Precision measurement of the mass of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:math>lepton

Ablikim, M.; Ачасов, М. Н.; Ai, X.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, J. V.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Braun, S.; Briere, R. A.; Cai, H.; Cai, Xinxia; Çakır, O.; Calcaterra, A.; Cao, G. F.; Çetin, S. A.; Chang, J. F.; Chelkov, G. A.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D. V.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; Ding, W. M.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fan, J.; Fang, J.; Su, Fang; Fang, Y.; Fava, L.; Feng, C.; Fu, C. D.; Fuks, O.; Gao, Q.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Tingting; Guo, Y. P.; Han, Y. L.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Chen, Hu; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, G. M.; Huang, G. S.; Huang, Hongxia; Huang, J. S.; Huang, L. Q.; Huang, X. T.; Huang, Y.; Hussain, T.; Ji, C. S.; Ji, Q. P.; Ji, Q.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, L. W.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Kalantar‐Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Kloss, B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupść, A.; Lai, W.; Lange, J. S.; Lara, M.; Larin, P.; Leyhe, M.; Li, C. H.; Li, Cheng; Li, Cui; Li, D.; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, Lei; Li, P. R.; Li, Q. J.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liu, Han; Liang, Y. F.; Liang, Y. T.; Lin, D. X.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. P.; Liu, K.; Liu, K. Y.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lou, X.; Lu, G. R.; Lü, H. J.; Lü, H.; Lu, J. G.; Lü, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; C., F.; L., H.; M., Q.; Ma, S.; Ma, Tao; Y., X.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Jiang, Min; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Moeini, H.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pelizaeus, M.; Peng, H.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Qi, M.; Qian, S. J.; Qiao, C. F.; Liu, Qin; Qin, X. S.; Qin, Yao; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, W. M.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Toth, D.; Ullrich, M.; Uman, I.; Varner, G.; Wang, B.; Wang, D.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q. J.; Wang, S. G.; Wang, W.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Werner, M.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, N.; Wang, Zhi; Xia, L.; Xia, Y.; Xiao, D.; Xiao, Z. J.; Xie, Y.; Xiu, Q. L.; Xu, G. F.; Li, Xu; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, L.; Yang, Y.; Yang, Yifan; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yu, Shiqi; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zang, S. L.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. B.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, S. H.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Liu, Zhao; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q.; Zhao, S. J.; Zhao, T. C.; Zhao, X.; Zhao, Y. B.; Zhao, Z.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y.; Zhong, B.; Li, Zhou; Zhou, Xiang; Zhou, X.; Zhou, X. R.; Zhou, Xingyu; Zhu, K.; Zhu, X.; Zhu, Y.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.

doi:10.1103/physrevd.90.012001

Cited by 31 publications

(15 citation statements)

References 30 publications

Supporting

Mentioning

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Section: Motivationmentioning

confidence: 92%

“…Among the most precise tests is a comparison of decay rates of K mesons, K − → e − ν e versus K − → µ − ν µ [4] [5]. Furthermore, taking into account precision measurements of the tau and muon masses and lifetimes, the measured decay rates τ − → e − ν e ν τ and µ − → e − ν e ν µ , have confirmed the equality of the weak coupling strengths of the tau and muon [3].However, recent studies of semileptonic decays of B mesons of the form B → D ( * ) − ν , with = e, µ, or τ , have resulted in observations that seem to challenge lepton universality. These weak decays are well understood in the framework of the SM, and therefore offer a unique opportunity to search for unknown processes, for instance non-SM couplings to yet undiscovered charged partners of the Higgs boson [6] or hypothetical leptoquarks [7].…”

mentioning

confidence: 92%

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A challenge to lepton universality in B meson decays

