arXiv subjects

Wei-Hong Liang

Publications and source records attributed to Wei-Hong Liang.

At least 73 records · Page 4Linked to original sources

arXiv2018

$\boldsymbol{Ω_b^- \to (Ξ_c^+ \, K^-) \, π^-}$ and the $\boldsymbol{Ω_c}$ states

We study the weak decay $Ω_b^- \to (Ξ_c^+ \, K^-) \, π^-$, in view of the narrow $Ω_c$ states recently measured by the LHCb collaboration and later confirmed by the Belle collaboration. The $Ω_c(3050)$ and $Ω_c(3090)$ are described as meson-baryon molecular states, using an extension of the local hidden gauge approach in coupled channels. We investigate the $ΞD$, $Ξ_c \bar K$ and $Ξ_c^\prime \bar K$ invariant mass distributions making predictions that could be confronted with future experiments, providing useful information that could help determine the quantum numbers and nature of these states.

hep-ph↗

arXiv2018

Triangle singularity enhancing isospin violation in $\bar B_s^0 \to J/ψπ^0 f_0(980)$

We perform calculations for the $\bar B_s^0 \to J/ψπ^0 f_0(980)$ and $\bar B_s^0 \to J/ψπ^0 a_0(980)$ reactions, showing that the first one is isospin-suppressed while the second one is isospin-allowed. The reaction proceeds via a triangle mechanism, with $\bar B_s^0 \to J/ψK^* \bar K +c.c.$, followed by the decay $K^* \to Kπ$ and a further fusion of $K\bar K$ into the $f_0(980)$ or $a_0(980)$. We show that the mechanism develops a singularity around the $π^0 f_0(980)$ or $π^0 a_0(980)$ invariant mass of 1420 MeV where the $π^0 f_0$ and $π^0 a_0$ decay modes are magnified and also the ratio of $π^0 f_0$ to $π^0 a_0$ production. Using experimental information for the $\bar B_s^0 \to J/ψK^* \bar K +c.c.$ decay, we are able to obtain absolute values for the reactions studied which fall into the experimentally accessible range. The reactions proposed and the observables evaluated, when contrasted with actual experiments should be very valuable to obtain information on the nature of the low lying scalar mesons.

hep-ph↗

arXiv2018

Production and mixing of scalar mesons in $η_c$ and $χ_{c1}$ decays

We briefly discuss how the chiral unitary approach in coupled channels and $SU(3)$ symmetry can be used to describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ reaction, recently measured by the BESIII collaboration. In this reaction a very strong peak for the $a_0(980)$ can be seen in the $ηπ$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $π^+π^-$. Next, we show the predictions made with the same model for the analogous decay $η_c \to ηπ^+ π^-$, which could also be measured experimentally. We discuss the differences of these two reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars. Furthermore, we comment on a new recent work where the same model was used to study the $a_0(980) - f_0(980)$ mixing in the $χ_{c1} \to π^0 π^0 η$ and $χ_{c1} \to π^0 π^+ π^-$ reactions, showing that quantitative agreement with the experimental measurement of this mixing, also performed by BESIII, can be obtained, revealing interesting aspects of the dynamics of this process and the importance of coupled channels.

hep-ph↗

arXiv2018

Hidden charm pentaquark and $Λ(1405)$ in the $Λ^0_b \to η_c K^- p (πΣ)$ reaction

We have performed a study of the $Λ^0_b \to η_c K^- p$ and $Λ^0_b \to η_c πΣ$ reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the $K^- p$ produced only couples to $Λ^*$ states, not $Σ^*$ and that the $πΣ$ state is only generated from final state interaction of $\bar{K}N$ and $ηΛ$ channels which are produced in a primary stage. This guarantees that the $πΣ$ state is generated in isospin $I=0$ and we see that the invariant mass produces a clean signal for the $Λ(1405)$ of higher mass at $1420$ MeV. We also study the $η_c p$ final state interaction, which is driven by the excitation of a hidden charm resonance predicted before. We relate the strength of the different invariant mass distributions and find similar strengths that should be clearly visible in an ongoing LHCb experiment. In particular we predict that a clean peak should be seen for a hidden charm resonance that couples to the $η_c p$ channel in the invariant $η_c p$ mass distribution.

