arXiv subjects

Yu-Ji Shi

Publications and source records attributed to Yu-Ji Shi.

At least 37 records · Page 2Linked to original sources

arXiv2022

Weak radiative decay $Λ_{c}^{+}\toΣ^{+}γ$ using light-cone sum rules

We calculate the decay width of the $Λ_{c}^{+}\toΣ^{+}γ$ using light-cone sum rules. For the initial quark radiation an effective Hamiltonian is constructed, where the internal quark line shrinks to a point. The final quark radiation is studied within the full theory. The leading twist light-cone distribution amplitudes of the $Σ^+$ serve as the non-perturbative input for the sum rules calculation, and the perturbative kernel is calculated at leading order. The branching fraction we obtain is ${\cal B}(Λ_{c}^{+}\toΣ^{+}γ)=1.03\pm 0.36 \times 10^{-4}$, which is below the recent upper limit $<2.6 \times 10^{-4}$ given by the Belle collaboration.

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arXiv2022

Light-Cone Sum Rules Analysis of $Ξ_{QQ^{\prime}q}\toΣ_{Q^{\prime}}^{*}$ Weak Decays

In this work, we investigate the semi-leptonic weak decays of spin-1/2 doubly-heavy baryons $Ξ_{QQ^{\prime}}$ into spin-3/2 singly-heavy baryons $Σ_{Q^{\prime}}^*$ within light-cone sum rules. Using the parallel components of the light-cone distribution amplitudes of $Σ_{Q^{\prime}}^*$, the transition form factors for these decays are calculated both analytically and numerically. The numerical results for these semi-leptonic weak decays widths and branching ratios are also predicted, which are compared with the same predictions by other theoretical approaches in the literatures. These phenomenology predictions can be tested by the experiments in the future.

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arXiv2022

W-exchange contribution to the decays $Ξ_{cc}^{++}\toΞ_{c}^{+(\prime)}π^{+}$ using light-cone sum rules

We calculate the W-exchange contribution to the $Ξ_{cc}^{++}\toΞ_{c}^{+(\prime)}π^{+}$ 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 ${\cal B}(Ξ_{cc}^{++}\toΞ_{c}^{+\prime}π^{+})/{\cal B}(Ξ_{cc}^{++}\toΞ_{c}^{+}π^{+})= 1.42\pm 0.78$, which is consistent with the experimental value of $1.41\pm 0.17\pm 0.1$.

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arXiv2022

Inclusive approach to hunt for the beauty-charmed baryons $Ξ_{bc}$

With a distinctive internal structure from all established hadrons, the beauty-charmed baryons $Ξ_{bc}$ can provide us with new points of view to decipher the strong interaction. In this work, we point out that the inclusive $Ξ_{bc} \to Ξ_{cc}^{++}+X$ decay is a golden channel for the experimental discovery of $Ξ_{bc}$ at the LHC. A unique feature of this process is that the $Ξ_{cc}^{++}$ is displaced, which greatly reduces the combinatorial background. A feasibility analysis is performed on the $Ξ_{bc}^+$ search, which is expected to have a longer lifetime than $Ξ_{bc}^0$ and thus a better displacement resolution. The $Ξ_{bc}^+ \to Ξ_{cc}^{++}+X$ branching ratio is calculated within the heavy diquark effective theory. Combining the $Ξ_{bc}$ production rate and the $Ξ_{cc}^{++}$ detection efficiency, we anticipate that hundreds of signal events will be collected during LHCb Run 3.

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arXiv2021

Resonance contributions in $B^-\to K^+K^-π^-$ within the light-come sum rule approach

In this work, we study the resonance contributions to the decay $B^-\to K^+K^-π^-$, which is dominated by the scalar $f_0(980), K_0^*(1430)$, vector $ρ(1450), ϕ(1020), K^*(892)$ 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.

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arXiv2021

Two-Meson Form Factors in Unitarized Chiral Perturbation Theory

We present a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators. The theoretical framework is based on a combination of unitarized chiral perturbation theory and dispersion relations. The low-energy constants in chiral perturbation theory are fixed by a global fit to the available data of the two-meson scattering phase shifts. Each form factor derived from unitarized chiral perturbation theory is improved by iteratively applying a dispersion relation. This study updates the existing results in the literature and explores those that have not been systematically studied previously, in particular the two-meson tensor form factors within unitarized chiral perturbation theory. We also discuss the applications of these form factors as mandatory inputs for low-energy phenomena, such as the semi-leptonic decays $B_s\to π^+π^-\ell^+\ell^-$ and the $τ$ lepton decay $τ\rightarrowπ^{-}π^{0}ν_τ$, in searches for physics beyond the Standard Model.

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arXiv2021

Chiral dynamics and S-wave contributions in $\bar B^0/D^0 \to π^{\pm}η l^{\mp} ν$ decays

In this work, we analyze the semi-leptonic decays $\bar B^0/D^0 \to (a_0(980)^{\pm}\toπ^{\pm}η) l^{\mp} ν$ within light-cone sum rules. The two and three-body light-cone distribution amplitudes (LCDAs) of the $B$ meson and the only available two-body LCDA of the $D$ meson are used. To include the finite-width effect of the $a_0(980)$, we use a scalar form factor to describe the final-state interaction between the $πη$ mesons, which was previously calculated within unitarized Chiral Perturbation Theory. The result for the decay branching fraction of the $D^0$ decay is in good agreement with that measured by the BESIII Collaboration, while the branching fraction of the $\bar B^0$ decay can be tested in future experiments.

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arXiv2020

SU(3) analysis of fully-light tetraquarks in heavy meson weak decays

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 $B/D \to U/T~P~lν$, $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.

