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Xin-Heng Guo

Publications and source records attributed to Xin-Heng Guo.

At least 55 records · Page 3Linked to original sources

Studying the bound state of the $B\bar{K}$ system in the Bethe-Salpeter formalism

In this work, we study the $B\bar{K}$ molecule in the Bethe-Salpeter (BS) equation approach. With the kernel containing one-particle-exchange diagrams and introducing two different form factors (monopole form factor and dipole form factor) in the vertex, we solve the BS equation numerically in the covariant instantaneous approximation. We investigate the isoscalar and isovector $B\bar{K}$ systems, and we find $X(5568)$ cannot be a $B\bar{K}$ molecule.

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Analyzing $Ξ(1620)$ in the molecule picture in the Bethe-Salpeter equation approach

In this work, we assume that the observed state $Ξ(1620)$ is a $s$-wave $Λ\bar{K}$ or $Σ\bar{K}$ bound state. Based on this molecule picture, we establish the Bethe-Salpeter equations for $Ξ(1620)$ in the ladder and instantaneous approximations. We solve the Bethe-Salpeter equations for the $Λ\bar{K}$ and $Σ\bar{K}$ systems numerically and find that the $Ξ(1620)$ can be explained as $Λ\bar{K}$ and $Σ\bar{K}$ bound states with $J^P=1/2^-$, respectively. Then we calculate the decay widths of $Ξ(1620)\rightarrowΞπ$ in these two different molecule pictures systems, respectively.

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Masses of doubly heavy baryons in the Bethe-Salpeter equation approach

A doubly heavy baryon can be regarded as composed of a heavy diquark and a light quark. In this picture, we study the masses of the doubly heavy diquarkes in the Bethe-Salpeter (BS) formalism first, which are then used as one of the inputs in studying the masses of the doubly heavy baryons in the quark-diquark model. We establish the BS equations for both the heavy diquarks and the heavy baryons with and without taking the heavy quark limit, respectively. These equations are solved numerically with the kernel containing the scalar confinement and one-gluon-exchange terms. The mass of the doubly charmed baryon $Ξ_{cc}^{(\ast)}$ is obtained in both approaches, $3.60\sim3.65\,\rm GeV$ ($Ξ_{cc}^{(\ast)}$) under the heavy quark limit, $3.53\sim3.56\,\rm GeV$ for $Ξ_{cc}$ and $3.61\sim3.63\,\rm GeV$ for $Ξ_{cc}^\ast$ without taking the heavy quark limit. The masses of $Ξ_{bc}^\prime$, $Ξ_{bc}^{(\ast)}$, $Ξ_{bb}^{(\ast)}$, $Ω_{cc}^{(\ast)}$, $Ω_{bc}^\prime$, $Ω_{bc}^{(\ast)}$ and $Ω_{bb}^{(\ast)}$ are also predicted in the same way. We find that the corrections to the results in the heavy quark limit are about $-0.02\,\rm GeV\sim-0.11\,\rm GeV$ for the masses of the doubly heavy baryons.

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Study of $CP$ Violation in $B^-\rightarrow K^- π^+π^-$ and $B^-\rightarrow K^- σ(600)$ decays in the QCD factorization approach

In this work, we study the localized $CP$ violation in $B^-\rightarrow K^-π^+π^-$ and $B^-\rightarrow K^- σ(600)$ decays by employing the quasi two-body QCD factorization approach. Both the resonance and the nonresonance contributions are studied for the $B^-\rightarrow K^-π^+π^-$ decay. The resonance contributions include those not only from $[ππ]$ channels including $σ(600)$, $ρ^0(770)$ and $ω(782)$ but also from $[Kπ]$ channels including $K^*(892)$, $K_0^*(1430)$, $K^*(1410)$, $K^*(1680)$ and $K_2^*(1430)$. By fitting the experimental data $\mathcal{A_{CP}}(K^-π^+π^-)=0.678\pm0.078\pm0.0323\pm0.007$ for $m_{K^-π^+}^2<15$ $\mathrm{GeV}^2$ and $0.08<m_{π^+π^-}^2<0.66$ $\mathrm{GeV}^2$, we get the end-point divergence parameters in our model, $ϕ_S \in [4.75, 5.95]$ and $ρ_S\in[4.2, 8]$. Using these results for $ρ_S$ and $ϕ_S$, we predict that the $CP$ asymmetry parameter $\mathcal{A_{CP}} \in [-0.094, -0.034]$ and the branching fraction $\mathcal{B} \in [1.82, 20.0]\times10^{-5}$ for the $B^-\rightarrow K^-σ(600)$ decay. In addition, we also analyse contributions to the localized $CP$ asymmetry $\mathcal{A_{CP}}(B^-\rightarrow K^-π^+π^-)$ from $[ππ]$, $[Kπ]$ channel resonances and nonresonance individually, which are found to be $\mathcal{A_{CP}}(B^-\rightarrow K^-[π^+π^-] \rightarrow K^-π^+π^-)=0.585\pm0.045$, $\mathcal{A_{CP}}(B^-\rightarrow [K^-π^+] π\rightarrow K^-π^+π^-)=0.086\pm0.021$ and $\mathcal{A_{CP}}^{NR}(B^-\rightarrow K^-π^+π^-)=0.061\pm0.0042$, respectively. Comparing these results, we can see that the localized $CP$ asymmetry in the $B^-\rightarrow K^-π^+π^-$ decay is mainly induced by the $[ππ]$ channel resonances while contributions from the $[Kπ]$ channel resonances and nonresonance are both very small.

