Methods for a blind analysis of isobar data collected by the STAR collaboration

In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.

Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at √sNN=200 GeV

High transverse momentum(pT)particle production is suppressed owing to the parton(jet)energy loss in the hot dense medium created in relativistic heavy-ion collisions.Redistribution of energy at low-to-modest pT has been difficult to measure,owing to large anisotropic backgrounds.We report a data-driven method for background evaluation and subtraction,exploiting the away-side pseudorapidity gaps,to measure the jetlike correlation shape in Au+Au collisions at √sNN=200 GeV in the STAR experiment.The correlation shapes,for trigger particles pT>3GeV/c and various associated particle pT ranges within 0.5<pT<10GeV/c,are consistent with Gaussians,and their widths increase with centrality.The results indicate jet broadening in the medium created in central heavy-ion collisions.

Mechanical behavior of advanced nano-laminates embedded with carbon nanotubes-a review

Embedding carbon nanotubes(CNTs)in load-bearing composite laminate hosts to turn them into nano-laminates is a rapidly emerging field and has tremendous potential in enhancing the mechanical performance of the host laminates.This state-of-the-art review intends to provide a physical insight into the understanding of the enhancing mechanisms of the processed and controlled CNTs in the nano-laminates.It focuses on four aspects:(1)physical characteristics of CNTs,including CNT length,diameter,weight percentage and surface functionalization;(2)processing and control techniques of CNTs in the fabrication of nano-laminates,including distribution,dispersion and orientation controls of CNTs;(3)mechanical properties along with their testing methods,including tension,in-plane compression,in-plane and interlaminar shear(ILS),flexure,mode I and mode II fracture toughness as well as compression-after-impact(CAI),ballistic protection and fatigue;and(4)CNT-matrix load transfer and enhancing mechanisms along with a few major governing factors.The selective and uniform production of CNTs with specific dimensions and physical properties has yet to be achieved on a consistent basis.Moreover,the processing details of CNTs vary very significantly among different researchers so that the processed CNTs share little common characteristics.There is little control over the CNT orientations in most fabrication processes of the nano-laminates except for some cases associated with chemical vapor deposition(CVD).There are only two reports on in-plane compression and there is only one on in-plane shear.For reinforcement-dominated mechanical properties such as longitudinal tension and flexure,there was little enhancement reported.However,the substantial enhancement in in-plane compression strength was also reported.For matrix-dominated mechanical properties,such as transverse tension,in-plane shear,ILS strength and mode I and mode II fracture toughness,a significant enhancement,albeit with substantially varying degrees,was reported for ILS strength and mode I and mode II fracture toughness values.Meanwhile,the lack of consistent characterization of those properties was also noticeable.There is little established understanding of the enhancing mechanisms in nanolaminates.