How hot will it get? Heavy quarks in the quark-gluon plasma

天气会有多热？

• 批准号: ST/J000043/1
• 负责人: Gert Aarts
• 金额: $ 0.84万
• 依托单位: Swansea University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FJ000043%2F1
• 关键词: How; hot; will; get; Heavy

What happens to quarks, the building blocks of matter, when they are put under the extreme conditions of high temperature? Quarks interact via the strong nuclear force, one of the four fundamental forces of Nature, described by Quantum Chromodynamics or QCD, and mediated by gluons. While under normal conditions quarks and gluons are confined into hadrons, such as protons, neutrons and pions, when the temperature is raised a phase transition to a deconfined phase occurs, and matter is organized as a plasma of quarks and gluons, rather than as a hadronic system. The high-temperature phase is known as the quark-gluon plasma (QGP). The critical temperature where the transition occurs is of the order of 175 MeV, or 2 x 10^(12) K, not readily available in your lab! In fact, the only time when the Universe was at such a high temperature, was a very long time ago, right after the Big Bang. Luckily for us, in the past decade such high temperatures have been recreated, albeit only for a very short time, by colliding heavy ions (lead and gold) together in heavy ion collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory (NY, USA). This has led to remarkable insight in the dynamics of strongly interacting matter just above the transition temperature, which has been dubbed the perfect fluid. These experiments are currently taken to the next level by the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland. In fact, in November of last year, the first heavy ion collisions took place at CERN, an event eagerly awaited for by experimental and theoretical physicists. How can the temperature of the quark-gluon plasma be estimated? Almost 25 years ago, it was proposed by two theoretical physicists, Tetsuo Matsui from Japan and Helmut Satz from Germany, that quarkonia, states built from one quark and one anti-quark, can provide insight into this. It was argued that various quarkonium states melt at different temperatures, or in other words, quarkonium states act as a thermometer! In order to make this precise, it is necessary to know at which temperature a particular state will melt. And this is where our research comes in. Since quarks and gluons are strongly interacting, it is not easy to compute melting temperatures with pen and paper. In fact, the only way to take into account all interactions is by using a numerical approach, known as lattice QCD. Here quarks and gluons are placed on a spacetime lattice and different arrangements of quarks and gluons have to be considered to find the preferred configurations. It turns out that at low temperatures configurations are preferred where the quarks are close together, i.e. confined, whereas at high temperature, quarks can be far apart, i.e. deconfined. By scanning over a range of temperatures, the melting temperatures of different states can then be deduced. In our work we propose a new way to find these melting temperatures. By relying on the fact that heavy quarks move slowly, we can ignore Einstein's Theory of Special Relativity for the quarks and use a non-relativistic approximation. It turns out that this simplifies the analysis considerably. Since the LHC has just started its first heavy ion collisions a few months ago, it is a particularly exciting time to work on this topic at this moment. Hopefully it will provide new insight into one of the fundamental forces ruling our Universe.

当夸克被置于高温的极端条件下时，物质的基石会发生什么？夸克通过强核力相互作用，强核力是自然界四种基本力之一，由量子色动力学或QCD描述，并由胶子介导。在正常条件下，夸克和胶子被限制在强子中，如质子、中子和π介子，当温度升高时，会发生向去禁闭相的相变，物质被组织成夸克和胶子的等离子体，而不是强子系统。高温阶段被称为夸克-胶子等离子体（QGP）。发生跃迁的临界温度大约是175 MeV，或2 × 10^（12）K，这在你的实验室里是不容易得到的！事实上，宇宙唯一一次处于如此高的温度，是在很久以前，就在大爆炸之后。幸运的是，在过去的十年里，这样的高温已经被重新创造出来，尽管只有很短的时间，通过在布鲁克海文国家实验室（纽约，美国）的相对论重离子对撞机中将重离子（铅和金）碰撞在一起。这导致了对强相互作用物质动力学的显着洞察力，该物质被称为完美流体。目前，位于瑞士日内瓦的欧洲核子研究中心（CERN）的大型强子对撞机（LHC）将这些实验提升到了一个新的水平。事实上，去年11月，欧洲核子研究中心发生了第一次重离子碰撞，这是实验物理学家和理论物理学家热切期待的事件。如何估计夸克胶子等离子体的温度？大约25年前，日本的松井哲夫（Tetsuo Matsui）和德国的赫尔穆特·萨茨（Helmut Satz）两位理论物理学家提出，夸克尼亚（quarkonia），即由一个夸克和一个反夸克构成的状态，可以提供对此的洞察力。有人认为，不同的夸克偶素状态在不同的温度下熔化，或者换句话说，夸克偶素状态充当温度计！为了使这一点精确，有必要知道特定状态在哪个温度下会熔化。这就是我们的研究的用武之地。由于夸克和胶子之间存在强烈的相互作用，因此用笔和纸计算熔化温度并不容易。事实上，考虑所有相互作用的唯一方法是使用数值方法，称为格点QCD。在这里，夸克和胶子被放置在时空晶格上，必须考虑夸克和胶子的不同排列，以找到优选的构型。事实证明，在低温下，夸克靠近在一起的配置是优选的，即被限制，而在高温下，夸克可以远离，即解除限制。通过在一定温度范围内扫描，可以推断出不同状态的熔化温度。在我们的工作中，我们提出了一种新的方法来找到这些熔化温度。依靠重夸克运动缓慢的事实，我们可以忽略爱因斯坦的夸克狭义相对论，而使用非相对论近似。事实证明，这大大简化了分析。由于大型强子对撞机几个月前刚刚开始了它的第一次重离子碰撞，这是一个特别令人兴奋的时刻来研究这个话题。希望它能为统治我们宇宙的基本力量之一提供新的见解。

项目成果

Spectrum-doubled heavy vector bosons at the LHC

• DOI: 10.1007/jhep01(2016)109
• 发表时间: 2016-01
• 期刊: Journal of High Energy Physics
• 影响因子: 5.4
• 作者: T. Appelquist;Yang Bai;J. Ingoldby;M. Piai

The quark condensate in multi-flavour QCD - planar equivalence confronting lattice simulations

多味QCD中的夸克凝聚——面对晶格模拟的平面等价

• DOI: 10.1016/j.physletb.2014.12.035
• 发表时间: 2015
• 期刊: Physics Letters B
• 影响因子: 4.4
• 作者: Armoni A

Center symmetry and the Hagedorn spectrum

中心对称性和哈格多恩谱

• DOI: 10.1103/physrevd.91.085007
• 发表时间: 2015
• 期刊: Physical Review D
• 影响因子: 5
• 作者: Armoni A

S wave bottomonium states moving in a quark-gluon plasma from lattice NRQCD

• DOI: 10.1007/jhep03(2013)084
• 发表时间: 2013-03-01
• 期刊: JOURNAL OF HIGH ENERGY PHYSICS
• 影响因子: 5.4
• 作者: Aarts, G.;Allton, C.;Skullerud, J. -I.
• 通讯作者: Skullerud, J. -I.

Defects in Chern-Simons theory, gauged WZW models on the brane, and level-rank duality

Chern-Simons 理论、膜上测量的 WZW 模型以及级别-等级二元性中的缺陷

• DOI: 10.1007/jhep07(2015)062
• 发表时间: 2015
• 期刊: Journal of High Energy Physics
• 影响因子: 5.4
• 作者: Armoni A