In this study,we employ the maximum likelihood estimator(MLE)to investigate the relationship between initial-state fluctuations and final-state anisotropies in relativistic heavy-ion collisions.The granularity of the ...In this study,we employ the maximum likelihood estimator(MLE)to investigate the relationship between initial-state fluctuations and final-state anisotropies in relativistic heavy-ion collisions.The granularity of the initial state,reflecting fluctuations in the initial conditions(ICs),is modeled using a peripheral tube model.In addition to differential flow,our analysis focuses on a class of more sensitive observables known as flow factorization.Specifically,we evaluate these observables using the MLE,an asymptotically normal and unbiased tool in standard statistical inference.Our findings show that the resulting differential flow remains essentially unchanged for different ICs defined by the peripheral tube model.The resulting harmonic coefficients obtained using the MLE and multiparticle cumulants are found to be consistent.However,the calculated flow factorizations show significant variations depending on both the IC and estimators,which is attributed to their sensitivity to initial-state fluctuations.Thus,we argue that the MLE offers a compelling alternative to standard methods,such as multi-particle correlators,particularly for sensitive observables constructed from higher moments of the azimuthal distribution.展开更多
Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light ...Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.展开更多
基金under the project Institutos Nacionais de Ciências e Tecnologia-Física Nuclear e Aplicacoes(INCT/FNA)Proc.(464898/2014-5)Supported by the Center for Scientific Computing(NCC/GridUNESP)of Sao Paulo State University(UNESP)+6 种基金the funding from the Physics Master Teacher Studio of Guangsha Universitythe support of the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX22-3453)the support of the National Natural Science Foundation of China(12347101)financial support from Brazilian agencies Fundacao de AmparoàPesquisa do Estado de Sao Paulo(FAPESP)Fundacao de AmparoàPesquisa do Estado do Rio de Janeiro(FAPERJ)Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq)Coordenacao de Aperfeicoamento de Pessoal de Nível Superior(CAPES)。
文摘In this study,we employ the maximum likelihood estimator(MLE)to investigate the relationship between initial-state fluctuations and final-state anisotropies in relativistic heavy-ion collisions.The granularity of the initial state,reflecting fluctuations in the initial conditions(ICs),is modeled using a peripheral tube model.In addition to differential flow,our analysis focuses on a class of more sensitive observables known as flow factorization.Specifically,we evaluate these observables using the MLE,an asymptotically normal and unbiased tool in standard statistical inference.Our findings show that the resulting differential flow remains essentially unchanged for different ICs defined by the peripheral tube model.The resulting harmonic coefficients obtained using the MLE and multiparticle cumulants are found to be consistent.However,the calculated flow factorizations show significant variations depending on both the IC and estimators,which is attributed to their sensitivity to initial-state fluctuations.Thus,we argue that the MLE offers a compelling alternative to standard methods,such as multi-particle correlators,particularly for sensitive observables constructed from higher moments of the azimuthal distribution.
基金support of the Joint Centre for Extreme Photonics.Funding:This work is supported by the start-up grant of ShanghaiTech University,Double First-Class Initiative Fund of ShanghaiTech University,Shanghai Rising-Star Program(22QA1406200)National Natural Science Foundation of China(12274297,92250303)+7 种基金Shanghai Science and Technology Program(21511105000)NSERC Discovery Grant program(RGPIN-327147-2012)by the U.S.Army Research Office through Award W911NF-14-1-0383Part of this research used Beamline 03U of the Shanghai Synchrotron Radiation Facilitysupported by the ME2 project under contract no.11227902the National Natural Science Foundation of China.Y.F.and C.J.are supported by the National Natural Science Foundation of China(12274230,91950102,and 11834004)Funding of NJUST(TSXK2022D005)H.X.is supported by the National Natural Science Foundation of China(12074063 and 12264003)。
文摘Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.
