Tue·Jul 23, 2024Tuesday·July 23, 2024

1. 01*

   Single-proton removal reaction in the IQMD+GEMINI model benchmarked by elemental fragmentation cross sections of ${}^{29-33}\mathrm{Si}$ on carbon at $\sim$230~MeV/nucleon

   Guang-Shuai Li · Jun Su · Satoru Terashima · Jian-Wei Zhao · Er-Xi Xiao · Ji-Chao Zhang · Liu-Chun He · Ge Guo · Wei-Ping Lin · Wen-Jian Lin · Chuan-Ye Liu · Chen-Gui Lu and 15 other authors

   We report on the first measurement of the elemental fragmentation cross sections (EFCSs) of ${}^{29-33}\mathrm{Si}$ on a carbon target at $\sim$230~MeV/nucleon. The experimental data covering charge changes of $\Delta Z$ = 1-4 are reproduced well by the isospin-dependent quantum molecular dynamics (IQMD) coupled with the evaporation GEMINI (IQMD+GEMINI) model. We further explore the mechanisms underlying the single-proton removal reaction in this model framework. We conclude that the cross sections from direct proton knockout exhibit a overall weak dependence on the mass number of $\mathrm{Si}$ projectiles. The proton evaporation induced after the projectile excitation significantly affects the cross sections for neutron-deficient $\mathrm{Si}$ isotopes, while neutron evaporation plays a crucial role in the reactions of neutron-rich $\mathrm{Si}$ isotopes. It is presented that the relative magnitude of one-proton and one-neutron separation energies is an essential factor that influences evaporation processes.

   nucl-exPLB(2024)·5 citations
2. 02*

   Energy Dependence of Polarized $\gamma \gamma \to {\mathbf{e}}^{+}{\mathbf{e}}^{-}$ in Peripheral Au+Au Collisions at RHIC

   The STAR Collaboration

   We report the differential yields at mid-rapidity of the Breit-Wheeler process ($\gamma \gamma \to e^{+}{e}^{-}$) in peripheral Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 54.4 GeV and 200 GeV with the STAR experiment at RHIC, as a function of energy $\sqrt{s_{{}_{\mathrm{NN}}}}$, $e^{+}{e}^{-}$ transverse momentum $p_{\mathrm{T}}$, $p_{\mathrm{T}}^2$, invariant mass $M_{ee}$ and azimuthal angle. In the invariant mass range of 0.4 $<$ $M_{ee}$ $<$ 2.6 GeV/$c^2$ at low transverse momentum ($p_{\mathrm{T}}$ $<$0.15 GeV/$c$), the yields increase while the pair $\sqrt{⟨p_{\mathrm{T}}^2⟩}$ decreases with increasing $\sqrt{s_{{}_{\mathrm{NN}}}}$, a feature is correctly predicted by the QED calculation. The energy dependencies of the measured quantities are sensitive to the nuclear form factor, infrared divergence and photon polarization. The data are compiled and used to extract the charge radius of the Au nucleus.

   nucl-exhep-exPRC(2025)·3 citations
3. 03*

   First experimental test of the ratio method for nuclear-reaction analysis

   S. Ota🇯🇵 · P. Capel🇩🇪 · G. Christian · V. Durant🇩🇪 · K. Hagel · E. Harris🇺🇸 · R. C. Johnson · Z. Luo🇺🇸 · F. M. Nunes🇺🇸 · M. Roosa🇺🇸 · A. Saastamoinen🇺🇸 · D. P. Scriven🇺🇸

   Nuclear halos are very exotic quantal structures observed far from stability. Because of their short lifetime, they are mostly studied through reactions. The ratio method offers a new observable: the ratio of angular differential cross sections for breakup and scattering. It is predicted to be much more sensitive to the projectile structure than individual cross sections thanks to its independence of the reaction process. We test this new observable experimentally for the first time considering the collision of 11Be on C at 22.8 MeV/nucleon. We extend this analysis to similar data recently measured on Pb at 19.1 MeV/nucleon. Both analyses confirm the theoretical predictions, which opens the door to a new era in the study of nuclear structure near the neutron dripline. This should prove invaluable in conjunction with the start of FRIB. The ratio method could also be extended to other fields of quantum physics beyond nuclear reactions.

