Search

This study explores coherent structures in a swirling turbulent jet. Stationary axisymmetric solutions of the Reynolds–Averaged Navier–Stokes equations at R e = 200 , 000 were obtained using an open source computational fluid dynamics code and the Spalart–Allmaras eddy viscosity model. Then, resolvent analysis with the same eddy viscosity field provided coherent structures of the turbulent fluctuations on the base flow. As in many earlier studies, a large gain separation is identified between the optimal and sub-optimal resolvent modes, permitting a focus on the most amplified response mode and its corresponding optimal forcing. At zero swirl, the results indicate that the jet's coherent response is dominated by axisymmetric ( m = 0 ) structures, which are driven by the usual Kelvin–Helmholtz shear amplification mechanism. However, as swirl is increased, different coherent structures begin to dominate the response. For example, double and triple spiral ( | m | = 2 and | m | = 3 ) modes are identified as the dominant structures when the axial and azimuthal velocity maxima of the base flow are comparable. In this case, distinct co- and counter-rotating | m | = 2 modes experience vastly different degrees of amplification. The physics of this selection process involve several amplification mechanisms contributing simultaneously in different regions of the mode. This is analysed in more detail by comparing the alignment between the wavevector of the dominant response mode and the principal shear direction of the base flow. Additional discussion also considers the development of structures along the exterior of the jet nozzle. [ABSTRACT FROM AUTHOR]

This work aims to provide a more complete understanding of the resonance mechanisms that occur in turbulent jets at high subsonic Mach number, as shown by Towne et al. (J. Fluid Mech., vol. 825, 2017, pp. 1113-1152). Resonance was suggested by that study to exist between upstream- and downstream-travelling guided waves. Five possible resonance mechanisms were postulated, each involving different families of guided waves that reflect in the nozzle exit plane and at a number of downstream turning points. However, that study did not identify which of the five resonance mechanisms underpin the observed spectral peaks. In this work, the waves underpinning resonance are identified via a biorthogonal projection of Large Eddy Simulation data on eigenbases provided by a locally parallel linear stability analysis. Two of the five scenarios postulated by Towne et al. are thus confirmed to exist in the turbulent jet. The reflection-coefficients in the nozzle exit and turning-point planes are, furthermore, identified. Such information is required as input for simplified resonance-modelling strategies such as developed in Jordan et al. (J. Fluid Mech., vol. 853, 2018, pp. 333-358) for jet-edge resonance, and in Mancinelli et al. (Exp. Fluids, vol. 60, 2019, pp. 1-9) for supersonic screech. [ABSTRACT FROM AUTHOR]

Since the Fermi Large Area Telescope launch, a large sample of blazars has been detected in the γ -ray band. One of the important parameters, the variability index (VI), is adopted to quantify the γ -ray blazar variability. The variability of blazars can be affected by the geometric jet structure, accretions, source sizes, or evolutions of particles. In this paper, we compiled a sample of 2250 blazars (792 flat spectrum radio quasars, 1458 BL Lacertae objects) with some physical parameters to investigate the correlations between the VI and beaming effects. The VI shows positive correlations with the Doppler factors, γ -ray luminosities, core dominances, and superluminal motions for both FSRQs and BL Lacs but only holds a positive correlation on polarizations for BL Lacs. The close correlations between VI and the beaming indicators reinforced the previous results that the γ -ray variability is related to the jet, and the VI can be regarded as an effective indicator for the jet beaming effects of Fermi blazars. [ABSTRACT FROM AUTHOR]

We propose a new approach of jet-based event reconstruction that aims to optimally exploit correlations between the products of a hadronic multi-pronged decay across all Lorentz boost regimes. The new approach utilizes clustered small-radius jets as seeds to define unconventional jets, referred to as PAIReD jets. The constituents of these jets are subsequently used as inputs to machine learning-based algorithms to identify the flavor content of the jet. We demonstrate that this approach achieves higher efficiencies in the reconstruction of signal events containing heavy-flavor jets compared to other event reconstruction strategies at all Lorentz boost regimes. Classifiers trained on PAIReD jets also have significantly better background rejections compared to those based on traditional event reconstruction approaches using small-radius jets at low Lorentz boost regimes. The combined effect of a higher signal reconstruction efficiency and better classification performance results in a two to four times stronger rejection of light-flavor jets compared to conventional strategies at low Lorentz-boosts, and rejection rates similar to classifiers based on large-radius multi-pronged jets at high Lorentz-boost regimes. [ABSTRACT FROM AUTHOR]

The azimuthal anisotropy of particles associated with jets (jet particles) at midrapidity is measured for the first time in p-Pb and Pb-Pb collisions at s NN = 5.02 TeV down to transverse momentum (pT) of 0.5 GeV/c and 2 GeV/c, respectively, with ALICE. The results obtained in p-Pb collisions are based on a novel three-particle correlation technique. The azimuthal anisotropy coefficient v2 in high-multiplicity p-Pb collisions is positive, with a significance reaching 6.8σ at low pT, and its magnitude is smaller than in semicentral Pb-Pb collisions. In contrast to the measurements in Pb-Pb collisions, the v2 coefficient is also found independent of pT within uncertainties. Comparisons with the inclusive charged-particle v2 and with AMPT calculations are discussed. The predictions suggest that parton interactions play an important role in generating a non-zero jet-particle v2 in p-Pb collisions, even though they overestimate the reported measurement. These observations shed new insights on the understanding of the origin of the collective behaviour of jet particles in small systems such as p-Pb collisions, and provide significant stringent new constraints to models. [ABSTRACT FROM AUTHOR]

Measurements of inclusive, differential cross-sections for the production of events with missing transverse momentum in association with jets in proton-proton collisions at s = 13 TeV are presented. The measurements are made with the ATLAS detector using an integrated luminosity of 140 fb−1 and include measurements of dijet distributions in a region in which vector-boson fusion processes are enhanced. They are unfolded to correct for detector resolution and efficiency within the fiducial acceptance, and are designed to allow robust comparisons with a wide range of theoretical predictions. A measurement of differential cross sections for the Z → νν process is made. The measurements are generally well-described by Standard Model predictions except for the dijet invariant mass distribution. Auxiliary measurements of the hadronic system recoiling against isolated leptons, and photons, are also made in the same phase space. Ratios between the measured distributions are then derived, to take advantage of cancellations in modelling effects and some of the major systematic uncertainties. These measurements are sensitive to new phenomena, and provide a mechanism to easily set constraints on phenomenological models. To illustrate the robustness of the approach, these ratios are compared with two common Dark Matter models, where the constraints derived from the measurement are comparable to those set by dedicated detector-level searches. [ABSTRACT FROM AUTHOR]

