arXiv subjects

En Wang

Publications and source records attributed to En Wang.

108 records · Page 6Linked to original sources

arXiv2017

Analysis of the $B^+\to J/ψϕK^+$ data at low $J/ψϕ$ invariant masses and the $X(4140)$ and $X(4160)$ resonances

We have studied the $J/ψϕ$ mass distribution of the $B^+\to J/ψϕK^+$ reaction from threshold to about 4250 MeV, and find that one needs the contribution of the $X(4140)$ with a narrow width, together with the $X(4160)$ which accounts for most of the strength of the distribution in that region. The existence of a clear cusp at the $D_s^* \bar{D}_s^*$ threshold indicates that the $X(4160)$ resonance is strongly tied to the $D_s^* \bar{D}_s^*$ channel, which finds a natural interpretation in the molecular picture of this resonance.

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arXiv2017

Study on the reaction of $γp \to f_1(1285) p$ in Regge-effective Lagrangian approach

The production of the $f_1(1285)$ resonance in the reaction of $γp \rightarrow f_1(1285) p$ is investigated within a Regge-effective Lagrangian approach. Besides the contributions of the $t$-channel $ρ$ and $ω$ trajectories exchanges, we also take into account the contributions of $s/u$-channel $N(2300)$ terms, $s/u$-channel nucleon terms, and the contact term. By fitting to the CLAS data, we find that the $s$-channel $N(2300)$ term plays an important role in this reaction. We predict the total cross section for this reaction, and find a clear bump structure around $W=2.3$ GeV, which is associated with the $N(2300)$ state. The reaction of $γp \to f_1(1285) p$ could be useful to further study of the $N(2300)$ experimentally.

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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.

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arXiv2016

Strong decays of the $X(2500)$ newly observed by the BESIII Collaboration

Basing on the observation of a new $J^{PC}=0^{-+}$ state, $X(2500)$, in the partial wave analysis of the decay $J/ψ\rightarrowγX\rightarrow γϕϕ$ performed by the BESIII Collaboration, we have evaluated the strong decays of the $X(2500)$ as the $4^1S_0$ and $5^1S_0$ $s\bar{s}$ states in the $^3P_0$ meson decay model. The predicted total decay width for the $4^1S_0$ $s\bar{s}$ is about 894.5 MeV, and the one for the $5^1S_0$ $s\bar{s}$ is about 271.1 MeV, which is in agreement with the experimental data $Γ_{X(2500)}=230^{+64+56}_{-35-33}$ MeV. By considering the mass and the total strong decay width of the $X(2500)$, we propose that the $X(2500)$ state can be interpreted as a candidate of the $5^1S_0$ $s\bar{s}$ state.

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arXiv2016

Excited bottom and bottom-strange mesons in the quark model

In order to understand the possible $q\bar{q}$ quark-model assignments of the $B_J(5840)$ and $B_J(5960)$ recently reported by the LHCb Collaboration, we evaluate mass spectra, strong decays, and radiative decays of bottom and bottom-strange mesons in a nonrelativistic quark model. Comparing these predictions with the relevant experimental results, we suggest that the $B_J(5840)$ and $B_J(5960)$ can be identified as the $B(2^1S_0)$ and $B(1^3D_3)$, respectively, and the $B(5970)$ reported by the CDF Collaboration can be interpreted as the $B(2^3S_1)$ or $B(1^3D_3)$. Further precise measurements of the width, spin and decay modes of the $B(5970)$ are needed to distinguish these two assignments. These predictions of bottom and bottom-strange mesons can provide useful information to further experimental investigations.

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arXiv2016

A hidden-charm pentaquark state in $Λ^0_b \to J/ψp π^-$ decay

We study here the $Λ_b^0 \to J/ψp π^-$ reaction in analogy to the $Λ^0_b \to J/ψp K^-$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/ψp$ mass distribution around $4450$ MeV, which is associated in the $Λ^0_b \to J/ψp K^-$ experiment to an exotic pentaquark baryonic state, although in $Λ_b^0 \to J/ψp π^-$ it shows up with relatively low statistics. We analyze the $Λ^0_b \to J/ψp π^-$ interaction along the same lines as the $Λ^0_b \to J/ψp K^-$ one, with the main difference stemming from the reduced Cabibbo strength in the former and the consideration of the $π^-p$ final state interaction instead of the $K^-p$ one. We find that with a minimal input, introducing the $π^-p$ and $J/ψp$ interaction in $S$-wave with realistic interactions, and the empirical $P$-wave and $D$-wave contributions, one can accomplish a qualitative description of the $π^-p$ and $J/ψp$ mass distributions. More importantly, the peak structure followed by a dip of the experimental $J/ψp$ mass distribution is reproduced with the same input as used to describe the data of $Λ^0_b\rightarrow J/ψp K^-$ reaction. The repercussion for the triangular singularity mechanism, invoked in some works to explain the pentaquark peak, is discussed.

