Double Higgs boson production and Higgs self-coupling extraction at CLIC
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Regular Article - Experimental Physics
Double Higgs boson production and Higgs self-coupling extraction at CLIC Philipp Roloff1 , Ulrike Schnoor1,a , Rosa Simoniello1 , Boruo Xu2 1 2
CERN, Geneva, Switzerland University of Cambridge, Cambridge, UK
Received: 17 December 2019 / Accepted: 18 October 2020 © The Author(s) 2020
Abstract The Compact Linear Collider (CLIC) is a future electron–positron collider that will allow measurements of the trilinear Higgs self-coupling in double Higgs boson events produced at its high-energy stages with collision ener√ gies from s = 1.4 to 3 TeV. The sensitivity to the Higgs self-coupling is driven by the measurements of the cross section and the invariant mass distribution of the Higgs¯ boson pair in the W-boson fusion process, e+ e− → HHν ν. It is enhanced by including the cross-section measurement of ZHH production at 1.4 TeV. The expected sensitivity of CLIC for Higgs pair production through W-boson fusion is ∗ using full ¯ b¯ and bbWW ¯ studied for the decay channels bbb √ detector simulation including all relevant backgrounds at s = 1.4 TeV with an integrated luminosity of L = 2.5 ab−1 and at √ s = 3 TeV with L = 5 ab−1 . Combining e+ e− → HHν ν¯ and ZHH cross-section measurements at 1.4 TeV with differential measurements in e+ e− → HHν ν¯ events at 3 TeV, CLIC will be able to measure the trilinear Higgs self-coupling with a relative uncertainty of −8% and +11% at 68% C.L., assuming the Standard Model. In addition, prospects for simultaneous constraints on the trilinear Higgs self-coupling and the Higgs-gauge coupling HHWW are derived based on the HHν ν¯ measurement.
1 Introduction The discovery of the Higgs boson [1,2] has initiated an era of investigations of its properties and of the nature of the mechanism that breaks the electroweak symmetry. Besides its mass and width, the properties of interest include the couplings of the Higgs boson to other Standard Model (SM) and hypothetical non-SM particles as well as the coupling to itself. While the couplings to other SM particles illustrate the way these particles obtain masses in the Higgs mechanism, the a e-mail:
[email protected] (corresponding author)
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self-coupling parameter determines the shape of the Higgs potential which has implications for the vacuum metastability, the hierarchy problem, as well as the electroweak phase transition and baryogenesis. In the Standard Model, the Higgs potential for the Higgs field φ is described by V (φ) = μ2 φ † φ +
λ2 † 2 (φ φ) , 2
(1)
where μ is proportional to the Higgs boson mass and λ is the Higgs self-coupling. This implies a fixed relation m 2H = λv between the mass and the self-coupling, with the vacuum expectation value v. In the interaction Lagrangian, this potential leads to a trilinear self-coupling gHHH which is proportional to λ. A deviation of the Higgs potential from the SM would directly point to new physics, for example in the context of baryogenesis: Indeed, one of the conditions for electroweak baryogenesis is the presence of a str
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