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Summary

Abstract

Introduction

Protocol

Representative Results

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Acknowledgements

References

Engineering

Setting Limits on Supersymmetry Using Simplified Models

Published: November 15th, 2013

DOI:

10.3791/50419

1Department of Physics and Astronomy, University College London, 2CERN, 3Physics Division, Lawrence Berkeley National Laboratories

This paper demonstrates a protocol for recasting experimental simplified model limits into conservative and aggressive limits on an arbitrary new physics model. Publicly available LHC experimental results can be recast in this manner into limits on almost any new physics model with a supersymmetry-like signature.

Experimental limits on supersymmetry and similar theories are difficult to set because of the enormous available parameter space and difficult to generalize because of the complexity of single points. Therefore, more phenomenological, simplified models are becoming popular for setting experimental limits, as they have clearer physical interpretations. The use of these simplified model limits to set a real limit on a concrete theory has not, however, been demonstrated. This paper recasts simplified model limits into limits on a specific and complete supersymmetry model, minimal supergravity. Limits obtained under various physical assumptions are comparable to those produced by directed searches. A prescription is provided for calculating conservative and aggressive limits on additional theories. Using acceptance and efficiency tables along with the expected and observed numbers of events in various signal regions, LHC experimental results can be recast in this manner into almost any theoretical framework, including nonsupersymmetric theories with supersymmetry-like signatures.

One of the most promising extensions of the Standard Model, supersymmetry (SUSY)1-14, is the central focus of many searches by the LHC experiments at CERN. The data collected in 2011 are already sufficient to push the limits of new physics beyond those of any previous collider15-22. As new data arrive and the exclusions are pushed still farther, it will be increasingly important to clearly communicate to the physics community what regions of the extensive supersymmetric parameter space have been excluded. Current limits are typically set on constrained two-dimensional planes, which frequently do not represent the diverse available SUSY parameter ....

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1. Model Deconstruction

  1. Generate proton-proton collision events covering a plane in the parameter space of the NPM. Any event generator configuration that includes a parton shower and hadronization model can be used. In the case of MSUGRA for example, the mass spectra are generated using Isasugra33, and the branching fractions and decay widths are calculated using MSSMCalc34. For the event generation itself, MadGraph 5 1.3.934 with CTEQ 6L1 parton density functions35

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Having applied the model deconstruction step to a point in the parameter space of MSUGRA, a breakdown of the output can be best visualized by counting up the various production and decay modes for every generated event and plotting the corresponding production rates and branching fractions according to the relative frequencies. The branching fractions for the various production and decay modes for representative MSUGRA points are illustrated in Figures 2 and 3. A large number of similar .......

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The application of simplified model limits to produce an exclusion contour in a complete new physics model has been demonstrated. Despite the apparent complexity of MSUGRA parameter space points, the kinematics can be well-reproduced by a combination of only a small number of simplified models. The kinematic agreement is further improved when looking within a particular signal region, since the searches thus far conducted at the LHC tend to favor simplified model-like event topologies with a (relatively) small number of .......

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The authors would like to thank Jay Wacker for significant discussion of simplified models and potential pitfalls. Many thanks also to Max Baak and Till Eifert for constructive criticism and encouragement whenever it was necessary. Thanks to the CERN Summer Student Program for making this collaboration possible.

