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While mean-field approximations, such as the nuclear shell model, provide a good description of many bulk nuclear properties, they fail to capture the important effects of nucleon–nucleon correlations such as the short-distance and high-momentum components of the nuclear many-body wave function1. Here, we study these components using the effective pair-based generalized contact formalism2,3 and ab initio quantum Monte Carlo calculations of nuclei from deuteron to 40Ca (refs. 4–6). We observe a universal factorization of the many-body nuclear wave function at short distance into a strongly interacting pair and a weakly interacting residual system. The residual system distribution is consistent with that of an uncorrelated system, showing that short-distance correlation effects are predominantly embedded in two-body correlations. Spin- and isospin-dependent ‘nuclear contact terms’ are extracted in both coordinate and momentum space for different realistic nuclear potentials. The contact coefficient ratio between two different nuclei shows very little dependence on the nuclear interaction model. These findings thus allow extending the application of mean-field approximations to short-range correlated pair formation by showing that the relative abundance of short-range pairs in the nucleus is a long-range (that is, mean field) quantity that is insensitive to the short-distance nature of the nuclear force.Effects of nucleon–nucleon correlations are studied with the generalized contact formalism and ab initio quantum Monte Carlo calculations. For nuclei from deuteron to 40Ca, the many-body nuclear wave function is shown to factorize at short distances.

The atomic nucleus is made of protons and neutrons (nucleons), which are themselves composed of quarks and gluons. Understanding how the quark–gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification—known as the EMC effect—was first observed over 35 years ago, there is still no generally accepted explanation for its cause 1 – 3 . Recent observations suggest that the EMC effect is related to close-proximity short-range correlated (SRC) nucleon pairs in nuclei 4 , 5 . Here we report simultaneous, high-precision measurements of the EMC effect and SRC abundances. We show that EMC data can be explained by a universal modification of the structure of nucleons in neutron–proton SRC pairs and present a data-driven extraction of the corresponding universal modification function. This implies that in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have distorted quark structure. This universal modification function will be useful for determining the structure of the free neutron and thereby testing quantum chromodynamics symmetry-breaking mechanisms and may help to discriminate between nuclear physics effects and beyond-the-standard-model effects in neutrino experiments. Simultaneous high-precision measurements of the EMC effect and short-range correlated abundances for several nuclei reveal a universal modification of the structure of nucleons in short-range correlated neutron–proton pairs.

Neutrinos exist in one of three types or ‘flavours’—electron, muon and tau neutrinos—and oscillate from one flavour to another when propagating through space. This phenomena is one of the few that cannot be described using the standard model of particle physics (reviewed in ref.  1 ), and so its experimental study can provide new insight into the nature of our Universe (reviewed in ref.  2 ). Neutrinos oscillate as a function of their propagation distance ( L ) divided by their energy ( E ). Therefore, experiments extract oscillation parameters by measuring their energy distribution at different locations. As accelerator-based oscillation experiments cannot directly measure E , the interpretation of these experiments relies heavily on phenomenological models of neutrino–nucleus interactions to infer E . Here we exploit the similarity of electron–nucleus and neutrino–nucleus interactions, and use electron scattering data with known beam energies to test energy reconstruction methods and interaction models. We find that even in simple interactions where no pions are detected, only a small fraction of events reconstruct to the correct incident energy. More importantly, widely used interaction models reproduce the reconstructed energy distribution only qualitatively and the quality of the reproduction varies strongly with beam energy. This shows both the need and the pathway to improve current models to meet the requirements of next-generation, high-precision experiments such as Hyper-Kamiokande (Japan) 3 and DUNE (USA) 4 . Electron scattering measurements are shown to reproduce only qualitatively state-of-the-art lepton–nucleus energy reconstruction models, indicating that improvements to these particle-interaction models are required to ensure the accuracy of future high-precision neutrino oscillation experiments.

The development and operation of liquid-argon time-projection chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. Whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. The Pandora Software Development Kit provides functionality to aid the design and implementation of pattern-recognition algorithms. It promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. Many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. This paper describes details of the chain of over one hundred Pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the MicroBooNE detector. Metrics that assess the current pattern-recognition performance are presented for simulated MicroBooNE events, using a selection of final-state event topologies.

