Severity of gallstone, sludge or microlithiasis induced pancreatitis - all of the same?

BACKGROUND/AIM

Severity of microlithiasis and sludge-induced pancreatitis in comparison to gallstone-induced pancreatitis has never been studied for a lack of definition. In order to understand whether bile duct obstruction or other mechanisms contribute to biliary pancreatitis severity we performed a monocentric, retrospective cohort study.

METHODS

In this retrospective cohort study 263 patients with acute biliary pancreatitis treated at a tertiary care center from 2005 to 2021 were stratified according to the recent consensus definition for microlithiasis and sludge. The gallstone-pancreatitis cohort was compared to microlithiasis, sludge and suspected stone passage pancreatitis cohorts in terms of pancreatitis outcome, liver function and EUS/ERCP results using one-way ANOVA and Chi2 test. Multinomial logistic regression analysis was performed to correct for bias.

RESULTS

Microlithiasis and sludge-induced pancreatitis classified according to the revised Atlanta classification, did not present with a milder course than gallstone-induced pancreatitis (p = 0.62). Microlithiasis and sludge showed an increase in bilirubin on the day of admission to hospital, which was not significantly different from gallstone-induced pancreatitis (p = 0.36). The likelihood of detecting biliary disease on EUS resulting in bile duct clearance was highest on the day of admission and day 1, respectively.

CONCLUSION

Microlithiasis and sludge induce gallstone-equivalent impaired liver function tests and induce pancreatitis with similar severity compared with gallstone-induced acute biliary pancreatitis.

Gut microbiota predicts severity and reveals novel metabolic signatures in acute pancreatitis

OBJECTIVE

Early disease prediction is challenging in acute pancreatitis (AP). Here, we prospectively investigate whether the microbiome predicts severity of AP (Pancreatitis-Microbiome As Predictor of Severity; P-MAPS) early at hospital admission.

DESIGN

Buccal and rectal microbial swabs were collected from 424 patients with AP within 72 hours of hospital admission in 15 European centres. All samples were sequenced by full-length 16S rRNA and metagenomic sequencing using Oxford Nanopore Technologies. Primary endpoint was the association of the orointestinal microbiome with the revised Atlanta classification (RAC). Secondary endpoints were mortality, length of hospital stay and severity (organ failure >48 hours and/or occurrence of pancreatic collections requiring intervention) as post hoc analysis. Multivariate analysis was conducted from normalised microbial and corresponding clinical data to build classifiers for predicting severity. For functional profiling, gene set enrichment analysis (GSEA) was performed and normalised enrichment scores calculated.

RESULTS

After data processing, 411 buccal and 391 rectal samples were analysed. The intestinal microbiome significantly differed for the RAC (Bray-Curtis, p value=0.009), mortality (Bray-Curtis, p value 0.006), length of hospital stay (Bray-Curtis, p=0.009) and severity (Bray-Curtis, p value=0.008). A classifier for severity with 16 different species and systemic inflammatory response syndrome achieved an area under the receiving operating characteristic (AUROC) of 85%, a positive predictive value of 67% and a negative predictive value of 94% outperforming established severity scores. GSEA revealed functional pathway units suggesting elevated short-chain fatty acid (SCFA) production in severe AP.

CONCLUSIONS

The orointestinal microbiome predicts clinical hallmark features of AP, and SCFAs may be used for future diagnostic and therapeutic concepts.

TRIAL REGISTRATION NUMBER

NCT04777812.

Management of Sinistral Portal Hypertension after Pancreaticoduodenectomy

BACKGROUND

Sinistral, or left-sided, portal hypertension (SPH) is a rare cause of upper gastrointestinal (GI) hemorrhage resulting from obstruction of the splenic vein. Venous drainage from the spleen via collaterals can result in venous hemorrhage into both the retroperitoneal and intra-abdominal spaces due to increased venous blood pressure in peripancreatic and gastroduodenal vasculature. SPH can occur secondary to pancreatitis with thrombosis of the splenic vein. Another possible cause is the surgical ligation of the splenic vein as part of pancreaticoduodenectomy (PD). Although splenectomy has been traditionally considered as the treatment of choice to relieve venous hypertension, individual concepts for each patient have to be developed. Considering the venous collateral drainage pathways, a comprehensive approach involving surgical, endoscopic, and interventional radiology interventions may be necessary to address the underlying cause of variceal bleeding. Among these approaches, splenic artery embolization (SAE) has demonstrated efficacy in mitigating the adverse effects associated with elevated venous outflow pressure.

