Probing granular inhomogeneity of a particle-emitting source by imaging two-pion Bose–Einstein correlations

Using the source imaging technique in two-pion interferometry,we study the image of the hydrodynamic particle-emitting source with the HIJING initial conditions for relativistic heavy-ion collisions on an event-by-event basis.It is shown that the initial-state fluctuations may give rise to bumpy structures of the medium during hydrodynamical evolution,which affects the two-pion emission space and leads to a visible two-tiered shape in the source function imaged using the two-pion Bose–Einstein correlations.This two-tiered shape can be understood within a similar but more analytic granular source model and is found to be closely related to the introduced quantity n,which characterizes the granular inhomogeneity of the source.By fitting the imaged source function with a granular source parametrization,we extract the granular inhomogeneity of the hydrodynamic source,which is found to be sensitive to both the Gaussian smearing width of the HIJING initial condition and the centrality of the collisions.

An event mixing technique for Bose-Einstein correlations of two pions in photoproduction around 1 GeV

We have developed an event mixing technique to observe Bose-Einstein correlations （BEC） between two identical neutral pions produced in photo-induced reactions in the non-perturbative QCD energy region. It is found that the missing-mass consistency cut and the pion-energy cut are essential for the event mixing method to effectively extract BEC observables. A Monte Carlo （MC） simulation is used to validate these constraints and confirms the efficiency of this method. Our work paves the way for similar BEC studies at lower energies where the multiplicity of emitted bosons is limited.

An energy sum constraint of event mixing for Bose-Einstein correlations in reactions with ππX final states around 1 GeV

We present a new event mixing technique for measuring two-pion Bose-Einstein correlations （BEC） in reactions with only two identical bosons among three final state particles. This new mixing method contains a missing mass consistency （MMC） cut and an energy sum order （ESO） cut. Unlike the previous proposed pion energy cut, which abandons nearly half the original events, the ESO cut does not eliminate any original events and hence improves the statistics of both original events and mixed events. Numerical tests using the γp→π0π0p events around 1 GeV are carried out to verify the validity of the ESO cut. This cut is able to reproduce the relative momentum distribution of the original events in the absence of BEC effects. In addition, its ability to observe BEC effects is tested by an event sample in the presence of BEC effects. Simulation results show the BEC effects can be observed clearly as an enhancement in the correlation function, and the BEC parameters extracted by this event mixing cut are consistent with the input BEC parameters.

Entanglement and nonlocality in multi-particle systems

Entanglement, the Einstein-Podolsky Rosen （EPR） paradox and Bell＇s failure of local-hidden- variable （LHV） theories are three historically famous forms of ＂quantum nonlocality＂. We give experimental criteria for these three forms of nonlocality in multi-particle systems, with the aim of better understanding the transition from microscopic to macroscopic nonlocality. We examine the nonlocality of N separated spin J systems. First, we obtain multipartite Bell inequalities that address the correlation between spin values measured at each site, and then we review spin squeezing inequal- ities that address the degree of reduction in the variance of collective spins. The latter have been particularly useful as a tool for investigating entanglement in Bose Einstein eondensates （BEC）. We present solutions for two topical quantum states： multi-qubit Greenberger-Horne Zeilinger （GHZ） states, and the ground state of a two-well BEC.