62 research outputs found

### Charmed Hadron Spectrum and Interactions

Studying hadrons containing heavy quarks in lattice QCD is challenging mainly due to finite lattice spacing effects. to control the discretization errors, mQa is required to be much less than 1, where mQ is the quark mass and a is the lattice spacing. For currently accessible lattice spacings, the charm quark mass doesn\u27t satisfy this requirement. One approach to simulate heavy quarks on the lattice is non-relativestic QCD, which treats heavy quark as a static source and expand the lattice quark action in powers of 1mQa . Unfortunately, the charm quark is not heavy enough to justify this expansion. An other is Heavy Quark Effective Theory (HQET) matched on QCD. Non-relativestic QCD and HQET are mainly used for bottom quark. Relativistic heavy-quark action, which incorporates both small mass and large mass formulations, is better suited to study the charm quark sector. The discretization errors can be reduced systematically following Symanzik improvement.;In this work, we use the relativistic heavy quark action to study the charmed hadron spectrum and interactions in full lattice QCD. For the light quarks we use domain-wall fermions in the valence sector and improved Kogut-Susskind sea quarks. The parameters in the heavy quark action are tuned to reduce lattice artifacts and match the charm quark mass and the action is tested by calculating the low-lying charmonium spectrum.;We compute the masses of the spin-1/2 singly and doubly charmed baryons. For the singly charmed baryons, our results are in good agreement with experiment within our systematics. For the doubly charmed baryon xicc we find the isospin-averaged mass to be MXcc = 3665 +/- 17 +/- 14+0-78 MeV; the three given uncertainties are statistical, systematic and an estimate of lattice discretization errors, respectively. In addition, we predict the mass splitting of the (isospin-averaged) spin-1/2 O cc with the xicc to be MWcc-MXcc = 98 +/- 9 +/- 22 +/- 13 MeV (in this mass splitting, the leading discretization errors are also suppressed by SU(3) symmetry). Combining this splitting with our determination of MXcc leads to our prediction of the spin-1/2 Occ mass, MWcc = 3763 +/- 19 +/- 26+13-79 MeV.;We calculate the scattering lengths of the charmed mesons with the light pseudoscalar mesons. The calculation is performed for four different light quark masses and extrapolated to the physical point using chiral perturbation formulas to next-to-next-to-leading order. The low energy constants are determined and used to make predictions. We find relatively strong attractive interaction in DK channels, which is closely related to the structure of DsJ(2317) state. The scattering of charmonium with light hadrons is also studied. Particularly, we find very weak attractive interaction between J/Psi and nucleon, in this channel the dominate interaction is attractive gluonic van der Walls and it could lead to molecular-like bound states

### A Numerical Study of Improved Quark Actions on Anisotropic Lattices

Tadpole improved Wilson quark actions with clover terms on anisotropic
lattices are studied numerically.
Using asymmetric lattice volumes, the pseudo-scalar meson dispersion
relations are measured for 8 lowest lattice momentum modes with quark mass
values ranging from the strange to the charm quark with various values of the
gauge coupling $\beta$ and 3 different values of the bare speed of light
parameter $\nu$. These results can be utilized to extrapolate or interpolate to
obtain the optimal value for the bare speed of light parameter $\nu_{opt}(m)$
at a given gauge coupling for all bare quark mass values $m$. In particular,
the optimal values of $\nu$ at the physical strange and charm quark mass are
given for various gauge couplings.
The lattice action with these optimized parameters can then be used to study
physical properties of hadrons involving either light or heavy quarks.Comment: 22 pages, 7 figures, 2 tables. Analysis greatly modified compared
with previous versio

### Tetraquarks, hadronic molecules, meson-meson scattering and disconnected contributions in lattice QCD

There are generally two types of Wick contractions in lattice QCD
calculations of a correlation function --- connected and disconnected ones. The
disconnected contribution is difficult to calculate and noisy, thus it is often
neglected. In the context of studying tetraquarks, hadronic molecules and
meson-meson scattering, we show that whenever there are both connected and
singly disconnected contractions, the singly disconnected part gives the
leading order contribution, and thus should never be neglected. As an explicit
example, we show that information about the scalar mesons sigma, f0(980),
a0(980) and kappa will be lost when neglecting the disconnected contributions.Comment: 9 pages, 2 figure

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

We study the scattering of light pseudoscalar mesons ($\pi$, $K$) off charmed
mesons ($D$, $D_s$) in full lattice QCD. The S-wave scattering lengths are
calculated using L\"uscher's finite volume technique. We use a relativistic
formulation for the charm quark. For the light quark, we use domain-wall
fermions in the valence sector and improved Kogut-Susskind sea quarks. We
calculate the scattering lengths of isospin-3/2 $D\pi$, $D_s\pi$, $D_sK$,
isospin-0 $D\bar{K}$ and isospin-1 $D\bar{K}$ channels on the lattice. For the
chiral extrapolation, we use a chiral unitary approach to next-to-leading
order, which at the same time allows us to give predictions for other channels.
It turns out that our results support the interpretation of the
$D_{s0}^*(2317)$ as a $DK$ molecule. At the same time, we also update a
prediction for the isospin breaking hadronic decay width
$\Gamma(D_{s0}^*(2317)\to D_s\pi)$ to $(133\pm22)$ keV.Comment: 22 pages, 5 figures; a typo in Table II corrected (for the
coefficients of the NLO amplitudes

### Hadron-Hadron Interactions from $N_f=2+1+1$ Lattice QCD: isospin-1 $KK$ scattering length

We present results for the interaction of two kaons at maximal isospin. The
calculation is based on $N_f=2+1+1$ flavour gauge configurations generated by
the European Twisted Mass Collaboration with pion masses ranging from about
$230$ to $450\,\textrm{MeV}$ at three values of the lattice spacing. The
elastic scattering length $a_0^{I=1}$ is calculated at several values of the
bare strange and light quark masses. We find $M_K a_0 =
-0.385(16)_{\textrm{stat}} (^{+0}_{-12})_{m_s}(^{+0}_{-5})_{Z_P}(4)_{r_f}$ as
the result of a combined extrapolation to the continuum and to the physical
point, where the first error is statistical, and the three following are
systematical. This translates to $a_0 =
-0.154(6)_{\textrm{stat}}(^{+0}_{-5})_{m_s}
(^{+0}_{-2})_{Z_P}(2)_{r_f}\,\textrm{fm}$.Comment: 28 pages, 18 tables, 14 figure

### Meson-meson scattering lengths at maximum isospin from lattice QCD

We summarize our lattice QCD determinations of the pion-pion, pion-kaon and
kaon-kaon s-wave scattering lengths at maximal isospin with a particular focus
on the extrapolation to the physical point and the usage of next-to-leading
order chiral perturbation theory to do so. We employ data at three values of
the lattice spacing and pion masses ranging from around 230 MeV to around 450
MeV, applying Luescher's finite volume method to compute the scattering
lengths. We find that leading order chiral perturbation theory is surprisingly
close to our data even in the kaon-kaon case for our entire range of pion
masses.Comment: 10 pages, 8 figures, Presented at the 9th International Workshop on
Chiral Dynamics, Sept. 17-21, 2018, Duke University, Durham, NC, USA ,
submitted to PoS, (C18-09-17.6). Funding acknowledgements added in v2
replacement, comma added in abstract. In v3 replacement, corrected typo in
equation 6.2 which was referring to the pion-kaon reduced mass instead of the
pion mas

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