Mon·Dec 23, 2024Monday·December 23, 2024

1. 01*

   Measurement of light-by-light scattering and the Breit-Wheeler process, and search for axion-like particles in ultraperipheral PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   CMS Collaboration

   Measurements of light-by-light scattering (LbL, $\gamma \gamma$ $\to$ $\gamma \gamma$) and the Breit-Wheeler process (BW, $\gamma \gamma$ $\to$ ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$) are reported in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV. The data sample, corresponding to an integrated luminosity of 1.7 nb${}^{-1}$, was collected by the CMS experiment at the CERN LHC in 2018. Events with an exclusively produced $\gamma \gamma$ or ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ pair with invariant masses $m^{\gamma \gamma ,\mathrm{ee}}$ $>$ 5 GeV, along with other fiducial criteria, are selected. The measured BW fiducial production cross section, ${\sigma }_{\text{fid}}$($\gamma \gamma$ $\to$ ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$) = 263.5 $\pm$ 1.8 (stat) $\pm$ 17.8 (syst) $\mu$b, as well as the differential distributions for various kinematic observables, are in agreement with leading-order quantum electrodynamics predictions complemented with final-state photon radiation. The measured differential BW cross sections allow discriminating between different theoretical descriptions of the photon flux of the lead ion. In the LbL final state, 26 exclusive diphoton candidate events are observed compared with 12.0 $\pm$ 2.9 expected for the background. Combined with previous results, the observed significance of the LbL signal with respect to the background-only hypothesis is above five standard deviations. The measured fiducial LbL scattering cross section, ${\sigma }_{\text{fid}}(\gamma \gamma$ $\to$ $\gamma \gamma )$ = 107 $\pm$ 24 (stat) $\pm$ 13 (syst) nb, is in agreement with next-to-leading-order predictions. Limits on the production of axion-like particles coupled to photons are set over the mass range 5-100 GeV, including the most stringent limits to date in the range of 5-10 GeV.

   nucl-exhep-exJHEP(2025)·37 citations
2. 02*

   Azimuthal anisotropies of charged particles with high transverse momentum in Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV with the ATLAS detector

   ATLAS Collaboration

   A measurement is presented of elliptic ($v_2$) and triangular ($v_3$) azimuthal anisotropy coefficients for charged particles produced in Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}=5.02$ TeV using a dataset corresponding to an integrated luminosity of $0.44$ nb${}^{-1}$ collected with the ATLAS detector at the LHC in 2018. The values of $v_2$ and $v_3$ are measured for charged particles over a wide range of transverse momentum ($p_{\text{T}}$), 1-400 GeV, and Pb+Pb collision centrality, 0-60%, using the scalar product and multiparticle cumulant methods. These methods are sensitive to event-by-event fluctuations and nonflow effects in the measurements of azimuthal anisotropies. Positive values of $v_2$ are observed up to a $p_{\text{T}}$ of approximately 100 GeV from both methods across all centrality intervals. Positive values of $v_3$ are observed up to approximately 25 GeV using both methods, though the application of the three-subevent technique to the multiparticle cumulant method leads to significant changes at the highest $p_{\text{T}}$. At high $p_{\text{T}}$ ($p_{\text{T}}⪆10$ GeV), charged particles are dominantly from jet fragmentation. These jets, and hence the measurements presented here, are sensitive to the path-length dependence of parton energy loss in the quark-gluon plasma produced in Pb+Pb collisions.

   nucl-exhep-exPRC(2025)·8 citations
3. 03*

   First measurement of symmetric cumulants of hexagonal flow harmonics in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV

   ALICE Collaboration

   Correlations between event-by-event fluctuations of anisotropic flow harmonics are measured in Pb$-$Pb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV, as recorded by the ALICE detector at the LHC. This study presents correlations up to the hexagonal flow harmonic, $v_6$, which was measured for the first time. The magnitudes of these higher-order correlations are found to vary as a function of collision centrality and harmonic order. These measurements are compared to viscous hydrodynamic model calculations with EKRT initial conditions and to the iEBE-VISHNU model with TRENTo initial conditions. The observed discrepancies between the data and the model calculations vary depending on the harmonic combinations. Due to the sensitivity of model parameters estimated with Bayesian analyses to these higher-order observables, the results presented in this work provide new and independent constraints on the initial conditions and transport properties in theoretical models used to describe the system created in heavy-ion collisions.

