Measurement of the Centrality Dependence of the Dijet Yield in p+Pb Collisions at sqrt[s_{NN}]=8.16 TeV with the ATLAS Detector

ATLAS measured the centrality dependence of the dijet yield using 165  nb^{-1} of p+Pb data collected at sqrt[s_{NN}]=8.16  TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, R_{CP}, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The R_{CP} shows a scaling with the Bjorken x of the parton originating from the proton, x_{p}, while no such trend is observed as a function of x_{Pb}. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to x_{p}∼10^{-3} and x_{Pb}∼4×10^{-4}.

Search for New Phenomena in Two-Body Invariant Mass Distributions Using Unsupervised Machine Learning for Anomaly Detection at sqrt[s]=13 TeV with the ATLAS Detector

Searches for new resonances are performed using an unsupervised anomaly-detection technique. Events with at least one electron or muon are selected from 140  fb^{-1} of pp collisions at sqrt[s]=13  TeV recorded by ATLAS at the Large Hadron Collider. The approach involves training an autoencoder on data, and subsequently defining anomalous regions based on the reconstruction loss of the decoder. Studies focus on nine invariant mass spectra that contain pairs of objects consisting of one light jet or b jet and either one lepton (e,μ), photon, or second light jet or b jet in the anomalous regions. No significant deviations from the background hypotheses are observed. Limits on contributions from generic Gaussian signals with various widths of the resonance mass are obtained for nine invariant masses in the anomalous regions.

Silent Infections are not So Silent: The Emerging Role of Combined Infections, Inflammation, and Vitamin Levels in OCD

Objective

Recent evidence highlights that different agents may trigger immune-mediated processes involved in the pathophysiology of different neuropsychiatric conditions. Given the limited information on obsessive-compulsive disorder (OCD), the present study aimed at assessing current/past infections and plasma levels of vitamin D, vitamin B12, folic acid, homocysteine and common peripheral inflammatory markers in a group of OCD outpatients.

Method

The sample included 217 adult outpatients with an OCD diagnosis according to the DSM-5 criteria. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) was used to assess the clinical phenotype and symptom severity. Laboratory blood tests measured levels of vitamin D, vitamin B12, folic acid, homocysteine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), blood count and antibodies titers for cytomegalovirus (CMV), Epstein Barr virus (EBV), Toxoplasma gondii and antistreptolysin titer.

Results

Sixty-one patients had a previous EBV infection, 46 were seropositive for CMV IgG, 24 showed positive antistreptolysin titer, 14 were seropositive for Toxoplasma gondii IgG, and four for CMV IgM. More than a half of patients showed vitamin D insufficiency. Compared to seronegative patients, patients with a past EBV infection displayed significantly higher scores on the Y-BOCS total score and compulsion subscale, and other symptoms. Vitamin D was negatively correlated with both the Y-BOCS total score and the subscales scores. Folic acid was negatively correlated with the Y-BOCS total and obsessions subscale score.

Conclusions

The findings of our study show an association between Epstein-Barr infection and hypovitaminosis D and the overall severity and specific symptom patterns of OCD. The laboratory measures used in this study are useful, cheap and easy parameters that should be routinely assessed in patients with OCD. Further studies are needed to clarify their role in OCD pathophysiology and outcomes, as well as the potential therapeutic impact of vitamins and antibiotics/immunomodulatory agents in OCD and other psychiatric conditions.

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

This Letter reports the observation of WZγ production and a measurement of its cross section using 140.1±1.2  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. The WZγ production cross section, with both the W and Z bosons decaying leptonically, pp→WZγ→ℓ^{'}^{±}νℓ^{+}ℓ^{-}γ (ℓ^{(^{'})}=e, μ), is measured in a fiducial phase-space region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01±0.30(stat)±0.16(syst)  fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50±0.06  fb. The observed significance of the WZγ signal is 6.3σ, compared with an expected significance of 5.0σ.

Combined Measurement of the Higgs Boson Mass from the H→γγ and H→ZZ^{*}→4ℓ Decay Channels with the ATLAS Detector Using sqrt[s]=7, 8, and 13 TeV pp Collision Data

A measurement of the mass of the Higgs boson combining the H→ZZ^{*}→4ℓ and H→γγ decay channels is presented. The result is based on 140  fb^{-1} of proton-proton collision data collected by the ATLAS detector during LHC run 2 at a center-of-mass energy of 13 TeV combined with the run 1 ATLAS mass measurement, performed at center-of-mass energies of 7 and 8 TeV, yielding a Higgs boson mass of 125.11±0.09(stat)±0.06(syst)=125.11±0.11  GeV. This corresponds to a 0.09% precision achieved on this fundamental parameter of the Standard Model of particle physics.

Search for Dark Photons in Rare Z Boson Decays with the ATLAS Detector

A search for events with a dark photon produced in association with a dark Higgs boson via rare decays of the standard model Z boson is presented, using 139  fb^{-1} of sqrt[s]=13  TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider. The dark boson decays into a pair of dark photons, and at least two of the three dark photons must each decay into a pair of electrons or muons, resulting in at least two same-flavor opposite-charge lepton pairs in the final state. The data are found to be consistent with the background prediction, and upper limits are set on the dark photon's coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, α_{D}ϵ^{2}, in the dark photon mass range of [5, 40] GeV except for the ϒ mass window [8.8, 11.1] GeV. This search explores new parameter space not previously excluded by other experiments.

A "transatlantic" follow-up study of the impact of the COVID-19 pandemic on patients with obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive symptom fluctuations may be contingent on the number of stressful pandemic-related events and the resilience characterizing different cultures. We investigated the influence of the pandemic on symptom changes in a sample of obsessive-compulsive disorder (OCD) patients from Brazil and Italy, two countries that were highly affected by the outbreak.

