Some highlights of research

Variable stars.

In the publication "Shifting Milestones of Natural Sciences:  The Ancient Egyptian Discovery of Algol's Period Confirmed" (2015, PLOS ONE 10(12), e0144140), Jetsu and Porceddu showed that the Ancient Egyptians discovered the first variable star and its period about three thousand years before the modern astronomers. Their statistical study of the Ancient Egyptian Cairo Calendar revealed that Algol represented Horus -- a god and king.


One page of the Cairo Calendar. Inside the superimposed rectangle is the hieratic writing for the word Horus.

Solar wind.

A study on unravelling the large-scale solar wind drives of Van Allen radiation belt enhancements published in Geophysical Research Letters. Presents a new framework to study dramatic variations in "killer electron" fluxes in these belts during space weather storms, in particular using recent Van Allen Probe measurements.

ALICE - Precision measurement of the mass difference between light nuclei and anti-nuclei.

On the 17th of August 2015, the ALICE experiment published a precise measurement of the difference between ratios of the mass and electric charge of light nuclei and antinuclei. The result, published in Nature Physics, confirms a fundamental symmetry of nature, so-called CPT symmetry, to an unprecedented precision for light nuclei. The measurements are based on the ALICE experiment's abilities to track and identify particles produced in high-energy heavy-ion collisions at the LHC.


Measurements of energy loss in the time-projection chamber enable the ALICE experiment to identify antinuclei (upper curves on the left) and nuclei (upper curves on the right) produced in the lead-ion collisions at the LHC.

Joining forces to test the Higgs boson's spin and parity.

The Tevatron experiments, CDF and DZero, found evidence for a Higgs boson in 2012, looking at events in which two bottom-flavoured jets recoiled from a vector boson - either Z or a W. The challenge is to see to what extent the observed Higgs boson candidates follow the Standard model predictions, and whether the Higgses observed at the Tevatron represent a mixture of the same states that were in 2013 observed at the LHC.

At the Tevatron, the Higgs boson's properties were found to be consistent with those predicted for the Standard Model Higgs boson. A way to test between the models of the Higgs boson's spin and parity is based on the following: a Higgs boson with an exotic spin and parity woud be produced with more energy than the SM version. CDF and DZero looked at the energies and angles of particles produced in Higgs boson events to check. But most of events at the Tevatron are non-Higgs-boson background events, so a lot of hard work went in to test the models. Both DZero and CDF modified their Higgs boson analyses for the new particles. If they are present in addition to the SM Higgs boson, or if they replace it entirely. Neither experiment found evidence for the exotic states, and the data prefer the SM interpretation.

But a much stronger statement can be made when CDF and DZero join forces and combine their results T. Aaltonen et al., [CDF and D0 Collaborations], Phys. Rev. Lett. 114 (2015) 15, 151802, using the same techniques used in the SM Higgs search combinations. The signal strength of exotic Higgs bosons in the JP = 0- and 2+ states is no more than 0.36 times that predicted for the SM Higgs boson. Given a choice between the SM Higgs boson, which has JP = 0+, and one of the two exotic models replacing it with the same signal strength, the Tevatron data disfavours the exotic models with a significance of 5.0 standard deviations for 0- and 4.9 standard deviations for 2+.