Observation of Single-Top-Quark Production in Association with a Photon Using the ATLAS Detector

This Letter reports the observation of single top quarks produced together with a photon, which directly probes the electroweak coupling of the top quark. The analysis uses 139  fb^{-1} of 13 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. Requiring a photon with transverse momentum larger than 20 GeV and within the detector acceptance, the fiducial cross section is measured to be 688±23(stat) _{-71}^{+75}(syst)  fb, to be compared with the standard model prediction of 515_{-42}^{+36}  fb at next-to-leading order in QCD.

Observation of the γγ→ττ Process in Pb+Pb Collisions and Constraints on the τ-Lepton Anomalous Magnetic Moment with the ATLAS Detector

This Letter reports the observation of τ-lepton-pair production in ultraperipheral lead-lead collisions Pb+Pb→Pb(γγ→ττ)Pb and constraints on the τ-lepton anomalous magnetic moment a_{τ}. The dataset corresponds to an integrated luminosity of 1.44  nb^{-1} of LHC Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV recorded by the ATLAS experiment in 2018. Selected events contain one muon from a τ-lepton decay, an electron or charged-particle track(s) from the other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations and a signal strength of μ_{ττ}=1.03_{-0.05}^{+0.06} assuming the standard model value for a_{τ}. To measure a_{τ}, a template fit to the muon transverse-momentum distribution from τ-lepton candidates is performed, using a dimuon (γγ→μμ) control sample to constrain systematic uncertainties. The observed 95% confidence-level interval for a_{τ} is -0.057 Collapse

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Strong Constraints on Jet Quenching in Centrality-Dependent p+Pb Collisions at 5.02 TeV from ATLAS

Jet quenching is the process of color-charged partons losing energy via interactions with quark-gluon plasma droplets created in heavy-ion collisions. The collective expansion of such droplets is well described by viscous hydrodynamics. Similar evidence of collectivity is consistently observed in smaller collision systems, including pp and p+Pb collisions. In contrast, while jet quenching is observed in Pb+Pb collisions, no evidence has been found in these small systems to date, raising fundamental questions about the nature of the system created in these collisions. The ATLAS experiment at the Large Hadron Collider has measured the yield of charged hadrons correlated with reconstructed jets in 0.36  nb^{-1} of p+Pb and 3.6  pb^{-1} of pp collisions at 5.02 TeV. The yields of charged hadrons with p_{T}^{ch}>0.5  GeV near and opposite in azimuth to jets with p_{T}^{jet}>30 or 60 GeV, and the ratios of these yields between p+Pb and pp collisions, I_{pPb}, are reported. The collision centrality of p+Pb events is categorized by the energy deposited by forward neutrons from the struck nucleus. The I_{pPb} values are consistent with unity within a few percent for hadrons with p_{T}^{ch}>4  GeV at all centralities. These data provide new, strong constraints that preclude almost any parton energy loss in central p+Pb collisions.

Search for Heavy Neutral Leptons in Decays of W Bosons Using a Dilepton Displaced Vertex in sqrt[s]=13 TeV pp Collisions with the ATLAS Detector

A search for a long-lived, heavy neutral lepton (N) in 139  fb^{-1} of sqrt[s]=13  TeV pp collision data collected by the ATLAS detector at the Large Hadron Collider is reported. The N is produced via W→Nμ or W→Ne and decays into two charged leptons and a neutrino, forming a displaced vertex. The N mass is used to discriminate between signal and background. No signal is observed, and limits are set on the squared mixing parameters of the N with the left-handed neutrino states for the N mass range 3  GeV Collapse

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Test of CP Invariance in Higgs Boson Vector-Boson-Fusion Production Using the H→γγ Channel with the ATLAS Detector

