Dark scent

The hand of creation by John Byrne from Green Lantern: Ganthet's Tale

The XENON1T experiment at Gran Sasso's laboratories in Italy is a liquid xenon detector designed for serach of the mysterious dark matter. About one year ago researchers observed an excess of events: 53 more than the 232 predicted⁽¹⁾.
There are several explanations: an unexpected noise' source; the passage of some axions, an hypothetical particle predicted by Roberto Peccei and Helen Quinn in 1977; some neutrinos that interact with matter in a new way.
Or dark matter's traces⁽²⁾. There are two new articles suggesting this; in particular the second suggests that the detected excess in XENON1T is dued by chameleons⁽³⁾.
The chameleon is an(other) hypothetical particle proposed in 2003 by Justin Khoury and Amanda Weltman, that couples to matter more weakly than gravity, and so a candidate for dark matter. It has a variable mass, so the hypothetical fifth force mediated by the chameleons can evade the constraints deduced by experiments on the equivalence principle. In this way chameleons could drive the observed acceleration of the universe's expansion, but it's very difficult to verify experimentally.

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1. XENON collaboration. (2020). Excess electronic recoil events in XENON1T. Physical Review D, 102(7). doi:10.1103/PhysRevD.102.072004 ↩︎
2. Aboubrahim, A., Klasen, M., & Nath, P. (2021). Xenon-1T excess as a possible signal of a sub-GeV hidden sector dark matter. Journal of High Energy Physics, 2021(2), 1-21. doi:10.1007/JHEP02(2021)229 ↩︎
3. Vagnozzi, S., Visinelli, L., Brax, P., Davis, A. C., & Sakstein, J. (2021). Direct detection of dark energy: the XENON1T excess and future prospects. Physical Review D, 104(6). doi:10.1103/PhysRevD.104.063023 ↩︎

Experimental problems in OPERA

It seems that are some experimental problems in OPERA:

The OPERA Collaboration, by continuing its campaign of verifications on the neutrino velocity measurement, has identified two issues that could significantly affect the reported result. The first one is linked to the oscillator used to produce the events time-stamps in between the GPS synchronizations. The second point is related to the connection of the optical fiber bringing the external GPS signal to the OPERA master clock.
These two issues can modify the neutrino time of flight in opposite directions. While continuing our investigations, in order to unambiguously quantify the effect on the observed result, the Collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam will be available in 2012. An extensive report on the above mentioned verifications and results will be shortly made available to the scientific committees and agencies.

I remember that alxo BOREXINO, an other experiment at Gran Sasso Laboratories, will try to measure neutrino's speed. Indeed the experimental mistake could preduce a higher velocity than the previous collected data.

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