QCD sum rules. Contributions from up to dim-5 have been considered. For completeness, we also study the two-point correlation function to obtain the pole residues of $\Xi_{Q}$ and $\Lambda_{Q}$, and higher accuracy is achieved. For the three-point correlation function, since stable Borel regions can not be found, about $20\%$ uncertainties are introduced for the form factors of $\Xi_{b}\to\Xi_{c}$ and $\Lambda_{b}\to\Lambda_{c}$. Our results for the form factors are consistent with those of the Lattice QCD within errors., Comment: 17 pages, 5 figures

Given its briefness and predictability, the minimal seesaw -- a simplified version of the canonical seesaw mechanism with only two right-handed neutrino fields -- has been studied in depth and from many perspectives, and now it is being pushed close to a position of directly facing experimental tests. This article is intended to provide an up-to-date review of various phenomenological aspects of the minimal seesaw and its associated leptogenesis mechanism in neutrino physics and cosmology. Our focus is on possible flavor structures of such benchmark seesaw and leptogenesis scenarios and confronting their predictions with current neutrino oscillation data and cosmological observations. In this connection particular attention will be paid to the topics of lepton number violation, lepton flavor violation, discrete flavor symmetries, CP violation and antimatter of the Universe., Comment: 111 pages, 23 figures, 9 tables, final version published in Reports on Progress in Physics as a Review Article

In this work, we evaluate the accuracy of the leading order results in Shifman-Vainshtein-Zakharov (SVZ) sum rules and the leading power results in the heavy quark limit for the mass of $\Lambda_{Q}$. Up to dim-5 condensate contributions are considered. By comparing with the experimental results, we find that the leading order results in SVZ sum rules can reach about 5\% accuracy both for $\Lambda_{b}$ and $\Lambda_{c}$, and it seems that better results can be obtained from the sum rules of the heavy quark limit both for $\Lambda_{b}$ and $\Lambda_{c}$. We re-check that the SVZ sum rules in the heavy quark limit coincide with the HQET sum rules. As a byproduct, we also have an exploratory discussion on the $ud$ diquark in $\Lambda_{Q}$., Comment: 10 pages, 3 figures

In this paper, we consider the imbedding of the popular and well-motivated trimaximal mixing and $\mu$-$\tau$ reflection symmetry (which can help us shape the forms of the neutrino mass matrix) in the minimal seesaw model (which contains much fewer parameters than the general seesaw model) with two TeV-scale right-handed neutrinos (for realizing a low-scale seesaw) of nearly degenerate masses (for realizing a resonant leptogenesis). However, either for the trimaximal mixing scenario (which is realized through the Form Dominance approach here) or for the $\mu$-$\tau$ reflection symmetry scenario, leptogenesis cannot proceed. To address this issue, we consider the possibility that the special forms of the neutrino mass matrix for the trimaximal mixing and $\mu$-$\tau$ reflection symmetry are slightly broken by the renormalization group evolution effect, thus allowing leptogenesis to proceed. It is found that in the normal case of the neutrino mass ordering, the baryon asymmetry thus generated can reproduce the observed value. For completeness, we have also extended our analysis to the scenario that two right-handed neutrinos are not nearly degenerate any more. Unfortunately, in this scenario the final baryon asymmetry is smaller than the observed value by several orders of magnitude., Comment: 25 pages, 4 figures, version to appear in JHEP

We construct a leading-order effective field theory for both scalar and axial-vector heavy diquarks, and consider its power expansion in the heavy diquark limit. By assuming the transition from QCD to diquark effective theory, we derive the most general form for the effective diquark transition currents based on the heavy diquark symmetry. The short-distance coefficients between QCD and heavy diquark effective field theory are also obtained by a tree level matching. With the effective currents in the heavy diquark limit, we perform a reduction of the form factors for semi-leptonic decays of doubly heavy baryons, and find that only one nonperturbative function is remaining. It is shown that this soft function can be related to the Isgur-Wise function in heavy meson transitions. As a phenomenological application, we take a single pole structure for the reduced form factor, and use it to calculate the semi-leptonic decay widths of doubly heavy baryons. The obtained results are consistent with others given in the literature, and can be tested in the future., Comment: 24 pages, 3 figures, 1 table

