W-pair production at future lepton colliders

未来轻子对撞机的 W 对生产

• 批准号: 493103835
• 负责人: Professor Dr. Stefan Dittmaier
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/493103835?language=en
• 关键词: pair; production; future; lepton; colliders

Future e+e- colliders, such as the ILC or FCC-ee, offer fantastic possibilities for high-precision measurements to challenge the Standard Model. For instance, from a scan of the total WW production cross section over its energy threshold, the W-boson mass could be determined with a precision of 3MeV (ILC) and even 0.5-1MeV (FCC-ee), respectively.This research project aims at providing the needed highly precise predictions for the cross section of the process e+e- -> WW -> 4fermions (ee4f) to account for the great expected experimental accuracy, in particular in the WW threshold region where sub-permille precision of the total cross section is required.For WW analyses at LEP2, a precision of ~2% at threshold and of ~0.5% above was sufficient, so that radiative corrections of next-to-leading order (NLO) were needed only in the W resonance regions, leading to the concept of the "double-pole approximation". Some years after LEP2, the state-of-the-art predictions were improved in two ways: Firstly, the NLO corrections for the ee4f process were calculated, after solving problems with the gauge-invariant treatment of the W resonances and in the evaluation of multi-leg one-loopamplitudes. Secondly, the complete NLO corrections and some leading higher-order terms were calculated within an Effective Field Theory (EFT) designed to describe the WW threshold region.To reach the ultimately required precision in the WW threshold region, the ee4f and EFT predictions have to be merged and extended. The ee4f calculation provides the necessary precision in the off-shell tails of the cross section, while the EFT offers the possibility to go beyond NLO in the W resonance regions. Significant improvements are needed in either direction. In the ee4f branch all four-fermion final states have to be treated in full NLO precision, including all process-specific interferences, and effects from initial-state radiation have to be included beyond NLO. The recent progress in automated NLO calculations is vital to achieve this. The EFT calculation has to be extended to the complete next-to-next-to-leading order (NNLO) level, posing conceptual and technical challenges. The conceptual progress in the EFT at NNLO will provide several spin-off results that are useful in similar calculations, e.g. for heavy-quark pair production. The technical challenges in the hard two-loop corrections can only be mastered owing to the dramatic progress in multi-loop calculations of recent years. The final outcome of the planned project will be a Monte Carlo program merging the refinedNLO ee4f and NNLO EFT parts in the WW threshold region with a smooth transition to NLO ee4f predictions at intermediate and high energies.

ILC或FCC-EE等未来的E+E-Colliders为高精度测量提供了奇妙的可能性，以挑战标准模型。例如，从扫描WW总生产横截面的能量阈值中，可以分别以3mev（ILC），甚至0.5-1MEV（FCC-EE）的精度确定W-boson质量，该研究项目旨在为所需的高度精确预测提供了对E+e-e-e-e-e-e-> w-> ew-> ee ee的高度准确预测（EE4F）的高度精确预测（EE4F），以提供高度精确的预测（EE4F）。 WW阈值区域需要总横截面的子层精度。对于LEP2进行WW分析，在阈值时的精度约为2％，高于0.5％的ww分析足够，因此仅在W Resonance区域仅需要对近代领导顺序（NLO）进行辐射校正，才能在W resonance区域中进行概念，从而概念“双杆近似”。 LEP2后的几年，在解决了量规不变的处理问题和多级单级单层层次的评估后，计算了EE4F工艺的NLO校正。其次，在旨在描述WW阈值区域的有效场理论（EFT）中计算了完整的NLO校正和某些领先的高阶项。要在WW阈值中达到最终所需的精度，必须合并和扩展EE4F和EFT预测。 EE4F计算提供了横截面的脱离尾部的必要精度，而EFT则提供了在W共振区域内超越NLO的可能性。这两个方向都需要进行重大改进。在EE4F分支中，所有四个fermion的最终状态都必须全NLO精度处理，包括所有特定过程的干扰，初始状态辐射的影响必须包括NLO以外。自动化计算的最新进展对于实现这一目标至关重要。 EFT计算必须扩展到完整的近代到领先顺序（NNLO）级别，从而带来概念和技术挑战。 NNLO在EFT中的概念进展将提供几种在类似计算中有用的衍生结果，例如用于夸克对的生产。由于近年来多循环计算的巨大进展，硬性两层校正中的技术挑战只能掌握。计划项目的最终结果将是一项蒙特卡洛计划，将WW阈值区域中的精制EE4F和NNLO EFT零件融合在一起，并在中间和高能量时平稳过渡到NLO EE4F预测。