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1. Physical and biogeochemical drivers of solute mobilization and flux through the critical zone after wildfire

   https://doi.org/10.3389/frwa.2023.1148298  

   Sánchez, Rodrigo Andrés; Meixner, Thomas; Roy, Tirthankar; Ferré, Paul Ty; Whitaker, Martha; Chorover, Jon (May 2023, Frontiers in Water)

   A nine-year time series of nutrient cation and anion concentration and efflux from three forested catchments in the Jemez River Basin Critical Zone Observatory (JRB-CZO) in northern New Mexico was used to quantify the pulse of chemical denudation resulting from varying levels stand-replacing wildfire intensity in May-June of 2013. The 3 years of pre-fire and 6 years of postfire data were also probed to shed light on the mechanisms underlying the pulsed release and the subsequent recovery. The initial large solute pulse released to the streams—K⁺, Ca²⁺, Mg²⁺, SO ${}_4^{2-}$, Cl⁻, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN)—was caused by leaching of hillslope ash deposits during the first monsoon storms post-fire. Debris flow following the wildfire likely redistributed much of the ash-containing sediments along streams and valley bottoms. Sustained elevated solute concentrations observed in the surface waters throughout the post-fire period relative to pre-fire baselines is consistent with these soluble materials being periodically flushed from the soils during wet seasons, i.e., snowmelt and summer monsoons. As microbial mediated reactions and biotic uptake—due to plant regrowth—recover after fire, nutrient ion export (e.g., NO ${}_3^{-}$, Cl⁻and SO ${}_4^{2-}$) steadily decreased toward the end of the post fire period, but remained above pre-fire levels, particularly for NO ${}_3^{-}$and SO ${}_4^{2-}$. Surface water concentrations of polyvalent cations (e.g., Al and Fe) decreased significantly after the fire. Our observations suggest that changes in organic matter composition after fire (e.g., increased humification index—HIX) and the presence of pyrogenic carbon may not favor organo-metal complexation and transport. Finally, differences in burn severity among the three watersheds presented in this study, provide insights of the relative impact of solute exports and resilience. The catchments that experienced high burn severity exhibited greater solute fluxes than the less severely burn. Moreover, despite these differences, toward the end of the post-fire period these surface waters presented low and similar solute effluxes, indicating system recovery. Nonetheless, magnitudes and rebounds were solute and process specific. The results of this study highlight the importance of surface and near surface physical and biogeochemical processes on the long-lasting geochemical denudation of forested catchments following wildfires of varying intensities. 

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2. Neutron skins: A perspective from dispersive optical models

   https://doi.org/10.3389/fphy.2024.1487314  

   Atkinson, M C; Dickhoff, W H (October 2024, Frontiers in Physics)

   Moreno, O (Ed.)

   An overview of neutron skin predictions obtained using an empirical nonlocal dispersive optical model (DOM) is presented. The DOM links both scattering and bound-state experimental data through a subtracted dispersion relation which allows for fully consistent, data-informed predictions for nuclei where such data exist. Large skins were predicted for both⁴⁸Ca ( $R_{\text{skin}}^{48}=0.25\pm 0.023$fm in 2017) and²⁰⁸Pb ( $R_{\text{skin}}^{208}=0.25\pm 0.05$fm in 2020). Whereas the DOM prediction in²⁰⁸Pb is within 1 $\sigma$of the subsequent PREX-2 measurement, the DOM prediction in⁴⁸Ca is over 2 $\sigma$larger than the thin neutron skin resulting from CREX. From the moment it was revealed, the thin skin in⁴⁸Ca has puzzled the nuclear-physics community as no adequate theories simultaneously predict both a large skin in²⁰⁸Pb and a small skin in⁴⁸Ca. The DOM is unique in its ability to treat both structure and reaction data on the same footing, providing a unique perspective on this $R_{\text{skin}}$puzzle. It appears vital that more neutron data be measured in both the scattering and bound-state domain for⁴⁸Ca to clarify the situation. 

