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Illana, A. et al, & Perez-Vidal, R. M. (2024). Octupole correlations in the N = Z+2=56 110Xe nucleus. Phys. Lett. B, 848, 138371–7pp.
Abstract: This letter reports on the first observation of an octupole band in the neutron-deficient (N = Z + 2) nucleus Xe-110. The Xe-110 nuclei were produced via the Fe-54(Ni-58,2n) fusion-evaporation reaction. The emitted gamma rays were detected using the jurogam 3 gamma-ray spectrometer, while the fusion-evaporation residues were separated with the MARA separator at the Accelerator Laboratory of the University of Jyv & auml;skyl & auml;, Finland. The experimental observation of the low-lying 3(-) and 5(-) states and inter-band E1 transitions between the ground-state band and the octupole band proves the importance of octupole correlations in this region. These new experimental data combined with theoretical calculations using the symmetry-conserving configuration-mixing method, based on a Gogny energy density functional, have been interpreted as an evidence of enhanced octupole correlations in neutron-deficient xenon isotopes.
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Irles, A., Marquez, J. P., Pöschl, R., Richard, F., Saibel, A., Yamamoto, H., et al. (2024). Probing gauge-Higgs unification models at the ILC with quark-antiquark forward-backward asymmetry at center-of-mass energies above the Z mass. Eur. Phys. J. C, 84(5), 537–17pp.
Abstract: The International Linear Collider (ILC) will allow the precise study of e(-)e(+)-> q (q) over bar interactions at different center-of-mass energies from the Z-pole to 1 TeV. In this paper, we discuss the experimental prospects for measuring differential observables in e(-)e(+)-> b (b) over bar and e(-)e(+) -> c (c) over bar at the ILC baseline energies, 250 and 500 GeV. The study is based on full simulation and reconstruction of the International Large Detector (ILD) concept. Two gauge-Higgs unification models predicting new high-mass resonances beyond the Standard Model are discussed. These models predict sizable deviations of the forward-backward observables at the ILC running above the Z mass and with longitudinally polarized electron and positron beams. The ability of the ILC to probe these models via high-precision measurements of the forward-backward asymmetry is discussed. Alternative scenarios at other energies and beam polarization schemes are also discussed, extrapolating the estimated uncertainties from the two baseline scenarios.
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ATLAS Collaboration(Aad, G. et al), Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Castillo, F. L., Castillo Gimenez, V., et al. (2024). Search for quantum black hole production in lepton plus jet final states using proton-proton collisions at √s=13 TeV with the ATLAS detector. Phys. Rev. D, 109(3), 032010–28pp.
Abstract: A search for quantum black holes in electron + jet and muon + jet invariant mass spectra is performed with 140 fb(-1) of data collected by the ATLAS detector in proton-proton collisions at root s = 13 TeV at the Large Hadron Collider. The observed invariant mass spectrum of lepton + jet pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.
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Jueid, A., Kip, J., Ruiz de Austri, R., & Skands, P. (2024). The Strong Force meets the Dark Sector: a robust estimate of QCD uncertainties for anti-matter dark matter searches. J. High Energy Phys., 02(2), 119–48pp.
Abstract: In dark-matter annihilation channels to hadronic final states, stable particles – such as positrons, photons, antiprotons, and antineutrinos – are produced via complex sequences of phenomena including QED/QCD radiation, hadronisation, and hadron decays. These processes are normally modelled by Monte Carlo (MC) event generators whose limited accuracy imply intrinsic QCD uncertainties on the predictions for indirect-detection experiments like Fermi-LAT, Pamela, IceCube or Ams-02. In this article, we perform a comprehensive analysis of QCD uncertainties, meaning both perturbative and nonperturbative sources of uncertainty are included – estimated via variations of MC renormalization-scale and fragmentation-function parameters, respectively – in antimatter spectra from dark-matter annihilation, based on parametric variations of the Pythia 8 event generator. After performing several retunings of light-quark fragmentation functions, we define a set of variations that span a conservative estimate of the QCD uncertainties. We estimate the effects on antimatter spectra for various annihilation channels and final-state particle species, and discuss their impact on fitted values for the dark-matter mass and thermally-averaged annihilation cross section. We find dramatic impacts which can go up to O(10%) for the annihilation cross section. We provide the spectra in tabulated form including QCD uncertainties and code snippets to perform fast dark-matter fits, in this github repository.
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Jungclaus, A. et al, Gadea, A., & Montaner-Piza, A. (2024). Excited-State Half-Lives in 130 Cd and the Isospin Dependence of Effective Charges. Phys. Rev. Lett., 132(22), 222501–7pp.
Abstract: The known I pi = 8 & thorn; 1 , E x = 2129-keV isomer in the semimagic nucleus 130 Cd 82 was populated in the projectile fission of a 238 U beam at the Radioactive Isotope Beam Factory at RIKEN. The high counting statistics of the accumulated data allowed us to determine the excitation energy, E x = 2001.2(7) keV, and half-life, T 1 =2 = 57(3) ns, of the I pi = 6 & thorn; 1 state based on gamma gamma coincidence information. Furthermore, the halflife of the 8 & thorn; 1 state, T 1 =2 = 224(4) ns, was remeasured with high precision. The new experimental information, combined with available data for 134 Sn and large-scale shell model calculations, allowed us to extract proton and neutron effective charges for 132 Sn, a doubly magic nucleus far -off stability. A comparison to analogous information for 100 Sn provides first reliable information regarding the isospin dependence of the isoscalar and isovector effective charges in heavy nuclei.
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