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Ultraslow-roll inflation on the lattice. II.: Nonperturbative curvature perturbation
No full textBuilding on the recent lattice simulations of ultraslow-roll dynamics presented in [A. Caravano et al., Phys. Rev. D 111, 063518 (2025).], we investigate the role of the nonlinear relation between the inflaton field configuration and the curvature perturbation ζ, the key observable after inflation. Using a nonperturbative δN approach applied to the lattice output, we generate fully nonlinear three-dimensional maps of ζ. This calculation captures both the non-Gaussianity arising from the nonlinear mapping between ϕ and ζ, and the intrinsic non-Gaussianity generated around Hubble crossing by the nonlinear field dynamics, which is neglected in stochastic approaches. We find that the nonlinear mapping has a profound impact on the statistics, significantly enhancing the positive tail of the ζ probability distribution, with important implications for observable quantities. A central part of this work is the comparison with the standard perturbative treatment based on a gauge transformation, which allows us to quantify when and how the perturbative picture breaks down as fluctuations grow large. Together with the above article, this work sets the basis for robust, nonperturbative predictions of primordial black hole production and scalar-induced gravitational wave emission from inflation using lattice simulations.Building on the recent lattice simulations of ultra-slow-roll (USR) dynamics presented in arXiv:2410.23942, we investigate the role of the nonlinear relation between the inflaton field configuration and the curvature perturbation , the key observable after inflation. Using a nonperturbative approach applied to the lattice output, we generate fully nonlinear three-dimensional maps of . This calculation captures both the non-Gaussianity arising from the nonlinear mapping between and , and the intrinsic non-Gaussianity generated around Hubble crossing by the nonlinear field dynamics, which is neglected in stochastic approaches. We find that the nonlinear mapping has a profound impact on the statistics, significantly enhancing the positive tail of the probability distribution, with important implications for observable quantities. A central part of this work is the comparison with the standard perturbative treatment based on a gauge transformation, which allows us to quantify when and how the perturbative picture breaks down as fluctuations grow large. Together with arXiv:2410.23942, this work sets the basis for robust, nonperturbative predictions of primordial black hole production and scalar-induced gravitational wave emission from inflation using lattice simulations
Testing T2K's Bayesian constraints with priors in alternate parameterisations
No full textBayesian analysis results require a choice of prior distribution. In long-baseline neutrino oscillation physics, the usual parameterisation of the mixing matrix induces a prior that privileges certain neutrino mass and flavour state symmetries. Here we study the effect of privileging alternate symmetries on the results of the T2K experiment. We find that constraints on the level of CP violation (as given by the Jarlskog invariant) are robust under the choices of prior considered in the analysis. On the other hand, the degree of octant preference for the atmospheric angle depends on which symmetry has been privileged.Bayesian analysis results require a choice of prior distribution. In long-baseline neutrino oscillation physics, the usual parameterisation of the mixing matrix induces a prior that privileges certain neutrino mass and flavour state symmetries. Here we study the effect of privileging alternate symmetries on the results of the T2K experiment. We find that constraints on the level of CP violation (as given by the Jarlskog invariant) are robust under the choices of prior considered in the analysis. On the other hand, the degree of octant preference for the atmospheric angle depends on which symmetry has been privileged
14th White Rabbit Workshop
No full textIn the recent years, Cherenkov telescopes have begun to be used for observations in the optical band using the technique of intensity interferometry. Intensity interferometry requires fast detectors—which Cherenkov telescopes already possess, as their cameras are comprised of photomultiplier tubes (PMTs)—as well as time synchronization between two telescopes to record data simultaneously and enable correlation either in real time or offline.
White Rabbit (WR) is employed for this synchronization, achieving sub-nanosecond accuracy. However, to further increase the signal-to-noise ratio (SNR) and detect fainter sources, even faster detectors are needed—for example, single-photon avalanche diodes (SPADs). These detectors are capable of detecting individual photons and generating corresponding pulses with overall jitter under 10 ps RMS. This imposes even stricter time synchronization requirements: the timing between two telescopes or detectors must match the SPAD-induced jitter, i.e., be below 10 ps.