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Residues of $Λ_Q$-type and $Σ_Q$-type Baryons in the Bethe-Salpeter Equation Approach

We study the residues of $Λ_Q$-type baryons ($Λ_Q$ and $Ξ_Q^A$) $(Q=b,c)$ and $Σ_Q$-type baryons ($Σ_Q^{(\ast)}$, $Ξ_Q^{S(\ast)}$ and $Ω_Q^{(\ast)}$) in the quark-diquark model within the Bethe-Salpeter (BS) formalism. These residues can be used, for example, in the calculations of the amplitudes in the scattering processes. After constructing the baryonic currents in the BS formalism, we derive the relations between the BS wave functions and the residues for these baryons. The BS equations are solved numerically with the kernel including the scalar confinement and the one gluon exchange terms and with the covariant instantaneous approximation being employed in the calculations. Finally, we obtain the numerical values of the residues $0.103\,\rm GeV\sim0.224\,\rm GeV$ for $Λ_Q$, $0.143\,\rm GeV\sim0.215\,\rm GeV$ for $Ξ_Q^A$, $0.262\,\rm GeV\sim0.361\,\rm GeV$ for $Σ_Q^{(\ast)}$, $0.313\,\rm GeV\sim0.460\,\rm GeV$ for $Ξ_Q^{S(\ast)}$ and $0.473\,\rm GeV\sim0.571\,\rm GeV$ for $Ω_Q^{(\ast)}$ in the ranges of the parameters in our model.

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Study of $CP$ Violations in $B^-\rightarrow K^- π^+π^-$ and $B^-\rightarrow K^- f_0(500)$ decays in the QCD factorization approach

Within the QCD factorization approach, we study the $CP$ violations in $B^-\rightarrow K^-π^+π^-$ and $B^-\rightarrow K^- f_0(500)$ decays. We find the experimental data of the localized $CP$ asymmetry in $B^-\rightarrow K^-π^+π^-$ decays in the region $m_{K^-π^+}^2<15$ $\mathrm{GeV}^2$ and $0.08<m_{π^+π^-}^2<0.66$ $\mathrm{GeV}^2$ can be explained by the interference of two intermediate resonances, $ρ^0(770)$ and $f_0(500)$ when the parameters in our interference model are in the allowed ranges, i.e. the relative strong phase $δ\in[0, 1.745]\cup[3.578, 6.266]$ and the end-point divergence parameters $ρ_S\in[2.790, 5.290]$ and $ϕ_S \in [1.518, 5.183]$. With the obtained allowed ranges for $ρ_S$ and $ϕ_S$, we obtain the predictions for the $CP$ asymmetry parameter $A_{CP} \in [-0.259, 0.006]$ and the branching fraction $\mathcal{B} \in [0.585, 3.230]\times10^{-5}$ for $B^-\rightarrow K^-f_0(500)$ decay modes.

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Electromagnetic form factors of $Λ_c$ in the Bethe-Salpeter equation approach

We study the electromagnetic form factors (EMFFs) of $Λ_c$ and the quark and diquark current contributes to the EMFFs of $Λ_c$ in the space-like (SL) region in the Bethe-Salpeter equation approach. In this picture, the heavy baryon $Λ_c $ is regarded as composed of a heavy quark and a scalar diquark. We find that for different values of parameters the quark and diquark current contribute to the EMFFs of $Λ_c$ is very different, but the total contribute to the EMFFs of $Λ_c$ is similarly. The EMFFs of $Λ_c$ are similar to those of other baryons (proton, $Ξ^-$, $Σ^+$) with a peak at $ω=1$ ($ω=v^\prime \cdot v $ is the velocity transfer between the initial state (with velocity $v$) and the final state (with velocity $v^\prime$) of $Λ_c$).

