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Search for light long-lived neutral particles from Higgs boson decays via vector-boson-fusion production from pp collisions at TeV with the ATLAS detector
No full textA search is reported for long-lived dark photons with masses between 0.1 GeV and 15 GeV, from exotic decays of Higgs bosons produced via vector-boson-fusion. Events that contain displaced collimated Standard Model fermions reconstructed in the calorimeter or muon spectrometer are probed. This search uses the full LHC Run 2 (2015–2018) data sample collected in proton–proton collisions at TeV, corresponding to an integrated luminosity of 139 . Dominant backgrounds from Standard Model processes and non-collision sources are estimated using data-driven techniques. The observed event yields in the signal regions are consistent with the expected background. Upper limits on the Higgs boson to dark photon branching fraction are reported as a function of the dark photon mean proper decay length or of the dark photon mass and the coupling between the Standard Model and the potential dark sector. This search is combined with previous ATLAS searches obtained in the gluon–gluon fusion and WH production modes. A branching fraction above 10% is excluded at 95% CL for a 125 GeV Higgs boson decaying into two dark photons for dark photon mean proper decay lengths between 173 and 1296 mm and mass of 10 GeV
Note Illustrative della Carta gravimetrica d'Italia alla scala 1:50.000, F. 337 Norcia, Servizio Geologico d'Italia - ISPRA
No full text<p>Note Illustrative redatte per il Foglio gravimetrico n. 337 Norcia della Carta Gravimetrica d'Italia alla scala 1:50.000. 46 pp.</p>
Investigation of CR heliospheric propagation models during Forbush Decrease with GPU parallelization
Get PDF<p>The Alpha Magnetic Spectrometer-02 (AMS-02) is pivotal in providing precise and exhaustive measurements of cosmic-ray (CR) fluxes in Earth's orbit. Transient variations in solar activity exert a considerable influence on low-energy CRs, challenging inferences on their intensities. Recently released daily flux measurements from the AMS open the opportunity for in-depth exploration into how solar disturbances, such as Coronal Mass Ejections, alter the heliospheric environment, leading to Forbush effects. This study conducts a comparative analysis of Forbush decreases observed by AMS-02 against predictions generated by numerical simulations of CR heliospheric propagation models. Probing multiple instances in a local and transient environment, we aim to shine a light on<br>\ngeneral properties governing CR propagation. To perform this investigation, we employ a novel Monte Carlo numerical simulation code, leveraging GPU parallelization with a Single Input Multiple Data approach. The code propagates a sample of quasi-particles backward in time through parallel, independent computations. Subsequently, the resulting distributions are averaged to solve the Parker Transport Equation. The insights gained from this study contribute to enhancing the reliability of numerical models in interpreting AMS-02 observations within the context of solar phenomena</p>
Phenomenology of a vector-field-induced and possibly parity breaking compensated isocurvature perturbation
No full textIt is natural to wonder whether there may be observational relics of new fundamental fields, beyond the inflaton, in large scale structure. Here we discuss the phenomenology of a model in which compensated isocurvature perturbations (CIPs) arise through the action of a primordial vector field that displaces dark matter relative to baryons. The model can be tested best by kinematic-Sunyaev-Zeldovich tomography, which involves the cross-correlation of cosmic microwave background and galaxy surveys, with next-generation observatories. There are also signatures of the vectorial nature of the new field that may be detectable in forthcoming galaxy surveys, but the galaxy survey cannot alone indicate the presence of a CIP. Models that induce a parity breaking four-point correlation in the galaxy distribution are also possible
Fusing photons into nothing, a new search for invisible ALPs and Dark Matter at Belle II
No full textWe consider an axion-like particle coupled to the Standard Model photons and decaying invisibly at Belle II. We propose a new search in the ee + invisible channel that we compare against the standard γ + invisible channel. We find that the ee + invisible channel has the potential to ameliorate the reach for the whole ALP mass range. This search leverages dedicated kinematic variables which significantly suppress the Standard Model background. We explore the implications of our expected reach for Dark Matter freeze-out through ALP-mediated annihilations
Quantum black hole physics from the event horizon
No full textQuantum gravity theories predict deformations of black hole solutions relative to their classical counterparts. A model-independent approach was advocated in Binetti et al. [Effective theory of quantum black holes, Phys. Rev. D 106, 046006 (2022)] that uses metric deformations parametrized in terms of physical quantities, such as the proper distance. While such a description manifestly preserves the invariance of the space-time under coordinate transformations, concrete computations are hard to tackle since the distance is defined in terms of the deformed metric itself. In this work, for spherically symmetric and static metrics, we provide a self-consistent framework allowing us to compute the distance function in close vicinity to the event horizon of a black hole. By assuming a minimal degree of regularity at the horizon, we provide explicit (series) expansions of the metric. This allows us to compute important thermodynamical quantities of the black hole, such as the Hawking temperature and entropy, for which we provide model-independent expressions, beyond a large mass expansion. Moreover, imposing for example the absence of curvature singularities at the event horizon leads to nontrivial consistency conditions for the metric deformations themselves, which we find to be violated by some models in the literature
