The Production Of Light (Anti-) Nuclei And Hypernuclei In Proton-proton Collisions

Research on the production and characteristics of antimatter has always been one of the important research topics in modern physics.As early as 1928,the British physicist Dirac proposed the theoretical hypothesis of the existence of antimatter.In 1932,positrons were first discovered in cosmic rays.According to the Big Bang theory of cosmology,in the original universe,the positive and negative particles should be equal,but the universe we are in now is full of ordinary matter,but the anti-matter does not know where it is.The asymmetry of particles and antiparticles matter has always been an unsolved mystery in the field of physics.For a long time,scientists have used detectors and accelerators,hoping to discover and create antimatter.Until this century,anti-helium nuclei and anti-hypertritium nuclei were successfully produced on the Large Hadron Collider of the RHIC laboratory in the United States and the European Nuclear Research Center(CERN).High-energy collision experiments can create a universe environment similar to the microseconds after the Big Bang,during which abundant nuclei and anti-nuclei can be produced.This provides us with an effective way to study anti-nuclei and anti-hypernuclei.The progress of antimatter research has important implications for our understanding of the structure of matter.In-depth study of antimatter is also an important link in solving the mystery of the origin of the universe.Therefore,the study of antimatter has important theoretical significance.High-energy collision experiments provide a unique possibility to study nuclear matter in extreme environments,especially the lifting of the forbidden phase quark-gluon plasma(QGP),which is predicted by lattice-dot quantum chromodynamics.However,due to the low efficiency of the accelerator experiment to produce antimatter,the cost is also very expensive.Model simulation research has become an important method and means of antimatter research.Currently,some models describing high-energy hadron-hadron collisions include event generators PYTHIA,EPOS and PHOJET,as well as perturbative quantum chromodynamics(pQCD)calculations to describe hard processes and phenomenological models to describe soft process components.This paper introduces the parton-hadron cascade model-PACIAE and PYTHIA models to simulate proton-proton collision events with different center of mass energies to obtain the multi-particle final state;then use the dynamic constrained phase space combination model(DCPC)to combine to produce light(Anti-)nuclei and(anti-)hypernuclei,in order to study the generation and characteristics of light antinuclei and hypernuclei in high-energy proton-proton collisions.This article first introduces the theories and experiments of antinuclear matter production,including the standard model,quantum chromodynamics(QCD),quark gluon plasma(QGP),QCD phase transition and other basic theories of particle physics and nuclear physics,as well as heavy ion collisions physical.The second chapter introduces the proposal of antimatter theory and the discovery of antimatter in the experiment.In 1928,the British physicist Dirac(P.A.M.Dirac)formally introduced the concept of positron when explaining the negative energy solution of Dirac's equation,predicting the annihilation and generation of positron and electron pairs,and made people realize the existence of antimatter.In 1932,the American physicist C.D.Anderson discovered the positron in a cosmic ray experiment-it was the first antiparticle discovered by people.With the advancement of accelerators and detectors,some scientists use advanced modern accelerator technology to produce antimatter in the laboratory through large-scale colliders or detect antimatter signals in the universe through detectors or magnetic spectrometers.In 1955,E.G.Segre and Chamberlain(O.Chamberlain)discovered the antiproton through the Proton Synchronous Stabilization Accelerator of Berkeley in the United States.At the end of 1956,Cork and others discovered anti-neutrons.In the next two decades,anti-deuteron,anti-triton,and anti-helium-3 nuclei were discovered one after another in accelerator experiments.In 1965,the research team that Ding Zhaozhong participated in successfully observed the anti-deuteron at the Proton Synchrotron of the Interactive Gradient at Brookhaven National Laboratory.In 1971,Soviet scientists measured the antimatter atomic nucleus with a mass number of 3-the anti-helium-3 nuclear signal at its National High Energy Physics Laboratory.The ALPHA experiment at CERN in 1995 produced for the first time the simplest ground state of antimatter atom-antihydrogen atom.In 1996,the Fermi National Accelerator Laboratory in the United States successfully produced 7 anti-hydrogen atoms.In April 1997,American astronomers announced that they had used gamma-ray detection satellites to discover that there was an antimatter source that continuously ejected antimatter about 3,500 light years above the Milky Way.The antimatter ejected formed an "antimatter" up to 2940 light-years away "fountain".On September 18,2000,CERN announced that the laboratory had successfully produced about 50,000 antihydrogen atoms in a low-energy state.This was the first time that humans had produced large quantities of antimatter under laboratory conditions.The ALICE experimental group also announced that an anti-deuteron was measured in a proton-proton collision with a center of mass energy of 7 TeV.Scientists have also tried a series of studies on the synthesis of antimatter atoms.In 2010,CERN researchers successfully captured antihydrogen atoms in the laboratory and maintained their state for 172 milliseconds.One year later,they increased the maintenance time to 1,000 