   nucl-exnucl-thPRL(2025)·1 citation
4. 04*

   Anisotropic flow fluctuation as a possible signature of clustered nuclear geometry in O-O collisions at the Large Hadron Collider

   Suraj Prasad🇮🇳 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳 · Gergely Gábor Barnaföldi🇭🇺

   Nuclei having $4n$ number of nucleons are theorized to possess clusters of $\alpha$ particles (${}^4$He nucleus). The Oxygen nucleus (${}^{16}$O) is a doubly magic nucleus, where the presence of an $\alpha$-clustered nuclear structure grants additional nuclear stability. In this study, we exploit the anisotropic flow coefficients to discern the effects of an $\alpha$-clustered nuclear geometry with respect to a Woods-Saxon nuclear distribution in O--O collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV using a hybrid of IP-Glasma + MUSIC + iSS + UrQMD models. In addition, we use the multi-particle cumulants method to measure anisotropic flow coefficients, such as elliptic flow ($v_2$) and triangular flow ($v_3$), as a function of multiplicity class. Anisotropic flow fluctuations, which are expected to be larger in small collision systems, are also studied for the first time in O--O collisions. It is found that an $\alpha$-clustered nuclear distribution gives rise to an enhanced value of $v_2$ and $v_3$ for the low-multiplicity events. Consequently, a rise in $v_3/v_2$ is also observed for the 0--10\% multiplicity class. Further, for $\alpha$-clustered O--O collisions, fluctuations of $v_2$ are larger for the highest multiplicity events, which decrease as the final-state multiplicity decreases. In contrast, for a Woods-Saxon ${}^{16}$O nucleus, $v_2$ fluctuations show an opposite behavior with decreasing multiplicity. When confronted with experimental data, this study may reveal the importance of the nuclear density profile on the discussed observables and provide physics validation for the hybrid model discussed in this work.

   ↳ nucl-thhep-exhep-phnucl-exPLB(2025)·22 citations
5. 05*

   The Relative Abundance of Correlated Spin-zero Nucleon Pairs

   Raz Yankovich · Ehoud Pazy · Nir Barnea🇮🇱

   We utilize the generalized contact formalism in conjunction with the Woods-Saxon mean-field description of the long-range part of the nuclear wave function to assess the relative prevalence of short-range correlation pairs within atomic nuclei. We validate our approach by fitting experimental charge density results and electron scattering experiments to a very good agreement. Applying our model, we calculate the spin-zero short-range correlations contact ratios. Interestingly, for nuclei with $A>50$, we observe a notable dependence on the neutron-to-proton ratio $N/Z$. Specifically, the probability per nucleon to find neutron-neutron pairs increases, while that of proton-proton pairs decreases, whereas the probability of finding neutron-proton pairs remains relatively constant. To interpret this isospin symmetry breaking effect, we employ a simple model based on generalized Levinger constants, linking it to differences in nuclear proton and neutron radii.

   ↳ nucl-thnucl-exPRC(2025)·4 citations
6. 06*

   Polarized cold-neutron reflectometry at JRR-3/MINE2 for the development of ultracold-neutron spin analyzers for a neutron EDM experiment at TRIUMF

   Takashi Higuchi🇯🇵 · Hiroaki Akatsuka🇯🇵 · Alexis Brossard🇨🇦 · Derek Fujimoto🇨🇦 · Pietro Giampa🇨🇦 · Sean Hansen-Romu🇨🇦 · Kichiji Hatanaka🇯🇵 · Masahiro Hino🇯🇵 · Go Ichikawa🇯🇵 · Sohei Imajo🇯🇵 · Blair Jamieson🇨🇦 · Shinsuke Kawasaki🇯🇵 and 9 other authors

