Search

In this work, we calculate the transition form factors of $$\Lambda _b$$ Λ b decaying into proton and $$N^*(1535)$$ N ∗ ( 1535 ) ($$J^P={1/2}^+$$ J P = 1 / 2 + and $${1/2}^-$$ 1 / 2 - respectively) within the framework of light-cone sum rules with the distribution amplitudes (DAs) of $$\Lambda _b$$ Λ b -baryon. In the hadronic representation of the correlation function, we have isolated both the proton and the $$N^*(1535)$$ N ∗ ( 1535 ) states so that the $$\Lambda _b \rightarrow p, N^*(1535)$$ Λ b → p , N ∗ ( 1535 ) form factors can be evaluated simultaneously. Due to the less known properties of the baryons, we investigate three interpolating currents of the light baryons and five parametrization models for DAs of $$\Lambda _b $$ Λ b . Numerically, our predictions on the $$\Lambda _b \rightarrow p$$ Λ b → p form factors and the branching fractions of $$\Lambda _b\rightarrow p\ell \nu $$ Λ b → p ℓ ν from the Ioffe or the tensor currents are consistent with the Lattice simulation and the results from the light-baryon sum rules, as well as the experimental data of $$Br(\Lambda _b^0\rightarrow p\mu ^-{{\bar{\nu }}})$$ B r ( Λ b 0 → p μ - ν ¯ ) . The predictions on the form factors of $$\Lambda _b \rightarrow N^*(1535)$$ Λ b → N ∗ ( 1535 ) are very sensitive to the choice of the interpolating currents so that the relevant measurement could be helpful to clarify the properties of baryons.

The decay width of the $$D_s^{*}$$ D s ∗ meson is dominated by the electromagnetic mode $$D_s^*\rightarrow D_s \gamma $$ D s ∗ → D s γ , and it is thus the longest-lived charged vector meson. In light of this point, we perform the first QCD LCSRs calculation of $$D_s^{*}\rightarrow \phi $$ D s ∗ → ϕ helicity form factors and discuss the experiment potential of discovering exclusive $$D_s^{*}$$ D s ∗ weak decays. The main result is the partial decay widths, which read as $$\varGamma _{D_s^*\rightarrow l \nu } = 2.44 \times 10^{-12} \, \textrm{GeV}$$ Γ D s ∗ → l ν = 2.44 × 10 - 12 GeV , $$\varGamma _{D_s^*\rightarrow \phi l \nu } = (3.28^{+0.82}_{-0.71}) \times 10^{-14} \, \textrm{GeV}$$ Γ D s ∗ → ϕ l ν = ( 3 . 28 - 0.71 + 0.82 ) × 10 - 14 GeV , $$\varGamma _{D_s^{*} \rightarrow \phi \pi } = ( 3.81^{+1.52}_{-1.33} ) \times 10^{-14} \, \textrm{GeV}$$ Γ D s ∗ → ϕ π = ( 3 . 81 - 1.33 + 1.52 ) × 10 - 14 GeV and $$\varGamma _{D_s^{*}\rightarrow \phi \rho } = ( 1.16^{+0.42}_{-0.39} ) \times 10^{-13} \, \textrm{GeV}$$ Γ D s ∗ → ϕ ρ = ( 1 . 16 - 0.39 + 0.42 ) × 10 - 13 GeV . We show that these channels are promising in the near future, serving as the first experimental observation of weak decays of a vector meson, and would open up a new playground for precision test of the standard model.

We reanalyze the $$\Lambda _b\rightarrow p$$ Λ b → p transition form factors in the perturbative QCD (PQCD) approach by including higher-twist light-cone distribution amplitudes (LCDAs) of a $$\Lambda _b$$ Λ b baryon and a proton. The previous PQCD evaluation performed decades ago with only the leading-twist $$\Lambda _b$$ Λ b baryon and proton LCDAs gave the form factors, which are two orders of magnitude smaller than indicated by experimental data. We find that the twist-4 $$\Lambda _b$$ Λ b baryon LCDAs and the twist-4 and -5 proton LCDAs contribute dominantly, and the enhanced form factors become consistent with those from lattice QCD and other nonperturbative methods. The estimated branching ratios of the semileptonic decays $$\Lambda _b\rightarrow p\ell {\bar{\nu }}_\ell $$ Λ b → p ℓ ν ¯ ℓ and the hadronic decay $$\Lambda _b\rightarrow p\pi $$ Λ b → p π are also close to the data. It implies that the b quark mass is not really heavy enough, and higher-power contributions play a crucial role, similar to the observation made in analyses of B meson transition form factors. With the formalism established in this work, we are ready to study various exclusive heavy baryon decays systematically in the PQCD approach.

