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1. A small proton charge radius from an electron–proton scattering experiment

   https://doi.org/10.1038/s41586-019-1721-2  

   Xiong, W.; Gasparian, A.; Gao, H.; Dutta, D.; Khandaker, M.; Liyanage, N.; Pasyuk, E.; Peng, C.; Bai, X.; Ye, L.; et al (November 2019, Nature)
2. Proton Radius: A Puzzle or a Solution!?

   https://doi.org/10.1088/1742-6596/2391/1/012017  

   Jentschura, Ulrich D. (December 2022, Journal of Physics: Conference Series)

   Abstract The proton radius puzzle is known as the discrepancy of the proton radius, obtained from muonic hydrogen spectroscopy (obtained as being roughly equal to 0.84 fm), and the proton radius obtained from (ordinary) hydrogen spectroscopy where a number of measurements involving highly excited states have traditionally favored a value of about 0.88 fm. Recently, a number of measurements of hydrogen transitions by the Munich (Garching) groups (notably, several hyperfine-resolved sublevels of the 2 S –4 P ) and by the group at the University of Toronto (2 S –2 P 1/2 ) have led to transition frequency data consistent with the smaller proton radius of about 0.84 fm. A recent measurement of the 2 S –8 D transition by a group at Colorado State University leads to a proton radius of about 0.86 fm, in between the two aforementioned results. The current situation points to a possible, purely experimental, resolution of the proton radius puzzle. However, a closer look at the situation reveals that the situation may be somewhat less clear, raising the question of whether or not the proton radius puzzle has been conclusively solved, and opening up interesting experimental possiblities at TRIUMF/ARIEL. 

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3. Charge Regulation in a Rieske Proton Pump Pinpoints Zero, One, and Two Proton-Coupled Electron Transfer

   https://doi.org/10.1021/jacs.3c03006  

   Koone, Jordan_C; Simmang, Mikaela; Saenger, Devin_L; Hunsicker-Wang, Laura_M; Shaw, Bryan_F (July 2023, Journal of the American Chemical Society)
4. Scattering Studies with Low-Energy Kaon-Proton Femtoscopy in Proton-Proton Collisions at the LHC

   https://doi.org/10.1103/PhysRevLett.124.092301  

   Acharya, S.; Adamová, D.; Adhya, S. P.; Adler, A.; Adolfsson, J.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; et al (March 2020, Physical Review Letters)
5. Search for a right-handed W boson and a heavy neutrino in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

   https://doi.org/10.1007/JHEP04(2022)047  

   Tumasyan, A.; Adam, W.; Andrejkovic, J. W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Escalante Del Valle, A.; Frühwirth, R.; Jeitler, M.; et al (April 2022, Journal of High Energy Physics)

   A bstract A search is presented for a right-handed W boson (W R ) and a heavy neutrino (N), in a final state consisting of two same-flavor leptons (ee or μμ) and two quarks. The search is performed with the CMS experiment at the CERN LHC using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb − 1 . The search covers two regions of phase space, one where the decay products of the heavy neutrino are merged into a single large-area jet, and one where the decay products are well separated. The expected signal is characterized by an excess in the invariant mass distribution of the final-state objects. No significant excess over the standard model background expectations is observed. The observations are interpreted as upper limits on the product of W R production cross sections and branching fractions assuming that couplings are identical to those of the standard model W boson. For N masses m N equal to half the W R mass $$ {m}_{{\mathrm{W}}_{\mathrm{R}}} $$ m W R ( m N = 0 . 2 TeV), $$ {m}_{{\mathrm{W}}_{\mathrm{R}}} $$ m W R is excluded at 95% confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channels, respectively. This analysis provides the most stringent limits on the W R mass to date. 

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