Fragmentation of jets containing a prompt J/ψ meson in PbPb and pp collisions at sNN= 5.02 TeV

arXiv preprint arXiv:2402.14786

We study how the recent experimental results constrain the gauge sectors of U(1) extensions of the standard model using a novel representation of the parameter space. We determine the bounds on the mixing angle between the massive gauge bosons, or equivalently, the new gauge coupling as a function of the mass of the new neutral gauge boson in the approximate range GeV/. We consider the most stringent bounds obtained from direct searches for the . We also exhibit the allowed parameter space by comparing the predicted and measured values of the parameter and those of the mass of the boson. Finally, we discuss the prospects of searches at future colliders.

The European Physical Journal. C, Particles and Fields

The measurement of Z boson production is presented as a method to determine the integrated luminosity of CMS data sets. The analysis uses proton–proton collision data, recorded by the CMS experiment at the CERN LHC in 2017 at a center-of-mass energy of 13\(\,\text {Te\hspace {-. 08em} V}\). Events with Z bosons decaying into a pair of muons are selected. The total number of Z bosons produced in a fiducial volume is determined, together with the identification efficiencies and correlations from the same data set, in small intervals of 20 of integrated luminosity, thus facilitating the efficiency and rate measurement as a function of time and instantaneous luminosity. Using the ratio of the efficiency-corrected numbers of Z bosons, the precisely measured integrated luminosity of one data set is used to determine the luminosity of another. For the first time, a full quantitative uncertainty analysis of the use of Z …

Osteoarthritis and Cartilage

Purpose (the aim of the study): Approximately 1 in 2 people with a history of significant knee injury develop symptomatic radiographic osteoarthritis (OA), so called post-traumatic osteoarthritis (PTOA) of the knee. The impacts of PTOA are well-described, but little is known about the genetic risk of developing OA after knee injury and whether this differs from idiopathic OA (iOA). Knowledge of genetic variants associated with PTOA would improve our understanding of this subgroup of disease. Our aim is to identify genome-wide significant signals associated with PTOA of the knee. Here we present initial work to a) establish optimal methods, including definition of phenotypes and relevant analyses; b) assess cohort feasibility to apply eligibility criteria to identify sufficient numbers; c) generate power and sample size calculations for a discovery GWAS meta-analysis, and d) create an analysis plan.Methods: As part of the …

Journal of Advanced Instrumentation in Science

The MUTOMCA (MUon TOMography for shielding CAsks) project investigates the suitability of muon tomography for the reverification of spent fuel casks. Spent fuel casks are stored, for decades, in dedicated locations and are under constant surveillance by international agencies through unattended monitoring equipment. In the hypothetical case that these instruments would temporarily fail, thus leading to a loss of Continuity of Knowledge (CoK), a reverification of the spent fuel enclosed in self-shielding casks would be required. The reverification is particularly challenging for conventional nondestructive assay (NDA) methods since thick-walled spent fuel casks considerably attenuate the radiation emitted by the spent fuel. On the other hand, inspectorates need a high degree of assurance on the amounts of nuclear material stored in those casks. With the aim of proving the ability of muon tomography to detect a diversion of fuel assemblies in closed spent fuel casks, an experimental apparatus was designed, developed, constructed, and commissioned. The detectors were used during the first months of 2023, in a field trial at a dry storage facility in Germany to examine CASTOR® V/19 casks. Preliminary results are presented along with the potentials and drawbacks of the experimental apparatus.

European Journal of Surgical Oncology

BackgroundBoth anastomotic leak (AL) and conduit necrosis (CN) after oesophagectomy are associated with high morbidity and mortality. Therefore, the identification of preoperative, modifiable risk factors is desirable. The aim of this study was to generate a risk scoring model for AL and CN after oesophagectomy.MethodsPatients undergoing curative resection for oesophageal cancer were identified from the international Oesophagogastric Anastomosis Audit (OGAA) from April 2018–December 2018. Definitions for AL and CN were those set out by the Oesophageal Complications Consensus Group. Univariate and multivariate analyses were performed to identify risk factors for both AL and CN. A risk score was then produced for both AL and CN using the derivation set, then internally validated using the validation set.ResultsThis study included 2247 oesophagectomies across 137 hospitals in 41 countries. The AL …