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  1. Miyazawa, H. Baryon Number Changing Currents. Prog. Theor. Phys. 36, 1266-1276 (1966).
  2. Ramond, P. Dual Theory for Free Fermions. Phys. Rev. D. 3, 2415-2418 (1971).
  3. Gol'fand, Y. A., Likhtman, E. P. Extension of the Algebra of Poincare Group Generators and Violation of P invariance. JETP Lett. 13, 323-326 (1971).
  4. Neveu, A., Schwarz, J. H. Factorizable dual model of pions. Nucl. Phys. B. 31, 86-112 (1971).
  5. Gervais, J. L., Sakita, B. Field theory interpretation of supergauges in dual models. Nucl. Phys. B. 34, 632-639 (1971).
  6. Neveu, A., Schwarz, J. H. Quark Model of Dual Pions. Phys. Rev. D. 4, 1109-1111 (1971).
  7. Volkov, D. V., Akulov, V. P. Is the neutrino a goldstone particle. Phys. Lett. B. 46, 109-110 (1973).
  8. Wess, J., Zumino, B. A lagrangian model invariant under supergauge transformations. Phys. Lett. B. 49, 52-54 (1974).
  9. Wess, J., Zumino, B. Supergauge transformations in four dimensions. Nucl. Phys. B. 70, 39-50 (1974).
  10. Fayet, P. Supersymmetry and Weak, Electromagnetic and Strong Interactions. Phys. Lett. B. 64, 159-162 (1976).
  11. Fayet, P. Spontaneously Broken Supersymmetric Theories of Weak, Electromagnetic and Strong Interactions. Phys. Lett. B. 69, 489-494 (1977).
  12. Farrar, G. R., Fayet, P. Phenomenology of the Production, Decay, and Detection of New Hadronic States Associated with Supersymmetry. Phys. Lett. B. 76, 575-579 (1978).
  13. Fayet, P. Relations Between the Masses of the Superpartners of Leptons and Quarks, the Goldstino Couplings and the Neutral Currents. Phys. Lett. B. 84, 416-420 (1979).
  14. Dimopoulos, S., Georgi, H. Softly Broken Supersymmetry and SU(5. Nucl. Phys. B. 193, 150-162 (1981).
  15. The ATLAS Collaboration. Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb-1 of √s = 7TeV proton-proton collisions. Phys. Rev. D. , .
  16. The ATLAS Collaboration. Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s = 7TeV proton-proton collisions. Phys. Lett. B. 710, 67-85 (2012).
  17. The ATLAS Collaboration. Further search for supersymmetry at √s=7 TeV in final states with jets, missing transverse momentum and isolated leptons with the ATLAS detector. Phys. Rev. D. , .
  18. The CMS Collaboration. Search for new physics in the multijet and missing transverse momentum final state in proton-proton collisions at sqrt(s) = 7 TeV. Phys. Rev. Lett. 109, 171803 (2012).
  19. The CMS Collaboration. Search for supersymmetry in pp collisions at √s=7 TeV in events with a single lepton, jets, and missing transverse momentum. J. High Energy Phys. 08, 165 (2011).
  20. The CMS Collaboration. Search for supersymmetry in events with b-quark jets and missing transverse energy in pp collisions at 7 TeV. Phys. Rev. D. 86, 072010 (2012).
  21. The CMS Collaboration. 2012 Report No.: CMS-PAS-SUS-11-016. Interpretation of Searches for Supersymmetry. , (2012).
  22. The CMS Collaboration. Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s = 7 TeV. Phys. Lett. B. 718, 815 (2012).
  23. Alves, D., et al. Where the Sidewalk Ends: Jets and Missing Energy Search Strategies for the 7 TeV LHC. JHEP. 1110, 012 (2011).
  24. Alves, D., et al. Simplified Models for LHC New Physics Searches. J. Phys. G.: Nucl. Part. Phys. 39, 105005 (2012).
  25. Chamseddine, A. H., et al. Locally Supersymmetric Grand Unification. Phys. Rev. Lett. 49, 970-974 (1982).
  26. Barbieri, R., et al. Gauge models with spontaneously broken local supersymmetry. Phys. Lett. B. 119, 343-347 .
  27. Ibanez, L. E. Locally supersymmetric SU(5) grand unification. Phys. Lett. B. 118, 73 (1982).
  28. Hall, L. J., et al. Supergravity as the messenger of supersymmetry breaking. Phys. Rev. D. 27, 2359-2378 (1983).
  29. Ohta, N. Grand Unified Theories Based on Local Supersymmetry. PTP. 70, 542-549 (1983).
  30. Chung, D. J. H., et al. The soft supersymmetry-breaking Lagrangian: theory and applications. J. Phys. Rept. 407, 1-203 (2005).
  31. Alwall, J. MadGraph 5: Going Beyond. JHEP. 1106, 128 (2011).
  32. Pumplin, J. New Generation of Parton Distributions with Uncertainties from Global QCD Analysis. JHEP. 0207, 012 (2002).
  33. Sjöstrand, T., Mrenna, S., Skands, P. Pythia 6.4 Physics and Manual. JHEP. 05, 026 (2006).
  34. . PhysicsResultsSUS < CMSPublic < TWiki [Internet] Available from: https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS
  35. . SupersymmetryPublicResults < AtlasPublic < TWiki [Internet] Available from: https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults (2013)
  36. Collaboration, D. 0. Search for Squarks and Gluinos in pp̄ collisions at √s=1.8TeV. Phys. Rev. Lett. 75, 618-623 (1995).
  37. Collaboration, C. D. F. Search for Gluinos and Scalar Quarks in pp̄ collisions at √s=1.8TeV using the Missing Energy plus Multijets Signature. Phys. Rev. Lett. 88, 041801 (2002).
  38. Collaboration, C. D. F. Inclusive Search for Squark and Gluino Production in pp̄ Collisions at√s=1.96TeV. Phys. Rev. Lett. 102, 121801 (2009).
  39. Collaboration, D. 0. Search for squarks and gluinos in events with jets and missing transverse energy using 2.1fb-1 of pp̄ collision data at √s=1.96TeV. Phys. Lett. B. 660, 449-457 (2008).
  40. Collaboration, D. E. L. P. H. I. Searches for supersymmetric particles in e+e-collisions up to 208 GeV and interpretation of the results within the MSSM. Eur. Phys. J. C. 31, 421-479 (2003).
  41. Collaboration, L. 3. Search for Scalar Leptons and Scalar Quarks at LEP. Phys. Lett. B. 580, 37-49 (2004).
  42. Collaboration, A. T. L. A. S. Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √s=7TeV proton-proton collisions. Phys. Lett. B. 701, 186-203 (2011).

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