arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 613 records · Page 34Linked to original sources

arXiv2010

Long-distant contribution and $χ_{c1}$ radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for $χ_{c1}\to γV$ ($V=ρ^0,\,ω,\,ϕ$) stimulates our interest in exploring extra mechanism of $χ_{c1}$ decay. In this work, we apply an important non-perturbative QCD effect, i.e., hadronic loop mechanism, to study $χ_{c1}\to γV$ radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of $χ_{c1}\to γV$ are consistent with the corresponding CLEO data of $χ_{c1}\to γV$. We expect further experimental measurement of $χ_{c1}\to γV$ at BES-III, which will be helpful to test the hadronic loop effect on $χ_{c1}$ decay.

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arXiv2010

$B^{()}\bar B^{()}$ intermediate state contribution to $Υ(4S,5S)\to η_b+γ$ radiative decay

In this work, we investigate the re-scattering effects in the radiative decay $Υ(5S)\toη_b+γ$, which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios $B(Υ(5S)\to Υ(1S)+ππ)$ and $B(Υ(5S)\to Υ(1S)+η)$. Our calculations show that the re-scattering effects may enhance $Γ(Υ(10860)\to η_b+γ)$ by four orders, but the tetraquark structure does not. Recently the BaBar and CLEO collaborations have measured the mass of ${η_b}$ and the branching ratios $\mathcal{B}(Υ(2S)\rightarrowη_b+γ)$, $\mathcal{B}(Υ(3S)\rightarrowη_b+γ)$. We hope that very soon, $Υ(10860)\to η_b+γ$ will be measured and it would be an ideal opportunity for testing whether the re-scattering or the tetraquark structure is responsible for the anomaly of $\mathcal{B}\big(Υ(5S)\rightarrowΥ(nS)π^+π^- (n=1,2,3)\big)$, $i.e.$, the future measurements on the radiative decays of $Υ(5S)$ might be a touchstone of the two mechanisms.

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arXiv2010

$D\bar{D}$ production and their interactions

S and P wave $D\bar{D}$ scatterings are studied in a meson exchange model with the coupling constants obtained in the heavy quark effective theory. With the extracted P wave phase shifts and the separable potential approximation, we include the $D\bar{D}$ rescattering effect and investigate the production process $e^+e^-\to D\bar{D}$. We find that it is difficult to explain the anomalous line shape observed by the BES collaboration with this mechanism. Combining our model calculation and the experimental measurement, we estimate the upper limit of the nearly universal cutoff parameter to be 1.7 GeV. With this number, the upper limits of the binding energies of the S wave $D\bar{D}$ and $B\bar{B}$ bound states are obtained. Assuming that the S wave and P wave interactions rely on the same cutoff, our study provides a way of extracting the information about S wave molecular bound states from the P wave meson pair production.

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arXiv2010

Re-Study on the wave functions of $Υ(nS)$ states in LFQM and the radiative decays of $Υ(nS)\to η_b+γ$

The Light-front quark model (LFQM) has been applied to calculate the transition matrix elements of heavy hadron decays. However, it is noted that using the traditional wave functions of the LFQM given in literature, the theoretically determined decay constants of the $Υ(nS)$ obviously contradict to the data. It implies that the wave functions must be modified. Keeping the orthogonality among the $nS$ states and fitting their decay constants we obtain a series of the wave functions for $Υ(nS)$. Based on these wave functions and by analogy to the hydrogen atom, we suggest a modified analytical form for the $Υ(nS)$ wave functions. By use of the modified wave functions, the obtained decay constants are close to the experimental data. Then we calculate the rates of radiative decays of $Υ(nS)\to η_b+γ$. Our predictions are consistent with the experimental data on decays $Υ(3S)\to η_b+γ$ within the theoretical and experimental errors.