Differential cross-sections for top-quark pair production, inclusively and in association with jets, are measured in pp collisions at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 140 fb−1. The events are selected with one charged lepton (electron or muon) and at least four jets. The differential cross-sections are presented at particle level as functions of several jet observables, including angular correlations, jet transverse momenta and invariant masses of the jets in the final state, which characterise the kinematics and dynamics of the top-antitop system and the hard QCD radiation in the system with associated jets. The typical precision is 5%–15% for the absolute differential cross-sections and 2%–4% for the normalised differential cross-sections. Next-to-leading-order and next-to-next-to-leading-order QCD predictions are found to provide an adequate description of the rate and shape of the jet-angular observables. The description of the transverse momentum and invariant mass observables is improved when next-to-next-to-leading-order QCD corrections are included. [ABSTRACT FROM AUTHOR]

A search for “emerging jets” produced in proton-proton collisions at a center-of-mass energy of 13 TeV is performed using data collected by the CMS experiment corresponding to an integrated luminosity of 138 fb−1. This search examines a hypothetical dark quantum chromodynamics (QCD) sector that couples to the standard model (SM) through a scalar mediator. The scalar mediator decays into an SM quark and a dark sector quark. As the dark sector quark showers and hadronizes, it produces long-lived dark mesons that subsequently decay into SM particles, resulting in a jet, known as an emerging jet, with multiple displaced vertices. This search looks for pair production of the scalar mediator at the LHC, which yields events with two SM jets and two emerging jets at leading order. The results are interpreted using two dark sector models with different flavor structures, and exclude mediator masses up to 1950 (1950) GeV for an unflavored (flavor-aligned) dark QCD model. The unflavored results surpass a previous search for emerging jets by setting the most stringent mediator mass exclusion limits to date, while the flavor-aligned results provide the first direct mediator mass exclusion limits to date. [ABSTRACT FROM AUTHOR]

We analyzed Interface-Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations of a small coronal jet that occurred at the solar west limb on 29 August 2014. The jet source region, a small bright point, was located at an active-region periphery and contained a fan-spine topology with a mini-filament. Our analysis has identified key features and timings that motivated the following interpretation of this event. As the stressed core flux rises, a current sheet forms beneath it; the ensuing reconnection forms a flux rope above a flare arcade. When the rising filament-carrying flux rope reaches the stressed null, it triggers a jet via explosive interchange (breakout) reconnection. During the flux-rope interaction with the external magnetic field, we observed brightening above the filament and within the dome, along with a growing flare arcade. EUV images reveal quasi-periodic ejections throughout the jet duration with a dominant period of 4 minutes, similar to coronal jetlets and larger jets. We conclude that these observations are consistent with the magnetic breakout model for coronal jets. [ABSTRACT FROM AUTHOR]

A measurement is presented of the primary Lund jet plane (LJP) density in inclusive jet production in proton-proton collisions. The analysis uses 138 fb−1 of data collected by the CMS experiment at s = 13 TeV. The LJP, a representation of the phase space of emissions inside jets, is constructed using iterative jet declustering. The transverse momentum kT and the splitting angle ∆R of an emission relative to its emitter are measured at each step of the jet declustering process. The average density of emissions as function of ln(kT/GeV) and ln(R/∆R) is measured for jets with distance parameters R = 0.4 or 0.8, transverse momentum pT> 700 GeV, and rapidity |y| < 1.7. The jet substructure is measured using the charged-particle tracks of the jet. The measured distributions, unfolded to the level of stable charged particles, are compared with theoretical predictions from simulations and with perturbative quantum chromodynamics calculations. Due to the ability of the LJP to factorize physical effects, these measurements can be used to improve different aspects of the physics modeling in event generators. [ABSTRACT FROM AUTHOR]

Measurements of inclusive charged-particle jet production in pp and p-Pb collisions at center-of-mass energy per nucleon-nucleon collision s NN = 5.02 TeV and the corresponding nuclear modification factor R pPb ch jet are presented, using data collected with the ALICE detector at the LHC. Jets are reconstructed in the central rapidity region |ηjet| < 0.5 from charged particles using the anti-kT algorithm with resolution parameters R = 0.2, 0.3, and 0.4. The pT-differential inclusive production cross section of charged-particle jets, as well as the corresponding cross section ratios, are reported for pp and p-Pb collisions in the transverse momentum range 10 < p T , jet ch < 140 GeV/c and 10 < p T , jet ch < 160 GeV/c, respectively, together with the nuclear modification factor R pPb ch jet in the range 10 < p T , jet ch < 140 GeV/c. The analysis extends the pT range of the previously-reported charged-particle jet measurements by the ALICE Collaboration. The nuclear modification factor is found to be consistent with one and independent of the jet resolution parameter with the improved precision of this study, indicating that the possible influence of cold nuclear matter effects on the production cross section of charged-particle jets in p-Pb collisions at s NN = 5.02 TeV is smaller than the current precision. The obtained results are in agreement with other minimum bias jet measurements available for RHIC and LHC energies, and are well reproduced by the NLO perturbative QCD Powheg calculations with parton shower provided by Pythia8 as well as by Jetscape simulations. [ABSTRACT FROM AUTHOR]

A search for R-parity-violating supersymmetry in final states with high jet multiplicity is presented. The search uses 140 fb−1 of proton-proton collision data at s = 13 TeV collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature prompt gluino-pair production decaying directly to three jets each or decaying to two jets and a neutralino which subsequently decays promptly to three jets. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted. Gluinos with masses up to 1800 GeV are excluded when decaying directly to three jets. In the cascade scenario, gluinos with masses up to 2340 GeV are excluded for a neutralino with mass up to 1250 GeV. [ABSTRACT FROM AUTHOR]

Accurate jet charge identification is essential for precise electroweak and flavor measurements at the high-energy frontier. We propose a novel method called the Leading Particle Jet Charge method (LPJC) to determine the jet charge based on information of the leading charged particle. Tested on Z → b b ¯ and Z → c c ¯ samples at center-of-mass energy of 91.2 GeV, the LPJC achieves an effective tagging power ϵeff of 20%/9% for c/b jet, respectively. In combination with the Weighted Jet Charge method (WJC), we develop a Heavy Flavor Jet Charge method (HFJC), which achieves an effective tagging power ϵeff of 39%/20% for c/b jet, respectively. This paper also discusses the dependencies between jet charge identification performance and the fragmentation process of heavy flavor jets, as well as critical detector performances. [ABSTRACT FROM AUTHOR]