WR, built upon the Precision Time Protocol (PTP), natively offers sub-nanosecond synchronization with deterministic latency. We demonstrate that a WR network can be efficiently shared between optical and Imaging Atmospheric Cherenkov Telescope (IACT) observatories for joint intensity interferometry observations. We investigate and address key challenges, including the effects of fiber temperature fluctuations and chromatic dispersion, which can impact long-distance timing stability.
Through experimental validation, we achieve 8 ps RMS time synchronization over a 50 km fiber link, demonstrating the feasibility of WR for high-precision astronomical applications. Furthermore, we analyze how WR clock phase coherence affects intensity interferometry sensitivity and discuss the implications for long-baseline and large-scale deployments
Search for Higgs boson decays into a pair of pseudoscalar particles in the final state using pp collisions at = 13 TeV with the ATLAS detector
No full textMany well-motivated extensions of the Standard Model predict light (pseudo)scalars, referred to as bosons, that couple to the 125 GeV Higgs boson, enabling new exotic decay modes. This study presents a search for Higgs boson decays into a pair of such particles, , where one -boson decays into a photon pair and the other into a -lepton pair, performed for the first time at the Large Hadron Collider. Both -leptons are reconstructed in their hadronic decay modes using a novel dedicated tagger for collimated -lepton pairs. The search uses 140 fb of proton–proton collision data at a centre-of-mass energy of TeV recorded between 2015 and 2018 by the ATLAS experiment. The search is performed in the mass range of the boson between 10 GeV and 60 GeV
Quantifying the Heat Load to Conductors Due to Strain Energy Release in CTD-101 K Magnet Impregnant
No full textState-of-the-art Nb3Sn superconducting accelerator magnets are still prone to lengthy training. This study investigates whether direct heat from fractures in commonly used magnet impregnant is sufficient to cause the instabilities during training. To do so, the strain energy release rate of CTD-101 K epoxy is measured in liquid nitrogen at 77 K, together with the temperature of a nearby copper element representing a Nb3Sn strand in the magnet windings. This experiment provides evidence that a large
part of the mechanical energy is converted into heat. An analytical model using strain energy release rate data of impregnates at 4.2 K shows that this heat can contribute to the first quenches during magnet training
Analysis methods - ATLAS
No full textHiggs measurements and searches in ATLAS rely on advanced machine learning (ML) techniques to enhance the reconstruction and identification of physics objects and improve data analysis strategies. In recent years, ML methods have been extensively developed and integrated across various domains, including jet flavour tagging, event classification and simulation modelling, to name a few. These techniques have significantly improved the sensitivity and reach of the different Higgs analyses. This talk presents highlights of recent advancements on analysis methods and techniques within ATLAS
Muon Reconstruction Performance of the ATLAS Detector Using Run-3 pp collision data
No full textAccurately measuring the muon performance of the ATLAS detector is crucial for providing essential input to physics analyses involving muons. For LHC Run 3, the ATLAS Muon Spectrometer underwent significant upgrades, most notably the New Small Wheel project, which introduced innovative new muon detectors. Evaluating the performance of these upgrades using Run 3 data is therefore of great importance
Ratio of <math display="inline"><mi>γ</mi><mo>/</mo><msup><mi>π</mi><mn>0</mn></msup></math> production rates in neutrino-nucleus interactions in the <math display="inline"><mi mathvariant="normal">Δ</mi></math> resonance mass region
No full textWe study the dependence of neutrino-induced γ/π0 production (νμ(-)+A→νμ(-)(μ)+γ/π0+X) on the target nucleus A, in the Δ resonance mass region. Our conclusion is based on experimental data for π0 production rates at photon-nucleus interactions from the A2 Collaboration at the Mainz MAMI accelerator. We assume that Δ resonance decays are independent of the production mechanism (via photon, Z, or W boson). In neutral current (NC) interactions, the 1π0+X production scales as A2/3. In contrast, photons from Δ decays typically escape the nucleus, resulting in a cross-section proportional to the atomic number A. Thus, in NC interactions, the ratio of γ production to π0 production is proportional to A1/3. In charged current (CC) νμ- (ν¯μ)-induced production of Δ+ (Δ0) will be proportional to the number of neutrons (protons) in the nucleus. After Δ decay, due to the charge universality in strong interactions, the suppression factor for π0 escaping the