arXiv subjects

Li-Sheng Geng

Publications and source records attributed to Li-Sheng Geng.

211 records · Page 12Linked to original sources

arXiv2015

K-pi interaction in finite volume and the K* resonance

We evaluate energy levels of the K-pi system in the K* channel in finite volume using chiral unitary theory. We use these energy levels to obtain K-pi phase shifts, and then obtain the K* mass and its decay width. We investigate their dependence on the pion mass and compare this with Lattice QCD calculations. We also compare our method with the standard Luscher approach, and solve the inverse problem to obtain the K-pi phase shifts from these "synthetic" lattice data.

hep-lat↗

arXiv2015

Scalar strangeness content of the nucleon and baryon sigma terms

The scalar strangeness content of the nucleon, characterized by the so-called strangeness-nucleon sigma term, is of fundamental importance in understanding its sea-quark flavor structure. We report a determination of the octet baryon sigma terms via the Feynman-Hellmann theorem by analyzing the latest high-statistics $n_f=2+1$ lattice QCD simulations with covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order. In particular, we predict $σ_{πN}=55(1)(4)$ MeV and $σ_{sN}=27(27)(4)$ MeV, while the first error is statistical and the second systematic due to different lattice scales. The predicted $σ_{sN}$ is consistent with the latest LQCD results and the results based on the next-to-next-to-leading order chiral perturbation theory. Several key factors in determining the sigma terms are systematically taken into account and clarified for the first time, including the effects of lattice scale setting, systematic uncertainties originating from chiral expansion truncations, and constraint of strong-interaction isospin breaking effects.

hep-ph↗

arXiv2014

The D-wave heavy-light mesons from QCD sum rules

We study the D-wave c_bar s heavy meson doublets (1^-,2^-) and (2^-,3^-) using the method of QCD sum rule in the framework of heavy quark effective theory. Choosing the same threshold values omega_c around 2.7 Gev, we calculate the masses of the 1^- and 3^- states. They are m_{D*_{s1}} = 2.81 \pm 0.10 GeV and m_{D*_{s3}} = 2.85 \pm 0.08 GeV, consistent with the newly observed D*_{s1}(2860) and D*_{s3}(2860) states by LHCb. The masses of their 2^- partners are calculated to be 2.82 \pm 0.10 and 2.81 \pm 0.08 GeV. The mass splittings within the same doublet are calculated to be m_{D_{s2}} - m_{D*_{s1}} = 0.016 \pm 0.007 GeV and m_{D*_{s3}} - m_{D'_{s2}} = 0.039 \pm 0.014 GeV.

hep-ph↗

arXiv2014

The $\bar{p} p \to ϕϕ$ reaction in an effective Lagrangian approach

We investigate the $\bar{p} p \to ϕϕ$ reaction within an effective Lagrangian approach.We show that the inclusion of either a scalar meson $f_0$ or a tensor meson $f_2$ in the $s$-channel can lead to a fairly good description of the bump structure of the total cross section around the invariant $\bar{p} p$ mass $W \simeq 2.2$ GeV, which cannot be reproduced with only the "background" contributions from $t$- and $u$-channel $N^*(1535)$ resonance as studied in a previous work. From the fits, we infer the properties of the involved scalar or tensor resonances.

nucl-th↗

arXiv2014

Study of Hadrons Using the Gaussian Functional Method in the O(4) Linear $σ$ Model

We study properties of hadrons in the O(4) linear $σ$ model, where we take into account fluctuations of mesons around their mean field values using the Gaussian functional (GF) method. In the GF method we calculate dressed $σ$ and $π$ masses, where we include the effect of fluctuations of mesons to find a better ground state wave function than the mean field approximation. Then we solve the Bethe-Salpeter equations and calculate physical $σ$ and $π$ masses. We recover the Nambu-Goldstone theorem for the physical pion mass to be zero in the chiral limit. The $σ$ meson is a strongly correlated meson-meson state, and has a 4 quark structure. We calculate $σ$ and $π$ masses as functions of temperature for the two cases of chiral limit and explicit chiral symmetry breaking. We get similar behaviors for the $σ$ and $π$ masses as the case of the mean field approximation, but the coupling constants are much larger than the values of the case of the mean field approximation.

nucl-th↗

arXiv2014

Octet baryon masses and sigma terms in covariant baryon chiral perturbation theory

We report an analysis of the octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order with and without the virtual decuplet contributions. Particular attention is paid to the finite-volume corrections and the finite lattice spacing effects on the baryon masses. A reasonable description of all the publicly available $n_f=2+1$ lattice QCD data is achieved.Utilyzing the Feynman-Hellmann theorem, we determine the nucleon sigma terms as $σ_{πN}=55(1)(4)$ MeV and $σ_{sN}=27(27)(4)$ MeV.

nucl-th↗

arXiv2014

Test of the $h_1(1830)$ made of $K^{}\bar{K}^$ with the $η_c\rightarrow ϕK^{}\bar{K}^{}$ decay

We present a new reaction, complementary to the $J/ψ\rightarrow ηK^{*0}\bar{K}^{*0}$ from which an $h_1$ resonance with mass around $1830$ MeV was reported from a BESIII experiment. The new reaction is $η_c\rightarrow ϕK^*\bar{K}^*$, or $η_c(2S)\rightarrow ϕK^*\bar{K}^*$. Using the information from the analysis of $J/ψ\rightarrow ηK^{*0}\bar{K}^{*0}$, we find that the $K^*\bar{K}^*$ invariant mass distribution for those two $η_c$ decays exhibits a clear peak around $1830$ MeV perfectly distinguishable from what one obtains with pure phase space. We suggest the implementation of these reactions to assert the existence of this elusive resonance which, by its nature as a vector-vector molecule with $0^-(1^{+-})$ quantum numbers, only couples to the $K^*\bar{K}^*$ channel.

