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Long-lived light mediators from Higgs boson decay at HL-LHC and FCC-hh, and a proposal of dedicated long-lived particle detectors for FCC-hh

Biplob Bhattacherjee, Shigeki Matsumoto, and Rhitaja Sengupta
Phys. Rev. D 106, 095018 – Published 15 November 2022
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  • INTRODUCTION
  • THE SCALAR MEDIATOR
  • THE LONG-LIVED MEDIATOR PARTICLE AT THE…
  • THE LONG-LIVED MEDIATOR PARTICLE AT THE…
  • SUMMARY AND CONCLUSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    We study the pair production of the long-lived mediator particles from the decay of the standard model Higgs boson and their subsequent decay into standard model particles. We compute the projected sensitivity, both model independently and with a minimal model, of using the muon spectrometer of the CMS detector at the HL-LHC experiment for ggF, VBF, and VH production modes of the Higgs boson and various decay modes of the mediator particle, along with dedicated detectors for long-lived particle searches like CODEX-b and MATHUSLA. Subsequently, we study the improvement with the FCC-hh detector at the 100 TeV collider experiment for such long-lived mediators, again focusing on the muon spectrometer. We propose dedicated long-lived particle detector designs for the 100 TeV collider experiment, detector for long-lived particles at high energy of 100 TeV, and study their sensitivities.

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    • Received 7 February 2022
    • Accepted 18 October 2022

    DOI:https://doi.org/10.1103/PhysRevD.106.095018

    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
    Extensions of Higgs sectorParticle dark matter
    Particles & Fields

    Authors & Affiliations

    Biplob Bhattacherjee1,*, Shigeki Matsumoto2,†, and Rhitaja Sengupta1,‡

    • 1Centre for High Energy Physics, Indian Institute of Science, Bengaluru 560012, India
    • 2Kavli IPMU (WPI), UTIAS, University of Tokyo, Kashiwa, Chiba 277-8583, Japan

    • *biplob@iisc.ac.in
    • †shigeki.matsumoto@ipmu.jp
    • ‡rhitaja@iisc.ac.in

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    Issue

    Vol. 106, Iss. 9 — 1 November 2022

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    • Figure 1
      Figure 1

      Normalized distributions of pT (left panel) and η (right panel) of the SM Higgs boson produced through the ggF, VBF, and VH production channels at s=14  TeV.

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    • Figure 2
      Figure 2

      Comparison of the pT (top panels) and η (bottom panels) distributions of the SM Higgs boson produced via the ggF (left panels), VBF (center panels), and VH (right panels) production channels at the s=14 and 100 TeV collider experiments.

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    • Figure 3
      Figure 3

      Normalized pT (top panels) and η (bottom panels) distributions of the mediator particle from the decay of the Higgs boson, for three values of the mediator mass (mϕ=500  MeV, 5 and 50 GeV), along with the latter for comparison in the ggF (left panels), VBF (center panels), and VH (right panels) production channels at s=14  TeV.

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    • Figure 4
      Figure 4

      The mean proper decay length of the mediator particle, cτϕ, predicted in the minimal model in Eq. (2.1) and the branching fraction of each decay mode, Br(ϕ→SM SM), contributing to the length are show in the left and right panels, respectively, assuming that the mediator does not decay into dark sector particles. In the left panel, the decay lengths with the mixing angles sinθ=10−2, 10−5, and 10−8 are shown. In the right panel, only the branching fractions that are analyzed in the following sections are shown.

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    • Figure 5
      Figure 5

      Normalized histograms of the boost factor distribution (top panels) and the decay length in the laboratory frame (bottom panels) of the mediator particle from the SM Higgs boson decay, for mϕ=500  MeV, 5 GeV, 50 GeV, and cτϕ=0.1  m (solid lines) and 1000 m (dashed lines), in the ggF (left), VBF (center), and VH (right) production modes of the Higgs boson production at s=14  TeV. The histogram of the exponential distribution, exp(−d/cτϕ), for the two different decay lengths are shown in gray.