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arXiv2010

Possible heavy molecular states composed of a pair of excited charm-strange mesons

The P-wave charm-strange mesons $D_{s0}(2317)$ and $D_{s1}(2460)$ lie below the $DK$ and $D^\ast K$ threshold respectively. They are extremely narrow because their strong decays violate the isospin symmetry. We study the possible heavy molecular states composed of a pair of excited charm strange mesons. As a byproduct, we also present the numerical results for the bottonium-like analogue.

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arXiv2010

The molecular systems composed of the charmed mesons in the $H\bar{S}+h.c.$ doublet

We study the possible heavy molecular states composed of a pair of charm mesons in the H and S doublets. Since the P-wave charm-strange mesons $D_{s0}(2317)$ and $D_{s1}(2460)$ are extremely narrow, the future experimental observation of the possible heavy molecular states composed of $D_s/D_s^\ast$ and $D_{s0}(2317)/D_{s1}(2460)$ may be feasible if they really exist. Especially the possible $J^{PC}=1^{--}$ states may be searched for via the initial state radiation technique.

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arXiv2010

Understanding the branching ratios of χ_{c1}\toϕϕ, ωω, ωϕobserved at BES-III

In this work, we discuss the contribution of the mesonic loops to the decay rates of $χ_{c1}\to ϕϕ,\,ωω$ which are suppressed by the helicity selection rules and $χ_{c1}\to ϕω$ which is a double-OZI forbidden process. We find that the mesonic loop effects naturally explain the clear signals of $χ_{c1}\to ϕϕ,\,ωω$ decay modes observed by the BES collaboration. Moreover, we investigate the effects of the $ω-ϕ$ mixing which may result in the order of magnitude of the branching ratio $BR(χ_{c1} \to ωϕ)$ being $10^{-7}$. Thus, we are waiting for the accurate measurements of the $BR(χ_{c1} \to ωω)$, $BR(χ_{c1} \to ϕϕ)$ and $BR(χ_{c1} \to ωϕ)$, which may be very helpful for testing the long-distant contribution and the $ω-ϕ$ mixing in $χ_{c1}\toϕϕ,\,ωω,\,ωϕ$ decays.

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arXiv2010

X(3915) and X(4350) as new members in P-wave charmonium family

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly support to explain the newly observed X(3915) and X(4350) as new members in P-wave charmonium family, i.e., $χ_{c0}^\prime$ for X(3915) and $χ_{c2}^{\prime\prime}$ for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the $J^{PC}$ quantum numbers of X(3915) and X(4350) must be $0^{++}$ and $2^{++}$ respectively, which provide the important criterion to test P-wave charmonium explanation for X(3915) and X(4350) proposed by this letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and experimental search for them is suggested.

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arXiv2010

Study on the radiative decays of $Υ(nS)\to η_b+γ$

In this work, we investigate the characteristics of the spin-singlet state $η_b$ of the bottomonia family via the radiative decays of $Υ(nS)\to η_b+γ$. The theoretical estimation of the decay widths is carried out in terms of the light-front quark model (LFQM). Recently CLEO and BaBar collaborations have measured $\mathcal{B}(Υ(3S)\toγη_b)$ and the mass of ${η_b}$. In terms of the data we fix the concerned input parameters in our calculations of $Υ(nS)\to η_b+γ$. A special attention is paid on the transition of $Υ(5S)\to η_b+γ$. The BELLE data showed that the width of $Υ(5S)\to Υ(2S,1S)+ππ$ is two orders larger than that of $Υ(4S)\to Υ(2S,1S)+ππ$, thus some theoretical explanations have been proposed. Among them, it is suggested the inelastic final state interaction (IFSI) $Υ(5S)\to B\bar B\to Υ(1S)+ππ$ may be a natural one. If so, a similar mechanism also applies to $Υ(5S)\to B^{(*)}\bar B^{(*)}\to η_b+γ$, the precise measurement would serve as a good test whether $Υ(5S)$ possess exotic components. Our calculation in the LFQM indicates that the rate of the direct process $Υ(5S)\toη_b+γ$ is not anomalous compared to $Υ(mS)\toη_b+γ(m=1,2,3,4)$, thus if the IFSI does apply, the rate of $Υ(5S)\toη_b+γ$ should be larger than the others by orders.