SUMMARY

This review summarizes key imaging findings in SPH patients after PD and highlights the potential of minimally invasive embolization for curative treatment of variceal hemorrhage.

KEY MESSAGES

(i) SPH is a potential consequence after major pancreas surgery. (ii) Collateral flow can lead to life-threatening abdominal bleeding. (iii) Depending on the origin and localization of the bleeding, a dedicated management is required, frequently involving interventional radiology techniques.

[Pancreatic cancer-screening or surveillance?]

BACKGROUND

Despite continuous improvement of diagnostic and therapeutic procedures, the number of new pancreatic ductal adenocarcinoma (PDAC) cases diagnosed annually almost equals the number of PDAC-related deaths. Prerequisite for curative treatment is a resectable tumor at the time of diagnosis. Individuals with genetic and/or familial risk profiles should therefore be screened and included in structured surveillance programs.

OBJECTIVES

Description of the status quo and usefulness of current PDAC screening and surveillance concepts.

METHODS

A selective literature search of current national and international guidelines including underlying literature was performed.

RESULTS

Nearly half of pancreatic cancer cases are missed by currently available surveillance programs, even in high-risk cohorts. Magnetic resonance imaging and endoscopic ultrasound supplemented by CA19‑9 (± HbA1c) are not accurate enough to ensure robust earlier pancreatic cancer detection. Complementary biomarker panels will take on a crucial diagnostic role in the future.

[Cystic pancreatic lesions-indications, timing and reasons for surveillance]

BACKGROUND

Cystic pancreatic lesions are detected incidentally at an increasing rate. Often, the patients present asymptomatically. Hence, the resulting clinical consequences remain challenging and unsettling for both physicians and patients.

OBJECTIVES

Status of current recommendations in handling cystic pancreatic lesions.

MATERIALS AND METHODS

Selective literature search of PubMed while taking current guidelines into account.

RESULTS

Correct diagnostic classification of the cystic lesion is crucial since further action depends on the type of cystic lesion. Resection is generally recommended for mucinous cystic neoplasms (MCN), solid pseudopapillary neoplasms (SPN), and intraductal papillary mucinous neoplasms (IPMN) with relevant risk criteria such as prominent main-duct dilation. Surveillance is recommended for IPMN without risk criteria, as long as comorbidities and life expectancy of the patient will allow preventive resection over the years. SCNs are benign and only symptomatic SCNs require resection. Inflammatory pancreatic cysts should only be treated under certain circumstances.

In-vitro model to mimic T cell subset change in human PDAC organoid co-culture

PURPOSE

Immunotherapies have largely failed as treatment options for pancreatic ductal adenocarcinoma (PDAC). In this field, clinical translational studies into personalized treatment are of fundamental importance. In our study, we model tumor-cell immune-cell interactions in a co-culture of primary human PDAC organoids and matched peripheral blood mononuclear cells (PBMCs).

METHODS

Using flow cytometry, we evaluated changes in T cell subtypes upon co-culture of patient-derived PDAC organoids and matched PBMCs.

RESULTS

After co-culturing PDAC organoids with PBMCs, we observed changes in CD4+, CD8+ and Treg cell populations. We observed favorable clinical outcome in patients whose PBMCs reacted to the co-culture with organoids.

CONCLUSION

This experimental model allows to investigate interactions between patient derived PDAC organoids and their PBMCs. This co-culture system could serve as a preclinical platform to guide personalized therapeutic strategies in the future.

Consensus definition of sludge and microlithiasis as a possible cause of pancreatitis

OBJECTIVE

In up to 20% of patients, the aetiology of acute pancreatitis (AP) remains elusive and is thus called idiopathic. On more detailed review these cases can often be explained through biliary disease and are amenable to treatment. Findings range from biliary sludge to microlithiasis but their definitions remain fluid and controversial.

DESIGN

A systematic literature review (1682 reports, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines) analysed definitions of biliary sludge and microlithiasis, followed by an online international expert survey (30 endoscopic ultrasound/hepatobiliary and pancreatic experts; 36 items) which led to definitions of both. These were consented by Delphi voting and clinically evaluated in a retrospective cohort of patients with presumed biliary pancreatitis.