The ALICE Collaboration reports a search for jet quenching effects in high-multiplicity (HM) proton-proton collisions at s = 13 TeV, using the semi-inclusive azimuthal-difference distribution ∆φ of charged-particle jets recoiling from a high transverse momentum (high-pT,trig) trigger hadron. Jet quenching may broaden the ∆φ distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a pT,trig-differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. Detailed analysis of these data and simulations show that the azimuthal broadening is due to bias of the HM selection towards events with multiple jets in the final state. The identification of this bias has implications for all jet quenching searches where selection is made on the event activity. [ABSTRACT FROM AUTHOR]

Observations have shown that the chromosphere networks are rich in features with density higher than the ambient atmosphere. To investigate the effect of horizontal density-inhomogeneity on spicules, here we carry out two-dimensional magnetohydrodynamic (MHD) simulations based on the shock scenario. In a gravitationally stratified solar atmosphere, we insert a vertical preexisting density structure (PeDS) that has higher density than the ambient regions, and then we drive a spicule by a velocity pulse at the bottom of the chromosphere. We find a horizontal flow of 2 km s−1 caused by a rarefaction wave that may have a certain material supplement effect for the spicules and a V-shaped shock front in the chromosphere. An interesting feature found in our experiment is that the existence of PeDS leads to the formation of multiple threads in spicules. Their formation results from the larger density, lower transition region, and higher speeds of magnetoacoustic waves in the PeDS than at its outer boundaries. Parameter studies show that multiple threads of a spicule can be more pronounced in cases with wider velocity pulses and a larger internal/external density ratio in the PeDS. Our study shows that the horizontal density-inhomogeneity in the solar atmosphere is an important factor that is responsible for the complexity of a spicule. [ABSTRACT FROM AUTHOR]

The tendency for low-speed solar wind to show greater spatiotemporal variability and different compositional properties from high-speed wind has led to the prevailing idea of a bimodal solar wind, in which fast wind comes from coronal holes and slow wind comes from coronal streamers. We present observational evidence that most of the slow wind originates from small coronal holes or from just inside the boundaries of large holes, with the rest leaking out from coronal streamers and confined to the immediate vicinity of the heliospheric current and plasma sheets. Although this conclusion was suggested earlier by extrapolations of photospheric field maps, additional support comes from (1) observations of slow wind at Earth following the central-meridian passage of small equatorial holes; (2) observations of slow wind with high Alfvénicity at 1 au by Wind, and more recently near the Sun by Parker Solar Probe and Solar Orbiter; and (3) the finding that 80% of the solar wind observed by Helios at 0.3 – 0.4 au during 1974 – 1978 was Alfvénic. We show that compositional properties such as charge-state ratios vary over the solar cycle and may depend on parameters such as the footpoint field strength B 0 , and thus cannot be used alone to distinguish between coronal hole and noncoronal-hole wind. Finally, we note that magnetograms greatly underestimate the amount of small-scale flux emerging inside coronal holes and other unipolar regions. If this rate is taken to be the same as in the quiet Sun, the energy flux density resulting from interchange reconnection with open field lines is on the order of 3 × 10 5 erg cm−2 s−1 ( B 0 /10 G), sufficient to drive the solar wind. The wind speed depends on the rate of flux-tube expansion, with slower expansion leading to more energy deposition at greater heights and faster wind. [ABSTRACT FROM AUTHOR]

For the period of satellite altimetry observation 1993–2018, a comparison was made of estimates of the linear meridional shifts of the jet structure and variations in current intensity in the sector of the Antarctic Circumpolar Current (ACC) south of Africa (10° E–25° W), obtained on the basis of the parameters derived from the module of the absolute dynamic topography (ADT) gradient : directly , module of the velocity of geostrophic current |u| on the ocean surface, half of square of the ADT gradient , and specific kinetic energy . The analysis was carried out by a method developed earlier and refined in this paper using linear regression analysis. It is shown that qualitatively the characters of the meridional shifts (displacement of the curves of these parameters averaged over latitude and for each year) in latitude and the corresponding current intensity variations (i.e., variations in the parameters themselves) over 26-year observations, when calculated through each of the four parameters, turned out to be similar. The same similarity was obtained from the calculations with respect to the ADT scale. Meanwhile, the quantitative differences between calculations for different pairs of parameters can be significant even in the and pair. In quantitative terms, the absolute values of shifts of the jet structure and variations in the intensity of currents in the ACC band in the studied sector of the Southern Ocean generally increase from those linearly dependent on the ADT gradient module to quadratically dependent ones. [ABSTRACT FROM AUTHOR]

Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at s = 13 TeV and p–Pb collisions at s NN = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φ and pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum interval 1 < pT< 4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6 < |∆η| < 1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events. [ABSTRACT FROM AUTHOR]

For the period of satellite altimetry observation 1993–2018, a comparison was made of estimates of the linear meridional shifts of the jet structure and variations in current intensity in the sector of the Antarctic Circumpolar Current (ACC) south of Africa (10° E–25° W), obtained on the basis of the parameters derived from the module of the absolute dynamic topography (ADT) gradient : directly , module of the velocity of geostrophic current |u| on the ocean surface, half of square of the ADT gradient , and specific kinetic energy . The analysis was carried out by a method developed earlier and refined in this paper using linear regression analysis. It is shown that qualitatively the characters of the meridional shifts (displacement of the curves of these parameters averaged over latitude and for each year) in latitude and the corresponding current intensity variations (i.e., variations in the parameters themselves) over 26-year observations, when calculated through each of the four parameters, turned out to be similar. The same similarity was obtained from the calculations with respect to the ADT scale. Meanwhile, the quantitative differences between calculations for different pairs of parameters can be significant even in the and pair. In quantitative terms, the absolute values of shifts of the jet structure and variations in the intensity of currents in the ACC band in the studied sector of the Southern Ocean generally increase from those linearly dependent on the ADT gradient module to quadratically dependent ones. [ABSTRACT FROM AUTHOR]

