Professor Daniela Bortoletto

Abstract:

The ASICs for the Phase 2 upgrade of the ATLAS and CMS pixel detectors have been jointly designed by the RD53 collaboration in 65 nm CMOS technology. One of the main design requirements of the ASICs was their ability to withstand an environment with unprecedented radiation doses, up to total ionzing doses (TID) of 1 Grad, delivered at a dose rate of around 20 krad/h. From simulation of the ASIC, the main limiting factor of the ASIC design is expected to be the small transistors used in the digital logic. As part of the ASIC characterization program, many dedicated irradiation measurements have been performed on ring oscillator circuits included in the chip for testing. This paper aims to summarize the main findings of these irradiation measurements, performed at the expected operational temperatures of the ASIC around −10 °C. First, the dose rate dependence of the damage to the digital logic is characterized in X-ray irradiations to low TID with varying dose rates. Then, results from X-ray irradiations and a long-term low dose rate irradiation using a Kr-85 source are compared, to estimate the expected damage at high TID delivered at a low dose rate. Finally, the combination of these measurements is used to predict the expected failure of the ASIC in terms of integrated luminosity collected by the ATLAS experiment, assuming the expected total ionizing doses for both the innermost layers in Barrel and Endcap of the upgraded ATLAS Inner Tracker (ITk).

Abstract:

This Letter presents a measurement of prompt charged-particle production in proton-oxygen interactions at s NN = 9.62     TeV center-of-mass energy with the ATLAS detector, corresponding to 634     μ b − 1 of integrated luminosity. A total of 246 × 10 6 selected events have at least one track with transverse momentum p T > 500     MeV and pseudorapidity | η | < 2.5 . The measured fiducial proton-oxygen cross section is σ fid . p O = 396 ± 6 ( exp . ) ± 9 ( lumi . )     mb and the extrapolated inelastic proton-air cross section is σ inel . p + air = 406 ± 6 ( exp . ) ± 9 ( lumi . ) ± 28 ( th . )     mb . Measurements of charged-particle multiplicity, p T , and η distributions are an order-of-magnitude more precise than differences between hadronic-interaction models. These results enable improved modeling of cosmic-ray air showers, which is important for astroparticle physics.

Abstract:

Entanglement is a key property of quantum systems. In this Letter the first measurements of quantum entanglement between spins in pairs of $Z$ bosons are reported, using proton-proton collision data from the Large Hadron Collider (LHC) at center-of-mass energies of 13 and 13.6 TeV, recorded with the ATLAS detector. Measurements of angular observables sensitive to $Z{Z}^{*}$ spin-density-matrix elements in the $H\to Z{Z}^{*}\to {\ell }^{+}{\ell }^{-}{\ell }^{+}{\ell }^{-}$ process yield coefficients $C_{2,1,2,-1}=-0.71\pm 0.45$ and $C_{2,2,2,-2}=0.08\pm 0.44$ , consistent with their Standard Model predictions. A complementary hypothesis test using the full angular distribution, and relying on several Standard Model assumptions in the decays, provides substantially higher sensitivity to quantum correlations and disfavors the separable-state hypothesis at a significance of 4.7 standard deviations (expected $4.9\sigma$ ) relative to the entangled Standard Model hypothesis. These results provide strong evidence of quantum entanglement between massive bosons (spin qutrits) at the electroweak scale.

Abstract:

This Letter presents the first evidence of the simultaneous production of two $Z$ bosons and one photon with the ATLAS detector at the Large Hadron Collider. The measurement is performed using the full Run-2 dataset, recorded from 2015 to 2018, of proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $140{\mathrm{fb}}^{-1}$ . The fully leptonic final state with four leptons and one photon is analyzed, $pp\to ZZ\gamma \to {\ell }^{+}{\ell }^{-}{\ell }^{\prime +}{\ell }^{\prime -}\gamma$ with $\ell ,{\ell }^{\prime }=e$ or $\mu$ . This final state is measured in a fiducial region where photon final-state radiation is minimized, and the photon has a transverse momentum of $p_{\mathrm{T}}^{\gamma }>20\mathrm{GeV}$ . Eight events are selected, with a background estimate of $0.92\pm 0.15$ . This results in an observed (expected) significance of the $ZZ\gamma$ final state of $4.4\sigma$ ( $4.0\sigma$ ). The measured cross section for $pp\to ZZ\gamma \to {\ell }^{+}{\ell }^{-}{\ell }^{\prime +}{\ell }^{\prime -}\gamma$ in the fiducial region is ${\sigma }_{ZZ\gamma }=0.144_{-0.051}^{+0.065}{(\mathrm{stat})}_{-0.004}^{+0.008}(\mathrm{syst})\mathrm{fb}$ , in agreement with the standard model prediction of ${\sigma }_{\mathrm{fid}}^{\mathrm{SM}}=0.130\pm 0.006\mathrm{fb}$ .

Abstract:

This Letter reports on the first evidence of inclusive Higgs-boson production at high transverse momentum in the $b\overline{b}$ final state, reconstructed in a single large-radius jet. The results are based on proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider at a center-of-mass energies of 13 and 13.6 TeV, corresponding to a total integrated luminosity of $301{\mathrm{fb}}^{-1}$ . The study profits from the large background suppression provided by the use of a new transformer-based algorithm for jet identification and the sharper mass and transverse momentum, $p_{\mathrm{T}}$ , resolution from a dedicated regression model. The yield relative to the standard model prediction for Higgs bosons produced at $p_{\mathrm{T}}$ larger than 450 GeV is measured to be $1.53\pm 0.2{7)}_{-0.27}^{+0.33}\pm 0.17$ , where the first uncertainty is statistical, the second is experimental systematic, and the third accounts for theory systematic, corresponding to an observed (expected) significance of $3.8\sigma (2.5\sigma )$ relative to the background-only hypothesis. Results are also obtained in three Higgs boson $p_{\mathrm{T}}$ intervals and found to be compatible with standard model predictions, where the first uncertainty is statistical, the second is experimental systematic, and the third accounts for theory systematic.