A sizable right-handed photon polarization in $b\to s\gamma$ is a clear signal for new physics. In this work we point out that the photon helicity in $b\to s\gamma$ can be unambiguously extracted by combining the measurements in $B\to K_1\gamma$ and the Cabibbo-favored $D\to K_1 e^+\nu$ decay. We propose a ratio of up-down asymmetries in $D\to K_1 e^+\nu$ to quantify the hadronic effects. { A method for measuring in experiment the involved partial decay widths in the ratio is discussed, and experimental facilities like BESIII, Belle-II and LHCb are likely to measure this ratio. We also give the angular distribution that is useful to extract the photon polarization in the presence of different kaon resonances. }, Comment: 5 pages, 1 figure; v2: title changed, a method for experimental measurements of the involved partial decay widths is given, accepted for publication in Physical Review Letters

In this paper, we emphasize why it is important for future neutrinoless double-beta ($0\nu\beta\beta$) decay experiments to reach the sensitivity to the effective neutrino mass $|m^{}_{\beta\beta}| \approx 1~{\rm meV}$. Assuming such a sensitivity and the precisions on neutrino oscillation parameters after the JUNO experiment, we fully explore the constrained regions of the lightest neutrino mass $m^{}_1$ and two Majorana-type CP-violating phases $\{\rho, \sigma\}$. The implications for the neutrino mass spectrum, the effective neutrino mass $m^{}_\beta$ in beta decays and the sum of three neutrino masses $\Sigma \equiv m^{}_1 + m^{}_2 + m^{}_3$ relevant for cosmological observations are also discussed., Comment: 16 pages, 6 figures

We analyze the weak decay of doubly-heavy baryon decays into anti-triplets $\Lambda_Q$ with light-cone sum rules. To calculate the decay form factors, both bottom and charmed anti-triplets $\Lambda_b$ and $\Lambda_c$ are described by the same set of leading twist light-cone distribution functions. With the obtained form factors, we perform a phenomenology study on the corresponding semi-leptonic decays. The decay widths are calculated and the branching ratios given in this work are expected to be tested by future experimental data, which will help us to understand the underlying dynamics in doubly-heavy baryon decays., Comment: 19 pages, 3 figures, 7 tables

We calculate the weak decay form factors of doubly-heavy baryons using three-point QCD sum rules. The Cutkosky rules are used to derive the double dispersion relations. We include perturbative contributions and condensation contributions up to dimension five, and point out that the perturbative contributions and condensates with lowest dimensions dominate. An estimate of part of gluon-gluon condensates show that it plays a less important role. With these form factors at hand, we present a phenomenological study of semileptonic decays. The future experimental facilities can test these predictions, and deepen our understanding of the dynamics in decays of doubly-heavy baryons., Comment: 30 pages, 8 figures. Version accepted in The European Physical Journal C

FCNC processes offer important tools to test the Standard Model (SM), and to search for possible new physics. In this work, we investigate the $s\to d\nu\bar{\nu}$ rare hyperon decays in SM and beyond. We find that in SM the branching ratios for these rare hyperon decays range from $10^{-14}$ to $10^{-11}$. When all the errors in the form factors are included, we find that the final branching fractions for most decay modes have an uncertainty of about $5\%$ to $10\%$. After taking into account the contribution from new physics, the generalized SUSY extension of SM and the minimal 331 model, the decay widths for these channels can be enhanced by a factor of $2 \sim 7$., Comment: 9 pages, 5 tables