An optically thin advective accretion disk appears to be indispensable to explain hard-state of black hole sources. Any transport of matter therein is assumed to be led by (modified) -viscosity when the magnetic field is weak. We explore how large scale stronger magnetic field helps in transporting angular momentum in disk and outflow/jet, depending on the field geometry and plasma- parameter, basically by underlying magnetic shear over -viscosity. Interestingly, while above a critical accretion rate the accretion disk turns out to be thermally unstable, in the presence of stronger magnetic fields the disk regains its stability. In the present work, we establish this by numerical simulation based on HARMPI, while the underlying theory was established by one of us earlier. This magnetically arrested advective accretion disk (MA-AAF) in the optically thin regime has far reaching implications including the explanation of ultra-luminous X-ray sources. [ABSTRACT FROM AUTHOR]

A measurement of novel event shapes quantifying the isotropy of collider events is performed in 140 fb−1 of proton-proton collisions with s = 13 TeV centre-of-mass energy recorded with the ATLAS detector at CERN's Large Hadron Collider. These event shapes are defined as the Wasserstein distance between collider events and isotropic reference geometries. This distance is evaluated by solving optimal transport problems, using the 'Energy-Mover's Distance'. Isotropic references with cylindrical and circular symmetries are studied, to probe the symmetries of interest at hadron colliders. The novel event-shape observables defined in this way are infrared- and collinear-safe, have improved dynamic range and have greater sensitivity to isotropic radiation patterns than other event shapes. The measured event-shape variables are corrected for detector effects, and presented in inclusive bins of jet multiplicity and the scalar sum of the two leading jets' transverse momenta. The measured distributions are provided as inputs to future Monte Carlo tuning campaigns and other studies probing fundamental properties of QCD and the production of hadronic final states up to the TeV-scale. [ABSTRACT FROM AUTHOR]

A search for high-mass dimuon resonance production in association with one or more b quark jets is presented. The study uses proton-proton collision data collected with the CMS detector at the LHC corresponding to an integrated luminosity of 138 fb−1 at a center-of-mass energy of 13 TeV. Model-independent limits are derived on the number of signal events with exactly one or more than one b quark jet. Results are also interpreted in a lepton-flavor-universal model with Z′ boson couplings to a bb quark pair (gb), an sb quark pair (gbδbs), and any same-flavor charged lepton (gℓ) or neutrino pair (gν), with |gν| = |gℓ|. For a Z′ boson with a mass m Z ′ = 350 GeV (2 TeV) and |δbs| < 0.25, the majority of the parameter space with 0.0057 < |gℓ| < 0.35 (0.25 < |gℓ| < 0.43) and 0.0079 < |gb| < 0.46 (0.34 < |gb| < 0.57) is excluded at 95% confidence level. Finally, constraints are set on a Z′ model with parameters consistent with low-energy b → sℓℓ measurements. In this scenario, most of the allowed parameter space is excluded for a Z′ boson with 350 < m Z ′ < 500 GeV, while the constraints are less stringent for higher m Z ′ hypotheses. This is the first dedicated search at the LHC for a high-mass dimuon resonance produced in association with multiple b quark jets, and the constraints obtained on models with this signature are the most stringent to date. [ABSTRACT FROM AUTHOR]

Relativistic outflows often exhibit extreme observational characteristics due to beaming effects, which makes measuring their jet power a challenging task. Although the spectral energy distribution (SED) obtained from multi-wavelength data can constrain the physical parameters of these jets, accurately estimating the Doppler factor remains difficult. To address this challenge, we assemble a comprehensive sample containing available SEDs of synchrotron and inverse Compton (IC) components, monochromatic luminosity, and broad-line region (BLR) emissions. We employ a parabolic equation to fit the synchrotron radiation SEDs, constraining jet physical parameters within the framework of a one-zone leptonic model. Our study delves into the jet properties and Doppler factor estimations, yielding the following key findings: (1) The fitting results of SED data for the entire sample reveal normal distributions of jet physical parameters for two subclasses of blazars. (2) Correlation analysis demonstrates that synchrotron peak luminosity exhibits a proportional relationship with both the radio and the γ-ray luminosities. (3) We introduce a novel method for estimating Doppler factors, which uncovers discrepancies between Doppler factors from this work and others from different techniques. [ABSTRACT FROM AUTHOR]

The Antarctic Circumpolar Current plays a key role in the circulation of the Southern Ocean and affects redistribution of heat by the ocean on a global scale. The study of the dynamics and structure of this current becomes especially relevant in a changing climate. The current is well manifested based on the satellite altimetry data, which makes it possible to study the variability of its structure in time and space on different scales. The methods for determining the position of individual fronts of the Antarctic Circumpolar Current based on satellite altimetry data becomes most important in solving these tasks. In this paper, we compare different approaches to the detection of fronts. To do this, the structure of the northernmost branch of the Antarctic Circumpolar Current, the Subantarctic Front, and its spatial and temporal variability have been considered based on the satellite altimetry data from 1993 to 2020 and also on the results of a hydrographic section made onboard the R/V Akademik Mstislav Keldysh across the northern part of the Drake Passage in February 2020. To assess the dynamics of the front, a section of the TOPEX/Poseidon, Jason-1,2,3 satellite altimeter track from Tierra del Fuego to the south, 350 km long, was selected. Criteria are presented for determining the position of the northern and main branches of the Subantarctic Front based on the satellite altimetry data. A long-term trend of shifting the position of the fronts with respect to the previously accepted levels of absolute dynamic topography has been found. It has been established that the accuracy of determining the position of fronts from fixed values of dynamic topography can decrease in time, in particular, due to the variations in the mean sea level. A statistically significant long-term trend in sea level rise in the region of the Subantarctic Front at a rate of 4 mm/year for the northern branch and 2.5 mm/year for the main branch was found. [ABSTRACT FROM AUTHOR]

The interaction of various convection forms with stably stratified intercepting layers in the atmosphere is theoretically investigated. Three different formulations of the problem are considered: (1) a linear problem with given perturbations of temperature and vertical velocity at the lower boundary of a stably stratified medium, (2) penetration of an isolated turbulent thermal into such a medium, and (3) the impact of an intense convective turbulent jet on the intercepting layer. Analytical solutions of the corresponding model problems are found. The possibility of connecting the considered models with signatures of intense convection, in particular, with dome-shaped protrusions above the anvil of a cumulonimbus cloud (or a cluster of a convective system), which represent the intrusion of a powerful updraft into a stably stratified medium, is discussed. [ABSTRACT FROM AUTHOR]