seconds.Scientists want to examine the principle of CPT symmetry by studying the energy spectrum of antihydrogen atoms.By comparing the quantum properties and fine structure of the positive and negative hydrogen atoms,as well as the measurement results of the atomic energy spectrum,if any difference can be found,it will herald a new physics.At the same time,the precise measurement of the anti-hydrogen atom's gravity is also an important experiment to test the basic laws of physics.In the same year,the RHIC-STAR cooperation group made important progress in antimatter detection.Chen Jinhui and Ma Yugang,Shanghai Institute of Applied Physics,Chinese Academy of Sciences,worked closely with other Chinese and foreign scientists such as Xu Changbu of STAR,and achieved hundreds of millions of times.Gold nuclei carry out high-energy "bumps" in the massive data to find evidence of anti-hypernuclei.Finally,by reconstructing the invariant mass spectra of anti-helium-3 nuclei and ?mesons,the first anti-hypernuclei particle,anti-hypertriton,was detected.These major discoveries are of great significance in the fields of nuclear physics and astrophysics,and once again triggered an upsurge in antimatter research.Antimatter research will also provide a deep understanding of the state of matter in the early universe and the composition of neutron stars and other stars.Then the third chapter specifically describes the high-energy collision transport model used in this paper-parton and hadron cascade model(PYTHIA,PACIAE)and dynamic constrained phase space combination model(DCPC).This dissertation will use the parton-hadron cascade model(PYTHIA,PACIAE)to generate nuclear-nuclear collision event data,and use the dynamic constrained phase space combination model(DCPC)to generate positive and anti-light nuclei and hypernuclei to study antimatter Generate characteristics and laws.The PYTHIA model is a parton-hadron cascade model,which contains a complete evolution process from partons to hadrons;the PACIAE model adds parton rescattering and hadron rescattering on the basis of the PYTHIA model,which is better than the PYTHIA model It is more suitable to describe the high-energy nuclear-nucleus(including pp)collision process.The DCPC combined model is based on the principle of dynamics plus dynamic constraints,using the multi-particle final state produced by PYTHIA or PACIAE as input,and calculating the generation of light antinuclear matter in high-energy collisions through phase space integration.Then,in Chapter 4,the generation and characteristics of light nuclei and anti-nuclei in high-energy proton-proton collisions are given.First,we use the PACIAE and PYTHIA models to generate the final hadrons' transverse momentum spectrum and fit the experimental data under the same conditions to determine the parameters of the PACIAE and PYTHIA models;then,the simulated center of mass energies are(?)=0.9,2.76,and 7 TeV respectively,the pseudorapidity range is |?|<0.5,and the 4.0×109 proton-proton collision events with the transverse momentum range of 0<pT<8 GeV/c,resulting in the final hadrons;then the phases with dynamic constraints are used.The combination of the spatial combination model(DCPC)produces light(anti)nuclei(d,d,3He,3He).To study the generation and characteristics of light anti-nuclei in high-energy proton-proton collisions d,d,3He,3He.We predicted the yield,yield ratio,and lateral momentum distribution of light(anti)nuclei in proton-proton collisions with center-of-mass energies of 0.90,2.76,and 7 TeV,respectively.The calculation results show that:d,d,3He,3He the yield of is obviously energy dependent,that is,when the collision energy increases,the yield increases significantly;when the mass number A of the produced nuclei increases,the yield of light(anti)nuclei decreases sharply;different energies The distribution patterns of the transverse momentum spectrum below are the same;the yield of antiparticles is smaller than that of positive particles,which indicates that the production of antimatter in high-energy proton-proton collisions is more difficult than that of positive matter.However,the ratio of antiparticle to positive particle yield remains unchanged under different collision energies,indicating that the nuclei and antinuclei produced at LHC energy have similar abundance.In Chapter 5,the production and characteristics of hypernuclei and anti-hypernuclei in high-energy proton-proton collisions are given.First,we use PACIAE and PYTHIA models to generate 4.0 × 109 protons with center of mass energies of 0.9,2.76,and 7 TeV,pseudorapidity range |?|<0.5,and transverse momentum range of 0<pT<8 GeV/c,proton-proton collision event;then use the dynamic constrained phase space combination model to combine to produce hypernuclei and anti-hypernuclei((?),(?)).In this way,we can study the generation and characteristics of hypernuclei in high-energy proton-proton collisions.We predicted the yield,yield ratio,and lateral momentum distribution of hypernuclei and anti-hypernuclei(?)in proton-proton collisions with center of mass energies of 0.90,2.76,and 7TeV,respectively.The calculation results show that:(?)the yield of is obviously energy dependent,that is,when the collision energy increases,the yield increases significantly;the distribution of the transverse momentum spectrum under different energies is the same.Secondly,we simulated and calculated the singular abundance factors in proton-proton collisions.Under three different collision energies S3=((?))/(?/p),they are nearly equal,and they are approximately in the range of 0.7 to 0.8.We use PACIAE+DCPC model to simulate and calculate part of the results that are in good agreement with the ALICE experimental data,and other results will provide references for further experimental research.