[Paper Review] Probing Atomic Higgs-like Forces at the Precision Frontier

Cédric Delaunay, Roee Ozeri+2 more|arXiv (Cornell University)|Jan 19, 2016

Advanced Frequency and Time Standards9 citations

TL;DR

This paper proposes using high-precision isotope shift spectroscopy in atomic clocks to probe new fundamental forces mediated by Higgs-like particles or light scalar bosons. By analyzing non-linearities in King plots of isotope shifts across multiple transitions, it demonstrates that sub-Hz-level frequency measurements could detect Higgs-mediated forces between electrons and neutrons, potentially improving current bounds on light fermion couplings by orders of magnitude.

ABSTRACT

We propose a novel approach to probe new fundamental interactions using isotope shift spectroscopy in atomic clock transitions. As concrete toy example we focus on the Higgs boson couplings to the building blocks of matter: the electron and the up and down quarks. We show that the attractive Higgs force between nuclei and their bound electrons, that is poorly constrained, might induce effects that are larger than the current experimental sensitivities. More generically, we discuss how new interactions between the electron and the neutrons, mediated via light new degrees of freedom, may lead to measurable non-linearities in a King plot comparison between isotope shifts of two different transitions. Given state-of-the-art accuracy in frequency comparison, isotope shifts have the potential of being measured with sub-Hz accuracy, thus potentially enabling the improvement of current limits on new fundamental interactions. Candidate atomic system for this measurement require two different clock transitions and four zero nuclear spin isotopes. We identify several systems that satisfy this requirement and also briefly discuss existing measurements. We consider the size of the effect related to the Higgs force and the requirements for it to produce an observable signal.

Motivation & Objective

• To develop a novel low-energy precision test for new fundamental interactions mediated by light Higgs-like particles.
• To address the poorly constrained couplings of the Higgs boson to light fermions—particularly electrons and up/down quarks.
• To improve existing experimental bounds on Higgs-to-light-fermion couplings, which remain weak despite the Higgs boson's discovery.
• To identify atomic systems with multiple clock transitions and zero-spin isotopes suitable for detecting non-linearities in King plots.

Proposed method

• Utilizes isotope shift spectroscopy in atomic clocks with sub-Hz frequency resolution to probe new physics.
• Applies first-order perturbation theory to calculate Higgs-induced energy shifts in atomic levels via a Yukawa-type potential: VHiggs(r) = −(yeyA / 4π) (e−rmh / r).
• Models the effective nuclear coupling yA using quark-level couplings: yn,p ≈7.7yu + 9.4yd + 0.75ys + 2.6×10−4cg.
• Employs King plot analysis to detect non-linearities arising from new scalar interactions between electrons and neutrons.
• Considers both Higgs exchange and mixing with light scalar mediators (φ) that induce additional Yukawa potentials.
• Identifies candidate systems such as Yb+, Ca+, Sr+, and Hg with multiple clock transitions and four stable zero-spin isotopes.

Experimental results

Research questions

• RQ1 Can sub-Hz precision in isotope shift measurements detect deviations from linearity in King plots due to new electron-neutron forces?
• RQ2 What is the maximum observable Higgs force shift in atomic energy levels given current experimental frequency accuracy?
• RQ3 How do Higgs couplings to light quarks and electrons affect atomic transition frequencies, and can they be probed beyond LHC constraints?
• RQ4 Which atomic systems are optimal for detecting new physics via non-linear King plots in isotope shift spectroscopy?
• RQ5 To what extent can isotope shift measurements improve bounds on light fermion couplings to the Higgs or new scalar mediators?

Key findings

• Higgs-mediated forces between electrons and nuclei can induce energy shifts in atomic levels up to 106 times larger than the SM prediction if quark couplings saturate LHC constraints.
• The Higgs-induced frequency shift scales as δEHiggs ∝ −(yeyA / m2h) |ψ(0)|2 for s-states, with |ψ(0)|2/n3 representing the electron density at the nucleus.
• For Yb+, the Higgs shift is estimated at ~1 Hz, potentially observable with current sub-Hz frequency resolution.
• Non-linearities in King plots due to new scalar interactions (e.g., from Higgs mixing with light φ) could be detected at the O(1 Hz) level in systems like Ca+ and Sr+.
• The method can bound electron-neutron couplings with sensitivity comparable to or better than existing LHC and atomic physics constraints.
• Systems like Yb+, Ca+, Sr+, and Hg are identified as optimal candidates due to multiple clock transitions and four stable zero-spin isotopes.