hep-ph↗

arXiv2017

Production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ and $η_c \to ηπ^+ π^-$ decays

Using the chiral unitary approach in coupled channels and $SU(3)$ symmetry we describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $χ_{c1} \to ηπ^+ π^-$ reaction, recently performed by the BESIII collaboration. A very strong peak for the $a_0(980)$ can be seen in the $ηπ$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $π^+π^-$. Next, we make predictions for the analogous decay $η_c \to ηπ^+ π^-$, which could also be measured experimentally. We discuss the differences of these reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars.

hep-ph↗

arXiv2017

Role of a triangle singularity in the $γp\rightarrow K^+ Λ(1405)$ reaction

We show the effects of a triangle singularity mechanism for the $γp \to K^+Λ(1405)$ reaction. The mechanism has a $N^*$ resonance around 2030 MeV, which decays into $K^* Σ$. The $K^*$ decays to $K^+ π$, and the $πΣ$ merge to form the $Λ(1405)$. This mechanism produces a peak around $\sqrt{s} = 2110$ MeV, and has its largest contribution around cos$θ=0$. The addition of this mechanism to other conventional ones, leads to a good reproduction of ${\rm d}σ/{\rm dcos}θ$ and the integrated cross section around this energy, providing a solution to a problem encountered in previous theoretical models.

hep-ph↗

arXiv2016

Predictions for $η_c \to ηπ^+ π^-$ producing $f_0(500)$, $f_0(980)$ and $a_0(980)$

We perform calculations for the $η_c \to ηπ^+ π^-$ decay using elements of SU(3) symmetry to see the weight of different trios of pseudoscalars produced in this decay, prior to the final state interaction of the mesons. After that, the interaction of pairs of mesons, leading finally to $ηπ^+ π^-$, is done using the chiral unitary approach. We evaluate the $π^+ π^-$ and $πη$ mass distributions and find large and clear signals for $f_0(500)$, $f_0(980)$ and $a_0(980)$ excitation. The reaction is similar to the $χ_{c1} \to ηπ^+ π^-$, which has been recently measured at BESIII and its implementation and comparison with these predictions will be very valuable to shed light on the nature of the low mass scalar mesons.

hep-ph↗

arXiv2016

Revising the $f_1(1420)$ resonance

We have studied the production and decay of the $f_1(1285)$ into $πa_0(980)$ and $K^* \bar K$ as a function of the mass of the resonance and find a shoulder around 1400 MeV, tied to a triangle singularity, for the $πa_0(980)$ mode, and a peak around 1420 MeV with about 60 MeV width for the $K^* \bar K$ mode. Both these features agree with the experimental information on which the $f_1(1420)$ resonance is based. In addition, we find that if the $f_1(1420)$ is a genuine resonance, coupling mostly to $K^* \bar K$ as seen experimentally, one finds unavoidably about a 20\% fraction for $πa_0(980)$ decay of this resonance, in drastic contradiction with all experiments. Altogether, we conclude that the $f_1(1420)$ is not a genuine resonance, but the manifestation of the $πa_0(980)$ and $K^* \bar K$ decay modes of the $f_1(1285)$ at higher energies than the nominal one.

hep-ph↗

arXiv2016

Semileptonic $Λ_b \to \bar ν_l l Λ_c(2595)$ and $Λ_b \to \bar ν_l l Λ_c(2625)$ decays in the molecular picture of $Λ_c(2595)$ and $Λ_c(2625)$

We evaluate the partial decay widths for the semileptonic $Λ_b \to \bar ν_l l Λ_c(2595)$ and $Λ_b \to \bar ν_l l Λ_c(2625)$ decays from the perspective that these two $Λ^*_c$ resonances are dynamically generated from the $DN$ and $D^*N$ interaction with coupled channels. We find that the ratio of the rates obtained for these two reactions is compatible with present experimental data and is very sensitive to the $D^* N$ coupling, which becomes essential to obtain agreement with experiment. Together with the results obtained for the $Λ_b \to π^- Λ^*_c$ reactions, it gives strong support to the molecular picture of the two $Λ^*_c$ resonances and the important role of the $D^*N$ component neglected in prior studies of the $Λ_c(2595)$ from the molecular perspective.

