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In marine ecosystems, increased global-scale transportation creates opportunities for rapid introduction of invasive parasitic species that, in some cases, result in dramatic shifts within the native communities. A lack of detailed knowledge regarding the ecology of invasive marine parasites hinders our ability to develop effective conservation strategies and avoid unforeseen ecological consequences. We examined co-infestation patterns of a highly pathogenic, introduced parasitic isopod (Orthione griffenis) and a native symbiotic clam (Neaeromya rugifera) on the North American native blue mud shrimp Upogebia pugettensis. Our comparisons included infestations of O. griffenis and N. rugifera among 447 U. pugettensis hosts over 3 study years and were designed to statistically assess whether the 2 symbionts exhibited significant associations with one another. Our results indicate that infestations by the 2 symbiont species are positively correlated, such that the presence of one symbiont is a strong, positive predictor for the presence of the other. For both symbionts, host size is an important factor that drives the observed correlation. Host sex is also influential for O. griffenis. Interestingly, even after accounting for these host attributes, the infestations by the 2 symbionts continue to correlate positively, particularly among older (second-year and beyond) symbionts, highlighting the likely influence of additional host and environmental factors in driving the symbiont correlation post-settlement. We consider potential mechanisms, including differential energetic reserves and longevities between infested and co-infested hosts, in detail. These results offer insights into the ecological drivers of symbiont co-infestation, which have important implications for understanding host-parasite interactions and future conservation measures. 

Continental arcs in Cordilleran orogenic systems display episodic changes in magma production rate, alternating between flare ups (70–90 km3 km􀀀 1 Myr􀀀 1) and lulls (< 20 km3 km􀀀 1 Myr􀀀 1) on timescales of tens of millions of years. Arc segments or individual magmatic suites may have even higher rates, up several 100 s of km3 km􀀀 1 Myr􀀀 1, during flare ups. These rates are largely determined by estimating volumes of arc crust, but do not reflect melt production from the mantle. The bulk of mantle-derived magmas are recycled back into the mantle by delamination of arc roots after differentiation in the deep crust. Mantle-derived melt production rates for continental arcs are estimated to be 140–215 km3 km􀀀 1 Myr􀀀 1 during flare ups and ≤ 15 km3 km􀀀 1 Myr􀀀 1 during lulls. Melt production rates averaged over multiple magmatic cycles are consistent with independent estimates for partial melting of the mantle wedge in subduction zones, however, the rates during flare ups and lulls are both anomalously high and anomalously low, respectively. The difference in mantle-derived melt production between flare ups and lulls is larger than predicted by petrologic and numerical models that explore the range of globally observed subduction parameters (e.g., convergence rate, height of the mantle wedge). This suggests that other processes are required to increase magmatism during flare ups and suppress magmatism during lulls. There are many viable explanations, but one possibility is that crystallized melts from the asthenospheric mantle wedge are temporarily stored in the deep lithosphere during lulls and then remobilized during flare ups. Basaltic melts may stall in the mantle lithosphere in inactive parts of the arc system, like the back-arc, refertilizing the mantle lithosphere and suppressing melt delivery to the lower crust. Subsequent landward arc migration (i.e., toward the interior of the continent) may encounter such refertilized mantle lithosphere magma source regions, contributing to magmatic activity during a flare up. A review of continental arcs globally suggests that flare ups commonly coincide with landward arc migration and that this migration may start tens of millions of years before the flare up occurs. The region of magmatic activity, or arc width, can also expand significantly during a flare up. Arc migration or expansion into different mantle source regions and across lithospheric and crustal boundaries can cause temporal shifts in the radiogenic isotopic composition of magmatism. In the absence of arc migration, temporal shifts are more muted. Isotopic studies of mantle xenoliths and exposures of deep arc crust suggest that that primary, mantle-derived magmas generated during flare ups reflect substantial contributions from the subcontinental mantle lithosphere. Arc migration may be caused by a variety of mechanisms, including slab anchoring or slab folding in the mantle transition zone that could generate changes in slab dip. Episodic slab shallowing is associated with many tectonic processes in Cordilleran orogenic systems, like alternations between shortening and extension in the upper plate. Studies of arc migration may help to link irregular magmatic production in continental arcs with geodynamic models for orogenic cyclicity. 