Abstract The path-length dependent parton energy loss within the dense partonic medium created in lead-lead collisions at a nucleon-nucleon center-of-mass energy of s NN = 5.02 TeV is studied by determining the azimuthal anisotropies for dijets with high transverse momentum. The data were collected by the CMS experiment in 2018 and correspond to an integrated luminosity of 1.69 nb−1. For events containing back-to-back jets, correlations in relative azimuthal angle and pseudorapidity (η) between jets and hadrons, and between two hadrons, are constructed. The anisotropies are expressed as the Fourier expansion coefficients vn, n = 2–4 of these azimuthal distributions. The dijet vn values are extracted from long-range (1.5 < |∆η| < 2.5) components of these correlations, which suppresses the background contributions from jet fragmentation processes. Positive dijet v2 values are observed which increase from central to more peripheral events, while the v3 and v4 values are consistent with zero within experimental uncertainties. [ABSTRACT FROM AUTHOR]

Measurements of transverse energy-energy correlations and their associated azimuthal asymmetries in multijet events are presented. The analysis is performed using a data sample corresponding to 139 fb−1 of proton-proton collisions at a centre-of-mass energy of s = 13 TeV, collected with the ATLAS detector at the Large Hadron Collider. The measurements are presented in bins of the scalar sum of the transverse momenta of the two leading jets and unfolded to particle level. They are then compared to next-to-next-to-leading-order perturbative QCD calculations for the first time, which feature a significant reduction in the theoretical uncertainties estimated using variations of the renormalisation and factorisation scales. The agreement between data and theory is good, thus providing a precision test of QCD at large momentum transfers Q. The strong coupling constant αs is extracted as a function of Q, showing a good agreement with the renormalisation group equation and with previous analyses. A simultaneous fit to all transverse energy-energy correlation distributions across different kinematic regions yields a value of α s m Z = 0.1175 ± 0.0006 exp. − 0.0017 + 0.0034 theo. , while the global fit to the asymmetry distributions yields α s m Z = 0.1185 ± 0.0009 exp. − 0.0012 + 0.0025 theo. . [ABSTRACT FROM AUTHOR]

The measurement of the production of charm jets, identified by the presence of a D0 meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of s = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D0 mesons were reconstructed from their hadronic decay D0 → K−π+ and the respective charge conjugate. Jets were reconstructed from D0-meson candidates and charged particles using the anti-kT algorithm, in the jet transverse momentum range 5 < pT,chjet< 50 GeV/c, pseudorapidity |ηjet| < 0.9 − R, and with the jet resolution parameters R = 0.2, 0.4, 0.6. The distribution of the jet momentum fraction carried by a D0 meson along the jet axis z ‖ ch was measured in the range 0.4 < z ‖ ch < 1.0 in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low pT,chjet. Measurements were also done for R = 0.3 at s = 5.02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper. [ABSTRACT FROM AUTHOR]

The discovery of γ - ray emitting Seyfert galaxies has opened a new unified scheme of active galactic nuclei (AGN) in which jetted Seyfert galaxies are viewed as young counterparts of radio loud AGN. In this paper, we investigate the relationship between gamma-ray (γ - ray) properties of jetted Seyfert galaxies and those of traditionally radio galaxies, radio quasars and BL Lac objects. Results show that jetted Seyfert galaxies appear as low luminosity tail of the radio loud AGNs on the luminosity redshift (Lγ – z) plane, indicating an evolutionary link between them. Nevertheless, narrow-line Seyfert galaxies (NLS1s) do not share similar characteristics with Seyfert galaxies as they possess higher luminosities and redshift than Seyfert galaxies, suggestive that NLS1s are more evolved sources. Analyses of γ – ray and radio core-dominance show that for each subclass of jetted AGN, the beaming angle is wider for radio than for γ - ray emissions. While Seyferts and radio galaxies, on average, have similar low inclination to the line of sight, NLS1 objects have orientations similar to quasars and BL Lacs. There is a significant correlation (r ~ 0.7) between the γ - ray core dominance and γ - ray luminosity. The results are consistent with the revised unification scheme and suggests that NLS1s are highly beamed sources whose parent populations can be found among the regular Seyferts and/or radio galaxies [ABSTRACT FROM AUTHOR]

The paper describes a method for analyzing the seasonal variability of the structure of the gradient field of the absolute dynamic topography (ADT) based on satellite altimetry data. This structure is understood as alternation in the meridional direction of zones of increased values of the ADT gradient modulus and zones of their lower values, i.e. jets and inter-jet gaps. The technique uses linear and harmonic regression analyses and makes it possible to calculate the amplitudes and phases of stationary harmonic oscillations that approximate seasonal variations in the meridional shift of the structure of the ADT gradient field and in the absolute values of the ADT gradient, as well as to estimate the calculation error. This technique was used to perform corresponding calculations for the Antarctic Circumpolar Current (ACC) band south of Africa (from 10° W to 25° E). In particular, the amplitude of the seasonal variations of the meridional shift of the ADT gradient field for the ACC as a whole was 0.009 ± 0.013° of latitude with a maximum northward shift in December. At the same time, there are zones within the ACC band where this amplitude reaches 0.12°, 0.16°, and 0.28° of latitude. The amplitude of the variations of the shift of the indicated field with respect to the scale of the ADT itself within the ACC band at different scale values is 0.6–2.5 cm. It is shown that this variations are mainly due to the seasonal variability of the ADT at geographic points. The amplitude of the seasonal variations of the ADT gradient modulus both in latitude and in relation the ADT scale increases from 1 × 10–3 cm/km in the central part of the ACC to 6–7 × 10–3 cm/km at the southern and northern peripheries. [ABSTRACT FROM AUTHOR]

Assuming that the first adiabatic invariant for radiating particles in relativistic jets is conserved, we investigate the change in brightness temperature along the jet axis. We show that in this case the observed break in the dependence of the brightness temperature on the distance to the "central engine" can be explained. [ABSTRACT FROM AUTHOR]

