Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter. Event vertex and event time are not only useful for event selection but also essential for the rec
onstruction of event energy. In this study, four event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes were analyzed comprehensively. The effects of photomultiplier tube properties were also investigated. The results indicate that the transit time spread is the main effect degrading the vertex reconstruction, while the effect of dark noise is limited. In addition, when the event is close to the detector boundary, the charge information provides better performance for vertex reconstruction than the time information.
A visualization method based on Unity engine is proposed for the Jiangmen Underground Neutrino Observatory (JUNO) experiment. The method has been applied in development of a new event display tool named ELAINA (Event Live Animation with unIty for Neu
trino Analysis), which provides an intuitive way for users to observe the detector geometry, to tune the reconstruction algorithm and to analyze the physics events. In comparison with the traditional ROOT-based event display, ELAINA provides better visual effects with the Unity engine. It is developed independently of the JUNO offline software but shares the same detector description and event data model in JUNO offline with interfaces. Users can easily download and run the event display on their local computers with different operation systems.
The current event display system in the offline software of Jiangmen Underground Neutrino Observatory Experiment(JUNO) is based on the ROOT EVE package. We use Unity, a renowned game engine, to improve its performance and make it available on differe
nt platforms. Compared to ROOT, Unity provides a more vivid demonstration for high energy physics experiments and can be ported to different platforms easily. We build a tool for event display in JUNO with Unity. It provides us an intuitive way to observe the detector model, the particle trajectories and the hit distributions.
The one-dimensional quantum sine-Gordon system with a linear spatial modulation is investigated in a special case, $beta ^{2}$ =4$pi $. The model is tranformed into a massive Thirring model and then is exactly diagonalized, the energy spetrum of the
model is obtained. Our result clearly demonstrates that cancelling the cosine term without any considering is unadvisable.
The two-dimensional Jordan-Wigner transformation is used to investigate the zero temperature spin-Peierls transition for an anisotropic two-dimensional XY model in adiabatic limit. The phase diagram between the dimerized (D) state and uniform (U) sta
te is shown in the parameter space of dimensionless interchain coupling $h$ $(=J_{perp}/J)$ and spin-lattice coupling $eta$. It is found that the spin-lattice coupling $eta$ must exceed some critical value $eta_c$ in order to reach the D phase for any finite $h$. The dependence of $eta_c$ on $h$ is given by $-1/ln h$ for $hto 0$ and the transition between U and D phase is of first-order for at least $h>10^{-3}$.