Computing demands for large scientific experiments, such as the CMS experiment at the CERN LHC, will increase dramatically in the next decades. To complement the future performance increases of software running on central processing units (CPUs), explorations of coprocessor usage in data processing hold great potential and interest. Coprocessors are a class of computer processors that supplement CPUs, often improving the execution of certain functions due to architectural design choices. We explore the approach of Services for Optimized Network Inference on Coprocessors (SONIC) and study the deployment of this as-a-service approach in large-scale data processing. In the studies, we take a data processing workflow of the CMS experiment and run the main workflow on CPUs, while offloading several machine learning (ML) inference tasks onto either remote or local coprocessors, specifically graphics processing units (GPUs). With experiments performed at Google Cloud, the Purdue Tier-2 computing center, and combinations of the two, we demonstrate the acceleration of these ML algorithms individually on coprocessors and the corresponding throughput improvement for the entire workflow. This approach can be easily generalized to different types of coprocessors and deployed on local CPUs without decreasing the throughput performance. We emphasize that the SONIC approach enables high coprocessor usage and enables the portability to run workflows on different types of coprocessors.

Journal of Statistical Theory and Practice

In this paper, we introduce a hybrid model that combines the elements of an RRT model and the Paillier encryption protocol which is common in computer science. The goal of this work is to leverage the strengths of both methods to come up with a more efficient sensitive data collection technique that produces a more efficient estimator as compared to Warner’s indirect question model.

Physical Review Letters

A search for dark matter in events with a displaced nonresonant muon pair and missing transverse momentum is presented. The analysis is performed using an integrated luminosity of 138 fb− 1 of proton-proton (p p) collision data at a center-of-mass energy of 13 TeV produced by the LHC in 2016–2018. No significant excess over the predicted backgrounds is observed. Upper limits are set on the product of the inelastic dark matter production cross section σ (p p→ A′→ χ 1 χ 2) and the decay branching fraction B (χ 2→ χ 1 μ+ μ−), where A′ is a dark photon and χ 1 and χ 2 are states in the dark sector with near mass degeneracy. This is the first dedicated collider search for inelastic dark matter.

Journal of Orthopaedics

IntroductionWith the increasing incidence of total knee arthroplasty (TKA), there is an expected rise in rate of periprosthetic fractures in the coming years. It is unclear how the outcomes of patients with distal femur fractures (DFF) and a total knee arthroplasty compare to patients of the same age group with native knees (NK).Materials and methodsA retrospective review was completed for distal femur fractures treated with surgical fixation from January 2019–March 2021. We excluded patients <50 years old, non-ambulatory patients, revision surgeries, and patients with less than 90 days of follow-up. A chart review was performed to collect age, gender, BMI, smoking status, American Society of Anesthesiology (ASA) classification, fracture types, fixation method, time to full weight bearing, and complications. Comparisons between the TKA vs Native knee groups were performed using t-test, chi-square, and Fisher's exact …

Journal of High Energy Physics

The polarization of τ leptons is measured using leptonic and hadronic τ lepton decays in Z→ τ+ τ− events in proton-proton collisions at= 13 TeV recorded by CMS at the CERN LHC with an integrated luminosity of 36.3 fb− 1. The measured τ− lepton polarization at the Z boson mass pole is=− 0.144±0.006 (stat)±0.014 (syst)=− 0.144±0.015, in good agreement with the measurement of the τ lepton asymmetry parameter of A τ= 0.1439±0.0043= at LEP. The τ lepton polarization depends on the ratio of the vector to axial-vector couplings of the τ leptons in the neutral current expression, and thus on the effective weak mixing angle sin 2, independently of the Z boson production mechanism. The obtained value sin 2= 0.2319±0. 0008 (stat)±0. 0018 (syst)= 0. 2319±0. 0019 is in good agreement with measurements at e+ e− colliders.

