Axial resonances a$$_{1}$$(1260), b$$_{1}$$(1235) and their decays from the lattice
- Univ. of Graz, Graz (Austria)
- Jozef Stefan Institute, Ljubljana (Slovenia)
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Jozef Stefan Institute, Ljubljana (Slovenia); Univ. of Ljubljana, Ljubljana (Slovenia)
The light axial-vector resonances $$a_1(1260)$$ and $$b_1(1235)$$ are explored in Nf=2 lattice QCD by simulating the corresponding scattering channels $$\rho\pi$$ and $$\omega\pi$$. Interpolating fields $$\bar{q} q$$ and $$\rho\pi$$ or $$\omega\pi$$ are used to extract the s-wave phase shifts for the first time. The $$\rho$$ and $$\omega$$ are treated as stable and we argue that this is justified in the considered energy range and for our parameters $$m_\pi\simeq 266~$$MeV and $$L\simeq 2~$$fm. We neglect other channels that would be open when using physical masses in continuum. Assuming a resonance interpretation a Breit-Wigner fit to the phase shift gives the $$a_1(1260)$$ resonance mass $$m_{a1}^{res}=1.435(53)(^{+0}_{-109})$$ GeV compared to $$m_{a1}^{exp}=1.230(40)$$ GeV. The $$a_1$$ width $$\Gamma_{a1}(s)=g^2 p/s$$ is parametrized in terms of the coupling and we obtain $$g_{a_1\rho\pi}=1.71(39)$$ GeV compared to $$g_{a_1\rho\pi}^{exp}=1.35(30)$$ GeV derived from $$\Gamma_{a1}^{exp}=425(175)$$ MeV. In the $$b_1$$ channel, we find energy levels related to $$\pi(0)\omega(0)$$ and $$b_1(1235)$$, and the lowest level is found at $$E_1 \gtrsim m_\omega+m_\pi$$ but is within uncertainty also compatible with an attractive interaction. Lastly, assuming the coupling $$g_{b_1\omega\pi}$$ extracted from the experimental width we estimate $$m_{b_1}^{res}=1.414(36)(^{+0}_{-83})$$.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- Grant/Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1128720
- Report Number(s):
- FERMILAB-PUB-14-002-T; arXiv eprint number arXiv:1401.2088
- Journal Information:
- Journal of High Energy Physics (Online), Vol. 2014, Issue 4; ISSN 1029-8479
- Publisher:
- Springer BerlinCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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