Improving NLO QCD event generators with high-energy EW corrections
No full textIn this work we present a new method for the combination of electroweak (EW) corrections at high energies, the so-called EW Sudakov logarithms (EWSL), and next-to-leading-order QCD predictions matched to parton-shower simulations (NLO+PS). Our approach is based on a reweighting procedure of NLO+PS events. In particular, both events with and without an extra hard emission from matrix elements are consistently reweighted via the inclusion of the corresponding EWSL contribution. We describe the technical details and the implementation in the MadGraph5_aMC@NLO framework. Via a completely automated procedure, events at this level of accuracy can be obtained for a vast class of hadroproduction processes. As a byproduct we provide results for phenomenologically relevant physical distributions from top-quark pair and Higgs boson associated production () and from the associated production of three Z gauge bosons (ZZZ)
Superhorizon entanglement from inflationary particle production
No full textWe investigate entanglement generation between the sub- and super-Hubble modes of inflaton fluctuations, in the context of particle production from perturbations during inflation. We consider a large-field inflationary scenario where inflation is driven by a vacuum energy symmetry breaking potential and the scalar inflaton field is nonminimally coupled to spacetime curvature. In particular, we focus on the slow-roll phase, adopting a quasi–de Sitter scale factor to properly account for the presence of perturbations and computing the pair production probability associated with the coupling between the inflaton and spacetime inhomogeneities. The interaction Lagrangian at first order is constructed from inhomogeneities induced by the inflaton dynamics, and the initial Bunch-Davies vacuum state of the field evolves under the action of such Lagrangian. In this framework, we quantify the total amount of entanglement via the von Neumann entropy of the reduced density operator for superhorizon modes, tracing out sub-Hubble degrees of freedom. We then compare these outcomes with entanglement production for quadratic chaotic inflation and for a small-field quadratic hilltop scenario, preserving field-curvature coupling in both cases and pointing out the main differences between large- and small-field approaches. We show that the amount of entanglement entropy arising from such geometric production grows rapidly in the slow-roll regime and that it is typically higher in large-field scenarios. We also discuss our outcomes in light of recent findings for the squeezing entropy of cosmological perturbations and cubic nonlinearities in de Sitter space
First measurements with monolithic active pixel test structures produced in a 65 nm CMOS process
No full textThe Inner Tracking System (ITS) of the ALICE experiment at CERN will undergo an upgrade during the LHC long shutdown 3, in which the three innermost tracking layers will be replaced. This upgrade, named the Inner Tracking System 3 (ITS3), employs stitched wafer-scale Monolithic Active Pixel Sensors fabricated in a 65 nm CMOS process. The sensors are 260 mm in length and thinned to less than 50 μm then bent to form truly half-cylindrical half-barrels. The feasibility of this process for the ITS3 was explored with the first test production run (MLR1) in 2021, whose goal was to evaluate the charged particle detection efficiency and the sensor performance under non-ionising and ionising radiation up to the expected levels for ALICE ITS3 of 10 1 MeV n cm (NIEL) and 10 kGy (TID). Three sensor flavours were produced to investigate this process: Analog Pixel Test Structure (APTS), Circuit Exploratoire 65 (CE65) and Digital Pixel Test Structure (DPTS).This contribution gives an overview of the MLR1 submission and test results, describing the different sensor flavours and presenting the results of the performance measurements done with particle beams for various chip variants and irradiation levels
A Flexible and Efficient Approach to Missing Transverse Momentum Reconstruction
No full textMissing transverse momentum is a crucial observable for physics at hadron colliders, being the only constraint on the kinematics of "invisible" objects such as neutrinos and hypothetical dark matter particles. Computing missing transverse momentum at the highest possible precision, particularly in experiments at the energy frontier, can be a challenging procedure due to ambiguities in the distribution of energy and momentum between many reconstructed particle candidates. This paper describes a novel solution for efficiently encoding information required for the computation of missing transverse momentum given arbitrary selection criteria for the constituent reconstructed objects. Pileup suppression using information from both the calorimeter and the inner detector is an integral component of the reconstruction procedure. Energy calibration and systematic variations are naturally supported. Following this strategy, the ATLAS Collaboration has been able to optimise the use of missing transverse momentum in diverse analyses throughout Runs 2 and 3 of the Large Hadron Collider and for future analyses