In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead to maximal atmospherical mixing angle ($\theta^{}_{23} = \pi/4$) and Dirac CP phase ($\delta = - \pi/2$) in two phenomenologically appealing scenarios: (1) one neutrino mass matrix element being vanishing (2) one neutrino mass being vanishing. For the obtained textures, some neutrino mass sum rules which relate the neutrino masses and mixing parameters will emerge. With the help of these sum rules, the unknown absolute neutrino mass scale and Majorana CP phases can be determined. Some discussions about the possible textures of neutrino mass matrix that can lead to $\theta^{}_{23} = \pi/4$, $\delta = - \pi/2$ and maximal Majorana CP phases ($\rho, \sigma = \pi/4$ or $3\pi/4$) as well as the model realization and breakings of the obtained textures are also given., Comment: 25 pages, no figures, major revisions, references added, version accepted for publication in PRD

In this paper, we derive in a novel approach the possible textures of neutrino mass matrix that can lead us to maximal atmospheric mixing angle and Dirac CP phase which are consistent with the current neutrino oscillation data. A total of eleven textures are thus found. Interestingly, the specific texture given by the $\mu$-$\tau$ reflection symmetry can be reproduced from one of the obtained textures. For these textures, some neutrino mass sum rules which relate the neutrino masses and Majorana CP phases will emerge., Comment: 21 pages, 10 figures, version to appear in JHEP, a new paragraph discussing the physical meaning of the textures obtained is added at the end of section 3

The discovery of doubly heavy baryon provides us with a new platform for precisely testing Standard Model and searching for new physics. As a continuation of our previous works, we investigate the FCNC processes of doubly heavy baryons. Light-front approach is adopted to extract the form factors, in which the two spectator quarks are viewed as a diquark. Results for form factors are then used to predict some phenomenological observables, such as the decay width and the forward-backward asymmetry. We find that most of the branching ratios for $b\to s$ processes are $10^{-8}\sim10^{-7}$ and those for $b\to d$ processes are $10^{-9}\sim10^{-8}$. The flavor SU(3) symmetry and symmetry breaking effects are explored. Parametric uncertainties are also investigated., Comment: 22 pages, 4 figures

As a continuation of our previous works, we investigate the weak decays of doubly heavy baryons into a spin-$3/2$ singly or doubly heavy baryon. Light-front approach is adopted to handle the dynamics in the transitions, in which the two spectator quarks are approximated as a diquark. Results for form factors are then used to calculate decay widths of semi-leptonic and nonleptonic processes. The flavor SU(3) symmetry and symmetry breaking effects in semi-leptonic decays modes are explored, and we point out that in charm sector, there are sizable symmetry breaking effects. For nonleptonic decay modes, we study only the factorizable channels induced by the external W-emission. We find that branching fractions for most 1/2 to 3/2 transitions are approximately one order of magnitude smaller than the corresponding ones for the 1/2 to 1/2 transitions. Parametric uncertainties are also investigated in detail. This work, together with our previous works, are beneficial to the experimental studies of doubly heavy baryons at LHC and other experiments., Comment: 23 pages, 2 figures

The $\mu$-$\tau$ reflection symmetry serves as a unique basis for understanding the observed neutrino mixing as it can lead us to the interesting results $\theta^{}_{23} = \pi/4$ and $\delta = -\pi/2$ which stand close to the current experimental results. But a precise measurement for $\theta^{}_{23}$ and $\delta$ will probably force us to modify the neutrino mixing $U^{(0)}$ from such a symmetry. Here we perform a study for modifications to $U^{(0)}$ in the forms of $U^{(1)\dagger} U^{(0)}$ and $U^{(0)} U^{(1)}$ where $U^{(1)}= R^{(1)}_{ij}$ (for $ij = 12, 23$ and 13) with $R^{(1)}_{ij}$ denoting a real orthogonal rotation on the $ij$ plane., Comment: 16 pages, 6 figures, minor revision, references added, to appear in Nuclear Physics B

In this work, we perform a analysis of semi-leptonic and nonleptonic weak decays of heavy baryons: $\Lambda_{b},\Xi_{b},\Omega_{b}$ and $\Lambda_{c},\Xi_{c},\Omega_{c}$. For nonleptonic decay modes, we study only the factorizable channels induced by the external W-emission. The two spectator quarks in baryonic transitions are treated as a diquark and form factors are calculated in the light-front approach. Using the results for form factors, we also calculate some corresponding semi-leptonic and nonleptonic decay widths. We find that our results are comparable with the available experimental data and other theoretical predictions. Decay branching fractions for many channels are found to reach the level $10^{-3}\sim10^{-2}$, which are promising to be discovered in the future measurements at BESIII, LHCb and BelleII. The SU(3) symmetry in semi-leptonic decays is examined and sources of symmetry breaking are discussed., Comment: 23 pages, 2 figures, to be published in Chinese Physics C

