# Testing ATLAS *Z*+MET excess with LHC Run 2

## Abstract

The ATLAS collaboration reported a 3σ excess in the search of events containing on-*Z* dilepton, jets, and large missing momentum (MET) in the 8 TeV LHC run. Motivated by this excess, many models of new physics have been proposed. Recently, the ATLAS and CMS collaborations reported new results for similar *Z*+MET channels in the 13 TeV run. In this paper, we comprehensively discuss the consistency between the proposed models and the LHC results of Run 1 and Run 2. We find that in models with heavy gluino production, there is generically some tension between the 8 TeV and 13 TeV results. On the other hand, models with light squark production provide relatively better fitting to both results.

## Keywords

Supersymmetry Phenomenology## Notes

**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.

## References

- [1]ATLAS collaboration,
*Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets and large missing transverse momentum in*\( \sqrt{s}=8 \)*TeV pp collisions with the ATLAS detector*,*Eur. Phys. J.***C 75**(2015) 318 [arXiv:1503.03290] [INSPIRE]. - [2]G. Barenboim, J. Bernabeu, V.A. Mitsou, E. Romero and O. Vives,
*METing SUSY on the Z peak*,*Eur. Phys. J.***C 76**(2016) 57 [arXiv:1503.04184] [INSPIRE].ADSCrossRefGoogle Scholar - [3]
- [4]B. Allanach, A. Raklev and A. Kvellestad,
*Consistency of the recent ATLAS Z*+*E*_{T}^{miss}*excess in a simplified GGM model*,*Phys. Rev.***D 91**(2015) 095016 [arXiv:1504.02752] [INSPIRE].ADSGoogle Scholar - [5]U. Ellwanger,
*Possible explanation of excess events in the search for jets, missing transverse momentum and a Z boson in pp collisions*,*Eur. Phys. J.***C 75**(2015) 367 [arXiv:1504.02244] [INSPIRE].ADSCrossRefGoogle Scholar - [6]J. Cao, L. Shang, J.M. Yang and Y. Zhang,
*Explanation of the ATLAS Z-peaked excess in the NMSSM*,*JHEP***06**(2015) 152 [arXiv:1504.07869] [INSPIRE].ADSCrossRefGoogle Scholar - [7]K. Harigaya, M. Ibe and T. Kitahara,
*ATLAS on-Z excess via gluino-Higgsino-singlino decay chains in the NMSSM*,*JHEP***01**(2016) 030 [arXiv:1510.07691] [INSPIRE].ADSCrossRefGoogle Scholar - [8]X. Lu, S. Shirai and T. Terada,
*ATLAS Z excess in minimal supersymmetric standard model*,*JHEP***09**(2015) 204 [arXiv:1506.07161] [INSPIRE].ADSCrossRefGoogle Scholar - [9]S.P. Liew, A. Mariotti, K. Mawatari, K. Sakurai and M. Vereecken,
*Z-peaked excess in goldstini scenarios*,*Phys. Lett.***B 750**(2015) 539 [arXiv:1506.08803] [INSPIRE].ADSCrossRefGoogle Scholar - [10]A. Kobakhidze, N. Liu, L. Wu and J.M. Yang,
*ATLAS Z-peaked excess in the MSSM with a light sbottom or stop*,*Phys. Rev.***D 92**(2015) 075008 [arXiv:1504.04390] [INSPIRE].ADSGoogle Scholar - [11]J. Cao, L. Shang, J.M. Yang and Y. Zhang,
*Explanation of the ATLAS Z-peaked excess by squark pair production in the NMSSM*,*JHEP***10**(2015) 178 [arXiv:1507.08471] [INSPIRE].ADSCrossRefGoogle Scholar - [12]M. Cahill-Rowley, J.L. Hewett, A. Ismail and T.G. Rizzo,
*ATLAS Z + missing transverse energy excess in the MSSM*,*Phys. Rev.***D 92**(2015) 075029 [arXiv:1506.05799] [INSPIRE].ADSGoogle Scholar - [13]J.H. Collins, J.A. Dror and M. Farina,
