학술논문
First constraints on the $L_\mu-L_\tau$ explanation of the muon $g-2$ anomaly from NA64-$e$ at CERN
Document Type
Working Paper
Author
Andreev, Yu. M.; Antonov, A.; Banerjee, D.; Oberhauser, B. Banto; Bernhard, J.; Bisio, P.; Celentano, A.; Charitonidis, N.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A. V.; Donskov, S. V.; Dusaev, R. R.; Enik, T.; Frolov, V. N.; Gardikiotis, A.; Gninenko, S. N.; Hösgen, M.; Kachanov, V. A.; Kambar, Y.; Karneyeu, A. E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D. V.; Kirsanov, M. M.; Kolosov, V. N.; Gertsenberger, S. V.; Girod, S.; Kasianova, E. A.; Kramarenko, V. A.; Kravchuk, L. V.; Krasnikov, N. V.; Kuleshov, S. V.; Lyubovitskij, V. E.; Lysan, V.; Marini, A.; Marsicano, L.; Matveev, V. A.; Fredes, R. Mena; Yanssen, R. Mena; Bueno, L. Molina; Mongillo, M.; Peshekhonov, D. V.; Polyakov, V. A.; Radics, B.; Salamatin, K.; Samoylenko, V. D.; Sieber, H.; Shchukin, D.; Soto, O.; Tikhomirov, V. O.; Tlisova, I.; Toropin, A. N.; Tuzi, M.; Ulloa, P.; Volkov, P. V.; Volkov, V. Yu.; Voronchikhin, I. V.; Zamora-Saá, J.; Zhevlako, A. S.
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Subject
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Abstract
The inclusion of an additional $U(1)$ gauge $L_\mu-L_\tau$ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light $Z^\prime$ vector boson, with dominant coupling to $\mu$ and $\tau$ leptons and interacting with electrons via a loop mechanism. The $L_\mu-L_\tau$ model can also explain the Dark Matter relic abundance, by assuming that the $Z'$ boson acts as a ``portal'' to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the $Z'$ search performed by the NA64-$e$ experiment at CERN SPS, that collected $\sim 9\times10^{11}$ 100 GeV electrons impinging on an active thick target. Despite the suppressed $Z'$ production yield with an electron beam, NA64-$e$ provides the first accelerator-based results excluding the $g-2$ preferred band of the $Z'$ parameter space in the 1 keV $ < m_{Z'} \lesssim 2$ MeV range, in complementarity with the limits recently obtained by the NA64-$\mu$ experiment with a muon beam.
Comment: 15 pages, 5 figures. New version with extended exclusion limits down to 1 keV in Z' mass
Comment: 15 pages, 5 figures. New version with extended exclusion limits down to 1 keV in Z' mass