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1. Elucidating the nature of the proton radioactivity and branching ratio on the first proton emitter discovered 53mCo

   https://doi.org/10.1038/s41467-023-39389-2  

   Sarmiento, Luis G; Roger, Thomas; Giovinazzo, Jérôme; Brown, B Alex; Blank, Bertram; Rudolph, Dirk; Kankainen, Anu; Alvarez-Pol, Héctor; Raj, Alex Arokia; Ascher, Pauline; et al (December 2023, Nature Communications)

   Abstract The observation of a weak proton-emission branch in the decay of the 3174-keV^53mCo isomeric state marked the discovery of proton radioactivity in atomic nuclei in 1970. Here we show, based on the partial half-lives and the decay energies of the possible proton-emission branches, that the exceptionally high angular momentum barriers,$${{{{{{\mathcal{l}}}}}}}_{{{{{{\rm{p}}}}}}}=9$$ $l_p=9$ and$${{{{{{\mathcal{l}}}}}}}_{{{{{{\rm{p}}}}}}}=7$$ $l_p=7$ , play a key role in hindering the proton radioactivity from^53mCo, making them very challenging to observe and calculate. Indeed, experiments had to wait decades for significant advances in accelerator facilities and multi-faceted state-of-the-art decay stations to gain full access to all observables. Combining data taken with the TASISpec decay station at the Accelerator Laboratory of the University of Jyväskylä, Finland, and the ACTAR TPC device on LISE3 at GANIL, France, we measured their branching ratios as b_p1= 1.3(1)% and b_p2= 0.025(4)%. These results were compared to cutting-edge shell-model and barrier penetration calculations. This description reproduces the order of magnitude of the branching ratios and partial half-lives, despite their very small spectroscopic factors. 

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2. Strong Evidence for ${}^9\mathrm{N}$ and the Limits of Existence of Atomic Nuclei

   https://doi.org/10.1103/PhysRevLett.131.172501  

   Charity, R J; Wylie, J; Wang, S M; Webb, T B; Brown, K W; Cerizza, G; Chajecki, Z; Elson, J M; Estee, J; Hoff, D_E M; et al (October 2023, Physical Review Letters)

   The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on two of the most exotic proton-rich isotopes where at least one half of their constitute nucleons are unbound. While the ground state of 8C is a resonance, its first excited state lies in the diffuse borderland between nuclear states and fleeting scattering features. Evidence for 9N, with seven protons and two neutrons, is also presented. This extremely proton-rich system represents the first-known example of a ground-state five-proton emitter. The energies of these states are consistent with theoretical predictions of an open-quantum-system approach. 

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3. Assessment of electron–proton correlation functionals for vibrational spectra of shared-proton systems by constrained nuclear-electronic orbital density functional theory

   https://doi.org/10.1063/5.0243086  

   Yang, Yuzhuo; Zhang, Yuzhe; Yang, Yang; Xu, Xi (December 2024, The Journal of Chemical Physics)

   Proton transfer plays a crucial role in various chemical and biological processes. A major theoretical challenge in simulating proton transfer arises from the quantum nature of the proton. The constrained nuclear-electronic orbital (CNEO) framework was recently developed to efficiently and accurately account for nuclear quantum effects, particularly quantum nuclear delocalization effects, in quantum chemistry calculations and molecular dynamics simulations. In this paper, we systematically investigate challenging proton transfer modes in a series of shared-proton systems using CNEO density functional theory (CNEO-DFT), focusing on evaluating existing electron–proton correlation functionals. Our results show that CNEO-DFT accurately describes proton transfer vibrational modes and significantly outperforms conventional DFT. The inclusion of the epc17-2 electron–proton correlation functional in CNEO-DFT produces similar performance to that without electron–proton correlations, while the epc17-1 functional yields less accurate results, comparable with conventional DFT. These findings hold true for both asymmetrical and symmetrical shared-proton systems. Therefore, until a more accurate electron–proton correlation functional is developed, we currently recommend performing vibrational spectrum calculations using CNEO-DFT without electron–proton correlation functionals. 

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4. Triple excitations in nuclear–electronic orbital coupled cluster theory for multiple quantum protons

   https://doi.org/10.1063/5.0303185  

   Goudy, Rowan J; Pavošević, Fabijan; Hammes-Schiffer, Sharon (December 2025, The Journal of Chemical Physics)

   Within the nuclear–electronic orbital (NEO) framework, specified nuclei, typically protons, are treated quantum mechanically on the same level as the electrons. This framework allows for nuclear quantum effects, such as anharmonic zero-point energy, to be included in quantum chemical calculations in a computationally efficient manner. NEO coupled cluster (NEO-CC) methods provide a promising strategy for producing accurate ground-state properties of moderately sized molecular systems. Herein, the inclusion of triple excitations in NEO-CC methods is explored for systems with multiple quantum protons. Full and perturbative treatments of electron–electron–proton and electron–proton–proton triple excitations are investigated. The perturbative treatment agrees quantitatively with the full treatment for proton affinity calculations and is much more computationally efficient, especially for systems with multiple quantum protons. The NEO-CCSD(T) method, which includes single, double, and perturbative electron–electron–proton, electron–proton–proton, and electron–electron–electron triple excitations, reproduces experimentally measured proton affinities within experimental uncertainty using a complete basis set extrapolation. Moreover, application of the NEO-CCSD(T) method to protonated water tetramers, with all nine protons treated quantum mechanically, incorporates the essential anharmonic zero-point energy with only a single-point energy calculation. NEO-CC methods offer an accurate and computationally practical approach for inclusion of nuclear quantum effects in molecular systems and may serve as a benchmark for lower-level NEO methods. 

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5. Measurements of inclusive and differential cross sections for the Higgs boson production and decay to four-leptons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP08(2023)040  

   Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Hussain, P. S.; et al (August 2023, Journal of High Energy Physics)

   A bstract Measurements of the inclusive and differential fiducial cross sections for the Higgs boson production in the H → ZZ → 4 ℓ ( ℓ = e , μ ) decay channel are presented. The results are obtained from the analysis of proton-proton collision data recorded by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb − 1 . The measured inclusive fiducial cross section is 2 . 73 ± 0 . 26 fb, in agreement with the standard model expectation of 2 . 86 ± 0 . 1 fb. Differential cross sections are measured as a function of several kinematic observables sensitive to the Higgs boson production and decay to four leptons. A set of double-differential measurements is also performed, yielding a comprehensive characterization of the four leptons final state. Constraints on the Higgs boson trilinear coupling and on the bottom and charm quark coupling modifiers are derived from its transverse momentum distribution. All results are consistent with theoretical predictions from the standard model. 

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