Management of newborns and healthcare workers exposed to isoniazid-resistant congenital tuberculosis in the neonatal intensive care unit

BACKGROUND

Management of newborns and healthcare workers (HCWs) exposed to congenital tuberculosis (TB) in the neonatal intensive care unit (NICU) has been reported rarely.

AIM

To outline a contact investigation process for individuals exposed to congenital TB in the NICU and investigate nosocomial transmission. Additionally, to assess the efficacy and safety of window prophylaxis in exposed newborns.

METHODS

A baby, born at a gestational age of 28 + 1 weeks, was diagnosed with isoniazid-resistant congenital TB on the 39th day of admission to the level IV NICU. Newborns and HCWs exposed cumulatively for ≥8 h underwent contact investigation and follow-up for a year.

FINDINGS

Eighty-two newborns underwent contact investigation. All newborns displayed normal chest X-rays, and 42 hospitalized newborns tested negative for acid-fast bacilli stain and Xpert® MTB/RIF assay in their endotracheal sputum or gastric juices. Eighty received window prophylaxis: six of 75 on rifampin experienced mild adverse events, and none of the five on levofloxacin. After 12 weeks, five (6.1%) had a positive tuberculin skin test, all of whom had already received the Bacillus Calmette-Guérin vaccine and tested negative on TB interferon-gamma releasing assay. Of 119 exposed HCWs, three (2.5%) were diagnosed with latent TB infection and completed a four-month rifampin therapy. There was no active TB disease among exposed newborns and HCWs during a one-year follow-up.

CONCLUSION

Timely diagnosis of congenital TB is crucial for minimizing transmission among exposed neonates and HCWs in the NICU setting. In cases of isoniazid-resistant index patients, even premature newborns may consider the use of rifampin or levofloxacin for window prophylaxis.

Development of machine learning models for the surveillance of colon surgical site infections

BACKGROUND

Conventional surgical site infection (SSI) surveillance is labour-intensive. We aimed to develop machine learning (ML) models for the surveillance of SSIs for colon surgery and to assess whether the ML could improve surveillance process efficiency.

METHODS

This study included cases who underwent colon surgery at a tertiary center between 2013 and 2014. Logistic regression and four ML algorithms including random forest (RF), gradient boosting (GB), and neural networks (NNs) with or without recursive feature elimination (RFE) were first trained on the entire cohort, and then re-trained on cases selected based on a previous rule-based algorithm. We assessed model performance based on the area under the curve (AUC), sensitivity, and positive predictive value (PPV). The estimated proportion of reduction in workload for chart review based on the ML models was evaluated and compared with the conventional method.

RESULTS

At a sensitivity of 95%, the NN with RFE using 29 variables had the best performance with an AUC of 0.963 and PPV of 21.1%. When combining both the rule-based algorithm and ML algorithms, the NN with RFE using 19 variables had a higher PPV (28.9%) than with the ML algorithm alone, which could decrease the number of cases requiring chart review by 83.9% compared with the conventional method.

CONCLUSION

We demonstrated that ML can improve the efficiency of SSI surveillance for colon surgery by decreasing the burden of chart review while providing high sensitivity. In particular, the hybrid approach of ML with a rule-based algorithm showed the best performance in terms of PPV.

"Primer shot" fractionation with an early treatment break is theoretically superior to consecutive weekday fractionation schemes for early-stage non-small cell lung cancer

PURPOSE

Radiotherapy is traditionally given in equally spaced weekday fractions. We hypothesize that heterogeneous interfraction intervals can increase radiosensitivity via reoxygenation. Through modeling, we investigate whether this minimizes local failures and toxicity for early-stage non-small cell lung cancer (NSCLC).

METHODS

Previously, a tumor dose-response model based on resource competition and cell-cycle-dependent radiosensitivity accurately predicted local failure rates for early-stage NSCLC cohorts. Here, the model mathematically determined non-uniform inter-fraction intervals minimizing local failures at similar normal tissue toxicity risk, i.e., iso-BED3 (iso-NTCP) for fractionation schemes 18Gyx3, 12Gyx4, 10Gyx5, 7.5Gyx8, 5Gyx12, 4Gyx15. Next, we used these optimized schedules to reduce toxicity risk (BED3) while maintaining stable local failures (TCP).

