arXiv subjects

Yan-Rui Liu

Publications and source records attributed to Yan-Rui Liu.

70 records · Page 4Linked to original sources

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.

hep-ph↗

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.

hep-ph↗

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.

hep-ph↗

arXiv2009

A chiral quark model study of $Z^+(4430)$ in the molecular picture

We investigated the bound state problem of the S wave charged $D_1 \bar{D}^*$ ($D_1' \bar{D}^*$) system in a chiral quark model by solving the resonating group method equation. Our preliminary study does not favor the molecular assumption of $Z^+(4430)$. On the contrary, if $Z^+(4430)$ is really a molecule, its partner with opposite $G$-parity should also exist and probably may be found in the $π^+η_c(2S)$, $J/ψπ^+π^0$, or $ψ'π^+π^0$ channel. For the bottom systems, we found the existence of both $I^G$=$1^+$ and $I^G$=$1^-$ $B_1 \bar{B}^*$ ($B_1' \bar{B}^*$) molecules is possible.

hep-ph↗

arXiv2009

The bound state problem of S-wave heavy quark meson-aitimeson systems

We investigated systematically whether the S-wave ($\bar{Q}q$) meson and the ($Q\bar{q}$) meson may form S-wave bound states in a chiral SU(3) quark model by solving the resonating group method equation. Here $Q=c$ or $b$ and $q=u$, $d$ or $s$. Our preliminary calculation disfavors the existence of $I=\frac12$ ($\bar{Q}l$)-($Q\bar{s}$) molecules ($l=u,d$) while favors the existence of isoscalar $B\bar{B}$, $B^*\bar{B}^*$ (J=2) and $B\bar{B}^*$ (C=+) molecules. The existence of isovector (charm-anticharm) and (charm-bottom) molecules is also disfavored. Therefore the resonance-like structure $Z^+(4051)$ is unlikely to be an S-wave $D^*\bar{D}^*$ molecule.

hep-ph↗

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.

hep-ph↗

arXiv2009

X(3872) and the bound state problem of $D^0\bar{D}^{\ast0}$ ($\bar{D}^0{D}^{\ast0}$) in a chiral quark model

The bound state problem of $D^0\bar{D}^{\ast0}$ ($\bar{D}^0{D}^{\ast0}$) is relevant to the molecular interpretation of the X(3872). We investigated this problem in a chiral quark model by solving the resonating group method equation. We found the system is unbound through S-wave $π$ and $σ$ interactions. The inclusion of $ρ$ and $ω$ meson exchanges is helpful to the formation of a molecule. Because the binding energy relies on the coupling constants, we cannot draw a definite conclusion whether a molecular state exists in $D^0\bar{D}^{\ast0}$ ($\bar{D}^0{D}^{\ast0}$) system. When moving on to the bottom counterpart, we obtained an S-wave $B\bar{B}^\ast$ state.

hep-ph↗

arXiv2008

The Δcontribution to the parity-violating nucleon-nucleon force

Because the nucleon may be excited and transformed into a virtual $Δ$ resonance easily, we consider the decuplet contribution to the parity-violating (PV) nucleon-nucleon interaction in the chiral effective field theory. The effective PV nucleon-nucleon potential is derived without introducing any unknown coupling constants.

nucl-th↗

arXiv2008

X(3872) and Other Possible Heavy Molecular States

We perform a systematic study of the possible molecular states composed of a pair of heavy mesons such as $D\bar D$, $D^\ast\bar D$, $D^\ast \bar D^\ast$ in the framework of the meson exchange model. The exchanged mesons include the pseudoscalar, scalar and vector mesons. Through our investigation, we find that (1) the structure X(3764) is not a molecular state; (2) There exists strong attraction in the range $r < 1$ fm for the $D^*\bar D^*$ system with $J=0, 1$. If future experiments confirm $Z^+(4051)$ as a loosely bound molecular state, its quantum number is probably $J^{P}=0^+$. Its partner state $Φ^{**0}$ may be searched for in the $π^0χ_{c1}$ channel; (3) The vector meson exchange provides strong attraction in the $D^\ast \bar D$ channel together with the pion exchange. A bound state solution exists with a reasonable cutoff parameter $Λ\sim 1.4$ GeV. X(3872) may be accommodated as a molecular state dynamically although drawing a very definite conclusion needs further investigation; (4) The $B^\ast \bar B$ molecular state exists.

