Mon·Jun 10, 2024Monday·June 10, 2024

1. 01*

   Observation and spectroscopy of proton-unbound nucleus ${}^{21}$Al

   D. Kostyleva🇩🇪 · X.-D. Xu🇨🇳 · I. Mukha🇩🇪 · L. Acosta🇪🇸 · M. Bajzek🇩🇪 · E. Casarejos🇪🇸 · A.A. Ciemny🇵🇱 · D. Cortina-Gil🇪🇸 · W. Dominik🇵🇱 · J.A. Dueñas🇪🇸 · J. M. Espino🇪🇸 · A. Estradé🇺🇸 and 42 other authors

   We report on the observation of previously-unknown isotope ${}^{21}$Al, the first unbound aluminum isotope located beyond the proton dripline. The ${}^{21}$Al nucleus decays by one-proton (1p) emission, and its in-flight decays were detected by tracking trajectories of all decay products with micro-strip silicon detectors. The 1p-emission processes were studied by analyses of the measured angular correlations of decay products ${}^{20}$Mg+p. The 1p-decay energies of ground and low-lying excited states of ${}^{21}$Al, its mass excess and proton separation energy value $S_p$=$-1.1(1)$ MeV were determined.

   nucl-exPRC(2024)·10 citations
2. 02*

   Proton 3D reconstruction with T-odd TMD gluon densities

   Alessandro Bacchetta🇮🇹 · Francesco Giovanni Celiberto🇪🇸 · Marco Radici🇮🇹

   We present studies aimed at probing the 3D gluon content of the proton through spin-dependent TMD gluon densities, computed by means of the spectator-model approach. Our formalism incorporates a fit-based modulation function for the spectator mass, designed to capture longitudinal-momentum effects across a broad kinematic range. Special emphasis is placed on the time-reversal even Boer-Mulders and the time-reversal odd Sivers functions. Accurate understanding of these functions is crucial for conducting precise 3D analyses of nucleons, highlighting the importance of collaborative efforts between the LHC and EIC Communities.

   ↳ hep-phhep-exnucl-exnucl-thPoS(2024)·8 citations
3. 03*

   Unraveling Trace Anomaly of Supradense Matter via Neutron Star Compactness Scaling

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸

   The trace anomaly $\Delta \equiv 1/3-P/\epsilon =1/3-\varphi$ quantifies the possibly broken conformal symmetry in supradense matter under pressure $P$ at energy density $\epsilon$. Perturbative QCD (pQCD) predicts a vanishing $\Delta$ at extremely high energy or baryon densities when the conformal symmetry is realized but its behavior at intermediate densities reachable in neutron stars (NSs) are still very uncertain. The extraction of $\Delta$ from NS observations strongly depends on the employed model for nuclear Equation of State (EOS). Using the IPAD-TOV method based on an Intrinsic and Perturbatively Analysis of the Dimensionless (IPAD) Tolman-Oppenheimer-Volkoff (TOV) equations that are further verified numerically by using $10^5$ EOSs generated randomly with a meta-model in a very broad EOS parameter space constrained by terrestrial nuclear experiments and astrophysical observations, here we first show that the compactness $\xi \equiv G{M}_{\mathrm{NS}}/R{c}^2\equiv M_{\mathrm{NS}}/R$ of a NS with mass $M_{\mathrm{NS}}$ and radius $R$ scales very accurately with ${\overline{\Pi }}_{\mathrm{c}}\equiv {\Pi }_{\mathrm{c}}\cdot (1+18\text{x}/25)\equiv \text{x}/(1+3{\text{x}}^2+4\text{x})\cdot (1+18\mathrm{X}/25)$ where $\text{x}\equiv {\varphi }_{\mathrm{c}}=P_{\mathrm{c}}/{\epsilon }_{\mathrm{c}}$ is the ratio of pressure over energy density at NS centers. The scaling of NS compactness thus enables one to readily read off the central trace anomaly ${\Delta }_{\mathrm{c}}=1/3-\text{x}$ directly from the observational data of either the mass-radius or red-shift measurements. We then demonstrate indeed that the available NS data themselves from recent X-ray and gravitational wave observations can determine model-insensitively the trace anomaly as a function of energy density in NS cores, providing a stringent test of existing NS models and a clear guidance in a new direction for further understanding the nature and EOS of supradense matter.

   ↳ astro-ph.HEhep-phhep-thnucl-ex+1PRD(2025)·19 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.