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    • Figure 6
      Figure 6

      Transverse projection of the propagation of a muon pair in the magnetic field of the CMS detector, where the pair is assumed to be from the decay of the LLP (mϕ=250  MeV) that is pair produced from the Higgs boson decay. See text for more details.

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    • Figure 7
      Figure 7

      Variation of the ΔR values between the muons coming from the decay of the boosted LLP (mediator particle ϕ) as a function of the distance between the secondary vertex and the IP, dSV, with (right panels) and without (left panes) the 3.8 T solenoidal magnetic field. The color bar shows the minimum pT from the muon pair.

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    • Figure 8
      Figure 8

      Efficiencies of the various cuts on mediator particles of mass 0.5 GeV (left panel) and 50 GeV (right panel) for varying lifetimes when it decays to a pair of muons.

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    • Figure 9
      Figure 9

      Projected upper limits on the branching fraction of the Higgs boson decaying into a pair of the mediator particles, Br(h→ϕϕ), for 50 observed decays of the mediator particles to muons for sets of cuts applied only on the displaced muons (top panels) and those combining the prompt and displaced activities (bottom panels). The shown limits are obtained by combining the ggF, VBF, and VH productions for the Higgs boson.

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    • Figure 10
      Figure 10

      Projected upper limits on the branching fraction of the Higgs boson decaying into a pair of the mediator particles, Br(h→ϕϕ), for 50 observed decays of the mediator particles to muons. The shown limits are obtained by combining the ggF, VBF, and VH productions for the Higgs boson.

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    • Figure 11
      Figure 11

      Normalized histograms of the transverse momentum (left panel) and the pseudorapidity (right panel) distributions of the long-lived mediator particle for two benchmark masses (mϕ=1 and 2 GeV) and decay lengths (cτϕ=0.1 and 10 m) before (dashed lines) and after (solid lines) applying the required cut on the DSV.

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    • Figure 12
      Figure 12

      Projected upper limits on Br(h→ϕϕ) for 50 observed decays of the mediator particles into pions for three sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 13
      Figure 13

      Projected upper limits on Br(h→ϕϕ) for 50 observed decays of the mediator particles into kaons for three sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 14
      Figure 14

      Normalized histograms of the transverse momentum (left panel) and the pseudorapidity (right panel) distributions of the long-lived mediator particle for two benchmark masses (mϕ=10 and 50 GeV) and decay lengths (cτϕ=0.1 and 10 m) before (dashed lines) and after (solid lines) applying the required cut on the DSV.

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    • Figure 15
      Figure 15

      Normalized histograms of multiplicity distributions of all particles associated with a DSV [nDSV (left panel)] and charged particles associated with a DSV [nDSVch (right panel)] for long-lived mediator particles having masses of mϕ=10 and 50 GeV, and the decay lengths of cτϕ=0.1 and 10 m after applying the required cut on the DSV. Multiplicity is calculated with particles having pT>0.5  GeV and |η|<2.8.

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    • Figure 16
      Figure 16

      Normalized histograms of the ∑pT,DSV (left panel) and Δϕmax (right panel) distributions for long-lived mediator particles having masses of mϕ=10 and 50 GeV and decay lengths of cτϕ=0.1 and 10 m after applying the required cut on the position of the DSV and nDSVch≥3.

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    • Figure 17
      Figure 17

      Efficiencies of the nDSVch, ∑pT,DSV, and Δϕmax cuts on mediator particles of 10 GeV (left panel) and 50 GeV (right panel) masses as a function of the decay length.

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    • Figure 18
      Figure 18

      Distribution of displaced vertices in the (R,Z) plane of the detector for mediator particles of 10 GeV (left panel) and 50 GeV (right panel) masses having cτϕ=1 and 5 m, respectively, and how it is affected by the selection cuts.

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    • Figure 19
      Figure 19

      Projected upper limits on Br(h→ϕϕ) for 50 observed decays of long-lived mediator particles decaying into a pair of b quarks within the CMS MS for four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH modes of the Higgs boson production at the 14 TeV HL-LHC experiment (3000  fb−1).

