Improved Bhabha cross section at LEP and the number of light neutrino species
In e+e− collisions, the integrated luminosity is generally measured from the rate of low-angle Bhabha interactions e+e−→e+e−. In the published LEP results, the inferred theoretical uncertainty of ±0.061% on the predicted rate is significantly larger than the reported experimental uncertainties. We p...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Elsevier
2020-04-01
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| Series: | Physics Letters B |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S0370269320301234 |
| _version_ | 1819100397575340032 |
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| author | Patrick Janot Stanisław Jadach |
| author_facet | Patrick Janot Stanisław Jadach |
| author_sort | Patrick Janot |
| collection | DOAJ |
| description | In e+e− collisions, the integrated luminosity is generally measured from the rate of low-angle Bhabha interactions e+e−→e+e−. In the published LEP results, the inferred theoretical uncertainty of ±0.061% on the predicted rate is significantly larger than the reported experimental uncertainties. We present an updated and more accurate prediction of the Bhabha cross section in this letter, which is found to reduce the Bhabha cross section by about 0.048%, and its uncertainty to ±0.037%. When accounted for, these changes modify the number of light neutrino species (and its accuracy), as determined from the LEP measurement of the hadronic cross section at the Z peak, to Nν=2.9963±0.0074. The 20-years-old 2σ tension with the Standard Model is gone. |
| first_indexed | 2024-12-22T01:02:08Z |
| format | Article |
| id | doaj.art-7e75b06d6adf4dd3b1e81a8e2b7b688c |
| institution | Directory Open Access Journal |
| issn | 0370-2693 |
| language | English |
| last_indexed | 2024-12-22T01:02:08Z |
| publishDate | 2020-04-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Physics Letters B |
| spelling | doaj.art-7e75b06d6adf4dd3b1e81a8e2b7b688c2022-12-21T18:44:11ZengElsevierPhysics Letters B0370-26932020-04-01803Improved Bhabha cross section at LEP and the number of light neutrino speciesPatrick Janot0Stanisław Jadach1CERN, EP Department, 1 Esplanade des Particules, CH-1217 Meyrin, Switzerland; Corresponding author.Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków, PolandIn e+e− collisions, the integrated luminosity is generally measured from the rate of low-angle Bhabha interactions e+e−→e+e−. In the published LEP results, the inferred theoretical uncertainty of ±0.061% on the predicted rate is significantly larger than the reported experimental uncertainties. We present an updated and more accurate prediction of the Bhabha cross section in this letter, which is found to reduce the Bhabha cross section by about 0.048%, and its uncertainty to ±0.037%. When accounted for, these changes modify the number of light neutrino species (and its accuracy), as determined from the LEP measurement of the hadronic cross section at the Z peak, to Nν=2.9963±0.0074. The 20-years-old 2σ tension with the Standard Model is gone.http://www.sciencedirect.com/science/article/pii/S0370269320301234 |
| spellingShingle | Patrick Janot Stanisław Jadach Improved Bhabha cross section at LEP and the number of light neutrino species Physics Letters B |
| title | Improved Bhabha cross section at LEP and the number of light neutrino species |
| title_full | Improved Bhabha cross section at LEP and the number of light neutrino species |
| title_fullStr | Improved Bhabha cross section at LEP and the number of light neutrino species |
| title_full_unstemmed | Improved Bhabha cross section at LEP and the number of light neutrino species |
| title_short | Improved Bhabha cross section at LEP and the number of light neutrino species |
| title_sort | improved bhabha cross section at lep and the number of light neutrino species |
| url | http://www.sciencedirect.com/science/article/pii/S0370269320301234 |
| work_keys_str_mv | AT patrickjanot improvedbhabhacrosssectionatlepandthenumberoflightneutrinospecies AT stanisławjadach improvedbhabhacrosssectionatlepandthenumberoflightneutrinospecies |