Searcharxiv⌕ Search

arXiv subjects

Y. W. Yu

Publications and source records attributed to Y. W. Yu.

35 records · Page 2Linked to original sources
arXiv2006

Thermal evolution of rotating strange stars in color superconductivity phase

Under the combination effect of the recommencement heating due to spin-down of strange stars and the heat perseveration due to weak conduct heat of the crust, the Cooper pair breaking and formation(PBF) in color superconduction quark matter arises. We investigated the cooling of the strange stars with a crust in color superconductivity phase including both decomfinement heating and PBF process. We find that deconfinement heating can delay the thermal evolution of strange stars and the PBF process suppresses the early temperature rise of the stars. The cooling strange stars behave within the brightness constraint of young compact objects when the color superconductivity gap is small enough.

astro-ph↗
arXiv2006

Effect of r-mode instability on the evolution of isolated strange stars

We studied the evolution of isolated strange stars synthetically, considering the influence of {\it r-}mode instability. Our results show that the cooling of strange stars with non-ultra strong magnetic fields is delayed by the heating due to the {\it r-}modes damping during million years, while the spin-down of the stars is dominated by gravitational radiation. Especially for the strange stars in a possible existing color-flavor locked phase, the effect of the {\it r-}mode instability on the evolution of the stars becomes extremely important since the viscosity, the neutrino emissivity, and the specific heat involving paring quarks are blocked. It leads to the cooling of these color superconducting stars is very slow, and the stars can remain high temperature within million years differing completely from previous understanding. In this case, a strange star in color-flavor locked phase can be located at the bottom of its {\it r-}mode instability window for a long time, but does not spin down to a very low frequency within hours.

astro-ph↗
arXiv2006

Baryon-meson interactions in chiral quark model

Using the resonating group method (RGM), we dynamically study the baryon-meson interactions in chiral quark model. Some interesting results are obtained: (1) The Sigma K state has an attractive interaction, which consequently results in a Sigma K quasibound state. When the channel coupling of Sigma K and Lambda K is considered, a sharp resonance appears between the thresholds of these two channels. (2) The interaction of Delta K state with isospin I=1 is attractive, which can make for a Delta K quasibound state. (3) When the coupling to the Lambda K* channel is considered, the N phi is found to be a quasibound state in the extended chiral SU(3) quark model with several MeV binding energy. (4) The calculated S-, P-, D-, and F-wave KN phase shifts achieve a considerable improvement in not only the signs but also the magnitudes in comparison with other's previous quark model study.

nucl-th↗
arXiv2005

N K Pi molecular state with I=1 and J(Pi)=3/2-

The structure of the molecule-like state of $NKπ$ with spin-parity $J^π={3/2}^-$ and isospin I=1 is studied within the chiral SU(3) quark model. First we calculate the $NK$, $Nπ$, and $Kπ$ phase shifts in the framework of the resonating group method (RGM), and a qualitative agreement with the experimental data is obtained. Then we perform a rough estimation for the energy of $(NKπ)_{J^π={3/2}^-,I=1}$, and the effect of the mixing to the configuration $(ΔK)_{J^π={3/2}^-,I=1}$ is also considered. The calculated energy is very close to the threshold of the $NKπ$ system. A detailed investigation is worth doing in the further study.

hep-ph↗
arXiv2005

N phi state in chiral quark model

The structures of N phi states with spin-parity J^{p}=3/2^- and J^p=1/2^- are dynamically studied in both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The channel coupling of N phi and Lambda K* is considered, and the effect of the tensor force which results in the mixing of S and D waves is also investigated. The results show that the N phi state has an attractive interaction, and in the extended chiral SU(3) quark model such an attraction plus the channel coupling effect can consequently make for an N phi quasi-bound state with several MeV binding energy.

nucl-th↗
arXiv2005

Coupled-channels study of Lambda K and Sigma K states in the chiral SU(3) quark model

The $S$-wave $ΛK$ and $ΣK$ states with isospin $I=1/2$ are dynamically investigated within the framework of the chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a good description of the energies of the baryon ground states, the binding energy of the deuteron, and the experimental data of the nucleon-nucleon ($NN$) and nucleon-hyperon ($NY$) scattering. Assumed not to give important contributions in the scattering processes, the s-channel quark-antiquark ($q\bar q$) annihilation interactions are not included as a first step. The results show a strong attraction between $Σ$ and $K$, which consequently results in a $ΣK$ quasi-bound state with about 17 MeV binding energy, unlike the case of $ΛK$ which is unbound. When the channel coupling of $ΛK$ and $ΣK$ is considered, a sharp resonance state near 1670 MeV with spin-parity $J^P=1/2^-$ is found. The narrow gap of the $ΛK$ and $ΣK$ thresholds, the strong attraction between $Σ$ and $K$, and the sizeable off-diagonal matrix elements of $ΛK$ and $ΣK$ are responsible for the appearance of this resonance.