arXiv preprint arXiv:2310.03844

The identification of prompt and isolated muons, as well as muons from heavy-flavour hadron decays, is an important task. We developed two multivariate techniques to provide highly efficient identification for muons with transverse momentum greater than 10\GeV. One provides a continuous variable as an alternative to a cut-based identification selection and offers a better discrimination power against misidentified muons. The other one selects prompt and isolated muons by using isolation requirements to reduce the contamination from nonprompt muons arising in heavy-flavour hadron decays. Both algorithms are developed using 59.7 fb of proton-proton collisions data at a centre-of-mass energy of = 13 TeV collected in 2018 with the CMS experiment at the CERN LHC.

arXiv preprint arXiv:2403.10341

A search is presented for the decay of the 125 GeV Higgs boson (H) to a pair of new light pseudoscalar bosons (a), followed by the prompt decay of each a boson to a bottom quark-antiquark pair, H aa . The analysis is performed using a data sample of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb. To reduce the background from standard model processes, the search requires the Higgs boson to be produced in association with a leptonically decaying W or Z boson. The analysis probes the production of new light bosons in a 15 60 GeV mass range. Assuming the standard model predictions for the Higgs boson production cross sections for pp WH and ZH, model independent upper limits at 95% confidence level are derived for the branching fraction (H aa ). The combined WH and ZH observed upper limit on the branching fraction ranges from 1.10 for 20 GeV to 0.36 for 60 GeV, complementing other measurements in the , and bb ( ,) channels.

arXiv preprint arXiv:2403.15518

The operation and performance of the Compact Muon Solenoid (CMS) electromagnetic calorimeter (ECAL) are presented, based on data collected in pp collisions at = 13 TeV at the CERN LHC, in the years from 2015 to 2018 (LHC Run 2), corresponding to an integrated luminosity of 151 fb. The CMS ECAL is a scintillating lead-tungstate crystal calorimeter, with a silicon strip preshower detector in the forward region that provides precise measurements of the energy and the time-of-arrival of electrons and photons. The successful operation of the ECAL is crucial for a broad range of physics goals, ranging from observing the Higgs boson and measuring its properties, to other standard model measurements and searches for new phenomena. Precise calibration, alignment, and monitoring of the ECAL response are important ingredients to achieve these goals. To face the challenges posed by the higher luminosity, which characterized the operation of the LHC in Run 2, the procedures established during the 2011-2012 run of the LHC have been revisited and new methods have been developed for the energy measurement and for the ECAL calibration. The energy resolution of the calorimeter, for electrons from Z boson decays reaching the ECAL without significant loss of energy by bremsstrahlung, was better than 1.8%, 3.0%, and 4.5% in the $\lvert\eta\rvert$ intervals [0.0,0.8], [0.8,1.5], [1.5, 2.5], respectively. This resulting performance is similar to that achieved during Run 1 in 2011-2012, in spite of the more severe running conditions.

The Lancet Diabetes & Endocrinology

BackgroundSodium–glucose co-transporter-2 (SGLT2) inhibitors reduce progression of chronic kidney disease and the risk of cardiovascular morbidity and mortality in a wide range of patients. However, their effects on kidney disease progression in some patients with chronic kidney disease are unclear because few clinical kidney outcomes occurred among such patients in the completed trials. In particular, some guidelines stratify their level of recommendation about who should be treated with SGLT2 inhibitors based on diabetes status and albuminuria. We aimed to assess the effects of empagliflozin on progression of chronic kidney disease both overall and among specific types of participants in the EMPA-KIDNEY trial.MethodsEMPA-KIDNEY, a randomised, controlled, phase 3 trial, was conducted at 241 centres in eight countries (Canada, China, Germany, Italy, Japan, Malaysia, the UK, and the USA), and …

Physical Review D

The second Gravitational-Wave Transient Catalog, GWTC-2, reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15∶ 00 UTC and 1 October 2019 15∶ 00 UTC. Here, we present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the probability of astrophysical origin for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have a …

Physical Review D

The second Gravitational-Wave Transient Catalog, GWTC-2, reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15∶ 00 UTC and 1 October 2019 15∶ 00 UTC. Here, we present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the probability of astrophysical origin for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have a …

Physics Letters B

Measurements of the elliptic (v 2) and triangular (v 3) azimuthal anisotropy coefficients are presented for Image 1 mesons produced in Image 2 hadron decays (nonprompt Image 1 mesons) in lead-lead collisions at s NN= 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt Image 1 mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb− 1. Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt Image 1 mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of v 2 and v 3 and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt Image 1 mesons. The results are …

