|
LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2024). Observation of Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the Ω0c Baryon. Phys. Rev. Lett., 132(8), 081802–11pp.
Abstract: The first observation of the singly Cabibbo-suppressed 0c -> -K thorn and 0c -> -z thorn decays is reported, using proton -proton collision data at a center -of -mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be Bo0c ->-K thorn thorn Bo0c ->-z thorn thorn 1/4 1/26.08 ⠂ 0.51ostat thorn ⠂ 0.40osyst thorn ⠃%; Bo0c ->-z thorn thorn Bo0c ->-z thorn thorn 1/4 1/215.81 ⠂ 0.87ostat thorn ⠂ 0.44osyst thorn ⠂ 0.16oext thorn ⠃%. In addition, using the 0c -> -z thorn decay channel, the 0c baryon mass is measured to be Mo0c thorn 1/4 2695.28 ⠂ 0.07ostat thorn ⠂ 0.27osyst thorn ⠂ 0.30oext thorn MeV; improving the precision of the previous world average by a factor of 4.
|
|
|
ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2024). Observation of WZγ Production in pp Collisions at √s=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 132(2), 021802–21pp.
Abstract: This Letter reports the observation of WZ gamma production and a measurement of its cross section using 140.1 +/- 1.2 fb(-1) of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the bosons decaying leptonically, pp -> WZ gamma -> l'(perpendicular to)nu l(+) l(-)gamma (l(')(+) = e, mu), is measured in a fiducial phasespace region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01 +/- 0.30(stat) +/- 0.16(syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50 +/- 0.06 fb. The observed significance of the WZ gamma signal is 6.3 sigma, compared with an expected significance of 5.0 sigma.
|
|
|
ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2024). Observation of Wγγ triboson production in proton-proton collisions at √s=13 TeV with the ATLAS detector. Phys. Lett. B, 848, 138400–24pp.
Abstract: This letter reports the observation of () production in proton-proton collisions. This measurement uses the full Run 2 sample of events recorded at a center-of-mass energy of root= 13 TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb-1. Events with a leptonically-decaying boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of 5.6 standard deviations. The inclusive fiducial production cross section of () and () events is measured to be fid = 13.8 +/- 1.1(stat)+2.1-2.0(syst) +/- 0.1(lumi) fb, in agreement with the Standard Model prediction.
|
|
|
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.
|
|
|
ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Performance and calibration of quark/gluon-jet taggers using 140 fb-1 of pp collisions at √s=13 TeV with the ATLAS detector. Chin. Phys. C, 48(2), 023001–25pp.
Abstract: The identification of jets originating from quarks and gluons, often referred to as quark/gluon tagging, plays an important role in various analyses performed at the Large Hadron Collider, as Standard Model measurements and searches for new particles decaying to quarks often rely on suppressing a large gluon-induced background. This paper describes the measurement of the efficiencies of quark/gluon taggers developed within the ATLAS Collaboration, using root s = 13 TeV proton-proton collision data with an integrated luminosity of 140 fb(-1) collected by the ATLAS experiment. Two taggers with high performances in rejecting jets from gluon over jets from quarks are studied: one tagger is based on requirements on the number of inner-detector tracks associated with the jet, and the other combines several jet substructure observables using a boosted decision tree. A method is established to determine the quark/gluon fraction in data, by using quark/gluon-enriched subsamples defined by the jet pseudorapidity. Differences in tagging efficiency between data and simulation are provided for jets with transverse momentum between 500 GeV and 2 TeV and for multiple tagger working points.
|
|
|
Bout, R., Busto, J., Cecchini, V., Charpentier, P., Chapellier, M., Dastgheibi-Fard, A., et al. (2024). Perspectives of a single-anode cylindrical chamber operating in ionization mode and high gas pressure. Eur. Phys. J. C, 84(5), 512–14pp.
Abstract: As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of 210 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>{210} $$\end{document} Po (5.3 MeV alpha \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document} ) and a diffuse source of 222 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$<^>{222}$$\end{document} Rn (5.5 MeV alpha \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha $$\end{document} ). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached.
|
|
|
Domcke, V., Ema, Y., & Sandner, S. (2024). Perturbatively including inhomogeneities in axion inflation. J. Cosmol. Astropart. Phys., 03(3), 019–24pp.
Abstract: Axion inflation, i.e. an axion-like inflaton coupled to an Abelian gauge field through a Chern-Simons interaction, comes with a rich and testable phenomenology. This is particularly true in the strong backreaction regime, where the gauge field production heavily impacts the axion dynamics. Lattice simulations have recently demonstrated the importance of accounting for inhomogeneities of the axion field in this regime. We propose a perturbative scheme to account for these inhomogeneities while maintaining high computational efficiency. Our goal is to accurately capture deviations from the homogeneous axion field approximation within the perturbative regime as well as self -consistently determine the onset of the nonperturbative regime.
|
|
|
Ferreiro, A., Monin, S., & Torrenti, F. (2024). Physical scale adiabatic regularization in cosmological spacetimes. Phys. Rev. D, 109(4), 045015–16pp.
Abstract: We develop a new regularization method for the stress -energy tensor and the two -point function of free quantum scalar fields propagating in cosmological spacetimes. We proceed by extending the adiabatic regularization scheme with the introduction of two additional mass scales. By setting them to the order of the physical scale of the studied scenario, we obtain ultraviolet -regularized quantities that do not distort the power spectra amplitude at the infrared scales amplified by the expansion of the Universe. This is not ensured by the standard adiabatic approach. We also show how our proposed subtraction terms can be interpreted as a renormalization of coupling constants in the Einstein equations. We finally illustrate our proposed regularization method in two scenarios of cosmological interest: de Sitter inflation and geometric reheating.
|
|
|
Jungclaus, A., Doornenbal, P., Acosta, J., Vaquero, V., Browne, F., Cortes, M. L., et al. (2024). Position of the single-particle 3/2- state in 135Sn and the N = 90 subshell closure. Phys. Lett. B, 851, 138561–5pp.
Abstract: The decay of excited states of the nucleus Sn-135, with three neutrons outside the doubly-magic Sn-132 core, was studied in an experiment performed at the Radioactive Isotope Beam Factory at RIKEN. Several gamma rays emitted from excited Sn-135 ions were observed following one-neutron and one-neutron-one-proton removal from Sn-136 and Sb-137 beams, respectively, on a beryllium target at relativistic energies. Based on the analogy to 133Sn populated via one-neutron removal from Sn-134, an excitation energy of 695(15) keV is assigned to the 3/2(-) state with strongest single-particle character in 135Sn. This result provides the first direct information about the evolution of the neutron shell structure beyond N = 82 and thus allows for a crucial test of shellmodel calculations in this region. The experimental findings are in full agreement with calculations performed employing microscopic effective two-body interactions derived from CD-Bonn and N3LO nucleon-nucleon potentials, which do not predict a pronounced subshell gap at neutron number N=90. The occurrence of such a gap in Sn-140, i.e., when the 1f(7/2) orbital is completely filled, had been proposed in the past, in analogy to the magicity of Ca-48, featuring a completely filled 0f(7/2) orbital one harmonic oscillator shell below.
|
|
|
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.
|
|