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Reexamining right-handed neutrino EFTs up to dimension six

Manimala Mitra, Sanjoy Mandal, Rojalin Padhan, Agnivo Sarkar, and Michael Spannowsky
Phys. Rev. D 106, 113008 – Published 29 December 2022
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  • INTRODUCTION
  • GENERAL SETUP
  • CONSTRAINTS ON RELEVANT NR-EFT…
  • POSSIBLE PRODUCTION MECHANISM
  • THE RIGHT-HANDED NEUTRINO DECAY MODES
  • PROSPECTIVE MULTILEPTON FINAL STATES
  • SUMMARY AND CONCLUSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    The gauge singlet right-handed neutrinos (RHNs) are essential fields in several neutrino mass models that explain the observed eV scale neutrino mass. We assume RHN field to be present in the vicinity of the electroweak scale and all the other possible beyond the Standard Model fields arise at high energy scale ≥Λ. In this scenario, the beyond the Standard Model physics can be described using effective field theory (EFT) where the set of canonical degrees of freedoms consists of both RHN and SM fields. EFT of this kind is usually dubbed as NR-EFT. We systematically construct relevant operators that can arise at dimension five and six while respecting underlying symmetry. To quantify the phenomenological implication of these EFT operators we calculate different couplings that involve RHN fields. We discuss the constraints on these EFT operators coming from different energy and precision frontier experiments. For pp, e−p and e+e− colliders, we identify various channels which crucially depends on these operators. We analytically evaluate the decay widths of RHN considering all relevant operators and highlight the differences that arise because of the EFT framework. Based upon the signal cross section we propose different multilepton channels to search for the RHN at 14 TeV LHC as well as future particle colliders.

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    • Received 21 November 2022
    • Accepted 2 December 2022

    DOI:https://doi.org/10.1103/PhysRevD.106.113008

    Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

    Published by the American Physical Society

    Physics Subject Headings (PhySH)

    1. Research Areas
    Effective field theoryParticle decaysParticle detection signaturesParticle interactionsParticle mixing & oscillationsParticle productionPhenomenology
    Particles & Fields

    Authors & Affiliations

    Manimala Mitra1,2,*, Sanjoy Mandal3,†, Rojalin Padhan1,2,4,‡, Agnivo Sarkar1,2,§, and Michael Spannowsky5,∥

    • 1Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005, India
    • 2Homi Bhabha National Institute, BARC Training School Complex, Anushakti Nagar, Mumbai 400094, India
    • 3Korea Institute for Advanced Study, Seoul 02455, Korea
    • 4Pittsburgh Particle Physics, Astrophysics, and Cosmology Center, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh 15260, USA
    • 5Institute for Particle Physics Phenomenology, Department of Physics, Durham University South Road, Durham DH1 3LE, United Kingdom

    • *manimala@iopb.res.in
    • †smandal@kias.re.kr
    • ‡rojalin.p@iopb.res.in
    • §agnivo.sarkar@iopb.res.in
    • ∥michael.spannowsky@durham.ac.uk

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    Issue

    Vol. 106, Iss. 11 — 1 December 2022

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    Images

    • Figure 1
      Figure 1

      Left panel: the Feynman diagram and the relevant operator for the process pp→NN/ν. Right panel: the variation of cross section for the process σ(gg→h→NN/ν) with MN for center-of-mass energy s=14  TeV and cutoff scale Λ=4  TeV. σ(gg→h→NN) is shown with the blue solid line and σ(gg→h→Nν) is shown with the red dashed-dot line. See text for details.

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    • Figure 2
      Figure 2

      Left panel: the Feynman diagram and the relevant operators for the process pp→NN/ν. Right panel: the variation of cross section with MN for center-of-mass energy s=14  TeV and cutoff scale Λ=4  TeV. σ(pp→NN) is shown with the blue solid line and σ(pp→Nν) is shown with the red dashed-dot line.

