Hindered M 1 Radiative Decay of Υ ( 2 S ) from Lattice NRQCD
Hindered M 1 Radiative Decay of Υ ( 2 S ) from Lattice NRQCD
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发表时间：
2018
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通讯作者：
Ciaran Hughes;R. Dowdall;C. Davies;R. Horgan;G. Hippel;M. Wingate
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作者：
Ciaran Hughes;R. Dowdall;C. Davies;R. Horgan;G. Hippel;M. Wingate
Ciaran Hughes, a Rachel J. Dowdall, Christine T. H. Davies, Ronald R. Horgan， Georg von Hippel和Matthew Wingate （HPQCD合作）b剑桥大学应用数学与理论物理系，剑桥cb30wa，英国SUPA，格拉斯哥大学物理与天文学院，格拉斯哥，g128qq，英国美因茨大学<s:1>物理研究所，Becherweg 45,55099美因茨，本文用晶格非相对论性QCD计算了受阻态M1 Υ（2S）→ηb(1S)γ衰变率。计算包括通过夸克相对速度中的O(v)对NRQCD作用的自旋相关相对论修正，通过夸克磁矩介导跃迁的先导电流的相对论修正，对先导自旋-磁耦合的辐射修正以及首次完整的误差估计。我们还在多个晶格间距值下使用胶子场系综，所有这些都包括u， d， s和c夸克真空极化。分支分数的计算结果为B（Υ（2S）→ηb(1S)γ） = 5.4（1.8）× 10−4，与目前的实验值一致。
Ciaran Hughes, a Rachel J. Dowdall, Christine T. H. Davies, Ronald R. Horgan, Georg von Hippel, and Matthew Wingate (HPQCD Collaboration) b Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK Institut für Kernphysik, University of Mainz, Becherweg 45, 55099 Mainz, Germany We present a calculation of the hindered M1 Υ(2S) → ηb(1S)γ decay rate using lattice nonrelativistic QCD. The calculation includes spin-dependent relativistic corrections to the NRQCD action through O(v) in the quark’s relative velocity, relativistic corrections to the leading order current which mediates the transition through the quark’s magnetic moment, radiative corrections to the leading spin-magnetic coupling and for the first time a full error budget. We also use gluon field ensembles at multiple lattice spacing values, all of which include u, d, s and c quark vacuum polarisation. Our result for the branching fraction is B(Υ(2S)→ ηb(1S)γ) = 5.4(1.8)× 10−4, which agrees with the current experimental value.