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arXiv2009

Discovery potential for charmonium-like state Y(3940) by the meson photoproduction

In this work, we investigate the discovery potential for Y(3940) by the photoproduction process $γp\to Y(3940)p$. The numerical result shows that the upper (lower) limit of the total cross section for $γp\to Y(3940)p$ is up to the order of 1 $nb$ (0.1 $μb$). Additionally, the background analysis and the Dalitz plot relevant to the production of Y(3940) are studied. The Dalitz plot analysis of Y(3940) production indicates that Y(3940) signal can be distinguished from the background clearly. The lower limit of the number of events of Y(3940) reaches up to 10/0.02GeV$^2$ for one billion collisions of $γp$ by studying the invariant mass spectrum of $J/ψω$. Experimental search for Y(3940) by the meson photoproduction is suggested.

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arXiv2009

Newly observed D_{sJ}(3040) and the radial excitations of P-wave charmed-strange mesons

Inspired by the newly observed $D_{sJ}(3040)^+$ state, in this work we systemically study the two-body strong decays of P-wave charmed-strange mesons with the first radial excitation. Under the assignment of $1^{+}(j^P=1/2^+)$, i.e. the first radial excitation of $D_{s1}(2460)^+$, we find that the width of $D_{sJ}(3040)^+$ is close to the lower limit of the BaBar measurement. This indicates that it is reasonable to interpret $D_{sJ}(3040)^+$ as the first radial excitation of $D_{s1}(2460)^+$. Our calculation further predicts that $0^-+1^-$ channels e.g. $D^+K^{*0}$, $D^0 K^{*+}$ and $D_s^+ϕ$ are important for the search for $D_{sJ}(3040)^+$. To help future experiments finding the remaining three P-wave charmed-strange mesons with the first radial excitation, we present the predictions for the strong decays of these three P-wave charmed-strange mesons.

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arXiv2009

The hidden charm decay of Y(4140) by the rescattering mechanism

Assuming that Y(4140) is the second radial excitation of the P-wave charmonium $χ_{cJ}^{\prime\prime}$ ($J=0, 1$), the hidden charm decay mode of Y(4140) is calculated in terms of the rescattering mechanism. Our numerical results show that the upper limit of the branching ratio of the hidden charm decay $Y(4140)\to J/ψϕ$ is on the order of $10^{-4}\sim 10^{-3}$ for both of the charmonium assumptions for Y(4140), which disfavors the large hidden charm decay pattern indicated by the CDF experiment. It seems to reveal that the pure second radial excitation of the P-wave charmonium $χ_{cJ}^{\prime\prime}$ ($J=0, 1$) is problematic.

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arXiv2009

The line shape of the radiative open-charm decay of Y(4140) and Y(3930)

In this work, we study the radiative open-charm decays $Y(4140)\to {D}_s^{\ast+} D_s^- γ$ and $Y(3930)\to{D}^{\ast+} D^-γ$ under the assignments of $D_{s}^*\bar{D}_s^*$ and $D^*\bar{D}^*$ as molecular states for Y(4140) and Y(3930) respectively. Based on our numerical result, we propose the experimental measurement of the photon spectrum of $Y(4140)\to {D}_s^{\ast+} D_s^- γ, D_{s}^+D_{s}^{*-}γ$ and $Y(3930)\to D^{*0}\bar{D}^0γ, D^{0}\bar{D}^{*0}γ, D^{*+}D^-γ, D^+D^{*-}γ$ can further test the molecular assignment for Y(4140) and Y(3930).

hep-ph↗

arXiv2009

Towards the decays of $\bar{N}_X(1625)$ in the molecular picture

In this talk, we firstly overview the experimental status of $\bar{N}_X(1625)$, which is an enhancement structure observed in $K^{-}\barΛ$ invariant mass spectrum of $J/ψ\to pK^{-}\barΛ$ process. Then we present the result of the decay of $\bar{N}_X(1625)$ under the two molecular assumptions, i.e. S-wave $\barΛK^-$ and S-wave $\barΣ^0K^-$ molecular states. Several experimental suggestions for $\bar{N}_X(1625)$ are proposed.