METHODS

Ninety-one OCD outpatients were evaluated at baseline and about one year later. Thirty of them were assessed in Brazil and 61 in Italy. Socio-demographic variables, symptoms' severity and the number of stressful pandemic-related events were collected. Comparisons between countries' samples were performed, and a linear regression examined whether the country of origin, demographic features and the number of stressful events were able to predict the symptoms' severity at the follow-up.

RESULTS

Brazilian patients experienced more stressful pandemic-related events than Italian patients (p = 0.018). However, along with higher age (p < 0.01) and increased severity of symptoms at baseline (p < 0.01), lower number of events predicted increased symptoms' severity after one year (p < 0.01). Country of origin was not a significant predictor of severity.

LIMITATIONS

Small number of subjects; lack of information regarding duration of illness; and potential sample differences between countries.

CONCLUSIONS

During the pandemic, the occurrence of more stressful pandemic-related events was associated with decreased severity of patients' OCD symptoms. Nevertheless, older patients and those with more severe symptoms seemed prone to exhibit increased OCD severity at follow-up.

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.

Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in Pb+Pb Collisions at sqrt[s_{NN}]=5.02 TeV with the ATLAS Detector

This letter presents a measurement of the nuclear modification factor of large-radius jets in sqrt[s_{NN}]=5.02  TeV Pb+Pb collisions by the ATLAS experiment. The measurement is performed using 1.72  nb^{-1} and 257  pb^{-1} of Pb+Pb and pp data, respectively. The large-radius jets are reconstructed with the anti-k_{t} algorithm using a radius parameter of R=1.0, by reclustering anti-k_{t} R=0.2 jets, and are measured over the transverse momentum (p_{T}) kinematic range of 158 Collapse

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Measurement of the Sensitivity of Two-Particle Correlations in pp Collisions to the Presence of Hard Scatterings

A key open question in the study of multiparticle production in high-energy pp collisions is the relationship between the "ridge"-i.e., the observed azimuthal correlations between particles in the underlying event that extend over all rapidities-and hard or semihard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. To address this question, two-particle correlations are measured in pp collisions at sqrt[s]=13  TeV using data collected by the ATLAS experiment at the LHC, with an integrated luminosity of 15.8  pb^{-1}, in two different configurations. In the first case, charged particles associated with jets are excluded from the correlation analysis, while in the second case, correlations are measured between particles within jets and charged particles from the underlying event. Second-order flow coefficients, v_{2}, are presented as a function of event multiplicity and transverse momentum. These measurements show that excluding particles associated with jets does not affect the measured correlations. Moreover, particles associated with jets do not exhibit any significant azimuthal correlations with the underlying event, ruling out hard processes contributing to the ridge.

Observation of an Excess of Dicharmonium Events in the Four-Muon Final State with the ATLAS Detector

A search is made for potential ccc[over ¯]c[over ¯] tetraquarks decaying into a pair of charmonium states in the four muon final state using proton-proton collision data at sqrt[s]=13  TeV, corresponding to an integrated luminosity of 140  fb^{-1} recorded by the ATLAS experiment at LHC. Two decay channels, J/ψ+J/ψ→4μ and J/ψ+ψ(2S)→4μ, are studied. Backgrounds are estimated based on a hybrid approach involving Monte Carlo simulations and data-driven methods. Statistically significant excesses with respect to backgrounds dominated by the single parton scattering are seen in the di-J/ψ channel consistent with a narrow resonance at 6.9 GeV and a broader structure at lower mass. A statistically significant excess is also seen in the J/ψ+ψ(2S) channel. The fitted masses and decay widths of the structures are reported.

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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Decreased vitamin D levels in obsessive-compulsive disorder patients

OBJECTIVE

The present paper compared vitamin D levels in adult patients with obsessive-compulsive disorder (OCD) and explored possible correlations with patients' characteristics.

METHODS

Fifty outpatients with OCD, according to DSM-5 criteria, were included and assessed with the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the Hamilton Rating Scale for Depression (HRDS).

RESULTS

All the patients except one showed lower vitamin D levels than normative values (>30 nm/L). Vitamin D values of the whole sample were negatively correlated with Y-BOCS total, compulsion subscale, and some items' scores, specifically "interference from obsessions," "distress associated with obsessions," and "time spent on compulsions". The same relationships were detected in men, while women showed negative correlations between vitamin D levels and Y-BOCS compulsion subscale and "resistance to compulsions," "degree of control of compulsions," "insight" item scores.

CONCLUSIONS

Our findings would indicate that vitamin D might be involved in the pathophysiology of OCD, and that it is possibly related to the severity of the disorder and to typical symptoms, with some sex-related peculiarities. Further studies are necessary to support or not our findings and to ascertain the effectiveness of vitamin D supplementation in patients with OCD.

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.

Decreased Levels of Vitamin D in Bipolar Patients

Recently, vitamin D is considered a pleiotropic hormone, and as such, it has also become a topic of renewed interest in neuropsychiatry for its proposed role in the aetiology and pathophysiology of different psychiatric conditions, including mood disorders (MDs). This seems particularly crucial while considering the relatively high and often neglected prevalence of hypovitaminosis D in the general population and in specific groups, such as patients suffering from the most common type of MDs, which are major depression (MDD) and bipolar disorders (BDs). Therefore, in view of the controversial literature and findings on this topic and its potential therapeutic implications, the present study aimed at evaluating vitamin D levels in the plasma of a sample of inpatients fulfilling the DSM-5 criteria for mood episodes within BDs. The clinical picture was assessed by means of specific rating scales. The results showed that the vitamin D levels (mean ± SD, nM/L) of the bipolar patients of our sample were significantly lower (14.58 ± 11.27 nmol/L) than the normative values (>30 nmol/L). Eleven patients had sufficient values and only 4 had optimal, while 19 showed insufficient, 18 critical, and 17 severely critical levels. No differences emerged according to different socio-demographic or clinical features. In our opinion, the present findings strengthen previous research highlighting decreased vitamin D levels in bipolar patients and support the role of this pleiotropic hormone in BDs. Nevertheless, further studies should follow to corroborate the data of this preliminary study and to address the potential benefits of vitamin D supplementation in the treatment of MDs.