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arXiv2016

The $Λ_{b}\rightarrow J/ψK^{0}Λ$ reaction and a hidden-charm pentaquark state with strangeness

We study the $Λ_{b}\rightarrow J/ψK^{0}Λ$ reaction considering both the $K^{0}Λ$ interaction with its coupled channels and the $J/ψΛ$ interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to $J/ψΛ$. By using the coupling of the resonance to $J/ψΛ$ from these predictions we show that a neat peak can be observed in the $J/ψΛ$ invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the $J/ψ$ spectrum.

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arXiv2016

Role of $Y(4630)$ in the $p\bar{p}\rightarrowΛ_c\barΛ_c$ reaction near threshold

We investigate the charmed baryon production reaction $p\bar{p}\rightarrowΛ_c\barΛ_c$ in an effective Lagrangian approach. Besides the $t$-channel $D^0$ and $D^{*0}$ mesons exchanges, the $s$-channel $Y(4630)$ meson exchange is taken into account. For the total cross sections, the $D^0$ and $D^{*0}$ mesons provide minor background contributions, while the $Y(4630)$ state gives a clear peak structure with the magnitude of 10 $μ$b at center of mass energy 4.63 GeV. Basing on the results, we suggest that the reaction of $p\bar{p}\rightarrowΛ_c\barΛ_c$ can be used to search for the $1^{--}$ charmonium-like $Y(4630)$ state, and our predictions can be tested in future by the $\rm{\bar PANDA}$ facility.

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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.

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arXiv2016

$χ_{c0}(1P)$ decay into $\barΣ~Σπ$ in search of an $I=1$, $1/2^-$ baryon state around $\bar K N$ threshold

We present the theoretical study of the process $χ_{c0}(1P)\to\barΣΣπ$ decay, by taking into account the $πΣ$ and $π\barΣ$ final state interactions of the final meson-baryon pair based on the chiral unitary approach. We show that the process filters the isospin $I=1$ in the $πΣ$ channel and offers a reaction to test the existence of an $I=1$ state with strangeness $S=-1$ and spin-parity $J^p=1/2^-$ around the $\bar KN$ threshold predicted by some theories and supported by some experiments.

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arXiv2015

Baryon resonances in the strangeness production

We have studied the $N^*(2120)$, $Δ^*(1940)$, and the possible $Σ^*(1380)$ resonances in the $γp \to K^+ Λ(1520)$, $pp \to n K^+ Σ(1385)$, and $Λp \to Λp π^0$ reactions within the resonance model and the effective Lagrangian approach. It is shown that when the contributions from these baryonic states were considered, the current experimental measurement could be well reproduced. In addition, we also demonstrate that the angular distributions provide direct information of these reactions, which could be useful for the investigation of those states and may be tested by future experiments.

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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.

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arXiv2014

Role of the $Δ^*(1940)$ in the $π^+ p \to K^+ Σ^+(1385)$ and $pp \to n K^+ Σ^+(1385)$ reactions

The $p p \to n K^+ Σ^+(1385)$ reaction is a very good isospin $3/2$ filter for studying $Δ^{++*}$ resonance decaying to $K^+Σ^+(1385)$. Within the effective Lagrangian method, we investigate the $Σ(1385)$ (spin-parity $J^P = 3/2^+$) hadronic production in the $π^+ p \to K^+ Σ^+(1385)$ and $p p \to n K^+ Σ^+(1385)$ reactions. For $π^+ p \to K^+ Σ^+(1385)$ reaction, in addition to the "background" contributions from $t$-channel $K^{*0}$ exchange, $u$-channel $Λ(1115)$ and $Σ^0(1193)$ exchange, we also consider the contribution from the $s$-channel $Δ^*(1940)$ resonance, which has significant coupling to $KΣ(1385)$ channel. We show that the inclusion of the $Δ^*(1940)$ resonance leads to a fairly good description of the low energy experimental total cross section data of $π^+ p \to K^+ Σ^+(1385)$ reaction. Basing on the study of $π^+ p \to K^+Σ^+(1385)$ reaction and with the assumption that the excitation of $Δ^*(1940)$ resonance dominant the $pp \to n K^+ Σ^+(1385)$ reaction, we calculate the total and differential cross sections of $p p \to n K^+ Σ^+(1385)$ reaction. It is shown that the new experimental data support the important role played by the $Δ^*(1940)$ resonance with a mass in the region of $1940$ MeV and a width of around $200$ MeV. We also demonstrate that the invariant mass distribution and the Dalitz Plot provide direct information of the $Σ^+(1385)$ production, which can be tested by future experiments.

