We present the results of searches for nucleon decay via n→ν[over ¯]π0 and p→ν[over ¯]π+ using data from a combined 172.8 kt·yr exposure of Super-Kamiokande-I,-II, and-III. We set lower limits on the partial lifetime for each of these modes: τn→ν[over ¯]π0>1.1×10(33) years and τp→ν[over ¯]π+>3.9×10(32) years at a 90% confidence level.
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http://dx.doi.org/10.1103/PhysRevLett.113.121802 | DOI Listing |
Phys Rev Lett
November 2024
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
The accuracy of V_{ud} determinations from superallowed β decays critically hinges on control over radiative corrections. Recently, substantial progress has been made on the single-nucleon, universal corrections, while nucleus-dependent effects, typically parametrized by a quantity δ_{NS}, are much less well constrained. Here, we lay out a program to evaluate this correction from effective field theory (EFT), highlighting the dominant terms as predicted by the EFT power counting.
View Article and Find Full Text PDFJ Phys Chem B
December 2024
Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, Moscow 119991, Russia.
The primary photoisomerization reactions of the all- to 13- and 11- to all- retinal protonated Schiff base (RPSB) in microbial and animal rhodopsins, respectively, occur on a subpicosecond time scale with high quantum yields. At the same time, the isolated RPSB exhibits slower excited-state decay, in particular, in its all- form, and hence the interaction with the protein environment is capable of changing the time scale as well as the specificity of the reaction. Here, by using the high-level QM/MM calculations, we provide a comparative study of the primary photoresponse of and RPSB isomers in both the initial forms and first photoproducts of microbial rhodopsin 2 (KR2) and bacteriorhodopsin (BR), and animal visual rhodopsin (Rho).
View Article and Find Full Text PDFBiomolecules
October 2024
Institute of Medical Physics, University of Szeged, 6720 Szeged, Hungary.
The pH dependence of the free energy level of the flash-induced primary charge pair PI was determined by a combination of the results from the indirect charge recombination of PQ and from the delayed fluorescence of the excited dimer (P*) in the reaction center of the photosynthetic bacterium , where the native ubiquinone at the primary quinone binding site Q was replaced by low-potential anthraquinone (AQ) derivatives. The following observations were made: (1) The free energy state of PI was pH independent below pH 10 (-370 ± 10 meV relative to that of the excited dimer P*) and showed a remarkable decrease (about 20 meV/pH unit) above pH 10. A part of the dielectric relaxation of the PI charge pair that is not insignificant (about 120 meV) should come from protonation-related changes.
View Article and Find Full Text PDFJ Phys Chem Lett
November 2024
College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China.
Long-lived triplet states are critical intermediates of thiobases for their applications in photodynamic therapy and as photoprobes for DNA/RNA-protein interactions, where thiobases are embedded in DNA/RNA and exist as thionucleosides. However, sugar moieties accelerate triplet decay rates, which is a common issue that must be resolved for thionucleosides. Here, we explore whether protonation of 2-thiocytosine (2tCyt) and 2-thiocytidine (2tCyd) under acidic pH can alter their triplet decays.
View Article and Find Full Text PDFEur Phys J C Part Fields
November 2024
Physics Department, TUM School of Natural Sciences, Technical University of Munich, James-Franck-Straße 1, 85748 Garching b. München, Germany.
Antinuclei in our Galaxy may stem either from annihilation or decay of dark matter, or from collisions of cosmic rays with the interstellar medium, which constitute the background of indirect dark matter searches. Understanding the formation mechanism of (anti)nuclei is crucial for setting limits on their production in space. Coalescence models, which describe the formation of light nuclei from final-state interaction of nucleons, have been widely employed in high-energy collisions.
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