Binge eating disorder, impulsivity and bipolar spectrum features in a sample of obese candidates for bariatric surgery

AIMS

Candidates for bariatric surgery are routinely screened for psychiatric disorders because abnormal eating behaviors are considered common among these patients. This study aimed to evaluate the frequency and persistence, in terms of one month-to-lifetime prevalence ratio, of binge eating disorder (BED) and the potential association with impulsivity features and bipolar spectrum comorbidity in a sample of obese patients undergoing a psychiatric evaluation for bariatric intervention.

METHODS

Overall, 80 candidates to bariatric surgery were assessed consecutively over 12 months within the framework of a collaboration between the University of Pisa Psychiatry and Internal Medicine Departments. Patients were evaluated through structured clinical interviews and self-report questionnaires.

RESULTS

The lifetime and last-month frequencies of BED according to DSM-5 criteria were 46.3% and 17.5%, respectively, with a prevalence ratio of 37.8%. Rates of formal bipolar disorder diagnoses were extremely low in patients with or without BED. However, patients with BED showed more severe dyscontrol, attentional impulsivity and bipolar spectrum features than patients with no BED.

CONCLUSIONS

The relationship of BED, impulsivity, and mood disorders in bariatric patients is more complex than usually reported in the literature. In particular, the presence of bipolar spectrum features should be systematically investigated in these patients because of their essential clinical and therapeutical implications.

Poor sleep quality may contribute to dysfunctional illness perception, physical and emotional distress in hospitalised patients: results of a national survey of the Italian Society of Consultation-Liaison Psychiatry

Distress associated with physical illness is a well-known risk factor for adverse illness course in general hospitals. Understanding the factors contributing to it should be a priority and among them dysfunctional illness perception and poor sleep quality may contribute to it. As poor sleep quality is recognised as a major risk factor for health problems, we aimed to study its association with illness perception and levels of distress during hospitalisation. This cross-sectional study included a consecutive series of 409 individuals who were hospitalised in medical and surgical units of different hospitals located throughout the Italian national territory and required an assessment for psychopathological conditions. Sleep quality was assessed with the Pittsburgh (Sleep Quality Index), emotional and physical distress with the Edmonton Symptom Assessment System (ESAS), and illness perception with the Brief Illness Perception Questionnaire (BIPQ). Differences between groups, correlations and mediations analyses were computed. Patients with poor sleep quality were more frequently females, with psychiatric comorbidity, with higher scores in the ESAS and BIPQ. Poor sleep quality was related to dysfunctional illness perception, and to both emotional and physical distress. In particular, by affecting cognitive components of illness perception, poor sleep quality may, directly and indirectly, predict high levels of distress during hospitalisation. Poor sleep quality may affect >70% of hospitalised patients and may favour dysfunctional illness perception and emotional/physical distress.Assessing and treating sleep problems in hospitalised patients should be included in the routine of hospitalised patients.

Obsessive-Compulsive Disorder, PANDAS, and Tourette Syndrome: Immuno-inflammatory Disorders

In the last years, much focus has been given to the possible role of inflammatory and immunologic alterations in the pathophysiology of obsessive-compulsive disorder (OCD) and some related conditions, such as pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) and Tourette syndrome (TS). Although the matter is intriguing, the available data are still controversial and/or limited. Therefore, the aim of this chapter was at reviewing and commenting on the literature on possible dysfunctions of inflammatory and immune system processes in OCD, PANDAS, and TS.This narrative review was carried out through searching PubMed and Google Scholar for English language papers from January 1985 to December 31, 2021.The data gathered up to now would suggest that the mechanisms involved might be heterogeneous according to the age of the patients and the disorder examined. Indeed, PANDAS seem more related to infections triggering autoimmunity not necessarily following group A beta-hemolytic streptococcal (GABHS) infection, as supposed in the past. Autoimmunity seems also important in TS, if coupled with an individual vulnerability that can be genetic and/or environmental. The data in adult OCD, albeit scattered and sometimes obtained in small samples of patients, would indicate that immune system and inflammatory processes are involved in the pathophysiology of the disorder. However, it is still unclear to conclude whether they are primary or secondary phenomena.In conclusion, taken together, the current findings pave that way towards novel and promising domains to explore the pathophysiology of OCD and related disorders, as well towards the development of innovative therapeutic strategy beyond current pharmacological paradigms.

Vitamin B12, homocysteine, and folic acid in patients suffering from bipolar disorders: Relationship with suicide

OBJECTIVES

Vitamin B12, folic acid, and homocysteine play a key role in 'one-carbon metabolism', involved in different brain processes. Altered levels have been reported in mood disorders (MDs), particularly in major depression (MDD), while the information in bipolar disorders (BDs) is limited. The present study aimed at assessing vitamin B12, homocysteine, and folic acid in 69 bipolar inpatients.

METHODS

Twenty-seven patients were diagnosed with BDI, 15 BDII, 16 schizoaffective disorders, and 11 MDD, according to DSM-5 criteria. The clinical picture was assessed by the MINI, HRSD, YMRS, and CGI. The blood parameters were measured according to common clinical-chemical methods.