With a distinctive internal structure from all established hadrons, the beauty-charmed baryons $\Xi_{bc}$ can provide us with new points of view to decipher the strong interaction. In this work, we point out that the inclusive $\Xi_{bc} \to \Xi_{cc}^{++}+X$ decay is a golden channel for the experimental discovery of $\Xi_{bc}$ at the LHC. A unique feature of this process is that the $\Xi_{cc}^{++}$ is displaced, which greatly reduces the combinatorial background. A feasibility analysis is performed on the $\Xi_{bc}^+$ search, which is expected to have a longer lifetime than $\Xi_{bc}^0$ and thus a better displacement resolution. The $\Xi_{bc}^+ \to \Xi_{cc}^{++}+X$ branching ratio is calculated within the heavy diquark effective theory. Combining the $\Xi_{bc}$ production rate and the $\Xi_{cc}^{++}$ detection efficiency, we anticipate that hundreds of signal events will be collected during LHCb Run 3., Comment: 6 pages, 3 figures

Discoveries of tetraquarks not only enrich the hadronic spectrum but also provide more platforms to understand quantum chromodynamics. We study the production processes of hidden-charm and open-charm tetraquarks in $B$ decays by analyzing their topological amplitudes. Relations between different channels are found, which confront tests by experiments to probe the nature of the tetraquarks. Furthermore, promising channels to find more tetraquarks are proposed., Comment: 8 pages, 1 figure, 2 tables

We suggest to study the production mechanism and some details of the production properties to probe the structure of the DDπ resonance Tcc recently observed by the LHCb Collaboration. If the resonance is produced as a four-quark state, one can find the corresponding signals via measurements on the production properties which are the same as those of Ξcc, i.e., the similarity of Tcc and Ξcc in the kinematics spectra, in the baryon number enhancement, and in the string effect, etc. The color connection of the preconfinement cluster in which the cc diquark pair hadronize to the Tcc or Ξcc plays the key role for their similarity. Moreover, the production cross section of Tcc in various rapidity regions and the production ratio between Tcc to a different isospin state Tcc′ (if it exists) are also important and clear tests. On the other hand, if Tcc is produced as a hadron molecule, the measurement on the momentum correlation of DD* can be a key judgement, since it determines the production ratio. From the present available information, the calculated cross section with nonrelativistic hadron molecule model is about an order of magnitude lower than the experimental measurement.

We propose a systematic theoretical framework for the topological amplitudes of the heavy meson decays and their $SU(N)$ decomposition. In the framework, the topological amplitudes are expressed in invariant tensors and classified into tree- and penguin-operator-induced diagrams according to which four-quark operators, tree or penguin, being inserted into their effective weak vertexes. By decomposing the four-quark operators into irreducible representations of $SU(N)$ group, one can derive the $SU(N)$ irreducible amplitudes from the tensor form of the topology. Taking the $D\to PP$ decay ($P$ denoting a pseudoscalar meson) with $SU(3)_F$ symmetry as an example, we show our framework in detail. The fact that some topologies are not independent in the $SU(3)_F$ limit is explained by group theory. It is found that there are only nine independent topologies in all tree- and penguin-operator-induced diagrams contributing to the $D\to PP$ decays in the Standard Model. If a large quark-loop diagram is assumed, the large $\Delta A_{CP}$ and the very different $D^0\to K^+K^-$ and $D^0\to \pi^+\pi^-$ branching fractions can be explained with a normal $U$-spin breaking. Moreover, our framework provides a simple and systematic way to analyze the $SU(N)$ breaking effects. As examples, the linear $SU(3)_F$ breaking and the high order $U$-spin breaking in charm decays are re-investigated in our framework, which are consistent with literature. We propose the concepts of splitting and degeneracy of topologies, and use them to describe the charm-less bottom decay. We find $SU(3)_F$ analysis for the charm-less $B$ decays is different from the $D$ decays because the charm-quark loop is beyond the $SU(3)$ symmetry and should be investigated in the symmetry breaking chain of $SU(4)\to SU(3)$., Comment: 62 pages, 3 figures, version published on JHEP

The semileptonic decays of ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{(*)}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}^{(*)}\ensuremath{\ell}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ 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 $\ensuremath{\lambda}$-mode orbital excited states $(1/{2}^{\ensuremath{-}})$, and the first radial excited states $(1/{2}^{+})$ of ${\mathrm{\ensuremath{\Lambda}}}_{(c)}^{(*)}$ are considered. The discussions are given for the form factors, partial widths, branching fractions, leptonic forward-backward asymmetries, hadron polarizations, lepton polarizations, and the lepton flavor universalities. Our results are useful for the inputs of heavy baryon decays and understanding the baryon structures, and helpful for experimental measurements.

