arXiv subjects

Shi-Lin Zhu

Publications and source records attributed to Shi-Lin Zhu.

At least 217 records · Page 12Linked to original sources

arXiv2013

The meson-exchange model for the $Λ\barΛ$ interaction

In the present work, we apply the one-boson-exchange potential (OBEP) model to investigate the possibility of Y(2175) and $η(2225)$ as bound states of $Λ\barΛ(^3S_1)$ and $Λ\barΛ(^1S_0)$ respectively. We consider the effective potential from the pseudoscalar $η$-exchange and $η^{'}$-exchange, the scalar $σ$-exchange, and the vector $ω$-exchange and $ϕ$-exchange. The $η$ and $η^{'}$ meson exchange potential is repulsive force for the state $^1S_0$ and attractive for $^3S_1$. The results depend very sensitively on the cutoff parameter of the $ω$-exchange ($Λ_ω$) and least sensitively on that of the $ϕ$-exchange ($Λ_ϕ$). Our result suggests the possible interpretation of Y(2175) and $η(2225)$ as the bound states of $Λ\barΛ(^3S_1)$ and $Λ\barΛ(^1S_0)$ respectively.

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arXiv2013

Exotic $QQ\bar{q}\bar{q}$, $QQ\bar{q}\bar{s}$ and $QQ\bar{s}\bar{s}$ states

After constructing the possible $J^P=0^-, 0^+, 1^-$ and $1^+$ $QQ\bar{q}\bar{q}$ tetraquark interpolating currents in a systematic way, we investigate the two-point correlation functions and extract the corresponding masses with the QCD sum rule approach. We study the $QQ\bar{q}\bar{q}$, $QQ\bar{q}\bar{s}$ and $QQ\bar{s}\bar{s}$ systems with various isospins $I=0, 1/2, 1$. Our numerical analysis indicates that the masses of doubly-bottomed tetraquark states are below the threshold of the two bottom mesons, two bottom baryons and one doubly bottomed baryon plus one anti-nucleon. Very probably these doubly-bottomed tetraquark states are stable.

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arXiv2012

Pseudoscalar Goldstone Bosons Scattering off Charmed Baryons with Chiral Perturbation Theory

We have systematically calculated the pseudoscalar Goldstone boson and charmed baryon scattering lengths to the third order with heavy baryon chiral perturbation theory. The scattering lengths can reveal the interaction of $K Λ_c$, $K Σ_c$, $πΩ_c$ etc. For each channel, we take into account of the interaction between the external particle and every possible charmed baryon in the triplet, sextet, and excited sextet. We use dimensional regularization and modified minimal subtraction to get rid of the divergences in the loop-diagram corrections. We notice that the convergence of chiral expansion for most of the channels becomes better after we let the low energy constants absorb the analytic contributions of the loop-diagram corrections and keep the nonanalytic terms only.

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arXiv2012

Isospin breaking, coupled-channel effects, and X(3872)

We re-investigate the possibility of X(3872) as a $D\bar{D}^*$ molecule with $J^{PC}=1^{++}$ within the framework of both the one-pion-exchange (OPE) model and the one-boson-exchange (OBE) model. After careful treatment of the S-D wave mixing, the mass difference between the neutral and charged $D(D^*)$ mesons and the coupling of the $D(D^*)$ pair to $D^*\bar{D}^*$, a loosely bound molecular state X(3872) emerges quite naturally with large isospin violation in its flavor wave function. For example, the isovector component is 26.24% if the binding energy is 0.30 MeV, where the isospin breaking effect is amplified by the tiny binding energy. After taking into account the phase space difference and assuming the $3π$ and $2π$ come from a virtual omega and rho meson respectively, we obtain the ratio of these two hidden-charm decay modes: $\mathcal{B}(X(3872)\rightarrow π^+π^-π^0 J/ψ)/\mathcal{B}(X(3872)\rightarrow π^+π^- J/ψ)=0.42$ for the binding energy being 0.3 MeV, which is consistent with the experimental value.