RESULTS

Thirty-four patients had significantly lower vitamin B12, and 14 higher homocysteine levels than normative values. Folic acid levels were normal in the majority of the sample. Patients with a family history of suicide showed significantly lower levels of vitamin B12.

CONCLUSIONS

Our results underline the utility of assessing vitamin B12, homocysteine, and folic acid in patients with BD. Although other studies are necessary, the present findings that lower levels of vitamin B12 seem typical of patients with a family history of suicide independently from the phase of illness suggest that they might constitute a possible predictor of suicide.

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.

Focus on neuroenhancement: a systematic review and its ethical implications

Introduction

Pharmacological and cognitive neuroenhancement refer to the non-medical use of prescription drugs, alcohol, illegal drugs, or the so-called soft enhancers, to enhance cognition, mood, work or school performance, or to promote pro-social behaviour. Literature on the topic is meagre, and available data only partially enlightens their use.

Objectives

The aim of this paper is to review and comment on the available literature on pharmacological neuroenhancement and, secondary, on emotional enhancement.

Methods

A systematic review was conducted according to the PRISMA guidelines. Pubmed, Scopus, Embase, PsychInfo and Google Scholar databases were accessed to select English language articles, published from 1980 to April 2020. 11746 papers were initially selected and 123 papers were finally included.

Results

Available literature indicates a widespread and increasing use of different kinds of substances, drugs and food supplements mainly with neuroenhancing purposes, especially amongst specific populations of young healthy subjects. The evidence regarding their efficacy is controversial. Further, a limited or no awareness regarding the possible consequences of their abuse/misuse emerges amongst users.

Conclusions

Despite the limited evidence that some substances may improve cognitive functions in healthy subjects and neglecting their detrimental side effects and potential risk of misuse, abuse and addiction, there is an increasing worldwide use of the so-called neuroenhancers, especially in some categories of individuals, such as university students. Further studies are needed to collect reliable data on the effects of neuroenhancers in healthy subjects. Neuroenhancement puts into question the concept of authenticity, so that the problem requires to be analyzed within a complex ethical conceptual frame.

Disclosure

No significant relationships.

Circadian Rhythm Alterations May be Related to Impaired Resilience, Emotional Dysregulation and to the Severity of Mood Features in Bipolar I and II Disorders

Objective

The study aimed to investigate the possible impact of resilience and emotion dysregulation on the clinical manifestations of bipolar disorders (BDs) focusing on the possible role of circadian rhythm alterations.

Method

A sample of 197 inpatients suffering from BD of type I (BDI) or II (BDII) were assessed during a major depressive episode using the Structural Clinical Interview for DSM-5 (SCID-5), the Beck Depression Inventory-II (BDI-II), the Young Mania Rating Scale (YMRS), Resilience Scale for Adults (RSA), Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN), Difficulties in Emotion Regulation Scale (DERS) and the Scale for Suicide Ideation (SSI). Participants with or without circadian rhythm disturbances as measured with Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN), were compared; regression and mediation analyses were computed.

Results

Participants with circadian rhythms disturbances showed a greater severity of depressive symptoms, of suicidal risk, lower resilience and more disturbances in emotion regulation including impulsivity and regulatory strategies. The logistic regression revealed that circadian rhythm disturbances was related to depressive symptoms (O.R. 4.0), suicidal risk (OR 2.51), emotion dysregulation (OR 2.28) and low resilience (OR 2.72). At the mediation analyses, circadian rhythm alterations showed an indirect effect on depressive symptoms by impairing resilience (Z= 3.17, p=0.0014)/ emotional regulation (Z= 4.36, p<0.001) and on suicidal risk by affecting resilience (Z= 2.00, p=0.045) and favoring impulsivity (Z= 2.14, p=0.032).

Conclusions

The present findings may show that circadian rhythm alterations might play a key role in BD manifestations, as being correlated with more severe clinical presentations of depressive symptoms, suicidal risk, impaired resilience and emotional regulation. Addressing circadian rhythm alterations might potentially promote resilience and emotion regulation hence improving mood symptoms and suicidal risk in BDs.

Characteristics of psychiatric comorbidities in emergency medicine setting and impact on length of hospitalization: A retrospective study

This study aims to evaluate clinical correlates of psychiatric comorbidity and length of hospitalization in patients admitted in a general hospital emergency medicine setting. Overall, 160 patients hospitalized for different acute medical pathologies were selected consecutively over 12 months. All subjects were evaluated with proper forms to collect data on medical and psychiatric diagnoses. Levels of C-reactive protein were also measured in all patients. Statistical analyses were conducted with univariate, logistic, and multiple linear regressions. Patients with psychiatric comorbidity had significantly longer hospitalization than did patients with no psychiatric diagnoses (days 10.9±9.5 vs. 6.9±4.5, p<0.005). Agitation and delirium were more frequent in the psychiatry comorbidity study group (p<0.05), as was cognitive impairment (p=0.001). These variables predicted longer hospitalisation (respectively: t=-3.27, p=0.002; t=-2.64, p=0.009; t=-2.85, p=0.006). Psychiatric comorbidity acts as an adjunct factor in determining clinical severity and predicting a more difficult recovery in patients hospitalized in an emergency medicine setting.

Changes of consultation-liaison psychiatry practice in Italian general hospitals: A comparative 20-year multicenter study

INTRODUCTION

Conducted under the auspices of the Italian Society of Consultation Liaison Psychiatry (SIPC) the aim of this study was to describe the characteristics of Consultation Liaison Psychiatry (CLP) activity in Italy (SIPC-2-2018) over the past 20 years by comparing with data from the first Italian nation-wide study (SIPC-1-1998).