After the discovery of the double-charm baryon $$\Xi _{cc}^{++}$$ Ξ cc + + by LHCb, one of the most important topics is to search for the bottom-charm baryons which contain a b quark, a c quark and a light quark. In this work, we study the two-body non-leptonic weak decays of a bottom-charm baryon into a spin-1/2 bottomed baryon and a light pseudoscalar meson with the short-distance contributions calculated under the factorization hypothesis and the long-distance contributions considering the final-state-interaction effects. The branching fractions of all fifty-seven decay channels are estimated. The results indicate that $$\Xi _{bc}^+\rightarrow \Xi _b^0\pi ^+$$ Ξ bc + → Ξ b 0 π + , $$\Xi _{bc}^{0}\rightarrow \Xi _{b}^{-}\pi ^+$$ Ξ bc 0 → Ξ b - π + and $$\Omega _{bc}^0\rightarrow \Omega _b^-\pi ^+$$ Ω bc 0 → Ω b - π + decay modes have relatively large decay rates and thus could be used to experimentally search for the bottom-charm baryons. The topological diagrams and the SU(3) symmetry of bottom-charm baryon decays are discussed.

After the discovery of the double-charm baryon $$\Xi _{cc}^{++}$$ Ξ cc + + by LHCb, one of the most important topics is to search for the bottom-charm baryons which contain a b quark, a c quark and a light quark. In this work, we study the two-body non-leptonic weak decays of a bottom-charm baryon into a spin-1/2 bottomed baryon and a light pseudoscalar meson with the short-distance contributions calculated under the factorization hypothesis and the long-distance contributions considering the final-state-interaction effects. The branching fractions of all fifty-seven decay channels are estimated. The results indicate that $$\Xi _{bc}^+\rightarrow \Xi _b^0\pi ^+$$ Ξ bc + → Ξ b 0 π + , $$\Xi _{bc}^{0}\rightarrow \Xi _{b}^{-}\pi ^+$$ Ξ bc 0 → Ξ b - π + and $$\Omega _{bc}^0\rightarrow \Omega _b^-\pi ^+$$ Ω bc 0 → Ω b - π + decay modes have relatively large decay rates and thus could be used to experimentally search for the bottom-charm baryons. The topological diagrams and the SU(3) symmetry of bottom-charm baryon decays are discussed.

The exotic states $$X_{0,1}(2900)$$ X 0 , 1 ( 2900 ) with the quark flavor of $$cs\bar{u}\bar{d}$$ c s u ¯ d ¯ are recently observed in the mass spectrum of $$D^+K^-$$ D + K - in $$B^-\rightarrow D^-D^+K^-$$ B - → D - D + K - by the LHCb collaboration. To explore the nature of $$X_{0,1}(2900)$$ X 0 , 1 ( 2900 ) , except for analyzing their masses and decay widths as usually did in literatures, the study of their production mechanism in B-meson weak decays would provide another important information. The amplitude of $$B^-\rightarrow D^- X_{0,1}$$ B - → D - X 0 , 1 is non-factorizable. We consider the final-state-interaction effects and calculate them via the rescattering mechanism. The measured branching fractions of $$B^-\rightarrow D^- X_{0,1}$$ B - → D - X 0 , 1 are revealed. It is manifested by $${B}^-\rightarrow \Lambda _c^-\Xi _c^{(\prime )0}$$ B - → Λ c - Ξ c ( ′ ) 0 and $$\Lambda _b^0\rightarrow P_c^+K^-$$ Λ b 0 → P c + K - that the rescattering mechanism can result in the relatively large branching fractions. The similar processes of $$B^-\rightarrow \pi ^-X_{0,1}$$ B - → π - X 0 , 1 are also analyzed. The isospins of $$X_{0,1}$$ X 0 , 1 can be investigated by $$B\rightarrow DX_{0,1}^{\pm ,0}$$ B → D X 0 , 1 ± , 0 decays.

