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Gao, F., & Oldengott, I. M. (2022). Cosmology Meets Functional QCD: First-Order Cosmic QCD Transition Induced by Large Lepton Asymmetries. Phys. Rev. Lett., 128(13), 131301–6pp.
Abstract: The lepton flavor asymmetries of the Universe are observationally almost unconstrained before the onset of neutrino oscillations. We calculate the cosmic trajectory during the cosmic QCD epoch in the presence of large lepton flavor asymmetries. By including QCD thermodynamic quantities derived from functional QCD methods in our calculation, our work reveals for the first time the possibility of a first-order cosmic QCD transition. We specify the required values of the lepton flavor asymmetries for which a first-order transition occurs for a number of different benchmark scenarios.
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Guastalla, G. et al, Algora, A., & Domingo-Pardo, C. (2013). Coulomb Excitation of Sn-104 and the Strength of the Sn-100 Shell Closure. Phys. Rev. Lett., 110(17), 172501–5pp.
Abstract: A measurement of the reduced transition probability for the excitation of the ground state to the first 2(+) state in Sn-104 has been performed using relativistic Coulomb excitation at GSI. Sn-104 is the lightest isotope in the Sn chain for which this quantity has been measured. The result is a key point in the discussion of the evolution of nuclear structure in the proximity of the doubly magic nucleus Sn-100. The value B(E2; 0(+) -> 2(+)) = 0.10(4) e(2)b(2) is significantly lower than earlier results for Sn-106 and heavier isotopes. The result is well reproduced by shell model predictions and therefore indicates a robust N = Z = 50 shell closure.
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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. (2020). CP Properties of Higgs Boson Interactions with Top Quarks in the (tt)over-barH and tH Processes Using H -> gamma gamma with the ATLAS Detector. Phys. Rev. Lett., 125(6), 061802–21pp.
Abstract: A study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and top quarks is presented. Higgs bosons are identified via the diphoton decay channel (H -> gamma gamma), and their production in association with a top quark pair ((tt) over barH) or single top quark (tH) is studied. The analysis uses 139 fb(-1) of proton-proton collision data recorded at a center-of-mass energy off root s= 13 TeV with the ATLAS detector at the Large Hadron Collider. Assuming a CP-even coupling, the (tt) over barH process is observed with a significance of 5.2 standard deviations. The measured cross section times H -> gamma gamma branching ratio is 1.64(-0.36)(+0.38)(stat)(-0.14)(+0.17) (sys) fb, and the measured rate for (tt) over barH is 1.43(-0.31)(+0.33) (stat)(-0.15)(+0.21) (sys) times the Standard Model expectation. The tH production process is not observed and an upper limit on its rate of 12 times the Standard Model expectation is set. A CP-mixing angle greater (less) than 43 (-43)degrees is excluded at 95% confidence level.
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Caputo, A., Liu, H. W., Mishra-Sharma, S., & Ruderman, J. T. (2020). Dark Photon Oscillations in Our Inhomogeneous Universe. Phys. Rev. Lett., 125(22), 221303–8pp.
Abstract: A dark photon kinetically mixing with the ordinary photon represents one of the simplest viable extensions to the standard model, and would induce oscillations with observable imprints on cosmology. Oscillations are resonantly enhanced if the dark photon mass equals the ordinary photon plasma mass, which tracks the free electron number density. Previous studies have assumed a homogeneous Universe; in this Letter, we introduce for the first time an analytic formalism for treating resonant oscillations in the presence of inhomogeneities of the photon plasma mass. We apply our formalism to determine constraints from cosmic microwave background photons oscillating into dark photons, and from heating of the primordial plasma due to dark photon dark matter converting into low-energy photons. Including the effect of inhomogeneities demonstrates that prior homogeneous constraints are not conservative, and simultaneously extends current experimental limits into a vast new parameter space.
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NEXT Collaboration(McDonald, A. D. et al), Alvarez, V., Benlloch-Rodriguez, J. M., Botas, A., Carcel, S., Carrion, J. V., et al. (2018). Demonstration of Single-Barium-Ion Sensitivity for Neutrinoless Double-Beta Decay Using Single-Molecule Fluorescence Imaging. Phys. Rev. Lett., 120(13), 132504–6pp.
Abstract: A new method to tag the barium daughter in the double-beta decay of Xe-136 is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba++) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (similar to 2 nm), and detected with a statistical significance of 12.9 sigma over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.
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