RESULTS

Optimal schedules consistently favored a "primer shot" fraction followed by a 2-week break, allowing tumor reoxygenation. Increasing or decreasing the assumed baseline hypoxia extended or shortened this optimal break by up to one week. Fraction sizes of 7.5 Gy and up required a single primer shot, while smaller fractions needed one or two extra fractions for full reoxygenation. The optimized schedules, versus consecutive weekday fractionation, predicted absolute LF reductions of 4.6%-7.4%, except for the already optimal LF rate seen for 18Gyx3. Primer shot schedules could also reduce BED3 at iso-TCP with the biggest improvements for the shortest schedules (94.6Gy reduction for 18Gyx3).

CONCLUSION

A validated simulation model clearly supports non-standard "primer shot" fractionation, reducing the impact of hypoxia-induced radioresistance. A limitation of this study is that primer-shot fractionation is outside prior clinical experience and therefore will require clinical studies for definitive testing.

Defective N-glycosylation in tumor-infiltrating CD8+ T cells impairs IFN-γ-mediated effector function

T cell-mediated antitumor immunity is modulated, in part, by N-glycosylation. However, the interplay between N-glycosylation and the loss of effector function in exhausted T cells has not yet been fully investigated. Here, we delineated the impact of N-glycosylation on the exhaustion of tumor-infiltrating lymphocytes in a murine colon adenocarcinoma model, focusing on the IFN-γ-mediated immune response. We found that exhausted CD8+ T cells downregulated the oligosaccharyltransferase complex, which is indispensable for N-glycan transfer. Concordant N-glycosylation deficiency in tumor-infiltrating lymphocytes leads to loss of antitumor immunity. Complementing the oligosaccharyltransferase complex restored IFN-γ production and alleviated CD8+ T cell exhaustion, resulting in reduced tumor growth. Thus, aberrant glycosylation induced in the tumor microenvironment incapacitates effector CD8+ T cells. Our findings provide insights into CD8+ T cell exhaustion by incorporating N-glycosylation to understand the characteristic loss of IFN-γ, opening new opportunities to amend the glycosylation status in cancer immunotherapies.

BAP1 shapes the bone marrow niche for lymphopoiesis by fine-tuning epigenetic profiles in endosteal mesenchymal stromal cells

Hematopoiesis occurs within a unique bone marrow (BM) microenvironment, which consists of various niche cells, cytokines, growth factors, and extracellular matrix components. These multiple components directly or indirectly regulate the maintenance and differentiation of hematopoietic stem cells (HSCs). Here we report that BAP1 in BM mesenchymal stromal cells (MSCs) is critical for the maintenance of HSCs and B lymphopoiesis. Mice lacking BAP1 in MSCs show aberrant differentiation of hematopoietic stem and progenitor cells, impaired B lymphoid differentiation, and expansion of myeloid lineages. Mechanistically, BAP1 loss in distinct endosteal MSCs, expressing PRX1 but not LEPR, leads to aberrant expression of genes affiliated with BM niche functions. BAP1 deficiency leads to a reduced expression of pro-hematopoietic factors such as Scf caused by increased H2AK119-ub1 and H3K27-me3 levels on the promoter region of these genes. On the other hand, the expression of myelopoiesis stimulating factors including Csf3 was increased by enriched H3K4-me3 and H3K27-ac levels on their promoter, causing myeloid skewing. Notably, loss of BAP1 substantially blocks B lymphopoiesis and skews the differentiation of hematopoietic precursors toward myeloid lineages in vitro, which is reversed by G-CSF neutralization. Thus, our study uncovers a key role for BAP1 expressed in endosteal MSCs in controlling normal hematopoiesis in mice by modulating expression of various niche factors governing lymphopoiesis and myelopoiesis via histone modifications.

Late ventricular potential for risk prediction of sudden cardiac death risk: a valuable tool or an unnecessary step?

