Eur. Phys. J. C (2018) 78:925
https://doi.org/10.1140/epjc/s10052-018-6413-9
Regular Article - Theoretical Physics
Muon conversion to electron in nuclei within the BLMSSM
Tao Guo
1,2,a
, Shu-Min Zhao
3,b
, Xing-Xing Dong
3,c
, Chun-Gui Duan
1,d
, Tai-Fu Feng
3,e
1
Department of Physics and Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024, China
2
College of Mathematics and Physics, Hebei GEO University, Shijiazhuang 050031, China
3
Department of Physics and Technology, Hebei University, Baoding 071002, China
Received: 9 August 2018 / Accepted: 1 November 2018 / Published online: 13 November 2018
© The Author(s) 2018
Abstract In a supersymmetric extension of the stan-
dard model with local gauged baryon and lepton numbers
(BLMSSM), there are new sources for lepton flavor violation,
because the right-handed neutrinos, new gauginos and Higgs
are introduced. We investigate muon conversion to electron in
nuclei within the BLMSSM in detail. The numerical results
indicate that the μ → e conversion rates in nuclei within the
BLMSSM can reach the experimental upper bound, which
may be detected in the future experiments.
1 Introduction
The observations of neutrino oscillations [1–3] imply that
neutrinos have tiny masses and are mixed [4–7], which have
demonstrated that lepton flavor in neutrino sector is not con-
served. Nevertheless, in the Standard Model (SM) with three
tiny massive neutrinos, the expected rates for the charged
lepton flavor violating (LFV) processes are very tiny [8–11].
Thus, Lepton-flavor violation is a window of new physics
beyond the SM. Among the various candidates for new
physics that produce potentially observable effects in LFV
processes, one of the most appealing model is supersym-
metric (SUSY) extension of the SM. Here, we can use the
neutrino oscillation experimental data to restrain the input
parameters in the new models. A neutral Higgs with mass
m
h
0
= 125.1 GeV reported by ATLAS [12] and CMS [13,14]
gives a strict constraint on relevant parameter space of the
model.
a
e-mail: sjzueguotao@163.com
b
e-mail: zhaosm@hbu.edu.com
c
e-mail: dxx_0304@163.com
d
e-mail: duancg@mail.hebtu.edu.cn
e
e-mail: fengtf@hbu.edu.cn
The present sensitivities of the μ − e conversion rates in
different nuclei [15–17] are collected here,
CR(μ → e : Au)<7 × 10
−13
,
CR(μ → e : Ti)<4.3 ×10
−12
,
CR(μ → e : Pb)<4.6 × 10
−11
. (1)
These processes have close relation with l
j
→ l
i
γ .Inthe
work [18], the μ → e conversion was studied in μνSSM.
For the models beyond SM, one can violate R parity with the
non-conservation of baryon number (B) or lepton number
(L)[19–22]. A minimal supersymmetric extension of the SM
with local gauged B and L(BLMSSM) was first proposed by
the author [23,24]. The local gauged B is used to explain the
matter-antimatter asymmetry in the universe. Right-handed
neutrinos in BLMSSM lead to three tiny neutrino masses
through the See-Saw mechanism and can account for the
neutrino oscillation experiments. So lepton number (L)is
expected to be broken spontaneously around TeV scale.
In BLMSSM, the lightest CP-even Higgs mass and the
decays h
0
→ γγ, h
0
→ ZZ(WW) were studied in the work
[25]. The neutron and lepton electric dipole moments(EDMs)
were researched in the CP-violating BLMSSM [26,27]. In
BLMSSM, there are also other works [28–30]. In this work,
we analyze the processes on muon conversion to electron in
nuclei within the BLMSSM. Compared with MSSM, there
are new sources to enlarge the processes via loop contribu-
tions. The new scores are produced from: (1) the coupling
of new neutralino(lepton neutralino)-slepton-lepton; (2) the
right-handed neutrinos mixing with left-handed neutrinos;
(3) the sneutrino sector is extended, whose mass squared
matrix is 6 ×6. In some parameter space of BLMSSM, large
corrections to the processes are obtained, and they can easily
exceed their experiment upper bounds. Therefore, to enhance
the processes on muon conversion to electron in nuclei is pos-
sible, and they may be measured in the near future.
After this introduction, we briefly summarize the main
ingredients of the BLMSSM, and show the needed mass
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