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    • Figure 20
      Figure 20

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles decaying into a pair of gluons (left four panels) and s quarks (right four panels) within the CMS MS for four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH channels of the Higgs boson production at the 14 TeV HL-LHC experiment with 3000  fb−1 integrated luminosity.

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    • Figure 21
      Figure 21

      Projected upper limits on Br(h→ϕϕ) for 50 observed decays of long-lived mediator particles decaying into a pair of c quarks within the CMS MS for four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH modes of the Higgs boson production at the 14 TeV HL-LHC experiment (3000  fb−1).

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    • Figure 22
      Figure 22

      Multiplicity of stable particles produced from the displaced secondary vertex (with a tolerance of 1 cm in each of the x, y, and z directions) due to the decay of mediator particles (LLPs) of 10 and 50 GeV masses, each having a decay length of 1 m, when it decays into a pair of gluons, strange quarks, charm quarks, and bottom quarks.

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    • Figure 23
      Figure 23

      Projected upper limits on Br(h→ϕϕ) for 50 observed decays of long-lived mediator particles decaying into τ leptons, when both the τs from a mediator particle decay into muons (left panel), otherwise within the CMS MS (right panel), for three sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH modes for the Higgs boson production at the 14 TeV HL-LHC experiment (3000  fb−1).

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    • Figure 24
      Figure 24

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles using the CMS MS when events are selected by applying the four sets of cuts described in the beginning of Sec. 3a2. The shown limits are obtained by combining the ggF, VBF, and VH channels for the Higgs boson production at the 14 TeV HL-LHC experiment (3000  fb−1) and the decay modes of the mediator particle ϕ→μ+μ−, π+π−, K+K−, cc¯, τ+τ−, and bb¯ according to the branching ratios in Fig. 4.

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    • Figure 25
      Figure 25

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles using the CMS MS when events are selected by applying softer cuts on the displaced particles only. The shown limits are obtained by combining the ggF, VBF, and VH modes for the Higgs boson production at the 14 TeV HL-LHC experiment with an integrated luminosity of 3000  fb−1 and the decay modes of ϕ→μ+μ−, π+π−, K+K−, cc¯, τ+τ−, and bb¯ according to the branching ratios in Fig. 4.

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    • Figure 26
      Figure 26

      Projected sensitivity on the (sinθ,mϕ) plane for the mediator particle in the minimal model with various sets of cuts assuming Br(h→ϕϕ)=0.01 (left panel) and for different values of Br(h→ϕϕ) with the PS×DS≥1  vtx set of cuts (right panel).

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    • Figure 27
      Figure 27

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for four observed decays of long-lived mediator particles within the CODEX-b (top panels) and MATHUSLA (bottom panel) detectors. The shown limits are obtained by combining the ggF, VBF, and VH channels for the production of the Higgs boson. See text for more details.

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    • Figure 28
      Figure 28

      Complementarity of the CMS MS analysis and the MATHUSLA LLP detector analysis at 14 TeV HL-LHC experiment with an integrated luminosity of 3000  fb−1.

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    • Figure 29
      Figure 29

      Projected sensitivity on the (sinθ,mϕ) plane for the mediator particle in the minimal model achieved with the CMS MS with the PS×DS≥1  vtx set of cuts, MATHUSLA and both the designs of CODEX-b assuming Br(h→ϕϕ)=0.01.

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    • Figure 30
      Figure 30

      Normalized histograms of the boost factor distribution (top panels) and the decay length distribution in lab frame (bottom panels) of the mediator particle from the Higgs boson decay, for mϕ=100  MeV, 5 GeV, 50 GeV, and cτϕ=0.1  m (solid lines) and 1000 m (dashed lines), in the ggF (left panels), VBF (center panels), and VH (right panels) Higgs boson production modes at s=100  TeV. The histogram of the exponential distribution, exp[−d/(cτϕ)], for the two different decay lengths are shown in gray.

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    • Figure 31
      Figure 31

      Comparison of the projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles into a pair of muons in the CMS and the FCC-hh detectors for the PS×DμS≥1  vtx set of cuts. The shown limits are obtained by combining the ggF, VBF, and VH modes for the Higgs boson production.