RESULTS

In 13% of original articles and 19.2% of reviews, microlithiasis and biliary sludge were used synonymously. In the survey, 41.7% of experts described the term 'sludge' and 'microlithiasis' as identical findings. As a consequence, three definitions were proposed, agreed on and confirmed by voting to distinctly discriminate between biliary sludge (hyperechoic material without acoustic shadowing) and microlithiasis (echorich calculi of ≤5 mm with acoustic shadowing) as opposed to larger biliary stones, both for location in gallbladder and bile ducts. In an initial attempt to investigate the clinical relevance in a retrospective analysis in 177 confirmed cases in our hospital, there was no difference in severity of AP if caused by sludge, microlithiasis or stones.

CONCLUSION

We propose a consensus definition for the localisation, ultrasound morphology and diameter of biliary sludge and microlithiasis as distinct entities. Interestingly, severity of biliary AP was not dependent on the size of concrements warranting prospective randomised studies which treatment options are adequate to prevent recurrence.

Machine learning-based decision tool for selecting patients with idiopathic acute pancreatitis for endosonography to exclude a biliary aetiology

BACKGROUND

Biliary microlithiasis/sludge is detected in approximately 30% of patients with idiopathic acute pancreatitis (IAP). As recurrent biliary pancreatitis can be prevented, the underlying aetiology of IAP should be established.

AIM

To develop a machine learning (ML) based decision tool for the use of endosonography (EUS) in pancreatitis patients to detect sludge and microlithiasis.

METHODS

We retrospectively used routinely recorded clinical and laboratory parameters of 218 consecutive patients with confirmed AP admitted to our tertiary care hospital between 2015 and 2020. Patients who did not receive EUS as part of the diagnostic work-up and whose pancreatitis episode could be adequately explained by other causes than biliary sludge and microlithiasis were excluded. We trained supervised ML classifiers using H2O.ai automatically selecting the best suitable predictor model to predict microlithiasis/sludge. The predictor model was further validated in two independent retrospective cohorts from two tertiary care centers (117 patients).

RESULTS

Twenty-eight categorized patients' variables recorded at admission were identified to compute the predictor model with an accuracy of 0.84 [95% confidence interval (CI): 0.791-0.9185], positive predictive value of 0.84, and negative predictive value of 0.80 in the identification cohort (218 patients). In the validation cohort, the robustness of the prediction model was confirmed with an accuracy of 0.76 (95%CI: 0.673-0.8347), positive predictive value of 0.76, and negative predictive value of 0.78 (117 patients).

CONCLUSION

We present a robust and validated ML-based predictor model consisting of routinely recorded parameters at admission that can predict biliary sludge and microlithiasis as the cause of AP.

Independent Validation and Assay Standardization of Improved Metabolic Biomarker Signature to Differentiate Pancreatic Ductal Adenocarcinoma From Chronic Pancreatitis

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma cancer (PDAC) is a highly lethal malignancy requiring efficient detection when the primary tumor is still resectable. We previously developed the MxPancreasScore comprising 9 analytes and serum carbohydrate antigen 19-9 (CA19-9), achieving an accuracy of 90.6%. The necessity for 5 different analytical platforms and multiple analytical runs, however, hindered clinical applicability. We therefore aimed to develop a simpler single-analytical run, single-platform diagnostic signature.

METHODS

We evaluated 941 patients (PDAC, 356; chronic pancreatitis [CP], 304; nonpancreatic disease, 281) in 3 multicenter independent tests, and identification (ID) and validation cohort 1 (VD1) and 2 (VD2) were evaluated. Targeted quantitative plasma metabolite analysis was performed on a liquid chromatography-tandem mass spectrometry platform. A machine learning-aided algorithm identified an improved (i-Metabolic) and minimalistic metabolic (m-Metabolic) signatures, and compared them for performance.

RESULTS

The i-Metabolic Signature, (12 analytes plus CA19-9) distinguished PDAC from CP with area under the curve (95% confidence interval) of 97.2% (97.1%-97.3%), 93.5% (93.4%-93.7%), and 92.2% (92.1%-92.3%) in the ID, VD1, and VD2 cohorts, respectively. In the VD2 cohort, the m-Metabolic signature (4 analytes plus CA19-9) discriminated PDAC from CP with a sensitivity of 77.3% and specificity of 89.6%, with an overall accuracy of 82.4%. For the subset of 45 patients with PDAC with resectable stages IA-IIB tumors, the sensitivity, specificity, and accuracy were 73.2%, 89.6%, and 82.7%, respectively; for those with detectable CA19-9 >2 U/mL, 81.6%, 88.7%, and 84.5%, respectively; and for those with CA19-9 <37 U/mL, 39.7%, 94.1%, and 76.3%, respectively.

