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  • Open Access

New production channels for light dark matter in hadronic showers

A. Celentano, L. Darmé, L. Marsicano, and E. Nardi
Phys. Rev. D 102, 075026 – Published 21 October 2020
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  • INTRODUCTION
  • LDM PRODUCTION BY SECONDARY e± IN PROTON…
  • NUMERICAL EVALUATION
  • APPLICATIONS AND EXAMPLES
  • CONCLUSIONS AND OUTLOOKS
  • NOTES
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    Hadronic showers transfer a relevant amount of their energy to electromagnetic subshowers. We show that the generation of “secondary” dark photons in these subshowers is significant and typically dominates the production at low dark photon masses. The resulting dark photons are however substantially less energetic than the ones originating from mesons decay. We illustrate this point both semianalytically and through Monte Carlo simulations. Existing limits on vector-mediator scenarios for light dark matter are updated with the inclusion of the new production processes.

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    • Received 25 June 2020
    • Accepted 11 August 2020

    DOI:https://doi.org/10.1103/PhysRevD.102.075026

    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 fermion sectorExtensions of gauge sectorParticle dark matterParticle production
    1. Physical Systems
    Hypothetical gauge bosons
    1. Techniques
    Neutrino detection
    Particles & Fields

    Authors & Affiliations

    A. Celentano1, L. Darmé2, L. Marsicano1, and E. Nardi2

    • 1Istituto Nazionale di Fisica Nucleare, Sezione di Genova, 16146 Genova, Italy
    • 2Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, C.P. 13, 00044 Frascati, Italy

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    Issue

    Vol. 102, Iss. 7 — 1 October 2020

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    Images

    • Figure 1
      Figure 1

      Comparison of the differential π0 yield per proton on target from a 120 GeV proton impinging on a thick graphite target. Red curve: result obtained from Eq. (1) based on EPOS-LHC [49]. Blue curve: results of a full geant4 -based simulation.

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    • Figure 2
      Figure 2

      Differential track length times energy squared in GeV for the positrons in the showers generated in the SHiP, DUNE and MiniBooNE targets in arbitrary units. The yellow lines represent the results from complete geant4 simulations. The blue regions represent the results obtained from the semianalytical approach described in the text, with the upper lines obtained by fixing in Eq. (1) L=λT (the nuclear interaction length) and the lower dashed lines corresponding to L=λc (the nuclear collision length) which is a more conservative choice.

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    • Figure 3
      Figure 3

      Angular distribution of positrons produced by the 120 GeV proton beam from the Fermilab accelerator in the DUNE target. The black, red and blue lines refer, respectively, to positrons with a 1 GeV, 3 GeV, and 8 GeV energy threshold. The normalization of each curve is proportional to the total positron yield applying the corresponding energy threshold. The angular distribution of electrons, not displayed, features a similar behavior.

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    • Figure 4
      Figure 4

      Dominant processes for dark photon production during the electromagnetic development of a shower.

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    • Figure 5
      Figure 5

      Production cross section for the associated e+e−→γV and Compton-like process γe−→e−V as function of the energy of the incoming particle (either a photon Eγ, a positron or an electron with energy Ee±) in the laboratory frame. We chose ϵ=0.001,mV=10  MeV.

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    • Figure 6
      Figure 6

      Dark photon production rate per proton-on-target for the MiniBooNE experiment as function of the dark photon mass mV. The shower-induced leptonic production processes are shown in green: electron/positron bremsstrahlung (dashed line) and resonant e+e−→V,V→χχ* (solid line), The blue line corresponds to the rate for standard hadronic production processes. We have applied basic cuts on the geant4 objects: their angle θ with respect to the beam axis is selected such that sinθ<0.2, and their kinetic energy should be larger than 10 MeV.

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    • Figure 7
      Figure 7

      Typical setup of a proton beam-dump experiment. The proton beam impinges on a thick target, where LDM particles are produced by secondaries—the inset shows the production of a LDM particle pairs from e+e− annihilation. LDM particles then propagate straight toward a downstream detector at distance D, where they are revealed via the scattering on atomic electrons and nuclei.

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    • Figure 8
      Figure 8

      Limits for the MiniBooNE experiments. The grey region represents the exclusion bounds from the BABAR [16] and NA64 [17] collaborations. The dashed orange line corresponds to the sensitivity as extracted from [64], the rust solid line is our estimate based on hadronic processes only, the solid green line is our estimate based on secondary production processes only, and the thick black line is the combination of the two.

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    • Figure 9
      Figure 9

      Projected reach of the SHiP experiment. The grey region represents the exclusion bounds from the BABAR [16] and NA64 [17] collaborations. The dashed orange line is the limit extracted from [74], the rust line our estimate based on hadronic processes only, the solid green line our estimate based on the secondary production processes only, and the thick black line is the combination of both.

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    • Figure 10
      Figure 10

      Energy distribution of LDM particles impinging on the SHiP detector for different production mechanisms: production from mesons decay (blue), positrons resonant annihilation (orange), electrons and positrons bremsstrahlung (green).

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    • Figure 11
      Figure 11

      Projected reach of the NOνA experiment. The grey region represents the exclusion bounds from the BABAR [16] and NA64 [17] collaborations. The rust line is our estimate based on hadronic processes only, the solid green line our estimate based on secondary production processes only, and the thick black line is the combination of both.

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    • Figure 12
      Figure 12

      Projected reach of the NOνA (green lines) and the SHiP (red lines) experiments, with reduced energy thresholds at 125 MeV for NOνA and 250 MeV for SHiP. Sensitivity estimates are based on 16.4 (38) signal events for NOνA (SHiP). The grey region represents the exclusion bounds from the BABAR [16] and NA64 [17] collaborations. The solid lines are our estimate based on hadronic processes only, while the dashed lines are based on secondary production processes.

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    • Figure 13
      Figure 13

      Projected reach of DUNE near detector. The grey region represents the exclusion bounds from the BABAR [16] and NA64 [17] collaborations. The rust line represents our estimate based on hadronic processes only, the solid green line our estimate based on secondary production only, and the thick black line is the combination of both.

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    • Figure 14
      Figure 14

      Projected reach of DUNE near detector, if moved by 36 m off the beam axis. Same color coding as the previous DUNE plot.

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