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1. Magnetic properties of a staggered $S=1$ chain with an alternating single-ion anisotropy direction

   https://doi.org/10.1103/PhysRevB.111.014421  

   Vaidya, S; Curley, S_P M; Manuel, P; Stewart, J Ross; Le, M Duc; Balz, C; Shiroka, T; Blundell, S J; Wheeler, K A; Calderon-Lin, I; et al (January 2025, Physical Review B)

   Materials composed of spin-1 antiferromagnetic (AFM) chains are known to adopt complex ground states that are sensitive to the single-ion-anisotropy (SIA) energy ( $D$), and intrachain ( $J_0$) and interchain ( $J_{1,2}^{\prime }$) exchange energy scales. While theoretical and experimental studies have extended this model to include various other energy scales, the effect of the lack of a common SIA axis is not well explored. Here we investigate the magnetic properties of $\mathrm{Ni}\left(\mathrm{pyrimidine}\right){\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\left({\mathrm{NO}}_3\right)}_2$, a chain compound where the tilting of Ni octahedra leads to a twofold alternation of the easy-axis directions along the chain. Muon-spin relaxation measurements indicate a transition to long-range order at $T_{\text{N}}=2.3\mathrm{K}$and the magnetic structure is initially determined to be antiferromagnetic and collinear using elastic neutron diffraction experiments. Inelastic neutron scattering measurements were used to find $J_0=5.107\left(7\right)\mathrm{K}, D=2.79\left(1\right)\mathrm{K},J_1^{\prime }=0.00\left(5\right)\mathrm{K}, J_2^{\prime }=0.18\left(3\right)\mathrm{K}$, and a rhombic anisotropy energy $E=0.19\left(9\right)\mathrm{K}$. Mean-field modeling reveals that the ground state structure hosts spin canting of $\varphi \approx 6.5^{\circ }$, which is not detectable above the noise floor of the elastic neutron diffraction data. Monte Carlo simulation of the powder-averaged magnetization, $M\left(H\right)$, is then used to confirm these Hamiltonian parameters, while single-crystal $M\left(H\right)$simulations provide insight into features observed in the data. Published by the American Physical Society2025 

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2. Strength measurements of the $E_{\mathrm{R}}^{\mathrm{lab}}=647$ and 1842 keV resonances in the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$ reaction and their relevance in novae nucleosynthesis

   https://doi.org/10.1103/PhysRevC.111.025804  

   Sidhu, R S; deBoer, R J; Görres, J; Wiescher, M; Koros, J; Manukyan, K; Matney, M; McDonaugh, J; Picciotto, V; Sanchez, A T; et al (February 2025, Physical Review C)

   Here we report on the direct measurement of the resonance strengths of the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$and 1842 keV resonances in the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$reaction. At novae temperatures, $0.2<T_9<0.7$, the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$reaction is governed by the low energy resonance at $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$, whereas the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$resonance serves as a normalization standard for nuclear reaction experiments within the astrophysically relevant energy range. For the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$resonance, we obtain a resonance strength $\omega \gamma =(2.51\pm 0.{09}_{\mathrm{stat}}\pm 0.{22}_{\mathrm{syst}})\mathrm{meV}$, with an uncertainty a factor of 2.5 smaller than the previous direct measurement value. For the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$resonance, we obtain a resonance strength $\omega \gamma =(0.148\pm 0.{006}_{\mathrm{stat}}\pm 0.{013}_{\mathrm{syst}})\mathrm{eV}$, which is consistent with previous studies but deviates by $2\sigma$from the most recent measurement. Our results suggest ${}^{40}\mathrm{Ca}$to be a strong waiting point in the nucleosynthesis path of oxygen-neon (ONe) novae. Published by the American Physical Society2025 

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3. Evidence for Environmental Effects in the z = 4.3 Protocluster Core SPT2349–56

   https://doi.org/10.3847/2041-8213/adc1c9  

   Hughes, Chayce; Hill, Ryley; Chapman, Scott C; Aravena, Manuel; Archipley, Melanie; Dike, Veronica J; Gonzalez, Anthony; Greve, Thomas R; Gururajan, Gayathri; Hayward, Chris; et al (April 2025, The Astrophysical Journal Letters)