*Mixed stops and the ATLAS on-Z excess*,*Phys. Rev.***D 92**(2015) 095022 [arXiv:1508.02419] [INSPIRE].ADSGoogle Scholar - [14]N. Vignaroli,
*Z-peaked excess from heavy gluon decays to vectorlike quarks*,*Phys. Rev.***D 91**(2015) 115009 [arXiv:1504.01768] [INSPIRE].ADSGoogle Scholar - [15]CMS collaboration,
*Search for physics beyond the standard model in events with two leptons, jets and missing transverse momentum in pp collisions at*\( \sqrt{s}=8 \)*TeV*,*JHEP***04**(2015) 124 [arXiv:1502.06031] [INSPIRE]. - [16]ATLAS collaboration,
*A search for supersymmetry in events containing a leptonically decaying Z boson, jets and missing transverse momentum in*\( \sqrt{s}=13 \)*TeV pp collisions with the ATLAS detector*, ATLAS-CONF-2015-082 (2015). - [17]CMS collaboration,
*Search for new physics in final states with two opposite-sign same-flavor leptons, jets and missing transverse momentum in pp collisions at*\( \sqrt{s}=13 \)*TeV*, CMS-PAS-SUS-15-011 (2015). - [18]M. Schreyer, A. Redelbach and R. Ströhmer,
*Search for supersymmetry in events containing light leptons, jets and missing transverse momentum in*\( \sqrt{s}=8 \)*T eV pp collisions with the ATLAS detector*, Ph.D. thesis, Universität Würzburg, Würzburg, Germany (2015).Google Scholar - [19]P. Meade, N. Seiberg and D. Shih,
*General gauge mediation*,*Prog. Theor. Phys. Suppl.***177**(2009) 143 [arXiv:0801.3278] [INSPIRE].ADSMathSciNetCrossRefMATHGoogle Scholar - [20]M. Buican, P. Meade, N. Seiberg and D. Shih,
*Exploring general gauge mediation*,*JHEP***03**(2009) 016 [arXiv:0812.3668] [INSPIRE].ADSMathSciNetCrossRefGoogle Scholar - [21]J.D. Wells,
*Implications of supersymmetry breaking with a little hierarchy between gauginos and scalars*, hep-ph/0306127 [INSPIRE]. - [22]
- [23]N. Arkani-Hamed and S. Dimopoulos,
*Supersymmetric unification without low energy supersymmetry and signatures for fine-tuning at the LHC*,*JHEP***06**(2005) 073 [hep-th/0405159] [INSPIRE].ADSCrossRefGoogle Scholar - [24]G.F. Giudice and A. Romanino,
*Split supersymmetry*,*Nucl. Phys.***B 699**(2004) 65 [*Erratum ibid.***B 706**(2005) 487] [hep-ph/0406088] [INSPIRE]. - [25]N. Arkani-Hamed, S. Dimopoulos, G.F. Giudice and A. Romanino,
*Aspects of split supersymmetry*,*Nucl. Phys.***B 709**(2005) 3 [hep-ph/0409232] [INSPIRE]. - [26]L.J. Hall and Y. Nomura,
*Spread supersymmetry*,*JHEP***01**(2012) 082 [arXiv:1111.4519] [INSPIRE].ADSMathSciNetCrossRefMATHGoogle Scholar - [27]L.J. Hall, Y. Nomura and S. Shirai,
*Spread supersymmetry with Wino LSP: gluino and dark matter signals*,*JHEP***01**(2013) 036 [arXiv:1210.2395] [INSPIRE].ADSCrossRefGoogle Scholar - [28]Y. Nomura and S. Shirai,
*Supersymmetry from typicality: TeV-scale gauginos and PeV-scale squarks and sleptons*,*Phys. Rev. Lett.***113**(2014) 111801 [arXiv:1407.3785] [INSPIRE].ADSCrossRefGoogle Scholar - [29]M. Ibe and T.T. Yanagida,
*The lightest Higgs boson mass in pure gravity mediation model*,*Phys. Lett.***B 709**(2012) 374 [arXiv:1112.2462] [INSPIRE].ADSCrossRefGoogle Scholar - [30]M. Ibe, S. Matsumoto and T.T. Yanagida,
*Pure gravity mediation with m*_{3/2}= 10*-*100*TeV*,*Phys. Rev.***D 85**(2012) 095011 [arXiv:1202.2253] [INSPIRE].ADSGoogle Scholar - [31]A. Arvanitaki, N. Craig, S. Dimopoulos and G. Villadoro,