   nucl-exPRC(2025)·4 citations
4. 04*

   Meaurement of spin vs. TKE of ${}^{144}$Ba produced in spontaneous fission of ${}^{252}$Cf

   N.P. Giha🇺🇸 · S. Marin🇺🇸 · I.A. Tolstukhin🇺🇸 · M.B. Oberling🇺🇸 · R.A. Knaack🇺🇸 · C. Mueller-Gatermann🇺🇸 · A. Korichi🇫🇷 · K. Bhatt🇺🇸 · M.P. Carpenter🇺🇸 · C. Fougères🇺🇸 · V. Karayonchev🇺🇸 · B.P. Kay🇺🇸 and 12 other authors

   We measure the average spin of ${}^{144}$Ba, a common fragment produced in ${}^{252}$Cf(sf), as a function of the total kinetic energy (TKE). We combined for the first time a twin Frisch-gridded ionization chamber with a world-class $\gamma$-ray spectrometer that was designed to measure high-multiplicity $\gamma$-ray events, Gammasphere. The chamber, loaded with a ${}^{252}$Cf(sf) source, provides a fission trigger, the TKE of the fragments, the approximate fragment masses, and the polar angle of the fission axis. Gammasphere provides the total $\gamma$-ray yield, fragment identification through the tagging of decay $\gamma$ rays, and the feeding of rotational bands in the fragments. We determine the dependence of the average spin of ${}^{144}$Ba on the fragments' TKE by correlating the fragment properties with the distribution of discrete levels that are fed. We find that the average spin only changes by about $0.5$ $\hslash$ across the TKE range of 158-203 MeV. The virtual independence of the spin on TKE suggests that spin is not solely generated through the statistical excitation of rotational modes, and more complex mechanisms are required.

   nucl-exPRC(2025)·4 citations
5. 05*

   Rare multi-nucleon decays with the full data sets of the Majorana Demonstrator

   I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · E. Blalock🇺🇸 · B. Bos🇺🇸 · M. Busch🇺🇸 · Y.-D. Chan🇺🇸 · J.R. Chapman🇺🇸 · C.D. Christofferson🇺🇸 · P.-H. Chu🇺🇸 · C. Cuesta🇪🇸 · J.A. Detwiler🇺🇸 and 30 other authors

   The Majorana Demonstrator was an ultra-low-background experiment designed for neutrinoless double-beta decay ($0\nu \beta \beta$) investigation in ${}^{76}$Ge. Located at the Sanford Underground Research Facility in Lead, South Dakota, the Demonstrator utilized modular high-purity Ge detector arrays within shielded vacuum cryostats, operating deep underground. The arrays, with a capacity of up to 40.4 kg (27.2 kg enriched to $\sim 88\%$ in ${}^{76}$Ge), have accumulated the full data set, totaling 64.5 kg yr of enriched active exposure and 27.4 kg yr of exposure for natural detectors. Our updated search improves previously explored three-nucleon decay modes in Ge isotopes, setting new partial lifetime limits of $1.83\times 10^{26}$ years (90\% confidence level) for ${}^{76}$Ge($ppp$) $\to$ ${}^{73}$Cu e${}^{+}{\pi }^{+}{\pi }^{+}$ and ${}^{76}$Ge($ppn$) $\to$ ${}^{73}$Zn e${}^{+}{\pi }^{+}$. The partial lifetime limit for the fully inclusive tri-proton decay mode of ${}^{76}$Ge is found to be $2.1\times 10^{25}$ yr. Furthermore, we have updated limits for corresponding multi-nucleon decays.

   nucl-exPRC(2025)·2 citations
6. 06*

   High precision X-ray spectroscopy of kaonic neon

   F Sgaramella🇮🇹 · D Sirghi🇮🇹 · K Toho🇯🇵 · F Clozza🇮🇹 · L Abbene🇫🇷 · C Amsler🇦🇹 · F Artibani🇮🇹 · M Bazzi🇮🇹 · G Borghi🇮🇹 · D Bosnar🇭🇷 · M Bragadireanu🇷🇴 · A Buttacavoli🇫🇷 and 32 other authors

   The high-precision kaonic neon X-ray transitions measurement performed by the SIDDHARTA-2 collaboration at the DA$\Phi$NE collider is reported. Both the X-ray energies and yields for high-n transitions were measured, demonstrating the feasibility of sub-eV Xray spectroscopy for kaonic atoms using low-Z gaseous targets. The measurement provides valuable insights into the de-excitation processes in kaonic atoms, providing new input data for the refinement of the corresponding theoretical models, and a framework for testing Quantum Electrodynamics in strange exotic atoms.

