Transition of $\rho \to \pi \gamma$ in Lattice QCD

Abstract

With the ongoing experimental interest in exploring the excited hadron spectrum, evaluations of the matrix elements describing the formation and decay of such states via radiative processes provide us with an important connection between theory and experiment. In particular, determinations obtained via the lattice allow for a direct comparison of QCD-expectation with experimental observation. Here we present the first light quark determination of the $\rho \to \pi \gamma$ transition form factor from lattice QCD using dynamical quarks. Using the PACS-CS 2+1 flavour QCD ensembles we are able to obtain results across a range of masses, to the near physical value of $m_{\pi }=157$ MeV. An important aspect of our approach is the use of variational methods to isolate the desired QCD eigenstate. For low-lying states, such techniques facilitate the removal of excited state contributions. In principle the method enables one to consider arbitrary eigenstates. We find our results are in accord with the non-relativistic quark model for heavy masses. In moving towards the light-quark regime we observe an interesting quark mass dependence, contrary to the quark model expectation. Comparison of our light-quark result with experimental determinations highlights a significant discrepancy suggesting that disconnected sea-quark loop contributions may play a significant role in fully describing this process.

9 pages, 5 figures and 1 table

References in corpus (5)

• Multichannel one-to-two transition amplitudes in a finite volume
• Exotic and excited-state radiative transitions in charmonium from lattice QCD
• Pseudoscalar and vector meson form factors from lattice QCD
• Light Meson Form Factors at near Physical Masses
• Excited meson radiative transitions from lattice QCD using variationally optimized operators

Cited by in corpus (13)

• Hadronic molecules
• The resonant ${\pi }^{+}\gamma \to {\pi }^{+}{\pi }^0$ amplitude from Quantum Chromodynamics
• The $\pi \gamma \to \pi \pi$ transition and the $\rho$ radiative decay width from lattice QCD
• Magnetic properties of ground-state mesons
• Nucleon matrix elements using the variational method in lattice QCD
• Light-quark contributions to the magnetic form factor of the Lambda(1405)
• Elastic Form Factors of Nucleon Excitations in Lattice QCD
• Theoretical tools for neutrino scattering: interplay between lattice QCD, EFTs, nuclear physics, phenomenology, and neutrino event generators
• Constraining beyond the Standard Model nucleon isovector charges
• Rho-pion transition form factors in the $k_T$ factorization formulism revisited
• $\Delta I=3/2$ and $\Delta I=1/2$ channels of $K\to \pi \pi$ decay at the physical point with periodic boundary conditions
• Hadron Structure and Spectrum from the Lattice
• Singlet baryons in the graded symmetry approach to partially quenched QCD