Proton-number fluctuations in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>2.4</mml:mn></mml:mrow><mml:mo> </mml:mo><mml:mi>GeV</mml:mi><mml:mo> </mml:mo><mml:mi>Au</mml:mi><mml:mo> </mml:mo><mml:mo>+</mml:mo><mml:mo> </mml:mo><mml:mi>Au</mml:mi></mml:math> collisions studied with the High-Acceptance DiElectron Spectrometer (HADES)

The QCD critical endpoint (CEP) is a very distinct feature of the phase diagram of nuclear matter, but it can presently not be located from first-principle calculations; experimental observations are needed to constrain its position. The HADES Collaboration at GSI measured cumulants and correlators for net-proton number fluctuations, the most important observable so far to search for the CEP. This extends experimental results below the lowest beam energies available at RHIC and will be useful to discern the possibility of a critical point in the QCD phase diagram.