Journal of High Energy Physics

, 2016:127 | Cite as

Forward-backward asymmetry as a discovery tool for Z′ bosons at the LHC

  • Elena AccomandoEmail author
  • Alexander Belyaev
  • Juri Fiaschi
  • Ken Mimasu
  • Stefano Moretti
  • Claire Shepherd-Themistocleous
Open Access
Regular Article - Theoretical Physics


The Forward-Backward Asymmetry (AFB) in Z′ physics is commonly only perceived as the observable which possibly allows one to interpret a Z′ signal appearing in the Drell-Yan channel by distinguishing different models of such (heavy) spin-1 bosons. In this paper, we revisit this issue, showing that the absence of any di-lepton rapidity cut, which is commonly used in the literature, can enhance the potential of the observable at the LHC. We moreover examine the ability of AFB in setting bounds on or even discovering a Z′ at the Large Hadron Collider (LHC) concluding that it may be a powerful tool for this purpose. We analyse two different scenarios: Z′-bosons with a narrow and wide width, respectively. We find that, in the first case, the significance of the AFB search can be comparable with that of the ‘bump’ search usually adopted by the experimental collaborations; however, in being a ratio of (differential) cross sections, the AFB has the advantage of reducing experimental systematics as well as theoretical errors due to PDF uncertainties. In the second case, the AFB search can outperform the bump search in terms of differential shape, meaning the AFB distribution may be better suited for new broad resonances than the event counting strategy usually adopted in such cases.