CONCLUSIONS

The single-platform, single-run, m-Metabolic signature of just 4 metabolites used in combination with serum CA19-9 levels is an innovative accurate diagnostic tool for PDAC at the time of clinical presentation, warranting further large-scale evaluation.

TRAIL Receptor Targeting Agents Potentiate PARP Inhibitor Efficacy in Pancreatic Cancer Independently of BRCA2 Mutation Status

Simple Summary

Research into pancreatic cancer has identified frequent changes in BRCA genes, especially in BRCA2, occurring in about 5% of patients. BRCA proteins help repair damaged DNA. Pancreatic cancers with alterations in BRCA genes are sensitive to treatment with PARP inhibitors. The PARP inhibitor olaparib can be used to treat pancreatic cancer with mutations in BRCA genes after response to standard platinum-based chemotherapy. Unfortunately, only a few patients with pancreatic cancer have mutations in BRCA genes. In this study, we show that the combination of olaparib and TRAIL can be more effective than olaparib alone in killing pancreatic cancer cells. Furthermore, we demonstrate that the combination of olaparib and TRAIL also kills cancer cells without BRCA2 mutations. Our results suggest a potential new combination therapy of olaparib and TRAIL for pancreatic cancer independent of BRCA2 mutations and may extend the limited applicability of PARP inhibitors in this disease.

Abstract

Chemotherapy, the standard treatment for pancreatic ductal adenocarcinoma (PDAC), has only a modest effect on the outcome of patients with late-stage disease. Investigations of the genetic features of PDAC have demonstrated a frequent occurrence of mutations in genes involved in homologous recombination (HR), especially in the breast cancer susceptibility gene 2 (BRCA2). Olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, is approved as a maintenance treatment for patients with advanced PDAC with germline BRCA1/2 mutations following a platinum-containing first-line regimen. Limitations to the use of PARP inhibitors are represented by the relatively small proportion of patients with mutations in BRCA1/2 genes and the modest capability of these substances of inducing objective response. We have previously shown that pancreatic cancer with BRCA2 mutations exhibits a remarkably enhanced sensitivity towards tumor-necrosis-factor-related apoptosis-inducing ligand (TRAIL) receptor-stimulating agents. We thus aimed to investigate the effect of combined treatment with PARP inhibitors and TRAIL receptor-stimulating agents in pancreatic cancer and its dependency on the BRCA2 gene status. The respective effects of TRAIL-targeting agents and the PARP inhibitor olaparib or of their combination were assessed in pancreatic cancer cell lines and patient-derived organoids. In addition, BRCA2-knockout and -complementation models were investigated. The effects of these agents on apoptosis, DNA damage, cell cycle, and receptor surface expression were assessed by immunofluorescence, Western blot, and flow cytometry. PARP inhibition and TRAIL synergized to cause cell death in pancreatic cancer cell lines and PDAC organoids. This effect proved independent of BRCA2 gene status in three independent models. Olaparib and TRAIL in combination caused a detectable increase in DNA damage and a concentration-dependent cell cycle arrest in the G2/M and S cell cycle phases. Olaparib also significantly increased the proportion of membrane-bound death receptor 5. Our results provide a preclinical rationale for the combination of PARP inhibitors and TRAIL receptor agonists for the treatment of pancreatic cancer and suggest that the use of PARP inhibitors could be extended to patients without BRCA2 mutations if used in combination with TRAIL agonists.

Influence of COVID-19 Pandemic on Endoscopic Procedures in Two European Large-Capacity Endoscopy Units: "Keep Calm, Keep Safe and Scope on?"

BACKGROUND

The COVID-19-pandemic poses challenges to the medical system and especially to endoscopic staff and patients. National, European and International societies provided recommendations on how to safely perform endoscopic procedures during the current pandemic. Until now, the effect of the current pandemic on tertiary endoscopy centers has not been reported.

OBJECTIVE

The aim of this was to analyze the influence of the early SARS-CoV2-pandemic on endoscopic care and work flow in 2 European tertiary endoscopy units.

METHODS

Data from 2 tertiary endoscopy units (Katowice and Munich) were retrospectively collected during the early pandemic and compared to an equivalent pre-pandemic period. Data include procedures, complications, benchmarks, and influence on endoscopy training.