hep-ph↗

arXiv2016

$Λ_b \to π^- (D_s^-) Λ_c(2595),~π^- (D_s^-) Λ_c(2625)$ decays and $DN,~D^*N$ molecular components

From the perspective that the $Λ_c(2595)$ and $Λ_c(2625)$ are dynamically generated resonances from the $DN,~D^*N$ interaction and coupled channels, we have evaluated the rates for $Λ_b \to π^- Λ_c(2595)$ and $Λ_b \to π^- Λ_c(2625)$ up to a global unknown factor that allows us to calculate the ratio of rates and compare with experiment, where good agreement is found. Similarly, we can also make predictions for the ratio of rates of the, yet unknown, decays of $Λ_b \to D_s^- Λ_c(2595)$ and $Λ_b \to D_s^- Λ_c(2625)$ and make estimates for their individual branching fractions.

hep-ph↗

arXiv2016

Determination of the $\boldsymbol{η^3{\rm He}}$ threshold structure from the low energy $\boldsymbol{pd \to η^3{\rm He}}$ reaction

We analyze the data on cross sections and asymmetries for the $pd (dp) \to η^3{\rm He}$ reaction close to threshold and look for bound states of the $η^3 {\rm He}$ system. Rather than parameterizing the scattering matrix, as is usually done, we develop a framework in which the $η^3 {\rm He}$ optical potential is the key ingredient, and its strength, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the $η^3 {\rm He}$ loop function incorporates the range of the interaction given by the empirical $^3 {\rm He}$ density. We find a local Breit Wigner form of the $η^3$He amplitude $T$ below threshold with a clear peak in $|T|^2$, which corresponds to an $η^3 {\rm He}$ binding of about 0.3 MeV and a width of about 3 MeV. By fitting the potential we can also evaluate the $η^3 {\rm He}$ scattering length, including its sign, thus resolving the ambiguity in the former analyses.

nucl-th↗

arXiv2016

$f_0(500)$, $f_0(980)$ and $a_0(980)$ production in the $χ_{c1} \to ηπ^+π^-$ reaction

We study the $χ_{c1} \to ηπ^+ π^-$ decay, paying attention to the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ from the final state interaction of pairs of mesons that can lead to these three mesons in the final state, which is implemented using the chiral unitary approach. Very clean and strong signals are obtained for the $a_0(980)$ excitation in the $ηπ$ invariant mass distribution and for the $f_0(500)$ in the $π^+ π^-$ mass distribution. A smaller, but also clear signal for the $f_0(980)$ excitation is obtained. The results are contrasted with experimental data and the agreement found is good, providing yet one more test in support of the picture where these resonances are dynamically generated from the meson-meson interaction.

hep-ph↗

arXiv2016

Workshop on Physics with Neutral Kaon Beam at JLab (KL2016) Mini-Proceedings

The KL2016 Workshop is following the Letter of Intent LoI12-15-001 "Physics Opportunities with Secondary KL beam at JLab" submitted to PAC43 with the main focus on the physics of excited hyperons produced by the Kaon beam on unpolarized and polarized targets with GlueX setup in Hall D. Such studies will broaden a physics program of hadron spectroscopy extending it to the strange sector. The Workshop was organized to get a feedback from the community to strengthen physics motivation of the LoI and prepare a full proposal. Further details about the Workshop can be found on the web page of the conference: http://www.jlab.org/conferences/kl2016/index.html .

hep-ph↗

arXiv2016

Weak decays of heavy hadrons into dynamically generated resonances

In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$, $D$, $Λ_b$, $Λ_c$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q \bar q$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.