METHODS

We collected data on CLP visits of 3,943 patients from 10 Italian hospitals over a period of 1 year. Data were compared with those from the SIPC-1 1998 study (4,183 participants). Patients were assessed with the same ad hoc 60-item Patient Registration Form recording information from five different areas: Sociodemographic, hospitalization-related, consultation-related, interventions and outcome.

RESULTS

Compared with participants from the previous study, SIPC-2-2018 participants were significantly older (d = 0.54) and hospitalized for a longer duration (d = 0.20). The current study detected an increase in the proportion of referrals from surgical wards and for individuals affected by onco-hematologic diseases. Depressive disorders still represented the most frequent psychiatric diagnosis, followed by adjustment and stress disorders and delirium/dementia. Also, CLP psychiatrists prescribed more often antidepressants (Φ = 0.13), antipsychotics (Φ = 0.09), mood stabilizers (Φ = 0.24), and less often benzodiazepines (Φ = 0.07).

CONCLUSION

CLP workload has increased considerably in the past 20 years in Italy, with changes in patient demographic and clinical characteristics. A trend toward increase in medication-based patient management was observed. These findings suggest that the psychiatric needs of patients admitted to the general hospital are more frequently addressed by referring physicians, although Italian CLP services still deserve better organization and autonomy.

Search for Lepton-Flavor Violation in Z-Boson Decays with τ Leptons with the ATLAS Detector

A search for lepton-flavor-violating Z→eτ and Z→μτ decays with pp collision data recorded by the ATLAS detector at the LHC is presented. This analysis uses 139  fb^{-1} of Run 2 pp collisions at sqrt[s]=13  TeV and is combined with the results of a similar ATLAS search in the final state in which the τ lepton decays hadronically, using the same data set as well as Run 1 data. The addition of leptonically decaying τ leptons significantly improves the sensitivity reach for Z→ℓτ decays. The Z→ℓτ branching fractions are constrained in this analysis to B(Z→eτ)<7.0×10^{-6} and B(Z→μτ)<7.2×10^{-6} at 95% confidence level. The combination with the previously published analyses sets the strongest constraints to date: B(Z→eτ)<5.0×10^{-6} and B(Z→μτ)<6.5×10^{-6} at 95% confidence level.

Obsessive-Compulsive and Depressive Symptoms in Professional Tennis Players

OBJECTIVE

A moderate sport activity is considered beneficial for both physical and mental health. On the contrary, different studies have shown that professional players may be more vulnerable to suffer from psychological and/or psychiatric disorders. Given the limited information available, the present study aimed to investigate the possible presence of depressive and obsessive-compulsive symptoms or disorders in a group of professional tennis players.

METHOD

Twenty-five current or former professional tennis players (18 men and 7 women; mean age ± SD: 42.32 ± 13.45 years), were recruited within the Italian Tennis Federation during an international competition and during a master meeting of coaches. They were compared with a control group, recruited from university students, doctors and nurses. All of them underwent a psychiatric interview with a structured scale and a psychopathological assessment carried out with the Mini-International Neuropsychiatric Interview (MINI), the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) and the Self Assessment Scale for Depression (SAD).

RESULTS

The Y-BOCS total and subscale scores were significantly higher in both current and past athletes than controls. Current athletes showed higher scores at Y-BOCS total, subscales and some items. The majority of the current athletes also showed superstitions and magical thinking.

CONCLUSIONS

The present study demonstrated that professional tennis players show a relevant increase of obsessive-compulsive symptoms and supertistions than controls. Interestingly, current athletes resulted more severe than past ones. Taken together, our findings support the notion that agonistic sport activities of high level require intensive training and compliance to strict daily routines that might represent a sort of vulnerability toward the onset of full-blown obsessive-compulsive disorder (as well as other disorders) in more fragile individuals. Not suprisingly, sport psychological support experts are increasingly needed.

Insomnia and circadian sleep disorders in ovarian cancer: Evaluation and management of underestimated modifiable factors potentially contributing to morbidity

Ovarian cancer is the leading cause of gynaecological cancer deaths and the seventh most commonly diagnosed cancer among women worldwide, so that, as it is related to substantial and increasing disease burden, the management of ovarian cancer survivors should be a priority. Such issues involve prevention and management of emotional distress, anxiety/depressive symptoms, and maintenance of quality of life from initial diagnosis to post-treatment. Within this framework, sleep disturbances, in particular insomnia, are emerging as modifiable determinants of mental health, also contributing to substantial morbidity among cancer, including ovarian cancer. To this aim we conducted a systematic review according to PRISMA guidelines on prevalence and management of insomnia and circadian sleep disorders in ovarian cancer, while selecting 22 papers. Insomnia was evaluated in ovarian cancer and, while circadian sleep disturbances were poorly assessed in ovarian cancer, insomnia increased from 14% to 60% of patients. Insomnia was associated with cancer-related comorbid conditions such as emotional distress, anxiety/depressive symptoms and low quality of life. Despite this evidence, no studies have been conducted about insomnia treatment in ovarian cancer. The burden of insomnia and circadian sleep disorders in patients with ovarian cancer still needs to be addressed, and requires a call to action for the evaluation and management of these potential modifiable factors that might contribute to ovarian cancer morbidity.