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Possible open-charmed pentaquark molecule $Ω_c(3188)$ --- the $D Ξ$ bound state --- in the Bethe-Salpeter formalism

We study the $S$-wave $DΞ$ bound state in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. With the kernel generated by the hadronic effective Lagrangian, two open-charmed bound states, which quantum numbers are $I=0$, $J^P=(\frac{1}{2})^-$ and $I=1$, $J^P=(\frac{1}{2})^-$, respectively, are predicted as new candidates of hadronic pentaquark molecules in our formalism. If existing, they could contribute to the broad 3188 eV structure near the five new narrow $Ω_c$ states observed recently by the LHCb Collaboration.

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X(3872) as a molecular $D\bar{D}^*$ state in the Bethe-Salpeter equation approach

We discuss the possibility that the X(3872) can be a $D\bar{D}^*$ molecular bound state in the Bethe-Salpeter equation approach in the ladder and instantaneous approximations. We show that the $D\bar{D}^*$ bound state with quantum numbers $J^{PC}=1^{++}$ exists. We also calculate the decay width of $X(3872) \rightarrow γJ/ψ$ channel and compare our result with those from previous calculations.

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Studying the bound state of the $K^-p$ system in the Bethe-Salpeter formalism

We study the $s$-wave kaon-nucleon bound state with the strangeness $S=-1$ in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. We solve the Bethe-Salpeter equation of the bound state and obtain the Bethe-Salpeter amplitude. It is shown that the $K^-p$ bound state exists in this formalism. We also study the decay width of the bound state based on the Bethe-Salpeter techniques. The mass of this bound state is 1422 MeV and its decay width is obviously smaller than that of $Λ(1405)$. These results indicate that there may be some other structures in the observed resonance.

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Spectra of charmed and bottom baryons with hyperfine interaction

Up to now, the excited charmed and bottom baryon states are still not well studied both experimentally and theoretically. In the present paper, we predict the mass of $Ω_b^*$, the only $L = 0$ baryon state which has not been observed, to be 6069.2 MeV. The spectra of charmed and bottom baryons with the orbital angular momentum $L = 1$ are studied in two popular constituent quark models, the Goldstone boson exchange (GBE) and the one gluon exchange (OGE) hyperfine interaction models, respectively. Inserting the latest experimental data from the "Review of Particle Physics", we find that in the GBE model, there exist some multiplets ($Σ_{c(b)}$, $Ξ'_{c(b)}$ and $Ω_{c(b)}$) which total spins of three quarks in their lowest energy states are 3/2, but in the OGE model there is no such phenomenon. This is the most important difference between the GBE and OGE models. These results can be tested in the near future. We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for determining which hyperfine interaction model is realized in nature.

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Spectroscopy of singly, doubly, and triply bottom baryons

Recently, some singly bottom baryons have been established experimentally, but none of doubly or triply bottom baryons has been observed. Under the Regge phenomenology, the mass of a ground state unobserved doubly or triply bottom baryon is expressed as a function of masses of the well established light baryons and singly bottom baryons. Then, the values of Regge slopes and Regge intercepts for baryons containing one, two, or three bottom quarks are calculated. After that, masses of the orbitally excited singly, doubly, and triply bottom baryons are estimated. Our predictions may be useful for the discovery of these baryons and the $J^P$ assignment of them.

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Electromagnetic form factors of $Λ_b$ in the Bethe-Salpeter equation approach

The heavy baryon $Λ_b $ is regarded as composed of a heavy quark and a scalar diquark which has good spin and isospin quantum numbers. In this picture, we calculate the electromagnetic (EM) form factors of $Λ_b$ in the Bethe-Salpeter equation approach. We find that the shapes of the EM form factors of $Λ_b$ are similar to those of $Λ$, which have a peak at about $ω=1$, but the amplitudes are much smaller than those of $Λ$.

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Detection of supernova neutrinos at spallation neutron sources

After considering the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein effects, the neutrino collective effects, and the Earth matter effects, the detection of supernova neutrinos at China Spallation Neutron Sources is studied and the event numbers of different flavor supernova neutrinos observed through various reaction channels are calculated with the neutrino energy spectra described by the Fermi-Dirac distribution and "beta fit" distribution respectively. Furthermore, the numerical calculation method of supernova neutrino detection on the Earth is applied to some other spallation neutron sources, and the total event numbers of supernova neutrinos observed through different reactions channels are given.

