Axial resonances a$$_{1}$$(1260), b$$_{1}$$(1235) and their decays from the lattice
The light axialvector 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 swave 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 BreitWigner 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 $$m_{b_1}^{res}=1.414(36)(^{+0}_{83})$$.
 Authors:

^{[1]};
^{[2]};
^{[3]};
^{[4]}
 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)
 Publication Date:
 Report Number(s):
 FERMILABPUB14002T
Journal ID: ISSN 10298479; arXiv eprint number arXiv:1401.2088
 Grant/Contract Number:
 AC0207CH11359
 Type:
 Accepted Manuscript
 Journal Name:
 Journal of High Energy Physics (Online)
 Additional Journal Information:
 Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2014; Journal Issue: 4; Journal ID: ISSN 10298479
 Publisher:
 Springer Berlin
 Research Org:
 Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), High Energy Physics (HEP) (SC25)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; lattice QCD; QCD
 OSTI Identifier:
 1128720
Lang, C. B., Leskovec, Luka, Mohler, Daniel, and Prelovsek, Sasa. Axial resonances a$_{1}$(1260), b$_{1}$(1235) and their decays from the lattice. United States: N. p.,
Web. doi:10.1007/JHEP04(2014)162.
Lang, C. B., Leskovec, Luka, Mohler, Daniel, & Prelovsek, Sasa. Axial resonances a$_{1}$(1260), b$_{1}$(1235) and their decays from the lattice. United States. doi:10.1007/JHEP04(2014)162.
Lang, C. B., Leskovec, Luka, Mohler, Daniel, and Prelovsek, Sasa. 2014.
"Axial resonances a$_{1}$(1260), b$_{1}$(1235) and their decays from the lattice". United States.
doi:10.1007/JHEP04(2014)162. https://www.osti.gov/servlets/purl/1128720.
@article{osti_1128720,
title = {Axial resonances a$_{1}$(1260), b$_{1}$(1235) and their decays from the lattice},
author = {Lang, C. B. and Leskovec, Luka and Mohler, Daniel and Prelovsek, Sasa},
abstractNote = {The light axialvector 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 swave 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 BreitWigner 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 $m_{b_1}^{res}=1.414(36)(^{+0}_{83})$.},
doi = {10.1007/JHEP04(2014)162},
journal = {Journal of High Energy Physics (Online)},
number = 4,
volume = 2014,
place = {United States},
year = {2014},
month = {4}
}