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GELATO: A Generic Event-Level Anomalous Trigger Option for ATLAS
No full textThe absence of beyond-Standard-Model physics discoveries at the LHC suggests that new physics may evade conventional trigger strategies. The existing ATLAS triggers are required to control data collection rates with high energy thresholds and target signal topologies specific to only certain models. Unsupervised machine learning enables the use of anomaly detection, presenting a unique model-agnostic way to search for anomalous signatures that deviate from Standard Model expectations. We present a new trigger sequence using fast anomaly detection algorithms in both the hardware and software triggers implemented for ATLAS Run-3 data-taking. The design and performance of the triggers will be described along with their integration and commissioning strategy with an emphasis on rate stability and operational robustness. First results from analysis of data collected through this new trigger stream, focusing on validating the trigger response, will be shown. This first anomaly detection trigger for ATLAS provides a framework for future machine learning implementations in the trigger system. The approach offers potential for novel sensitivity to a broad spectrum of new physics signatures in Run-3 and beyond
On the nature and charge state of the X-Defect, a radiation-induced Silicon defect with field-enhanced charge carrier emission
No full textThe elusive X-Defect, a defect found in low-resistivity p-type Silicon after irradiation, observed as a low-temperature shoulder of the BiOi defect (Boron-interstitial-Oxygen-interstitial complex) in Thermally Stimulated Current (TSC) measurements, was investigated to determine its properties, matching them with those of a previously identified defect. Through a combination of TSC, Deep-Level Transient Spectroscopy (DLTS), Difference-DLTS (DDLTS), numerical simulations of field-enhanced charge carrier emissions in TSC measurements and a comparison to literature, the X-Defect was identified as the singly positively charged Silicon di-vacancy V2(+/0). This assignment is supported by an agreement in activation energy, capture cross-section, trap type and charge emission process, as well as simulations comparing the effects of phonon-assisted tunnelling (PAT) and Poole–Frenkel (PF) mechanisms on TSC spectra. DDTLS measurements revealed a quadratic dependence of the activation energy on the electric field strength, confirming PAT as the prevailing mechanism over PF in the case of the radiation-induced X-Defect. Assigning the X-Defect to an electrically neutral defect in the space charge region resolves previous contradictions regarding its lack of impact on the effective doping concentration Neff. •X-Defect is the Silicon di-vacancy in the donor state V2(+/0).•X-Defect does not impact Neff.•Phonon-assisted tunnelling process was observed for the V2(+/0).•The zero-field activation energy of the V2(+/0) is (0.1962 ± 0.0007)eV.The elusive X-Defect, a defect found in low-resistivity -type Silicon after irradiation, observed as a low-temperature shoulder of the defect (Boron-interstitial-Oxygen-interstitial complex) in Thermally Stimulated Current (TSC) measurements, was investigated to determine its properties, matching them with those of a previously identified defect. Through a combination of TSC, Deep-Level Transient Spectroscopy (DLTS), Difference-DLTS (DDLTS), numerical simulations of field-enhanced charge carrier emissions in TSC measurements and a comparison to literature, the X-Defect was identified as the singly positively charged Silicon di-vacancy . This assignment is supported by an agreement in activation energy, capture cross-section, trap type and charge emission process, as well as simulations comparing the effects of phonon-assisted tunnelling (PAT) and Poole-Frenkel (PF) mechanisms on TSC spectra. DDTLS measurements revealed a quadratic dependence of the activation energy on the electric field strength, confirming PAT as the prevailing mechanism over PF in the case of the radiation-induced X-Defect. Assigning the X-Defect to an electrically neutral defect in the space charge region resolves previous contradictions regarding its deficiency in impacting on the effective doping concentration
Energy Deposition and Characterization of Single-Event Upset and Latch-Up Cross Sections With 14 MeV and Thermal Neutrons
No full textSingle-event latch-up (SEL) cross sections of static random access memory (SRAM) at high energy (100–200 MeV)
are generally not reproducible with 14-MeV neutrons, differently to single-event upset (SEU) cross sections. We explain
this phenomenon through Monte Carlo simulations, analyzing neutron–silicon interactions and the indirect energy deposition
in sensitive volumes (SVs) resembling the two mechanisms, showing that the former approach is not sufficient to explain
how the energy is deposited. The SRAMs were characterized in monoenergetic and spallation facilities and their Monte Carlo
model was validated using various particle beams. Additionally, the contribution of individual ions to the SEU and SEL cross
sections is quantified, demonstrating the distinct impact of these ions in the two mechanisms. For instance, alpha particles play
a significant role in triggering SEUs, while they hardly induce SELs. This is related to the energy released by the ion in
correlation with its range and the size of the SV. Finally, the models are validated against thermal neutrons, and the SEL
sensitivity is also investigated, demonstrating the absence of SEL for devices with a linear energy transfer (LET) threshold above
2 MeV · cm2/m
New physics with the gravitational waves form early universe phase transitions
No full textIn many BSM physics scenarios the early Universe went through a first-order phase transition. The gravitational waves produced in the transition may be observable in future gravitational wave detectors, such as the LISA gravitational wave space mission. In order to fully utilize the observations the gravitational wave production must be calculatedto high precision. In this talk I discuss the importance of numerical simulations in the analysis of phase transitions, from BSM thermodynamics, critical bubble nucleation and the subsequent hydrodynamic evolution and gravitational wave production.