The European physical journal. C, Particles and fields

The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton–proton collisions at a center-of-mass energy of 13 Te V. The analysis uses a data sample corresponding to a total integrated luminosity of 138 fb-1 collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The W+ c production cross section and the cross section ratio R c±= σ (W++ c)/σ (W-+ c) are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in R c±= 0.950±0.005 (stat)±0.010 (syst). The …

A search is described for the production of a pair of bottom-type vector-like quarks (B VLQs) with mass greater than 1000 GeV. Each B VLQ decays into a b quark and a Higgs boson, a b quark and a Z boson, or a t quark and a W boson. This analysis considers both fully hadronic final states and those containing a charged lepton pair from a Z boson decay. The products of the H bb boson decay and of the hadronic Z or W boson decays can be resolved as two distinct jets or merged into a single jet, so the final states are classified by the number of reconstructed jets. The analysis uses data corresponding to an integrated luminosity of 138 fb collected in proton-proton collisions at = 13 TeV with the CMS detector at the LHC from 2016 to 2018. No excess over the expected background is observed. Lower limits are set on the B VLQ mass at 95% confidence level. These depend on the B VLQ branching fractions and are 1570 and 1540 GeV for 100% B bH and 100% B bZ, respectively. In most cases, the mass limits obtained exceed previous limits by at least 100 GeV.

EAI Endorsed Transactions on Internet of Things

The reliability of fuel cells during testing is crucial for their development on test benches. For the development of fuel cells on test benches, it is essential to maintain their dependability during testing. It is only possible for the alarm module of the control software to identify the most serious failures because of the large operating parameter range of a fuel cell. This study presents a novel approach to monitoring fuel cell stacks during testing that relies on machine learning to ensure precise outcomes. The use of machine learning to track fuel cell operating variables can achieve improvements in performance, economy, and reliability. ML enables intelligent decision-making for efficient fuel cell operation in varied and dynamic environments through the power of data analytics and pattern recognition. Evaluating the performance of fuel cells is the first and most important step in establishing their reliability and durability. This introduces methods that track the fuel cell's performance using digital twins and clustering-based approaches to monitor the test bench's operating circumstances. The only way to detect the rate of accelerated degradation in the test scenarios is by using the digital twin LSTM-NN model that is used to evaluate fuel cell performance. The proposed methods demonstrate their ability to detect discrepancies that the state-of-the-art test bench monitoring system overlooked, using real-world test data. An automated monitoring method can be used at a testing facility to accurately track the operation of fuel cells.

Physics Letters B

A search for non-resonant Higgs boson pair production, as predicted by the Standard Model, is presented, where one of the Higgs bosons decays via the H→ b b channel and the other via one of the H→ W W⁎/Z Z⁎/τ τ channels. The analysis selection requires events to have at least two b-tagged jets and exactly two leptons (electrons or muons) with opposite electric charge in the final state. Candidate events consistent with Higgs boson pair production are selected using a multi-class neural network discriminant. The analysis uses 139 fb− 1 of pp collision data recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. An observed (expected) upper limit of 1.2 (0.9− 0.3+ 0.4) pb is set on the non-resonant Higgs boson pair production cross-section at 95% confidence level, which is equivalent to 40 (29− 9+ 14) times the value predicted in the Standard Model.

Physics Letters B

We study different entropies for coherent states representing the geometry of spherically symmetric compact systems. We show that the thermodynamic entropy reproduces the Bekenstein-Hawking result in the presence of thermal modes at the Hawking temperature if the object is a black hole and saturates the Bekenstein bound for more general compact objects. We also analyse the information entropy of the quantum coherent state without radiation and find further support against the singular Schwarzschild geometry.

Physics Letters B

Semi-visible jets, with a significant contribution to the event's missing transverse momentum, can arise in strongly interacting dark sectors. This results in an event topology where one of the jets can be aligned with the direction of the missing transverse momentum. The first search for semi-visible jets produced via a t-channel mediator exchange is presented. The analysis uses proton-proton collisions with an integrated luminosity of 139 fb−1 and a centre-of-mass energy of 13 TeV, collected with the ATLAS detector during the Run 2 of the LHC. No excess over Standard Model predictions is observed. Assuming a coupling strength of unity between the mediator, a Standard Model quark and a dark quark, mediator masses up to 2.7 TeV are excluded at the 95% confidence level. Upper limits on the coupling strength are also derived.