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arXiv2012

Spin-1 charmonium-like states in QCD sum rule

We study the possible spin-1 charmonium-like states by using QCD sum rule approach. We calculate the two-point correlation functions for all the local form tetraquark interpolating currents with $J^{PC}=1^{--}, 1^{-+}, 1^{++}$ and $1^{+-}$ and extract the masses of the tetraquark charmonium-like states. The mass of the $1^{--}$ $qc\bar q\bar c$ state is $4.6\sim4.7$ GeV, which implies a possible tetraquark interpretation for Y(4660) meson. The masses for both the $1^{++}$ $qc\bar q\bar c$ and $sc\bar s\bar c$ states are $4.0\sim 4.2$ GeV, which is slightly above the mass of X(3872). For the $1^{-+}$ and $1^{+-}$ $qc\bar q\bar c$ states, the extracted masses are $4.5\sim4.7$ GeV and $4.0\sim 4.2$ GeV respectively.

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arXiv2012

Few-Body Systems Composed of Heavy Quarks

Within the past ten years many new hadrons states were observed experimentally, some of which do not fit into the conventional quark model. I will talk about the few-body systems composed of heavy quarks, including the charmonium-like states and some loosely bound states.

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arXiv2012

Hadronic Molecular States Composed of Heavy Flavor Baryons

We investigate the possible molecules composed of two heavy flavor baryons such as "$A_QB_Q$"(Q=b, c) within the one-pion-exchange model (OPE). Our results indicate that the long-range $π$ exchange force is strong enough to form molecules such as $[Σ_QΞ_Q^{'}]^{I=1/2}_{S=1}$(Q=b, c), $[Σ_QΛ_Q]^{I=1}_{S=1}$(Q=b, c), $[Σ_bΞ_b^{'}]^{I=3/2}_{S=1}$ and $[Ξ_bΞ^{'}_b]^{I=0}_{S=1}$ where the S-D mixing plays an important role. In contrast, the $π$ exchange does not form the spin-singlet $A_QB_Q$ bound states. If we consider the heavier scalar and vector meson exchanges as well as the pion exchange, some loosely bound spin-singlet S-wave states appear while results of the spin-triplet $A_QB_Q$ system does not change significantly, which implies the pion exchange plays an dominant role in forming the spin-triplet molecules. Moreover, we perform an extensive coupled channel analysis of the $Λ_QΛ_Q$ system within the OPE and one-boson-exchange (OBE) framework and find that there exist loosely bound states of $Λ_QΛ_Q$(Q=b,c) with quantum numbers $I(J^P)=0(0^+)$, $0(0^-)$ and $0(1^-)$. The binding solutions of $Λ_QΛ_Q$ system mainly come from the coupled-channel effect in the flavor space. Besides the OPE force, the medium- and short-range attractive force also plays a significant role in the formation of the loosely bound $Λ_cΛ_c$ and $Λ_bΛ_b$ states. Once produced, they will be very stable because such a system decays via weak interaction with a very long lifetime around $10^{-13}\sim10^{-12}$s.

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arXiv2012

Hadronic molecules with both open charm and bottom

With the one-boson-exchange model, we study the interaction between the S-wave $D^{(*)}/D^{(*)}_s$ meson and S-wave $B^{(*)}/B^{(*)}_s$ meson considering the S-D mixing effect. Our calculation indicates that there may exist the $B_c$-like molecular states. We estimate their masses and list the possible decay modes of these $B_c$-like molecular states, which may be useful to the future experimental search.

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arXiv2012

Possible $J^{PC} = 0^{+-}$ Exotic State

We study the possible exotic states with $J^{PC} = 0^{+-}$ using the tetraquark interpolating currents with the QCD sum rule approach. The extracted masses are around 4.85 GeV for the charmonium-like states and 11.25 GeV for the bottomomium-like states. There is no working region for the light tetraquark currents, which implies the light $0^{+-}$ state may not exist below 2 GeV.