RESULTS

During the early pandemic, we noted a highly significant decrease (49.1%) in the overall number of all endoscopies with a significant increase in therapeutic procedures. Besides, there were no significant differences in the number of urgent endoscopic retrograde cholangiopancreatography or interventional endoscopic ultrasound procedures. The exceptional situation reduced endoscopic procedures performed by trainees significantly.

CONCLUSIONS

The SARS-CoV2-pandemic halved the endoscopy service of 2 tertiary centers while maintaining an urgent therapeutic service. Recommended personal safety measures in endoscopy proved to be efficient and safe in preventing SARS-CoV2 infection of staff or spreading. Unnecessarily, the SARS-CoV2 pandemic prevented routine endoscopy training.

Study protocol P-MAPS: microbiome as predictor of severity in acute pancreatitis-a prospective multicentre translational study

Background

Acute pancreatitis (AP) is an inflammatory disorder that causes a considerable economic health burden. While the overall mortality is low, around 20% of patients have a complicated course of disease resulting in increased morbidity and mortality. There is an emerging body of evidence that the microbiome exerts a crucial impact on the pathophysiology and course of AP. For several decades multiple clinical and laboratory parameters have been evaluated, and complex scoring systems were developed to predict the clinical course of AP upon admission. However, the majority of scoring systems are determined after several days and achieve a sensitivity around 70% for early prediction of severe AP. Thus, continued efforts are required to investigate reliable biomarkers for the early prediction of severity in order to guide early clinical management of AP patients.

Methods

We designed a multi-center, prospective clinical-translational study to test whether the orointestinal microbiome may serve as novel early predictor of the course, severity and outcome of patients with AP. We will recruit 400 AP patients and obtain buccal and rectal swabs within 72 h of admission to the hospital. Following DNA extraction, microbiome analysis will be performed using 3rd generation sequencing Oxford Nanopore Technologies (ONT) for 16S rRNA and metagenomic sequencing. Alpha- and beta-diversity will be determined and correlated to the revised Atlanta classification and additional clinical outcome parameters such as the length of hospital stay, number and type of complications, number of interventions and 30-day mortality.

Discussion

If AP patients show a distinct orointestinal microbiome dependent on the severity and course of the disease, microbiome sequencing could rapidly be implemented in the early clinical management of AP patients in the future.

Trial registration: ClinicalTrials.gov Identifier: NCT04777812

Tuberculous perihepatic abscess and neurosarcoidosis: report of 2 uncommon manifestations of 2 common granulomatous diseases in 1 patient

Infections caused by pathogens of the Mycobacterium tuberculosis complex, i. e., tuberculosis (TB), and the non-infectious, autoimmune disease sarcoidosis are among the most common granulomatous diseases worldwide. Typically, the lung is the primary site of infection and manifestation, respectively which makes the two diseases important differential diagnoses. Both diseases can affect virtually all organ systems, albeit with significantly lower incidence. CASE PRESENTATION:  We report the case of a 50-year-old Indian man presenting with a tuberculous perihepatic abscess and a systemic inflammatory response after being diagnosed with neurosarcoidosis presenting as a single granuloma in the frontal lobe with lymphadenopathy in 2014. On day of admission the patient presented with right upper abdominal pain and fever for two weeks. With increased inflammatory parameters in serum and after finding of external CT images, a perihepatic abscess was suspected. This encapsulated cave was drained percutaneously under CT control. A high concentration of acid-fast rods was detected using ZN, PCR was positive for M. tuberculosis. Several samples of sputum and urine were microscopically negative but yielded growth of Mycobacteria after four weeks. DISCUSSION:  This is a case presenting with two different granulomatous diseases, each of which manifested itself in an atypical form. The tuberculous liver abscess might either be explained as a flare-up of latent tuberculosis under azathioprine therapy or as a reinfection acquired during one of several visits in the high-prevalence country India. In addition, it must be discussed whether the cerebral granuloma in 2014 could have been an early stage of tuberculous granuloma. Sensitivity of ZN staining is significantly reduced in cerebral samples, and negative PCR-results might be due to low germ load or methodical issues, e. g., decreased sensitivity in formalin fixated samples.

COVID-19 aus der Sicht der Gastroenterologie

COVID 19, caused by SARS-CoV2, a new variant of coronaviruses, typically presents with respiratory symptoms. However, in a significat number of patients different organs are involved in the disease, often including gastrointestinal symptoms. These could include loss of appetite, vomiting, abdominal pain and diarrhea, with diarrhea being associated with a more severe course of COVID-19. Because viral RNA can be detected in fecal samples, some implications for clinical routine in diagnostic and therapeutic procedures are grown. Until yet, no clear evidence is given regarding fecal-oral transmission of SARS-CoV2.

