arXiv subjects

C. W. Xiao

Publications and source records attributed to C. W. Xiao.

At least 37 records · Page 2Linked to original sources

arXiv2019

Prediction of hidden charm strange molecular baryon states with heavy quark spin symmetry

We have studied the meson-baryon $S-$wave interaction, using coupled channels, in the isoscalar hidden-charm strange sector and $J^P = 1/2^-,3/2^-$ and $5/2^-$. We impose constraints of heavy quark spin symmetry in the interaction and obtain the non vanishing matrix elements from an extension of the local hidden gauge approach to the charm sector. The ultraviolet divergences are renormalized using the same meson-baryon-loops regulator previously employed in the non-strange hidden charm sector, where a good reproduction of the properties of the newly discovered pentaquark states is obtained. We obtain five states of $1/2^-$, four of $3/2^-$ and one of $5/2^-$, which could be compared in the near future with forthcoming LHCb experiments. The $5/2^-$, three of the $3/2^-$ and another three of the $1/2^-$ resonances are originated from isoscalar $\bar D^{(*)}Ξ_c^\prime$ and $\bar D^{(*)}Ξ_c^*$ interactions. They should be located just few MeV below the corresponding thresholds (4446, 4513, 4588 and 4655 MeV), and would be SU(3)-siblings of the isospin 1/2 $\bar D^{(*)} Σ_c^{(*)}$ quasi-bound states previously found, and that provided a robust theoretical description of the $P_c(4440)$, $P_c(4457)$ and $P_c(4312)$ LHCb exotic states. The another two $1/2^-$ and $3/2^-$ states obtained in this work are result of the $\bar D^{(*)}Ξ_c-D^{(*)}_sΛ_c$ coupled-channels isoscalar interaction, are significantly broader than the others, with widths of the order of 15 MeV, being $\bar D^{(*)}_sΛ_c$ the dominant decay channel.

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arXiv2019

Heavy quark spin symmetric molecular states from ${\bar D}^{()}Σ_c^{()}$ and other coupled channels in the light of the recent LHCb pentaquarks

We consider the ${\bar D}^{(*)}Σ_c^{(*)}$ states, together with $J/ψN$ and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as $1/2^-$ $\bar{D} Σ_c$, $1/2^-$ $\bar{D}^* Σ_c$, and $3/2^-$ $\bar{D}^* Σ_c$, and isospin $I=1/2$. We find another state around 4374 MeV, of $3/2^-$ $\bar{D} Σ_c^*$ structure, for which indications appear in the experimental spectrum. Two other near degenerate states of $1/2^-$ $\bar{D}^* Σ_c^*$ and $3/2^-$ $\bar{D}^* Σ_c^*$ nature are also found around 4520 MeV, which although less clear, are not incompatible with the observed spectrum. In addition, a $5/2^-$ $\bar D^* Σ_c^*$ state at the same energy appears, which however does not couple to $J/ψp$ in $S-$wave, and hence it is not expected to show up in the LHCb experiment.

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arXiv2018

The branching ratio $ω\to π^+π^-$ revisited

We analyze the most recent data for the pion vector form factor in the timelike region, employing a model-independent approach based on dispersion theory. We confirm earlier observations about the inconsistency of different modern high-precision data sets. Excluding the BaBar data, we find an updated value for the isospin-violating branching ratio $\mathcal{B}(ω\to π^+π^-) = (1.46\pm 0.08) \times 10^{-2}$. As a side result, we also extract an improved value for the pion vector or charge radius, $\sqrt{\langle r_V^2\rangle} = 0.6603(5)(4)\text{fm}$, where the first uncertainty is statistical as derived from the fit, while the second estimates the possible size of nonuniversal radiative corrections. In addition, we demonstrate that modern high-quality data for the decay $η' \to π^+π^-γ$ will allow for an even improved determination of the transition strength $ω\toπ^+π^-$.

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arXiv2016

Investigations of the $D$-multi-$ρ$ interactions

In the present work, which aims at searching for bound sates, the interactions of the $D$-multi-$ρ$ systems are investigated by means of the formalism of the fixed-center-approximation to Faddeev equations. Reproducing the states of $f_2 (1270)$ and $D_1 (2420)$ dynamically in the two-body $ρρ$ and $ρD$ interactions, respectively, as the clusters of the fixed center approximation, the state of $D(3000)^0$ is found as a molecule of $D-f_2$ or $ρ-D_1$ structures in the three-body interactions, where we determine its quantum number $J^P = 2^-$ and find another possible state of $D_2 (3100)$ with isospin $I=3/2$. In our results, there are some other predictions with uncertainties, a $D_3 (3160)$ state with $I(J^P) = \frac{1}{2} (3^+)$ in the four-body interactions, a narrow $D_4 (3730)$ state with $I(J^P) = \frac{1}{2} (4^-)$, a wide $D_4 (3410)$ state of $I(J^P) = \frac{1}{2} (4^-)$, and another wide $D_4 (3770)$ state but with $I(J^P) = \frac{3}{2} (4^-)$ in the five-body interactions, and a $D_5 (3570)$ state with $I(J^P) = \frac{1}{2} (5^+)$ in the six-body interactions. Our results are consistent with the findings of quark models.