Background/Introduction

Signal-averaged electrocardiography (SA-ECG) is a high-resolution electrocardiography that can detect late ventricular potential, which known to be a noninvasive tool for risk stratification of sudden cardiac death (SCD) by predicting reentrant ventricular tachyarrhythmia. There is a paucity of data with SA-ECG on SCD survivors without structural heart disease, whereas majority of previous studies had been focused on post myocardial infarction survivors.

Purpose

This study assessed the clinical utility of SA-ECG as a risk stratification modality for lethal arrhythmic event in patients at risk of SCD without definite structural heart disease.

Methods

Total 629 patients who experienced or had potential risk of SCD were studied with SA-ECG. Among them, 48 patients who were found to have significant structural heart disease were excluded, except arrhythmogenic right ventricular cardiomyopathy. Major arrhythmic event (MAE) was defined as composite of all-cause death, aborted SCD, and sustained VT during any time either before visit of clinic or during follow up period. Syncope and non-sustained VT was defined as non-major arrhythmic event. SA-ECG was defined positive when fulfilling three or more criterion: (1) unfiltered QRS duration ≥114ms, (2) filtered QRS duration ≥114ms, (3) duration of terminal QRS <40uV exceeding 40ms, and (4) root mean square voltage in the terminal 40ms of ≤20ms.

Results

Among total 581 patients, 145 patients with positive SA-ECG showed higher incidence of MAE compared to patients with negative SA-ECG (21.4% vs. 6.7%, OR 3.816 [95% CI 2.208–6.597], p<0.001, Table). As the number of positive SA-ECG criteria increases, incidence of MAE tended to increase sequentially, which was markedly noted from 2 positive to 3 positive criteria (10.7% to 20.8%, p<0.001, Figure). In particular, patient with inherited arrhythmia showed higher rate of positive late potential compared to those with non-inherited arrhythmia (51.0% vs. 19.3%, p<0.001).

Conclusion

This study showed that at least 3 out of 4 diagnostic criteria in SA-ECG can independently predict lethal arrhythmic events and the positive late potential was associated with lethal arrhythmic event that leads to SCD, suggesting risk prediction for SCD using SA-ECG in patients even without structural heart disease including inherited arrhythmias.

Funding Acknowledgement

Type of funding sources: None.

Clinical role of genetic testing for overlapping between Brugada syndrome and arrhythmogenic right ventricular cardiomyopathy

Background/Introduction

Brugada syndrome (BrS) and arrhythmogenic right ventricular cardiomyopathy (ARVC) are inherited arrhythmias that may predispose to sudden cardiac arrest. Although its pathogenetic mechanisms differ, overlapping features between BrS and ARVC have been demonstrated previously. However, it remains to be determined whether genetic testing for ARVC-related gene is needed in patients with BrS.

Purpose

This study is aimed to analyze genetic profiles of BrS patients using next generation sequencing (NGS) based multigene panel including ARVC related genes.

Methods

Patients who were confirmed as BrS or clinically suspected as BrS with type 2 or 3 Brugada pattern electrocardiography were studied. Genetic testing using NGS panels (Illumina Inc., San Diego, CA, USA) included 30 genetic variants associated with inherited arrhythmia and genetic cardiomyopathy.

Results

Among the total 119 patients from BrS registry, 63 patients were confirmed as BrS and 56 patients were clinically suspected as BrS without fulfilling diagnostic criteria. One-hundred-fourteen patients (95.8%) were male, and mean age of onset was 43.6 year-old. Genetic variants were identified in 25 of 42 patients who received genetic testing. Six out of 25 patients (24.0%) showed ARVC-related genotypes (2 PKP2, 1 DSG2, 1 TMEM43, 1 JUP, and 1 DSP) (Figure 1 and Table 1). None of the patients showed structural or electrocardiographic features that fulfill diagnostic criteria of ARVC. It is notable that ARVC-related genotypes were mostly frequently accounted for BrS patients, following SCN5A and SCN10A.