We present the first survey of quiet Sun features observed in hard X-rays (HXRs), using the Nuclear Spectroscopic Telescope ARray (NuSTAR), a HXR focusing optics telescope. The recent solar minimum, combined with NuSTAR's high sensitivity, has presented a unique opportunity to perform the first HXR imaging spectroscopy on a range of features in the quiet Sun. By studying the HXR emission of these features, we can detect or constrain the presence of high temperature (> 5 MK) or non-thermal sources, to help understand how they relate to larger, more energetic solar phenomena, and determine their contribution to heating the solar atmosphere. We report on several features observed in the 28 September 2018 NuSTAR full-disk quiet Sun mosaics, the first of the NuSTAR quiet Sun observing campaigns, which mostly include steady features of X-ray bright points and an emerging flux region, which later evolved into an active region, as well as a short-lived jet. We find that the features' HXR spectra are well fitted with isothermal models with temperatures ranging between 2.0 – 3.2 MK. Combining the NuSTAR data with softer X-ray emission from Hinode/XRT and EUV from SDO/AIA, we recover the differential emission measures, confirming little significant emission above 4 MK. The NuSTAR HXR spectra allow us to constrain the possible non-thermal emission that would still be consistent with a null HXR detection. We found that for only one of the features (the jet) was there a potential non-thermal upper limit capable of powering the heating observed. However, even here, the non-thermal electron distribution had to be very steep (effectively mono-energetic) with a low energy cut-off between 3 – 4 keV. [ABSTRACT FROM AUTHOR]

The radio quasar NVSS J141922−083830 (J1419−0838) was initially classified as an uncategorised blazar-type object, following its detection in the γ -ray band with the Fermi space telescope. Later, using multi-waveband observations and modeling, its was found to be a flat-spectrum radio quasar (FSRQ). However, its radio emission has never been discussed in depth in the literature. Here we present a detailed analysis on the radio properties of J1419−0838 using archival interferometric imaging data at pc and kpc scales. We conclude that the flux density variations, the flat radio spectrum, the compact nature of the quasar structure at all scales, and the relativistic Doppler enhancement of the radio emission all support the previous classification as an FSRQ. We also investigated the short- and long-term mid-infrared (MIR) light curve of the quasar based on observations by the Wide-field Infrared Survey Explorer satellite, and found that there is significant variability on time-scales of days as well as years. Comparison of the MIR light curve to the times of previously reported γ -ray and optical flares shows no clear correlation between the events at different wavebands. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the dispersivity of an aerosol obtained using two injector devices arranged differently mutually are presented. The dependences of the numerical and volume concentrations of droplets in the aerosol formed in the course of variation of the relative angle of attack of jets on the size of droplets are presented. The limiting initial distances between droplets in the aerosol, at which the sizes of the droplets practically do not change during their free fall, are determined. Based on the research results, recommendations were formulated to ensure predictable distributions of the droplets of liquid in a gaseous medium at different distances from the fire zone. [ABSTRACT FROM AUTHOR]

Accurately measuring the properties of the Higgs boson is one of the core physics objectives of the Circular Electron Positron Collider (CEPC). As a Higgs factory, the CEPC is expected to operate at a centre-of-mass energy of 240 GeV, deliver an integrated luminosity of 5.6 ab−1, and produce one million Higgs bosons according to the CEPC Conceptual Design Report (CDR). Combining measurements of the ℓ+ℓ−H, ν ν ¯ H , and q q ¯ H channels, we conclude that the signal strength of H → b b ¯ / c c ¯ / gg can be measured with a relative accuracy (relative statistical uncertainty only) of 0.27%/4.03%/1.56%. Extrapolating to the recently released TDR operating parameters corresponding to the integrated luminosity of 20 ab−1, the relative accuracy of H → b b ¯ / c c ¯ / gg signal strength is 0.14%/2.13%/0.82% (relative statistical uncertainty only). We analyze the dependence of the expected accuracies on the critical detector performances: Color Singlet Identification (CSI) for the q q ¯ H channel and flavor tagging for both ν ν ¯ H and q q ¯ H channels. Compared to the baseline CEPC detector performance, ideal flavor tagging can increase the H → b b ¯ / c c ¯ / gg signal strength accuracy by 2%/63%/13% in the ν ν ¯ H channel and 35%/122%/181% in the q q ¯ H channel. A strong dependence between the CSI performance and anticipated accuracies in q q ¯ H channel is identified. The relevant systematic uncertainties are also discussed in this paper. [ABSTRACT FROM AUTHOR]

The Sun Watcher with Active Pixels and Image Processing (SWAP) instrument onboard ESA's PRoject for On Board Autonomy 2 (PROBA2) has provided the first uncompressed, high-cadence, continuous, large field-of-view observations of the extended extreme-ultraviolet (EUV) corona for over a complete solar cycle. It has helped shape our understanding of this previously understudied region, and pioneered research into the middle corona. In this article, we present a review of all publications that have utilized these observations to explore the extended EUV corona, highlighting the unique contributions made by SWAP. The review is broadly divided into three main sections of SWAP-based studies about: i) long-lived phenomena, such as streamers, pseudo-streamers, and coronal fans; ii) dynamic phenomena, such as eruptions, jets, EUV waves, and shocks; iii) coronal EUV emission generation. We also highlight SWAP's imaging capabilities, techniques that have been applied to observations to enhance the off-limb observations and its legacy. [ABSTRACT FROM AUTHOR]

Jets produced in high-energy heavy-ion collisions are modified compared to those in proton-proton collisions due to their interaction with the deconfined, strongly-coupled quark-gluon plasma (QGP). In this work, we employ machine learning techniques to identify important features that distinguish jets produced in heavy-ion collisions from jets produced in proton-proton collisions. We formulate the problem using binary classification and focus on leveraging machine learning in ways that inform theoretical calculations of jet modification: (i) we quantify the information content in terms of Infrared Collinear (IRC)-safety and in terms of hard vs. soft emissions, (ii) we identify optimally discriminating observables that are in principle calculable in perturbative QCD, and (iii) we assess the information loss due to the heavy-ion underlying event and background subtraction algorithms. We illustrate our methodology using Monte Carlo event generators, where we find that important information about jet quenching is contained not only in hard splittings but also in soft emissions and IRC-unsafe physics inside the jet. This information appears to be significantly reduced by the presence of the underlying event. We discuss the implications of this for the prospect of using jet quenching to extract properties of the QGP. Since the training labels are exactly known, this methodology can be used directly on experimental data without reliance on modeling. We outline a proposal for how such an experimental analysis can be carried out, and how it can guide future measurements. [ABSTRACT FROM AUTHOR]