Hadronic Colliders 


Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


  1. [1]
    E. Accomando, A. Belyaev, L. Fedeli, S.F. King and C. Shepherd-Themistocleous, Zphysics with early LHC data, Phys. Rev. D 83 (2011) 075012 [arXiv:1010.6058] [INSPIRE].ADSGoogle Scholar
  2. [2]
    P. Langacker, The Physics of Heavy ZGauge Bosons, Rev. Mod. Phys. 81 (2009) 1199 [arXiv:0801.1345] [INSPIRE].CrossRefADSGoogle Scholar
  3. [3]
    J. Erler and P. Langacker, Constraints on extended neutral gauge structures, Phys. Lett. B 456 (1999) 68 [hep-ph/9903476] [INSPIRE].CrossRefADSGoogle Scholar
  4. [4]
    E. Accomando, D. Becciolini, A. Belyaev, S. Moretti and C. Shepherd-Themistocleous, Zat the LHC: Interference and Finite Width Effects in Drell-Yan, JHEP 10 (2013) 153 [arXiv:1304.6700] [INSPIRE].CrossRefADSGoogle Scholar
  5. [5]
    E. Accomando et al., Wand Zsearches at the LHC, PoS(DIS 2013)125 [INSPIRE].
  6. [6]
    A. Belyaev, R. Foadi, M.T. Frandsen, M. Jarvinen, F. Sannino and A. Pukhov, Technicolor Walks at the LHC, Phys. Rev. D 79 (2009) 035006 [arXiv:0809.0793] [INSPIRE].ADSGoogle Scholar
  7. [7]
    D. Barducci, A. Belyaev, S. De Curtis, S. Moretti and G.M. Pruna, Exploring Drell-Yan signals from the 4D Composite Higgs Model at the LHC, JHEP 04 (2013) 152 [arXiv:1210.2927] [INSPIRE].CrossRefADSGoogle Scholar
  8. [8]
    Y.G. Kim and K.Y. Lee, Direct search for heavy gauge bosons at the LHC in the nonuniversal SU(2) model, Phys. Rev. D 90 (2014) 117702 [arXiv:1405.7762] [INSPIRE].ADSGoogle Scholar
  9. [9]
    E. Malkawi and C.P. Yuan, New physics in the third family and its effect on low-energy data, Phys. Rev. D 61 (2000) 015007 [hep-ph/9906215] [INSPIRE].ADSGoogle Scholar
  10. [10]
    G. Altarelli, B. Mele and M. Ruiz-Altaba, Searching for New Heavy Vector Bosons in \( p\overline{p} \) Colliders, Z. Phys. C 45 (1989) 109 [Erratum ibid. C 47 (1990) 676] [INSPIRE].
  11. [11]
    J. Erler, P. Langacker, S. Munir and E. Rojas, ZBosons at Colliders: a Bayesian Viewpoint, JHEP 11 (2011) 076 [arXiv:1103.2659] [INSPIRE].CrossRefADSGoogle Scholar
  12. [12]
    N. Arkani-Hamed, S. Dimopoulos and G.R. Dvali, The Hierarchy problem and new dimensions at a millimeter, Phys. Lett. B 429 (1998) 263 [hep-ph/9803315] [INSPIRE].CrossRefADSGoogle Scholar
  13. [13]
    N. Arkani-Hamed, S. Dimopoulos and G.R. Dvali, Phenomenology, astrophysics and cosmology of theories with submillimeter dimensions and TeV scale quantum gravity, Phys. Rev. D 59 (1999) 086004 [hep-ph/9807344] [INSPIRE].ADSGoogle Scholar
  14. [14]
    E. Eichten, K.D. Lane and M.E. Peskin, New Tests for Quark and Lepton Substructure, Phys. Rev. Lett. 50 (1983) 811 [INSPIRE].CrossRefADSGoogle Scholar
  15. [15]
    E. Eichten, I. Hinchliffe, K.D. Lane and C. Quigg, Super Collider Physics, Rev. Mod. Phys. 56 (1984) 579 [INSPIRE].CrossRefADSGoogle Scholar
  16. [16]
    CMS collaboration, Search for physics beyond the standard model in dilepton mass spectra in proton-proton collisions at \( \sqrt{s}=8 \) TeV, JHEP 04 (2015) 025 [arXiv:1412.6302] [INSPIRE].
  17. [17]
    T. Jezo, M. Klasen, D.R. Lamprea, F. Lyonnet and I. Schienbein, NLO + NLL limits on Wand Zgauge boson masses in general extensions of the Standard Model, JHEP 12 (2014) 092 [arXiv:1410.4692] [INSPIRE].CrossRefADSGoogle Scholar
  18. [18]
    E. Accomando, D. Becciolini, S. De Curtis, D. Dominici, L. Fedeli and C. Shepherd-Themistocleous, Interference effects in heavy W-boson searches at the LHC, Phys. Rev. D 85 (2012) 115017 [arXiv:1110.0713] [INSPIRE].ADSGoogle Scholar
  19. [19]
    CMS collaboration, Search for new physics in final states with a tau and missing transverse energy using pp collisions at \( \sqrt{s}=8 \) TeV, CMS-PAS-EXO-12-011 (2015) [INSPIRE].
  20. [20]
    CMS collaboration, Search for physics beyond the standard model in final states with a lepton and missing transverse energy in proton-proton collisions at \( \sqrt{s}=8 \) TeV, Phys. Rev. D 91 (2015) 092005 [arXiv:1408.2745] [INSPIRE].
  21. [21]
    R. Hamberg, W.L. van Neerven and T. Matsuura, A Complete calculation of the order α s2 correction to the Drell-Yan K factor, Nucl. Phys. B 359 (1991) 343 [Erratum ibid. B 644 (2002) 403] [INSPIRE].
  22. [22]
    W.L. van Neerven and E.B. Zijlstra, The O(α s2) corrected Drell-Yan K-factor in the DIS and MS scheme, Nucl. Phys. B 382 (1992) 11 [Erratum ibid. B 680 (2004) 513] [INSPIRE].
  23. [23]
    R. Hamberg, T. Matsuura and W. van Neerven, Total cross sections for Z- and W-production, ZWPROD program (1989–2002),
  24. [24]
    S. Kretzer, H.L. Lai, F.I. Olness and W.K. Tung, CTEQ6 parton distributions with heavy quark mass effects, Phys. Rev. D 69 (2004) 114005 [hep-ph/0307022] [INSPIRE].ADSGoogle Scholar
  25. [25]
    S. Godfrey and T. Martin, ZDiscovery Reach at Future Hadron Colliders: A Snowmass White Paper, in Community Summer Study 2013: Snowmass on the Mississippi. (CSS2013), Minneapolis, MN, U.S.A., July 29–August 6 2013 [arXiv:1309.1688] [INSPIRE].
  26. [26]
    M. Carena, A. Daleo, B.A. Dobrescu and T.M.P. Tait, Zgauge bosons at the Tevatron, Phys. Rev. D 70 (2004) 093009 [hep-ph/0408098] [INSPIRE].ADSGoogle Scholar
  27. [27]
    F. Petriello and S. Quackenbush, Measuring Zcouplings at the CERN LHC, Phys. Rev. D 77 (2008) 115004 [arXiv:0801.4389] [INSPIRE].ADSGoogle Scholar
  28. [28]
    M. Cvetič and S. Godfrey, Discovery and identification of extra gauge bosons, hep-ph/9504216 [INSPIRE].
  29. [29]
    P. Langacker, R.W. Robinett and J.L. Rosner, New Heavy Gauge Bosons in pp and \( p\overline{p} \) Collisions, Phys. Rev. D 30 (1984) 1470 [INSPIRE].ADSGoogle Scholar
  30. [30]
    T.G. Rizzo, Indirect Searches for Z-like Resonances at the LHC, JHEP 08 (2009) 082 [arXiv:0904.2534] [INSPIRE].CrossRefADSGoogle Scholar
  31. [31]
    M. Dittmar, Neutral current interference in the TeV region: The Experimental sensitivity at the LHC, Phys. Rev. D 55 (1997) 161 [hep-ex/9606002] [INSPIRE].ADSGoogle Scholar
  32. [32]
    S. Alekhin et al., The PDF4LHC Working Group Interim Report, arXiv:1101.0536 [INSPIRE].

Copyright information

© The Author(s) 2016

Authors and Affiliations

  • Elena Accomando
    • 1
    Email author
  • Alexander Belyaev
    • 1
  • Juri Fiaschi
    • 1
  • Ken Mimasu
    • 2
  • Stefano Moretti
    • 1
  • Claire Shepherd-Themistocleous
    • 3
  1. 1.School of Physics and AstronomyUniversity of Southampton, Highfield CampusSouthamptonU.K.
  2. 2.School of Physics and AstronomyUniversity of SussexBrightonU.K.
  3. 3.Particle Physics Department, STFC, Rutherford Appleton LaboratoryOxfordshireU.K.

Personalised recommendations