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Gregorio Bernardi

Publications and source records attributed to Gregorio Bernardi.

16 recordsLinked to original sources
arXiv2026

Toward a Measurement of the Higgs Boson Mass with Natural-Width Precision at FCC-ee

Higgs boson mass measurements with sub-10 MeV precision enable sub-percent determinations of Higgs boson couplings and prevent the Higgs boson mass from becoming a limiting input to electroweak fits. Probing the electron Yukawa coupling through resonant Higgs boson production requires a precision comparable to the Higgs boson natural width of approximately 4 MeV. Using the leptonic ZH recoil channels, we show that FCC-ee can reach a Higgs boson mass precision of 4 MeV, including statistical and systematic uncertainties, thereby enabling this unique measurement. We identify the detector and accelerator performance required to reach this precision.

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arXiv2025

Model-independent ZH production cross section at FCC-ee

This paper presents prospects for measuring the model-independent $ZH$ production cross section at the FCC-ee using the recoil-mass method at center-of-mass energies of 240 GeV and 365 GeV. Analyses are carried out in the muon, electron, and hadronic decay modes of the associated $Z$ boson. The event selections rely primarily on the kinematics of the reconstructed $Z$ decay products, ensuring maximal independence from specific Higgs boson decay modes, while multivariate techniques are employed to further enhance sensitivity. The statistical interpretation of the leptonic and hadronic final states at 240 GeV, with an integrated luminosity of 10.8 ab$^{-1}$, yields relative precisions of 0.52% for the combined leptonic channels and 0.38% for the hadronic channel. Their full statistical combination leads to total uncertainties of 0.31% at 240 GeV and 0.52% at 365 GeV, the latter assuming an integrated luminosity of 3.12 ab$^{-1}$. Dedicated statistical tests demonstrate model independence at the level of the obtained precision. This study presents the first consistent and combined analysis of the leptonic and hadronic final states for a model-independent $ZH$ cross-section measurement at a future lepton collider, using a unified workflow and covering both $\sqrt{s}=240$ and 365 GeV. It provides the most precise expected measurement of the $ZH$ production cross section at future lepton colliders, with the degree of model independence demonstrated within the achieved statistical precision.

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arXiv2021

A special Higgs challenge: Measuring the mass and production cross section with ultimate precision at FCC-ee

The FCC-ee offers powerful opportunities to determine the Higgs boson parameters, exploiting over $10^6$ ${\rm e^+e^- \to ZH}$ events and almost $10^5$ ${\rm WW \to H}$ events at centre-of-mass energies around 240 and 365 GeV. This essay spotlights the important measurements of the ZH production cross section and of the Higgs boson mass. The measurement of the total ZH cross section is an essential input to the absolute determination of the HZZ coupling -- a "standard candle" that can be used by all other measurements, including those made at hadron colliders -- at the per-mil level. A combination of the measured cross sections at the two different centre-of-mass energies further provides the first evidence for the trilinear Higgs self-coupling, and possibly its first observation if the cross-section measurement can be made accurate enough. The determination of the Higgs boson mass with a precision significantly better than the Higgs boson width (4.1 MeV in the Standard Model) is a prerequisite to either constrain or measure the electron Yukawa coupling via direct ${\rm e^+e^- \to H}$ production at $\sqrt{s} = 125$ GeV. Approaching the statistical limit of 0.1% and $\mathcal{O}(1)$ MeV on the ZH cross section and the Higgs boson mass, respectively, sets highly demanding requirements on accelerator operation (ZH threshold scan, centre-of-mass energy measurement), detector design (lepton momentum resolution, hadronic final state reconstruction performance), theoretical calculations, and analysis techniques (efficiency and purity optimization with modern tools, constrained kinematic fits, control of systematic uncertainties). These challenges are examined in turn in this essay.

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arXiv2014

Review of Physics Results from the Tevatron

We present a comprehensive review of the physics results obtained by the CDF and D0 collaborations up to summer 2014, with emphasis on those achieved in the Run II of the Tevatron collider which delivered a total integrated luminosity of ~10 fb-1 at sqrt{s}=1.96 TeV. The results are presented in six main physics topics: QCD, Heavy Flavor, Electroweak, Top quark, Higgs boson and searches for New Particles and Interactions. The characteristics of the accelerator, detectors, and the techniques used to achieve these results are also briefly summarized.

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arXiv2014

Standard Model Higgs Boson Searches through the 125 GeV Boson Discovery

Searches for the standard model Higgs boson are reviewed from the 2 TeV run of the Tevatron with ~ 10 fb-1 of recorded data, and from the 7 and 8 TeV runs of the LHC, with ~ 5 and ~ 6 fb-1, respectively, i.e., until the July-2012 discovery of a new particle by the LHC experiments. The CMS and ATLAS Collaborations observe independently a new boson with mass ~ 125 GeV, mainly through its bosonic decays in gammagamma, ZZ, and W+W-, consistent with the standard model Higgs boson. The CDF and D0 experiments combine their results to see evidence of a similar particle produced in association with a vector boson and decaying fermionically in bbbar.

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arXiv2012

Status Report of the DPHEP Study Group: Towards a Global Effort for Sustainable Data Preservation in High Energy Physics

Data from high-energy physics (HEP) experiments are collected with significant financial and human effort and are mostly unique. An inter-experimental study group on HEP data preservation and long-term analysis was convened as a panel of the International Committee for Future Accelerators (ICFA). The group was formed by large collider-based experiments and investigated the technical and organisational aspects of HEP data preservation. An intermediate report was released in November 2009 addressing the general issues of data preservation in HEP. This paper includes and extends the intermediate report. It provides an analysis of the research case for data preservation and a detailed description of the various projects at experiment, laboratory and international levels. In addition, the paper provides a concrete proposal for an international organisation in charge of the data management and policies in high-energy physics.

