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In stars, the fusion of $^{22}$Ne and $^4$He may produce either $^{25}$Mg,with the emission of a neutron, or $^{26}$Mg and a $\gamma$ ray. At hightemperature, the ($\alpha,n$) channel dominates, while at low temperature, itis energetically hampered. The rate of its competitor, the$^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg reaction, and, hence, the minimumtemperature for the ($\alpha,n$) dominance, are controlled by many nuclearresonances. The strengths of these resonances have hitherto been studied onlyindirectly. The present work aims to directly measure the total strength of theresonance at $E$_{r}$\,=\,$334$\,$keV (corresponding to$E$_{x}$\,=\,$10949$\,$keV in $^{26}$Mg). The data reported here have beenobtained using high intensity $^4$He$^+$ beam from the INFN LUNA 400 kVunderground accelerator, a windowless, recirculating, 99.9% isotopicallyenriched $^{22}$Ne gas target, and a 4$\pi$ bismuth germanate summing$\gamma$-ray detector. The ultra-low background rate of less than 0.5counts/day was determined using 67 days of no-beam data and 7 days of$^4$He$^+$ beam on an inert argon target. The new high-sensitivity setupallowed to determine the first direct upper limit of 4.0$\,\times\,$10$^{-11}$eV (at 90% confidence level) for the resonance strength. Finally, thesensitivity of this setup paves the way to study further$^{22}$Ne($\alpha$,$\gamma$)$^{26}$Mg resonances at higher energy.

First direct limit on the 334 keV resonance strength in the $^{22}$Ne({\alpha},{\gamma})$^{26}$Mg reaction