   Abstract We present Atacama Large Millimeter/submillimeter Array observations of the [CI] 492 and 806 GHz fine-structure lines in 25 dusty star-forming galaxies (DSFGs) atz= 4.3 in the core of the SPT2349–56 protocluster. The protocluster galaxies exhibit a median $L_{\left[\text{C}\mathrm{I}\right](2-1)}^{\prime }/L_{\left[\text{C}\mathrm{I}\right](1-0)}^{\prime }$ratio of 0.94, with an interquartile range of 0.81–1.24. These ratios are markedly different to those observed in DSFGs in the field (across a comparable redshift and 850μm flux density range), where the median is 0.55, with an interquartile range of 0.50–0.76, and we show that this difference is driven by an excess of [Ci](2–1) in the protocluster galaxies for a given 850μm flux density. Assuming local thermal equilibrium, we estimate gas excitation temperatures of $T_{\mathrm{ex}}=59.1_{-6.8}^{+8.1}$K for our protocluster sample and $T_{\mathrm{ex}}=33.9_{-2.2}^{+2.4}$K for the field sample. Our main interpretation of this result is that the protocluster galaxies have had their cold gas driven to their cores via close-by interactions within the dense environment, leading to an overall increase in the average gas density and excitation temperature, as well as an elevated [Ci](2–1) luminosity-to-far-infrared-luminosity ratio. 

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4. Magneto-optical trap of titanium atoms

   https://doi.org/10.1103/PhysRevResearch.7.023025  

   Eustice, Scott; Schrott, Jackson; Stöltzel, Anke; Wolf, Julian; Novoa, Diego; Cassella, Kayleigh; Stamper-Kurn, Dan M (April 2025, Physical Review Research)

   We realize a magneto-optical trap (MOT) of titanium (Ti) atoms, performing laser cooling on the 498 nm transition between the long-lived $3{\mathrm{d}}^3\left({}^4\mathrm{F}\right)4\mathrm{s}{\mathrm{a}}^5{\mathrm{F}}_5$metastable state and the $3{\mathrm{d}}^3\left({}^4\mathrm{F}\right)4\mathrm{p}{\mathrm{y}}^5{\mathrm{G}}_6^{\mathrm{o}}$excited state. Without the addition of any repumping light, we observe MOTs of the three stable, $I=0$bosonic isotopes, ${}^{46}\mathrm{Ti}, {}^{48}\mathrm{Ti}$, and ${}^{50}\mathrm{Ti}$. Up to $8.30\left(26\right)\times {10}^5{}^{48}\mathrm{Ti}$atoms are trapped at a maximum density of $1.3\left(4\right)\times {10}^{11}{\mathrm{cm}}^{-3}$and at a temperature of $90\left(15\right)\mu \mathrm{K}$. By measuring the decay of the MOT, we constrain the leakage branching ratio of the cooling transition ( $\le 2.5\times {10}^{-6}$) and the two-body loss coefficient ( $\le 2\times {10}^{-10}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$). Our approach to laser cooling Ti can be applied to other transition metals, enabling a significant expansion of the elements that can be laser cooled. Published by the American Physical Society2025 

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5. Systematic study of flow vector fluctuations in $\sqrt{s_{NN}}=5.02$ TeV Pb-Pb collisions

   https://doi.org/10.1103/PhysRevC.109.065202  

   Acharya, S; Adamová, D; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; et al (June 2024, Physical Review C)

   Measurements of the $p_{\mathrm{T}}$-dependent flow vector fluctuations in Pb–Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$using azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, ] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the $p_{\mathrm{T}}$-dependent flow vector fluctuations at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$with two-particle correlations. Significant $p_{\mathrm{T}}$-dependent fluctuations of the ${\vec{V}}_2$flow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up to $\sim 15\%$being present in the 5% most central collisions. In parallel, no evidence of significant $p_{\mathrm{T}}$-dependent fluctuations of ${\vec{V}}_3$or ${\vec{V}}_4$is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than $5\sigma$significance in central collisions. These observations in $\text{Pb–Pb}$collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high $p_{\mathrm{T}}$, which might be biased by $p_{\mathrm{T}}$-dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system. ©2024 CERN, for the ALICE Collaboration2024CERN 

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