Conclusion

In the clinic setting, ARVC-related genetic variants were identified in significant proportion of BrS patients, supporting that genetic testing of ARVC-overlapping is needed. This study suggests that follow-up including imaging study should be considered in BrS patients with ARVC-related genotypes to monitor disease progression as ARVC.

Funding Acknowledgement

Type of funding sources: None.

Bap1/SMN axis in Dpp4+ skeletal muscle mesenchymal cells regulates the neuromuscular system

The survival of motor neuron (SMN) protein is a major component of the pre-mRNA splicing machinery and is required for RNA metabolism. Although SMN has been considered a fundamental gene for the central nervous system, due to its relationship with neuromuscular diseases, such as spinal muscular atrophy, recent studies have also revealed the requirement of SMN in non-neuronal cells in the peripheral regions. Here, we report that the fibro-adipogenic progenitor subpopulation expressing Dpp4 (Dpp4⁺ FAPs) is required for the neuromuscular system. Furthermore, we also reveal that BRCA1-associated protein-1 (Bap1) is crucial for the stabilization of SMN in FAPs by preventing its ubiquitination-dependent degradation. Inactivation of Bap1 in FAPs decreased SMN levels and accompanied degeneration of the neuromuscular junction, leading to loss of motor neurons and muscle atrophy. Overexpression of the ubiquitination-resistant SMN variant, SMN^K186R, in Bap1-null FAPs completely prevented neuromuscular degeneration. In addition, transplantation of Dpp4⁺ FAPs, but not Dpp4^– FAPs, completely rescued neuromuscular defects. Our data reveal the crucial role of Bap1-mediated SMN stabilization in Dpp4⁺ FAPs for the neuromuscular system and provide the possibility of cell-based therapeutics to treat neuromuscular diseases.

Extended DeepILST for Various Thermodynamic States and Applications in Coarse-Graining

Molecular dynamics (MD) simulations are widely used to obtain the microscopic properties of atomistic systems when the interatomic potential or the coarse-grained potential is known. In many practical situations, however, it is necessary to predict the interatomic or coarse-grained potential, which is a tremendous challenge. Many approaches have been developed to predict the potential parameters based on various techniques, including the relative entropy method, integral equation theory, etc., but these methods lack transferability and are limited to a specific range of thermodynamic states. Recently, data-driven and machine learning approaches have been developed to overcome such limitations. In this study, we expand the range of thermodynamic states used to train deep inverse liquid-state theory (DeepILST)¹, a deep learning framework for solving the inverse problem of liquid-state theory. We also assess the performance of DeepILST in coarse-graining various multiatom molecules and identify the molecular characteristics that affect the coarse-graining performance of DeepILST.

Fate and transport in environmental quality

Changes in pollutant concentrations in environmental media occur both from pollutant transport in water or air and from local processes, such as adsorption, degradation, precipitation, straining, and so on. The terms "fate and transport" and "transport and fate" reflect the coupling of moving with the carrier media and biogeochemical processes describing local transformations or interactions. The Journal of Environmental Quality (JEQ) was one of the first to publish papers on fate and transport (F&T). This paper is a minireview written to commemorate the 50th anniversary of JEQ and show how the research interests, methodology, and public attention have been reflected in fate and transport publications in JEQ during the last 40 years. We report the statistics showing how the representation of different pollutant groups in papers changed with time. Major focus areas have included the effect of solution composition on F&T and concurrent F&T, the role of organic matter, and the relative role of different F&T pathways. The role of temporal and spatial heterogeneity has been studied at different scales. The value of long-term F&T studies and developments in modeling as the F&T research approach was amply demonstrated. Fate and transport studies have been an essential part of conservation measure evaluation and comparison and ecological risk assessment. For 50 years, JEQ has delivered new insights, methods, and applications related to F&T science. The importance of its service to society is recognized, and we look forward to new generations of F&T researchers presenting their contributions in JEQ.