Search for New Phenomena in Final States with Two Leptons and One or No b-Tagged Jets at sqrt[s]=13 TeV Using the ATLAS Detector

A search for new phenomena is presented in final states with two leptons and one or no b-tagged jets. The event selection requires the two leptons to have opposite charge, the same flavor (electrons or muons), and a large invariant mass. The analysis is based on the full run-2 proton-proton collision dataset recorded at a center-of-mass energy of sqrt[s]=13  TeV by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 139  fb^{-1}. No significant deviation from the expected background is observed in the data. Inspired by the B-meson decay anomalies, a four-fermion contact interaction between two quarks (b, s) and two leptons (ee or μμ) is used as a benchmark signal model, which is characterized by the energy scale and coupling, Λ and g_{*}, respectively. Contact interactions with Λ/g_{*} lower than 2.0 (2.4) TeV are excluded for electrons (muons) at the 95% confidence level, still far below the value that is favored by the B-meson decay anomalies. Model-independent limits are set as a function of the minimum dilepton invariant mass, which allow the results to be reinterpreted in various signal scenarios.

Search for Displaced Leptons in sqrt[s]=13 TeV pp Collisions with the ATLAS Detector

A search for charged leptons with large impact parameters using 139  fb^{-1} of sqrt[s]=13  TeV pp collision data from the ATLAS detector at the LHC is presented, addressing a long-standing gap in coverage of possible new physics signatures. Results are consistent with the background prediction. This search provides unique sensitivity to long-lived scalar supersymmetric lepton partners (sleptons). For lifetimes of 0.1 ns, selectron, smuon, and stau masses up to 720, 680, and 340  GeV, respectively, are excluded at 95% confidence level, drastically improving on the previous best limits from LEP.

The Microbiota/Microbiome and the Gut-Brain Axis: How Much Do They Matter in Psychiatry?

The functioning of the central nervous system (CNS) is the result of the constant integration of bidirectional messages between the brain and peripheral organs, together with their connections with the environment. Despite the anatomical separation, gut microbiota, i.e., the microorganisms colonising the gastrointestinal tract, is highly related to the CNS through the so-called "gut-brain axis". The aim of this paper was to review and comment on the current literature on the role of the intestinal microbiota and the gut-brain axis in some common neuropsychiatric conditions. The recent literature indicates that the gut microbiota may affect brain functions through endocrine and metabolic pathways, antibody production and the enteric network while supporting its possible role in the onset and maintenance of several neuropsychiatric disorders, neurodevelopment and neurodegenerative disorders. Alterations in the gut microbiota composition were observed in mood disorders and autism spectrum disorders and, apparently to a lesser extent, even in obsessive-compulsive disorder (OCD) and related conditions, as well as in schizophrenia. Therefore, gut microbiota might represent an interesting field of research for a better understanding of the pathophysiology of common neuropsychiatric disorders and possibly as a target for the development of innovative treatments that some authors have already labelled "psychobiotics".

Early Life Stress and Chronobiological Rhythms Desynchronization: Possible Impact on Mood Symptoms and Suicidal Ideation in Bipolar Disorder

ABSTRACT

The study aimed at investigating the potential impact of early stressful events on the clinical manifestations of bipolar disorder (BD). A sample of 162 adult individuals with BD was assessed using the Structural Clinical Interview for DSM-5, the Beck Depression Inventory-II, the Young Mania Rating Scale, the Early Trauma Inventory Self Report-Short Form, the Biological Rhythms Interview of Assessment in Neuropsychiatry, the Insomnia Severity Index, and the Scale for Suicide Ideation. A significant path coefficient indicated a direct effect of early life stressors on biological rhythms (coeff. = 0.26; p < 0.001) and of biological rhythms on depressive symptoms (coeff. = 0.5; p < 0.001), suicidal risk (coeff. = 0.3; p < 0.001), and insomnia (coeff. = 0.34; p < 0.001). Data suggested that the desynchronization of chronobiological rhythms might be one mediator of the association between early life stress and the severity of mood symptoms/suicidal ideation in BD. Addressing circadian rhythm alterations in subjects exposed to early stressors would help in preventing consequences of those stressors on BD.

Interpersonal Problematic Areas in Liaison Psychiatry: A Feasibility Study

OBJECTIVE

Interpersonal Psychotherapy (IPT) model, with its four problematic areas of grief, deficit, role transition and role dispute, provides a useful frame of reference for a quick case formulation. We aimed at applying the IPT problematic areas assessment in a sample of patients from a liaison psychiatry setting.

METHODS

One-hundred and twenty-nine hospitalized patients of both sexes, aged between 18 and 80 years were interviewed. The 'Interpersonal Problem Areas Rating Scale' (IPARS) was used to detect the interpersonal focuses.

RESULTS

IPARS problematic areas were identified in the 76% of the sample (n=98). Grief and role transition, interpersonal deficits and role disputes were, respectively, the most frequently (43.4 and 42.6%, respectively) and the less frequently described focuses (14 and 11.6%). Moreover, 31 patients (24%) showed no problem areas related to current symptomatology.

CONCLUSIONS

The IPT model has proved to be an easy-to-use tool, able to guide the psychological interview and allowing the collection of information from an interpersonal perspective in a short time, although no specific focuses were detected as related to current psychological distress in around 25% of the sample.

Neuroenhancement: State of the Art and Future Perspectives

Pharmacological neuroenhancement refers to the non-medical use of prescription drugs, alcohol, illegal drugs, or the so-called soft enhancers for the purpose of improving cognition, mood, pro-social behavior, or work and academic performance. This phenomenon is undoubtedly more frequent than previously supposed especially amongst university students. The aim of the present paper was to carefully review and comment on the available literature on neuroenhancement, according to Prisma guidelines. The results showed a great use of all prescribed drugs (benzodiazepines, antidepressants, antipsychotics, nootropic compounds, and especially stimulants) as neuroenhancers amongst healthy subjects, although probably the real prevalence is underestimated. The use of illicit drugs and soft enhancers is similarly quite common. Data on the improvement of cognition by other compounds, such as oxytocin and pheromones, or non-pharmacological techniques, specifically deep brain stimulation and transcranial magnetic stimulation, are still limited. In any case, if it is true that human beings are embedded by the desire to overcome the limits of their intrinsic nature, neuroenhancement practices put into question the concept of authenticity. Therefore, the problem appears quite complex and requires to be deepened and analyzed with no prejudice, although within an ethical conceptual frame.