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    • Figure 3
      Figure 3

      Left panel: the Feynman diagram with the corresponding relevant EFT operators that contribute to the processes pp→NNjj and pp→Nνjj. Right panel: the variation of a cross section with MN. σ(pp→jjNN) is shown with the blue solid line and σ(pp→jjNν) is shown with the red dashed-dot line.

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    • Figure 4
      Figure 4

      Left panel shows the Feynman diagram with the relevant contributing EFT operators for the VBF process pp→jjNν/jjNN. Right panel shows the variation of cross section with RHN neutrino mass MN. The blue and red lines represent σ(pp→jjNN) and σ(pp→jjNν), respectively.

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    • Figure 5
      Figure 5

      Left panel shows the Feynman diagram with the relevant contributing operators for the VBF process pp→ℓ±Njj. The right panel stands for variation of σ(pp→W±jj→ℓ±Njj) with MN. The gray dot dashed, red dot dashed, orange dashed, and thick blue line stands for the contribution to this cross section coming from mixing only, mixing+OLNW, mixing+OHNe, and combining all the operators.

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    • Figure 6
      Figure 6

      (a) Feynman diagram and relevant operators for the process pp→W±→ℓ±N. (b) and (c) are variations of σ(pp→W±→ℓ±N) with MN for θ˜=10−6 and 10−3, respectively. In each panel the gray dot-dashed, red dot-dashed, orange dashed, and thick blue line stand for the contribution to this cross section coming from mixing only, mixing+OLNW, mixing+OHNe, and combining all the operators.

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    • Figure 7
      Figure 7

      Upper panel: the Feynman diagram and the relevant operators for the process e−p→jN. Bottom panel: variation of cross section for the process e−p→jN as a function of the sterile neutrino mass MN. The gray dot-dashed, red dotted, and blue thick lines stand for the contribution to the cross section coming from mixing only, mixing+OLNW+OHNe, and combination of all the operators, respectively.

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    • Figure 8
      Figure 8

      Upper panel: the Feynman diagram and the relevant operators for the process e−p→(j+3N)/(j+2N+ν). The cross section for the process e−p→j+3N. Bottom panel: variation of cross section corresponding to these processes as a function of the RHN mass MN. The blue thick and red dot-dashed lines signify the cross section corresponding to the process e−p→j+3N and e−p→j+2N+ν, respectively. The cross section is evaluated while taking into account all relevant operators.

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    • Figure 9
      Figure 9

      In the upper panel we present the Feynman diagram and the relevant operators for the process e+e−→NN/Nν. In the lower panel we show the cross section for the process e+e−→NN/Nν with s=91  GeV (c) and s=3  TeV (d). The blue thick line and red dot-dashed lines represent the process e+e−→NN and e+e−→Nν, respectively.

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    • Figure 10
      Figure 10

      In (a) we show the Feynman diagram and in (b) the cross section for the process e+e−→2N+2ν and e+e−→3N+ν. The blue thick and red dot dashed lines represent e+e−→2N+2ν and e+e−→3N+ν processes, respectively.

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    • Figure 11
      Figure 11

      The partial decay width correspond to Γ(N→ℓ±W∓) (left) and Γ(N→νh) (right) respectively. For both these cases the cutoff scale is set at 4 TeV. See text for details.

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    • Figure 12
      Figure 12

      The partial decay width correspond to Γ(N→νZ) (left) and Γ(N→νγ) (right), respectively. For both these cases the cutoff scale is set at 4 TeV. The value for αLNW and αLNB is consistent with the current experimental limits.

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    • Figure 13
      Figure 13

      The branching ratio corresponding to different two body decay modes for the MN mass range from 200 GeV to 1 TeV. In the left panel, we show branching ratio correspond to NR-EFT framework up to d=6 where the cutoff scale Λ is set to be 4 TeV and the mixing angle θ˜=10−3. In the right panel we show the branching ratio of possible two body decay modes if we only consider the renormalizable part of the Lagrangian. This plot correspond to both the mixing angle θ˜=10−3 and 10−6, respectively. See text for details.

