Higgs Searches at DZero

长期以来，粒子物理学家的目标是发现和理解宇宙的组成部分。多年来，这些积木的理论描述已经发展出来，它描述了基本粒子以及它们如何相互作用。这个理论被称为“标准模型”。虽然这个理论非常成功--许多测量结果都非常精确地证实了它的预测--但这个难题中仍然有缺失的部分。一个特别引人注目的悬而未决的问题是质量的起源。在最简单的形式中，标准模型不允许基本粒子，如夸克、电子、μ子、光子、胶子等拥有质量。这是一个真实的问题，因为实验证据压倒性地支持这些粒子中的一些是有质量的。对这一理论的修正基于许多人的工作，但最突出的是希格斯，温伯格和萨拉姆，提出了一种称为“自发电弱对称性破缺”的机制。也被称为希格斯机制，该理论的预测之一是存在一种称为希格斯玻色子的中性粒子。这不是唯一的可能性，另一类流行的理论进一步扩展了标准模型-称为“超对称性”，简称SUSY，预测存在许多新粒子-其中包括几个希格斯玻色子。通过寻找希格斯玻色子，人们可以找到支持或反驳这些理论的证据。目前的实验结果排除了质量小于质子115倍的希格斯玻色子的存在。在Tevatron-CDF和D-Zero的实验将在没有发现的情况下将这个极限扩展到180左右。这一点很重要，因为理论上的考虑沿着间接的实验证据表明，如果标准模型是正确的，或者最简单的超对称形式是正确的，那么希格斯粒子的质量应该小于这个极限。有几种不同的实验信号--或通道--可以用来寻找希格斯玻色子。拟议的研究将涉及对D-Zero实验中收集的数据集进行详细分析，其中一个通道（最敏感的通道）以及所有单个通道的结果的组合。通过结合来自许多渠道的结果，实现了观察希格斯玻色子的最佳可能机会。

It has long been the goal of particle physicists to discover and understand the building blocks of the universe. Over the years a theoretical description of these building blocks has been developed which describes the fundamental particles and how they interact with one another. The theory is called the 'Standard Model'. Although this theory has been extremely successful - with many measurements confirming its predictions to great precision - there are missing pieces in the puzzle. One particularly compelling open question is that of the origin of mass. In its simplest form the Standard Model does not allow for the fundamental particles such as quarks, electrons, muons, photons, gluons etc to possess mass. This is a real problem since experimental evidence overwhelmingly supports the proposition that some of these particles are massive. A modification to this theory based on the work of many but most prominently, Higgs, Weinberg and Salaam, proposes a mechanism known as 'Spontaneous Electroweak Symmetry Breaking'. Also known as the Higgs mechanism, one of the predictions of this theory is the existence of a neutral particle called the Higgs Boson. This is not the only possibility, another popular class of theories which further extend the Standard Model - called 'Super-Symmetry', or SUSY for short, predict the existence of many new particles - amongst them several Higgs bosons. By searching for Higgs boson(s) one can thus find evidence to support or refute these theories. Current experimental results rule out the existence of a Higgs boson with a mass less than around 115 times that of the proton. The experiments at the Tevatron - CDF and D-Zero will extend this limit to around 180 in the absence of discovery. This is important because theoretical considerations along with indirect experimental evidence suggest that if the Standard Model is correct or the simplest form of Supersymmetry is correct then the Higgs should have a mass less than this limit. There are several different experimental signatures - or channels - which can be used to search for the Higgs. The proposed research will involve the detailed analysis of the data-set collected at the D-Zero experiment in one of these channels (the single most sensitive) and the combination of the results from all the individual channels. By combining the results from many channels the best possible chance for observing the Higgs boson is achieved.