arXiv subjects

Xiu-Lei Ren

Publications and source records attributed to Xiu-Lei Ren.

51 records · Page 3Linked to original sources

arXiv2017

Hyperon-nucleon Scattering In A Covariant Chiral Effective Field Theory Approach

A recently proposed covariant chiral effective field theory approach is applied to study strangeness $S=-1$ hyperon-nucleon interactions at leading order. 12 low energy constants are introduced by Lorentz invariance, which is different from the heavy baryon approach, where only five appear. The Kadyshevsky equation is employed to iterate the chiral potentials. A quite satisfactory description of the 36 hyperon-nucleon scattering data is obtained with $χ^2\simeq 17$, which is comparable with the next-to-leading order heavy baryon approach. The results hint at a more efficient way to construct the chiral potentials.

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arXiv2017

$B_sπ$--$B\bar{K}$ interactions in finite volume and the $X(5568)$

The recent observation of $X(5568)$ by the D0 Collaboration has aroused a lot of interest both theoretically and experimentally. In the present work, we first point out that $X(5568)$ and $D_{s0}^*(2317)$ cannot simultaneously be of molecular nature, from the perspective of heavy-quark symmetry and chiral symmetry, based on a previous study of the lattice QCD scattering lengths of $DK$ and its coupled channels. Then we compute the discrete energy levels of the $B_sπ$ and $B\bar{K}$ system in finite volume using unitary chiral perturbation theory. The comparison with the latest lattice QCD simulation, which disfavors the existence of $X(5568)$, supports our picture where the $B_sπ$ and $B\bar{K}$ interactions are weak and $X(5568)$ cannot be a $B_sπ$ and $B\bar{K}$ molecular state. In addition, we show that the extended Weinberg compositeness condition also indicates that $X(5568)$ cannot be a molecular state made from $B_sπ$ and $B\bar{K}$ interactions.

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arXiv2017

Consistency between SU(3) and SU(2) chiral perturbation theory for the nucleon mass

Treating the strange quark mass as a heavy scale compared to the light quark mass, we perform a matching of the nucleon mass in the SU(3) sector to the two-flavor case in covariant baryon chiral perturbation theory. The validity of the $19$ low-energy constants appearing in the octet baryon masses up to next-to-next-to-next-to-leading order~\cite{Ren:2014vea} is supported by comparing the effective parameters (the combinations of the $19$ couplings) with the corresponding low-energy constants in the SU(2) sector~\cite{Alvarez-Ruso:2013fza}. In addition, it is shown that the dependence of the effective parameters and the pion-nucleon sigma term on the strange quark mass is relatively weak around its physical value, thus providing support to the assumption made in Ref.~\cite{Alvarez-Ruso:2013fza}.

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arXiv2016

Strangeness $S=-1$ hyperon-nucleon scattering in covariant chiral effective field theory

Motivated by the successes of covariant baryon chiral perturbation theory in one-baryon systems and in heavy-light systems, we study relevance of relativistic effects in hyperon-nucleon interactions with strangeness $S=-1$. In this exploratory work, we follow the covariant framework developed by Epelbaum and Gegelia to calculate the $YN$ scattering amplitude at leading order. By fitting the five low-energy constants to the experimental data, we find that the cutoff dependence is mitigated, compared with the heavy-baryon approach. Nevertheless, the description of the experimental data remains quantitatively similar at leading order.

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arXiv2016

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

We report on a recent study of the ground-state octet baryon masses and sigma terms in covariant baryon chiral perturbation theory with the extended-on-mass-shell scheme up to next-to-next-to-next-to-leading order. To take into account lattice QCD artifacts, the finite-volume corrections and finite lattice spacing discretization effects are carefully examined. We performed a simultaneous fit of all the $n_f = 2+1$ lattice octet baryon masses and found that the various lattice simulations are consistent with each other. Although the finite lattice spacing discretization effects up to $\mathcal{O}(a^2)$ can be safely ignored, but the finite volume corrections cannot even for configurations with $M_ϕL>4$. As an application, we predicted the octet baryon sigma terms using the Feynman-Hellmann theorem. In particular, the pion- and strangeness-nucleon sigma terms are found to be $σ_{πN} = 55(1)(4)$ MeV and $σ_{sN} = 27(27)(4)$ MeV, respectively.

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arXiv2015

$S$-wave $KK^*$ interaction in a finite volume and the $f_1(1285)$

Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called $XYZ$ particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson $f_1(1285)$ can also be understood as a dynamically generated state built upon the $KK^*$ interaction. In this work, we calculate the energy levels of the $KK^*$ system in the $f_1(1285)$ channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid approach adopted in previous studies. We also study the inverse problem of extracting the bound state information from synthetic lattice QCD data and comment on the difference between our approach and the L{\" u}scher method.

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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.

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arXiv2015

States of $ρD^* \bar D^*$ with $J=3$ within the Fixed Center Approximation to the Faddeev equations

We study the interaction of the a $ρ$ and $D^*$, $\bar D^*$ with spins aligned using the Fixed Center Approximation to the Faddeev equations. We select a cluster of $D^* \bar D^*$, which is found to be bound in $I=0$ and can be associated to the X(3915), and let the $ρ$ meson orbit around the $D^*$ and $\bar D^*$. In this case we find an $I=1$ state with mass around 4340 MeV and narrow width of about 50 MeV. We also investigate the case with a cluster of $ρD^*$ and let the $\bar D^*$ orbit around the system of the two states. The $ρD^*$ cluster is also found to bind and leads to the $D^*_2(2460)$ state. The addition of the extra $\bar D^*$ produces further binding and we find, with admitted uncertainties, a state of $I=0$ around 4000 MeV, and a less bound narrow state with $I=1$ around 4200 MeV.

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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.

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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.

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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.

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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.

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arXiv2013

Lowest-lying octet baryon masses in covariant baryon chiral perturbation theory

We report on a systematic study of the ground-state octet baryon masses in the covariant baryon chiral perturbation theory with the extended-on-mass-shell renormalization scheme up to next-to-next-to-next-to-leading order, taking into account the contributions of the virtual decuplet baryons. A reasonable description of the lattice results is achieved by fitting simultaneously all the publicly available $n_f = 2+1$ lattice QCD data. It confirms that the various lattice simulations are consistent with each other. We stress that a self-consistent treatment of finite-volume corrections is important to obtain a $χ^2/\rm{d.o.f.}$ about 1.

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arXiv2013

Virtual decuplet effects on octet baryon masses in covariant baryon chiral perturbation theory

We extend a previous analysis of the lowest-lying octet baryon masses in covariant baryon chiral perturbation theory (ChPT) by explicitly taking into account the contribution of the virtual decuplet baryons. Up to next-to-next-to-next-to-leading order (N$^3$LO), the effects of these heavier degrees of freedom are systematically studied. Their effects on the light-quark mass dependence of the octet baryon masses are shown to be relatively small and can be absorbed by the available low-energy constants up to N$^3$LO. Nevertheless, a better description of the finite-volume corrections of the lattice QCD data can be achieved, particularly those with small $M_ϕL$ ($<4$), which is demonstrated by a careful study of the NPLQCD and QCDSF-UKQCD small-volume data. Finally, we show that the predicted pion- and strangeness-baryon sigma terms are only slightly changed by the inclusion of the virtual decuplet baryons.

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arXiv2012

Octet-baryon masses in finite space

We report on a recent study of finite-volume effects on the lowest-lying octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-leading order by analysing the latest $n_f = 2 + 1$ lattice QCD results from the NPLQCD Collaboration.

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