Longitudinal Flow Decorrelations in Xe+Xe Collisions at sqrt[s_{NN}]=5.44 TeV with the ATLAS Detector

The first measurement of longitudinal decorrelations of harmonic flow amplitudes v_{n} for n=2-4 in Xe+Xe collisions at sqrt[s_{NN}]=5.44  TeV is obtained using 3  μb^{-1} of data with the ATLAS detector at the LHC. The decorrelation signal for v_{3} and v_{4} is found to be nearly independent of collision centrality and transverse momentum (p_{T}) requirements on final-state particles, but for v_{2} a strong centrality and p_{T} dependence is seen. When compared with the results from Pb+Pb collisions at sqrt[s_{NN}]=5.02  TeV, the longitudinal decorrelation signal in midcentral Xe+Xe collisions is found to be larger for v_{2}, but smaller for v_{3}. Current hydrodynamic models reproduce the ratios of the v_{n} measured in Xe+Xe collisions to those in Pb+Pb collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between Xe+Xe and Pb+Pb. The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions.

Search for Dark Matter Produced in Association with a Dark Higgs Boson Decaying into W^{±}W^{∓} or ZZ in Fully Hadronic Final States from sqrt[s]=13 TeV pp Collisions Recorded with the ATLAS Detector

Several extensions of the Standard Model predict the production of dark matter particles at the LHC. An uncharted signature of dark matter particles produced in association with VV=W^{±}W^{∓} or ZZ pairs from a decay of a dark Higgs boson s is searched for using 139  fb^{-1} of pp collisions recorded by the ATLAS detector at a center-of-mass energy of 13 TeV. The s→V(qq[over ¯])V(qq[over ¯]) decays are reconstructed with a novel technique aimed at resolving the dense topology from boosted VV pairs using jets in the calorimeter and tracking information. Dark Higgs scenarios with m_{s}>160  GeV are excluded.

Medium-Induced Modification of Z-Tagged Charged Particle Yields in Pb+Pb Collisions at 5.02 TeV with the ATLAS Detector

The yield of charged particles opposite to a Z boson with large transverse momentum (p_{T}) is measured in 260  pb^{-1} of pp and 1.7  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 Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how their showers are modified as they propagate through the quark-gluon plasma created in Pb+Pb collisions. Compared with pp collisions, charged-particle yields in Pb+Pb collisions show significant modifications as a function of charged-particle p_{T} in a way that depends on event centrality and Z boson p_{T}. The data are compared with a variety of theoretical calculations and provide new information about the medium-induced energy loss of partons in a p_{T} regime difficult to measure through other channels.

Predictors of Suicidal Ideation and Preparatory Behaviors in Individuals With Bipolar Disorder: The Contribution of Chronobiological Dysrhythmicity and Its Association With Hopelessness

OBJECTIVE

To examine the role of chronobiological dysrhythmicity in suicidal ideation and behaviors and its relation with hopelessness.

METHODS

One hundred twenty-seven patients (77 females, mean age of 47.4 ± 12.5 years) with a major depressive episode and bipolar disorder (BD) type I or II (according to Structured Clinical Interview for DSM-5 assessment) were recruited in 2019 and assessed for depressive and manic symptoms (Beck Depression Inventory-II, Young Mania Rating Scale) and with the Biological Rhythms Interview of Assessment in Neuropsychiatry, Beck Hopelessness Scale, and Scale for Suicide Ideation. Univariate regression and mediation analyses were performed.

RESULTS

Forty-one patients (32.3%) showed clinically significant suicidal ideation and were more frequently affected by BD type I (P = .029) with mixed features (P = .022). Compared to nonsuicidal individuals, they had significantly more depressive symptoms (P = .019), higher emotional component of hopelessness (P = .037), and higher dysrhythmicity of sleep (P = .009), activities (P = .048), and social life (P = .019). Passive and active suicidal ideation and suicidal plans were best predicted by dysrhythmicity of sleep and social life. Dysrhythmicity of sleep and social life mediated the direct effect of depressive symptoms on passive and active suicidal ideation and also of active ideation on suicidal plans. The emotional component of hopelessness was related to dysrhythmicity of social life and mediated its effect on suicidal plans (P = .010).

CONCLUSIONS

Chronobiological alterations directly contributed to passive and active suicidal ideation and to suicidal preparation, with a key role of dysrhythmicity of sleep, activities, and social life. Chronobiological alterations also impacted the emotional component of hopelessness, hence indirectly contributing to suicidal ideations and plans. These findings call for the systematic screening of these dysrhythmicity dimensions when considering suicidal risk in individuals with BD.