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arXiv2008

Searches and Prospects for Standard Model Higgs boson at the Tevatron

We report on results obtained at the Tevatron by the CDF and D0 collaborations up to June 2008 (2.4 fb-1), on searches for standard model (SM) Higgs bosons having a high mass (135-200 GeV). High mass Higgs bosons decay dominantly in WW and the presented searches are performed in the leptonic decay modes of the W's. Both direct production (ppbar -> H) and associated production (ppbar -> WH) are studied and eventually combined with all channels available at the Tevatron. Prospects for SM Higgs searches with the full projected Tevatron statistics are also given.

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arXiv2005

Searches for Higgs Boson(s) at the Upgraded Tevatron

We summarize the status of Higgs boson searches at the upgraded Fermilab Tevatron performed by the DO and CDF collaborations. We report on three categories of searches, namely 1) the search for the Standard Model Higgs boson (p\bar{p} --> H, WH or ZH, with H --> WW* and/or H --> b\bar{b}), 2) the search for the minimal supersymmetric Higgs boson using p\bar{p} --> hb\bar{b} --> b\bar{b}b\bar{b} and p\bar{p} --> hX --> tau tau X, 3) the search for doubly charged Higgs boson.

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arXiv1998

Structure Function Measurements and Kinematic Reconstruction at HERA

The procedure used for structure function measurements at HERA is briefly described and related to the properties of kinematic reconstruction. The reconstruction methods of the inclusive deep inelastic scattering variables are reviewed and their sensitivity to the energy and angle miscalibrations are discussed in detail. New prescriptions are introduced and related to the standard methods in order to optimize the F_2 structure function measurement over the widest kinematic range, both in the low x, low Q^2 and in the high x, high Q^2 regions. The prospects for the future high Q^2 studies are briefly discussed.

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arXiv1997

H1 Results in Deep Inelastic Scattering

Recent deep inelastic results from the H1 collaboration are presented. The topics covered include inclusive diffractive physics, the determination of alpha_S using the event shapes, the study of the hadronic final state at low x with single particles and with jets, the structure function measurements in particular F_2 at low Q^2 and the high Q^2 physics both in neutral and charged current.

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arXiv1997

Some Properties of the Very High Q^2 Events of HERA

The kinematic reconstruction of neutral current high Q^2 events at HERA is discussed in detail using as an example the recently published events of the H1 and ZEUS collaborations at Q^2 > 15000 GeV^2 and M > 180 GeV, which are more numerous than expected from Standard Model predictions. Taking into account the complete information of these events, the mass reconstruction is improved and the difference between the average mass of the samples of the two experiments is reduced from 26+/-10 GeV to 17+/-7 GeV, but remains different enough to render unlikely an interpretation of the excess observed by the two collaborations as originating from the decay of a single narrow resonance.

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arXiv1996

Structure Function Measurements at HERA and Perturbative QCD

New results from the H1 and ZEUS collaborations on the measurement of cross-sections at very high Q^2 (up to 25000 GeV^2) and on the proton structure function F_2(x,Q^2) for momentum transfers squared Q^2 >= 1.5 GeV^2 and Bjorken x >= 3.5 10^{-5} are reported, using data collected at HERA mainly in 1994. No deviations from the Standard Model have been observed at high Q^2 and F_2 is seen to increase significantly with decreasing x, even in the lowest reachable Q^2 region. Comparisons at low Q^2 with fixed target experiments and with models based on pomeron exchange are presented. The F_2 results are well described by a Next to Leading Order QCD fit, and are consistent at the present level of precision with the rise at low x within this Q^2 range generated via the DGLAP evolution equations. The gluon density is extracted and being observed to rise at low x.

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arXiv1996

Low Q^2 Structure Function Measurements

New Results on the measurement of the proton structure function F_2(x,Q^2) are reported for momentum transfers squared Q^2 >= 1.5 GeV^2 and Bjorken x >= 3.5 10^{-5} using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low x within this Q^2 range is generated via the DGLAP evolution equations. A comparison with models based on pomeron exchange is also presented. The gluon density is extracted and observed to rise at low x.

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arXiv1996

Structure Function Measurement at HERA

Preliminary results on a measurement of the proton structure function F_2 are reported for momentum transfers squared Q^2 between 1.5~GeV^2 and 5000 GeV^2 and for Bjorken x between 5.10^{-5} and 0.32 using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low x within this Q^2 range is generated "radiatively" via the DGLAP evolution equations. Prospects for future structure function measurements at HERA are briefly mentioned.

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arXiv1994

On the Kinematic Reconstruction of Deep Inelastic Scattering at HERA: the $Σ$ Method

We review and compare the reconstruction methods of the inclusive deep inelastic scattering variables used at HERA. We introduce a new prescription, the $Σ$ method, which allows to measure the structure function of the proton $F_2(x,Q^2)$ in a large kinematic domain, and in particular in the low x-low$Q^2$ region, with small systematic errors and small radiative corrections. A detailed comparison between the $Σ$ method and the other methods is shown. Extensions of the $Σ$ method are presented. The effect of QED radiation on the kinematic reconstruction and on the structure function measurement is discussed.

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