Physics Letters B

The inclusive top-quark-pair production cross section σ t t¯ and its ratio to the Z-boson production cross section have been measured in proton–proton collisions at s= 13.6 TeV, using 29 fb− 1 of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and b-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be σ t t¯= 850±3 (stat.)±18 (syst.)±20 (lumi.) pb. The ratio of the t t¯ and the Z-boson production cross sections is also measured, where the Z-boson contribution is determined for inclusive e+ e− and μ+ μ− events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the t t¯ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, R t t¯/Z= 1.145±0.003 (stat.)±0.021 (syst.)±0.002 (lumi.) is consistent …

Physics Letters B

This letter presents a search for narrow, high-mass resonances in the Zγ final state with the Z boson decaying into a pair of electrons or muons. The s= 13 TeV pp collision data were recorded by the ATLAS detector at the CERN Large Hadron Collider and have an integrated luminosity of 140 fb− 1. The data are found to be in agreement with the Standard Model background expectation. Upper limits are set on the resonance production cross section times the decay branching ratio into Zγ. For spin-0 resonances produced via gluon–gluon fusion, the observed limits at 95% confidence level vary between 65.5 fb and 0.6 fb, while for spin-2 resonances produced via gluon–gluon fusion (or quark–antiquark initial states) limits vary between 77.4 (76.1) fb and 0.6 (0.5) fb, for the mass range from 220 GeV to 3400 GeV.

Physics Letters B

This letter reports the observation of W (ℓ ν) γ γ production in proton-proton collisions. This measurement uses the full Run 2 sample of events recorded at a center-of-mass energy of s= 13 TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb− 1. Events with a leptonically-decaying W boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of 5.6 standard deviations. The inclusive fiducial production cross section of W (e ν) γ γ and W (μ ν) γ γ events is measured to be σ fid= 13.8±1.1 (stat)+ 2.1− 2.0 (syst)±0.1 (lumi) fb, in agreement with the Standard Model prediction.

Physics Letters B

A search for non-resonant Higgs boson pair production, as predicted by the Standard Model, is presented, where one of the Higgs bosons decays via the H→ b b channel and the other via one of the H→ W W⁎/Z Z⁎/τ τ channels. The analysis selection requires events to have at least two b-tagged jets and exactly two leptons (electrons or muons) with opposite electric charge in the final state. Candidate events consistent with Higgs boson pair production are selected using a multi-class neural network discriminant. The analysis uses 139 fb− 1 of pp collision data recorded at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. An observed (expected) upper limit of 1.2 (0.9− 0.3+ 0.4) pb is set on the non-resonant Higgs boson pair production cross-section at 95% confidence level, which is equivalent to 40 (29− 9+ 14) times the value predicted in the Standard Model.

Physics Letters B

A search for the decay of the Higgs boson to a Z boson and a light, pseudoscalar particle, a, decaying respectively to two leptons and to two photons is reported. The search uses the full LHC Run 2 proton–proton collision data at s= 13 TeV, corresponding to 139 fb− 1 collected by the ATLAS detector. This is one of the first searches for this specific decay mode of the Higgs boson, and it probes unexplored parameter space in models with axion-like particles (ALPs) and extended scalar sectors. The mass of the a particle is assumed to be in the range 0.1–33 GeV. The data are analysed in two categories: a merged category where the photons from the a decay are reconstructed in the ATLAS calorimeter as a single cluster, and a resolved category in which two separate photons are detected. The main background processes are from Standard Model Z boson production in association with photons or jets. The data are in …

Physics Letters B

Measurements of the elliptic (v 2) and triangular (v 3) azimuthal anisotropy coefficients are presented for Image 1 mesons produced in Image 2 hadron decays (nonprompt Image 1 mesons) in lead-lead collisions at s NN= 5.02 TeV. The results are compared with previously published charm meson anisotropies measured using prompt Image 1 mesons. The data were collected with the CMS detector in 2018 with an integrated luminosity of 0.58 nb− 1. Azimuthal anisotropy is sensitive to the interactions of quarks with the hot and dense medium created in heavy ion collisions. Comparing results for prompt and nonprompt Image 1 mesons can assist in understanding the mass dependence of these interactions. The nonprompt results show lower magnitudes of v 2 and v 3 and weaker dependences on the meson transverse momentum and collision centrality than those found for prompt Image 1 mesons. The results are …