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arXiv2011

The possible hidden-charm molecular baryons composed of anti-charmed meson and charmed baryon

With the one-boson-exchange model we have studied the possible existence of the very loosely bound hidden-charm molecular baryons composed of anti-charmed meson and charmed baryon. Our numerical results indicate that there exist $Σ_c\bar{D}^*$ states with $I(J^P)=1/2(1/2^-), 1/2(3/2^-), 3/2(1/2^-), 3/2(3/2^-)$ and $Σ_c\bar{D}$ state with $3/2(1/2^-)$. But the $Λ_c \bar{D}$ and $Λ_c \bar{D}^*$ molecular states do not exist.

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arXiv2011

Charged bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$ and the $Υ(5S)\to Υ(2S)π^+π^-$ decay

Inspired by the newly observed two charged bottomonium-like states, we consider the possible contribution from the intermediate $Z_b(10610)$ and $Z_b(10650)$ states to the $Υ(5S)\to Υ(2S)π^+π^-$ decay process, which naturally explains Belle's previous observation of the anomalous $Υ(2S)π^+π^-$ production near the peak of $Υ(5S)$ at $\sqrt s=10.87$ GeV [K.F. Chen {\it et al}. (Belle Collaboration), Phys. Rev. Lett. {\bf 100}, 112001 (2008)]. The resulting $dΓ(Υ(5S)\to Υ(2S)π^+π^-)/dm_{π^+π^-}$ and $dΓ(Υ(5S)\to Υ(2S)π^+π^-)/d\cosθ$ distributions agree with Belle's measurement after inclusion of these $Z_b$ states. This formalism also reproduces the Belle observation of the double-peak structure and its reflection in $Υ(2S)π^+$ invariant mass spectrum of $Υ(5S)\to Υ(2S)π^+π^-$ decay.

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arXiv2011

The Pseudoscalar Meson and Heavy Vector Meson Scattering Lengths

We have systematically studied the S-wave pseudoscalar meson and heavy vector meson scattering lengths to the third order with the chiral perturbation theory, which will be helpful to reveal their strong interaction. For comparison, we have presented the numerical results of the scattering lengths (1) in the framework of the heavy meson chiral perturbation theory and (2) in the framework of the infrared regularization. The chiral expansion converges well in some channels.

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arXiv2011

Possible Deuteron-like Molecular States Composed of Heavy Baryons

We perform a systematic study of the possible loosely bound states composed of two charmed baryons or a charmed baryon and an anti-charmed baryon within the framework of the one boson exchange (OBE) model. We consider not only the $π$ exchange but also the $η$, $ρ$, $ω$, $ϕ$ and $σ$ exchanges. The $S-D$ mixing effects for the spin-triplets are also taken into account. With the derived effective potentials, we calculate the binding energies and root-mean-square (RMS) radii for the systems $Λ_cΛ_c(\barΛ_c)$, $Ξ_cΞ_c(\barΞ_c)$, $Σ_cΣ_c(\barΣ_c)$, $Ξ_c^\primeΞ_c^\prime(\barΞ_c^\prime)$ and $Ω_cΩ_c(\barΩ_c)$. Our numerical results indicate that: (1) the H-dibaryon-like state $Λ_cΛ_c$ does not exist; (2) there may exist four loosely bound deuteron-like states $Ξ_cΞ_c$ and $Ξ_c^\primeΞ_c^\prime$ with small binding energies and large RMS radii.

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arXiv2011

$Z_b(10610)^\pm$ and $Z_b(10650)^\pm$ as the $B^\bar{B}$ and $B^\bar{B}^{*}$ molecular states

In the framework of the one-boson-exchange model, we have studied the interaction of the $B^*\bar{B}$ and $B^*\bar{B}^{*}$ system. After considering the S-wave and D-wave mixing, we notice that both $Z_b(10610)^\pm$ and $Z_b(10650)^\pm$ can be interpreted as the $B^*\bar{B}$ and $B^*\bar{B}^{*}$ molecular states quite naturally. Within the same framework, there also exist several molecular charmonia including X(3872) and several other molecular bottomonia, which are the partners of $Z_b(10610)$ and $Z_b(10650)$. The long-range one-pion-exchange force alone is strong enough to form these loosely bound molecular states, which ensures the numerical results quite model-independent and robust.

