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Systematically searching for new resonances at the energy frontier using topological models

Mohammad Abdullah, Eric Albin, Anthony DiFranzo, Meghan Frate, Craig Pitcher, Chase Shimmin, Suneet Upadhyay, James Walker, Pierce Weatherly, Patrick J. Fox, and Daniel Whiteson
Phys. Rev. D 89, 095002 – Published 7 May 2014
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  • INTRODUCTION
  • TOPOLOGIES IN ℓ+ℓ−jj
  • THE MODELS
  • BACKGROUNDS TO ℓℓjj
  • MASS RECONSTRUCTION AND LHC SENSITIVITY
  • CONCLUSIONS
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    We propose a new strategy to systematically search for new physics processes in particle collisions at the energy frontier. An examination of all possible topologies which give identifiable resonant features in a specific final state leads to a tractable number of “topological models” per final state and gives specific guidance for their discovery. Using one specific final state, ℓℓjj, as an example, we find that the number of possibilities is reasonable and reveals simple, but as-yet-unexplored, topologies which contain significant discovery potential. We propose analysis techniques and estimate the sensitivity for pp collisions with s=14 TeV and L=300 fb−1.

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    • Received 10 February 2014

    DOI:https://doi.org/10.1103/PhysRevD.89.095002

    © 2014 American Physical Society

    Authors & Affiliations

    Mohammad Abdullah1, Eric Albin1, Anthony DiFranzo1, Meghan Frate1, Craig Pitcher1, Chase Shimmin1, Suneet Upadhyay1, James Walker1, Pierce Weatherly1, Patrick J. Fox2, and Daniel Whiteson1

    • 1Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
    • 2Fermi National Accelerator Laboratory, Batavia, Illinois 60615, USA

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    Issue

    Vol. 89, Iss. 9 — 1 May 2014

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    Images

    • Figure 1
      Figure 1

      Diagram for Z′→χ1χ2→ℓ+jℓ−j.

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    • Figure 2
      Figure 2

      Diagram for Z′→χ1χ2→ℓ+ℓ−jj.

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    • Figure 3
      Figure 3

      Diagrams for Z′→ℓ∓L→ℓ∓(ℓ±jj) (right).

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    • Figure 4
      Figure 4

      Diagram for Z′→jQ→j(ℓ+ℓ−j).

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    • Figure 5
      Figure 5

      Cross section for Z′ production at s=14  TeV, including all decay modes.

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    • Figure 6
      Figure 6

      Distribution of mℓ+ℓ− in simulated events for a background process contributing to the ℓℓjj final state in pp collisions at s=14  TeV with L=300  fb−1, after preselection requirements.

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    • Figure 7
      Figure 7

      In simulated Z′→χ1χ2→ℓℓjj events, the distribution of reconstructed invariant ℓℓ, jj, and ℓℓjj masses for several values of mZ′,mχ1, and mχ2. The normalization is arbitrary. The shoulder in mjj is due to imperfect selection of the jet pair.

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    • Figure 8
      Figure 8

      In the (ℓℓ)(jj) topology, distribution of mℓℓjj in simulated signal and background events for two example mass points, after requirements on mℓℓ and mjj in pp collisions at s=14  TeV with L=300  fb−1. The top shows the case of mZ′=250  GeV, mχ1,χ2=100  GeV; the bottom shows the case of mZ′=500  GeV, mχ1,χ2=100  GeV. In both cases, an arbitrary value of σ(pp→Z′→χ1χ2→ℓℓjj) is assumed.

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    • Figure 9
      Figure 9

      In the (ℓℓ)(jj) topology, selection efficiency and expected cross-section upper limits versus mχ1 and mχ2 for several choices of mZ′ at s=14  TeV with L=300  fb−1. For small values of mχ2, the efficiency is small due to jet pT requirements and jet resolution effects. For values of mχ1 near mZ, the larger backgrounds lead to weakened limits.

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    • Figure 10
      Figure 10

      In the (ℓℓ)(jj) topology, expected upper limits on the cross section σ(pp→Z′→χ1χ2→ℓℓjj) at 95% C.L. versus mZ′ for several choices of mχ1 and mχ2 in pp collisions at s=14  TeV with L=300  fb−1. The mχ1,2=200, 100 GeV (red curve) and mχ1,2=100, 200 curves have different dependences on mZ′ due to the asymmetry in the lepton and jet efficiencies for large values of pTχ.

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    • Figure 11
      Figure 11

      Limits on coupling gZ′qq for two choices of BF(Z′→χ1χ2). The shaded region shows the current limits on the coupling from other topologies (see the text) where the width of the band reflects the variation with assumed mχ1 and mχ2 in pp collisions at s=14  TeV with L=300  fb−1.

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    • Figure 12
      Figure 12

      In simulated Z′→ℓL→ℓℓjj events, distribution of reconstructed invariant ℓjj and ℓℓjj masses for several values of mZ′ and mL. Normalization is arbitrary.

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    • Figure 13
      Figure 13

      In the ℓ(ℓjj) topology, the distribution of mℓℓjj in signal and background events for two example mass points, after requirements on mℓjj and mℓℓ in pp collisions at s=14  TeV with L=300  fb−1. The top shows the case of mZ′=250  GeV, mL=100  GeV; the bottom shows the case of mZ′=500  GeV, mL=200  GeV.

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    • Figure 14
      Figure 14

      In the ℓ(ℓjj) topology, selection efficiency and expected cross-section upper limits versus mZ′ and mL at s=14  TeV with L=300  fb−1. For large mZ′−mL, the efficiency drops due to large transverse momentum of the L, which leads to small opening angles of the L decay products.

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    • Figure 15
      Figure 15

      In the ℓ(ℓjj) topology, expected upper limits on the coupling gZ′gg versus mZ′ and mL for two choices of BF(Z′→ℓL) at s=14  TeV with L=300  fb−1. The shaded region shows the current limits on the coupling from other topologies (see the text) where the width of the band reflects the variation with assumed mL.

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    • Figure 16
      Figure 16

      In the j(jℓℓ) topology, distribution of reconstructed invariant jℓℓ and ℓℓjj masses for several values of mZ′ and mQ. Normalization is arbitrary.

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    • Figure 17
      Figure 17

      In the j(jℓℓ) topology, distribution of mℓℓjj in signal and background events for two example mass points, after requirements on mjℓℓ and mℓℓ at s=14  TeV with L=300  fb−1. The top shows the case of mZ′=250  GeV, mQ=200  GeV; the bottom shows the case of mZ′=600  GeV, mQ=200  GeV. In both cases, an arbitrary value of σ(pp→Z′→qQ→jjℓℓ) is assumed.

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    • Figure 18
      Figure 18

      In the j(jℓℓ) topology, selection efficiency (top) and expected cross-section upper limits (bottom) versus mZ′ and mQ at s=14  TeV with L=300  fb−1. For large mZ′−mQ, the efficiency drops due to the large transverse momentum of the Q, which leads to small opening angles of the Q decay products.

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    • Figure 19
      Figure 19

      Expected upper limits on the coupling gZ′gg versus mZ′ and mQ for two choices of BF(Z′→qQ) at s=14  TeV with L=300  fb−1. The shaded region shows the current limits on the coupling from other topologies (see the text) where the width of the band reflects the variation with assumed mQ.

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