A search for pair production of squarks or gluinos decaying via sleptons or weak bosons is reported. The search targets a final state with exactly two leptons with same-sign electric charge or at least three leptons without any charge requirement. The analysed data set corresponds to an integrated luminosity of 139 fb⁻¹of proton-proton collisions collected at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Multiple signal regions are defined, targeting several SUSY simplified models yielding the desired final states. A single control region is used to constrain the normalisation of theWZ+ jets background. No significant excess of events over the Standard Model expectation is observed. The results are interpreted in the context of several supersymmetric models featuring R-parity conservation or R-parity violation, yielding exclusion limits surpassing those from previous searches. In models considering gluino (squark) pair production, gluino (squark) masses up to 2.2 (1.7) TeV are excluded at 95% confidence level.

 

A search for supersymmetry targeting the direct production of winos and higgsinos is conducted in final states with either two leptons (eorμ) with the same electric charge, or three leptons. The analysis uses 139 fb⁻¹ofppcollision data at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV collected with the ATLAS detector during Run 2 of the Large Hadron Collider. No significant excess over the Standard Model expectation is observed. Simplified and complete models with and withoutR-parity conservation are considered. In topologies with intermediate states including eitherWhorWZpairs, wino masses up to 525 GeV and 250 GeV are excluded, respectively, for a bino of vanishing mass. Higgsino masses smaller than 440 GeV are excluded in a naturalR-parity-violating model with bilinear terms. Upper limits on the production cross section of generic events beyond the Standard Model as low as 40 ab are obtained in signal regions optimised for these models and also for anR-parity-violating scenario with baryon-number-violating higgsino decays into top quarks and jets. The analysis significantly improves sensitivity to supersymmetric models and other processes beyond the Standard Model that may contribute to the considered final states.

 

Search for a new pseudoscalar a-boson decaying to muons in events with additional top quark pairs. 

A search for dark matter produced in association with a Higgs boson in final states with two hadronically decayingτ-leptons and missing transverse momentum is presented. The analysis uses 139 fb⁻¹of proton-proton collision data at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. No evidence of physics beyond the Standard Model is found. The results are interpreted in terms of a 2HDM+amodel featuring two scalar Higgs doublets and a pseudoscalar singlet field. Exclusion limits on the parameters of the model in selected benchmark scenarios are derived at 95% confidence level. Model-independent limits are also set on the visible cross-section for processes beyond the Standard Model producing missing transverse momentum in association with a Higgs boson decaying intoτ-leptons.

 

A search for pair-produced vector-like quarks using events with exactly one lepton (eor$$\mu $$$\mu$), at least four jets including at least oneb-tagged jet, and large missing transverse momentum is presented. Data from proton–proton collisions at a centre-of-mass energy of$$\sqrt{s}=$$$\sqrt{s}=$13 $$\text {TeV}$$$\text{TeV}$, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb$$^{-1}$$${}^{-1}$, are analysed. Vector-like partnersTandBof the top and bottom quarks are considered, as is a vector-likeXwith charge$$+5/3$$$+5/3$, assuming their decay into aW,Z, or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section ofTandBquark pairs as a function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 $$\text {TeV}$$$\text{TeV}$assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 $$\text {TeV}$$$\text{TeV}$(1.46 $$\text {TeV}$$$\text{TeV}$) for exclusive$$T \rightarrow Zt$$$T\to Zt$($$B/X \rightarrow Wt$$$B/X\to Wt$) decays. In addition, lower limits on theTandBquark masses are derived for all possible branching ratios.

 

This paper describes a search for the single production of an up-type vector-like quark (T) decaying asT→HtorT→Zt. The search utilises a dataset ofppcollisions at$$ \sqrt{s} $$$\sqrt{s}$= 13 TeV collected with the ATLAS detector during the 2015–2018 data-taking period of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb⁻¹. Data are analysed in final states containing a single lepton with multiple jets andb-jets. The presence of boosted heavy resonances in the event is exploited to discriminate the signal from the Standard Model background. No significant excess above the Standard Model expectation is observed, and 95% CL upper limits are set on the production cross section ofTquarks in different decay channels. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (κ) of the vector-like quark. For singletTquarks,κvalues above 0.53 are excluded for all masses below 2.3 TeV. At a mass of 1.6 TeV,κvalues as low as 0.35 are excluded. ForTquarks in the doublet scenario, where the production cross section is much lower,κvalues above 0.72 are excluded for all masses below 1.7 TeV, and this exclusion is extended toκabove 0.55 for low masses around 1.0 TeV.