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Localized direct CP violation in $B^\pm\rightarrow ρ^0 (ω)π^\pm\rightarrow π^+ π^-π^\pm$

We study the localized direct CP violation in the hadronic decays $B^\pm\rightarrow ρ^0 (ω)π^\pm\rightarrowπ^+ π^-π^\pm$, including the effect caused by an interesting mechanism involving the charge symmetry violating mixing between $ρ^0$ and $ω$. We calculate the localized integrated direct CP violation when the low invariant mass of $π^+π^-$ [$m(π^+π^-)_{low}$] is near $ρ^0(770)$. For five models of form factors investigated, we find that the localized integrated direct CP violation varies from -0.0170 to -0.0860 in the ranges of parameters in our model when $0.750<m(π^+π^-)_{low}<0.800$\,GeV. This result, especially the sign, agrees with the experimental data and is independent of form factor models. The new experimental data shows that the signs of the localized integrated CP asymmetries in the regions $0.470<m(π^+π^-)_{low}<0.770$\,GeV and $0.770<m(π^+π^-)_{low}<0.920$\,GeV are positive and negative, respectively. We find that $ρ$-$ω$ mixing makes the localized integrated CP asymmetry move towards the negative direction, and therefore contributes to the sign change in those two regions. This behavior is also model independent. We also calculate the localized integrated direct CP violating asymmetries in the regions $0.470<m(π^+π^-)_{low}<0.770$\,GeV and $0.770<m(π^+π^-)_{low}<0.920$\,GeV and find that they agree with the experimental data in some models of form factors.

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Masses of doubly and triply charmed baryons

Until now, the first reported doubly charmed baryon $Ξ_{cc}^{+}(3520)$ is still a puzzle. It was discovered and confirmed by SELEX collaboration, but not confirmed by LHCb, BABAR, BELLE, FOCUS, or any other collaboration. In the present paper, by employing Regge phenomenology, we first express the mass of the ground state ($L$=0) doubly charmed baryon $Ω_{cc}^{*+}$ as a function of masses of the well established light baryons and singly charmed baryons. Inserting the recent experimental data, the mass of $Ω_{cc}^{*+}$ is given to be 3809$\pm$36 MeV, which is independent of any unobservable parameters. Then, with the quadratic mass relations, we calculate the masses of the ground state triply charmed baryon $Ω_{ccc}^{++}$ and doubly charmed baryons $Ξ_{cc}^{(*)++}$, $Ξ_{cc}^{(*)+}$, and $Ω_{cc}^{+}$ (the mass of $Ξ_{cc}^{+}$ is determined as 3520$^{+41}_{-40}$ MeV, which agrees with the mass of $Ξ_{cc}^{+}(3520)$). The isospin splitting $M_{Ξ_{cc}^{++}} - M_{Ξ_{cc}^{+}} = 0.4 \pm 0.3$ MeV. After that, masses of the orbitally excited ($L$=1,2,3) doubly and triply charmed baryons are estimated. The results are reasonable comparing with those extracted in many other approaches. We suggest more efforts to study doubly and triply charmed baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for numerically examining whether the linear mass relations or the quadratic mass relations are realized in nature. Our predictions are useful for the discovery of unobserved doubly and triply charmed baryon states and the $J^P$ assignment of these states.

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Possible large $CP$ violation in three body decays of heavy baryon

We propose a new mechanism which can introduce large $CP$ asymmetries in the phase spaces of three-body decays of heavy baryons. In this mechanism, a large $CP$ asymmetry is induced by the interference of two intermediate resonances, which subsequently decay into two different combinations of final particles. We apply this mechanism to the decay channel $Λ_b^0 \to p π^0π^-$, and find that the differential $CP$ asymmetry can reach as large as $50\%$, while the regional $CP$ asymmetry can reach as large as $16\%$ in the interference region of the phase space.

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Neutrino Physics with JUNO

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy as a primary physics goal. It is also capable of observing neutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, solar neutrinos, as well as exotic searches such as nucleon decays, dark matter, sterile neutrinos, etc. We present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. By detecting reactor antineutrinos from two power plants at 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4 sigma significance with six years of running. The measurement of antineutrino spectrum will also lead to the precise determination of three out of the six oscillation parameters to an accuracy of better than 1\%. Neutrino burst from a typical core-collapse supernova at 10 kpc would lead to ~5000 inverse-beta-decay events and ~2000 all-flavor neutrino-proton elastic scattering events in JUNO. Detection of DSNB would provide valuable information on the cosmic star-formation rate and the average core-collapsed neutrino energy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400 events per year, significantly improving the statistics of existing geoneutrino samples. The JUNO detector is sensitive to several exotic searches, e.g. proton decay via the $p\to K^++\barν$ decay channel. The JUNO detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics. It holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our Universe.

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