arXiv subjects

Luka Leskovec

Publications and source records attributed to Luka Leskovec.

39 records · Page 3Linked to original sources

arXiv2013

Evidence for X(3872) from DD* scattering on the lattice

A candidate for the charmonium(like) state X(3872) is found 11 +/- 7 MeV below the DD* threshold using dynamical Nf=2 lattice simulation with J^PC=1^++ and I=0. This is the first lattice simulation that establishes a candidate for X(3872) in addition to the nearby scattering states D D* and J/psi omega, which inevitably have to be present in dynamical QCD. We extract large and negative DD* scattering length a_0=-1.7 +/- 0.4 fm and the effective range r_0=0.5 +/- 0.1 fm, but their reliable determination will have to wait for a simulation on a larger volume. In I=1 channel, only the D D* and J/psi rho scattering states are found and no candidate for X(3872). This is in agreement with the interpretation that X(3872) is dominantly I=0, while its small I=1 component arises solely from the isospin breaking and is therefore absent in our simulation with m_u=m_d.

hep-lat↗

arXiv2012

K pi scattering for isospin 1/2 and 3/2 in lattice QCD

We simulate K pi scattering in s-wave and p-wave for both isospins I=1/2, 3/2 using quark-antiquark and meson-meson interpolating fields. We extract the elastic phase shifts delta at several values of the K-pi relative momenta. The resulting phases exhibit qualitative agreement with the experimental phases in all four channels. We express the s-wave phase shifts near threshold in terms of the scattering length and the effective range. Our K pi system has zero total momentum and is simulated on a single ensemble with two dynamical quarks, so results apply for mpi=266 MeV and mK=552 MeV in our simulation. The backtracking contractions in both I=1/2 channels are handled by the use of Laplacian-Heavyside smeared quarks within the distillation method. Elastic phases are extracted from the energy levels using Luscher's relations. In all four channels we observe the expected K(n)pi(-n) scattering states, which are shifted due to the interaction. In both attractive I=1/2 channels we observe additional states that are related to resonances; we attribute them to K_0^*(1430) in s-wave and K*(892), K*(1410) and K*(1680) in p-wave.

hep-lat↗

arXiv2012

Scattering phase shifts for two particles of different mass and non-zero total momentum in lattice QCD

We derive the relation between the scattering phase shift and the two-particle energy in the finite box, which is relevant for extracting the strong phase shifts in lattice QCD. We consider elastic scattering of two particles with different mass and with non-zero total momentum in the lattice frame. This is a generalization of the Luscher formula, which considers zero total momentum, and the generalization of Rummukainen-Gottlieb's formula, which considers degenerate particles with non-zero total momentum. We focus on the most relevant total momenta in practice, i.e. P=(2π/L) e_z and P=(2π/L) (e_x+e_y) including their multiples and permutations. We find that the P-wave phase shift can be reliably extracted from the two-particle energy if the phase shifts for l>=2 can be neglected, and we present the corresponding relations. The reliable extraction of S-wave phase shift is much more challenging since delta(l=0) is always accompanied by delta(l=1) in the phase shift relations, and we propose strategies for estimating delta(l=0). We also propose the quark-antiquark and meson-meson interpolators that transform according the considered irreducible representations.

hep-lat↗