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Corfu Summer Institute School and Workshops on Elementary Particle Physics and Gravity (CORFU)

Experimental constrains on the Continuous Spontaneous Localization model from spontaneous radiation emission

Kristian Piscicchia, Angelo Bassi, Catalina Curceanu, Sandro Donadi, Andreas Pichler, R. Del Grande

Published Aug 22, 2018• 0 citations
Publisher

Abstract

The work presented in this paper aimed to obtain new, more stringent, limits on the parameters of the Continuous Spontaneous Localization collapse model. The result is accomplished by performing a Bayesian analysis of the X-ray emission data collected by the IGEX collaboration, compared with the spontaneous photon emission which is predicted by collapse models. The most stringent limits on the collapse rate $\lambda$ and the correlation length $r_C$ of the CSL model are obtained , with respect to any other method, over a broad range of the parameters space.

DOI
10.22323/1.318.0201

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The work presented in this paper aimed to obtain new, more stringent, limits on the parameters of the Continuous Spontaneous Localization collapse model. The result is accomplished by performing a Bayesian analysis of the X-ray emission data collected by the IGEX collaboration, compared with the spontaneous photon emission which is predicted by collapse models. The most stringent limits on the collapse rate λ\lambdaλ and the correlation length rCr_CrC​ of the CSL model are obtained , with respect to any other method, over a broad range of the parameters space.
In this paper new upper limits on the parameters of the Continuous Spontaneous Localization (CSL) collapse model are extracted. To this end the X-ray emission data collected by the IGEX collaboration are analyzed and compared with the spectrum of the spontaneous photon emission process predicted by collapse models. This study allows to obtain the most stringent limits within a relevant range of the CSL model parameters, with respect to any other method. The collapse rate λ\lambdaλ and the correlation length rCr_CrC​ are mapped, thus allowing to exclude a broad range of the parameter space.
Collapse models consist in dynamical reformulations of the standard quantum mechanics aiming to solve the measurement problem. The standard Schrödinger dynamics is modified with the introduction of nonlinear and stochastic terms, which induce the wave function collapse in space. Collapse models predict slight deviations from the standard quantum mechanics predictions, in particular the emission of a “spontaneous radiation”, which we explored to set the most stringent limits on the collapse models parameters in a broad range. To this end, the X-ray emission data collected by the IGEX collaboration are analyzed and compared with the spectrum of the spontaneous photon emission process predicted by the theories. The results of the data analyses, and the ongoing experimental efforts will be presented.
Collapse models introduce stochastic and nonlinear modifications in the quantum dynamics, predicting observable effects, such as spontaneous radiation from charged particles, which can be used to constrain their parameters. Recently, attention has focused on the 1-100 keV energy range, where the wavelength of the emitted photons becomes comparable to atomic dimensions, making the emission sensitive to atomic structure and leading to model-dependent behaviors that enable their discrimination. Here, we derive a general expression for the spontaneous emission rate for arbitrary noise, providing a framework that systematically incorporates the atomic structure through the radial distribution of the emitters, modulated by the specific collapse model. The formalism recovers previous results in the appropriate limits and naturally includes new low-energy effects, such as cancellation mechanisms arising from charge correlations. We evaluate the rates for germanium and xenon within the Diósi-Penrose and Continuous Spontaneous Localization models, showing how these correlations modify the predicted emission rates. This approach provides a unified framework to account for atomic effects and enables more robust, material-dependent experimental constraints on collapse model parameters.
We have analyzed recently published XENONnT data for the spontaneous X-ray emission signature predicted by the objective wave function collapse model of quantum mechanics. With extremely low background and large exposure, XENONnT data can be used to completely exclude the theoretically predicted collapse parameters of continuous spontaneous localization~(CSL) model suggested by Ghirardi, Rhimini and Weber. Our result strongly suggests that the simplest version of the CSL model with the white-noise assumption is unlikely to provide answers to the long-standing measurement problem of quantum mechanics and motivates pursuits of more complex versions of the theory. If the result is interpreted with the Diósi-Penrose gravitational wave function collapse model, our limit improves the previous limit by a factor of 5.7. Detailed analysis using more precise background modelling can further improve the limits.
The article reviews our recent experimental results on the Continuous Spontaneous Localization (CSL) model and on the gravity related collapse model developed by Diósi and Penrose (DP). These models of dynamical reduction of the wave function consist in non-linear and stochastic modifications of the Schröedinger equation, which lead to a progressive breakdown of the superposition principle, as the size of the system increases. We performed a high sensitivity survey of the spontaneous radiation phenomenon, predicted by the collapse models, in a dedicated experiment operated in the extremely low background of the Gran Sasso underground National Laboratory of INFN in Italy. Our studies set the strongest bounds on the CSL parameters, in a broad region of the parameters space, and rule out the DP in its present formulation.
Standard implementations of Continuous Spontaneous Localization (CSL) assume white noise with an infinite bandwidth, leading to a divergent heating rate and the prediction of unobserved spontaneous X-ray emission (the “Heating Catastrophe”). This paper presents a complete mathematical resolution using a relativistic coloured noise field with a Lorentz invariant spectral density D(k) = λσ2/[1 + (kμkμL2c)n]. We derive the exact suppression factor S for the spontaneous emission rate. For a correlation time τc ≈ 10−12 s, the high frequency spectral tail scales as ω−2n. We demonstrate that for the X-ray regime (ω ∼ 1018Hz), the per-mode suppression is ∼ 10−12, moderated by phase space integration to a total factor of S ≈ 10−8. This reduces the predicted radiation rate below the sensitivity floors of IGEX and CUORE, resolving the tension with experimental data while preserving macroscopic collapse.