   The neutron electric dipole moment (EDM) is a sensitive probe for currently undiscovered sources of charge-parity symmetry violation. As part of the TRIUMF Ultracold Advanced Neutron (TUCAN) collaboration, we are developing spin analyzers for ultracold neutrons (UCNs) to be used for a next-generation experiment to measure the neutron EDM with unprecedented precision. Spin-state analysis of UCNs constitutes an essential part of the neutron EDM measurement sequence. Magnetized iron films used as spin filters of UCNs are crucial experimental components, whose performance directly influences the statistical sensitivity of the measurement. To test such iron film spin filters, we propose the use of polarized cold-neutron reflectometry, in addition to conventional UCN transmission experiments. The new method provides information on iron film samples complementary to the UCN tests and accelerates the development cycles. We developed a collaborative effort to produce iron film spin filters and test them with cold and ultracold neutrons available at JRR-3/MINE2 and J-PARC/MLF BL05. In this article, we review the methods of neutron EDM measurements, discuss the complementarity of this new approach to test UCN spin filters, provide an overview of our related activities, and present the first results of polarized cold-neutron reflectometry recently conducted at the MINE2 beamline.

   ↳ physics.ins-detnucl-exJ.Phys.Soc.Jap.(2024)·2 citations
7. 07*

   Searching for dark matter with the Th-229 nuclear lineshape from laser spectroscopy

   Elina Fuchs🇩🇪 · Fiona Kirk🇩🇪 · Eric Madge🇮🇱 · Chaitanya Paranjape🇮🇱 · Ekkehard Peik🇩🇪 · Gilad Perez🇮🇱 · Wolfram Ratzinger🇮🇱 · Johannes Tiedau🇩🇪

   The recent laser excitation of the low-lying Th-229 isomer transition is starting a revolution in ultralight dark matter searches. The enhanced sensitivity of this transition to the large class of dark matter models dominantly coupling to quarks and gluons will ultimately allow us to probe coupling strengths eight orders of magnitude smaller than the current bounds from optical atomic clocks, which are mainly sensitive to dark matter couplings to electrons and photons. We argue that, with increasing precision, observations of the Th-229 excitation spectrum will soon give world-leading constraints. Using data from the pioneering laser excitation of Th-229 by Tiedau et al. [Phys. Rev. Lett. 132, 182501 (2024)], we present a first dark matter search in the excitation spectrum. While the exclusion limits of our detailed study of the lineshape are still below the sensitivity of currently operating clock experiments, we project the measurement of Zhang et al. [Nature 663, 63 (2024)] to surpass it.

   ↳ hep-phnucl-exphysics.atom-phPRX(2025)·47 citations
8. 08*

   Entanglement Enabled Intensity Interferometry in ultrarelativistic ultraperipheral nuclear collisions

   James Daniel Brandenburg🇺🇸 · Haowu Duan🇺🇸 · Zhoudunming Tu🇺🇸 · Raju Venugopalan🇺🇸 · Zhangbu Xu🇺🇸

   An important tool in studying the sub-femtoscale spacetime structure of matter in ultrarelativistic heavy-ion collisions is Hanbury-Brown-Twiss (HBT) intensity interferometry of identical particles in the final state of such collisions. We show here that a variant of an entanglement enabled intensity interferometry ($E^2{I}^2$) proposed by Cotler and Wilczek provides a powerful alternative to HBT interferometry in extracting fundamental nonperturbative features of QCD at high energies. In particular, we show that the spatial distributions of color singlet (pomeron) configurations in nuclei can be obtained from exclusive resonant decays of $\rho$-mesons into ${\pi }^{\pm }$-pairs in ultrarelativistic ultraperipheral nuclear collisions (UPCs) at RHIC and the LHC. The $E^2{I}^2$ framework developed here is quite general. It can be employed to extract information on the spin structure of pomeron couplings as well as enhance the discovery potential for rare odderon configurations from exclusive vector meson decays into few-particle final states both in UPCs and at the Electron-Ion Collider.

   ↳ hep-phhep-thnucl-exnucl-thPRResearch(2025)·15 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.