hep-ph↗

arXiv2008

$Z^+(4430)$ as a $D_1'{D}^* $ ($D_1{D}^* $) molecular state

We reexamine whether $Z^+(4430)$ could be a $D_1'-{D}^*$ or $D_1-{D}^*$ molecular state after considering both the pion and $σ$ meson exchange potentials and introducing the form factor to take into account the structure effect of the interaction vertex. Our numerical analysis with Matlab package MATSLISE indicates the contribution from the sigma meson exchange is small for the $D_1'-{D}^*$ system and significant for the $D_1-{D}^*$ system. The S-wave $D_1-\bar{D}^*$ molecular state with only $J^{P}=0^-$ and $D_1'-{D}^*$ molecular states with $J^P=0^-,1^-,2^-$ may exist with reasonable parameters. One should investigate whether the broad width of $D_1'$ disfavors the possible formation of molecular states in the future. The bottom analog $Z_B$ of $Z^+(4430)$ has a larger binding energy, which may be searched at Tevatron and LHC. Experimental measurement of the quantum number of $Z^+(4430)$ may help uncover its underlying structure.

hep-ph↗

arXiv2008

Is X(3872) {\sl Really} a Molecular State?

After taking into account both the pion and sigma meson exchange potential, we have performed a dynamical calculation of the $D^0\bar{D}^{\ast0}$ system. The $σ$ meson exchange potential is repulsive from heavy quark symmetry and numerically important for a loosely bound system. Our analysis disfavors the interpretation of X(3872) as a loosely bound molecular state if we use the experimental $D^\ast Dπ$ coupling constant $g=0.59$ and a reasonable cutoff around 1 GeV, which is the typical hadronic scale. Bound state solutions with negative eigenvalues for the $D\bar{D}^\ast$ system exist only with either a very large coupling constant (two times of the experimental value) or a large cutoff ($Λ\sim 6$ GeV or $β\sim 6$ GeV$^2$). In contrast, there probably exists a loosely bound S-wave $B\bar{B}^\ast$ molecular state. Once produced, such a molecular state would be rather stable since its dominant decay mode is the radiative decay through $B^\ast\to B γ$. Experimental search of these states will be very interesting.

hep-ph↗

arXiv2008

Dynamics study of $Z^+(4430)$ and X(3872) in molecular picture

In this talk, we review our recent work about the dynamical studies of $Z^+(4430)$ and X(3872). $Z^+(4430)$ can not be explained as a $D_1'D^*$ or $D_1D^*$ molecular state only considering one pion exchange potential without the cutoff, which needs to be confirmed by introducing sigma exchange potential and adding the cutoff in the effective potential. One also excludes the possibility of X(3872) as a $DD^*$ molecular state by one pion and one sigma exchanges with the cutoff. Fortunately there exists an S-wave $BB^*$ bound state with $J^{PC}=1^{++}$. we suggest future experiment to search this state.

hep-ph↗

arXiv2007

Is Z^+(4430) a loosely bound molecular state?

Since $Z^+(4430)$ lies very close to the threshold of $D^\ast{\bar D}_1$, we investigate whether $Z^+(4430)$ could be a loosely bound S-wave state of $D^\ast{\bar D}_1$ or $D^\ast{\bar D}^\prime_1$ with $J^P=0^-, 1^-, 2^-$, i.e., a molecular state arising from the one-pion-exchange potential. The potential from the crossed diagram is much larger than that from the diagonal scattering diagram. With various trial wave functions, we notice that the attraction from the one pion exchange potential alone is not strong enough to form a bound state with realistic pionic coupling constants deduced from the decay widths of $D_1$ and $D^\prime_1$.

hep-ph↗

arXiv2007

Bottom Baryons

Recently CDF and D0 collaborations observed several bottom baryons. In this work we perform a systematic study of the masses of bottom baryons up to $1/m_Q$ in the framework of heavy quark effective field theory (HQET) using the QCD sum rule approach. The extracted chromo-magnetic splitting between the bottom baryon heavy doublet agrees well with the experimental data.

hep-ph↗

arXiv2007

Decuplet contribution to the meson-baryon scattering lengths

We calculate decuplet contributions to the s-wave pseudoscalar meson octet-baryon scattering lengths to the third order in heavy baryon chiral perturbation theory (HB$χ$PT). Using experimental pion-nucleon and kaon-nucleon scattering lengths as inputs, we determine low-energy constants and predict other meson-baryon scattering lengths. Numerically we consider three cases: (1) the case with only baryon octet contributions; (2) with decuplet contributions and (3) in the large N_c limit. Hopefully, the analytical expressions and the predictions are helpful to future investigations of the meson-baryon scattering lengths.

hep-ph↗

arXiv2007

Meson-baryon scattering lengths in HB$χ$PT

We calculate the chiral corrections to the s-wave pseudoscalar meson octet-baryon scattering lengths $a_{MB}$ to ${\cal O}(p^3)$ in the SU(3) heavy baryon chiral perturbation theory (HB$χ$PT). Hopefully the obtained analytical expressions will be helpful in the chiral extrapolation of these scattering lengths in the future lattice simulation.

hep-ph↗