Light-front holographic QCD and exclusive B decays

光前全息 QCD 和独特的 B 衰变

• 批准号: SAPIN-2017-00031
• 负责人: Sandapen, Ruben
• 金额: $ 1.09万
• 依托单位: Mount Allison University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=675584
• 关键词: Light; front; holographic; QCD; exclusive

The Standard Model (SM) of particle physics has successfully withstood decades of intensive testing culminating in the long-awaited discovery of the Higgs boson in 2012 at the LHC. Yet, we know that the SM is incomplete since it does not accommodate gravity and neither does it account for neutrino oscillations, dark matter and for the matter/antimatter asymmetry. Despite intensive efforts, to this date no New Physics (NP) discoveries have been made at the LHC. However, an intriguing number of anomalies, i.e. discrepancies between the data and SM predictions, have been reported in rare exclusive B decays. These are decays of the B meson (containing a heavy b quark) to a lighter meson (no b quark) accompanied by a photon or a pair of leptons. These exclusive decays are relatively clean to measure experimentally but the theory behind them is challenging. There are two reasons for this: first, although we are able to compute (using perturbation theory) the underlying b-quark decay in the SM, our final predictions for observables have a residual dependence on an energy scale called the renormalization scale thus introducing a systematic uncertainty. Secondly, quarks and gluons are permanently confined into mesons and this has to be carefully accounted for using non-perturbative methods.******The LHC Run II has started in 2015 and in the next five years, the precision of the data is expected to at least double. These more precise LHC data will be complemented by independent measurements from the Belle II detector at the SuperKEKB collider in Japan scheduled to start taking data in 2017. Clearly theory input will be essential to interpret the forthcoming data as well as to guide future experiments. In this research, we aim to increase the reliability of our theoretical predictions for the rare exclusive B decays in two ways. First, we are applying a new theoretical procedure, the so-called Principle of Maximum Conformality, to reduce the renormalization scale uncertainty. Thus, our research can help to identify unambiguously NP signals in these rare decays. Secondly, we are using an alternative (and complementary) non-perturbative method, known as light-front holography, to account for the confinement of quarks and gluons in mesons.******Besides its phenomenological applications, light-front holography in itself is worth investigating. It is an example of what are known as holographic dualities, i.e. mathematical equivalences between strongly-coupled quantum theories in physical spacetime and weakly-coupled gravitational theories in higher dimensional spaces. It may well be that these dualities have a deeper physical meaning aside from being mere mathematical tools. In this research, we also aim to explore the underlying links between light-front holography and another standard non-perturbative method. This will help to understand better the unsolved problem of quark confinement in hadrons.

粒子物理学的标准模型（SM）成功地在2012年在LHC上发现了人们期待已久的希格斯玻色子（Higgs Boson）的几十年进行了深入的测试。然而，我们知道SM不完全不适合重力，并且它也无法解释中微子振荡，暗物质和物质/反物质不对称。尽管进行了密集的努力，但此日还没有在LHC上发现新的物理（NP）。但是，在罕见的B衰减中，已经报道了许多有趣的异常，即数据和SM预测之间的差异。这些是B Meson（包含重B夸克）的衰变，伴有光子或一对瘦素。这些独家衰减相对干净，可以实验测量，但是它们背后的理论具有挑战性。造成两个原因有两个：首先，尽管我们能够计算SM中的基本B Quark衰减（使用扰动理论），但我们对可观察物的最终预测对称为重新归一化量表的能量量表具有残差依赖性，从而引入了系统的不确定性。其次，夸克和胶子被永久限制在介子中，必须仔细考虑使用非扰动方法。****** ****** LHC Run II已于2015年开始，在接下来的五年中，数据的精度预计至少要两倍。这些更精确的LHC数据将通过日本SuperkekB撞机的独立测量来补充，该测量器计划于2017年开始获取数据。显然，理论输入对于解释即将到来的数据以及指导未来的实验至关重要。在这项研究中，我们旨在通过两种方式提高对罕见的独家B衰减的理论预测的可靠性。 首先，我们采用了一种新的理论程序，即最大相同性的所谓原理，以减少重新归一化量表的不确定性。因此，我们的研究可以帮助识别这些罕见衰变中明确的NP信号。其次，我们正在使用一种替代性（和补充）非扰动方法，称为轻型全息图，以说明介体中夸克和胶子的限制。******除了其现象学应用外，还值得研究光前的全息图。这是一个被称为全息偶性的例子，即物理时空中强耦合的量子理论与较高维空间中弱耦合的重力理论之间的数学等价。除了仅仅是数学工具之外，这些二元性可能还具有更深的物理意义。在这项研究中，我们还旨在探索轻瞬态和另一种标准的非扰动方法之间的潜在联系。这将有助于更好地理解Hadron中未解决的Quark禁闭问题。