Publications by Giacomo Artoni


Searches for electroweak production of supersymmetric particles with compressed mass spectra in √s=13 TeV pp collisions with the ATLAS detector

Physical Review D: Particles, Fields, Gravitation and Cosmology American Physical Society 101 (2020) 052005

L Ambroz, G Artoni, M Backes, W Balunas, A Barr, D Bortoletto, Foti, J Frost, GE Gallardo, E Gallas, C Gwenlan, B Huffman, C Merlassino, K Nagai, R Nickerson, SR Paredes Saenz, Petrov, Sharma, Shipsey, M Stankaityte, C Tosciri, Wölker, Zgubič

This paper presents results of searches for the electroweak production of supersymmetric particles in models with compressed mass spectra. The searches use 139 fb⁻¹ of √s = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider. Events with missing transverse momentum and two same-flavor, oppositely charged, low-transverse-momentum leptons are selected, and are further categorized by the presence of hadronic activity from initial-state radiation or a topology compatible with vector-boson fusion processes. The data are found to be consistent with predictions from the Standard Model. The results are interpreted using simplified models of R-parity-conserving supersymmetry in which the lightest supersymmetric partner is a neutralino with a mass similar to the lightest chargino, the second-to-lightest neutralino, or the slepton. Lower limits on the masses of charginos in different simplified models range from 193 to 240 GeV for moderate mass splittings, and extend down to mass splittings of 1.5 to 2.4 GeV at the LEP chargino bounds (92.4 GeV). Similar lower limits on degenerate light-flavor sleptons extend up to masses of 251 GeV and down to mass splittings of 550 MeV. Constraints on vector-boson fusion production of electroweak SUSY states are also presented.


Measurement of VH, H -> b(b)over-bar production as a function of the vector-boson transverse momentum in 13 TeV pp collisions with the ATLAS detector

Journal of High Energy Physics Springer 2019 (2019) 141

D Bortoletto, M Aaboud, G Aad, B Abbott, L Ambroz, G Artoni, WK Balunas, AJ Barr, L Beresford, AM Cooper-Sarkar, JA Frost, EJ Gallas, F Giuli, C Gwenlan, CP Hays, TB Huffman, C Issever, JKK Liu, L Marchese, K Nagai, ME Nelson, R Nickerson, E Schopf, IPJ Shipsey

Cross-sections of associated production of a Higgs boson decaying into bottomquark pairs and an electroweak gauge boson, W or Z, decaying into leptons are measured as a function of the gauge boson transverse momentum. The measurements are performed in kinematic fiducial volumes defined in the ‘simplified template cross-section’ framework. The results are obtained using 79.8 fb−1 of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. All measurements are found to be in agreement with the Standard Model predictions, and limits are set on the parameters of an effective Lagrangian sensitive to modifications of the Higgs boson couplings to the electroweak gauge bosons.


Search for dark matter and other new phenomena in events with an energetic jet and large missing transverse momentum using the ATLAS detector

Journal of High Energy Physics Springer Verlag 2018 (2018) 126

G Aad, G Artoni, A Barr, K Becker, L Beresford, D Bortoletto, A Cooper-Sarkar, JA Frost, E Gallas, C Gwenlan, F Giuli, C Hays, T Huffman, C Issever, J Liu, L Marchese, K Nagai, ME Nelson, R Nickerson, I Shipsey, G Viehhauser, J Tseng, A Weidberg, G Zemaityte

Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy of 13 TeV collected in 2015 and 2016 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons (e or μ). Several signal regions are considered with increasing requirements on the missing transverse momentum above 250 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, and supersymmetric particles in several compressed scenarios.


Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb(-1) of root&ITs&IT = 13 TeV &ITpp&IT collision data with the ATLAS detector

Journal of High Energy Physics Springer 2017 (2017) 84

G Aad, B Abbott, G Artoni, A Barr, AK Becker, A Cooper-Sarkar, L Beresford, E Gallas, D Bortoletto, C Hays, F Giuli, L Marchese, C Gwenlan, R Nickerson, C Issever, B Huffman, J Frost, G Viehhauser, J Tseng, K Nagai, I Shipsey, J Liu, G Zemaityte, AR Weidberg, ME Nelson

A search for strongly produced supersymmetric particles using signatures involving multiple energetic jets and either two isolated same-sign leptons (e or μ), or at least three isolated leptons, is presented. The analysis relies on the identification of b-jets and high missing transverse momentum to achieve good sensitivity. A data sample of proton-proton collisions at s√=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to a total integrated luminosity of 36.1 fb−1, is used for the search. No significant excess over the Standard Model prediction is observed. The results are interpreted in several simplified supersymmetric models featuring R-parity conservation or R-parity violation, extending the exclusion limits from previous searches. In models considering gluino pair production, gluino masses are excluded up to 1.87 TeV at 95% confidence level. When bottom squarks are pair-produced and decay to a chargino and a top quark, models with bottom squark masses below 700 GeV and light neutralinos are excluded at 95% confidence level. In addition, model-independent limits are set on a possible contribution of new phenomena to the signal region yields.