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(-) -> tau(+)tau(-) events. By exploiting the sensitivity of tau 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 +/- 1.8 fb(-1) of BABAR data at root s = 10.58 GeV, the average longitudinal polarization of the PEP-II e(+)e(-) collider has been measured to be < P > = 0.0035 +/- 0.0024(stat) +/- 0.0029(sys). 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

Batignani, G.;Bettarini, S.;Casarosa, G.;Forti, F.;Giorgi, M.  A.;Paoloni, E.;Rizzo, G.;
2023-01-01

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(-) -> tau(+)tau(-) events. By exploiting the sensitivity of tau 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 +/- 1.8 fb(-1) of BABAR data at root s = 10.58 GeV, the average longitudinal polarization of the PEP-II e(+)e(-) collider has been measured to be < P > = 0.0035 +/- 0.0024(stat) +/- 0.0029(sys). 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.
2023
Lees, J.  P.; Poireau, V.; Tisserand, V.; Grauges, E.; Palano, A.; Eigen, G.; Brown, D.  N.; Kolomensky, Yu.  G.; Fritsch, M.; Koch, H.; Cheaib, R.; H...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/1241752
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