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arXiv2009

Light Pseudoscalar Meson and Heavy Meson Scattering Lengths

We have performed a systematical calculation of the pion ($π, K, η$) and heavy pseudoscalar meson S-wave scattering lengths up to ${\cal O}(p^3)$ in the chiral perturbation theory in the heavy quark symmetry limit. With the three scattering lengths from the lattice simulations as input we estimate the unknown low-energy constants. Then we predict all the other unmeasured scattering lengths. The analytical expressions and predictions may be helpful to future investigations. Especially we note that the DK scattering length is positive. Therefore their interaction is attractive, which helps to lower the mass of the "bare" charm-strange scalar state in the quark model through the couple-channel effect.

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arXiv2009

The puzzle of excessive non-$D\bar D$ component of the inclusive $ψ(3770)$ decay and the long-distant contribution

In this letter we suggest that the obvious discrepancy between theoretical prediction on the $\mathrm{non}-D\bar D$ decays of $ψ(3770)$ and data is to be alleviated by taking final state interaction (FSI) into account. By assuming that $ψ(3770)$ overwhelmingly dissociates into $D\bar D$, then the final state interaction induces a secondary process, we calculate the branching ratios of $ψ(3770)\to D\bar D\to J/ψη, ρπ, ωη, K^*K$. Our results show that the branching ratio of $ψ(3770)\to \mathrm{non}-D\bar{D}$ can reach up to $\mathcal{B}_{\mathrm{non}-D\bar{D}}^{FSI}=(0.2\sim1.1)%$ while typical parameters $I=0.4$ GeV$^{-2}$ and $α=0.8\sim 1.3$ are adopted. This indicates that the FSI is obviously non-negligible.

hep-ph↗

arXiv2009

B_{s1}(5830) and B_{s2}^*(5840)

In this paper we investigate the strong decays of the two newly observed bottom-strange mesons $B_{s1}(5830)$ and $B_{s2}^*(5840)$ in the framework of the quark pair creation model. The two-body strong decay widths of $B_{s1}(5830)^0\to B^{*+}K^-$ and $B_{s2}^*(5840)^0\to B^+K^-, B^{*+}K^-$ are calculated by considering $B_{s1}(5830)$ to be a mixture between $|^1P_1>$ and $|^3P_1>$ states, and $B_{s2}^*(5840)$ to be a $|^3P_2>$ state. The double pion decay of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ is supposed to occur via the intermediate state $σ$ and $f_0(980)$. Although the double pion decay widths of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ are smaller than the two-body strong decay widths of $B_{s1}(5830)$ and $B_{s2}^*(5840)$, one suggests future experiments to search the double pion decays of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ due to their sizable decay widths.

hep-ph↗

arXiv2009

Y(4143) is probably a molecular partner of Y(3930)

After discussing the various possible interpretations of the Y(4143) signal observed by the CDF collaboration in the $J/ψϕ$ mode, we tend to conclude that Y(4143) is probably a $D_s^\ast {\bar D}_s^\ast$ molecular state with $J^{PC}=0^{++}$ or $2^{++}$ while Y(3930) is its $D^\ast {\bar D}^\ast$ molecular partner as predicted in our previous work (arXiv:0808.0073). Both the hidden-charm and open charm two-body decays occur through the rescattering of the vector components within the molecular states while the three- and four-body open charm decay modes are forbidden kinematically. Hence their widths are narrow naturally. CDF, Babar and Belle collaborations may have discovered heavy molecular states already. We urge experimentalists to measure their quantum numbers and explore their radiative decay modes in the future.

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