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Optimal Calibration-Free Observable for the Nucleon-Coupling Ratio in a Dual-Alkali Comagnetometer for Dark Matter Searches
Authors:
Yossi Rosenzweig,
Yevgeny Kats,
Eli Sarid,
Menachem Givon,
Yonathan Japha,
Ron Folman
Abstract:
A dual-alkali single-cell $^{87}$Rb-$^{39}$K-$^{3}$He comagnetometer can read an axionlike dark matter signal through two optical-rotation channels, encoding the ratio $\mathcal{R}=ξ_n/ξ_p$ of the field's neutron and proton spin couplings in their relative response. The inter-species phase difference $Δ\varphi$ has been proposed as a calibration-free readout that is sensitive to $\mathcal{R}$. Tre…
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A dual-alkali single-cell $^{87}$Rb-$^{39}$K-$^{3}$He comagnetometer can read an axionlike dark matter signal through two optical-rotation channels, encoding the ratio $\mathcal{R}=ξ_n/ξ_p$ of the field's neutron and proton spin couplings in their relative response. The inter-species phase difference $Δ\varphi$ has been proposed as a calibration-free readout that is sensitive to $\mathcal{R}$. Treating the extraction of $\mathcal{R}$ as a statistical estimation problem, we show that the optimal observable is the complex inter-channel ratio, which splits into $Δ\varphi$ and an amplitude ratio, of which only $Δ\varphi$ is insensitive to the relative gain and hence calibration-free. For our choice of comagnetometer parameters, above $\sim\!100$ Hz the phase difference alone captures most of the coupling-ratio information. At lower frequencies $Δ\varphi$ is not near-sufficient: there the amplitude ratio would improve the precision on $\mathcal{R}$ by a factor of $\gtrsim2$ below $\sim\!40$ Hz. Recovering that information, however, requires the relative gain to be known sufficiently accurately, so $Δ\varphi$ stays the robust observable even where it is not the optimal one.
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Submitted 7 August, 2026;
originally announced August 2026.
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Correlated comagnetometry for precision measurements
Authors:
Yossi Rosenzweig,
Yevgeny Kats,
Eli Sarid,
Menachem Givon,
Yonathan Japha,
Ron Folman
Abstract:
Magnetometers are among the most widely used probes in science and technology. Comagnetometers increase sensitivity by self-cancellation of magnetic noise, but only at low frequencies. We suggest a correlated measurement of two alkali species in one cell to cancel the magnetic background also at high frequencies. The inter-species phase difference of the light-matter interaction response function…
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Magnetometers are among the most widely used probes in science and technology. Comagnetometers increase sensitivity by self-cancellation of magnetic noise, but only at low frequencies. We suggest a correlated measurement of two alkali species in one cell to cancel the magnetic background also at high frequencies. The inter-species phase difference of the light-matter interaction response function is found to be calibration free and insensitive to common-mode intensity noise. Utilizing a dark-matter signal as a testcase, the method achieves a thirtyfold background suppression, raising the signal-to-noise ratio by an order of magnitude or more, depending on the coupling to the different subatomic particles. We show that the method also provides model differentiation. The higher sensitivity and model differentiation open a path to novel probes for precision measurements in general and exotic fields in particular.
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Submitted 20 July, 2026;
originally announced July 2026.
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Hadronic Calorimeter Shower Size: Challenges and Opportunities for Jet Substructure in the Superboosted Regime
Authors:
Shikma Bressler,
Thomas Flacke,
Yevgeny Kats,
Seung J. Lee,
Gilad Perez
Abstract:
Hadrons have finite interaction size with dense material, a basic feature common to known forms of hadronic calorimeters (HCAL). We argue that substructure variables cannot use HCAL information to access the microscopic nature of jets much narrower than the hadronic shower size, which we call superboosted massive jets. It implies that roughly 15% of their transverse energy profile remains inaccess…
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Hadrons have finite interaction size with dense material, a basic feature common to known forms of hadronic calorimeters (HCAL). We argue that substructure variables cannot use HCAL information to access the microscopic nature of jets much narrower than the hadronic shower size, which we call superboosted massive jets. It implies that roughly 15% of their transverse energy profile remains inaccessible due to the presence of long-lived neutral hadrons. This part of the jet substructure is also subject to order-one fluctuations. We demonstrate that the effects of the fluctuations are not reduced when a global correction to jet variables is applied. The above leads to fundamental limitations in the ability to extract intrinsic information from jets in the superboosted regime. The neutral fraction of a jet is correlated with its flavor. This leads to an interesting and possibly useful difference between superboosted W/Z/h/t jets and their corresponding backgrounds. The QCD jets that form the background to the signal superboosted jets might also be qualitatively different in their substructure as their mass might lie at or below the Sudakov mass peak. Finally, we introduce a set of zero-cone longitudinal jet substructure variables and show that while they carry information that might be useful in certain situations, they are not in general sensitive to the jet substructure.
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Submitted 15 March, 2016; v1 submitted 8 June, 2015;
originally announced June 2015.