Lüth

2018

Hyperfine Interact

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One of the key assumptions of the Standard Model of fundamental particles is that the interactions of the charged leptons, namely electrons, muons, and taus, differ only because of their different masses. While precision tests have not revealed any definite violation of this assumption, recent studies of B meson decays involving the higher-mass tau lepton have resulted in observations that challenge lepton universality at the level of four standard deviations. A confirmation of these results would point to new particles or interactions, and could have profound implications for our understanding of particle physics. MotivationMore than 70 years of particle physics research have led to an elegant and concise theory of particle interactions at the sub-nuclear level, commonly referred to as the Standard Model (SM) [1,2]. In the framework of the SM of particle physics the fundamental building blocks, quarks and leptons, are each grouped in three generations of two members each. The three charged leptons, the electron (e − ), the muon (µ − ) and the tau (τ − ) are each paired with a very low mass, electrically neutral neutrino, ν e , ν µ , and ν τ . The three generations are ordered by the mass m of the charged lepton ranging from 0.511 MeV for e ± to 105 MeV for µ ± , and 1,777 MeV for τ ± [3]. Charged leptons participate in electromagnetic and weak, whereas neutrinos only undergo weak interaction. The SM assumes that these interactions of the charged and neutral leptons are universal, i.e., the same for the three generations.Precision tests of lepton universality have been performed by many experiments. To date no definite violation of lepton universality has been observed. Among the most precise tests is a comparison of decay rates of K mesons, K − → e − ν e versus K − → µ − ν µ [4] [5]. Furthermore, taking into account precision measurements of the tau and muon masses and lifetimes, the measured decay rates τ − → e − ν e ν τ and µ − → e − ν e ν µ , have confirmed the equality of the weak coupling strengths of the tau and muon [3].However, recent studies of semileptonic decays of B mesons of the form B → D ( * ) − ν , with = e, µ, or τ , have resulted in observations that seem to challenge lepton universality. These weak decays are well understood in the framework of the SM, and therefore offer a unique opportunity to search for unknown processes, for instance non-SM couplings to yet undiscovered charged partners of the Higgs boson [6] or hypothetical leptoquarks [7]. Such searches have been performed on data collected by three different experiments, BABAR and Belle at e + e − colliders in the U.S.A. and in Japan, and LHCb at the proton-proton (pp) collider at CERN in Europe.In the following, details of the measurements, their results and preliminary studies to understand the observed effects will be presented, along with prospects for improved sensitivity and complementary measurements. This article is partially based on an earlier review with the same title [8].

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Section: Motivationmentioning

confidence: 92%

mentioning

confidence: 92%

A challenge to lepton universality in B meson decays

Lüth

2018

Hyperfine Interact

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“…Precise measurements of the τ mass and production cross section were performed by the BESIII collaboration [81]. Doing a scan in the energy of the e + e − beam around the τ threshold made it possible to measure the τ τ production cross section at the sub-percent level.…”

Section: Tau Physicsmentioning

confidence: 99%

Flavor gauge models below the Fermi scale

Babu

Friedland

Machado

et al. 2017

J. High Energ. Phys.

120

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The mass and weak interaction eigenstates for the quarks of the third generation are very well aligned, an empirical fact for which the Standard Model offers no explanation. We explore the possibility that this alignment is due to an additional gauge symmetry in the third generation. Specifically, we construct and analyze an explicit, renormalizable model with a gauge boson, X, corresponding to the B − L symmetry of the third family. Having a relatively light (in the MeV to multi-GeV range), flavor-nonuniversal gauge boson results in a variety of constraints from different sources. By systematically analyzing 20 different constraints, we identify the most sensitive probes: kaon, B + , D + and Upsilon decays, D −D 0 mixing, atomic parity violation, and neutrino scattering and oscillations. For the new gauge coupling g X in the range (10 −2 -10 −4 ) the model is shown to be consistent with the data. Possible ways of testing the model in b physics, top and Z decays, direct collider production and neutrino oscillation experiments, where one can observe nonstandard matter effects, are outlined. The choice of leptons to carry the new force is ambiguous, resulting in additional phenomenological implications, such as nonuniversality in semileptonic bottom decays. The proposed framework provides interesting connections between neutrino oscillations, flavor and collider physics.

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“…By a fit to the τ pair cross section data near threshold, shown in the left plot of Fig. 3, the mass of the τ lepton was determined to be (17):…”

Section: Beam Energy Measurement Systemmentioning

confidence: 99%

“…Cross section measurements are shown with error bars; the smooth curve is the fit. (Right plot) Comparison of the measured ⌧ mass with those from the PDG (17). The green band corresponds to the 1 limit of the BESIII measurement.…”

Section: Systematic Error Estimationmentioning

confidence: 99%

Physics Accomplishments and Future Prospects of the BES Experiments at the Beijing Electron--Positron Collider

Briere

Harris

Mitchell

2016

Annu. Rev. Nucl. Part. Sci.

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The cornerstone of the Chinese experimental particle physics program consists of a series of experiments performed in the tau-charm energy region. China began building e + e − colliders at the Institute for High Energy Physics in Beijing more than three decades ago. Beijing Electron Spectrometer, BES, is the common root name for the particle physics detectors operated at these machines. The development of the BES program is summarized and highlights of the physics results across several topical areas are presented.

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Precision measurement of the mass of theτlepton

Cited by 31 publications

References 30 publications

A challenge to lepton universality in B meson decays

A challenge to lepton universality in B meson decays

Flavor gauge models below the Fermi scale

Physics Accomplishments and Future Prospects of the BES Experiments at the Beijing Electron--Positron Collider

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