πe3 Form Factor f- Near the Mass Shell
The generalized Ward-Takahashi identity (gWTI) in the pion sector for broken isotopic symmetry is derived and used for the model-independent calculation of the longitudinal form factor f- of the πe3 vector vertex. The on-shell f- is found to be proportional to the mass difference of the pions and th...
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| Main Author: | |
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| Format: | Article |
| Language: | English |
| Published: |
Wiley
2015-01-01
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| Series: | Advances in High Energy Physics |
| Online Access: | http://dx.doi.org/10.1155/2015/656239 |
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| Summary: | The generalized Ward-Takahashi identity (gWTI) in the pion sector for broken isotopic symmetry is derived and used for the model-independent calculation of the longitudinal form factor f- of the πe3 vector vertex. The on-shell f- is found to be proportional to the mass difference of the pions and the difference between the vector isospin T=1 and scalar isospin T=2 pion radii. A numerical estimate of the form factor yields a value two times higher than the previous estimate from the quark model. Off-shell form factors are known to be ambiguous because of the gauge dependence and the freedom in the parameterization of the fields. The near-mass-shell f- appears to be an exception, allowing for experimental verification of the consequences of the gWTI. We calculate the near-mass-shell f- using the gWTI and dispersion techniques. The results are discussed in the context of the conservation of vector current (CVC) hypothesis. |
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| ISSN: | 1687-7357 1687-7365 |