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Classifying hadronic objects in ATLAS with ML/AI algorithms
No full textHadronic object reconstruction & classification is one of the most promising settings for cutting-edge machine learning and artificial intelligence algorithms at the LHC. In this contribution, highlights of ML/AI applications by ATLAS to QCD and boosted-object identification, MET reconstruction and other tasks will be presented
Energy–energy correlators in charm-tagged jets in proton–proton collisions at TeV
No full textIn this letter, we present the first measurement of the energy–energy correlator (EEC) in charm-tagged jets from proton–proton (pp) collisions at TeV. EECs probe the structure of QCD radiation, providing a unique test of mass-dependent effects in parton showers involving a charm quark and offering a distinct view into non-perturbative phenomena, including the hadronization process. The EEC is measured for charm-tagged jets and flavor-untagged (inclusive) jets with transverse momenta of GeV/, where charm-quark mass effects are significant. We observe a significant suppression of the EEC amplitude in charm jets compared to inclusive ones, consistent with the expected suppression of radiation from massive quarks – a fundamental prediction of QCD. Despite the significant amplitude difference, the observed peak positions of the charm and inclusive-jet EEC are similar, indicating a complex interplay between Casimir factor (differentiating quark and gluon jets), and quark-mass (dead-cone) effects in the QCD parton shower and subsequent hadronization effects. Comparisons with next-to-leading order calculations and various Monte Carlo event generators reveal the sensitivity of this observable to both mass effects in the parton shower and hadronization process. These results provide new constraints on theoretical models of heavy-quark jets and offer insights into the parton-to-hadron transition in QCD.In this letter, we present the first measurement of the energy-energy correlator (EEC) in charm-tagged jets from proton-proton (pp) collisions at TeV. EECs probe the structure of QCD radiation, providing a unique test of mass-dependent effects in parton showers involving a charm quark and offering a distinct view into non-perturbative phenomena, including the hadronization process. The EEC is measured for charm-tagged jets and flavor-untagged (inclusive) jets with transverse momenta of GeV/, where charm-quark mass effects are significant. We observe a significant suppression of the EEC amplitude in charm jets compared to inclusive ones, consistent with the expected suppression of radiation from massive quarks -- a fundamental prediction of QCD. Despite the significant amplitude difference, the observed peak positions of the charm and inclusive-jet EEC are similar, indicating a complex interplay between Casimir factor (differentiating quark and gluon jets), and quark-mass (dead-cone) effects in the QCD parton shower as well as subsequent hadronization effects. Comparisons with next-to-leading order calculations and various Monte Carlo event generators reveal the sensitivity of this observable to both mass effects in the parton shower and hadronization process. These results provide new constraints on theoretical models of heavy-quark jets and offer insights into the parton-to-hadron transition in QCD
Event-activity dependence of heavy-flavor production at the ALICE experiment
No full textHeavy-flavor production at the LHC offers valuable tests of quantum-chromodynamics calculations, owing to the large masses of heavy quarks. Measurements of charm production as a function of event activity reveal new features of charm production and fragmentation, providing insights into the interplay between soft and hard processes. In addition, charm production in heavy-ion collisions addresses flavor-dependent quark transport properties in both hot and cold nuclear matter, helping to clarify the roles of coalescence and fragmentation in heavy-flavor hadron formation. This contribution summarizes recent measurements from the ALICE experiment on charm production as a function of charged-particle multiplicity in collisions at various energies, including the measurements of charm baryon-to-meson production yield ratios in , –Pb, and Pb–Pb collisions. New results on production in collisions as a function of the transverse spherocity of the event are also presented.Heavy-flavor production at the LHC offers valuable tests of quantum-chromodynamics calculations, owing to the large masses of heavy quarks. Measurements of charm production as a function of event activity reveal new features of charm production and fragmentation, providing insights to the interplay between soft and hard processes. In addition, charm production in heavy-ion collisions addresses flavor-dependent quark transport properties in both hot and cold nuclear matter, helping to clarify the roles of coalescence and fragmentation in heavy-flavor hadron formation. This contribution summarizes recent measurements from the ALICE experiment on charm production as a function of charged-particle multiplicity in pp collisions at various energies, including the measurements of charm baryon-to-meson production yield ratios in pp, p--Pb and Pb--Pb collisions. New results on production in pp collisions as a function of the transverse spherocity of the event, as well as of the transverse event-activity classifier , are also presented