In order to localize $U(1)$ gauge vector field on Randall-Sundrum-like braneworld model with infinite extra dimension, we propose a new kind of non-minimal coupling between the $U(1)$ gauge field and the gravity. We propose three kinds of coupling methods and they all support the localization of zero mode. In addition, one of them can support the localization of massive modes. Moreover, the massive tachyonic modes can be excluded. And our method can be used not only in the thin braneword models but also in the thick ones., Comment: Added acknowledgments to the refree. Appeared on JHEP

Inspired by the recent observation of the $\Xi_{cc}^{++}$ by LHCb collaboration, we explore the "decay constants" of doubly heavy baryons in the framework of QCD sum rules. With the $\Xi_{cc}, \Xi_{bc}, \Xi_{bb}$, and $\Omega_{cc}, \Omega_{bc}, \Omega_{bb}$ baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contribution from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with $J^P=1/2^+$ and from negative parity baryons with $J^P=1/2^-$. We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons., Comment: 15 pages, 4 figures, 4 tables, to be published in Chinese Physics C

For some theoretical and experimental considerations, the relatively light Majorana neutrinos at the GeV scale have been attracting some interest. In this article we consider a scenario with only one Majorana neutrino $N$, negligible mixing with the active neutrinos $\nu_{L}$, where the Majorana neutrino interactions could be described in a model independent approach based on an effective theory. Under such a framework, we particularly study the feasibility of observing the $N$ with mass in the range 0$-$30 GeV via the process $e^+ e^- \to \nu N \to\gamma + \slashed E$ in the future Belle-II and ILC experiments. The results show that it is unpromising for Belle-II to observe the signal, while ILC may easily make a discovery for the Majorana neutrino., Comment: 14 pages, 7 figures, 2 tables

In this paper, we attempt to implement the neutrino $\mu$-$\tau$ reflection symmetry (which predicts $\theta^{}_{23} = \pi/4$ and $\delta = \pm \pi/2$ as well as trivial Majorana phases) in the minimal seesaw (which enables us to fix the neutrino masses). For some direct (the preliminary experimental hints towards $\theta^{}_{23} \neq \pi/4$ and $\delta \neq - \pi/2$) and indirect (inclusion of the renormalization group equation effect and implementation of the leptogenesis mechanism) reasons, we particularly study the breakings of this symmetry and their phenomenological consequences., Comment: 20 pages, 7 figures, accepted for publication in JHEP

Very recently, the LHCb collaboration has observed in the final state $\Lambda_c^+ K^-\pi^+\pi^+$ a resonant structure that is identified as the doubly-charmed baryon $\Xi_{cc}^{++}$. Inspired by this observation, we investigate the weak decays of doubly heavy baryons $\Xi_{cc}^{++}$, $\Xi_{cc}^{+}$, $\Omega_{cc}^{+}$, $\Xi_{bc}^{(\prime)+}$, $\Xi_{bc}^{(\prime)0}$, $\Omega_{bc}^{(\prime)0}$, $\Xi_{bb}^{0}$, $\Xi_{bb}^{-}$ and $\Omega_{bb}^{-}$ and focus on the decays into spin $1/2$ baryons in this paper. At the quark level these decay processes are induced by the $c\to d/s$ or $b\to u/c$ transitions, and the two spectator quarks can be viewed as a scalar or axial vector diquark. We first derive the hadronic form factors for these transitions in the light-front approach and then apply them to predict the partial widths for the semi-leptonic and non-leptonic decays of doubly heavy baryons. We find that a number of decay channels are sizable and can be examined in future measurements at experimental facilities like LHC, Belle II and CEPC., Comment: 40 pages, 4 figures, to appear in EPJC