A test of CP invariance in Higgs boson production via vector-boson fusion has been performed in the H→γγ channel using 139  fb^{-1} of proton-proton collision data at sqrt[s]=13  TeV collected by the ATLAS detector at the LHC. The optimal observable method is used to probe the CP structure of interactions between the Higgs boson and electroweak gauge bosons, as described by an effective field theory. No sign of CP violation is observed in the data. Constraints are set on the parameters describing the strength of the CP-odd component in the coupling between the Higgs boson and the electroweak gauge bosons in two effective field theory bases: d[over ˜] in the HISZ basis and c_{HW[over ˜]} in the Warsaw basis. The results presented are the most stringent constraints on CP violation in the coupling between Higgs and weak bosons. The 95% C.L. constraint on d[over ˜] is derived for the first time and the 95% C.L. constraint on c_{HW[over ˜]} has been improved by a factor of 5 compared to the previous measurement.

Optimal selection of learning data for highly accurate QSAR prediction of chemical biodegradability: a machine learning-based approach

Prior to the manufacture of new chemicals, regulations mandate a thorough review of the chemicals under risk management. This review involves evaluating their effects on the environment and human health. To assess these effects, a review report that conforms to the OECD Test Guidelines must be submitted to the regulatory body. One of the essential components of the report is an assessment of the biodegradability of chemicals in the environment. In addition to conventional methods, quantitative structure-activity relationship (QSAR) models have been developed to predict the properties of chemicals based on their structural features. Although a greater number of chemicals in the learning set may enhance the prediction accuracy, it may also lead to a decrease in accuracy due to the mixing of different structural features and properties of the chemicals. To improve the prediction performance, it is recommended to use only the appropriate data for biodegradability prediction as a training set. In this study, we propose a novel approach for the optimal selection of training set that enables a highly accurate prediction of the biodegradability of chemicals by QSAR. Our findings indicate that the proposed method effectively reduces the root mean squared error and improves the prediction accuracy.

Case report: carcinosarcoma of the fallopian tube

Introduction/Objective

Carcinosarcoma is a malignant biphasic tumor composed of carcinomatous and sarcomatous elements. Carcinosarcoma of the fallopian tube is an extremely rare malignancy with fewer than 100 cases reported in the literature. We report a rare case of carcinosarcoma arising from the right fallopian tube.

Methods/Case Report

A 72-year-old female presented with worsening vaginal discharge and abdominal cramps.

Abdominal computed tomography detected a right adnexal mass. A torsed fallopian tube with a large mass was identified intraoperatively. Grossly, a 3.1 cm tan friable mass was seen protruding from the right fallopian tube lumen with numerous detached tumor fragments (9.4 cm in aggregate). Microscopically, the tumor was biphasic with a major mesenchymal component and minor epithelial component. A solid pattern of spindled and epithelioid cells with heterologous element of chondrosarcoma and a separate component with features of high-grade serous carcinoma in cribriform and solid sheets with slit-like spaces were seen. Both components showed marked nuclear atypia, pleomorphism, prominent nucleoli, and frequent mitoses. Both components were positive for p53, PAX-8, and beta- catenin immunohistochemistry, with a Ki-67 index of 80-90%. The sarcoma component was positive for p16, vimentin, and smooth muscle actin; the carcinoma component was positive for WT1, pan-cytokeratin, and cytokeratin 7. Pelvic washings were negative for malignancy. Metastases were not identified. Chemotherapy with paclitaxel and carboplatin was initiated with no recurrence identified 17 months after treatment.

Results (if a Case Study enter NA)

N/A

Conclusion

Proper identification and reporting of rare malignancies, such as this fallopian tube carcinosarcoma, with treatment and follow up, provide oncologists with the necessary information to advance treatment.

An Extremely Rare Case of Renal Collision Tumor Comprised of Hyperpigmented Microcystic Chromophobe Renal Cell Carcinoma and Papillary Renal Cell Carcinoma

Introduction/Objective

Renal collision tumors are rare lesions defined as the coexistence of two adjacent but histologically distinct tumors with sharp borders forming a single lesion. A combination of chromophobe renal cell carcinoma (ChRCC) and papillary renal cell carcinoma (RCC) is extremely rare. Here we report a collision tumor of hyperpigmented microcystic ChRCC, an uncommon variant of ChRCC, and papillary RCC. To our knowledge, it is the first reported case of this particular combination.