hep-ph↗
arXiv2005

Further study on 5q configuration states in the chiral SU(3) quark model

The structure of the $5q$ configuration states with strangeness ${\cal{S}}=+1$ is further studied in the chiral SU(3) quark model based on our previous work. We calculate the energies of fifteen low configurations of the $5q$ system, four lowest configurations of $J^π={1/2}^-$ with $4q$ partition $[4]_{orb}(0s^4)[31]^{σf}$, four of $J^π={1/2}^+$ with $4q$ partition $[31]_{orb}(0s^30p)[4]^{σf}$ and seven of $J^π={1/2}^+$ with $4q$ partition $[4]_{orb}(0s^30p)[31]^{σf}$. Some modifications are made in this further study, i.e., the orbital wave function is extended as an expansion of 4 different size harmonic oscillator forms; three various forms (quadratic, linear and error function form) of the color confinement potential are considered; the states with $4q$ partition $[4]_{orb}(0s^30p)[31]^{σf}$ are added, which are unnegligible in the $J^π={1/2}^+$ case and were not considered in our previous paper, further the mixing between configurations $[31]_{orb}(0s^30p)[4]^{σf}$ and $[4]_{orb}(0s^30p)[31]^{σf}$ is also investigated. The results show that the T=0 state is still always the lowest one for both $J^π={1/2}^-$ and $J^π={1/2}^+$ states, and $J^π={1/2}^-, T=0$ state is always lower than that of $J^π={1/2}^+$. All of these modifications can only offer several tens to hundred MeV effect, and the theoretical value of the lowest state is still about 245 MeV higher than the experimental mass of $Θ^+$. It seems to be difficult to get the calculated mass close to the observed one with the reasonable parameters in the framework of the chiral SU(3) quark model when the model space is chosen as a $5q$ cluster.

nucl-th↗
arXiv2005

S, P, D, F wave KN phase shifts in the chiral SU(3) quark model

The $S$, $P$, $D$, $F$ wave $KN$ phase shifts have been studied in the chiral SU(3) quark model by solving a resonating group method equation. The numerical results of different partial waves are in agreement with the experimental data except for the cases of $P_{13}$ and $D_{15}$, which are less well described when the laboratory momentum of the kaon meson is greater than 400 MeV.

nucl-th↗
arXiv2004

Resonating group method study of kaon-nucleon elastic scattering in the chiral SU(3) quark model

The chiral SU(3) quark model is extended to include an antiquark in order to study the kaon-nucleon system. The model input parameters $b_u$, $m_u$, $m_s$ are taken to be the same as in our previous work which focused on the nucleon-nucleon and nucleon-hyperon interactions. The mass of the scalar meson $σ$ is chosen to be 675 MeV and the mixing of $σ_0$ and $σ_8$ is considered. Using this model the kaon-nucleon $S$ and $P$ partial waves phase shifts of isospin I=0 and I=1 have been studied by solving a resonating group method (RGM) equation. The numerical results of $S_{01}$, $S_{11}$, $P_{01}$, $P_{03}$, and $P_{11}$ partial waves are in good agreement with the experimental data while the phase shifts of $P_{13}$ partial wave are a little bit too repulsive when the laboratory momentum of the kaon meson is greater than 500 MeV in this present calculation.

nucl-th↗
arXiv2004

The Short Range Mechanism of N-N interaction in the Extended Chiral SU(3) Quark Model

We give the comparisons between the chiral SU(3) quark model and the extended chiral SU(3) quark model. The results show that the phase shifts of NN scattering are very similar. However, the short range mechanisms of nucleon-nucleon interaction are totally different. In the chiral SU(3) quark model, the short range interaction is dominantly from OGE, and in the extended chiral SU(3) quark model, it is dominantly from vector meson exchanges.