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    • Figure 14
      Figure 14

      Partial decay width corresponds to the decay mode Γ(Ni→ℓjℓkνk;j≠k) for RHN mass ranging from 10 to 80 GeV. The orange dot-dashed, black dotted (red dashed), and gray dotted lines stand for the individual contribution coming from OHNe, LCC with θ˜=10−3 (θ˜=10−6), and OLNLe, respectively. The blue thick line denotes the total decay taking into account all the contributions. The left panel is for cutoff scale Λ=500  GeV and 4 TeV, respectively.

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    • Figure 15
      Figure 15

      Partial decay width corresponds to the decay mode Γ(Ni→νjℓkℓk;j=k) for RHN mass ranging from 10 to 80 GeV. The meaning of color code is same as in Fig. 14.

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    • Figure 16
      Figure 16

      Partial decay width corresponds to the decay mode Γ(Ni→νjℓkℓk;j≠k) for RHN mass ranging from 10 GeV to 80 GeV. The orange dot-dashed, black dotted (red dashed) line stands for the contribution coming from OLNLe and mixing angle θ˜=10−3 (θ˜=10−6). The blue thick line represents the total contribution with the assumption of θ˜=10−3. Left and right panel are for cutoff scales Λ=500  GeV and 4 TeV, respectively.

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    • Figure 17
      Figure 17

      Partial decay width corresponds to the decay mode Γ(Ni→ℓjuαd¯β;α≠β) for RHN masses ranging from 10 to 80 GeV. In each panel, the black dotted or red dashed, orange dot-dashed, and gray lines stand for the contribution coming from the mixing angle, OHNe, and from combination of four Fermi operator. The blue thick line represents the total contribution with the assumption of θ˜=10−3, and the left and right panels are for two different cutoff scale.

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    • Figure 18
      Figure 18

      Partial decay width corresponds to the decay mode Γ(Ni→νjuαu¯α) of RHN having mass in the range of 10 to 80 GeV. In each panel, the black dotted or red dashed and orange dot-dashed line stands for the contribution coming from the mixing angle and OQuNl. The blue thick line represents the total contribution with the assumption of θ˜=10−3, and the left and right panels are for two different cutoff scales.

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    • Figure 19
      Figure 19

      Partial decay width corresponds to the decay mode Γ(Ni→νjdαd¯α) of RHN mass ranging from 10 to 80 GeV. The color code is same as in Fig. 18 except the orange dot-dashed line now stands for four Fermi operators.

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    • Figure 20
      Figure 20

      Partial decay width corresponds to the decay mode Γ(Ni→νjνν¯) of RHN mass ranging from 10 to 80 GeV. The black dotted and red dashed lines stand for mixing angles θ˜=10−3 and θ˜=10−6, respectively.

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    • Figure 21
      Figure 21

      The total decay width correspond to RHN field where the MN is ranging from 10 to 80 GeV. The blue dashed and red dot-dashed line stands for the mixing angle θ˜=10−3 and θ˜=10−6, respectively. The black solid line represents the total decay width of the N field under full d=6 NR-EFT where the cutoff scale Λ is set to be 4 TeV. Similarly the brown dotted line stands for the total decay width of the N field with cutoff scale Λ=500  GeV.

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    • Figure 22
      Figure 22

      Upper panel: the branching ratios of RHN mass ranging from 10 to 80 GeV in various three body modes for the benchmark points BP1 (Λ=500  GeV) and BP2 (Λ=4  TeV). In both cases, we have considered the active sterile mixing angle θ˜=10−3. Lower panel: we calculate the branching ratio of the RHN mass ranging from 10 to 80 GeV in different three body decay modes while considering the renormalizable part of the Lagrangian.

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    • Figure 23
      Figure 23

      The left panel denotes the number of events that can be obtained at HL-LHC with c.m. energy 14 TeV and L=3000  fb−1. The right panel shows achievable number events that can be obtained at e+e− and e−p colliders for different c.m. energies.

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