Physics Letters B

We investigate the relation between quantum nonlocality and gravity at the astrophysical scale, both in the classical and quantum regimes. Considering a gedanken experiment involving particle pairs orbiting in the strong gravitational field of ultra-compact objects, we find that the violation of Bell inequality acquires an angular modulation factor that strongly depends on the nature of the gravitational source. We show how such gravitationally-induced modulation of quantum nonlocality readily discriminates between black holes (both classical and inclusive of quantum corrections) and string fuzzballs, i.e., the true quantum description of ultra-compact objects according to string theory. These findings promote Bell nonlocality as a potentially key tool in putting quantum gravity to the test.

Physics Letters B

In this Letter, the first measurement of the inelastic cross section for antitriton–nucleus interactions is reported, covering the momentum range of 0.8≤ p< 2.4 GeV/c. The measurement is carried out using data recorded with the ALICE detector in pp and Pb–Pb collisions at a centre-of-mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector material serves as an absorber for antitriton nuclei. The raw yield of (anti) triton nuclei measured with the ALICE apparatus is compared to the results from detailed ALICE simulations based on the Image 1 toolkit for the propagation of (anti) particles through matter, allowing one to quantify the inelastic interaction probability in the detector material. This analysis complements the measurement of the inelastic cross section of antinuclei up to A= 3 carried out by the ALICE Collaboration, and demonstrates the feasibility of the study of the isospin dependence of …

Physics Letters B

The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb–Pb collision data at a center-of-mass energy per nucleon–nucleon collision s NN= 5.02 TeV. Charged-particle jets are reconstructed using the anti-k T algorithm with resolution parameters R= 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and R= 0.2, 0.4, 0.6 in central (0–10%), semi-central (30–50%), and peripheral (60–80%) Pb–Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet p T≥ 40 GeV/c at R= 0.6 in central Pb–Pb collisions. This is an important step for discriminating different models of jet quenching in the quark–gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and …

Physics Letters B

The measurements of the inclusive J/ψ yield at midrapidity (| y|< 0. 9) and forward rapidity (2.5< y< 4) in Pb–Pb collisions at s NN= 5.02 TeV with the ALICE detector at the LHC are reported. The inclusive J/ψ production yields and nuclear modification factors, R AA, are measured as a function of the collision centrality, J/ψ transverse momentum (p T), and rapidity. The J/ψ average transverse momentum and squared transverse momentum (< p T> and< p T 2>) are evaluated as a function of the centrality at midrapidity. Compared to the previous ALICE publications, here the entire Pb–Pb collisions dataset collected during the LHC Run 2 is used, which improves the precision of the measurements and extends the p T coverage. The p T-integrated R AA shows a hint of an increasing trend towards unity from semicentral to central collisions at midrapidity, while it is flat at forward rapidity. The p T-differential R AA shows a …

Physics Letters B

The first measurements of skewness and kurtosis of mean transverse momentum (< p T>) fluctuations are reported in Pb–Pb collisions at s NN= 5.02 TeV, Xe–Xe collisions at s NN= 5.44 TeV and pp collisions at s= 5.02 TeV using the ALICE detector. The measurements are carried out as a function of system size< d N ch/d η>| η|< 0.5 1/3, using charged particles with transverse momentum (p T) and pseudorapidity (η), in the range 0.2< p T< 3.0 GeV/c and| η|< 0.8, respectively. In Pb–Pb and Xe–Xe collisions, positive skewness is observed in the fluctuations of< p T> for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum …

