Stimulated by a keen interest in possible collective behavior in high-energy proton-proton and protonnucleus collisions,we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulat...Stimulated by a keen interest in possible collective behavior in high-energy proton-proton and protonnucleus collisions,we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulated p+p interactions using the Pythia 8 event generator.Multi-parton interactions and color connection are included in these simulations,which have been perceived to produce collectivity in final-state particles.Meanwhile,contributions from genuine few-body nonflow correlations,not of collective flow behavior,are known to be severe in these small-system collisions.We present our Pythia correlation studies pedagogically and report azimuthal harmonic anisotropies analyzed using several methods.We observe anisotropies in these Pythia simulated events qualitatively and semi-quantitatively,similar to experimental data.Our findings highlight the delicate nature of azimuthal anisotropies in small-system collisions and provide a benchmark that can aid in improving data analysis and interpreting experimental measurements in small-system collisions.展开更多
The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a...The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.展开更多
基金Supported in part by the U.S.Department of Energy(DE-SCo012910)。
文摘Stimulated by a keen interest in possible collective behavior in high-energy proton-proton and protonnucleus collisions,we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulated p+p interactions using the Pythia 8 event generator.Multi-parton interactions and color connection are included in these simulations,which have been perceived to produce collectivity in final-state particles.Meanwhile,contributions from genuine few-body nonflow correlations,not of collective flow behavior,are known to be severe in these small-system collisions.We present our Pythia correlation studies pedagogically and report azimuthal harmonic anisotropies analyzed using several methods.We observe anisotropies in these Pythia simulated events qualitatively and semi-quantitatively,similar to experimental data.Our findings highlight the delicate nature of azimuthal anisotropies in small-system collisions and provide a benchmark that can aid in improving data analysis and interpreting experimental measurements in small-system collisions.
文摘The chiral magnetic effect (CME) refers to a charge separation along a strong magnetic field due to an imbalanced chirality of quarks from interactions with the vacuum topological gluon field. This chiral anomaly is a fundamental property of quantum chromodynamics (QCD) and, therefore, an observation of the CME would have far-reaching impact on our understanding of QCD and Nature. The measurements of the CME-sensitive azimuthal correlator Δγ observable in heavy-ion collisions are contaminated by a major background induced by elliptic flow anisotropy. Several novel approaches have been carried out, including a dedicated isobar collision program, to address this flow-induced background. Further background effects, arising from nonflow correlations, have been studied. While the isobar data are consistent with zero CME signal with an upper limit of 10% of the measured Δγ, the Au+Au midcentral data suggest a positive CME signal on the order of 10% of the measured Δγ with a significance of ~2 standard deviations. Future increased statistics and improved detector capability should yield a firm conclusion on the existence (or the lack) of the CME in relativistic heavy-ion collisions.