hep-ph↗

arXiv2016

$J/ψN$ interactions revisited and $Λ_b^0 \to J/ψK^- (π^-) p$ decays

Recently LHCb experiments confirmed the findings of the two $P_c$ states in the $Λ_b^0 \to J/ψp π^-$ decays. In the present work, we investigate both the $Λ_b^0 \to J/ψK^- p$ and the $Λ_b^0 \to J/ψp π^-$ decays, continuing the investigations of our former works on the interactions of $J/ψN$ with its coupled channels by considering the s-/u- channel contributions. We obtain consistent results of the line-shape of the $J/ψN$ invariant mass distribution with the LHCb experiments, and favour the $P_c (4450)$ state as a $\bar{D}^* Σ_c$ bound state with $J=1/2^-$.

hep-ph↗

arXiv2015

Two, three, many body systems involving mesons. Multimeson condensates

In this talk we review results from studies with unconventional many hadron systems containing mesons: systems with two mesons and one baryon, three mesons, some novel systems with two baryons and one meson, and finally systems with many vector mesons, up to six, with their spins aligned forming states of increasing spin. We show that in many cases one has experimental counterparts for the states found, while in some other cases they remain as predictions, which we suggest to be searched in BESIII, Belle, LHCb, FAIR and other facilities.

hep-ph↗

arXiv2015

$J/ψ(η_c) N$ and $Υ(η_b) N$ cross sections

Inspired by the recent findings of the two $P_c^+$ states in the $J/ψp$ mass spectrum at LHCb, we investigate the elastic and inelastic cross sections of the $J/ψN$, $η_c N$, $ΥN$ and $η_b N$ channels within the constraints from heavy quark spin and flavour symmetry. The $\bar{D}^{(*)} Σ_c^{(*)}$ ($B^{(*)} Σ_b^{(*)}$) bound states predicted in earlier works should be accessible in elastic and/or inelastic processes of the $J/ψN$ and/or $η_c N$ ($ΥN$ and/or $η_b N$) interactions.

hep-ph↗

arXiv2015

States generated in the $K$-multi-$ρ$ interactions

In the present work we use three-body interaction formalism to investigate the $K$-multi-$ρ$ interactions. First, we reproduced the resonances $f_2(1270)$ and $K_1(1270)$ in the $ρρ$ and $ρK$ two-body interactions respectively, as the clusters of the fixed center approximation. Then, we study the three-body $K -ρρ(f_2)$ and $ρ- ρK (K_1)$ interactions with the fixed center approximation of the Faddeev equations. Furthermore, we extrapolate the formalism to study the four-body, five-body and six-body systems, containing one $K$ meson and multi-$ρ$ mesons. In our research, without introducing any free parameters, we generate the $K_2 (1770)$ state in the three-body interaction with the mass of 1707 MeV and a width about 113 MeV, which are consistent with the experiments. We also find a clear resonant structure in our results of the five-body interaction, with a mass 2505 MeV and a width about 32 MeV or more, which is associated to the $K_4 (2500)$ state, where we obtain consistent results with the experimental findings. Furthermore, we predict some new states in the other many body interactions, $K_3 (2080)$, $K_5 (2670)$ (isospin $I=1/2$), and $K_4 (2640)$ (isospin $I=3/2$), with uncertainties.

hep-ph↗

arXiv2015

Baryon states with open charm in the extended local hidden gauge approach

In this paper we examine the interaction of $D N$ and $D^* N$ states, together with their coupled channels, by using an extension of the local hidden gauge formalism from the light meson sector, which is based on heavy quark spin symmetry. The scheme is based on the use of the impulse approximation at the quark level, with the heavy quarks acting as spectators, which occurs for the dominant terms where there is the exchange of a light meson. The pion exchange and the Weinberg-Tomozawa interactions are generalized and with this dynamics we look for states generated from the interaction, with a unitary coupled channels approach that mixes the pseudoscalar-baryon and vector-baryon states. We find two states with nearly zero width which are associated to the $Λ_c(2595)$ and $Λ_c(2625)$. The lower state, with $J^P = 1/2^-$, couples to $D N$ and $D^* N$, and the second one, with $J^P = 3/2^-$, to $D^* N$. In addition to these two $Λ_c$ states, we find four more states with $I=0$, one of them nearly degenerate in two states of $J=1/2,\ 3/2$. Furthermore we find three states in $I=1$, two of them degenerate in $J=1/2, 3/2$.