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arXiv2011

The Decay Properties of the 1^{-+} Hybrid State

Within the framework of the QCD sum rules, we consider the three-point correlation function, work at the limit q^2 -> 0 and m_π-> 0, and pick out the singular term ~ {1\over q^2} to extract the pionic coupling constants of the 1^{-+} hybrid meson. Then we calculate the decay widths of different modes. The decay width of the S-wave modes b_1 π, f_1πincreases quickly as the hybrid meson mass and decay momentum increase. But for the low mass hybrid meson around 1.6 GeV, the P-wave decay mode ρπis very important and its width is around 180 MeV, while the widths of ηπand η^\prime πare strongly suppressed. We suggest the experimental search of π_1(1600) through the decay chains at BESIII: e^+e^- -> J/ψ(ψ') -> π_1 +γor e^+e^- -> J/ψ(ψ') -> π_1 +ρwhere the π_1 state can be reconstructed through the decay modes π_1 -> ρπ-> π^+π^-π^0 or π_1 -> f_1(1285)π^0. It is also interesting to look for π_1 using the available BELLE/BABAR data through the process e^+e^- -> γ^\ast -> ρπ_1, b_1π_1, γπ_1 etc.

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arXiv2011

Novel charmonium-like structures in the $J/ψϕ$ and $J/ψω$ invariant mass spectra

Stimulated by the new evidence of Y(4274) observed in the $J/ψϕ$ invariant mass spectrum, we first propose the charmonium-like state Y(4274) as the S-wave $D_s\bar{D}_{s0}(2317)+h.c.$ molecular state with $J^P=0^-$, which is supported well by dynamics study of the system composed of the pseudoscalar and scalar charmed mesons. The S-wave $D\bar{D}_{0}(2400)+h.c.$ molecular charmonium appears as the molecular partner of Y(4274), which is in accord with the enhancement structure appearing at 4.2 GeV in the $J/ψω$ invariant mass spectrum from B decays. Our study shows that the enhancement structures, $i.e.$, the newly observed Y(4274) and the previously announced $Y(4140)/Y(3930)$ in the $J/ψϕ$ and $J/ψω$ invariant mass spectra, can be understood well under the uniform framework of the molecular charmonium, which can be tested by future experiments.

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arXiv2011

Pseudoscalar Meson and Decuplet Baryon Scattering Lengths

We have systematically calculated the S-wave pseudoscalar meson and decuplet baryon scattering lengths to the third order in the small scale expansion scheme of the heavy baryon chiral perturbation theory. We hope the future study may test the framework and the present predictions.

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arXiv2011

The Vector and Axial-Vector Charmonium-like States

After constructing all the tetraquark interpolating currents with $J^{PC}=1^{-+}, 1^{--}, 1^{++}$ and $1^{+-}$ in a systematic way, we investigate the two-point correlation functions to extract the masses of the charmonium-like states with QCD sum rule. For the $1^{--}$ $qc\bar q\bar c$ charmonium-like state, $m_X=4.6\sim4.7$ GeV, which implies a possible tetraquark interpretation for the state Y(4660). The masses for both the $1^{++}$ $qc\bar q\bar c$ and $sc\bar s\bar c$ charmonium-like states are around $4.0\sim 4.2$ GeV, which are slightly above the mass of X(3872). For the $1^{-+}$ $qc\bar q\bar c$ charmonium-like state, the extracted mass is $4.5\sim 4.7$ GeV. We also discuss the possible decay modes and experimental search of the $1^{-+}$ charmonium-like states.

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