Triton Production And Neutron Density Fluctuations At RHIC

Quark and lepton constitute the infinite and ever-changing physical laws of nature through electromagnetic interaction,weak interaction,strong interaction,and gravitational interaction.Strong interactions are the strongest of the four interactions and the key to understanding the basic components of the microcosm and the laws of interaction between them.The continuous research and development of strong interactions finally established a strong interaction quantum field theory-quantum chromodynamics theory.The basic components of the theory are quarks and gluons,which are tightly bound to the inside of the hadrons and cannot be freed to a single state.It is only possible to indirectly observe their existence by hadron experiments.The relativistic heavy-ion collision experiment is a powerful tool for studying the QCD phase structure and plays a guiding role in exploring the state of matter,strong interactions,and the evolution of the universe.In the theory,the lattice QCD predicts that the transition from the hadron phase of the quark-gluon confinement to the QCD phase of the deconfinement in the high-temperature and low-baryon density region is a crossover,and the phase transition occurs in the low-temperature and high-baryon density region is the first-order phase boundary.And the first-order phase transition boundary has an end point,called the QCD critical point.Searching and locating the critical point has become a hot topic and preface topic in today’s high-energy physics experiments and theoretical research.Explore the QCD phase diagram is the most important goal of t.he STAR experiment at RHIC in Brookhaven National Laboratory.In high-energy nuclear collisions’ light nuclei provide a unique tool to explore the QCD phase structure.The production of light nuclei is sensitive to the temperature and phase-space density of the system at freeze-out.In addition,phase transition will lead to large baryon density fluctuation,which will be re.fle.cted in the.light nucle.i production.For example,the ratio of proton(N(p))and triton(N(t))to deuteron(N(d))yields,which is defined as N(t)·N(p)/N2(d),may be used as a sensitive observable to search for the QCD critical point.In this paper,we will report the energy dependence of light nuclei(t)production in Au+Au collisions at(?)=7.7,11.5,14.5,19.6,27,39,62.4,and 200 GeV measured by the STAR experime.nt at RHIC.We will present the beam energy dependence for the coalescence parameter B3(t)and the yield ratio of N(t)-N(p)/N2(d).Their physics implications will be discussed.