Scour downstream of smooth and rough rigid aprons under wall jets has been studied experimentally. Effect of apron roughness on scour has been investigated, and quantification of reduction in the scour depth due to rough apron has been performed. Characteristics of velocity and turbulence over smooth and rough aprons as well as within the scour hole have been analyzed to study the behavior of the jet and its interaction with the rough apron. Results show that there is a significant reduction in the equilibrium scour depth due to roughness. A maximum of 82.8% and a minimum of 31.1% reduction in the equilibrium scour depth was observed due to inducing roughness over the rigid apron. Velocity characteristics establish the cause of reduction in the equilibrium scour depth, which is due to reduction in the erosive capacity of the jet as it moves over the rough apron. The potential core of the jet gets consumed at a much lesser length due to roughness over the apron than over a smooth apron, as the boundary layer develops at a smaller distance. Further, it was observed that it takes a smaller length for the flow to get fully developed under the rough apron as compared with the smooth apron. Based on the results of the present analysis, recommendation can be made for use of roughness over the apron to restrict scour due to wall jets. [ABSTRACT FROM AUTHOR]

Continuing Article I, we revisit challenging events previously identified by different authors, whose analysis led to conclusions about various mechanisms of the shock-wave excitation. Here, we reconsider four events that involved fan-spine coronal configurations with a null-point topology (NPT). The presence of Type-II radio bursts in all events as well as extreme-ultraviolet disturbances (EUV waves) observed in three events evidence the presence of shock waves, whereas no coronal mass ejections (CMEs) were detected in most events. One idea proposed to explain the observations was the shock-wave excitation by the straightening of a postreconnection kinked loop. The Type-II burst in another event appeared in association with a compact flare with a high thermal pressure that looked to be in favor of a flare-generated blast wave. One event was associated with a possible pseudo-CME. All of these challenging events have been reconciled in terms of an impulsively excited piston shock. CME-less filament eruptions in NPT configurations appear to represent a distinct category of events responsible for some of the observed shock waves. [ABSTRACT FROM AUTHOR]

In this paper, we give comprehensive analyses for event shape observables in electron-positron annihilation by using the Principle of Maximum Conformality (PMC) which is a rigorous scale-setting method to eliminate the renormalization scheme and scale ambiguities in perturbative QCD predictions. Conventionally the renormalization scale and theoretical uncertainties in event shape observables are often evaluated by setting the scale to the center-of-mass energy s . The event shape distributions using this conventional scale setting are plagued by the large renormalization scale uncertainty and underestimate the experimental data. Moreover, since the renormalization scale is simply fixed to the center-of-mass energy s , only one value of the coupling αs at the single scale s can be extracted. In contrast, the PMC renormalization scales are determined by absorbing the nonconformal β contributions that govern the behavior of the running coupling via the Renormalization Group Equation (RGE). The resulting PMC scales change with event shape kinematics, reflecting the virtuality of the underlying quark and gluon subprocess. The PMC scales thus yield the correct physical behavior of the scale and the PMC predictions agree with precise event shape distributions measured at the LEP experiment. More importantly, we can precisely determine the running of the QCD coupling constant αs(Q2) over a wide range of Q2 in perturbative domain from event shape distributions measured at a single center-of-mass energy s . [ABSTRACT FROM AUTHOR]

We present an analysis of the X-ray data obtained in the period of flaring activity of SS 433 in July and August 2018, during which the brightest radio flares over the entire history of its observations were detected at frequencies 2–5 GHz based on data from the RATAN-600 radio telescope. The Swift/XRT and NICER space observatory data were obtained immediately during the radio flares within the program of Target of Opportunity (ToO) observations. The Chandra/HETGS observations and the additional quasi-simultaneous NICER calibration observations were carried out in the active phase of the system between the radio intensity peaks. We show that during the peak radio fluxes the emission lines of the relativistic jets are detected with confidence in the X-ray spectrum, while their basic parameters remain stable, which can serve as evidence for the absence of significant violations in the jet collimation and acceleration mechanisms. At the same time, the X-ray intensity of the jets at these moments drops by a factor of 4–5 and is restored to its normal values within days. Anomalous deviations of the jet line positions from the predictions of the kinematic model were found in the period of activity and during the radio flares. Our modeling of the Chandra spectra using the emission model of baryonic jets in SS 433 point to rapid changes in the structure of the wind from the supercritical disk that partially blocks the emission from the hottest regions of the jets. The set of these factors points to a possible connection of the emergence of radio flares and active states of SS 433 with perturbations in the rate of mass transfer and outflow in the system. [ABSTRACT FROM AUTHOR]

The multi-wavelength non-thermal emission from the relativistic AGN jets exhibits flux variability ranging from a very short timescale of minutes, hours to long-timescale of months and years. These magnetically driven jets are subject to several instabilities during their propagation in space. Magneto-hydrodynamical (MHD) instabilities are the most probable candidate responsible for magnetic energy dissipation that could prompt jet radiation and particle acceleration. In this work, we have investigated the impact of the pitch profile and magnetization value on developing the current-driven (CD) kink instability in the moderately relativistic regime of Lorentz factor 5. To achieve this, we simulate a 3D plasma column, a representative section of an AGN jet. From our analysis, a stalled growth of the instability is apparent with a lower magnetization value due to the variable Alfvénic nature of the flow. In addition, we have also investigated the impact of constant pitch profile on the dynamical evolution of the plasma column and the corresponding emission features. [ABSTRACT FROM AUTHOR]

Extending the Standard Model with right-handed neutrinos (RHNs) is well motivated by the observation of neutrino oscillations. In the type-I seesaw model, the RHNs interact with the SM particles via tiny mixings with the active neutrinos, which makes their discovery in the laboratory, and in particular at collider experiments in general challenging. In this work we instead consider an extension of the seesaw model with RHNs with the addition of a leptoquark (LQ), and employ a non-minimal production mechanism of the RHN via LQ decay, which is unsuppressed by neutrino mixing. We focus on relatively light RHN with mass O (10) GeV and LQ with mass 1.0 TeV, and explore the discovery prospect of the RHN at the proposed Large Hadron electron Collider. In the considered mass range and with the given interaction strength, the RHN is long lived and, due to it stemming from the LQ decay, it is also heavily boosted, resulting in collimated decay products. The unique signature under investigation is thus a displaced fat jet. We use kinematic variables to separate signal from background, and demonstrate that the ratio variables with respect to energy/number of displaced and prompt tracks are useful handles in the identification of displaced decays of the RHN. We also show that employing a positron beam provides order of magnitude enhancement in the detection prospect of this signature. [ABSTRACT FROM AUTHOR]

