Discovering Exotics at Jefferson Lab

约克大学的强子与核物理小组正在寻找一名聪明而热情的博士生，利用强电子束和CLAS探测器在杰斐逊实验室发现奇异粒子。描述强相互作用的基本理论是量子色动力学。QCD允许夸克有多种束缚态。最简单和最成熟的构型是介子（夸克-反夸克系统）和重子（3个夸克系统）。这个领域目前正经历着快速的变化，四夸克、五夸克、六夸克和强子分子的说法直到最近才开始显露出来。这一进展是通过利用强度前沿的尖端粒子束，以及首次与大型可接受粒子探测器相结合而实现的。该领域引起了公众极大的兴趣，具有很高的科学影响。发现新的奇异粒子的故事吸引了媒体的大量关注。我们的团队正在领导一些令人兴奋的研究，这些研究揭示了六夸克态——六夸克[PRL 1,2,3,4]。我们利用独特的清洁和受控的生产环境，可通过光和电诱导的反应。在大多数情况下，证明新粒子的奇异性质是一项具有挑战性的任务。然而，重子数B=2的六夸克很容易识别。我们小组参与了最近发现的第一个非平凡六夸克，d*(2380)，其夸克含量为uddd。我们目前的大部分活动现在都致力于这一发现：我们最近表明，d*(2380)可能在中子星内大量形成，影响基本性质[PLB]，也可能在早期宇宙中大量产生。像任何其他粒子一样，d*(2380)不是单独出现的，而是作为SU(3)多重粒子的一部分。在d*的情况下，它是反十重子，所以我们预计会发现9个具有相同自旋宇称（JP = 3+）但奇异度不同的粒子。该发现的下一个候选粒子将是ds——一种含有夸克的粒子。这种粒子可以在JLab设施中大量生产，并通过高接受度的CLAS12探测器设备进行检测。经过JLab的能量和亮度升级后，在几周的数据采集时间内就可以收集到足够的统计数据。带有氘核目标的第一个CLAS光束时间刚刚开始。对于一个博士生来说，这将是一个黄金机会，以数据采集开始项目，并以一篇重要的发现论文完成项目。

The Hadron and Nuclear Physics group at the University of York is looking for a bright and enthusiastic PhD student todiscover exotic particles at Jefferson Laboratory utilizing intense electron beam and CLAS detector.The fundamental theory thought to describe the strong interaction is Quantum Chromodynamics (QCD). QCD permits a large variety of bound states of quarks. The simplest and best-established configurations are mesons (quark-anti-quark systems) and baryons (3 quark systems). The field is currently undergoing rapid change with claims of tetraquarks, pentaquarks, hexaquarks and hadronic molecules only recently starting to reveal themselves. The advance has been made possible through exploiting cutting-edge particle beams at the frontiers of intensity, coupled for the first time with large acceptance particle detectors. The field has attracted very significant public interest and has high scientific impact. Stories about discoveries of new exotic particles attract significant media attention.Our group is leading exciting studies which are revealing six-quark states - hexaquarks [PRL 1,2,3,4]. We exploit the uniquely clean and controlled production environment accessible through photo- and electro-induced reactions. Proving the exotic nature of a new particle is a challenging task for the majority of the cases. However hexaquarks, where baryon number B=2 are easily identifiable. Our group was involved in a recent discovery of a first non-trivial hexaquark, the d* (2380), having quark content uuuddd. A large fraction of our current activities are now devoted to this discovery: we have recently shown that the d*(2380) may form copiously within neutron stars influencing fundamental properties [PLB] and also be produced significantly in early Universe.Like any other particles, the d*(2380) does not appear alone, but as a part of an SU(3) multiplet. In the d*'s case it is antidecuplet, so we expect 9 more particles with the same spin-parity (JP = 3+) but different strangeness to be discovered. The next candidate for the discovery would be ds - a particle with a quark content uuudds. This particle can be produced in large quantities at the JLab facility and detected by the high acceptance CLAS12 detector apparatus. After the energy and the luminosity upgrade of the JLab one can collect adequate statistics within few weeks of data taking. The first CLAS beam time with a deuteron target has been just started. For a PhD student it would be a golden opportunity to start the project with the data taking and complete it with an important discovery paper.