We calculate the parameters $x$ and $y$ for the $D$ meson mixing in the Standard Model by considering a dispersion relation between them. The dispersion relation for a fictitious charm quark of arbitrary mass squared $s$ is turned into an inverse problem, via which the mixing parameters at low $s$ are solved with the perturbative inputs $x(s)$ and $y(s)$ from large $s$. It is shown that nontrivial solutions for $x$ and $y$ exist, whose values around the physical charm scale agree with the data in both CP-conserving and CP-violating cases. We then predict the observables $|q/p|-1\approx 2\times 10^{-4}$ and $Arg(q/p)\approx 6\times 10^{-3}$ degrees associated with the coefficient ratio for the $D$ meson mixing, which can be confronted with more precise future measurements. Our work represents the first successful quantitative attempt to explain the $D$ meson mixing parameters in the Standard Model., 7 pages, 6 figures, v2: Version accepted in PLB. References added. Fig. 5 added

In this study, we investigate the discovery potential of double-charm tetraquarks \begin{document}$ T^{\{cc\}}_{[\bar{q}\bar{q}']} $\end{document} . We find that their production cross sections at the LHCb with \begin{document}$ \sqrt{s} = 13 $\end{document} TeV reach \begin{document}$ \mathcal{O}(10^4) $\end{document} pb, which indicates that the LHCb has collected \begin{document}$ \mathcal{O}(10^8) $\end{document} such particles. Through the decay channels of \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^{+}K^{-}\pi^{+} $\end{document} or \begin{document}$ D^0D^+\gamma $\end{document} (if stable) or \begin{document}$ T^{\{cc\}}_{[\bar{u}\bar{d}]}\to D^0D^{*+}\to D^0D^0\pi^+ $\end{document} (if unstable), it is highly expected that they get discovered at the LHCb in the near future. We also discuss the productions and decays of the double-charm tetraquarks at future Tera- \begin{document}$ Z $\end{document} factories.

An overview of the recent first observation of CP violation in the Charm sector by the LHCb collaboration. Selection of theoretical models explaining this measurement is reviewed. Finally, experimental prospects for future measurements are discussed., 4 pages, 2 figures, 1 table

This paper focuses on how to define and how to mine temporal association rules of an attributed graph sequence. Different from other temporal data, an attributed graph sequence contains edge-oriented structural data and vertex-oriented attribute data both of which vary with time. By reviewing the different forms of temporal association rules in the literature of related date types, we propose a definition of temporal association rule of an attributed graph sequence, which is a generalization of existing temporal association rules. In this definition, a two-tuple is used to describe the antecedent and consequent of a temporal association rule, which contains both structural information and attribute information. From this definition, a method for mining temporal association rules of an attributed graph sequence is given, and an Apriori algorithm-based mining algorithm is then designed. In the new mining method, two stages are given: the first one is for mining temporal structural association rules, while the second one is for mining temporal attribute association rules based on the result obtained in the first stage. This mining method exhibits good performance and high efficiency which was validated by the experiments carried on some datasets presented in this paper.

A sizable right-handed photon polarization in b→sγ is a clear signal for new physics. In this Letter, we point out that the photon helicity in b→sγ can be unambiguously extracted by combining the measurements in B→K1γ and the Cabibbo-favored D→K1e+ν decay. We propose a ratio of up-down asymmetries in D→K1e+ν 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 for extracting the photon polarization in the presence of different kaon resonances.

We analyze the capacity of future $Z$-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos $N$ are considered to be produced via the process $e^+e^-\to Z\to \nu N$ and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $\sigma(e^+e^-\to \nu N\to \nu\ell jj)$ given by the $Z$-factories with integrated luminosities of 0.1, 1 and 10 ab$^{-1}$ if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints., Comment: 17 pages, 6 figures, more complete SM background is considered compared to v1

The time-dependent CP asymmetry in B 0 → K resγ → π+π− K Sγ is sensitive to the photon polarisation in the quark level process b → sγ. While this polarisation is predominantly left-handed in the standard model, it could be modified by the existence of new physics contributions that may possess different CP properties. In this paper, we derive the CP violation formulae for B 0 → K resγ → π+π− K Sγ including the most dominant intermediate states. We propose a new observable that could be measured in a time-dependent amplitude analysis of B 0 → π+π− K Sγ decays, providing a stringent contraint on the photon polarisation. We discuss the future prospects for obtaining such constraints from measurements at Belle II and LHCb.

