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Discovery of Matter Anti-matter Asymmetry in the Charm Sector

魅力领域物质反物质不对称性的发现

基本信息

批准号：
ST/K003410/1
负责人：
Marco Gersabeck
金额：
$ 28.13万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FK003410%2F1
关键词：
Discovery Matter Anti matter Asymmetry

项目摘要

Symmetries play an essential role in our understanding of the universe. Nature exhibits a stunning level of symmetry across all scales, from the bilateral symmetry of many animal's bodies to the mathematical symmetry of the fundamental physical laws. But only the imperfections of symmetries reveal the full picture. In astrophysics for example, the anisotropy of the cosmic microwave background radiation has given insight into the structure of the universe roughly 300,000 years after the big bang.At the Large Hadron Collider (LHC) we study the type of physics which governed the processes just a fraction of a second after the big bang. The LHC, located 100m underground just outside Geneva, collides protons at energies that have never previously been reached in a laboratory on earth. The smallest of the four large experiments at the LHC is known as LHCb, and is specifically designed to discover asymmetries in the behaviour of matter and antimatter.In our current understanding, matter consists of twelve fundamental particles: the six quarks (u, d, s, c, b, t ordered by increasing mass), and an electron with its heavier partners muon and tau and their three associated neutrinos. These interact by the exchange of so-called bosons, which are fundamental force carrying particles. The standard model of particle physics (SM) explains these matter interactions and has so far held up to all experimental tests. However, it fails to give explanations to basic questions like the reason why the t-quark is over 50,000 times heavier than the u-quark. Another is the puzzle that perfect symmetry would lead to equal amounts of matter and antimatter and the annihilation of the universe shortly after the big-bang. Questions like these tell us that the SM does not cover all aspects of fundamental interactions and therefore has to be extended.Nature has given us three special laboratories to study matter and antimatter interaction: neutral mesons (called K, B and D-meson), particles consisting of one quark (matter) and one antiquark (antimatter). Studies of the decays of these mesons have proven to be an excellent laboratory for discovering differences between the matter and anti-matter world. The studies of two of these systems (K and B mesons) have led to Nobel-prize winning breakthroughs. Together with a post-doctoral researcher, I will search for tiny differences of decays of D-mesons and anti-D-mesons. Half a year ago, scientists from the LHCb experiment have published a measurement showing a first indication for such a matter anti-matter asymmetry.Our group will focus on complementary measurements that are necessary to understand the origin of this asymmetry. Within the SM the relations between our measurements are predicted to high precision. Deviations from these predictions will unveil the presence of thus far unknown particles which are involved in this process.Particle physics research continues to lead to technological benefits to society, from the World Wide Web to medical imaging, but its true purpose will always be the search for fundamental understanding of our universe. My goal is to further this understanding, using the matter-antimatter asymmetry to reveal nature's beauty. And true beauty lies in imperfections.

对称性在我们对宇宙的理解中起着至关重要的作用。从许多动物身体的两侧对称到基本物理定律的数学对称，大自然在所有尺度上都展现出惊人的对称性。但只有不完美的对称性才能揭示出全貌。例如，在天体物理学中，宇宙微波背景辐射的各向异性让我们了解了大爆炸后大约30万年的宇宙结构。在大型强子对撞机（LHC）中，我们研究控制大爆炸后不到一秒的过程的物理类型。大型强子对撞机位于日内瓦郊外地下100米处，以地球上实验室从未达到的能量对质子进行碰撞。LHC的四个大型实验中最小的一个被称为LHCb，专门用于发现物质和反物质行为的不对称性。在我们目前的理解中，物质由12个基本粒子组成：6个夸克（u, d, s, c, b， t按质量递增顺序排列），一个电子及其较重的伙伴介子和τ以及它们的3个相关中微子。它们通过所谓玻色子的交换相互作用，玻色子是携带基本力的粒子。粒子物理学的标准模型（SM）解释了这些物质的相互作用，并且迄今为止经受住了所有的实验测试。然而，它无法解释一些基本问题，比如为什么t夸克比u夸克重5万多倍。另一个谜题是，完美的对称会导致等量的物质和反物质，以及大爆炸后不久宇宙的湮灭。像这样的问题告诉我们，SM并没有涵盖基本相互作用的所有方面，因此必须加以扩展。大自然给了我们三个专门的实验室来研究物质和反物质的相互作用：中性介子（称为K介子，B介子和d介子），由一个夸克（物质）和一个反夸克（反物质）组成的粒子。对介子衰变的研究已被证明是发现物质世界和反物质世界之间差异的绝佳实验室。对其中两个系统（K介子和B介子）的研究导致了获得诺贝尔奖的突破。我将与一名博士后研究员一起寻找d介子和反d介子衰变的微小差异。半年前，LHCb实验的科学家们发表了一项测量结果，首次显示了这种物质反物质不对称的迹象。我们的团队将专注于了解这种不对称起源所必需的互补测量。在SM内，我们的测量值之间的关系预测精度很高。这些预测的偏差将揭示迄今为止未知的粒子的存在，这些粒子参与了这一过程。从万维网到医学成像，粒子物理学研究不断为社会带来技术效益，但其真正目的永远是寻求对宇宙的基本理解。我的目标是进一步加深这种理解，利用物质与反物质的不对称来揭示自然之美。真正的美存在于不完美之中。