CAREER: Studies of Heavy Quarkonium Production in Relativistic Heavy-Ion Collisions at UC Davis.

职业：在加州大学戴维斯分校从事相对论重离子碰撞中重夸克子产生的研究。摘要：在对自然界基本相互作用的研究中，最引人注目的是强核相互作用。这是对付夸克和胶子的力，它们是构成质子和中子的基本粒子，因此是我们周围所有物质的基本组成部分。强相互作用的一个关键特性是夸克和胶子永远不会孤立存在，这种现象被称为“约束”。当核物质被加热到极端条件时，这种行为就会改变。计算预测正常的核物质存在到一定温度。在这个温度以上，有一个过渡到一个阶段，在这个阶段，核子溶解，使它们的内部夸克和胶子被释放出来。这些“被定义的”夸克和胶子因此形成了一种新的核物质状态，被称为夸克-胶子等离子体（QGP）。在大爆炸后的几微秒内，宇宙被认为已经越过了这个相边界，随着温度的降低，从QGP凝聚成强子气体。在实验方面，在实验室中产生QGP并研究其性质是高能重离子碰撞实验的主要目标。这项研究的两个关键问题是：a)提供证据，证明碰撞中产生的物质由限定的夸克和胶子组成；b)确定产生的系统的温度高于交叉温度。有几种途径可以解决上述问题，在本建议中，解决了其中之一。这是对由相对较重的夸克-反夸克对组成的粒子的研究，它们被强作用力束缚。这些状态很有趣，因为在QGP中，高温和定义较轻的夸克和胶子的存在改变了这些重夸克-反夸克状态的光谱性质，使它们不再结合。当重离子碰撞形成QGP时，相对于没有形成QGP的质子+质子或氘核+核碰撞，这些态的产生受到抑制，从而为定义提供了一个特征。由于这些夸克-反夸克粒子的基态和激发态在不同的温度下熔化，测量它们的相对比例为实验家提供了测量这种极热物质的温度计。在这个提议中，首席研究员将测量重离子碰撞中最重的可用夸克-反夸克束缚态的产生。研究将在重离子碰撞的最高能量加速器上进行：位于布鲁克海文国家实验室（长岛，纽约）的相对论重离子对撞机上的STAR探测器和位于欧洲高能物理实验室（日内瓦，瑞士）的大型强子对撞机上的CMS探测器。PI将维持一个外联计划，重点放在三个组成部分。他将指导参加戴维斯大学REU项目的本科生。他是奇卡诺人和美洲原住民科学促进会（SACNAS）的成员。通过SACNAS， PI向未来的拉丁裔科学家传达重离子研究的兴奋，在他们的年度会议上指导学生，参与学生海报的选择，并评审学生的演讲。最后，他将为Cesar Chavez学校的理科生进行物理演讲和演示，这是一所位于戴维斯的西班牙语浸入式学校。

CAREER: Studies of Heavy Quarkonium Production in Relativistic Heavy-Ion Collisions at UC Davis.Abstract:In the study of the basic interactions of nature, one of the most intriguing is the strong nuclear interaction. This is the force which deals with quarks and gluons, which are the elementary particles that make up protons and neutrons, and are therefore the basic building blocks of all the matter we see around us. A key property of the strong interaction is that quarks and gluons are never seen in isolation, a phenomenon called "confinement". This behavior changes when nuclear matter is heated to extreme conditions. Calculations predict that normal nuclear matter exists up to a certain temperature. Above this temperature, there is a cross-over to a phase where nucleons dissolve such that their inner quarks and gluons are liberated. These "deconfined" quarks and gluons thus form a new state of nuclear matter, which has been called the Quark-Gluon Plasma (QGP). A few microseconds after the Big Bang, the universe is believed to have crossed this phase boundary, condensing from a QGP to a hadron gas as the temperature decreased. In the experimental front, producing the QGP in the laboratory and studying its properties is the main goal of experiments with heavy-ion collisions at high-energies. Two key issues in this search are a) producing evidence that the matter produced in the collisions consists of deconfined quarks and gluons, and b) determining that the temperature of the produced system is above the cross-over temperature. There are several avenues to attack the above issues, and in this proposal, one of them is addressed. This is the study of particles made of relatively heavy quark-antiquark pairs, which are bound by the strong force. These states are interesting because in a QGP, the high temperatures and the presence of deconfined lighter quarks and gluons modify the spectral properties of these heavy quark-antiquark states such that they no longer bind. When a heavy-ion collision forms a QGP, the production of these states is therefore suppressed relative to proton+proton or deuteron+nucleus collisions where no QGP is formed, providing a signature for deconfinement. Since the ground states and the excited states of these quark-antiquark particles melt at different temperatures, measuring the relative ratios provides experimentalists with a thermometer for this extremely hot matter. In this proposal, the Principal Investigator will measure the production of the heaviest available quark-antiquark bound states in heavy ion collisions. The investigations will be carried out at the highest energy accelerators for heavy ion collisions: with the STAR detector at the Relativistic Heavy-Ion Collider located in Brookhaven National Laboratory (Long Island, NY) and with the CMS detector at the Large Hadron Collider in the European Laboratory for High Energy Physics (CERN, Geneva, Switzerland).The PI will maintain an outreach program focusing on three components. He will mentor undergraduate students participating in the REU program at Davis. He is a member of the Society of the Advancement of Chicanos and Native Americans in Science (SACNAS). Through SACNAS, the PI communicates the excitement of heavy-ion research to future Latino scientists, mentors students during their annual conference, participates in the selection of student posters, and judges student presentations. Finally, he will develop physics presentations and demonstrations for the science students of the Cesar Chavez School, a Spanish-immersion school in Davis.