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arXiv2014

Baryon states with open beauty in the extended local hidden gauge approach

In this paper we examine the interaction of \bar B N, \bar B Δ, \bar B^* N and \bar B^* Δstates, together with their coupled channels, using a mapping from the light meson sector. The assumption that the heavy quarks act as spectators at the quark level automatically leads us to the results of the heavy quark spin symmetry for pion exchange and reproduces the results of the Weinberg Tomozawa term, coming from light vector exchanges in the extended local hidden gauge approach. With this dynamics we look for states dynamically generated from the interaction and find two states with nearly zero width, which we associate to the Λ_b(5912) and Λ_b(5920) states. The states couple mostly to \bar B^* N, which are degenerate with the Weinberg Tomozawa interaction. The difference of masses between these two states, with J=1/2, 3/2 respectively, is due to pion exchange connecting these states to intermediate \bar B N states. In addition to these two Λ_b states, we find three more states with I=0, one of them nearly degenerate in two states of J=1/2,3/2. Furthermore we also find eight more states in $I=1$, two of them degenerate in J=1/2, 3/2, and other two degenerate in J=1/2, 3/2, 5/2.

hep-ph↗

arXiv2013

Description of $ρ(1700)$ as a $ρK \bar{K}$ system with the fixed center approximation

We study the $ρK\bar{K}$ system with an aim to describe the $ρ(1700)$ resonance. The chiral unitary approach has achieved success in a description of systems of the light hadron sector. With this method, the $K \bar{K}$ system in the isospin sector $I=0$, is found to be a dominant component of the $f_0 (980)$ resonance. Therefore, by regarding the $K\bar{K}$ system as a cluster, the $f_0 (980)$ resonance, we evaluate the $ρK\bar{K}$ system applying the fixed center approximation to the Faddeev equations. We construct the $ρK$ unitarized amplitude using the chiral unitary approach. As a result, we find a peak in the three-body amplitude around 1739 MeV and a width of about 227 MeV. The effect of the width of $ρ$ and $f_0 (980)$ is also discussed. We associate this peak to the $ρ(1700)$ which has a mass of $1720 \pm 20$ MeV and a width of $250 \pm 100$ MeV.

hep-ph↗

arXiv2013

A study of $ηK \bar K$ and $η' K \bar K$ with the fixed center approximation to Faddeev equations

In the present work we investigate the three-body systems of $ηK \bar K$ and $η' K \bar K$, by taking the fixed center approximation to Faddeev equations. We find a clear and stable resonance structure around 1490 MeV in the squared $ηK \bar K$ scattering amplitude, which is not sensitive to the renormalization parameters. Conversely, we get only an enhancement effect of the threshold in the $η' K \bar K$ amplitude that indicates the difficulty to bind the $η' K \bar K$ system as a consequence of a weaker $η' K$ interaction than the $ηK$ one. We associate the $ηK \bar K$ state found to the $η(1475)$.

hep-ph↗

arXiv2013

Hidden beauty molecules within the local hidden gauge approach and heavy quark spin symmetry

Using a coupled channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-meson interaction with hidden beauty and obtain several new states. Both I=0 and I=1 states are analyzed and it is shown that in the I=1 sector, the interactions are too weak to create any bound states within our framework. In total, we predict with confidence the existence of 6 bound states, and weakly bound 6 more possible states. The existence of these weakly bound states depend on the influence of the coupled channel effects.

hep-ph↗

arXiv2013

Hidden beauty baryon states in the local hidden gauge approach with heavy quark spin symmetry

Using a coupled channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-baryon interaction with hidden beauty and obtain several new states of $N^*$ around 11 GeV. We consider the basis of states $η_b N$, $ΥN$, $B Λ_b$, $B Σ_b$, $B^* Λ_b$, $B^* Σ_b$, $B^* Σ_b^*$ and find four basic bound states which correspond to $B Σ_b$, $B Σ_b^*$, $B^* Σ_b$ and $B^* Σ_b^*$, decaying mostly into $η_b N$ and $ΥN$ and with a binding energy about 50-130 MeV with respect to the thresholds of the corresponding channel. All of them have isospin $I=1/2$, and there are no bound states or resonances in $I=3/2$. The $B Σ_b$ state appears in $J=1/2$, the $B Σ_b^*$ in $J=3/2$, the $B^* Σ_b$ appears nearly degenerate in $J=1/2, ~3/2$ and the $B^* Σ_b^*$ appears nearly degenerate in $J=1/2, ~3/2, ~5/2$. These states have a width from $6 \sim 45 \mev$ except for the one in $J=5/2$ which has zero width since it cannot decay into any of the states of the basis chosen.

