http://hdl.handle.net/10183/19214 2026-11-14T09:15:50Z 2026-11-14T09:15:50Z Ortolani, Sergio Souza, Stefano O. Nardiello, Domenico Barbuy, Beatriz Bica, Eduardo Luiz Damiani Ferreira, Bernardo Pereira Lima Chiappini, C.C.M. Fernández-Trincado, José Gregorio Ernandes, Heitor http://hdl.handle.net/10183/308849 2026-07-11T11:02:36Z 2026-01-01T00:00:00Z

Ancient relic moderately metal-rich bulge cluster Tonantzintla 2 a new Milky Way globular cluster confirmed using VVV RR Lyrae stars Ortolani, Sergio; Souza, Stefano O.; Nardiello, Domenico; Barbuy, Beatriz; Bica, Eduardo Luiz Damiani; Ferreira, Bernardo Pereira Lima; Chiappini, C.C.M.; Fernández-Trincado, José Gregorio; Ernandes, Heitor The assembly history of the Galactic bulge is intimately tied to the formation of the proto–Milky Way, yet reconstructing this early phase is difficult because mergers and secular evolution have erased most of its original structure. Among present-day stellar systems, only globular clusters retain the ancient signatures needed to trace these primordial building blocks. Here we present the most detailed characterization to date of Tonantzintla 2, a prime candidate for a relic of the Milky Way’s primordial bulge. It is a moderately metal-rich globular cluster projected onto the bulge that has remained largely unexplored despite its potential to constrain the early formation of the inner Milky Way. We derive its fundamental parameters using proper-motion-corrected Hubble Space Telescope WFC3 and Advanced Camera for Surveys photometry. By applying an isochrone fitting to very clean data, we obtain an age of 13.58 + 1.0 0.72 Gyr, a reddening E(B – V ) = 1.44 ± 0.02, a metallicity [M/H] = −0.68 + 0.05 0.04 , and a heliocentric distance of d⊙ = 7.38 0.08 0.13 kpc. A complementary chemical-abundance analysis of seven member stars from APOGEE high-resolution spectroscopy reveals an enrichment pattern consistent with an in situ origin. Tonantzintla 2 is among the oldest globular clusters studied in the literature, and the oldest so far analyzed in the Galactic bulge. Its age places a stringent constraint on the onset of the bulge formation, implying that star formation in the inner Galaxy began within ∼0.2 Gyr of the Big Bang and that Tonantzintla 2 represents an exceptional relic of the Milky Way’s earliest chemical enrichment.

2026-01-01T00:00:00Z Santa Rosa, Ana Carolina Antonini Romero, Alejandra Daniela Kepler, Souza Oliveira http://hdl.handle.net/10183/308837 2026-07-01T09:55:49Z 2026-01-01T00:00:00Z

Evolution and formation of ultramassive white dwarf stars : the case for a 9M progenitor Santa Rosa, Ana Carolina Antonini; Romero, Alejandra Daniela; Kepler, Souza Oliveira We study the full evolution of a 1.313 M white dwarf star that descended from a 9 M main-sequence progenitor with an initial metallicity of Z = 0.02. Using MESA r24.08.01, we calculate its entire evolution from pre-ZAMS to the WD cooling curve, including both the evolution through 139 thermal pulses and the post-AGB phase. The resulting remnant is an ultramassive H-deficient WD, for which the composition, in mass fraction, is 47.7 per cent 16O, 39.7 per cent 20Ne, 4.2 per cent 24Mg, 3.3 per cent 23Na, and 0.386 per cent 12C – corresponding to a total mass of 5 × 10−3 M of C –, surrounded by a 1.5 × 10−5M He layer. We also investigate the effects of fully suppressing the TP-SAGB stage by adopting a high massloss rate only after the second dredge-up, and find only minor differences in the final mass and composition. In addition, we calculate models with and without phase separation during the WD stage, estimating a cooling delay of only 16 Myr. This is the first ultramassive white dwarf sequence for which both the TP-SAGB and post-AGB stages are calculated and, to our knowledge, the most massive WD model from complete evolution for which cooling times and detailed abundance profiles are published.

2026-01-01T00:00:00Z Chekhovsky, Vladimir Silveira, Gustavo Gil da CMS Collaboration http://hdl.handle.net/10183/308817 2026-07-01T09:55:26Z 2026-01-01T00:00:00Z

Search for nonresonant new physics signals in high-mass dilepton events produced in association with b-tagged jets in proton-proton collisions at √s =13TeV Chekhovsky, Vladimir; Silveira, Gustavo Gil da; CMS Collaboration A search for nonresonant new physics phenomena in high-mass dilepton events produced in association with b-tagged jets is performed using proton-proton collision data collected in 2016–2018 by the CMS experiment at the CERN LHC, at a center-of-mass energy of 13TeV corresponding to an integrated luminosity of 138fb−1. The analysis considers two effective field theory models with dimension-six operators; involving four-fermion contact interactions between two leptons (ℓℓ, electrons or muons) and b or s quarks (bbℓℓ and bsℓℓ). Two lepton flavor combinations (ee and µµ) are required and events are classified as having 0, 1, or ≥2 b-tagged jets in the final state. No significant excess is observed over the standard model backgrounds. Upper limits are set on the production cross section of the new physics signals. These translate into lower limits on the energy scale Λ of 6.9 to 9.0TeV in the bbℓℓ model, depending on model parameters, and on the ratio of energy scale and effective coupling, Λ/g∗, of 2.0 to 2.6TeV in the bsℓℓ model. Lepton flavor universality is also tested by comparing the dielectron (ee) and dimuon (µµ) mass spectra for different b-tagged jet multiplicities. No significant deviation from the standard model expectation of unity is observed.

2026-01-01T00:00:00Z Gay Ducati, Maria Beatriz Krug, Cristiano ALICE Collaboration http://hdl.handle.net/10183/308794 2026-06-28T11:07:02Z 2026-01-01T00:00:00Z

Observation of partonic flow in proton—proton and proton—nucleus collisions Gay Ducati, Maria Beatriz; Krug, Cristiano; ALICE Collaboration Quantum Chromodynamics predicts a phase transition from hadronic matter to quark–gluon plasma (QGP) at high temperatures and energy densities, where quarks and gluons (partons) are no longer confined within hadrons. The QGP forms in ultrarelativistic heavy-ion collisions. Anisotropic flow coefficients, quantifying the azimuthal expansion of produced matter, probe QGP properties. Flow measurements in high-energy heavy-ion collisions show a distinctive grouping of anisotropic flow for baryons and mesons at intermediate transverse momentum – a feature associated with flow imparted at the quark level, confirming QGP existence. The observation of QGP-like features in proton–proton and proton–ion collisions has sparked debate about QGP formation in smaller systems. For the first time, we demonstrate the distinctive grouping of anisotropic flow for baryons and mesons in highmultiplicity proton–lead and proton–proton collisions at the Large Hadron Collider (LHC). These results are described by a model including hydrodynamic flow followed by hadron formation via quark coalescence, consistent with the formation of partonic flowing systems in these collisions.

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