nucleus must also follow A-1/3, as in NC interactions. We predict the ratio of the γ/π0 production rates in NC and CC interactions and for νμ and ν¯μ beams: argon target, ∼3.1% (NC/CC νμ/ν¯μ); water target, ∼1.9% (NC), ∼2.3% (CC νμ), and ∼1.7% (CC ν¯μ); liquid scintillator target: ∼1.7% (NC), ∼2.1% (CC νμ), and ∼1.6% (CC ν¯μ). The accuracy of our predictions is limited due to uncertainties in the decay rate Δ+/0→p/n+γ and the presence of other (minor) channels of neutrino-induced γ/π0 production in the Δ mass region. We also discuss solving the MiniBooNE anomaly by looking at the CC single-photon and single-neutral-pion production rates at the short baseline neutrino program experiments at Fermilab.We study the dependence of neutrino-induced production () on the target nucleus A, at the resonance mass region. Our conclusion is based on experimental data for production rates at photon-nucleus interactions from the A2 collaboration at the Mainz MAMI accelerator. We assume that resonance decays are independent of the production mechanism (via photon, Z, or W boson). In Neutral Current (NC) interactions, the production scales as A. In contrast, photons from decays typically escape the nucleus, resulting in a cross-section proportional to the atomic number A. Thus, in NC interactions, the ratio of production to production is proportional to A. In Charged Current (CC) () -induced production of () will be proportional to the number of neutrons (protons) in the nucleus. After decay, due to the charge universality in strong interactions, the suppression factor for escaping the nucleus must also follow A, as in NC interactions. We predict the ratio of the production rates in NC and CC interactions and for and beams: {Argon target}: 3.1% (NC/CC ). {\bf Water target}: 1.9% (NC), 2.3% (CC ), 1.7% (CC ). {Liquid Scintillator target}: 1.7% (NC), 2.1% (CC ), 1.6% (CC ). We also discuss solving the MiniBooNE anomaly by looking at the CC single photon and single neutral pion production rates at the SBN program experiments at Fermilab
Improved measurement of mixing in decays
No full textBranching fraction ratios between the decays are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb. The measured ratios of these branching fractions are where the uncertainties are statistical, systematic and related to the precision of the branching fractions, respectively. They are used to constrain the mixing angle, , and to probe the presence of a possible glueball component in the meson, described by the gluonic mixing angle . The obtained results are , where the uncertainties are statistically dominated. While the value of is compatible with existing experimental determinations and theoretical calculations, the angle differs from zero by more than four standard deviations, which points to a substantial glueball component in the meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.Branching fraction ratios between the decays are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb. The measured ratios of these branching fractions arewhere the uncertainties are statistical, systematic and related to the precision of the η branching fractions, respectively. They are used to constrain the η/η′ mixing angle, ϕ, and to probe the presence of a possible glueball component in the η′ meson, described by the gluonic mixing angle ϕ. The obtained results arewhere the uncertainties are statistically dominated. While the value of ϕ is compatible with existing experimental determinations and theoretical calculations, the angle ϕ differs from zero by more than four standard deviations, which points to a substantial glueball component in the η′ meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date.[graphic not available: see fulltext]Branching fraction ratios between the decays are measured using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of , and , corresponding to an integrated luminosity of . The measured ratios of these branching fractions are and , where the uncertainties are statistical, systematic and related to the precision of the branching fractions, respectively. They are used to constrain the mixing angle, , and to probe the presence of a possible glueball component in the meson, described by the gluonic mixing angle . The obtained results are and , where the uncertainties are statistically dominated. While the value of is compatible with existing experimental determinations and theoretical calculations, the angle differs from zero by more than four standard deviations, which points to a substantial glueball component in the meson and/or unexpectedly large contributions from gluon-mediated processes in these decays. The absolute branching fractions are also measured relative to that of the well-established decay, which serves as the normalisation channel. These results supersede the previous LHCb measurements and are the most precise to date