Primary challenges for current and future precision neutrino experiments using liquid argon time projection chambers (LArTPCs) include understanding detector effects and quantifying the associated systematic uncertainties. This paper presents a novel technique for assessing and propagating LArTPC detector-related systematic uncertainties. The technique makes modifications to simulation waveforms based on a parameterization of observed differences in ionization signals from the TPC between data and simulation, while remaining insensitive to the details of the detector model. The modifications are then used to quantify the systematic differences in low- and high-level reconstructed quantities. This approach could be applied to future LArTPC detectors, such as those used in SBN and DUNE.

Background:Up to a third of psoriatic arthritis (PsA) patients fail their first biological/targeted synthetic disease modifying drug (b/tsDMARD) and likelihood of non-response (NR) is greater with each subsequent b/tsDMARD switch. This has substantial cost implications and impacts quality of life. Many factors contribute to NR, e.g. obesity and co-morbidities, making this a difficult-to-treat PsA (D2TPsA) population. Establishing a refractory inflammatory drive underpinning this loss of or lack of response is essential to personalise further treatment strategies for this subgroup.Objectives:To describe the baseline clinical and ultrasound (US) features of patients with D2TPsA, to compare differences in between patients responding to their current b/tsDMARD [disease activity score psoriatic arthritis (DAPSA) low disease activity; DAPSA≤14] vs. moderate-to-high disease activity (DAPSA ≥15) and to explore possible biomarkers associated with b/tsDMARD NR.Methods:A cross-sectional analysis of PsA patients attending the Leeds Specialist Spondyloarthritis Tertiary Service in 2023 who were currently being treated with b/tsDMARDs and had been exposed to ≥2 b/tsDMARDs in total. Demographic, clinical, biochemical and patient outcome data were collected, and US examination performed on the same visit in patients with swollen joint count (SJC) ≥1 (≤3 joints scanned per patient) to objectively measure inflammation. b/tsDMARD NR was defined as DAPSA ≥15 despite adequate trial of drug treatment. Clinical characteristics between those with a DAPSA ≥15 versus DAPSA ≤14 (low disease activity/remission) were compared, and a sub-analysis was performed in those patients with and without joint swelling (DAPSA ≥15/SJC ≥1 vs. DAPSA ≥15/ SJC=0). ANOVA/Wilcoxon-Mann-Whitney-U/Chi-squared tests were used to test for statistical significance between individual variables, and clinically/statistically relevant variables were then included in a logistic regression. For datapoints with <10% missing values the mean was imputed, otherwise the variable was discarded. Analyses were performed in RStudio 2023.06.0 + 421.Results:A total of 594 patients taking b/tsDMARDs for PsA were identified, of which 30.0% (178/594) had received ≥2 b/tsDMARDs of any mode of action (MOA) and 97% (173/178) had received ≥2b/tsDMARD with different MOA. Seventy-four (74.7%; 133/178) were seen face-to-face in clinic, of whom 68.4% (91/133) had a DAPSA ≥15 and 33% (30/91) had at least one swollen joint (Figure 1). DAPSA ≥15 was associated with higher Leeds Enthesitis Index (LEI; 1.0 vs 0.2, p<0.001), Physician Likert disease activity score (PhLDA; 2.8 vs. 1.4, p<0.001), Health Assessment Questionnaire (HAQ; 1.8 vs. 0.6, p<0.001) and extent of impact on ADLs (p<0.001). LEI, PhLDA and HAQ remained significant in the regression. Characteristics that differed between DAPSA ≥15/SJC ≥1 vs. DAPSA≥15/SJC=0 were osteoarthritis (33.3% vs. 55.7%, p=0.044), symptom duration (5.8 vs. 8.1, p=0.066), inflammatory bowel disease (0% vs. 11.5%, p=0.053) and PhLDA (2.1 vs. 3.3, p<0.001). Twenty-seven patients with SJC ≥1 and DAPSA ≥15 underwent joint US, and power doppler (PD) was found in 48.1% (13/27) (Figure 2).Conclusion:In our cohort, LEI, HAQ and PhLDA were significantly higher in patients with DAPSA ≥15 in individual and multivariate logistic regression, and higher PhLDA was associated with joint swelling. However, objective inflammation (PD on US) was only found in ~50% of cases. Findings now require replication in a larger clinical cohort to confirm reproducibility and to explore the utility of clinical characteristics and US as predictors of NR in D2TPsA.REFERENCES:NIL.Figure 1.Flowchart of patients with difficult-to-treat PsA under the care of the Leeds Specialist Spondyloarthritis (SpA) ServiceFigure 2.Summary of clinical characteristics and logistic regression analysesAcknowledgements:The Leeds Spondyloarthritis Specialist Service including all administrative support staff, nursing staff, specialist nurses and junior doctors who help to care for the patients included in this audit. We would also like to thank all our patients for their cooperation without which this work would not be possible.Disclosure of Interests:Stephanie Harrison Received speaker fees for a non-promotional educational meetings sponsored by Janssen and Novartis., Or Hen: None declared, Andrea Di Matteo Janssen., Kamran Naraghi: None declared, Jake Weddell: None declared, Zara Vowden: None declared, Claire Vandevelde Janssen and UCB., Jane Freeston Novartis., Ferring., Andrew Barr: None declared, Dennis McGonagle AbbVie, BMS, Celgene, Eli-Lily, Janssen, Novartis, UCB and Pfizer., AbbVie, BMS, Celgene, Eli-Lily, Janssen, Novartis, UCB and Pfizer., Helena Marzo-Ortega AbbVie, Biogen, Eli-Lily, Janssen, Novartis, Pfizer and UCB., AbbVie, Biogen, Eli-Lily, Janssen, Novartis, Pfizer, Takeda and UCB., Eli-Lilly, Janssen, Moonlake, Novartis, and UCB., Janssen, Novartis, Pfizer and UCB