   nucl-exhep-exPLB(2025)·13 citations
7. 07*

   Isolated one-phonon mixed-symmetry 2+ state of the radioactive neutron-rich nuclide 132Te

   T. Stetz · H. Mayr · V. Werner · N. Pietralla · Y. Tsunoda · T. Otsuka · G. Rainovski · T. Beck · R. Borcea · S. Calinescu · C. Costache · I. E. Dinescu and 11 other authors

   The $M1$ transition strengths between excited $2^{+}$ states of the neutron-rich, radioactive nuclide ${}^{132}$Te have been studied through direct lifetime measurements using the Doppler-shift attenuation method in a two-neutron transfer reaction on a ${}^{130}$Te target. An unambiguous identification of the lowest-lying mixed-symmetry $2^{+}$ state has been achieved on the basis of the large $B(M1;2_2^{+}\to 2_1^{+}$)=0.18(2) ${\mu }_{\mathrm{N}}^2$ transition strength, in agreement with shell-model calculations. Results are compared to the shell model, and the analysis of both, data and calculations, unambiguously identifies the second-excited $2^{+}$ state of ${}^{132}$Te as the one-quadrupole phonon mixed-symmetry state of this isotope. A lowering of the energy and $B(M1;2_{\mathrm{ms}}^{+}\to 2_1^{+})$ strength within the $N$=80 isotones toward the $Z$=50 shell closure is observed, which goes alongside with the lowering of the $E2$ collectivity approaching the magic proton shell.

   nucl-exPRC(2025)·1 citation
8. 08*

   Neural network biased corrections: Cautionary study in background corrections for quenched jets

   David Stewart🇺🇸 · Joern Putschke🇺🇸

   Jets clustered from heavy ion collision measurements combine a dense background of particles with those actually resulting from a hard partonic scattering. The background contribution to jet transverse momentum ($p_T$) may be corrected by subtracting the collision average background; however, the background inhomogeneity limits the resolution of this correction. Many recent studies have embedded jets into heavy ion backgrounds and demonstrated a markedly improved background correction is achievable by using neural networks (NNs) trained with aspects of jet substructure which are used to map measured jet $p_{\mathrm{T}}$ to the embedded truth jet $p_{\mathrm{T}}$. However, jet quenching in heavy ion collisions modifies jet substructure, and correspondingly biases the NNs' background corrections. This study investigates those biases by using simulations of jet quenching in central Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{GeV}/c$ with hydrodynamically modeled quark-gluon plasma (QGP) evolution. To demonstrate the magnitude of the effect of such biases in measurement, a leading jet nuclear modification factor ($R_{\mathrm{AA}}$) is calculated and reported using the NN background correction on jets quenched utilizing a brick of QGP.

   ↳ physics.data-anhep-exnucl-exPRC(2025)·5 citations
9. 09*

   Constraining neutron star properties through parity-violating electron scattering experiments and relativistic point coupling interactions

   P.S. Koliogiannis🇭🇷 · E. Yuksel🇬🇧 · N. Paar🇭🇷

   Parity-violating electron scattering experiments on ${}^{48}\mathrm{Ca}$ (CREX) and ${}^{208}\mathrm{Pb}$ (PREX-2) offer valuable insight into the isovector properties of finite nuclei, providing constraints for the density dependence of the nuclear equation of state, which is crucial for understanding astrophysical phenomena. In this work, we establish functional dependencies between the properties of finite nuclei-such as weak charge form factors and neutron skin thickness-and the bulk properties of neutron stars, including tidal deformability from binary neutron star mergers and neutron star radii. The dependencies are formulated by introducing a family of $\beta$-equilibrated equations of state based on relativistic energy density functionals with point coupling interactions. The charge minus the weak form factors derived from CREX and PREX-2 measurements, combined with the observational constraints on tidal deformability from the GW170817 event, are used to constrain the symmetry energy and neutron star radii. Notably, the energy density expanded up to the fourth order in symmetry energy yields larger radii compared to calculations limited to the second order term. However, the results reveal a discrepancy between the constraints provided by the CREX and PREX-2 experiments. For a more quantitative assessment, higher precision parity-violating electron scattering data and neutron star observations are required.

   ↳ nucl-thastro-ph.HEastro-ph.SRnucl-exPLB(2025)·5 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.