Rubin-LSST

Abstract:

The $\mathrm{SNO}+$ Collaboration reports the first evidence of ${}^8\mathrm{B}$ solar neutrinos interacting on ${}^{13}\mathrm{C}$ nuclei. The charged current interaction proceeds through ${}^{13}\mathrm{C}+{\nu }_e{\to }^{13}\mathrm{N}+e^{-}$ which is followed, with a 10 minute half life, by ${}^{13}\mathrm{N}{\to }^{13}\mathrm{C}+e^{+}+{\nu }_e$ . The detection strategy is based on the delayed coincidence between the electron and the positron. Evidence for the charged current signal is presented with a significance of $4.2\sigma$ . Using the natural abundance of ${}^{13}\mathrm{C}$ present in the scintillator, 5.7 metric tons of ${}^{13}\mathrm{C}$ over 231 days of data were used in this analysis. The ${5.6}_{-2.3}^{+3.0}$ observed events in the data set are consistent with the expectation of ${4.7}_{-1.3}^{+0.6}$ events. This result is the second real-time measurement of CC interactions of ${}^8\mathrm{B}$ neutrinos with nuclei and constitutes the lowest energy observation of neutrino interactions on ${}^{13}\mathrm{C}$ generally. This enables the first direct measurement of the CC ${\nu }_e$ reaction to the ground state of ${}^{13}\mathrm{N}$ , yielding an average cross section of $({16.1}_{-6.7}^{+8.5}(\mathrm{stat}\mathrm{.}{)}_{-2.7}^{+1.6}(\mathrm{syst}\mathrm{.}))\times {10}^{-43}{\mathrm{cm}}^2$ over the relevant ${}^8\mathrm{B}$ solar neutrino energies.

Abstract:

We measure the amplitude of matter fluctuations over a wide range of redshifts by combining CMB lensing observations from ACT DR6 and Planck PR4 with the overdensity of quasars from Quaia, a Gaia and unWISE quasar catalog. Our analysis includes the CMB lensing power spectrum from ACT DR6, the auto-correlation of two Quaia quasar samples centered at z ≃ 1.0 and z ≃ 2.1, and their cross-correlations with CMB lensing from both ACT DR6 and Planck PR4. By performing a series of contamination and systematic null tests, we find no evidence for contamination in the lensing maps, contrary to what was suggested in previous Quaia cross-correlation analyses using Planck PR4 CMB lensing data. From the joint analysis of the quasar auto- and cross-correlations with CMB lensing, and including BOSS BAO data to break the degeneracy between Ω m and σ 8, we obtain σ 8 = 0.802+0.045 -0.057, consistent with ΛCDM predictions from Planck primary CMB measurements. We also find consistent results using DESI BAO data. Combining the CMB lensing auto-spectrum with the cross-correlation measurement improves the constraint on σ 8 by 12% relative to the lensing auto-spectrum alone, yielding σ 8 = 0.804 ± 0.013. This dataset combination also enables a reconstruction of structure growth across redshifts. We infer a 12% constraint on the amplitude of matter fluctuations at z > 3, with a measurement at the median redshift of the signal of σ 8(z̃ = 5.1) = 0.146+0.021 -0.014, consistent with Planck at the 1.4σ level. These results provide one of the highest redshift constraints on the growth of structure to date.

Abstract:

Higgs boson production cross-sections via gluon–gluon fusion and vector-boson fusion in proton–proton collisions are measured in the H→WW∗→ℓνℓν$$H\rightarrow WW^*\rightarrow \ell \nu \ell \nu $$ decay channel. The Large Hadron Collider delivered proton–proton collisions at a centre-of-mass energy of 13TeV$$13\,\text {TeV}$$ between 2015 and 2018, which were recorded by the ATLAS detector, corresponding to an integrated luminosity of 140fb-1.$$140\,\text {fb}^{-1}.$$ The total cross-sections for Higgs boson production by gluon–gluon fusion and vector-boson fusion times the H→WW∗$$H\rightarrow WW^*$$ branching ratio are measured to be 12.4-1.2+1.3pb$$12.4^{+1.3}_{-1.2}\,\text {pb}$$ and 0.79-0.16+0.18pb,$$0.79^{+0.18}_{-0.16}\,\text {pb},$$ respectively, in agreement with the Standard Model predictions. Higgs boson production is further characterised through measurements of Simplified Template Cross-Sections in a total of fifteen kinematic fiducial regions. A new scheme of kinematic fiducial regions has been introduced to enhance the sensitivity to CP-violating effects in Higgs boson interactions. Both schemes are used to constrain CP-even and CP-odd dimension-six operators in the Standard Model effective field theory

Abstract:

ATLAS, a general-purpose experiment at the Large Hadron Collider (LHC), makes use of a large internationally-distributed computing infrastructure, including over 106$$10^6$$ TB of managed data on disk and tape and almost one million simultaneously running CPU cores. Upgrades for the High-Luminosity LHC (HL-LHC) will increase the required computing resources by a factor of 3–4 by the beginning of the 2030s, and by an order of magnitude before the conclusion of data taking at the beginning of the 2040s. These resources are spread over around 100 computing sites worldwide. Efforts are underway within the experiment to evaluate and mitigate various aspects of the environmental impact of the sites, with the additional long-term goal of making recommendations to the sites that will significantly reduce the total expected environmental impact in the HL-LHC era. These efforts take several forms: building awareness in the experiment community, adjusting aspects of the computing policy, and modifications of data center configurations, either in ways that take advantage of particular features of ATLAS workloads or in generic ways that reduce the environmental impact of the computing resources. This paper describes the ongoing investigations and approaches that have already provided useful and actionable outcomes.

Abstract:

Kilonovae are the scientifically rich—but observationally elusive—optical transient phenomena associated with compact binary mergers. Only a handful of events have been discovered to date, all through multiwavelength (gamma-ray) and multimessenger (gravitational-wave) signals. Given their scarcity, it is important to maximise the discovery possibility of new kilonova events. To this end, we present our follow-up observations of the gravitational-wave signal S250818k—a plausible binary neutron star merger at a distance of 237 ± 62 Mpc. Pan-STARRS tiled 286 and 318 deg2 (32% and 34% of the 90% sky localisation region) within 3 and 7 days of the GW signal, respectively. ATLAS covered 65% of the sky map within 3 days, but with lower sensitivity. These observations uncovered 47 new transients; however, none were deemed to be linked to S250818k. We undertook an expansive follow-up campaign of AT2025ulz, the purported counterpart to S250818k. The griz-band light curve, combined with our redshift measurement (z = 0.0849 ± 0.0003), all indicate that SN2025ulz is a type IIb supernova and thus not the counterpart to S250818k. We rule out the presence of an AT2017gfo-like kilonova within ≈27% of the distance posterior sampled by our Pan-STARRS pointings (≈9.1% across the total 90% 3D sky localisation). We demonstrate that early observations are optimal for probing the distance posterior of the 3D gravitational-wave sky map, and that SN2025ulz was a plausible kilonova candidate for ≲5 days, before ultimately being ruled out.