Quantum Universe
Cluster of ExcellenceQuantum Universe
During the development of the analysis, the physicists consulted with their theory colleagues in the Quantum Universe cluster to ensure that the theoretically most interesting signals are targeted. Particular emphasis was given to events where the Z boson decays into a pair of leptons (electrons or muons) and the hypothetical H boson decays into a pair of top quarks, which are then seen in the detector as six jets (clusters of particles flying close by). “After quite a lot of hard work preparing everything in much detail, we were very excited to see what Nature had placed in our measured events,” said Daniel Hundhausen, a PhD student at Universität Hamburg, who worked on this analysis. “This particular decay chain is named ‘the smoking gun’ by the theorists because it offers significant promise in corroborating the 2HDM predictions,” added Daniel. A signal would show up as a deviation from the well-known SM ‘backgrounds’ in the distributions of the A boson mass and of the Z transverse momentum. The red line in Fig. 2 shows an example of such an hypothetical deviation.
The researchers carefully scrutinized the data, searching for deviations from the SM predictions, but no ‘anomalous excess’ was found. “We did not find any statistically significant BSM signal and, therefore, we could conclude that the A and H bosons – if they exist – do not have mass values inside certain ranges,” explained Matteo Bonanomi, a postdoctoral researcher at Universität Hamburg and also a member of the analysis team. Those ‘excluded ranges’ are shown in Fig. 3. The results do not confirm an earlier excess seen by the ATLAS Collaboration [2].