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arXiv2014

Regge signatures from forward CLAS $Λ(1520)$ photoproduction data

The $γp \to K^+ Λ(1520)$ reaction mechanism is investigated within a Regge--effective Lagrangian hybrid approach based on our previous study of this reaction [Physical Review C89, 015203 (2014)]. Near threshold and for large $K^+$ angles, both the CLAS and LEPS data can be successfully described by considering the contributions from the contact, $t$-channel $\bar K$ exchange, $u$-channel $Λ(1115)$ hyperon pole, and the $s$-channel nucleon pole and $N^*(2120)$ resonance contributions. However, for higher energies and forward $K^+$ angles, systematic discrepancies with data appear, which hint the possible existence of sizable quark-gluon string mechanism effects. We show how the inclusion of a $\bar K$ Regge--trajectory exchange in the $t$-channel leads to an efficient description of the $Λ(1520)$ photoproduction channel over the whole energy and angular ranges accessible in the CLAS experiment.

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arXiv2014

Re-analysis of the $Λ(1520)$ photoproduction reaction

Based on previous studies that support the important role of the $N^*(2120) D_{13}$ resonance in the $γp \to K^+ Λ(1520)$ reaction, we make a re-analysis of this $Λ(1520)$ photoproduction reaction taking into account the recent CLAS differential cross-section data. In addition to the contact, $t-$channel $\bar K$ exchange, $s-$channel nucleon pole and $N^*(2120)$ [previously called $N^*(2080)$] resonance contributions, which have been already considered in previous works, we also study the $u-$channel $Λ(1115)$ hyperon pole term. The latter mechanism has always been ignored in all theoretical analysis, which has mostly relied on the very forward $K^+$ angular LEPS data. It is shown that when the contributions from the $N^*(2120)$ resonance and the $Λ(1115)$ hyperon are taken into account, both the new CLAS and the previous LEPS data can be simultaneously described. We also show that the contribution from the $u-$channel $Λ(1115)$ pole term produces an enhancement for large $K^+$ angles, and it becomes more and more relevant as the photon energy increases, being essential to describe the CLAS differential cross sections at backward angles. Furthermore, we find that the new CLAS data also favor the existence of the $N^*(2120)$ resonance, and that these measurements can be used to further constrain its properties.

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arXiv2013

The role of $N^*(2120)$ nucleon resonance in $KΛ(1520)$ photon and hadronic productions

The associate $KΛ(1520)$ photon and hadronic production in the $γp \to K^+Λ(1520)$, $p p \to p K^+ Λ(1520)$ and $π^- p \to K^0 Λ(1520)$ reactions are investigated within the effective Lagrangian approach and the isobar model. We are interested in the contribution from the $N^*(2120)$ (previously called $N^*(2080)$) resonance, which has a significant coupling to the $KΛ(1520)$ channel. The theoretical results show that the current experimental data for the $γp \to K^+Λ(1520)$ reaction favor the existence of the $N^*(2120)$ resonance, and that these measurements can be used to further constrain its properties. We present results, including the $N^*(2120)$ contribution, for total cross sections of the $γp \to K^+Λ(1520)$, $π^- p \to K^0 Λ(1520)$, and $p p \to p K^+ Λ(1520)$ reactions. For this latter one, we also calculate invariant mass and Dalitz plot distributions.

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arXiv2013

Low-lying even parity meson resonances and spin-flavor symmetry revisited

We review and extend the model derived in Phys. Rev. D83 016007 (2011) to address the dynamics of the low-lying even parity meson resonances. This model is based on a coupled channels spin-flavor extension of the chiral Weinberg-Tomozawa Lagrangian. This interaction is then used to study the S-wave meson-meson scattering involving members not only of the π-octet, but also of the ρ-nonet. In this work, we study in detail the structure of the SU(6) symmetry breaking contact terms that respect (or softly break) chiral symmetry. We derive the most general local (without involving derivatives) terms consistent with the chiral symmetry breaking pattern of QCD. After introducing sensible simplifications to reduce the large number of possible operators, we carry out a phenomenological discussion of the effects of these terms. We show how the inclusion of these pieces leads to an improvement of the description of J^P = 2^+ sector, without spoiling the main features of the predictions obtained in the original model in the J^P = 0^+ and J^P = 1^+ sectors. In particular, we find a significantly better description of the I^G(J^{PC})=0^+(2^{++}), 1^-(2^{++}) and the I(J^{P})=\frac{1}{2}(2^{+}) sectors, which correspond to the f_2(1270), a_2(1320) and K^*_2(1430) quantum numbers, respectively.

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arXiv2009

Canonical interpretation of the $η_2(1870)$

We argue that the mass, production, total decay width, and decay pattern of the $η_2(1870)$ do not appear to contradict with the picture of it being the conventional $2 ^1D_2$ $q\bar{q}$ state. The possibility of the $η_2(1870)$ being a mixture of the conventional $q\bar{q}$ and the hybrid is also discussed.

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