hep-ph↗

arXiv2013

Combining heavy quark spin and local hidden gauge symmetries in the dynamical generation of hidden charm baryons

We present a coupled channel unitary approach to obtain states dynamically generated from the meson baryon interaction with hidden charm, using constraints of heavy quark spin symmetry. We use as basis of states, $\bar D B$, $\bar D^* B$ states, with $B$ baryon charmed states belonging to the 20 representations of SU(4) with $J^P=1/2^+,~3/2^+$. In addition we also include the $η_c N$ and $J/ψN$ states. The inclusion of these coupled channels is demanded by heavy quark spin symmetry, since in the large $m_Q$ limit the $D$ and $D^*$ states are degenerate and are obtained from each other by means of a spin rotation, under which QCD is invariant. The novelty in the work is that we use dynamics from the extrapolation of the local hidden gauge model to SU(4) and we show that this dynamics fully respects the constraints of heavy quark spin symmetry. With the full space of states demanded by the heavy quark spin symmetry and the dynamics of the local hidden gauge we look for states dynamically generated and find four basic states which are bound, corresponding to $\bar D Σ_c$, $\bar D Σ_c^*$, $\bar D^* Σ_c$ and $\bar D^* Σ_c^*$, decaying mostly into $η_c N$ and $J/ψN$. All the states appear in isospin $I=1/2$ and we find no bound states or resonances in $I=3/2$. The $\bar D Σ_c$ state appears in $J=1/2$, the $\bar D Σ_c^*$ in $J=3/2$, the $\bar D^* Σ_c$ appears nearly degenerate in $J=1/2, ~3/2$ and the $\bar D^* Σ_c^*$ appears nearly degenerate in $J=1/2, ~3/2, ~5/2$, with the peculiarity that in $J=5/2$ the state has zero width in the space of states chosen. All the states are bound with about 50 MeV with respect to the corresponding $\bar D B$ thresholds and the width, except for the $J=5/2$ state, is also of the same order of magnitude.

hep-ph↗

arXiv2012

Three methods to detect the predicted $D \bar{D}$ scalar meson X(3700)

In analogy to the f_0(500), which appears as a $ππ$ resonance in chiral unitary theory, and the f_0(980), which appears as a quasibound $K \bar K$ state, the extension of this approach to the charm sector also predicts a quasibound $D \bar D $ state with mass around 3720 MeV, named as X(3700), for which some experimental support is seen in the $e^+ e^- \to J/ψD \bar D $ reaction close to the $D \bar D $ threshold. In the present work we propose three different experiments to observe it as a clear peak. The first one is the radiative decay of the $ψ(3770)$, $ψ(3770) \to γX(3700) \to γηη'$. The second one proposes the analogous reaction $ψ(4040) \to γX(3700) \to γηη'$ and the third reaction is the $e^+ e^- \to J/ψX(3700) \to J/ψηη'$. Neat peaks are predicted for all the reactions and the calculated rates are found within measurable range in present facilities.

hep-ph↗

arXiv2012

The small $K π$ component in the $K^*$ wave functions

We use a recently developed formalism which generalizes the Weinberg's compositeness condition to partial waves higher than s-wave in order to determine the probability of having a $K π$ component in the $K^*$ wave function. A fit is made to the $K π$ phase shifts in p-wave, from where the coupling of $K^*$ to $K π$ and the $K π$ loop function are determined. These ingredients allow us to determine that the $K^*$ is a genuine state, different to a $K π$ component, in a proportion of about 80%.

hep-ph↗

arXiv2012

Interaction of vector mesons with baryons and nuclei

After some short introductory remarks on particular issues on the vector mesons in nuclei, in this paper we present a short review of recent developments concerning the interaction of vector mesons with baryons and with nuclei from a modern perspective using the local hidden gauge formalism for the interaction of vector mesons. We present results for the vector baryon interaction and in particular for the resonances which appear as composite states, dynamically generated from the interaction of vector mesons with baryons, taking also the mixing of these states with pseudoscalars and baryons into account. We then venture into the charm sector, reporting on hidden charm baryon states around 4400 MeV, generated from the interaction of vector mesons and baryons with charm, which have a strong repercussion on the properties of the $J/ΨN$ interaction. We also address the interaction of $K^*$ with nuclei and make suggestions to measure the predicted huge width in the medium by means of the transparency ratio. The formalism is extended to study the phenomenon of $J/ψ$ suppression in nuclei via $J/ψ$ photoproduction reactions.

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