The Rise and Fall of the Ridge

The Rise and Fall of the Ridge in Heavy Ion Collisions

Recent data from heavy ion collisions at RHIC show unexpectedly large near-angle correlations that broaden longitudinally with increasing centrality. The amplitude of this ridge-like correlation rises rapidly, reaches a maximum, and then falls in the most central collisions. In this letter we explain how this behavior can be explained as initial-state coordinate-space anisotropies converted into final-state momentum-space correlations. We propose $v_n^2/ε_{n,\mathrm{part}}^{2}$ as a useful way to study length scales and provide a prediction for the ridge in Pb+Pb collisions at $\sqrt{s_{\mathr…

Charge conservation and the shape of the ridge of two-particle correlations in relativistic heavy-ion collisions

We demonstrate that in the framework of the event-by-event hydrodynamics followed by statistical hadronization, the proper charge conservation in the mechanism of hadron production provides the crucial non-flow component and leads to agreement with the two-dimensional two-particle correlation data in relative azimuthal angle and pseudorapidity at soft transverse momenta (p_T<2GeV). The fall-off of the same-side ridge in relative pseudorapidity follows from the fact that a pair of particles with balanced charges is emitted from the same fluid element, whose collective velocity collimates the mo…

核质量预测中核回归的Wigner与镜像关联

Wigner and mirror correlations in nuclear mass predictions with kernel ridge regression

本研究提出Wigner与镜像关联的核岭回归方法WKRRoe，通过核函数编码关联，使核质量预测精度达98.0 keV，优于100-keV基准，尤其提升N=Z附近及镜像核的预测能力。

The "Shoulder" and the "Ridge" in PHENIX

The observation of jet quenching in ultra-relativistic heavy ion collisions demonstrates significant energy loss of fast partons when passing through the created medium. Correlations between final-state particles at intermediate transverse momentum (1.0 $\lesssim$ $p_{T}$ $\lesssim$ 4.0 GeV/$c$) allow for study of the medium and its response to deposited energy. Comparison of these measurements in heavy ion collisions with measurements in proton collisions show strong modification of the correlation shape and particle yields. Two new structures are created, both extended in $Δη$, one centered …

The Rise and Fall of Pentaquarks in Experiments

Experimental evidence for and against the existence of pentaquarks has accumulated rapidly in the last three years. If they exist, they would be dramatic examples of hadronic states beyond our well-tested and successful particle models. The positive evidence suggests existence of baryonic objects with widths of at most a few MeV, some displaying exotic quantum numbers, such as baryons with strangeness $S = +1$. The non-observations of these states have often come from reaction channels very different from the positive evidence channels, making comparisons difficult. The situation has now been …

Rise and fall of $Λ$ and $\barΛ$ global polarization in semi-central heavy-ion collisions at HADES, NICA and RHIC energies from the core-corona model

We compute the $Λ$ and $\overlineΛ$ global polarizations in semi-central heavy-ion collisions using the core-corona model where the source of $Λ$'s and $\overlineΛ$'s is taken as consisting of a high-density core and a less dense corona. We show that the overall properties of the polarization excitation functions can be linked to the relative abundance of $Λ$s coming from the core versus those coming from the corona. For low collision energies, the former are more abundant whereas for higher energies the latter become more abundant. The main consequence of this reversing of the relative abunda…