*Mini-split*,*JHEP***02**(2013) 126 [arXiv:1210.0555] [INSPIRE].ADSCrossRefGoogle Scholar - [32]N. Arkani-Hamed, A. Gupta, D.E. Kaplan, N. Weiner and T. Zorawski,
*Simply unnatural supersymmetry*, arXiv:1212.6971 [INSPIRE]. - [33]M. Toharia and J.D. Wells,
*Gluino decays with heavier scalar superpartners*,*JHEP***02**(2006) 015 [hep-ph/0503175] [INSPIRE]. - [34]P. Gambino, G.F. Giudice and P. Slavich,
*Gluino decays in split supersymmetry*,*Nucl. Phys.***B 726**(2005) 35 [hep-ph/0506214] [INSPIRE]. - [35]R. Sato, S. Shirai and K. Tobioka,
*Gluino decay as a probe of high scale supersymmetry breaking*,*JHEP***11**(2012) 041 [arXiv:1207.3608] [INSPIRE].ADSCrossRefGoogle Scholar - [36]R. Sato, S. Shirai and K. Tobioka,
*Flavor of gluino decay in high-scale supersymmetry*,*JHEP***10**(2013) 157 [arXiv:1307.7144] [INSPIRE].ADSCrossRefGoogle Scholar - [37]C. Cheung, Y. Nomura and J. Thaler,
*Goldstini*,*JHEP***03**(2010) 073 [arXiv:1002.1967] [INSPIRE].ADSMathSciNetCrossRefMATHGoogle Scholar - [38]ATLAS collaboration,
*Search for strong production of supersymmetric particles in final states with missing transverse momentum and at least three b-jets at*\( \sqrt{s}=8 \)*TeV proton-proton collisions with the ATLAS detector*,*JHEP***10**(2014) 024 [arXiv:1407.0600] [INSPIRE]. - [39]D.B. Kaplan and H. Georgi, SU(2) × U(1)
*breaking by vacuum misalignment*,*Phys. Lett.***B 136**(1984) 183 [INSPIRE].ADSCrossRefGoogle Scholar - [40]L. Randall and R. Sundrum,
*A large mass hierarchy from a small extra dimension*,*Phys. Rev. Lett.***83**(1999) 3370 [hep-ph/9905221] [INSPIRE]. - [41]J. Alwall et al.,
*The automated computation of tree-level and next-to-leading order differential cross sections and their matching to parton shower simulations*,*JHEP***07**(2014) 079 [arXiv:1405.0301] [INSPIRE].ADSCrossRefGoogle Scholar - [42]J. Alwall, M. Herquet, F. Maltoni, O. Mattelaer and T. Stelzer,
*MadGraph 5: going beyond*,*JHEP***06**(2011) 128 [arXiv:1106.0522] [INSPIRE].ADSCrossRefMATHGoogle Scholar - [43]T. Sjöstrand, S. Mrenna and P.Z. Skands,
*PYTHIA 6.4 physics and manual*,*JHEP***05**(2006) 026 [hep-ph/0603175] [INSPIRE]. - [44]DELPHES 3 collaboration, J. de Favereau et al.,
*DELPHES 3, a modular framework for fast simulation of a generic collider experiment*,*JHEP***02**(2014) 057 [arXiv:1307.6346] [INSPIRE]. - [45]M. Cacciari, G.P. Salam and G. Soyez,
*FastJet user manual*,*Eur. Phys. J.***C 72**(2012) 1896 [arXiv:1111.6097] [INSPIRE].ADSCrossRefGoogle Scholar - [46]M. Cacciari and G.P. Salam,
*Dispelling the N*^{3}*myth for the k*_{t}*jet-finder*,*Phys. Lett.***B 641**(2006) 57 [hep-ph/0512210] [INSPIRE]. - [47]J. Alwall et al.,
*Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions*,*Eur. Phys. J.***C 53**(2008) 473 [arXiv:0706.2569] [INSPIRE].ADSCrossRefGoogle Scholar - [48]J. Pumplin, D.R. Stump, J. Huston, H.L. Lai, P.M. Nadolsky and W.K. Tung,
*New generation of parton distributions with uncertainties from global QCD analysis*,*JHEP***07**(2002) 012 [hep-ph/0201195] [INSPIRE]. - [49]W. Beenakker, R. Hopker, M. Spira and P.M. Zerwas,
*Squark and gluino production at hadron colliders*,*Nucl. Phys.***B 492**(1997) 51 [hep-ph/9610490] [INSPIRE]. - [50]A. Kulesza and L. Motyka,