97 Function of species-specific OCT4 reporter system during porcine embryo development

The present study examined the activity and function of pig OCT4 (POU5F1) enhancer in porcine early embryo development. OCT4 is one of the master regulators for the pluripotency of early mammalian embryonic development and embryonic stem cells. It has two regulatory elements: distal enhancer (DE) and proximal enhancer (PE) in the upstream regulatory region. They are activated under different conditions such as naïve and primed. It is known that two enhancers are activated to produce OCT4 simultaneously or sequentially depending on the state of pluripotency. Many porcine OCT4 upstream region-based reporter systems have been reported because this is a necessary part of studying porcine-specific pluripotency. However, the porcine-specific OCT4 reporter system has never been transfected and functionally tested during porcine early embryo development. We performed functional tests of the previously established porcine-specific OCT4 reporter system in the early embryo development stage. Porcine embryos were micro-injected with the pOCT4-ΔPE-eGFP (DE-GFP) containing a distal enhancer and core promoter and pOCT4-ΔDE-DsRed2 (PE-RFP) containing a proximal enhancer and core promoter. They were cultured in PZM-3 at 39°C in a humidified atmosphere, 5% CO2, and 5% O2 for 168h. Fifty of the 100 embryos were injected with OCT4 reporter system as treatment groups and the other 50 were not injected (control groups). We analysed mRNA and protein expression of GFP and RFP using quantitative real-time PCR and confocal microscopy by developmental stages. The introduced reporter system could function beginning with the 4-cell stage. The expression of GFP and RFP was observed simultaneously in the early embryonic development stage up to blastocyst, indicating that porcine OCT4 was produced by distal and proximal enhancers, unlike mouse Oct4 expression, which was only controlled by the distal enhancer during early embryo development. Therefore, the mechanisms and functions of distal and proximal enhancers of porcine OCT4 were different from those of the mouse. This is similar to results of the previous experiment using porcine-induced pluripotent stem cells, which suggest that porcine OCT4 is expressed by two enhancers and in a stage-specific manner during reprogramming and that pigs do not use only one enhancer in pluripotent states, but two enhancers at the same time, and there is only a difference in degree. This work showed that the porcine OCT4 reporter system enables non-destructive analysis during early embryo development and it could be applied to study species-specific pluripotency and to help the establishment of naïve embryonic stem cells in the pig. This work was supported by the BK21 Plus Program, the National Research Foundation of Korea (NRF) grant funded by the Korea government (NRF-2019R1C1C1004514), the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Development of High Value-Added Food Technology Program funded by the Ministry of Agriculture, Food, and Rural Affairs (MAFRA; 118042-03-3-HD020).

42 Disruption of endogenous SOX2 during porcine embryo development using the CRIPSR/Cas9 system

The lineage specification of the pre-implantation embryo is important to understand the developmental process, but it remains unclear because the expression of lineage-specific genes is distinct among species. Pigs have genetic and physiological traits similar to humans; however, there are differences in gene expression during the pre-implantation stage. To select a candidate gene that affects the formation of the inner cell mass (ICM) in porcine embryo, we conducted preliminary experiments. First, we measured the expression level of candidate genes for lineage specification in parthenogenetic-activated embryos. The expression of pluripotent genes peaked on Day 3 and thereafter decreased gradually. Next, we conducted immunocytochemistry. OCT4 was expressed in all cells in morula and Day 5 blastocyst, but some Day 7 blastocysts expressed OCT4 in both ICM and trophectoderm (TE), whereas others expressed OCT4 only in ICM. NANOG was not observed in the morula stage, whereas SOX2 was located in a restricted area. To examine the effect of SOX2 in ICM formation, we injected plasmid expressing Cas9 and guide (g)RNA using Lipofectamine for efficient transgene expression at the 2-cell stage to increase viability by inducing mosaicism. The expression of enhanced green fluorescent protein (EGFP) contained in the plasmid confirmed that the plasmid was operating normally. In SOX2-knockout (KO) early blastocysts, the numbers of total cells and SOX2- and NANOG-positive cells were greatly decreased, while OCT4 was expressed in most cells. As in early blastocysts, SOX2-KO late blastocysts had fewer cells expressing SOX2, NANOG, and SOX17 than control. To identify the transcriptional consequences of SOX2 reduction, we performed quantitative PCR analysis on non-injected and PX458-gRNA injected blastocysts. Injection of PX458-gRNA resulted in downregulation of NANOG, SOX17, and SMAD7, but not SOX2 and OCT4. Furthermore, proliferation-associated genes were downregulated in injected blastocysts. In conclusion, SOX2-targeted porcine embryos showed blastocoel formation, the inner cell mass formed poorly, and embryos have inefficient cells. Also, the depletion of SOX2 in porcine blastocysts downregulated pluripotent genes and proliferation genes. This work was supported by the BK21 Plus Program, the National Research Foundation of Korea (NRF) grant funded by the Korea government (NRF-2019R1C1C1004514), the Korea Institute of Planning and Evaluation for Technology in Food, Agriculture and Forestry (IPET) through the Development of High Value-Added Food Technology Program funded by the Ministry of Agriculture, Food, and Rural Affairs (MAFRA; 118042-03-3-HD020).

