arXiv subjects

J. Quevillon

Publications and source records attributed to J. Quevillon.

8 recordsLinked to original sources

arXiv2020

Les Houches 2019 Physics at TeV Colliders: New Physics Working Group Report

This report presents the activities of the `New Physics' working group for the `Physics at TeV Colliders' workshop (Les Houches, France, 10--28 June, 2019). These activities include studies of direct searches for new physics, approaches to exploit published data to constrain new physics, as well as the development of tools to further facilitate these investigations. Benefits of machine learning for both the search for new physics and the interpretation of these searches are also presented.

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arXiv2019

Higgs boson potential at colliders: status and perspectives

This document summarises the current theoretical and experimental status of the di-Higgs boson production searches, and of the direct and indirect constraints on the Higgs boson self-coupling, with the wish to serve as a useful guide for the next years. The document discusses the theoretical status, including state-of-the-art predictions for di-Higgs cross sections, developments on the effective field theory approach, and studies on specific new physics scenarios that can show up in the di-Higgs final state. The status of di-Higgs searches and the direct and indirect constraints on the Higgs self-coupling at the LHC are presented, with an overview of the relevant experimental techniques, and covering all the variety of relevant signatures. Finally, the capabilities of future colliders in determining the Higgs self-coupling are addressed, comparing the projected precision that can be obtained in such facilities. The work has started as the proceedings of the Di-Higgs workshop at Colliders, held at Fermilab from the 4th to the 9th of September 2018, but it went beyond the topics discussed at that workshop and included further developments.

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arXiv2018

Les Houches 2017: Physics at TeV Colliders New Physics Working Group Report

We present the activities of the `New Physics' working group for the `Physics at TeV Colliders' workshop (Les Houches, France, 5--23 June, 2017). Our report includes new physics studies connected with the Higgs boson and its properties, direct search strategies, reinterpretation of the LHC results in the building of viable models and new computational tool developments.

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arXiv2017

The neutral Higgs self-couplings in the (h)MSSM

We consider the Minimal Supersymmetric extension of the Standard Model in the regime where the supersymmetric breaking scale is extermely large. In this MSSM, not only the Higgs masses will be affected by large radiative corrections, the dominant part of which is provided by the third generation quark/squark sector, but also the various self-couplings among the Higgs states. In this note, assuming that squarks are extremely heavy, we evaluate the next-to-leading order radiative corrections to the two neutral CP-even Higgs self-couplings $λ_{H h h}$ and $λ_{h h h}$ and to the partial decay width $Γ(H \to h h)$ that are most relevant at the LHC. The calculation is performed using an effective field theory approach that resums the large logarithmic squark contributions and allows to keep under control the perturbative expansion. Since the direct loop vertex corrections are generally missing in this effective approach, we have properly renormalised the effective theory to take them into account. Finally, we perform a comparison of the results in this effective MSSM with those obtained in a much simpler way in the so-called hMSSM approach in which the mass value for the lightest Higgs boson $M_{h}=125$ GeV is used as an input. We show that the hMSSM provides a reasonably good approximation of the corrected self-couplings and $H \to hh$ decay rate and, hence, it can be used also in these cases.

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arXiv2015

Fully covering the MSSM Higgs sector at the LHC

In the context of the Minimal Supersymmetric extension of the Standard Model (MSSM), we reanalyze the search for the heavier CP-even $H$ and CP-odd $A$ neutral Higgs bosons at the LHC in their production in the gluon-fusion mechanism and their decays into gauge and lighter $h$ bosons and into top quark pairs. We show that only when considering these processes, that one can fully cover the entire parameter space of the Higgs sector of the model. Indeed, they are sensitive to the low $\tanβ$ and high Higgs mass ranges, complementing the traditional searches for high mass resonances decaying into $τ$-lepton pairs which are instead sensitive to the large and moderate $\tanβ$ regions. The complementarity of the various channels in the probing of the complete $[\tanβ, M_A]$ MSSM parameter space at the previous and upcoming phases of the LHC is illustrated in a recently proposed simple and model independent approach for the Higgs sector, the $h$MSSM, that we also refine in this paper.

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arXiv2013

The post-Higgs MSSM scenario: Habemus MSSM?

We analyze the Minimal Supersymmetric extension of the Standard Model that we have after the discovery of the Higgs boson at the LHC, the hMSSM (habemus MSSM?), i.e. a model in which the lighter $h$ boson has a mass of approximately 125 GeV which, together with the non-observation of superparticles at the LHC, indicates that the SUSY-breaking scale $M_S$ is rather high, $M_S > 1$ TeV. We first demonstrate that the value $M_h \approx 125$ GeV fixes the dominant radiative corrections that enter the MSSM Higgs boson masses, leading to a Higgs sector that can be described, to a good approximation, by only two free parameters. In a second step, we consider the direct supersymmetric radiative corrections and show that, to a good approximation, the phenomenology of the lighter Higgs state can be described by its mass and three couplings: those to massive gauge bosons and to top and bottom quarks. We perform a fit of these couplings using the latest LHC data on the production and decay rates of the light $h$ boson and combine it with the limits from the negative search of the heavier $H,A$ and $H^\pm$ states, taking into account the current uncertainties.

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arXiv2013

The measurement of the Higgs self-coupling at the LHC: theoretical status

Now that the Higgs boson has been observed by the ATLAS and CMS experiments at the LHC, the next important step would be to measure accurately its properties to establish the details of the electroweak symmetry breaking mechanism. Among the measurements which need to be performed, the determination of the Higgs self-coupling in processes where the Higgs boson is produced in pairs is of utmost importance. In this paper, we discuss the various processes which allow for the measurement of the trilinear Higgs coupling: double Higgs production in the gluon fusion, vector boson fusion, double Higgs-strahlung and associated production with a top quark pair. We first evaluate the production cross sections for these processes at the LHC with center-of-mass energies ranging from the present $\sqrt s=8$ TeV to $\sqrt s=100$ TeV, and discuss their sensitivity to the trilinear Higgs coupling. We include the various higher order QCD radiative corrections, at next-to-leading order for gluon and vector boson fusion and at next-to-next-to-leading order for associated double Higgs production with a gauge boson. The theoretical uncertainties on these cross sections are estimated. Finally, we discuss the various channels which could allow for the detection of the double Higgs production signal at the LHC and the accuracy on the self-coupling that could be ultimately achieved.

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arXiv2012

Implications of a 125 GeV Higgs for supersymmetric models

Preliminary results of the search for a Standard Model like Higgs boson at the LHC with 5 fb-1 data have just been presented by the ATLAS and CMS collaborations and an excess of events at a mass of ~125 GeV has been reported. If this excess of events is confirmed by further searches with more data, it will have extremely important consequences in the context of supersymmetric extensions of the Standard Model and, in particular the minimal one, the MSSM. We show that for a standard-like Higgs boson with a mass 123 < M_h < 127 GeV, several unconstrained or constrained (i.e. with soft supersymmetry-breaking parameters unified at the high scale) MSSM scenarios would be excluded, while the parameters of some other scenarios would be severely restricted. Examples of constrained MSSM scenarios which would be disfavoured as they predict a too light Higgs particle are the minimal anomaly and gauge mediated supersymmetry breaking models. The gravity mediated constrained MSSM would still be viable, provided the scalar top quarks are heavy and their trilinear coupling large. Significant areas of the parameter space of models with heavy supersymmetric particles, such as split or high-scale supersymmetry, could also be excluded as, in turn, they generally predict a too heavy Higgs particle.

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