We study the $K^0_S-K^0_L$ asymmetries and $CP$ violations in charm-baryon decays with neutral kaons in the final state. The $K^0_S-K^0_L$ asymmetry can be used to search for two-body doubly Cabibbo-suppressed amplitudes of charm-baryon decays, with the one in $\Lambda^+_c\to pK^0_{S,L}$ as a promising observable. Besides, it is studied for a new $CP$-violation effect in these processes, induced by the interference between the Cabibbo-favored and doubly Cabibbo-suppressed amplitudes with the neutral kaon mixing. Once the new CP-violation effect is determined by experiments, the direct $CP$ asymmetry in neutral kaon modes can then be extracted and used to search for new physics. The numerical results based on $SU(3)$ symmetry will be tested by the experiments in the future., Comment: 15 pages, 3 tables. Version published in JHEP

Invited viewpoint on the role of decay in the search of the single-charge double-charm baryon by the LHCb Collaboration., Comment: 2 pages

We find a new $CP$-violation effect in charm decays into neutral kaons, which results from the interference between two tree (Cabibbo-favored and doubly Cabibbo-suppressed) amplitudes with the mixing of final-state mesons. This effect, estimated to be of order of $10^{-3}$, is much larger than the direct $CP$ asymmetries in these decays, but missed in the literature. If confirmed, the new effect has to be taken into account, as the above direct $CP$ asymmetries are used to search for new physics.

After the discovery of the Higgs boson, several future experiments have been proposed to study the Higgs boson properties, including two circular lepton colliders, the CEPC and the FCC-ee, and one linear lepton collider, the ILC. We evaluate the precision reach of these colliders in measuring the branching ratios of the charged lepton flavor violating Higgs decays $$H\rightarrow e^\pm \mu ^\mp $$ H→e±μ∓ , $$e^\pm \tau ^\mp $$ e±τ∓ and $$\mu ^\pm \tau ^\mp $$ μ±τ∓ . The expected upper bounds on the branching ratios given by the circular (linear) colliders are found to be $${\mathcal {B}}(H\rightarrow e^\pm \mu ^\mp ) < 1.2~(2.1) \times 10^{-5}$$ B(H→e±μ∓)<1.2(2.1)×10-5 , $${\mathcal {B}}(H\rightarrow e^\pm \tau ^\mp ) < 1.6~(2.4) \times 10^{-4}$$ B(H→e±τ∓)<1.6(2.4)×10-4 and $${\mathcal {B}}(H\rightarrow \mu ^\pm \tau ^\mp ) < 1.4~(2.3) \times 10^{-4}$$ B(H→μ±τ∓)<1.4(2.3)×10-4 at 95% CL, which are improved by one to two orders compared to the current experimental bounds. We also discuss the constraints that these upper bounds set on certain theory parameters, including the charged lepton flavor violating Higgs couplings, the corresponding parameters in the type-III 2HDM, and the new physics cut-off scales in the SMEFT, in RS models and in models with heavy neutrinos.

After the discovery of the Higgs boson, several future experiments have been proposed to study the Higgs boson properties, including two circular lepton colliders, the CEPC and the FCC-ee, and one linear lepton collider, the ILC. We evaluate the precision reach of these colliders in measuring the branching ratios of the charged lepton flavor violating Higgs decays $$H\rightarrow e^\pm \mu ^\mp $$ , $$e^\pm \tau ^\mp $$ and $$\mu ^\pm \tau ^\mp $$ . The expected upper bounds on the branching ratios given by the circular (linear) colliders are found to be $${\mathcal {B}}(H\rightarrow e^\pm \mu ^\mp ) < 1.2~(2.1) \times 10^{-5}$$ , $${\mathcal {B}}(H\rightarrow e^\pm \tau ^\mp ) < 1.6~(2.4) \times 10^{-4}$$ and $${\mathcal {B}}(H\rightarrow \mu ^\pm \tau ^\mp ) < 1.4~(2.3) \times 10^{-4}$$ at 95% CL, which are improved by one to two orders compared to the current experimental bounds. We also discuss the constraints that these upper bounds set on certain theory parameters, including the charged lepton flavor violating Higgs couplings, the corresponding parameters in the type-III 2HDM, and the new physics cut-off scales in the SMEFT, in RS models and in models with heavy neutrinos.