The current constraints from lattice QCD on the existence of the H-dibaryon are discussed. With only two significant lattice QCD calculations of the H-dibaryon binding energy at approximately the same lattice spacing, the forms of the chiral and continuum extrapolations to the physical point are not determined. In this brief report, we consider the constraints on the H-dibaryon imposed by two simple chiral extrapolations. In both instances, the extrapolation to the physical pion mass allows for a bound H-dibaryon or a near-threshold scattering state. Further lattice QCD calculations are required to clarify this situation.

Present Constraints on the H-dibaryon at the Physical Pointfrom Lattice QCD

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Chiral perturbation theory for heavy hadrons and chiral effective field theory for heavy hadronic molecules

The lightest charmed scalar meson is known as the ${D}_{0}^{*}(2300)$, which is one of the earliest new hadron resonances observed at modern $B$ factories. We show here that the parameters assigned to the lightest scalar $D$ meson are in conflict with the precise LHCb data of the decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$. On the contrary, these data can be well described by an unitarized chiral amplitude containing a much lighter charmed scalar meson, the ${D}_{0}^{*}(2100)$. We also extract the low-energy $S$-wave $D\ensuremath{\pi}$ phase of the decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}$ from the data in a model-independent way, and show that its difference from the $D\ensuremath{\pi}$ scattering phase shift can be traced back to an intermediate ${\ensuremath{\rho}}^{\ensuremath{-}}$ exchange. Our work highlights that an analysis of data consistent with chiral symmetry, unitarity, and analyticity is mandatory in order to extract the properties of the ground-state scalar mesons in the singly heavy sector correctly, in analogy to the light scalar mesons ${f}_{0}(500)$ and ${K}_{0}^{*}(700)$.

https://link.aps.org/pdf/10.1103/PhysRevLett.126.192001

Where Is the Lightest Charmed Scalar Meson

We consider the chiral Lagrangian with nucleon, isobar, and pion degrees of freedom. The baryon masses and the axial-vector form factor of the nucleon are derived at the one-loop level. We explore the impact of using on-shell baryon masses in the loop expressions. As compared to results from conventional chiral perturbation theory we find significant differences. An application to QCD lattice data is presented. We perform a global fit to the available lattice data sets for the baryon masses and the nucleon axial-vector form factor, and determine the low-energy constants relevant at $$\hbox {N}^3$$
 LO for the baryon masses and at $$\hbox {N}^2$$
 LO for the form factor. Partial finite-volume effects are considered. We point out that the use of on-shell masses in the loops results in non-analytic behavior of the baryon masses and the form factor as function of the pion mass, which becomes prominent for larger lattice volumes than presently used.

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On the axial-vector form factor of the nucleon and chiral symmetry

/pdf/interactions-of-charmed-mesons-with-light-pseudoscalar-3ay13zy6es.pdf

Interactions of Charmed Mesons with Light Pseudoscalar Mesons from Lattice QCD and Implications on the Nature of the D_{s0}^*(2317)

We consider the quark-mass dependence of the baryon octet and decuplet ground state masses. It is predicted that QCD dynamics implies a first order transition when increasing the strange quark mass from its chiral limit towards its physical value. Our claim relies on a global fit to the available QCD lattice data on such baryon masses. Quantitative results based on an application of the chiral SU(3) Lagrangian at N$^3$LO are discussed. We predict an anomalous sector of QCD where stable baryonic matter would be composed of lambda or anti-lambda particles rather than nucleons and anti-nucleons.

/pdf/on-a-first-order-transition-in-qcd-with-up-down-and-strange-3mlwbajfoh.pdf

On a first order transition in QCD with up, down and strange quarks

We perform an analysis of QCD lattice data on masses of charmed meson with J^P = 0^- and J^P =1^- quantum numbers. The quark-mass dependence of the data set is used to gain information on the size of counter terms in the chiral Lagrangian formulated with open-charm mesons. Of particular interest are those counter terms that are active in the exotic flavour sextet channel. A chiral expansion scheme is developed and applied to the lattice data set. An accurate reproduction of the lattice data based on ensembles of PACS-CS, MILC, ETMC and HSC with pion and kaon masses smaller than 600 MeV is achieved. It is argued that a unique set of low-energy parameters is obtainable only if additional information from an HSC ensemble on some scattering phase shifts is included in our global fits. Based on such low-energy parameters we find a clear signal for a member of the exotic flavour sextet states in the pi D phase shift, between the eta D and bar K D_s thresholds. A striking dependence of such phase shifts on the values of the up, down and strange quarks is predicted.

/pdf/on-chiral-extrapolations-of-coupled-channel-reaction-4plptfxpv4.pdf

On chiral extrapolations of coupled-channel reaction dynamics for charmed mesons

We consider the Higgs potential in generalizations of the Standard Model. The possibility of the potential to develop two almost degenerate minima is explored. This would imply that QCD matter at two distinct sets of quark masses is relevant for astrophysics and cosmology. If in the exotic minimum the QCD matter ground state is electromagnetically neutral, dark matter may consist of QCD matter and antimatter in bubbles of the Higgs field. We predict an abundance of $$\gamma $$ rays in the few MeV region as messengers of dark matter regions in space. In addition the ratio of dark matter to normal matter is expected to show a time dependence.

/pdf/a-generalized-higgs-potential-with-two-degenerate-minima-for-4l7zjy4pz5.pdf

A generalized Higgs potential with two degenerate minima for a dark QCD matter scenario

We consider the quark-mass dependence of the baryon octet and decuplet ground state masses. It is predicted that QCD dynamics implies a first order transition when increasing the strange quark mass from its chiral limit towards its physical value. Our claim relies on a global fit to the available QCD lattice data on such baryon masses. Quantitative results based on an application of the chiral SU(3) Lagrangian at N$$^3$$LO are discussed. We predict an anomalous sector of QCD where stable baryonic matter would be composed of $$\varLambda $$ or $$\bar{\varLambda }$$ particles rather than nucleons and anti-nucleons.

/pdf/on-a-first-order-transition-in-qcd-with-up-down-and-strange-391lb23z0v.pdf

We study the scattering of open-beauty mesons and Goldstone bosons as predicted by the chiral SU(3) Lagrangian. The impact of subleading-order chiral interactions to systems with ${J}^{P}={0}^{+}$ and ${J}^{P}={1}^{+}$ quantum numbers is worked out. We estimate the relevant low-energy coefficients from the open-charm sector, for which their values have been determined previously from sets of QCD lattice data. The leading-order heavy-quark symmetry-breaking effects are estimated by matching the $B$-meson ground-state chiral mass formula to the mass formula from the heavy-quark effective theory. We make refined predictions for the flavor antitriplet and sextet resonances that are generated dynamically by coupled-channel interactions.

/pdf/chiral-excitations-of-open-beauty-systems-3bb4j7ri7f.pdf

Xiao-Yu Guo

Papers

On a first order transition in QCD with up, down and strange quarks

On chiral extrapolations of coupled-channel reaction dynamics for charmed mesons

A generalized Higgs potential with two degenerate minima for a dark QCD matter scenario

On a first order transition in QCD with up, down and strange quarks

Chiral excitations of open-beauty systems