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  • Open Access

Searching for leptoquarks at IceCube and the LHC

Ujjal Kumar Dey, Deepak Kar, Manimala Mitra, Michael Spannowsky, and Aaron C. Vincent
Phys. Rev. D 98, 035014 – Published 9 August 2018
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  • INTRODUCTION
  • MODELS
  • ICECUBE EVENTS
  • CONSTRAINTS FROM LHC
  • FLAVOR ANOMALIES
  • CONCLUSION
  • ACKNOWLEDGMENTS
  • APPENDICES
    • References

    Abstract

    In the light of recent experimental results from IceCube, LHC searches for scalar leptoquark, and the flavor anomalies RK and RK*, we analyze two scalar leptoquark models with hypercharge Y=1/6 and Y=7/6. We consider the 53 high-energy starting events from IceCube and perform a statistical analysis, taking into account both the Standard Model and leptoquark contribution together. The lighter leptoquark states that are in agreement with IceCube are strongly constrained from LHC di-lepton+dijet search. Heavier leptoquarks in the TeV mass range are in agreement both with IceCube and LHC. We furthermore show that leptoquark, which explains the B-physics anomalies and does not have any coupling with the third generation of quarks and leptons, can be strongly constrained.

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    • Received 12 June 2018

    DOI:https://doi.org/10.1103/PhysRevD.98.035014

    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
    Neutrino interactions
    1. Physical Systems
    Leptoquarks
    Particles & Fields

    Authors & Affiliations

    Ujjal Kumar Dey1,*, Deepak Kar2,†, Manimala Mitra3,4,‡, Michael Spannowsky5,§, and Aaron C. Vincent6,7,∥

    • 1Centre for Theoretical Studies, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
    • 2School of Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa
    • 3Institute of Physics, Sachivalaya Marg, Bhubaneswar, Odisha 751005, India
    • 4Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai 400085, India
    • 5Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, United Kingdom
    • 6Department of Physics, Imperial College London, Blackett Laboratory, Prince Consort Road SW7 2AZ, United Kingdom
    • 7Canadian Particle Astrophysics Research Centre (CPARC), Department of Physics, Engineering Physics and Astronomy, Queens University, Kingston, Ontario K7L 3N6, Canada

    • *ujjal.dey1@gmail.com
    • †deepak.kar@cern.ch
    • ‡manimala@iopb.res.in
    • §michael.spannowsky@durham.ac.uk
    • ∥aaron.vincent@queensu.ca

    Article Text

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    Issue

    Vol. 98, Iss. 3 — 1 August 2018

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    Images

    • Figure 1
      Figure 1

      Feynman diagrams for neutrino-quark interactions through LQ χ1/3, relevant for model A.

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    • Figure 2
      Figure 2

      Feynman diagrams for neutrino-quark interactions through LQ χ2/3, relevant for model B.

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    • Figure 3
      Figure 3

      The ratio of neutrino-nucleon cross sections, between the Standard Model (SM) + leptoquark model and the relevant Standard Model only channel, for five different LQ masses. Left: model A, neutral current contribution only (x11=1, x12=x13=0.1). Middle: model B neutral current contribution only (solid line); charged current contribution only (dashed line) (x11=y11=1, all other couplings set to zero). Right: ratio of the total cross section to the SM case (note different y scale).

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    • Figure 4
      Figure 4

      Constraints on model B from the 53 HESE IceCube events. Left: exclusion contours as a function of the LQ mass and coupling; the best-fit point is shown as a red diamond. Middle: astrophysical neutrino flux necessary to accommodate the additional force mediator. Right: best-fit number of atmospheric background neutrinos as a function of the LQ mass and coupling. We do not show the corresponding figure for model A, since every point is within 1σ of the Standard Model. In all three plots the purple (dashed) horizontal lines represent the perturbativity bound of the corresponding couplings.

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    • Figure 5
      Figure 5

      Spectrum as expected at IceCube for the best-fit point in model A (left) and model B (right). Atmospheric backgrounds are separated in to tracks (magenta) and showers (light blue). Total tracks (atmospheric+astrophysical) are shown in red, while the showers (blue) are split into LQ contribution (dash-dotted line), SM contribution (dashed line), and total (solid line). Data points from four years of IceCube data (crosses) are split into tracks (red) and showers (black). Note (1) the bin at Edep=300  TeV contains both a shower and a track event, and (2) although we have not shown them for clarity, the zero-event bins up to Edep=10  PeV are included in our analysis.

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    • Figure 6
      Figure 6

      Constraints on the relevant couplings x11, y11 from the CMS search for the first generation of leptoquark. Shaded region corresponds to the excluded region at the 95% C.L. [16]. Gray dashed line corresponds to the exclusion limit for model A and the solid brown and purple lines represent model B. For model B, the two lines correspond to the two choices of the parameters (a),(b) defined in the text.

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    • Figure 7
      Figure 7

      Correlation between the two branching ratios of χ25/3→tu and χ25/3→eu. Gray shaded region corresponds to the excluded region from CMS eejj search for first generation of leptoquark, for MLQ=650  GeV. Similar limits hold for leptoquark connecting μ. Solid line corresponds to the scenario of x31=0.1, x11≠0, while the dashed line corresponds to x31=x32=x33=0.01, x11≠0. For both the lines we consider x11 variation between 0.001-1.

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    • Figure 8
      Figure 8

      The contours for different r [see Eq. (18)] that correspond to the dijet+MET limits [90], relevant for model A. The region with r≥1 is excluded at 95% C.L.

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