nucl-th↗

arXiv2014

Pseudocalar meson and vector meson interactions and dynamically generated axial-vector mesons

The axial-vector mesons $a_1(1260)$, $b_1(1235)$, $f_1(1285)$, $h_1(1170)$, $h_1(1380)$, and $K_1(1270)$ are dynamically generated in the unitized chiral perturbation theory. Such a picture has been tested extensively in the past few years. In this work, we calculate the interaction kernel up to $\mathcal{O}(p^2)$ and study the impact on the dynamically generated axial-vector states. In anticipation of future lattice QCD simulations, we calculate the scattering lengths and the pole positions as functions of the pion mass, with the light-quark mass dependence of the kaon, the eta, and the vector mesons determined by the $n_f=2+1$ lattice QCD simulations of the PACS-CS Collaboration.

nucl-th↗

arXiv2014

Decuplet baryon masses in covariant baryon chiral perturbation theory

We present an analysis of the lowest-lying decuplet baryon masses in the covariant baryon chiral perturbation theory with the extended-on-mass-shell scheme up to next-to-next-to-next-to-leading order. In order to determine the $14$ low-energy constants, we perform a simultaneous fit of the $n_f=2+1$ lattice QCD data from the PACS-CS, QCDSF-UKQCD, and HSC Collaborations, taking finite-volume corrections into account self-consistently. We show that up to next-to-next-to-next-to-leading order one can achieve a good description of the lattice QCD and experimental data. Surprisingly, we note that the current lattice decuplet baryon masses can be fitted rather well by the next-to-leading order baryon chiral perturbation theory, which, however, misses the experimental data a little bit. Furthermore, we predict the pion- and strangeness-sigma terms of the decuplet baryons by use of the Feynman-Hellmann theorem.

nucl-th↗

arXiv2014

Chiral extrapolation and finite-volume dependence of the hyperon vector couplings

The hyperon vector form factors at zero momentum transfer, $f_1(0)$, play an important role in a precise determination of the Cabibbo-Kobayashi-Maskawa matrix element $V_{us}$. Recent studies based on lattice chromodynamics (LQCD) simulations and covariant baryon chiral perturbation theory yield contradicting results. In this work, we study chiral extrapolation of and finite-volume corrections to the latest $n_f=2+1$ LQCD simulations. Our results show that finite-volume corrections are relatively small and can be safely ignored at the present LQCD setup of $m_πL=4.6$ but chiral extrapolation needs to be performed more carefully. Nevertheless, the discrepancy remains and further studies are needed to fully understand it.

hep-ph↗

arXiv2014

Off-shell effects on the interaction of Nambu-Goldstone bosons and $D$ mesons

The Bethe-Salpeter equation in unitarized chiral perturbation theory is usually solved with the so-called on-shell approximation. The underlying argument is that the off-shell effects can be absorbed by the corresponding coupling constants and physical masses, which has been corroborated by the success of unitarized chiral perturbation theory in describing a variety of physical phenomena. Such an approximation needs to be scrutinized when applied to study the light-quark mass evolution of physical observables, as routinely performed nowadays. In the present work, we propose to solve the Bethe-Salpeter equation with the full off-shell terms of the chiral potentials and apply this formalism to the description of the latest $n_f=2+1$ lattice QCD (LQCD) data on the scattering lengths of Nambu-Goldstone bosons off $D$ mesons. It is shown that the LQCD data can be better described in this formalism than in the widely used on-shell approximation. On the other hand, no qualitative difference between the on-shell and off-shell approaches is observed for the light-quark mass evolution of the scattering lengths, given the limited LQCD data and their relatively large uncertainties. We also show that the light-quark mass dependence of the $D^*_{s0}(2317)$ remains essentially the same in both approaches.

hep-ph↗

arXiv2014

Baryon chiral perturbation theory with Wilson fermions up to $\mathcal{O}(a^2)$ and discretization effects of latest $n_f=2+1$ LQCD octet baryon masses

We construct the chiral Lagrangians relevant in studies of the ground-state octet baryon masses up to $\mathcal{O}(a^2)$ by taking into account discretization effects and calculate the masses up to $\mathcal{O}(p^4)$ in the extended-on-mass-shell scheme. As an application, we study the latest $n_f=2+1$ LQCD data on the ground-state octet baryon masses from the PACS-CS, QCDSF-UKQCD, HSC, and NPLQCD Collaborations. It is shown that the discretization effects for the studied LQCD simulations are at the order of one to two percent for lattice spacings up to $0.15$ fm and the pion mass up to 500 MeV.

hep-ph↗

arXiv2014

Thermodynamics of hadrons using the Gaussian functional method in the linear sigma model

We investigate thermodynamics of hadrons using the Gaussian functional method (GFM) at finite temperature. Since the interaction among mesons is very large, we take into account fluctuations of mesons around their mean field values using the GFM. We obtain the ground state energy by solving the Schrödinger equation. The meson masses are obtained using the energy minimization condition. The resulting mass of the Nambu-Goldstone boson is not zero even in the spontaneous chiral symmetry broken phase due to the non-perturbative effect. We consider then the bound state of mesons using the Bethe-Salpeter equation and show that the Nambu-Goldstone theorem is recovered. We investigate further the behavior of the meson masses and the mean filed value as functions of temperature for the cases of chiral limit and explicit chiral symmetry breaking.

hep-ph↗