A bstract The MicroBooNE liquid argon time projection chamber located at Fermilab is a neutrino experiment dedicated to the study of short-baseline oscillations, the measurements of neutrino cross sections in liquid argon, and to the research and development of this novel detector technology. Accurate and precise measurements of calorimetry are essential to the event reconstruction and are achieved by leveraging the TPC to measure deposited energy per unit length along the particle trajectory, with mm resolution. We describe the non-uniform calorimetric reconstruction performance in the detector, showing dependence on the angle of the particle trajectory. Such non-uniform reconstruction directly affects the performance of the particle identification algorithms which infer particle type from calorimetric measurements. This work presents a new particle identification method which accounts for and effectively addresses such non-uniformity. The newly developed method shows improved performance compared to previous algorithms, illustrated by a 93.7% proton selection efficiency and a 10% muon mis-identification rate, with a fairly loose selection of tracks performed on beam data. The performance is further demonstrated by identifying exclusive final states in ν μ CC interactions. While developed using MicroBooNE data and simulation, this method is easily applicable to future LArTPC experiments, such as SBND, ICARUS, and DUNE.

The origin of the modification of the quark structure of nucleons in the nuclear medium can be tested with tagged recoil nucleon measurements from deep inelastic scattering off electrons on deuterium. The LAD experiment at the Thomas Jefferson National Laboratory (JLab) will measure the modification of the neutron structure function for high-momentum, highly-virtual neutrons by measuring the spectator recoil protons in coincidence with the scattered electron. An update on the experimental setup and projected results is presented. The experiment will collect data in Fall 2024.

A significant challenge in measurements of neutrino oscillations is reconstructing the incoming neutrino energies. While modern fully-active tracking calorimeters such as liquid argon time projection chambers in principle allow the measurement of all final state particles above some detection threshold, undetected neutrons remain a considerable source of missing energy with little to no data constraining their production rates and kinematics. We present the first demonstration of tagging neutrino-induced neutrons in liquid argon time projection chambers using secondary protons emitted from neutron-argon interactions in the MicroBooNE detector. We describe the method developed to identify neutrino-induced neutrons and demonstrate its performance using neutrons produced in muon-neutrino charged current interactions. The method is validated using a small subset of MicroBooNE’s total dataset. The selection yields a sample with 60 % of selected tracks corresponding to neutron-induced secondary protons. At this purity, the integrated efficiency is 8.4% for neutrons that produce a detectable proton.

Cosmic ray (CR) interactions can be a challenging source of background for neutrino oscillation and cross-section measurements in surface detectors. We present methods for CR rejection in measurements of charged-current quasielastic-like (CCQE-like) neutrino interactions, with a muon and a proton in the final state, measured using liquid argon time projection chambers (LArTPCs). Using a sample of cosmic data collected with the MicroBooNE detector, mixed with simulated neutrino scattering events, a set of event selection criteria is developed that produces an event sample with minimal contribution from CR background. Depending on the selection criteria used a purity between 50 and 80% can be achieved with a signal selection efficiency between 50 and 25%, with higher purity coming at the expense of lower efficiency. While using a specific dataset and selection criteria values optimized for the MicroBooNE detector, the concepts presented here are generic and can be adapted for various studies of exclusive \\[\\nu _{\\mu }\\] CCQE interactions in LArTPCs.