Signatures of α clustering in light nuclei from relativistic nuclear collisions

E-by-e fluctuations of initial conditions in interactions of light, intermediate and heavy nuclei at energies 4 - 200 GeV per nucleon

A better understanding of initial conditions of nuclear interactions is one of the most important heavy ion physics problems. The paper considers these problems in the centrality selected interactions of light (C, O, Ne) – (beam) and heavy (Au, Pb) – (beam) ions with light (C/N/O) – (target) and heavy (Ag/Br) – (target) nuclei using the data of JINR-AGS-SPS target emulsion experiments with limited statistics. To reveal a possible system structure dependence, the analyses of E-by-E fluctuations on the longitudinal event shape and multiplicity have been performed, vertically and horizontally.

Elliptic Flow in Ultrarelativistic Collisions with Polarized Deuterons

Predictions are made for elliptic flow in collisions of polarized deuterons with a heavy nucleus. It is shown that the eccentricity of the initial fireball, evaluated with respect to the deuteron polarization axis perpendicular to the beam direction, has a substantial magnitude for collisions of highest multiplicity. Within the Glauber approach we obtain ∼7% for the deuteron states with spin projection 0, and ∼-3% for spin projection ±1. We propose to measure the elliptic flow coefficient as the second order harmonic coefficient in the azimuthal distribution of produced charged hadrons with respect to the fixed polarization axis. Collective expansion yields a value of the order of 1% for this quantity, as compared to zero in the absence of polarization and/or collectivity. Such a vivid rotational symmetry breaking could be measured with the current experimental accuracy of the relativistic heavy-ion experiments. The effect has a fundamental significance for understanding the nature of dynamics in small systems, as its experimental confirmation would prove the presence of the shape-flow transmutation mechanism, typical of hydrodynamic expansion or rescattering in the later stages of the fireball evolution.

Giant dipole resonance as a fingerprint of α clustering configurations in 12C and 16O

It is studied how the α cluster degrees of freedom, such as α clustering configurations close to the α decay threshold in (12)C and (16)O, including the linear chain, triangle, square, kite, and tetrahedron, affect nuclear collective vibrations with a microscopic dynamical approach, which can describe properties of nuclear ground states well across the nuclide chart and reproduce the standard giant dipole resonance (GDR) of (16)O quite nicely. It is found that the GDR spectrum is highly fragmented into several apparent peaks due to the α structure. The different α cluster configurations in (12)C and (16)O have corresponding characteristic spectra of GDR. The number and centroid energies of peaks in the GDR spectra can be reasonably explained by the geometrical and dynamical symmetries of α clustering configurations. Therefore, the GDR can be regarded as a very effective probe to diagnose the different α cluster configurations in light nuclei.