Observation of an excess at 30 GeV in the opposite sign di-muon spectra of ${\rm Z}^{0} \to b\overline{ b} + {\rm X}$ events recorded by the ALEPH experiment at LEP
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| Format: | Preprint |
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2016
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| _version_ | 1866912053474623488 |
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| author | Heister, Arno |
| author_facet | Heister, Arno |
| contents | The re-analysis of the archived data recorded at the ${\rm Z}^{0}$ 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 $\pm$ 0.46 GeV in events containing b quarks. The excess has a natural width of 1.78 $\pm$ 1.14 GeV.
The di-muon excess has a local significance around $5\,σ$ ($Z_{\rm asym}$), depending on the background model used. The significances for background models based on a kernel density approximation stay close to $3\,σ$ ($Z_{\rm freq,\,lee}$), when including a look elsewhere effect. Another method to obtain a significance value results in at least $2.6\,σ$ ($Z_{\rm Bi}$). A compatible, but smaller excess is visible in the opposite di-electron mass spectrum as well.
This paper uses the data collected by the ALEPH experiment in the years 1992-1995, which have been archived to allow their use for physics analyses after the closure of the collaboration. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_1610_06536 |
| institution | arXiv |
| publishDate | 2016 |
| record_format | arxiv |
| spellingShingle | Observation of an excess at 30 GeV in the opposite sign di-muon spectra of ${\rm Z}^{0} \to b\overline{ b} + {\rm X}$ events recorded by the ALEPH experiment at LEP Heister, Arno High Energy Physics - Experiment The re-analysis of the archived data recorded at the ${\rm Z}^{0}$ 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 $\pm$ 0.46 GeV in events containing b quarks. The excess has a natural width of 1.78 $\pm$ 1.14 GeV. The di-muon excess has a local significance around $5\,σ$ ($Z_{\rm asym}$), depending on the background model used. The significances for background models based on a kernel density approximation stay close to $3\,σ$ ($Z_{\rm freq,\,lee}$), when including a look elsewhere effect. Another method to obtain a significance value results in at least $2.6\,σ$ ($Z_{\rm Bi}$). A compatible, but smaller excess is visible in the opposite di-electron mass spectrum as well. This paper uses the data collected by the ALEPH experiment in the years 1992-1995, which have been archived to allow their use for physics analyses after the closure of the collaboration. |
| title | Observation of an excess at 30 GeV in the opposite sign di-muon spectra of ${\rm Z}^{0} \to b\overline{ b} + {\rm X}$ events recorded by the ALEPH experiment at LEP |
| topic | High Energy Physics - Experiment |
| url | https://arxiv.org/abs/1610.06536 |