Limits on heavy neutral lepton mixing parameters

Limits on $\vert {{\mathit U}}_{{{\mathit \mu}} {{\mathit x}}}\vert ^2$

INSPIRE   PDGID:
S077A01
Quoted limits are either the best limit near the kinematic threshold of the experiment, or a characteristic value in the mass range of the experimental sensitivity
VALUE CL% DOCUMENT ID TECN  COMMENT
$<5 \times 10^{-7}$ 95 1
AAD
2023AO
 ATLS ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}\sim{}3 - 15$ GeV, ${{\mathit p}}{{\mathit p}}$ at 13 TeV
$<0.1$ 95 2
AAD
2023CE
 ATLS Near ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $0.1 - 2$ TeV
$<0.1$ 95 3
TUMASYAN
2023AC
 CMS Near ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $0.1 - 3$ TeV
$<5 \times 10^{-9}$ 90 4
ABRATENKO
2022A
 MBNE Near ${\mathit m}_{{{\mathit K}}}–{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<3 \times 10^{-7}$ 95 5
TUMASYAN
2022AD
 CMS ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}\sim{}8 - 14$ GeV, ${{\mathit p}}{{\mathit p}}$ at 13 TeV
$<1 \times 10^{-3}$ 95 6
AAIJ
2021AA
 LHCB ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}\sim{}5 - 50$ GeV, ${{\mathit p}}{{\mathit p}}$ at 7, 8 TeV
$<2 \times 10^{-4}$ 95 7
AAIJ
2021AA
 LHCB ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}\sim{}5 - 50$ GeV, ${{\mathit p}}{{\mathit p}}$ at 7, 8 TeV
$<5 \times 10^{-9}$ 90 8, 9
CORTINA-GIL
2021
NA62 Near ${\mathit m}_{{{\mathit K}}}–{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<0.02$ 90 10
PRIM
2020
BELL ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ 1 GeV
$<2 \times 10^{-5}$ 95 11
AAD
2019F
 ATLS ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $10 - 50$ GeV
$<2 \times 10^{-6}$ 95 12
AAD
2019F
 ATLS ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ 10 GeV
$<1 \times 10^{-9}$ 90 13
ABE
2019B
 T2K Near ${\mathit m}_{{{\mathit K}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<5 \times 10^{-6}$ 90 14, 15
AGUILAR-AREVA..
2019B
 PIEN ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $16 - 30$ MeV
$<1 \times 10^{-5}$ 90 15
AGUILAR-AREVA..
2019B
 PIEN Near ${\mathit m}_{{{\mathit \pi}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<3 \times 10^{-7}$ 90 8
CORTINA-GIL
2018
NA62 ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $250 - 350$ MeV
$<3 \times 10^{-6}$ 90 8
LAZZERONI
2017A
 NA62 Near ${\mathit m}_{{{\mathit K}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<0.05$ 90 16
PARK
2016
BELL ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ 1.4 GeV
$<1 \times 10^{-8}$ 90 8
ARTAMONOV
2015A
 B949 ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $200 - 300$ MeV
$<3 \times 10^{-5}$ 90 17
LIVENTSEV
2013
BELL Near ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $2 - 2.5$ GeV
$<2.0 \times 10^{-8}$ 95 18
DAUM
2000
KARM ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ = 33.905 MeV
$<8 \times 10^{-8}$ 90 19
VAITAITIS
1999
CCFR Near ${\mathit m}_{{{\mathit K}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<6 \times 10^{-8}$ 90 20
VAITAITIS
1999
CCFR Near ${\mathit m}_{{{\mathit D}_{{{s}}}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<3 \times 10^{-5}$ 95 21
ABREU
1997I
 DLPH ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $6 - 50$ GeV
$<2 \times 10^{-5}$ 95 22
ABREU
1997I
 DLPH Near ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ 3.5 GeV
$<3 \times 10^{-5}$ 90 23
VILAIN
1995C
 CHM2 Near ${\mathit m}_{{{\mathit K}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<3 \times 10^{-8}$ 24, 25
BERNARDI
1988
CNTR Near ${\mathit m}_{{{\mathit \mu}}}+{\mathit m}_{{{\mathit \pi}}}$ kin. thres.
$<2 \times 10^{-9}$ 25, 26
BERNARDI
1988
CNTR Near ${\mathit m}_{{{\mathit K}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<1 \times 10^{-7}$ 90 27
DORENBOSCH
1986
CHRM Near ${\mathit m}_{{{\mathit D}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
$<1 \times 10^{-7}$ 90 28
COOPER-SARKAR
1985
BEBC Near ${\mathit m}_{{{\mathit D}}}−{\mathit m}_{{{\mathit \mu}}}$ kin. thres.