nucl-th↗
arXiv2004

N-N Interactions in the Extended Chiral SU(3) Quark Model

The chiral SU(3) quark model is extended to include coupling between vector chiral field and quarks. By using this model, the phase shifts of NN scattering for different partial waves are studied. The results are very similar to those of the chiral SU(3) quark model calculation, in which one gluon exchange (OGE) plays dominate role in the short range part of the quark-quark interactions. Only in the $^1S_0$ case, the one channel phase shifts of the extended chiral SU(3) quark model are obviously improved.

nucl-th↗
arXiv2003

A study of pentaquark $Θ$ state in the chiral SU(3) quark model

The structure of the pentaquark state uudd-sbar is studied in the chiral SU(3) quark model as well as in the extended chiral SU(3) quark model, in which the vector meson exchanges are included. Four configurations of JP=1/2- and four of JP=1/2+ are considered. The results show that the isospin T=0 state is always the lowest one for both JP=1/2- and JP=1/2+ cases in various models. But the theoretical value of the lowest one is still about 200-300 MeV higher than the experimental mass of $Θ$. It seems that a dynamical calculation should be done for the further study.

hep-ph↗
arXiv2000

Possible S-wave Dibaryons in SU(3) Chiral Quark Model

In the framework of the SU(3) chiral quark model, the $S-$wave baryon-baryon bound states are investigated. It is found that according to the symmetry character of the system and the contributions from chiral fields, there are three types of bound states. The states of the first type, such as $[ΩΩ]_{(0,0)}$ and $[Ξ^{*}Ω]_{(0,1/2)}$ are deeply bound dibaryon with narrow widths. The second type states, $[Σ^{*} Δ]_{(0,5/2)}$,$[Σ^{*} Δ]_{(3,1/2)}$, $[ΔΔ]_{(0,3)}$ and $[ΔΔ]_{(3,0)}$ are also bound states, but with broad widths. $[ΞΩ- Ξ^{*}Ω]_{(1,1/2)}$, $[ΞΞ]_{(0,1)}$, and $[N Ω]_{(2,1/2)}$ are third type states. They, like {\em d}, are weakly bound only if the chiral fields can provide attraction between baryons.

nucl-th↗
arXiv2000

Dibaryon Systems In SU(3) Chira Quark Model

The possible candidates of $S-$wave dibaryons with various strange numbers are studied under the chiral SU(3) quark model. It is shown that there are three types of baryon-baryon bound states. The states of the first type are called deuteron-like states. If chiral fields can provide enough attraction between interacting baryons, these systems, such as $[ΞΩ- Ξ^{*}Ω]_{(1,1/2)}$, $[ΞΞ]_{(0,1)}$, $[N Ω]_{(2,1/2)}$ would be weakly bound. The states of the second type such as $[Σ^{*} Δ]_{(0,5/2)}$, $[Σ^{*} Δ]_{(3,1/2)}$, $[ΔΔ]_{(0,3)}$ and $[ΔΔ]_{(3,0)}$ are named as $ΔΔ$-like states. Due to the highly symmetric character in orbital space, these systems could be relatively deeply bound, but the strong decay modes of composed baryons cause the widths of the states much broader. The states of the third type are entitled as $ΩΩ$-like states. Due to the same symmetry character shown in the systems of the second type and the only weak decay mode of composed baryons, for instance in $[ΩΩ]_{(0,0)}$, or at most one strong decay mode of composed baryons, for example in $[Ξ^{*}Ω]_{(0,1/2)}$, these states are deeply bound states with narrow widths. The states of latter two types are most interesting new dibaryon states and should be carefully investigated both theoretically and experimentally.

nucl-th↗
arXiv1999

H-Dihyperon in Quark Cluster Model

The H dihyperon (DH) is studied in the framework of the SU(3) chiral quark model. It is shown that except the $σ$ chiral field, the overall effect of the other SU(3) chiral fields is destructive in forming a stable DH. The resultant mass of DH in a three coupled channel calculation is ranged from 2225 $MeV$ to 2234 $MeV$.

nucl-th↗
arXiv1999

Deltaron Dibaryon Structure in Chiral SU(3) Quark Model

We discuss the structure of Deltaron dibaryon in the chiral SU(3) quark model. The energy of Deltaron is obtained by considering the coupling of the $ΔΔ$ and $CC$ (hidden color) channels. The effects of various parameters on the Deltaron mass are also studied. It is shown that the mass of Deltaron is lower than the mass of $ΔΔ$ but higher than the mass of $ΔN π$.

nucl-th↗