Bonn 2020 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 15: Search for new particles I

T 15.4: Vortrag

Montag, 30. März 2020, 17:15–17:30, H-HS XVI

Observation of an excess at 30 GeV in the opposite sign di-muon spectra of Zb b + X events recorded by the ALEPH experiment at LEP — •Arno Heister — privat

The re-analysis of the archived data recorded at the Z0 resonance by the ALEPH experiment at LEP during the years 1992-1995 shows an excess in the opposite sign di-muon mass spectra at 30.40 ± 0.46 GeV in events containing b quarks. The excess has a natural width of 1.78 ± 1.14 GeV.

The di-muon excess has a local significance around 5 σ (Zasym), depending on the background model used. The significances for background models based on a kernel density approximation stay close to 3 σ (Zfreqlee), when including a look elsewhere effect. Another method to obtain a significance value results in at least 2.6 σ (ZBi). A compatible, but smaller excess is visible in the opposite di-electron mass spectrum as well.

Several experiments have data samples that include the di-lepton mass region discussed here. The excess described in the paper arXiv:1610.06536 may be present in data of other experiments at LEP, the Tevatron and the LHC. Former members of the L3 collaboration as well as the ATLAS and CMS collaborations have published the result of their searches for this excess. The L3 data and the CMS data shows a noteworthy excess. The ATLAS experiment did not find anything in its data, yet.

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