Physics Letters B

The pseudorapidity dependence of elliptic (v 2), triangular (v 3), and quadrangular (v 4) flow coefficients of charged particles measured in Pb–Pb collisions at a centre-of-mass energy per nucleon pair of s NN= 5.02 TeV and in Xe–Xe collisions at s NN= 5.44 TeV with ALICE at the LHC are presented. The measurements are performed in the pseudorapidity range− 3.5< η< 5 for various centrality intervals using two-and multi-particle cumulants with the subevent method. The flow probability density function (pdf) is studied with the ratio of flow coefficient v 2 calculated with four-and two-particle cumulant, and suggests that the variance of flow pdf is independent of pseudorapidity. The decorrelation of the flow vector in the longitudinal direction is probed using two-particle correlations. The results measured with respect to different reference regions in pseudorapidity exhibit differences, argued to be a result of saturating …

Physics Letters B

The magnetic dipole moments (μ) of 209 Tl g (N= 128) and 207 Tl m (N= 126) have been measured for the first time using the in-source laser resonance-ionization spectroscopy technique with the Laser Ion Source and Trap (LIST) at ISOLDE (CERN). The application of the LIST suppresses the usually overwhelming background of the isobaric francium isotopes and allows access to heavy thallium isotopes with A⩾ 207. The self-consistent theory of finite Fermi systems based on the energy density functional by Fayans et al. well describes the N dependence of μ for 1/2+ thallium ground states, as well as μ for the 11/2− isomeric states in europium, gold and thallium isotopes. The inclusion of particle-vibration coupling leads to a better agreement between the theory and experiment for μ (Tl g, I π= 1/2+). It is shown that beyond mean-field contributions to μ cannot be neglected at least for thallium isotopes with I π= 1/2+.

Physics Letters B

Semi-visible jets, with a significant contribution to the event's missing transverse momentum, can arise in strongly interacting dark sectors. This results in an event topology where one of the jets can be aligned with the direction of the missing transverse momentum. The first search for semi-visible jets produced via a t-channel mediator exchange is presented. The analysis uses proton-proton collisions with an integrated luminosity of 139 fb−1 and a centre-of-mass energy of 13 TeV, collected with the ATLAS detector during the Run 2 of the LHC. No excess over Standard Model predictions is observed. Assuming a coupling strength of unity between the mediator, a Standard Model quark and a dark quark, mediator masses up to 2.7 TeV are excluded at the 95% confidence level. Upper limits on the coupling strength are also derived.

Physics Letters B

The inclusive top-quark-pair production cross section σ t t¯ and its ratio to the Z-boson production cross section have been measured in proton–proton collisions at s= 13.6 TeV, using 29 fb− 1 of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and b-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be σ t t¯= 850±3 (stat.)±18 (syst.)±20 (lumi.) pb. The ratio of the t t¯ and the Z-boson production cross sections is also measured, where the Z-boson contribution is determined for inclusive e+ e− and μ+ μ− events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the t t¯ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, R t t¯/Z= 1.145±0.003 (stat.)±0.021 (syst.)±0.002 (lumi.) is consistent …

Physics Letters B

This letter presents a search for narrow, high-mass resonances in the Zγ final state with the Z boson decaying into a pair of electrons or muons. The s= 13 TeV pp collision data were recorded by the ATLAS detector at the CERN Large Hadron Collider and have an integrated luminosity of 140 fb− 1. The data are found to be in agreement with the Standard Model background expectation. Upper limits are set on the resonance production cross section times the decay branching ratio into Zγ. For spin-0 resonances produced via gluon–gluon fusion, the observed limits at 95% confidence level vary between 65.5 fb and 0.6 fb, while for spin-2 resonances produced via gluon–gluon fusion (or quark–antiquark initial states) limits vary between 77.4 (76.1) fb and 0.6 (0.5) fb, for the mass range from 220 GeV to 3400 GeV.

Physics Letters B

This letter reports the observation of W (ℓ ν) γ γ production in proton-proton collisions. This measurement uses the full Run 2 sample of events recorded at a center-of-mass energy of s= 13 TeV by the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb− 1. Events with a leptonically-decaying W boson and at least two photons are considered. The background-only hypothesis is rejected with an observed and expected significance of 5.6 standard deviations. The inclusive fiducial production cross section of W (e ν) γ γ and W (μ ν) γ γ events is measured to be σ fid= 13.8±1.1 (stat)+ 2.1− 2.0 (syst)±0.1 (lumi) fb, in agreement with the Standard Model prediction.