Methods/Case Report

A 70-year-old male with aortic stenosis presented with dyspnea and renal insufficiency. A renal mass was discovered incidentally. MRI characterized the left renal mass as 7.2 cm and bilobed. Radical nephrectomy was performed. Grossly, the tumor was located in the upper pole and consisted of two distinct components separated by fibrous tissue: a 5.4 cm black/orange mottled tumor and an adjacent 5.0 cm yellow lobulated tumor. Histologically, the larger tumor displayed a microcystic and solid pattern comprised of large cells with pale cytoplasm, hyperchromatic wrinkled nuclei, perinuclear halos, prominent cell membranes, and extensive intracellular and extracellular brown-black pigment, consistent with hyperpigmented microcystic ChRCC. The adjacent tumor showed diagnostic features of papillary RCC including papillae with fibrovascular cores lined by columnar cells with low nuclear grade, abundant macrophages, and foci of psammomatous calcifications. The hyperpigmented microcystic ChRCC was positive for CD117 and negative for Melan-A. Papillary RCC was strongly positive for Cytokeratin7 and Vimentin.

Results (if a Case Study enter NA)

N/A

Conclusion

Meticulous examination of the histologic features, aided by immunohistochemistry, can generate an accurate diagnosis of collision tumor and direct to the appropriate treatment choice.

Observation of WWW Production in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

This Letter reports the observation of WWW production and a measurement of its cross section using 139  fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. Events with two same-sign leptons (electrons or muons) and at least two jets, as well as events with three charged leptons, are selected. A multivariate technique is then used to discriminate between signal and background events. Events from WWW production are observed with a significance of 8.0 standard deviations, where the expectation is 5.4 standard deviations. The inclusive WWW production cross section is measured to be 820±100 (stat)±80 (syst)  fb, approximately 2.6 standard deviations from the predicted cross section of 511±18  fb calculated at next-to-leading-order QCD and leading-order electroweak accuracy.

A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery

The standard model of particle physics1-4 describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model is a field that permeates all of space and interacts with fundamental particles5-9. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN10,11. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons-the carriers of the strong, electromagnetic and weak forces-are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (τ)) are well measured and indications of interactions with a second-generation particle (muons, μ) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model.

Assessment of Heating on Titanium Alloy Cerebral Aneurysm Clips during 7T MRI

BACKGROUND AND PURPOSE

Patients with cerebral aneurysms often undergo MR imaging after microsurgical clipping. Ultra-high-field MR imaging at 7T may provide high diagnostic capability in such clinical situations. However, titanium alloy clips have safety issues such as adverse interactions with static magnetic fields and radiofrequency-induced heating during 7T MR imaging. The purpose of this study was to quantitatively assess temperature increases on various types of titanium alloy aneurysm clips during 7T MR imaging.

MATERIALS AND METHODS

Five types of titanium alloy aneurysm clips were tested, including combinations of short, long, straight, angled, and fenestrated types. Each clip was set in a phantom filled with gelled saline mixed with polyacrylic acid and underwent 7T MR imaging with 3D T1WI with a spoiled gradient recalled acquisition in the steady-state technique. Temperature was chronologically measured at the tips of the clip blade and head, angled part of the clip, and 5 mm from the tip of the clip head using MR imaging-compatible fiber-optic thermometers.

RESULTS

Temperature increases at all locations for right-angled and short straight clips were <1°C. Temperature increases at the angled part for the 45° angled clip and the tip of the clip head for the straight fenestrated clip were >1°C. Temperature increases at all locations for the long straight clip were >2°C.

CONCLUSIONS

Temperature increases on the right-angled and short straight clips remained below the regulatory limit during 7T MR imaging, but temperature increases on the 45° angled, straight fenestrated, and long straight clips exceeded this limit.