Four-boson Efimov physics is well known in the negative energy regime but far less above the four-body breakup threshold. The part of this region with negative two-boson scattering length is studied solving rigorous four-particle scattering equations for transition operators in the momentum space. Moving away from the unitary limit, the Efimov tetramers evolve from unstable bound states into resonances. Their energies and widths are studied as functions of the two-boson scattering length; a universal behavior is established and given in a dimensionless representation. The Efimov tetramers have finite width in the whole regime; they broaden rapidly in the resonance regime but remain narrower than the associated trimer. The resonant behavior is most clearly seen in the four-particle recombination rate.

中文翻译：

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高于四玻色子阈值的 Efimov 共振

四玻色子 Efimov 物理学在负能量状态下是众所周知的，但远低于四体分解阈值。研究了该区域的负双玻色子散射长度部分，用于求解动量空间中跃迁算子的严格四粒子散射方程。远离单一极限，Efimov 四聚体从不稳定的束缚态演变成共振。它们的能量和宽度被研究为两个玻色子散射长度的函数；在无量纲表示中建立并给出了普遍行为。Efimov四聚体在整个范围内具有有限的宽度；它们在共振区迅速展宽，但仍比相关的三聚体窄。在四粒子复合率中可以最清楚地看到共振行为。