PaperPanorama

Nuclear Experiment·nucl-ex

Thu·Oct 15, 2026

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    Probing the production mechanisms of virtual photons at RHIC

    STAR Collaboration

    We report the measurement of direct virtual photon () in four Au+Au collision energies at = 14.6--54.4 GeV. The yields scale with charged-particle multiplicity () as , independent of collision energies and centralities, exceeding hadronic expectations and indicating notable contribution from QGP phase. At 54.4 GeV, the direct virtual photon mass distributions are further studied over GeV/, and are found to evolve from exponential to power-law form with increasing , signaling a shift from "blackbody" radiation to emission governed by Kroll-Wada formalism.

    nucl-ex
  2. 02

    O(p,)F Reaction and the C and O Isotopic Ratios in Red Giant Branch Stars

    D. Robb · P. McGlynn · M. Aliotta · C. Ananna · F. Barile · L. Barbieri · D. Bemmerer · A. Best · R. Biasissi · A. Boeltzig · R. Bonnell · C. Broggini and 46 other authors

    The O/O isotopic ratio is a widely used tracer of nucleosynthesis and mixing processes in red giant stars. Its value depends on the rates of the proton-capture reactions responsible for the production and destruction of O and O among which the O(p,)F reaction plays a central role, as it involves both isotopes. This work reports on a new measurement of the O(p,)F cross section carried out at the Laboratory for Underground Nuclear Astrophysics (LUNA) over a center-of-mass energy range of 200 - 380 keV, a region previously unexplored by experimental studies. Two complementary techniques were employed: prompt gamma-ray detection and activation. The results obtained with the two techniques are consistent within experimental uncertainties. From the measured cross sections and existing literature data, we evaluate a new thermonuclear reaction rate, which is then used to demonstrate how simultaneous measurements of stellar carbon and oxygen isotopic ratios constrain the initial mass and the extent of the mixing events in red giant branch stars. In particular, we demonstrate how the C/C abundance ratio is primarily sensitive to the temperature T attained during mixing, whereas the O/O abundance ratio is highly sensitive to the initial stellar mass M. Therefore, simultaneous measurements of these isotopic ratios can disentangle and place stringent constraints on M and T, and the remaining uncertainty is now dominated by stellar abundance measurements rather than nuclear-physics inputs.

    nucl-exastro-ph.SR
  3. 03

    Physics with Radioactive Ion Beams at the Nuclear Science Laboratory

    W.S. Porter · D.W. Bardayan · M. Brodeur · C. Dembski · P.D. O'Malley · F. Rivero · W.W. von Seeger · C. Boomershine · O. Bruce · S.R. Carmichael · S. Coil · A.M. Houff and 4 other authors

    The University of Notre Dame is home to a rich history of nuclear science efforts, including some of the earliest developments in the production and creation of radioactive ion beams (RIBs). The resulting TwinSol facility stands as the longest continuously-operating RIB facility in the United States, and has enabled a wide range of experimental efforts in nuclear structure, astrophysics and fundamental symmetries through in-flight RIBs one to two nucleons from stability. A recent upgrade to TwinSol via a third solenoid constituted the founding of the TriSol facility, which provides cleaner, better-focused RIBs to downstream experiments. In this paper, we present a summary of RIB science at the Nuclear Science Laboratory (NSL) with both TwinSol and TriSol and discuss recent upgrades and future experimental plans at the facilities.

    nucl-exphysics.acc-phphysics.ins-det
  4. 04

    Strange-quark-number-dependent response to partonic dynamics in baryon-rich Au+Au collisions

    Di Zhao · Xun Zhu · Gao-Chan Yong

    We identify a strange-quark-number-dependent hierarchy in the response to explicit partonic dynamics by comparing PHSD5.2 with its hadron--string limit in baryon-rich Au+Au collisions at --~GeV. Crossing the local conversion threshold alone does not ensure a visible final-state signal: abundant-hadron flow changes little at 3--4.5~GeV, whereas the fractional yield response becomes ordered at 6.2--7.2~GeV, reaching --, , and at 7.2~GeV. The hierarchy is consistent with an enlarged recombination phase space for strange constituents released from different pre-hadronic sources, but does not by itself establish an increase in the total abundance or stronger strange-quark clustering. Since is a model-defined response rather than a direct observable, matched excitation functions of and , together with high- proton elliptic flow, provide experimentally accessible discriminants between the predicted PHSD and HSD dynamics.

    ↳ nucl-thnucl-exPhys. Lett. B 882 (2026) 141031
  5. 05

    Collective-flow signatures of bubble nuclei in intermediate-energy projectile fragmentation reactions

    Ge Ren · Chun-Wang Ma · Xi-Guang Cao · Kai-Xuan Cheng · Jie Pu

    Characterized by central density depletion, bubble nuclei represent an important class of exotic nuclear structures. Collective flow in the Ca+Be projectile fragmentation reaction at 140 MeV/u is investigated using the extended quantum molecular dynamics (EQMD) model with a parameter on of the isoscalar monopole excitation strength . The projectile is initialized as a relaxed ten- cluster configuration exhibiting a bubble-like density distribution. The results reveal that increasing modifies the density distribution and the size of the depleted central region of bubble, producing pronounced changes in fragment yields and collective flow around . Below this value, heavy-fragment production plays a significant role, while the directed flow of protons and neutrons remains predominantly negative, indicating preferential emission toward the target side. Above , enhanced expansion of the central low-density region suppresses heavy residues and drives toward positive values. In contrast, preformed clusters show different responses, reflecting their origin in the initial cluster configuration rather than solely in secondary decay. At low excitation, the cluster flow exhibits a pronounced impact-parameter dependence, whereas stronger excitation weakens cluster binding and suppresses directional anisotropy, driving the flow close to zero. The rapidity slopes of the flow coefficients also vary systematically with , tracing changes in emission anisotropy during expansion. These findings extend traditional static descriptions by probing the dynamical evolution of exotic structures in heavy-ion reactions and the contrasting collective-flow behavior of preformed clusters and single nucleons constitutes a sensitive dynamical probe of bubble-like structures.

    ↳ nucl-thnucl-ex
  6. 06

    Constraining three-nucleon forces in nuclear lattice effective field theory

    Serdar Elhatisari · Ulf-G. Meißner · Zhengxue Ren · Shuang Zhang

    We study short-range three-nucleon forces (3NFs) in nuclear lattice effective field theory with a chiral two-nucleon interaction at NLO. The one-pion-exchange () and contact () terms of the leading 3NF are decomposed into locally and non-locally smeared components and supplemented by partial-wave-resolved pair contacts coupled to the density of a third nucleon. We determine their coefficients from nuclear binding energies for nuclei in the mass range from to and neutron--alpha finite-volume energies. This allows to work out the minimal three-nucleon force that can be used for future precision studies in NLEFT.

    ↳ nucl-thhep-latnucl-ex