• • We do not use the following data for averages, fits, limits, etc. • •
$<1 \times 10^{-7}$ 90 29
ABRATENKO
2020
MBNE Superseded by ABRATENKO 2022A
1  AAD 2023AO search for ${{\mathit W}}$ $\rightarrow$ ${{\mathit \nu}_{{{x}}}}{{\mathit \mu}}$, for both Majorana and Dirac HNL scenarios. Also consider scenarios involving multiflavor mixing, with correspondingly weaker limits.
2  AAD 2023CE search for Majorana HNLs via vector boson fusion ${{\mathit W}^{\pm}}$ ${{\mathit W}^{\pm}}$ $\rightarrow$ ${{\mathit \mu}^{\pm}}{{\mathit \mu}^{\pm}}$. Limits set in a ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ mass range from 50 GeV up to 20 TeV, using the Phenomenological Type-I Seesaw model as a benchmark scenario.
3  TUMASYAN 2023AC search for Majorana HNLs via vector boson fusion ${{\mathit W}^{\pm}}$ ${{\mathit W}^{\pm}}$ $\rightarrow$ ${{\mathit \mu}^{\pm}}{{\mathit \mu}^{\pm}}$. Limits set in a ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ mass range from 50 GeV up to 25 TeV.
4  ABRATENKO 2022A search for ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{\mp}}{{\mathit \pi}^{\pm}}$, in the mass range ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $246 - 385$ MeV. Also considers limits from ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \pi}^{+}}$ only, for the case of a Dirac HNL.
5  TUMASYAN 2022AD search for ${{\mathit W}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit \nu}_{{{x}}}}$, ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit e}}{{\mathit \nu}_{{{e}}}}$ and set limits for Dirac and Majorana Heavy Neutral Leptons. The data correspond to an integrated luminosity of 138 fb${}^{-1}$.
6  Limit from prompt lepton number conserving ${{\mathit W}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit \mu}}{{\mathit j}}$ search.
7  Limit from prompt lepton number violating ${{\mathit W}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit \mu}}{{\mathit j}}$ search .
8  Search for ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$.
9  Assumes a lifetime exceeding 50 ns, and searches over ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ range $200 - 384$ MeV.
10  Search for ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$ in the mass range ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $0 - 1.5$ GeV .
11  Limit from prompt lepton number violating trilepton search.
12  Limit from displaced lepton violating or conserving trilepton searches.
13  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ decay through ${{\mathit U}}_{{{\mathit \mu}} {{\mathit x}}}$. ABE 2019B also considers bounds on $\vert {{\mathit U}}_{{{\mathit \ell}} {{\mathit x}}}{{\mathit U}}_{{{\mathit \ell}^{\,'}} {{\mathit x}}}\vert $ for combinations of lepton flavors in the ${{\mathit \nu}_{{{x}}}}$ decay final state.
14  Limit requires muon kinetic energy $>$ 1.2 MeV.
15  Search for ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$.
16  PARK 2016 quotes an approximate limit B( ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$) $<$ $3 \times 10^{-6}$ in the mass range ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $0.2 - 1.4$ GeV.
17  Search for ${{\mathit B}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$.
18  DAUM 2000 quotes a branching ratio bound B( ${{\mathit \pi}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$) $<$ $6.0 \times 10^{-10}$ at 95$\%$ CL.
19  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$.
20  ${{\mathit D}_{{{s}}}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}}{{\mathit X}}$.
21  Search for prompt ${{\mathit \nu}_{{{x}}}}$ decay signatures.
22  Search for displaced ${{\mathit \nu}_{{{x}}}}$ decay signatures.
23  Search for Heavy Neutral Leptons produced by neutral current muon neutrino interactions, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}{{\mathit \nu}_{{{\mu}}}}$.
24  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ decay through ${{\mathit U}}_{{{\mathit \mu}} {{\mathit x}}}$ and ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $<$ ${\mathit m}_{{{\mathit \mu}}}$ + ${\mathit m}_{{{\mathit \pi}}}$.
25  BERNARDI 1988 also considers bounds on $\vert {{\mathit U}}_{{{\mathit e}} {{\mathit x}}}{{\mathit U}}_{{{\mathit \mu}} {{\mathit x}}}\vert $.
26  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \pi}^{+}}$.
27  ${{\mathit D}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$.
28  ${{\mathit D}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \ell}^{+}}{{\mathit \nu}_{{{{{\mathit \ell}}}}}}$ or ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \pi}^{+}}$.
29  ${{\mathit K}^{+}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \nu}_{{{x}}}}$, with ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{-}}{{\mathit \pi}^{+}}$, in the mass range ${\mathit m}_{{{\mathit \nu}_{{{x}}}}}$ $\sim{}$ $260 - 385$ MeV. ABRATENKO 2020 also considers ${{\mathit \nu}_{{{x}}}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \pi}^{-}}$ for the case of a Majorana HNL.
References