C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits
Abstract Hadronisation corrections are crucial in extractions of the strong coupling constant ( $$\alpha _s$$ α s ) from event-shape distributions at lepton colliders. Although their dynamics cannot be understood rigorously using perturbative methods, their dominant effect on physical observables ca...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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SpringerOpen
2021-02-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | https://doi.org/10.1140/epjc/s10052-021-08941-z |
| _version_ | 1818325778822070272 |
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| author | Gionata Luisoni Pier Francesco Monni Gavin P. Salam |
| author_facet | Gionata Luisoni Pier Francesco Monni Gavin P. Salam |
| author_sort | Gionata Luisoni |
| collection | DOAJ |
| description | Abstract Hadronisation corrections are crucial in extractions of the strong coupling constant ( $$\alpha _s$$ α s ) from event-shape distributions at lepton colliders. Although their dynamics cannot be understood rigorously using perturbative methods, their dominant effect on physical observables can be estimated in singular configurations sensitive to the emission of soft radiation. The differential distributions of some event-shape variables, notably the C parameter, feature two such singular points. We analytically compute the leading non-perturbative correction in the symmetric three-jet limit for the C parameter, and find that it differs by more than a factor of two from the known result in the two-jet limit. We estimate the impact of this result on strong coupling extractions, considering a range of functions to interpolate the hadronisation correction in the region between the 2 and 3-jet limits. Fitting data from ALEPH and JADE, we find that most interpolation choices increase the extracted $$\alpha _{s}$$ α s , with effects of up to $$4\%$$ 4 % relative to standard fits. This brings a new perspective on the long-standing discrepancy between certain event-shape $$\alpha _s$$ α s fits and the world average. |
| first_indexed | 2024-12-13T11:49:54Z |
| format | Article |
| id | doaj.art-dd0b520ad3404c70ad549b1ade9766fd |
| institution | Directory Open Access Journal |
| issn | 1434-6044 1434-6052 |
| language | English |
| last_indexed | 2024-12-13T11:49:54Z |
| publishDate | 2021-02-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | European Physical Journal C: Particles and Fields |
| spelling | doaj.art-dd0b520ad3404c70ad549b1ade9766fd2022-12-21T23:47:23ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60441434-60522021-02-0181211110.1140/epjc/s10052-021-08941-zC-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fitsGionata Luisoni0Pier Francesco Monni1Gavin P. Salam2CERN, Theoretical Physics DepartmentCERN, Theoretical Physics DepartmentRudolf Peierls Centre for Theoretical Physics, Clarendon Laboratory, University of OxfordAbstract Hadronisation corrections are crucial in extractions of the strong coupling constant ( $$\alpha _s$$ α s ) from event-shape distributions at lepton colliders. Although their dynamics cannot be understood rigorously using perturbative methods, their dominant effect on physical observables can be estimated in singular configurations sensitive to the emission of soft radiation. The differential distributions of some event-shape variables, notably the C parameter, feature two such singular points. We analytically compute the leading non-perturbative correction in the symmetric three-jet limit for the C parameter, and find that it differs by more than a factor of two from the known result in the two-jet limit. We estimate the impact of this result on strong coupling extractions, considering a range of functions to interpolate the hadronisation correction in the region between the 2 and 3-jet limits. Fitting data from ALEPH and JADE, we find that most interpolation choices increase the extracted $$\alpha _{s}$$ α s , with effects of up to $$4\%$$ 4 % relative to standard fits. This brings a new perspective on the long-standing discrepancy between certain event-shape $$\alpha _s$$ α s fits and the world average.https://doi.org/10.1140/epjc/s10052-021-08941-z |
| spellingShingle | Gionata Luisoni Pier Francesco Monni Gavin P. Salam C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits European Physical Journal C: Particles and Fields |
| title | C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits |
| title_full | C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits |
| title_fullStr | C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits |
| title_full_unstemmed | C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits |
| title_short | C-parameter hadronisation in the symmetric 3-jet limit and impact on $$\alpha _s$$ α s fits |
| title_sort | c parameter hadronisation in the symmetric 3 jet limit and impact on alpha s α s fits |
| url | https://doi.org/10.1140/epjc/s10052-021-08941-z |
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