Clustering in low density nuclear matter has been investigated using the NIMROD multidetector at Texas A&M University. Thermal coalescence modes were employed to extract densities, $\rho$, and temperatures, $T$, for evolving systems formed in collisions of $47A$ MeV ${}^{40}\mathrm{Ar}+{}^{112}\mathrm{Sn}$, ${}^{124}\mathrm{Sn}$ and ${}^{64}\mathrm{Zn}+{}^{112}\mathrm{Sn}$, ${}^{124}\mathrm{Sn}$. The yields of $d$, $t$, ${}^3\mathrm{He}$, and ${}^4\mathrm{He}$ have been determined at $\rho =0.002$ to 0.03 $\mathrm{nucleons}/{\mathrm{fm}}^3$ and $T=5$ to 11 MeV. The experimentally derived equilibrium constants for $\alpha$ particle production are compared with those predicted by a number of astrophysical equations of state. The data provide important new constraints on the model calculations.

We compare two types of Tsallis distribution, that is, with and without thermodynamical description, using the experimental data from the STAR, PHENIX, ALICE, and CMS Collaborations on the rapidity and energy dependence of the transverse momentum spectra inp+pcollisions. Both of them can fit the particle spectra well. We show that the Tsallis distribution with thermodynamical description gives lower temperatures than the ones without it. The extra factormT(transverse mass) in the Tsallis distribution with thermodynamical description plays an important role in the discrepancies between the two types of Tsallis distribution. But for the heavy particles, the choice to usemTorET(transverse energy) in the Tsallis distribution becomes more crucial.

Using the experimental data from the STAR, PHENIX, ALICE, and CMS programs on the rapidity and energy dependence of the $p_T$ spectra in $p+p$ collisions, we show that a universal distribution exists. The energy dependence of temperature $T$ and parameter $n$ of the Tsallis distribution are also discussed in detail. A cascade particle production mechanism in $p+p$ collisions is proposed.

In-medium binding energies and Mott points for $d$, $t$, ${}^3\mathrm{He}$ and $\alpha$ clusters in low-density nuclear matter have been determined at specific combinations of temperature and density in low-density nuclear matter produced in collisions of $47A$ MeV ${}^{40}\mathrm{Ar}$ and ${}^{64}\mathrm{Zn}$ projectiles with ${}^{112}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}$ target nuclei. The experimentally derived values of the in-medium modified binding energies are in good agreement with recent theoretical predictions based upon the implementation of Pauli blocking effects in a quantum statistical approach.

The Tsallis distribution has been tested to fit all the particle spectra at mid-rapidity from central events produced in d + Au, Cu + Cu, and Au + Au collisions at RHIC and p + Pb, Pb + Pb collisions at LHC. Even though there are strong medium effects in Cu + Cu and Au + Au collisions, the results show that the Tsallis distribution can be used to fit most of particle spectra in the collisions studied except in Au + Au collisions where some deviations are seen for proton andΛat lowpT. In addition, as the Tsallis distribution can only fit part of the particle spectra produced in Pb + Pb collisions wherepTis up to 20 GeV/c, a new formula with one more fitting degree of freedom is proposed in order to reproduce the entirepTregion.