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arXiv 1307.4337hep-ph
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NNLO非共振修正对e+ e碰撞产生顶对的阈值:端点奇异项

NNLO non-resonant corrections to threshold top-pair production from e+ e- collisions: Endpoint-singular terms

Bernd Jantzen, Pedro Ruiz-Femenía

摘要:

我们分析了在顶-反顶阈值附近的能量处,次引导非共振对e+ e- -> W+ W-b bbar截面的贡献。这些对应于相对于前导阶谐振结果的下一个到下一个前导阶(NNLO)校正。我们表明,这些修正产生1/10端点奇点,精确地取消了有限宽度的分歧所产生的共振生产的W+ W- b bbar的最终状态从壳衰变的顶夸克和反顶夸克在相同的顺序。我们还提供了(m_t/Lambda)^2、(m_t/Lambda)和(m_t/Lambda)^0 log(Lambda)项的解析结果,这些项主导了NNLO非共振修正全集的(Lambda/m_t)次方展开,其中Lambda是施加在b-W对不变质量上的一个既不太紧也不太松的切割(m_t Gamma_t <<Lambda ^2 << m_t^2)。

英文摘要:

We analyse the subleading non-resonant contributions to the e+ e- -> W+ W- b bbar cross section at energies near the top-antitop threshold. These correspond to next-to-next-to-leading-order (NNLO) corrections with respect to the leading-order resonant result. We show that these corrections produce 1/epsilon endpoint singularities which precisely cancel the finite-width divergences arising in the resonant production of the W+ W- b bbar final state from on-shell decays of the top and antitop quarks at the same order. We also provide analytic results for the (m_t/Lambda)^2, (m_t/Lambda) and (m_t/Lambda)^0 log(Lambda) terms that dominate the expansion in powers of (Lambda/m_t) of the complete set of NNLO non-resonant corrections, where Lambda is a cut imposed on the invariant masses of the b W pairs that is neither too tight nor too loose (m_t Gamma_t << Lambda^2 << m_t^2).

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