The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$, which would be helpful for experimental searches for these particles. The branching fractions are studied under the factorization hypothesis for the short-distance contributions and considering the rescattering effect for the long-distance contributions which are significantly enhanced. Comparing all the decay modes, we recommend the processes of $\Xi_{cc}^{++}\to \Lambda_c^+K^-\pi^+\pi^+$ and $\Xi_c^+\pi^+$ as the first priority for experiments to search for the doubly heavy baryons., Comment: 16 pages, 3 figure, 5 tables. Version to be published in CPC

The neutrino $\mu$-$\tau$ reflection symmetry has been attracting a lot of attention as it predicts the interesting results $\theta^{}_{23} = \pi/4$ and $\delta = \pm \pi/2$. But it is reasonable to consider breakings of such a symmetry either from the theoretical considerations or on the basis of experimental results. We thus perform a systematic study for the possible symmetry-breaking patterns and their implications for the mixing parameters. The general treatment is applied to some specific symmetry breaking arising from the renormalization group effects for illustration., Comment: 18 pages, 6 figures, 5 tables, minor revision, accepted for publication in JHEP

If massive neutrinos are the Majorana particles and have a normal mass ordering, the effective mass term $\langle m\rangle^{}_{ee}$ of a neutrinoless double-beta ($0\nu 2\beta$) decay may suffer significant cancellations among its three components and thus sink into a decline, resulting in a "well" in the three-dimensional graph of $|\langle m\rangle^{}_{ee}|$ against the smallest neutrino mass $m^{}_1$ and the relevant Majorana phase $\rho$. We present a new and complete analytical understanding of the fine issues inside such a well, and discover a novel threshold of $|\langle m\rangle^{}_{ee}|$ in terms of the neutrino masses and flavor mixing angles: $|\langle m\rangle^{}_{ee}|^{}_* = m^{}_3 \sin^2\theta^{}_{13}$ in connection with $\tan\theta^{}_{12} = \sqrt{m^{}_1/m^{}_2}$ and $\rho =\pi$. This threshold point, which links the {\it local} minimum and maximum of $|\langle m\rangle^{}_{ee}|$, can be used to signify observability or sensitivity of the future $0\nu 2\beta$-decay experiments. Given current neutrino oscillation data, the possibility of $|\langle m\rangle^{}_{ee}| < |\langle m\rangle^{}_{ee}|^{}_*$ is found to be very small., Comment: 9 pages, 3 figures, version to appear in Eur. Phys. J. C

We suggest to study the $B_{s}$ and its excitations $B_{sJ}$ in the $B_c$ decays. We calculate the $B_c\to B_{sJ}$ and $B_c\to B_{J}$ form factors within the covariant light-front quark model, where the $B_{sJ}$ and $B_{J}$ denote an s-wave or p-wave $\bar bs$ and $\bar bd$ meson, respectively. The form factors at $q^2=0$ are directly computed while their $q^2$-distributions are obtained by the extrapolation. The derived form factors are then used to study semileptonic $B_c\to (B_{sJ},B_{J})\bar\ell\nu$ decays, and nonleptonic $B_c\to B_{sJ}\pi$. Branching fractions and polarizations are predicted in the standard model. We find that the branching fractions are sizable and might be accessible at the LHC experiment and future high-energy $e^+e^-$ colliders with a high luminosity at the $Z$-pole. The future experimental measurements are helpful to study the nonperturbative QCD dynamics in the presence of a heavy spectator and also of great value for the spectroscopy study., Comment: 16 pages, 2 figures

The latest LHC data suggest an intriguing excess at $m_{\gamma\gamma} = 750$ GeV which apparently requires an explanation from the beyond standard model physics. In this note we explore the possibility for this signal to arise from a top-pion in the Top Triangle Moose model which can be viewed as a dimensional-deconstruction version of the top-color assisted technicolor model. We demonstrate that the observed excess can be accommodated by and has important implications for this interesting model., Comment: 12 pages, 3 figures, Int. J. Mod. Phys. A (2016)