Physics case for low- QCD studies at FCC-ee
No full textMeasurements of hadronic final states in collisions at centre-of-mass (CM) energies below the Z peak can notably extend the FCC-ee physics reach in terms of precision quantum chromodynamics (QCD) studies. Hadronic final states can be studied over a range of hadronic energies \sqrt{s_\mathrm{had}} \approx 20\mbox{--}80\,\mathrm{GeV} by exploiting events with hard initial- and final-state QED radiation (ISR/FSR) during the high-luminosity Z-pole run, as well as in dedicated short (about one month long) runs at CM energies and . Using realistic estimates and fast detector simulations, we show that data samples of about hadronic events can be collected at the FCC-ee at each of the low-CM-energy points. Such datasets can be exploited in a variety of precision QCD measurements, including studies of light-, heavy-quark and gluon jet properties, hadronic event shapes, fragmentation functions, and nonperturbative dynamics. This will offer valuable insights into strong interaction physics, complementing data from nominal FCC-ee runs at higher center-of-mass energies, and
Metal Foil Detectors assembly for the beam and background monitoring in the LHCb experiment
No full textAfter an upgrade in 2019–2021, the LHCb experiment istaking data in Run 3 (2022–2026) with an instantaneous luminosityof proton-proton collisions of2×10 cms. This articlepresents the Radiation Monitoring System (RMS-R3) for controllingthe beam and background conditions at LHCb. It runs continuouslyduring the detector's operation, and independently of the main LHCbdata acquisition. Its design is based on robust and radiation-hardMetal Foil Detector technology. The RMS-R3 monitors theinstantaneous luminosity and its evolution. The analysis of theRMS-R3 Run 3 data demonstrates its linear response with a highreproducibility in a five orders of magnitude dynamic range ofluminosity over a long period of operation.After an upgrade in 2019--2021, the LHCb experiment is taking data in Run 3 (2022--2026) with an instantaneous luminosity of proton-proton collisions of cms. This article presents the Radiation Monitoring System (RMS-R3) for controlling the beam and background conditions at LHCb. It runs continuously during the detector's operation, and independently of the main LHCb data acquisition. Its design is based on robust and radiation-hard Metal Foil Detector technology. The RMS-R3 monitors the instantaneous luminosity and its evolution. The analysis of the RMS-R3 Run 3 data demonstrates its linear response with a high reproducibility in a five orders of magnitude dynamic range of luminosity over a long period of operation
U(1) Gauging, Continuous TQFTs, and Higher Symmetry Structures
No full textQuantum field theories can exhibit various generalized symmetry structures, among which higher-group symmetries and non-invertible symmetry defects are particularly prominent. In this work, we explore a new general scenario in which these two structures are intertwined. This phenomenon arises in four dimensions when gauging one of multiple 0-form symmetries in the presence of mixed 't Hooft anomalies. We illustrate this with two distinct models that flow to an IR gapless phase and a gapped phase, respectively, and examine how this symmetry structure manifests in each case. Additionally, we investigate a five-dimensional model where a similar structure exists intrinsically. Our main tool is a symmetry TQFT in one higher dimension, formulated using non-compact gauge fields and having infinitely many topological operators. We carefully determine its boundary conditions and provide a detailed discussion on various dressing choices for its bulk topological operators.Quantum field theories can exhibit various generalized symmetry structures, among which higher-group symmetries and non-invertible symmetry defects are particularly prominent. In this work, we explore a new general scenario in which these two structures are intertwined. This phenomenon arises in four dimensions when gauging one of multiple 0-form symmetries in the presence of mixed 't Hooft anomalies. We illustrate this with two distinct models that flow to an IR gapless phase and a gapped phase, respectively, and examine how this symmetry structure manifests in each case. Additionally, we investigate a five-dimensional model where a similar structure exists intrinsically. Our main tool is a symmetry TQFT in one higher dimension, formulated using non-compact gauge fields and having infinitely many topological operators. We carefully determine its boundary conditions and provide a detailed discussion on various dressing choices for its bulk topological operators