Measurement of the Lund Jet Plane Using Charged Particles in 13 TeV Proton-Proton Collisions with the ATLAS Detector

The prevalence of hadronic jets at the LHC requires that a deep understanding of jet formation and structure is achieved in order to reach the highest levels of experimental and theoretical precision. There have been many measurements of jet substructure at the LHC and previous colliders, but the targeted observables mix physical effects from various origins. Based on a recent proposal to factorize physical effects, this Letter presents a double-differential cross-section measurement of the Lund jet plane using 139  fb^{-1} of sqrt[s]=13  TeV proton-proton collision data collected with the ATLAS detector using jets with transverse momentum above 675 GeV. The measurement uses charged particles to achieve a fine angular resolution and is corrected for acceptance and detector effects. Several parton shower Monte Carlo models are compared with the data. No single model is found to be in agreement with the measured data across the entire plane.

Measurement of Azimuthal Anisotropy of Muons from Charm and Bottom Hadrons in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

The elliptic flow of muons from the decay of charm and bottom hadrons is measured in pp collisions at sqrt[s]=13  TeV using a data sample with an integrated luminosity of 150  pb^{-1} recorded by the ATLAS detector at the LHC. The muons from heavy-flavor decay are separated from light-hadron decay muons using momentum imbalance between the tracking and muon spectrometers. The heavy-flavor decay muons are further separated into those from charm decay and those from bottom decay using the distance-of-closest-approach to the collision vertex. The measurement is performed for muons in the transverse momentum range 4-7 GeV and pseudorapidity range |η|<2.4. A significant nonzero elliptic anisotropy coefficient v_{2} is observed for muons from charm decays, while the v_{2} value for muons from bottom decays is consistent with zero within uncertainties.

Prospective randomized comparison of cerebrospinal fluid aspiration and conventional popping methods using 27-gauge spinal needles in patients undergoing spinal anaesthesia

Background

Performing spinal anaesthesia using the conventional popping method with a 27-gauge (27G) spinal needle is technically difficult. In this study, we compared the aspiration and conventional popping method for spinal anaesthesia using 27G Quincke-type needles.

Methods

This prospective, randomized study enrolled 90 patients, aged 19 to 65 years, with American Society of Anesthesiologists physical status I-III, who were undergoing spinal anaesthesia. Patients were randomly assigned to one of two groups using a computer-generated random number table: patients receiving spinal anaesthesia using the aspiration method, in which the needle is advanced with continuous aspiration, or the conventional popping method. The primary outcome measure was the success rate of the first attempt to perform dural puncture. Number of attempts and passages, withdrawal cases, successful attempt time, total procedure time, and actual depth of dural puncture were recorded.

Results

Eighty-eight patients were included in the study. In the aspiration group, the success rate of first attempt for dural puncture was 93.3%, compared with 72.1% in the popping group (P = 0.019). Success involving needle withdrawal was recorded in 4 (8.9%) patients in the aspiration group and 13 (30.2%) in the popping group (P = 0.024). In the popping group, the number of attempts was significantly higher (P = 0.044), and total procedure time was significantly longer (P = 0.023). Actual depths of dural puncture were deeper in the popping group than in the aspiration group (P = 0.019).

