{"title":"Exclusive J/ψ, ψ(2s), and e+e− pair production in Au+Au ultraperipheral collisions at the BNL Relativistic Heavy Ion Collider","authors":"M. I. Abdulhamidet al.(STAR Collaboration)","doi":"10.1103/physrevc.110.014911","DOIUrl":null,"url":null,"abstract":"Measurements of exclusive <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow><mo>,</mo><mo> </mo><mrow><mi>ψ</mi><mo>(</mo><mn>2</mn><mi>s</mi><mo>)</mo></mrow></math>, and electron-positron (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow></math>) pair photoproduction in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Au</mi><mo>+</mo><mi>Au</mi></mrow></math> ultraperipheral collisions are reported by the STAR experiment at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msqrt><msub><mi>s</mi><msub><mrow></mrow><mi>NN</mi></msub></msub></msqrt><mo>=</mo><mn>200</mn><mspace width=\"4pt\"></mspace><mi>GeV</mi></mrow></math>. We report several first measurements at the BNL Relativistic Heavy Ion Collider, which are (i) <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> photoproduction with large momentum transfer up to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mrow><mn>2.2</mn><mspace width=\"4pt\"></mspace><mrow><mo>(</mo><mi>GeV</mi></mrow><mo>/</mo><mi>c</mi><mo>)</mo></mrow><mn>2</mn></msup></math>, (ii) coherent <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> photoproduction associated with neutron emissions from nuclear breakup, (iii) the rapidity dependence of incoherent <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> photoproduction, (iv) the <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>ψ</mi><mo>(</mo><mn>2</mn><mi>s</mi><mo>)</mo></mrow></math> photoproduction cross section at midrapidity, and (v) <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow></math> pair photoproduction up to high invariant mass of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>6</mn><mspace width=\"4pt\"></mspace><mi>GeV</mi><mo>/</mo><msup><mi>c</mi><mn>2</mn></msup></mrow></math>. For measurement (ii), the coherent <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> total cross section of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>γ</mi><mo>+</mo><mi>Au</mi><mo>→</mo><mi mathvariant=\"normal\">J</mi><mo>/</mo><mi>ψ</mi><mo>+</mo><mi>Au</mi></mrow></math> as a function of the center-of-mass energy <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>W</mi><mrow><mi>γ</mi><mi>N</mi></mrow></msub></math> has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, quantum electrodynamics, and the next-to-leading-order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> cross sections of Au nuclei are found to be <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>71</mn><mo>%</mo><mo>±</mo><mn>10</mn><mo>%</mo></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>36</mn><mo>%</mo><mo>±</mo><mn>7</mn><mo>%</mo></mrow></math>, respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.","PeriodicalId":20122,"journal":{"name":"Physical Review C","volume":null,"pages":null},"PeriodicalIF":3.1000,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physical Review C","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1103/physrevc.110.014911","RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"Physics and Astronomy","Score":null,"Total":0}
引用次数: 0
Abstract
Measurements of exclusive , and electron-positron () pair photoproduction in ultraperipheral collisions are reported by the STAR experiment at . We report several first measurements at the BNL Relativistic Heavy Ion Collider, which are (i) photoproduction with large momentum transfer up to , (ii) coherent photoproduction associated with neutron emissions from nuclear breakup, (iii) the rapidity dependence of incoherent photoproduction, (iv) the photoproduction cross section at midrapidity, and (v) pair photoproduction up to high invariant mass of . For measurement (ii), the coherent total cross section of as a function of the center-of-mass energy has been obtained without photon energy ambiguities. The data are quantitatively compared with the Monte Carlo models STARlight, Sartre, BeAGLE, and theoretical calculations of gluon saturation with color glass condensate, nuclear shadowing with leading twist approximation, quantum electrodynamics, and the next-to-leading-order perturbative QCD. At the photon-nucleon center-of-mass energy of 25.0 GeV, the coherent and incoherent cross sections of Au nuclei are found to be and , respectively, of that of free protons. These data provide an important experimental constraint for nuclear parton distribution functions and a unique opportunity to advance the understanding of the nuclear modification effect at the top RHIC energy.
期刊介绍:
Physical Review C (PRC) is a leading journal in theoretical and experimental nuclear physics, publishing more than two-thirds of the research literature in the field.
PRC covers experimental and theoretical results in all aspects of nuclear physics, including:
Nucleon-nucleon interaction, few-body systems
Nuclear structure
Nuclear reactions
Relativistic nuclear collisions
Hadronic physics and QCD
Electroweak interaction, symmetries
Nuclear astrophysics