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3. Observation of $\text{γ}\text{γ}\to \text{τ}\text{τ}$ in proton–proton collisions and limits on the anomalous electromagnetic moments of the τ lepton

   https://doi.org/10.1088/1361-6633/ad6fcb  

   CMS_Collaboration, The (September 2024, Reports on Progress in Physics)

   Abstract The production of a pair of τ leptons via photon–photon fusion, $\text{γ}\text{γ}\to \text{τ}\text{τ}$, is observed for the first time in proton–proton collisions, with a significance of 5.3 standard deviations. This observation is based on a data set recorded with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb⁻¹. Events with a pair of τ leptons produced via photon–photon fusion are selected by requiring them to be back-to-back in the azimuthal direction and to have a minimum number of charged hadrons associated with their production vertex. The τ leptons are reconstructed in their leptonic and hadronic decay modes. The measured fiducial cross section of $\text{γ}\text{γ}\to \text{τ}\text{τ}$is ${\sigma }_{\text{obs}}^{\text{fid}}={12.4}_{-3.1}^{+3.8}\text{fb}$. Constraints are set on the contributions to the anomalous magnetic moment ( $a_{\text{τ}}$) and electric dipole moments ( $d_{\text{τ}}$) of the τ lepton originating from potential effects of new physics on the $\text{γ}\text{τ}\text{τ}$vertex: $a_{\text{τ}}={0.0009}_{-0.0031}^{+0.0032}$and $|d_{\text{τ}}|<2.9\times {10}^{-17}e\text{cm}$(95% confidence level), consistent with the standard model. 

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4. Observation of the $${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} $$ decay

   https://doi.org/10.1140/epjc/s10052-024-13114-9  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Valle, A_Escalante Del; Hussain, P S; et al (October 2024, The European Physical Journal C)

   Abstract Using proton–proton collision data corresponding to an integrated luminosity of$$140\hbox { fb}^{-1}$$ $140{\text{fb}}^{-1}$collected by the CMS experiment at$$\sqrt{s}= 13\,\text {Te}\hspace{-.08em}\text {V} $$ $\sqrt{s}=13\text{Te}\text{V}$, the$${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} $$ ${\Lambda }_{\text{b}}^0\to \text{J}/\psi {\Xi }^{-}{\text{K}}^{+}$decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the$${{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{{\uppsi }} ({2\textrm{S}})} {{\Lambda }} $$ ${\Lambda }_{\text{b}}^0\to \psi \left(2\text{S}\right)\Lambda$decay, is measured to be$$\mathcal {B}({{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{\text {J}/\uppsi }} {{{\Xi }} ^{{-}}} {{\text {K}} ^{{+}}} )/\mathcal {B}({{{\Lambda }} _{\text {b}}^{{0}}} \rightarrow {{{\uppsi }} ({2\textrm{S}})} {{\Lambda }} ) = [3.38\pm 1.02\pm 0.61\pm 0.03]\%$$ $B({\Lambda }_{\text{b}}^0\to \text{J}/\psi {\Xi }^{-}{\text{K}}^{+})/B({\Lambda }_{\text{b}}^0\to \psi \left(2\text{S}\right)\Lambda )=[3.38\pm 1.02\pm 0.61\pm 0.03]\%$, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in$$\mathcal {B}({{{\uppsi }} ({2\textrm{S}})} \rightarrow {{\text {J}/\uppsi }} {{{\uppi }} ^{{+}}} {{{\uppi }} ^{{-}}} )$$ $B(\psi \left(2\text{S}\right)\to \text{J}/\psi {\pi }^{+}{\pi }^{-})$and$$\mathcal {B}({{{\Xi }} ^{{-}}} \rightarrow {{\Lambda }} {{{\uppi }} ^{{-}}} )$$ $B({\Xi }^{-}\to \Lambda {\pi }^{-})$. 

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5. Observation of a pseudoscalar excess at the top quark pair production threshold

   https://doi.org/10.1088/1361-6633/adf7d3  

   Collaboration, The_CMS (August 2025, Reports on Progress in Physics)

   Abstract A search for resonances in top quark pair ( $\mathrm{t}\bar{\mathrm{t}}$) production in final states with two charged leptons and multiple jets is presented, based on proton–proton collision data collected by the CMS experiment at the CERN LHC at $\sqrt{s}=13\text{TeV}$, corresponding to 138 fb⁻¹. The analysis explores the invariant mass of the $\mathrm{t}\bar{\mathrm{t}}$system and two angular observables that provide direct access to the correlation of top quark and antiquark spins. A significant excess of events is observed near the kinematic $\mathrm{t}\bar{\mathrm{t}}$threshold compared to the non-resonant production predicted by fixed-order perturbative quantum chromodynamics (pQCD). The observed enhancement is consistent with the production of a color-singlet pseudoscalar ( ${}^1{\text{S}}_0^{\left[1\right]}$) quasi-bound toponium state, as predicted by non-relativistic quantum chromodynamics. Using a simplified model for ${}^1{\text{S}}_0^{\left[1\right]}$toponium, the cross section of the excess above the pQCD prediction is measured to be $8.8{}_{-1.4}^{+1.2}\text{pb}$. 

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