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Related papers: $N_{\rm eff}$ as a new physics probe in the precis…

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We present a new constraint on the effective number of relativistic species in the early universe, $N_{\rm eff}$, by combining recent primordial helium abundance measurements from the Large Binocular Telescope $Y_p$ Project with primordial…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-23 Samuel Goldstein , J. Colin Hill

We consider the inference of the cosmic radiation density, traditionally parameterised as the effective number of neutrino species N_eff, from precision cosmological data. Paying particular attention to systematic effects, notably…

Astrophysics · Physics 2008-11-26 Jan Hamann , Steen Hannestad , Georg G. Raffelt , Yvonne Y. Y. Wong

The vast majority of extensions of the Standard Model affecting the number of effective relativistic neutrino species ($N_{\rm eff}$) do so additively, namely, they enhance this quantity with some light state contributing to dark radiation.…

High Energy Physics - Phenomenology · Physics 2026-04-03 Miguel Escudero , Maksym Ovchynnikov , Neal Weiner

We present in this work a new calculation of the standard-model benchmark value for the effective number of neutrinos, $N_{\rm eff}^{\rm SM}$, that quantifies the cosmological neutrino-to-photon energy densities. The calculation takes into…

High Energy Physics - Phenomenology · Physics 2021-05-03 Jack J. Bennett , Gilles Buldgen , Pablo F. de Salas , Marco Drewes , Stefano Gariazzo , Sergio Pastor , Yvonne Y. Y. Wong

The effective number of neutrino species, $N_{\rm eff}$, serves as a key fitting parameter extensively employed in cosmological studies. In this work, we point out a fundamental inconsistency in the conventional treatment of $N_{\rm eff}$…

High Energy Physics - Phenomenology · Physics 2026-04-27 Sougata Ganguly , Tae Hyun Jung , Seokhoon Yun

Cosmological data have provided new constraints on the number of neutrino species and the neutrino mass. However these constraints depend on assumptions related to the underlying cosmology. Since a correlation is expected between the number…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Aaron Smith , Maria Archidiacono , Asantha Cooray , Francesco De Bernardis , Alessandro Melchiorri , Joseph Smidt

New energy-density functionals (EDFs) inspired by effective-field theories (EFTs) have been recently proposed. The present work focuses on three of such functionals which were developed to produce satisfactory equations of state for nuclear…

Nuclear Theory · Physics 2018-09-26 Jérémy Bonnard , Marcella Grasso , Denis Lacroix

One of the major goals of future Cosmic Microwave Background measurements is the accurate determination of the effective number of neutrinos $N_{\rm eff}$. Reaching an experimental sensitivity of $\Delta N_{\rm eff} = 0.013$ could indeed…

Cosmology and Nongalactic Astrophysics · Physics 2018-03-28 Ludovico Capparelli , Eleonora Di Valentino , Alessandro Melchiorri , Jens Chluba

The thourough investigation of radiative corrections allows to gain information on physics processes at higher energy scales than those directly accessible by current experiments. As a consequence, using electroweak precision measurements…

High Energy Physics - Phenomenology · Physics 2011-04-22 Dörthe Ludwig

We revisit the global fit to electroweak precision observables in the Standard Model and present model-independent bounds on several general new physics scenarios. We present a projection of the fit based on the expected experimental…

High Energy Physics - Phenomenology · Physics 2017-02-28 Jorge de Blas , Marco Ciuchini , Enrico Franco , Satoshi Mishima , Maurizio Pierini , Laura Reina , Luca Silvestrini

Based on the framework of Standard Model Effective Field Theory, we performed a few global fits, each containing a subset of dimension-6 operators, for the measurements that are expected at future colliders. The fit for the Higgs and…

High Energy Physics - Phenomenology · Physics 2024-07-22 Jorge de Blas , Yong Du , Christophe Grojean , Jiayin Gu , Victor Miralles , Michael E. Peskin , Junping Tian , Marcel Vos , Eleni Vryonidou

For a long time, global fits of the electroweak sector of the Standard Model (SM) have been used to exploit measurements of electroweak precision observables at lepton colliders (LEP, SLC), together with measurements at hadron colliders…

High Energy Physics - Phenomenology · Physics 2015-06-22 M. Baak , J. Cuth , J. Haller , A. Hoecker , R. Kogler , K. Moenig , M. Schott , J. Stelzer

We perform a global analysis of the bounds from charged lepton flavour violating observables to new physics. We parametrize generic new physics through the Effective Field Theory formalism and perform global fits beyond the common…

High Energy Physics - Phenomenology · Physics 2025-10-07 Enrique Fernández-Martínez , Xabier Marcano , Daniel Naredo-Tuero

The radiative component of the Universe has a characteristic impact on both large scale structure (LSS) and the cosmic microwave background radiation (CMB). We use the recent WMAP data, together with previous CBI data and 2dF matter power…

Astrophysics · Physics 2009-11-07 Elena Pierpaoli

We derive general constraints on the mixing of heavy Seesaw neutrinos with the SM fields from a global fit to present flavour and electroweak precision data. We explore and compare both a completely general scenario, where the heavy…

High Energy Physics - Phenomenology · Physics 2016-12-22 Enrique Fernandez-Martinez , Josu Hernandez-Garcia , Jacobo Lopez-Pavon

Extending the Standard Model with higher-dimensional operators in an effective-field-theory (EFT) approach provides a systematic framework to study new-physics (NP) effects from a bottom-up perspective, as long as the NP scale is…

High Energy Physics - Phenomenology · Physics 2020-01-29 Marzia Bordone , Oscar Catà , Thorsten Feldmann

We derive here a robust bound on the effective number of neutrinos from constraints on primordial nucleosynthesis yields of deuterium and helium. In particular, our results are based on very weak assumptions on the astrophysical…

Cosmology and Nongalactic Astrophysics · Physics 2011-06-13 Gianpiero Mangano , Pasquale D. Serpico

We revisit several aspects of Standard Model physics at finite temperature that drive the theoretical value of the cosmological parameter $N_{\rm eff}$, the effective number of neutrinos in the early universe, away from 3. Our chief focus…

High Energy Physics - Phenomenology · Physics 2020-12-01 Jack J. Bennett , Gilles Buldgen , Marco Drewes , Yvonne Y. Y. Wong

The effective number of relativistic neutrino species is a fundamental probe of the early Universe and its measurement represents a key constraint on many scenarios beyond the Standard Model of Particle Physics. In light of this, an…

High Energy Physics - Phenomenology · Physics 2023-12-21 Mattia Cielo , Miguel Escudero , Gianpiero Mangano , Ofelia Pisanti

The W Mass determination at the Tevatron CDF experiment reported a deviation from the SM expectation at 7$\sigma$ level. We discuss a few possible interpretations and their collider implications. We perform electroweak global fits under…

High Energy Physics - Phenomenology · Physics 2022-12-07 Jiayin Gu , Zhen Liu , Teng Ma , Jing Shu
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