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arXiv2020

The semi-leptonic form factors of $Λ_{b}\toΛ_{c}$ and $Ξ_{b}\toΞ_{c}$ in QCD sum rules

In this work, the full leading order results of the form factors for $Ξ_{b}\toΞ_{c}$ and $Λ_{b}\toΛ_{c}$ 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 $Ξ_{Q}$ and $Λ_{Q}$, 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 $Ξ_{b}\toΞ_{c}$ and $Λ_{b}\toΛ_{c}$. Our results for the form factors are consistent with those of the Lattice QCD within errors.

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arXiv2020

QCD Sum Rules Analysis of Weak Decays of Doubly-Heavy Baryons

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.

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arXiv2020

Hadronization of heavy diquark and light quark within NJL-Model

We present a path-integral hadronization for doubly heavy baryons. The two heavy quarks in the baryon are approximated as a scalar or axial-vector diquark described by a heavy diquark effective theory. The gluon dynamics are represented by a NJL-Model interaction for the heavy diquarks and light quarks, which leads to an effective action of the baryon fields after the quark and diquark fields are integrated out. This effective action for doubly heavy baryon includes the electromagnetic and electroweak interactions, as well as the interaction with light mesons. We also verify the Ward-Takahashi identity at the baryon level, obtain the Isgur-Wise function for weak transitions, and calculate the strong coupling constant of the doubly heavy baryon and pion. Numerical studies are also performed.

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arXiv2020

The SVZ sum rules and the heavy quark limit for $Λ_{Q}$

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 $Λ_{Q}$. 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 $Λ_{b}$ and $Λ_{c}$, and it seems that better results can be obtained from the sum rules of the heavy quark limit both for $Λ_{b}$ and $Λ_{c}$. 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 $Λ_{Q}$.

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arXiv2020

Unification of Flavor SU(3) Analyses of Heavy Hadron Weak Decays

Analyses of heavy mesons and baryons hadronic charmless decays using the flavor SU(3) symemtry can be formulated in two different forms. One is to construct the SU(3) irreducible representation amplitude (IRA) by decomposing effective Hamiltonian, and the other is to draw the topological diagrams (TDA). In the flavor SU(3) limit, we study various $B/D\to PP,VP,VV$, $B_c\to DP/DV$ decays, and two-body nonleptonic decays of beauty/charm baryons, and demonstrate that when all terms are included these two ways of analyzing the decay amplitudes are completely equivalent. Furthermore we clarify some confusions in drawing topological diagrams using different ways of describing beauty/charm baryons.

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arXiv2020

Towards a Heavy Diquark Effective Theory for Weak Decays of Doubly Heavy Baryons

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.

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arXiv2020

Light-Cone Sum Rules Analysis of $Ξ_{QQ^{\prime}}\toΣ_{Q^{\prime}}$ Weak Decays

As a continuation of our previous work, we investigate the weak decays of doubly-heavy baryons $Ξ_{QQ^{\prime}}$ into sextet $Σ_{Q^{\prime}}$ with light-cone sum rules. We calculate the form factors for these decays with the parallel light-cone distribution amplitudes of $Σ_{Q^{\prime}}$. Numerical results of these form factors are used to predict the decay widths and branching ratios of the corresponding semi-leptonic processes. Parametric uncertainties and theoretical analyses are also given in detail. We find that the decay widths of $Ξ_{cc}$ and $Ξ_{bc}$ decays are several orders of magnitude larger than those of $Ξ_{bb}$ decays.

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arXiv2019

Light-Cone Sum Rules Analysis of $Ξ_{QQ^{\prime}q}\toΛ_{Q^{\prime}}$ Weak Decays

We analyze the weak decay of doubly-heavy baryon decays into anti-triplets $Λ_Q$ with light-cone sum rules. To calculate the decay form factors, both bottom and charmed anti-triplets $Λ_b$ and $Λ_c$ 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.

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arXiv2017

Weak Decays of Doubly Heavy Baryons: Multi-body Decay Channels

The newly-discovered $Ξ_{cc}^{++}$ decays into the $ Λ_{c}^+ K^-π^+π^+$, but the experimental data has indicated that this decay is not saturated by any two-body intermediate state. In this work, we analyze the multi-body weak decays of doubly heavy baryons $Ξ_{cc}$, $Ω_{cc}$, $Ξ_{bc}$, $Ω_{bc}$, $Ξ_{bb}$ and $Ω_{bb}$, in particular the three-body nonleptonic decays and four-body semileptonic decays. We classify various decay modes according to the quark-level transitions and present an estimate of the typical branching fractions for a few golden decay channels. Decay amplitudes are then parametrized in terms of a few SU(3) irreducible amplitudes. With these amplitudes, we find a number of relations for decay widths, which can be examined in future.

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arXiv2017

Chiral dynamics, S-wave contributions and angular analysis in $D\to ππ\ell\barν$

We present a theoretical analysis of the $D^-\to π^+π^- \ell\barν$ and $\bar D^0\to π^+π^0 \ell\barν$ decays. We construct a general angular distribution which can include arbitrary partial waves of $ππ$. Retaining the S-wave and P-wave contributions we study the branching ratios, forward--backward asymmetries and a few other observables. The P-wave contribution is dominated by $ρ^0$ resonance, and the S-wave contribution is analyzed using the unitarized chiral perturbation theory. The obtained branching fraction for $D\to ρ\ellν$, at the order $10^{-3}$, is consistent with the available experimental data. The S-wave contribution has a branching ratio at the order of $10^{-4}$, and this prediction can be tested by experiments like BESIII and LHCb. Future measurements can also be used to examine the $π$--$π$ scattering phase shift.

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