The first measurements of energy spectra and substructure of anti-kT jets in hadronic Z0 decays in e+e− collisions are presented. The archived e+e− annihilation data at a center-of-mass energy of 91.2 GeV were collected with the ALEPH detector at LEP in 1994. In addition to inclusive jet and leading dijet energy spectra, various jet substructure observables are analyzed as a function of jet energy which includes groomed and ungroomed jet mass to jet energy ratios, groomed momentum sharing, and groomed jet radius. The results are compared with perturbative QCD calculations and predictions from the Sherpa, Herwig v7.1.5, Pythia6, Pythia8 and Pyquen event generators. The jet energy spectra agree with perturbative QCD calculations which include the treatment of logarithms of the jet radius and threshold logarithms. None of the event generators give a fully satisfactory description of the data. [ABSTRACT FROM AUTHOR]

The observed characteristics of the spectral and photometric variability of SS 433 are discussed based on the data for 2018–2021 and compared with earlier results. The change in the orbital period that we discovered earlier according to -photometry is confirmed by the data in the -filter, although with less accuracy. In the observation interval from 1978 to 2021, secular changes are not observed either in the stationary or moving H lines. However, there are breaks in the precession phase up to days, which appear at time scales less than 1 year and disappear in 2–3 years. [ABSTRACT FROM AUTHOR]

We introduce a simple procedure that resolves the long-standing question of how to account for single-logarithmic spin-correlation effects in parton showers not just in the collinear limit, but also in the soft wide-angle limit, at leading colour. We discuss its implementation in the context of the PanScales family of parton showers, where it complements our earlier treatment of the purely collinear spin correlations. Comparisons to fixed-order matrix elements help validate our approach up to third order in the strong coupling, and an appendix demonstrates the small size of residual subleading-colour effects. To help probe wide-angle soft spin correlation effects, we introduce a new declustering-based non-global spin-sensitive observable, the first of its kind. Our showers provide a reference for its single-logarithmic resummation. The work in this paper represents the last step required for final-state massless showers to satisfy the broad PanScales next-to-leading logarithmic accuracy goals. [ABSTRACT FROM AUTHOR]

Non-global QCD observables are characterised by a sensitivity to the full angular distribution of soft radiation emitted coherently in hard scattering processes. This complexity poses a challenge to their all-order resummation, that was formulated at the leading-logarithmic order about two decades ago. In this article we present a solution to the long-standing problem of their resummation beyond this order, and carry out the first complete next-to-leading logarithmic calculation for non-global observables. This is achieved by solving numerically the recently derived set of non-linear differential equations which describe the evolution of soft radiation in the planar, large-Nc limit. As a case study we address the calculation of the transverse energy distribution in the interjet rapidity region in e+e−→ dijet production. The calculation is performed by means of an algorithm that we formulate in the language of jet-calculus generating functionals, which also makes the resummation technique applicable to more general non-global problems, such as those that arise in hadronic collisions. We find that NLL corrections are substantial and their inclusion leads to a significant reduction of the perturbative scale uncertainties for these observables. The computer code used in the calculations is made publicly available. [ABSTRACT FROM AUTHOR]

Anomaly detection relies on designing a score to determine whether a particular event is uncharacteristic of a given background distribution. One way to define a score is to use autoencoders, which rely on the ability to reconstruct certain types of data (background) but not others (signals). In this paper, we study some challenges associated with variational autoencoders, such as the dependence on hyperparameters and the metric used, in the context of anomalous signal (top and W) jets in a QCD background. We find that the hyperparameter choices strongly affect the network performance and that the optimal parameters for one signal are non-optimal for another. In exploring the networks, we uncover a connection between the latent space of a variational autoencoder trained using mean-squared-error and the optimal transport distances within the dataset. We then show that optimal transport distances to representative events in the background dataset can be used directly for anomaly detection, with performance comparable to the autoencoders. Whether using autoencoders or optimal transport distances for anomaly detection, we find that the choices that best represent the background are not necessarily best for signal identification. These challenges with unsupervised anomaly detection bolster the case for additional exploration of semi-supervised or alternative approaches. [ABSTRACT FROM AUTHOR]

We discuss the measurement of gluon transverse momentum distribution (TMD) in dijet and heavy hadron pair (HHP) production in semi-inclusive deep inelastic scattering. The factorization of these processes in position space shows the appearance of a specific new soft factor matrix element on top of angular and complex valued anomalous dimensions. We show in detail how these features can be treated consistently and we discuss a scale prescription for the evolution kernel of the dijet soft function. As a result we obtain phenomenological predictions for unpolarized and angular modulated cross-sections for the electron-ion collider (EIC) using current available information on unpolarized TMD. [ABSTRACT FROM AUTHOR]

The selection of jets in heavy-ion collisions based on their pT after jet quenching is known to bias towards jets that lost little energy in the quark-gluon plasma. In this work, we study and quantify the impact of this selection bias on jet substructure observables so as to isolate effects caused by the modification of the substructure of jets by quenching. We do so at first in a simplified Monte Carlo study in which it is possible to identify the same jet before and after quenching. We show explicitly that jets selected based on their quenched (i.e. observable) pT have substantially smaller fractional energy loss than those selected based on the pT that they would have had in the absence of any quenching. This selection bias has a large impact on jet structure and substructure observables. As an example, we consider the angular separation ∆R of the hardest splitting in each jet, and find that the ∆R distribution of the (biased) sample of jets selected based upon their quenched pT is almost unmodified by quenching. In contrast, quenching causes dramatic modifications to the ∆R distribution of a sample of jets selected based upon their unquenched pT, with a significant enhancement at larger ∆R coming from the soft particles originating from the wake of the jet in the quark-gluon plasma. The jets which contribute to this enhancement are those which have lost the most energy and which were, therefore, left out of the sample selected after quenching. In a more realistic study, we then show that the same qualitative effects can all be observed in Z+jet events. Selecting jets in such events based on either the jet pT or the Z-boson pT provides an experimentally accessible way to quantify the effects of selection biases in jet observables and separate them from the modification of jet substructure caused by quenching. Selecting Z+jet events based upon the jet pT yields a ∆R distribution that appears almost unmodified whereas selecting Z+jet events based upon the Z-boson pT reveals a significant modification to the ∆R-distribution caused by quenching, once again arising from the wakes of those jets that lose more energy. [ABSTRACT FROM AUTHOR]