*Threshold resummation for squark-antisquark and gluino-pair production at the LHC*,*Phys. Rev. Lett.***102**(2009) 111802 [arXiv:0807.2405] [INSPIRE].ADSCrossRefGoogle Scholar - [51]A. Kulesza and L. Motyka,
*Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC*,*Phys. Rev.***D 80**(2009) 095004 [arXiv:0905.4749] [INSPIRE].ADSGoogle Scholar - [52]W. Beenakker, S. Brensing, M. Krämer, A. Kulesza, E. Laenen and I. Niessen,
*Soft-gluon resummation for squark and gluino hadroproduction*,*JHEP***12**(2009) 041 [arXiv:0909.4418] [INSPIRE].ADSCrossRefGoogle Scholar - [53]W. Beenakker et al.,
*Squark and gluino hadroproduction*,*Int. J. Mod. Phys.***A 26**(2011) 2637 [arXiv:1105.1110] [INSPIRE].ADSCrossRefGoogle Scholar - [54]W. Beenakker, M. Krämer, T. Plehn, M. Spira and P.M. Zerwas,
*Stop production at hadron colliders*,*Nucl. Phys.***B 515**(1998) 3 [hep-ph/9710451] [INSPIRE]. - [55]W. Beenakker et al.,
*Supersymmetric top and bottom squark production at hadron colliders*,*JHEP***08**(2010) 098 [arXiv:1006.4771] [INSPIRE].ADSCrossRefMATHGoogle Scholar - [56]A. Alloul, N.D. Christensen, C. Degrande, C. Duhr and B. Fuks,
*FeynRules 2.0 — A complete toolbox for tree-level phenomenology*,*Comput. Phys. Commun.***185**(2014) 2250 [arXiv:1310.1921] [INSPIRE]. - [57]C. Degrande et al.,
*UFO — The Universal FeynRules Output*,*Comput. Phys. Commun.***183**(2012) 1201 [arXiv:1108.2040] [INSPIRE].ADSCrossRefGoogle Scholar - [58]ATLAS collaboration,
*Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using*\( \sqrt{s}=8 \)*TeV proton-proton collision data*,*JHEP***09**(2014) 176 [arXiv:1405.7875] [INSPIRE]. - [59]ATLAS collaboration,
*Search for squarks and gluinos in final states with jets and missing transverse momentum at*\( \sqrt{s}=13 \)*TeV with the ATLAS detector*, ATLAS-CONF-2015-062 (2015). - [60]ATLAS collaboration,
*Search for supersymmetry in events with four or more leptons in*\( \sqrt{s}=13 \)*TeV pp collisions with the ATLAS detector*,*Phys. Rev.***D 90**(2014) 052001 [arXiv:1405.5086] [INSPIRE]. - [61]CMS collaboration,
*Search for anomalous production of events with three or more leptons in pp collisions at*\( \sqrt{s}=8 \)*TeV*,*Phys. Rev.***D 90**(2014) 032006 [arXiv:1404.5801] [INSPIRE]. - [62]Particle Data Group collaboration, K.A. Olive et al.,
*Review of particle physics*,*Chin. Phys.***C 38**(2014) 090001 [INSPIRE]. - [63]ATLAS collaboration,
*Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at*\( \sqrt{s}=8 \)*TeV with the ATLAS detector*,*JHEP***04**(2015) 116 [arXiv:1501.03555] [INSPIRE]. - [64]ATLAS collaboration,
*Search for gluinos in events with an isolated lepton, jets and missing transverse momentum at*\( \sqrt{s}=13 \)*TeV with the ATLAS detector*, ATLAS-CONF-2015-076 (2015). - [65]R. Ding, Y. Fan, J. Li, T. Li and B. Zhu,
*The ATLAS leptonic-Z excess from light squark productions in the NMSSM extension with a heavy Dirac gluino*, arXiv:1508.07452 [INSPIRE]. - [66]ATLAS collaboration,
*Search for pair-produced third-generation squarks decaying via charm quarks or in compressed supersymmetric scenarios in pp collisions at*\( \sqrt{s}=8 \)*TeV with the ATLAS detector*,*Phys. Rev.***D 90**(2014) 052008 [arXiv:1407.0608] [INSPIRE].