Conclusions

The aspiration method using a 27G Quincke-type needle offers clinical benefits for dural puncture compared with the conventional popping method for spinal anaesthesia.

Trial registration

Clinical research information service number: KCT0002815, registered 21/Apr/2018. Retrospectively registered.

Search for Magnetic Monopoles and Stable High-Electric-Charge Objects in 13 Tev Proton-Proton Collisions with the ATLAS Detector

A search for magnetic monopoles and high-electric-charge objects is presented using 34.4  fb^{-1} of 13 TeV pp collision data collected by the ATLAS detector at the LHC during 2015 and 2016. The considered signature is based upon high ionization in the transition radiation tracker of the inner detector associated with a pencil-shape energy deposit in the electromagnetic calorimeter. The data were collected by a dedicated trigger based on the tracker high-threshold hit capability. The results are interpreted in models of Drell-Yan pair production of stable particles with two spin hypotheses (0 and 1/2) and masses ranging from 200 to 4000 GeV. The search improves by approximately a factor of 5 the constraints on the direct production of magnetic monopoles carrying one or two Dirac magnetic charges and stable objects with electric charge in the range 20≤|z|≤60 and extends the charge range to 60<|z|≤100.

Observation of Electroweak Production of a Same-Sign W Boson Pair in Association with Two Jets in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

This Letter presents the observation and measurement of electroweak production of a same-sign W boson pair in association with two jets using 36.1  fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of sqrt[s]=13  TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69±7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial signal cross section is σ^{fid}=2.89_{-0.48}^{+0.51}(stat)_{-0.28}^{+0.29}(syst)  fb.

Observation of Light-by-Light Scattering in Ultraperipheral Pb+Pb Collisions with the ATLAS Detector

This Letter describes the observation of the light-by-light scattering process, γγ→γγ, in Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV. The analysis is conducted using a data sample corresponding to an integrated luminosity of 1.73  nb^{-1}, collected in November 2018 by the ATLAS experiment at the LHC. Light-by-light scattering candidates are selected in events with two photons produced exclusively, each with transverse energy E_{T}^{γ}>3  GeV and pseudorapidity |η_{γ}|<2.4, diphoton invariant mass above 6 GeV, and small diphoton transverse momentum and acoplanarity. After applying all selection criteria, 59 candidate events are observed for a background expectation of 12±3 events. The observed excess of events over the expected background has a significance of 8.2 standard deviations. The measured fiducial cross section is 78±13(stat)±7(syst)±3(lumi)  nb.

Comparison of Fragmentation Functions for Jets Dominated by Light Quarks and Gluons from pp and Pb+Pb Collisions in ATLAS

Charged-particle fragmentation functions for jets azimuthally balanced by a high-transverse-momentum, prompt, isolated photon are measured in 25  pb^{-1} of pp and 0.49  nb^{-1} of Pb+Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The measurements are compared to predictions of Monte Carlo generators and to measurements of inclusively selected jets. In pp collisions, a different jet fragmentation function in photon-tagged events from that in inclusive jet events arises from the difference in fragmentation between light quarks and gluons. The ratios of the fragmentation functions in Pb+Pb events to that in pp events are used to explore the parton color-charge dependence of jet quenching in the hot medium. In relatively peripheral collisions, fragmentation functions exhibit a similar modification pattern for photon-tagged and inclusive jets. However, photon-tagged jets are observed to have larger modifications than inclusive jets in central Pb+Pb events.

Combination of Searches for Invisible Higgs Boson Decays with the ATLAS Experiment

Dark matter particles, if sufficiently light, may be produced in decays of the Higgs boson. This Letter presents a statistical combination of searches for H→invisible decays where H is produced according to the standard model via vector boson fusion, Z(ℓℓ)H, and W/Z(had)H, all performed with the ATLAS detector using 36.1  fb^{-1} of pp collisions at a center-of-mass energy of sqrt[s]=13  TeV at the LHC. In combination with the results at sqrt[s]=7 and 8 TeV, an exclusion limit on the H→invisible branching ratio of 0.26(0.17_{-0.05}^{+0.07}) at 95% confidence level is observed (expected).