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Creators/Authors contains: "Barbieri, M"

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  1. Almost all globular clusters (GCs) contain multiple stellar populations consisting of stars with varying helium and light-element abundances. These populations include first-population stars, which exhibit similar chemical compositions as halo-field stars with comparable [Fe/H], and second-population stars, characterized by higher helium and nitrogen abundances along with reduced levels of oxygen and carbon. Nowadays, one of the most intriguing open questions about GCs pertains to the formation and evolution of their multiple populations. Recent works based on N-body simulations of GCs show that the fractions and characteristics of binary stars can serve as dynamic indicators of the formation period of multiple-population GCs and their subsequent dynamical evolution. Nevertheless, the incidence of binaries among multiple populations is still poorly studied. Moreover, the few available observational studies focus only on the bright stars of a few GCs. We used deep images of the GC 47 Tucanae collected with theJames Webband theHubblespace telescopes to investigate the incidence of binaries among multiple populations of M dwarfs and bright main- sequence stars. To reach this objective, we used UV, optical, and near-infrared filters to construct photometric diagrams that allowed us to disentangle binary systems and multiple populations. Moreover, we compared these observations with a large sample of simulated binaries. In the cluster central regions, the incidence of binaries among first-population stars is only slightly higher than that of second- population stars. In contrast, in the external regions, the majority of the studied binaries (≳85%) are composed of first-population stars. These results are consistent with the GC formation scenarios in which the second-population stars originate in the cluster’s central region, forming a compact and dense stellar group within a more extended system of first-population stars. 
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    Free, publicly-accessible full text available June 1, 2026
  2. A<sc>bstract</sc> Inclusive and differential cross sections for Higgs boson production in proton-proton collisions at a centre-of-mass energy of 13.6 TeV are measured using data collected with the CMS detector at the LHC in 2022, corresponding to an integrated luminosity of 34.7 fb−1. Events with the diphoton final state are selected, and the measured inclusive fiducial cross section is$${\sigma }_{\text{fid}}={74}\pm {11}{\left({\text{stat}}\right)}_{-4}^{+5}\left({\text{syst}}\right)$$fb, in agreement with the standard model prediction of 67.8 ± 3.8 fb. Differential cross sections are measured as functions of several observables: the Higgs boson transverse momentum and rapidity, the number of associated jets, and the transverse momentum of the leading jet in the event. Within the uncertainties, the differential cross sections agree with the standard model predictions. 
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    Free, publicly-accessible full text available September 1, 2026
  3. A measurement is presented of the cross section in proton-proton collisions for the production of two W bosons and one Z boson. It is based on data recorded by the CMS experiment at the CERN LHC at center-of-mass energies s = 13 and 13.6 TeV, corresponding to an integrated luminosity of 200 fb 1 . Events with four charged leptons (electrons or muons) in the final state are selected. Both nonresonant W W Z production and Z H production, with the Higgs boson decaying into two W bosons, are reported. For the first time, the two processes are measured separately in a simultaneous fit. Combining the two modes, signal strengths relative to the standard model (SM) predictions of 0.75 0.29 + 0.34 and 1.74 0.60 + 0.71 are measured for s = 13 and 13.6 TeV, respectively. The observed (expected) significance for the triboson signal is 3.8 (2.5) standard deviations for s = 13.6 TeV , thus providing the first evidence for triboson production at this center-of-mass energy. Combining the two modes and the two center-of-mass energies, the inclusive signal strength relative to the SM prediction is measured to be 1.03 0.28 + 0.31 , with an observed (expected) significance of 4.5 (5.0) standard deviations. 
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    Free, publicly-accessible full text available August 1, 2026
  4. A<sc>bstract</sc> The first measurement of the dijet transverse momentum balancexjin proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of$$\sqrt{{s}_{\text{NN}}}$$= 8.16 TeV is presented. Thexjobservable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb−1, were collected with the CMS detector in 2016. Thexjdistributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractionsxin the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios ofxjdistributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events. 
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    Free, publicly-accessible full text available July 1, 2026
  5. We report the discovery of a Neptune-like planet (LP 714-47 b, P = 4.05204 d, m b = 30.8 ± 1.5 M ⊕ , R b = 4.7 ± 0.3 R ⊕ ) located in the “hot Neptune desert”. Confirmation of the TESS Object of Interest (TOI 442.01) was achieved with radial-velocity follow-up using CARMENES, ESPRESSO, HIRES, iSHELL, and PFS, as well as from photometric data using TESS, Spitzer , and ground-based photometry from MuSCAT2, TRAPPIST-South, MONET-South, the George Mason University telescope, the Las Cumbres Observatory Global Telescope network, the El Sauce telescope, the TÜBİTAK National Observatory, the University of Louisville Manner Telescope, and WASP-South. We also present high-spatial resolution adaptive optics imaging with the Gemini Near-Infrared Imager. The low uncertainties in the mass and radius determination place LP 714-47 b among physically well-characterised planets, allowing for a meaningful comparison with planet structure models. The host star LP 714-47 is a slowly rotating early M dwarf ( T eff = 3950 ± 51 K) with a mass of 0.59 ± 0.02 M ⊙ and a radius of 0.58 ± 0.02 R ⊙ . From long-term photometric monitoring and spectroscopic activity indicators, we determine a stellar rotation period of about 33 d. The stellar activity is also manifested as correlated noise in the radial-velocity data. In the power spectrum of the radial-velocity data, we detect a second signal with a period of 16 days in addition to the four-day signal of the planet. This could be shown to be a harmonic of the stellar rotation period or the signal of a second planet. It may be possible to tell the difference once more TESS data and radial-velocity data are obtained. 
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