hep-ph↗

arXiv2016

$\bar B^0$, $B^-$ and $\bar B^0_s$ decays into $J/ψ$ and $K \bar K$ or $πη$

We study the $\bar B^0_s \to J/ψK^+ K^-$, $\bar B^0 \to J/ψK^+ K^-$, $B^- \to J/ψK^0 K^-$, $\bar B^0 \to J/ψπ^0 η$ and $B^- \to J/ψπ^- η$ decays and compare their mass distributions with those obtained for the $\bar B^0_s \to J/ψπ^+ π^-$ and $\bar B^0 \to J/ψπ^+ π^-$. The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial Cabibbo-Kobayashi-Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part of the theory and thus, up to a global normalization factor, all the invariant mass distributions are predicted with no free parameters. Comparison is made with the limited experimental information available. Further comparison of these results with coming LHCb measurements will be very valuable to make progress in our understanding of the meson-meson interaction and the nature of the low lying scalar meson resonances, $f_0(500), f_0(980)$ and $a_0(980)$.

hep-ph↗

arXiv2015

Looking for a hidden-charm pentaquark state with strangeness $S=-1$ from $Ξ^-_b$ decay into $J/ψK^- Λ$

Assuming that the recently observed hidden-charm pentaquark state, $P_c(4450)$, is of molecular nature as predicted in the unitary approach, we propose to study the decay of $Ξ^-_b\rightarrow J/ψK^- Λ$ to search for the strangeness counterpart of the $P_c(4450)$. There are three ingredients in the decay mechanism: the weak decay mechanism, the hadronization mechanism, and the finite state interactions in the meson-baryon system of strangeness $S=-2$ and isospin $I=1/2$ and of the $J/ψΛ$. All these have been tested extensively. As a result, we provide a genuine prediction of the differential cross section where a strangeness hidden-charm pentaquark state, the counterpart of the $P_c(4450)$, can be clearly seen. The decay rate is estimated to be of similar magnitude as the $Λ_b^0\rightarrow J/ψK^- p$ observed by the LHCb collaboration.

hep-ph↗

arXiv2015

$\bar B^0$ decay into $D^0$ and $f_0(500)$, $f_0(980)$, $a_0(980)$, $ρ$ and $\bar B^0_s$ decay into $D^0$ and $κ(800)$, $K^{*0}$

We make predictions for ratios of branching fractions of $\bar B^0$ decays into $D^0$ and the scalar mesons $f_0(500)$, $f_0(980)$, $a_0(980)$, plus $\bar B^0_s$ decay into $D^0$ and $κ(800)$. We also compare the $π^+ π^-$ production in the scalar channel with that observed in the $ρ$ channel and make predictions for the $\bar B^0_s$ decay into $D^0$ and $K^*(892)$, comparing the strength of this channel with that of $κ(800)$ production. The work is based on results of the chiral unitary approach where the scalar resonances are generated from the pseudoscalar-pseudoscalar interaction. Up to an arbitrary normalization, the mass distributions and rates for decays into the scalar resonances are predicted with no free parameters. Comparison with experimental data is done when available.

hep-ph↗

arXiv2015

Predictions for the $\bar B^0 \to \bar K^{*0} X (YZ)$ and $\bar B^0_s \to ϕX (YZ)$ with $X(4160), Y(3940), Z(3930)$

We investigate the decay of $\bar B^0 \to \bar K^{*0} R$ and $\bar B^0_s \to ϕR$ with $R$ being the $X(4160)$, $Y(3940)$, $Z(3930)$ resonances. Under the assumption that these states are dynamically generated from the vector-vector interaction, as has been concluded from several theoretical studies, we use a reaction mechanism of quark production at the elementary level, followed by hadronization of one final $q \bar q$ pair into two vectors and posterior final state interaction of this pair of vector mesons to produce the resonances. With this procedure we are able to predict five ratios for these decays, which are closely linked to the dynamical nature of these states, and also predict the order of magnitude of the branching ratios which we find of the order of $10^{-4}$, well within the present measurable range. In order to further test the dynamical nature of these resonances we study the $\bar B^0_s \to ϕD^* \bar D^*$ and $\bar B^0_s \to ϕD_s^* \bar D_s^*$ decays close to the $D^* \bar D^*$ and $D_s^* \bar D_s^*$ thresholds and make predictions for the ratio of the mass distributions in these decays and the $\bar B^0_s \to ϕR$ decay widths. The measurement of these decays rates can help unravel the nature of these resonances.

hep-ph↗