Observation and Measurement of Forward Proton Scattering in Association with Lepton Pairs Produced via the Photon Fusion Mechanism at ATLAS

The observation of forward proton scattering in association with lepton pairs (e^{+}e^{-}+p or μ^{+}μ^{-}+p) produced via photon fusion is presented. The scattered proton is detected by the ATLAS Forward Proton spectrometer, while the leptons are reconstructed by the central ATLAS detector. Proton-proton collision data recorded in 2017 at a center-of-mass energy of sqrt[s]=13  TeV are analyzed, corresponding to an integrated luminosity of 14.6  fb^{-1}. A total of 57 (123) candidates in the ee+p (μμ+p) final state are selected, allowing the background-only hypothesis to be rejected with a significance exceeding 5 standard deviations in each channel. Proton-tagging techniques are introduced for cross-section measurements in the fiducial detector acceptance, corresponding to σ_{ee+p}=11.0±2.6(stat)±1.2(syst)±0.3(lumi) and σ_{μμ+p}=7.2±1.6(stat)±0.9(syst)±0.2(lumi)  fb in the dielectron and dimuon channel, respectively.

Search for Heavy Resonances Decaying into a Photon and a Hadronically Decaying Higgs Boson in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at sqrt[s]=13  TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139  fb^{-1}. The analysis is performed by reconstructing hadronically decaying Higgs boson (H→bb[over ¯]) candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two b quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-section times branching fraction for narrow spin-1 resonances decaying into a Higgs boson and a photon in the resonance mass range from 0.7 to 4 TeV, cross-section times branching fractions are excluded between 11.6 fb and 0.11 fb at a 95% confidence level.

Search for Higgs Boson Decays into a Z Boson and a Light Hadronically Decaying Resonance Using 13 TeV pp Collision Data from the ATLAS Detector

A search for Higgs boson decays into a Z boson and a light resonance in two-lepton plus jet events is performed, using a pp collision dataset with an integrated luminosity of 139  fb^{-1} collected at sqrt[s]=13  TeV by the ATLAS experiment at the CERN LHC. The resonance considered is a light boson with a mass below 4 GeV from a possible extended scalar sector or a charmonium state. Multivariate discriminants are used for the event selection and for evaluating the mass of the light resonance. No excess of events above the expected background is found. Observed (expected) 95% confidence-level upper limits are set on the Higgs boson production cross section times branching fraction to a Z boson and the signal resonance, with values in the range 17-340 pb (16_{-5}^{+6}-320_{-90}^{+130}  pb) for the different light spin-0 boson mass and branching fraction hypotheses, and with values of 110 and 100 pb (100_{-30}^{+40} and 100_{-30}^{+40}  pb) for the η_{c} and J/ψ hypotheses, respectively.

Dijet Resonance Search with Weak Supervision Using sqrt[s]=13 TeV pp Collisions in the ATLAS Detector

This Letter describes a search for narrowly resonant new physics using a machine-learning anomaly detection procedure that does not rely on signal simulations for developing the analysis selection. Weakly supervised learning is used to train classifiers directly on data to enhance potential signals. The targeted topology is dijet events and the features used for machine learning are the masses of the two jets. The resulting analysis is essentially a three-dimensional search A→BC, for m_{A}∼O(TeV), m_{B},m_{C}∼O(100  GeV) and B, C are reconstructed as large-radius jets, without paying a penalty associated with a large trials factor in the scan of the masses of the two jets. The full run 2 sqrt[s]=13  TeV pp collision dataset of 139  fb^{-1} recorded by the ATLAS detector at the Large Hadron Collider is used for the search. There is no significant evidence of a localized excess in the dijet invariant mass spectrum between 1.8 and 8.2 TeV. Cross-section limits for narrow-width A, B, and C particles vary with m_{A}, m_{B}, and m_{C}. For example, when m_{A}=3  TeV and m_{B}≳200  GeV, a production cross section between 1 and 5 fb is excluded at 95% confidence level, depending on m_{C}. For certain masses, these limits are up to 10 times more sensitive than those obtained by the inclusive dijet search. These results are complementary to the dedicated searches for the case that B and C are standard model bosons.

CP Properties of Higgs Boson Interactions with Top Quarks in the tt[over ¯]H and tH Processes Using H→γγ with the ATLAS Detector

A study of the charge conjugation and parity (CP) properties of the interaction between the Higgs boson and top quarks is presented. Higgs bosons are identified via the diphoton decay channel (H→γγ), and their production in association with a top quark pair (tt[over ¯]H) or single top quark (tH) is studied. The analysis uses 139  fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of sqrt[s]=13  TeV with the ATLAS detector at the Large Hadron Collider. Assuming a CP-even coupling, the tt[over ¯]H process is observed with a significance of 5.2 standard deviations. The measured cross section times H→γγ branching ratio is 1.64_{-0.36}^{+0.38}(stat)_{-0.14}^{+0.17}(sys)  fb, and the measured rate for tt[over ¯]H is 1.43_{-0.31}^{+0.33}(stat)_{-0.15}^{+0.21}(sys) times the Standard Model expectation. The tH production process is not observed and an upper limit on its rate of 12 times the Standard Model expectation is set. A CP-mixing angle greater (less) than 43 (-43)° is excluded at 95% confidence level.

Search for Heavy Higgs Bosons Decaying into Two Tau Leptons with the ATLAS Detector Using pp Collisions at sqrt[s]=13 TeV

A search for heavy neutral Higgs bosons is performed using the LHC Run 2 data, corresponding to an integrated luminosity of 139  fb^{-1} of proton-proton collisions at sqrt[s]=13  TeV recorded with the ATLAS detector. The search for heavy resonances is performed over the mass range 0.2-2.5 TeV for the τ^{+}τ^{-} decay with at least one τ-lepton decaying into final states with hadrons. The data are in good agreement with the background prediction of the standard model. In the M_{h}^{125} scenario of the minimal supersymmetric standard model, values of tanβ>8 and tanβ>21 are excluded at the 95% confidence level for neutral Higgs boson masses of 1.0 and 1.5 TeV, respectively, where tanβ is the ratio of the vacuum expectation values of the two Higgs doublets.