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A confirmation of the long-standing muon g − 2 discrepancy requires both experimental and theoretical progress. On the theory side, the hadronic corrections are under close scrutiny, as they induce the leading uncertainty of the Standard Model prediction. Recently, the MUonE experiment has been proposed at CERN to provide a new determination of the leading hadronic contribution to the muon g − 2 via the measurement of the differential cross section of muon-electron scattering. The precision expected at this experiment raises the question whether possible new physics (NP) could affect its measurements. We address this issue studying possible NP signals in muon-electron collisions due to heavy or light mediators, depending on whether their mass is higher or lower than Oð1 GeVÞ. We analyze the former in a modelindependent way via an effective field theory approach, whereas for the latter we focus on scenarios with light scalar and vector bosons. Using existing experimental bounds, we show that possible NP effects in muon-electron collisions are expected to lie below MUonE's sensitivity. This result confirms and reinforces the physics case of the MUonE proposal.

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“…where Γ μ ¼ m 5 μ G 2 F =192π 3 ≈ 3 × 10 −10 eV is the muon decay rate. The evaluation of the (singlet) matrix element gives [56]…”

Section: E Heavy Np and Lfv Effectsmentioning

confidence: 99%

New physics at the MUonE experiment at CERN

2020

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“…Usually these experiments apply only when the leptonic mixing matrix is diagonal [14]. Also, in models with extended Higgs sector some not unrealist situations could exist in which scalar bosons contribution to muonium to antimuonium conversion is not negligible [15]. Therefore, in this work we assume a more interesting lower limit on the double charged bilepton mass, ∼ 350 GeV, which is accessible to next generation of accelerators and is compatible with others low energy bounds [9,16].…”

Section: Introductionmentioning

confidence: 99%

3-3-1 exotic quark search at CERN LEPII and LHC

1999

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The 3-3-1 electroweak model is the simplest chiral extension of the standard model which predicts single and double charged bileptons and exotic quarks carrying -4/3 and 5/3 units of the positron charge. In this paper we study the possibilities of the production and decay of one of these exotic quarks at CERN LEPII-LHC collider. For typical vector bilepton, exotic quark masses and mixing angles we obtained between 20 and 750 events per year. Angular distributions are also presented.

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“…The interactions in Eqs. (2) and (7) involve different mixing matrices, hence, if all bosons have masses of the same order of magnitude, as it is in fact expected in the 331 model (see below), we can have some cancellations among all the contributions. Notice that those matrices are unitary only when G ′ is real, like the matrices in Eq.…”

mentioning

confidence: 69%

“…In this case the neutral currents given in Eq. (7) are diagonal and there is no FCNC in the lepton sector and all the sextet-lepton couplings are proportional to K RL = √ 2m l /v S where m l is the lepton mass. If v S is of the order of 100 GeV the main contribution to the M → M conversion comes from the interaction in Eq.…”

mentioning

confidence: 99%

Remark on the muonium to antimuonium conversion in a 3-3-1 model

Pleitez

2000

Phys. Rev. D

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Here we analyze the relation between the search for muonium to antimuonium conversion and the 3-3-1 model with doubly charged bileptons. We show that the constraint on the mass of the vector bilepton obtained by experimental data can be evaded even in the minimal version of the model since there are other contributions to that conversion. We also discuss the condition for which the experimental data constraint is valid.PACS number͑s͒: 11.30. Fs, 11.30.Hv, 12.60.Ϫi, 36.10.Dr Recently a new upper limit for the spontaneous transition of muonium (M ϵ ϩ e Ϫ ) to antimuonium (M ϵ Ϫ e ϩ ) has been obtained ͓1͔. This implies constraints upon the models that induce the M →M transition. One of them is the 3-3-1 model proposed some years ago ͓2͔. Here we would like to discuss the conditions in which this constraint can be evaded even in the context of the minimal version of the model ͑minimal in the sense that no new symmetries or fields are introduced͒.In that model in the lepton sector the charged physical mass eigenstates ͑unprimed fields͒ are related to the weak eigenstates ͑primed fields͒ through unitary transformationsT . It means that the doubly charged vector bilepton, U ϩϩ , interacts with the charged leptons through the current given bywhere g 3l is the SU(3) coupling constant and K is the unitary matrix defined as KϭE R T E L in the basis in which the interactions with the WIn the theoretical calculations of the M →M transition induced by a doubly charged vector bilepton so far only the case Kϭ1 has been considered ͓4͔. Although this is a valid simplification, it does not represent the most general case in the minimal 3-3-1 model. In fact, in that model in the quark sector all left-handed mixing matrices survive in different places of the Lagrangian density ͓5͔. In the lepton sector both left-and right-handed mixing matrices survive in the interactions with the doubly charged vector bilepton as in Eq. ͑2͒ and also with neutral, doubly and singly charged scalars ͑see below͒. Hence, these mixing matrices such as K in Eq. ͑2͒ have the same status as the Kobayashi-Maskawa mixing matrix in the context of the standard model in the sense that they must be determined by experiment. In Ref.͓1͔ it is recognized that their bound is valid only for the flavor diagonal bilepton gauge boson case, i.e., Kϭ1. If nondiagonal interactions, like in Eq. ͑2͒, are assumed, the new upper limit on the conversion probability in the M →M system impliesIf ͉K ͉͉K ee ͉Ϸ0.70, we get a lower bound of 600 GeV for the doubly charged bilepton which is compatible with the upper bound obtained by theoretical arguments ͓6͔.The following is more important. In addition to the contribution of the vector bileptons there are also the doubly charged and the neutral scalar ones. To consider only the vector bileptons is also a valid approximation since all the lepton-scalar couplings can be small if all vacuum expectation values ͑VEVs͒, except the one controlling the SU(3) breaking, are of the order of the electroweak scale and if there is no flavor chan...

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μ+e−⇆
W.-S. Hou
¹
,
Gwo-Guang Wong
²

Cited by 19 publications

References 30 publications

New physics at the MUonE experiment at CERN

New physics at the MUonE experiment at CERN

3-3-1 exotic quark search at CERN LEPII and LHC

Remark on the muonium to antimuonium conversion in a 3-3-1 model

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μ+e−⇆W.-S. Hou1, Gwo-Guang Wong2

Cited by 19 publications

References 30 publications

New physics at the MUonE experiment at CERN

New physics at the MUonE experiment at CERN

3-3-1 exotic quark search at CERN LEPII and LHC

Remark on the muonium to antimuonium conversion in a 3-3-1 model

Contact Info

Product

Resources

About

μ+e−⇆
W.-S. Hou
¹
,
Gwo-Guang Wong
²