What Do We Currently Know about the Pathophysiology of Alcoholic Pancreatitis: A Brief Review

BACKGROUND

Alcoholic pancreatitis is a serious medical concern worldwide and remains to be one of the common causes of pancreatic disease.

SUMMARY

While alcohol consumption causes direct damage to pancreatic tissue, only a small percentage of active drinkers will develop pancreatitis. An explanation of this phenomenon is probably that alcohol increases pancreatic vulnerability to damage; however, the simultaneous presence of additional risk factors and pancreatic costressors is required to increase the risk of pancreatitis and its complications caused by alcohol misuse. Recently, a number of important genetic as well as environmental factors influencing the risk of alcoholic pancreatitis have been described.

KEY MESSAGES

In brief, this review reports established factors for the development of alcoholic pancreatitis and summarizes recent progress made in basic and clinical research.

Hypertonicity-enforced BCL-2 addiction unleashes the cytotoxic potential of death receptors

Attempts to exploit the cytotoxic activity of death receptors (DR) for treating cancer have thus far been disappointing. DR activation in most malignant cells fails to trigger cell death and may even promote tumor growth by activating cell death-independent DR-associated signaling pathways. Overcoming apoptosis resistance is consequently a prerequisite for successful clinical exploitation of DR stimulation. Here we show that hyperosmotic stress in the tumor microenvironment unleashes the deadly potential of DRs by enforcing BCL-2 addiction of cancer cells. Hypertonicity robustly enhanced cytotoxicity of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and other DR ligands in various cancer entities. Initial events in TRAIL DR signaling remained unaffected, but hypertonic conditions unlocked activation of the mitochondrial death pathway and thus amplified the apoptotic signal. Mechanistically, we demonstrate that hyperosmotic stress imposed a BCL-2-addiction on cancer cells to safeguard the integrity of the outer mitochondrial membrane (OMM), essentially exhausting the protective capacity of BCL-2-like pro-survival proteins. Deprivation of these mitochondrial safeguards licensed DR-generated truncated BH3-interacting domain death agonist (tBID) to activate BCL-2-associated X protein (BAX) and initiated mitochondrial outer membrane permeabilization (MOMP). Our work highlights that hyperosmotic stress in the tumor environment primes mitochondria for death and lowers the threshold for DR-induced apoptosis. Beyond TRAIL-based therapies, our findings could help to strengthen the efficacy of other apoptosis-inducing cancer treatment regimens.

First Measurement of Transverse-Spin-Dependent Azimuthal Asymmetries in the Drell-Yan Process

The first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan (DY) process is reported. We use the CERN SPS 190  GeV/c π^{-} beam and a transversely polarized ammonia target. Three azimuthal asymmetries giving access to different transverse-momentum-dependent (TMD) parton distribution functions (PDFs) are extracted using dimuon events with invariant mass between 4.3  GeV/c^{2} and 8.5  GeV/c^{2}. Within the experimental uncertainties, the observed sign of the Sivers asymmetry is found to be consistent with the fundamental prediction of quantum chromodynamics (QCD) that the Sivers TMD PDFs extracted from DY have a sign opposite to the one extracted from semi-inclusive deep-inelastic scattering (SIDIS) data. We present two other asymmetries originating from the pion Boer-Mulders TMD PDFs convoluted with either the nucleon transversity or pretzelosity TMD PDFs. A recent COMPASS SIDIS measurement was obtained at a hard scale comparable to that of these DY results. This opens the way for possible tests of fundamental QCD universality predictions.

Observation of a New Narrow Axial-Vector Meson a1(1420)

The COMPASS Collaboration at CERN has measured diffractive dissociation of 190  GeV/c pions into the π(-)π(-)π(+) final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers J(PC)=1(++). We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with J(PC)=2(++) and 4(++) decaying into ρ(770)π and with J(PC)=1(++) decaying into f0(980)π. We identify a new a1 meson with mass (1414(-13)(+15))  MeV/c2 and width (153(-23)(+8))  MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.

Measurement of the charged-pion polarizability

The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q(2)<0.0015  (GeV/c)(2). From a sample of 63,000 events, the pion electric polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4)  fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.