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    • Figure 32
      Figure 32

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles into muons within the FCC-hh MS at the 100 TeV collider experiment for the four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 33
      Figure 33

      Projected upper limits on the branching fraction of the Higgs boson decaying into a pair of the mediator particles, Br(h→ϕϕ), for 50 observed decays of the mediator particles to muons. The shown limits are obtained by combining the ggF, VBF, and VH productions for the Higgs boson.

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    • Figure 34
      Figure 34

      Left: efficiency of various cuts with varying decay lengths for 10 GeV mediator particle in the FCC-hh barrel and end cap MS along with the corresponding efficiencies obtained in the CMS MS. Right: comparison of the normalized distributions of Δϕmax for two decay lengths for 10 GeV mediator particle in the 14 and 100 TeV colliders.

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    • Figure 35
      Figure 35

      Comparison of the efficiencies as a function of decay lengths, as obtained from the DjetsS≥1  vtx (top) and PggFS×DjetsS≥1 vtx (bottom) sets of cuts between the CMS MS at 14 TeV and FCC-hh MS at 100 TeV, when a mediator of mass 10 GeV (left) and 50 GeV (right) decays to a pair of b quarks. For the FCC-hh detector, we also show the efficiencies for the barrel and end cap MS and the forward MS separately.

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    • Figure 36
      Figure 36

      Comparison of the projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles into a pair of b quarks within the CMS and the FCC-hh MS for the PS×DjetsS≥1  vtx set of cuts. The shown limits are obtained by combining the ggF, VBF, and VH modes for the Higgs boson production.

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    • Figure 37
      Figure 37

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles into b quarks within the FCC-hh MS at the 100 TeV collider experiment for the four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 38
      Figure 38

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for 50 observed decays of long-lived mediator particles into c quarks within the FCC-hh MS at the 100 TeV collider experiment for the four sets of cuts explained in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 39
      Figure 39

      Efficiencies of different ∑pT cuts, with and without Δϕmax>0.2 cut in the FCC-hh barrel and end cap MS, with varying decay lengths for the 10 GeV mediator particle.

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    • Figure 40
      Figure 40

      Illustration of the parameters denoting position and size of the decay volumes for DELIGHT detector, a box-type LLP detector near the IP of the 100 TeV collider.

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    • Figure 41
      Figure 41

      Projected upper limits on the branching fraction, Br(h→ϕϕ), for four observed decays of long-lived mediator particles within DELIGHT (A), (B), and (C) at the 100 TeV collider experiment, which are described in the text. The shown limits are obtained by combining the ggF, VBF, and VH production modes of the Higgs boson.

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    • Figure 42
      Figure 42

      Validation of the CODEX-b (left) and MATHUSLA (right) detectors [71, 72].

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    • Figure 43
      Figure 43

      Efficiency maps for decays of long-lived mediator particles within the CODEX-b detector for the ggF (top), VBF (center), and VH (bottom) production of the Higgs boson.

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    • Figure 44
      Figure 44

      Efficiency maps for decays of long-lived mediator particles within MATHUSLA for the ggF (top), VBF (center), and VH (bottom) production of the Higgs boson.

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    • Figure 45
      Figure 45

      Efficiency maps for decays of long-lived mediator particles within the DELIGHT (A) detector near the 100 TeV collider for the ggF (top panels), VBF (center panels), and VH (bottom panels) production of the Higgs boson at 100 TeV collider experiment.

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    • Figure 46
      Figure 46

      Efficiency maps for decays of long-lived mediator particles within the DELIGHT (B) detector near the 100 TeV collider for the ggF (top panels), VBF (center panels), and VH (bottom panels) production of the Higgs boson at 100 TeV collider experiment.

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    • Figure 47
      Figure 47

      Efficiency maps for decays of long-lived mediator particles within the DELIGHT (C) detector near the 100 TeV collider for the ggF (top panels), VBF (center panels), and VH (bottom panels) production of the Higgs boson at 100 TeV collider experiment.

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