We present a new technique, “tau polarimetry,” for measuring the longitudinal beam polarization present in an e+e− collider through the analysis of e+e− → τ+τ− events. By exploiting the sensitivity of τ decay kinematics to the longitudinal polarization of the beams, we demonstrate that the longitudinal polarization can be measured with a 3 per mil systematic uncertainty at the interaction point using a technique that is independent of spin and beam transport modeling. Using 424.2 pm 1.8 fb−1 of BABAR data at sqrt(s) = 10.58 GeV, the average longitudinal polarization of the PEP-II e+e- collider has been measured to be = 0.0035 pm 0.0024stat pm 0.0029sys. The systematic uncertainty studies are described in detail, which can serve as a guide for future applications of tau polarimetry. A proposed e− beam longitudinal polarization upgrade to the SuperKEKB e+e− collider would benefit from this technique.
Precision e− beam polarimetry at an e+e− B factory using tau-pair events
Calabrese, R.;Garzia, I.;Luppi, E.;
2023
Abstract
We present a new technique, “tau polarimetry,” for measuring the longitudinal beam polarization present in an e+e− collider through the analysis of e+e− → τ+τ− events. By exploiting the sensitivity of τ decay kinematics to the longitudinal polarization of the beams, we demonstrate that the longitudinal polarization can be measured with a 3 per mil systematic uncertainty at the interaction point using a technique that is independent of spin and beam transport modeling. Using 424.2 pm 1.8 fb−1 of BABAR data at sqrt(s) = 10.58 GeV, the average longitudinal polarization of the PEP-II e+e- collider has been measured to be = 0.0035 pm 0.0024stat pm 0.0029sys. The systematic uncertainty studies are described in detail, which can serve as a guide for future applications of tau polarimetry. A proposed e− beam longitudinal polarization upgrade to the SuperKEKB e+e− collider would benefit from this technique.File | Dimensione | Formato | |
---|---|---|---|
PhysRevD.108.092001-2.pdf
accesso aperto
Descrizione: Full text editoriale
Tipologia:
Full text (versione editoriale)
Licenza:
Creative commons
Dimensione
6.15 MB
Formato
Adobe PDF
|
6.15 MB | Adobe PDF | Visualizza/Apri |
I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.