Measurement of the τ electric dipole moment using longitudinal polarization of e+e beams

Ananthanarayan, B. ; Rindani, Saurabh D. (1995) Measurement of the τ electric dipole moment using longitudinal polarization of e+e beams Physical Review D - Particles, Fields, Gravitation and Cosmology, 51 (11). pp. 5996-6007. ISSN 1550-7998

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Certain CP-odd momentum correlations in the production and subsequent decay of τ pairs in e+e collisions are enhanced significantly when the e+ and e beams are longitudinally polarized. These may be used to probe the real and imaginary parts of dτγ, the electric dipole moment of the τ. Closed-form expressions for these "vector correlations" and the standard deviation of the operators defining them due to standard model interactions are presented for the two-body final states of τ decays. If 42% average polarization of each beam is achieved, as proposed for the τ-charm factories, with equal integrated luminosities for each sign of polarization and a total yield of 2×107 τ+τ pairs, it is possible to attain sensitivities for ||δ Redτγ|| of 8×10−19, 1×10−19, 1×10−19e cm, respectively, and for ||δ Imdτγ|| of 4×10−14, 6×10−15, 5×10−16e cm, respectively, at the three operating center-of-mass energies of 3.67, 4.25, and 10.58 GeV. These bounds emerge when the effects of a possible weak dipole form factor dτZ are negligible as is the case when it is of the same order of magnitude as dτZ. Furthermore, in such a polarization experiment where different polarizations are possible, a model-independent disentangling of their individual effects is possible, and a technique to achieve this is described. A strong longitudinal polarization physics program at the τ-charm factory appears warranted.

Item Type:Article
Source:Copyright of this article belongs to The American Physical Society.
ID Code:43593
Deposited On:14 Jun 2011 09:51
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