This talk is part of the Advancing gravitational wave predictions from cosmological first-order phase transitions </p
Advancing gravitational wave predictions from cosmological first-order phase transitions
No full textThe dynamics of of the electroweak phase transition has profound implications for cosmology and particle physics, and is governed by the density perturbations generated by the expanding bubble. A precise determination of this dynamics, and in particular of the bubble wall velocity, is crucial to assess the experimental signatures of the transition. In this talk, I will report on recent advances in the quantitative theoretical description of bubble dynamics, and, adopting typical benchmark models, present numerical results for the wall velocity and the profiles that describe the phase transition dynamics. A near-universal behaviour across models will emerge and be discussed
Implications for Pulsar Timing Arrays of Sub-solar Black Hole Detections: From LVK to Einstein Telescope and Cosmic Explorer
No full textThe detection of compact binary mergers with sub-solar masses at gravitational-wave observatories could mark the groundbreaking discovery of primordial black holes (PBHs). Concurrently, evidence for a nHz stochastic gravitational wave background observed by pulsar timing arrays (PTAs) could suggest a non-astrophysical origin, potentially arising from scalar-induced gravitational waves (SIGW). In this work, we analyze the connection between the two phenomena in the case where they share a common origin: the collapse of large primordial curvature perturbations in the early universe. We focus on sub-solar PBH populations within reach of upcoming experiments, including the current and future runs of LIGO-Virgo-KAGRA as well as the third generation observatories such as the Einstein Telescope and Cosmic Explorer. Using a Bayesian framework with physically motivated priors, we perform a consistent model comparison that incorporates existing astrophysical bounds together with the discovery potential of future detectors. Our analysis lends stronger support for the SIGW interpretation over the astrophysical one, as the narrowed priors place greater weight on the region of highest likelihood. Ultimately, we illustrate that combining PTA data with interferometer searches can deliver correlated evidence for new physics across multiple gravitational-wave bands
Observation of structures in the mass spectrum with the ATLAS detector
No full textA search for resonant structures in the (2S) mass spectrum is performed using proton-proton collision data at TeV, corresponding to an integrated luminosity of 140 fb, recorded by the ATLAS experiment at the LHC. The decay channels of and are analyzed. An excess near 6.9 GeV is observed in both channels with a combined significance of 8.9. No significant signal is observed near 7.2 GeV, and an upper limit on its yield relative to (6900) is provided. A simultaneous fit with the di- channel is carried out under assumptions regarding the resonance interferences, yielding a ratio of the partial decay widths between the and di- channels of for the resonance near 6.9 GeV.A search for resonant structures in the (2S) mass spectrum is performed using proton--proton collision data at TeV, corresponding to an integrated luminosity of 140 fb, recorded by the ATLAS experiment at the LHC. The decay channels of and are analyzed. An excess near 6.9 GeV is observed in both channels with a combined significance of 8.9. No significant signal is observed near 7.2 GeV, and an upper limit on its yield relative to (6900) is provided. A simultaneous fit with the di- channel is carried out under assumptions regarding the resonance interferences, yielding a ratio of the partial decay widths between the and di- channels of for the resonance near 6.9 GeV
Quarkonia collectivity in large collision systems with ALICE
No full textQuarkonium production is one of the golden probes to study the quark--gluon plasma (QGP). Among many observables, the measurement of azimuthal anisotropies in quarkonium production sheds light on the collective behavior of heavy-flavor particles in a strongly interacting medium. In particular, the measurements of the elliptic flow () of quarkonia in Pb--Pb collisions at the LHC provide us direct evidence of heavy quark thermalization in the QGP. In these proceedings, new results of inclusive elliptic flow measurement in Pb--Pb collisions carried out by the ALICE collaboration in Run 3 using three methods including event-plane, scalar-product and multi-particle correlation (cumulant) will be presented. The method of cumulant will give access to the flow fluctuations at forward rapidity. Alongside the new flow measurements of , new results of flow measurement at forward rapidity in ALICE Run 3 will be presented as well with comparison to model calculations