Title: Axial resonances a$$_{1}$$(1260), b$$_{1}$$(1235) and their decays from the lattice

Abstract

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 $$m_{b_1}^{res}=1.414(36)(^{+0}_{-83})$$.

Authors:

Lang, C. B. ^[1]; Leskovec, Luka ^[2]; Mohler, Daniel ^[3]; Prelovsek, Sasa ^[4]

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+ Show Author Affiliations

1. Univ. of Graz, Graz (Austria)
2. Jozef Stefan Institute, Ljubljana (Slovenia)
3. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
4. Jozef Stefan Institute, Ljubljana (Slovenia); Univ. of Ljubljana, Ljubljana (Slovenia)

Publication Date:

Mon Apr 28 00:00:00 EDT 2014

Research Org.:

Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), High Energy Physics (HEP)

OSTI Identifier:

1128720

Report Number(s):

FERMILAB-PUB-14-002-T
Journal ID: ISSN 1029-8479; arXiv eprint number arXiv:1401.2088

Grant/Contract Number:  

AC02-07CH11359

Resource 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 1029-8479

Publisher:

Springer Berlin

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; lattice QCD; QCD