# The emergence of multi-lepton anomalies at the LHC and their compatibility with new physics at the EW scale

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## Abstract

A recent study [1] has shown that a simplified model predicting a heavy scalar of mass 270 GeV (*H* ) that decays to a Standard Model (SM) Higgs boson in association with a scalar singlet of mass 150 GeV (*S*) can accommodate several anomalous multi-lepton results in proton-proton collisions at the Large Hadron Collider (LHC). With this in mind, the goal of this article is to provide a more formal study of a wider set of LHC results pertaining to the production of multiple leptons. We find that a combination of such results lead to strong discrepancies between the data and SM Monte Carlo predictions. These discrepancies appear in corners of the phase-space where different SM processes dominate, indicating that the potential mismodeling of a single SM process is unlikely to explain them. Systematic uncertainties from the prediction of SM processes evaluated with currently available tools seem unable to explain away these discrepancies. A combination is able to constrain the simplified model’s single degree of freedom *β*^{2}, related to the size of the Yukawa coupling of *H* to the top quark, to a value of 2*.*92 *±* 0*.*35. This is in contrast to the absence of signal, where *βg* = 0. This result is discussed in the independent contexts of both potential for new physics in the existing LHC data as well as the limitations of our current understanding of the SM. That being said, QCD NNLO and EW NLO corrections in di-lepton final states are not expected to change the conclusions of this study. New results pertaining to the production of two opposite sign different flavour charged leptons with a full jet veto further confirm the presence of anomalies in similar corners of the leptonic phase-space.

## Keywords

Hadron-Hadron scattering (experiments)## Notes

### **Open Access**

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## References

- [1]S. von Buddenbrock, A.S. Cornell, A. Fadol, M. Kumar, B. Mellado and X. Ruan, Multi-l epton signatures of additional sca lar bosons beyond the Standard Model at the LHC, J.
*Phys.*G 45 (2018) 115003 [arXiv :1711.07874] [INSPIRE]. - [2]S. von Buddenbrock et al.,
*The compatibility of LHC Run 1 data with a heavy scalar of mass around*270*G eV ,*arXiv:1506 .00612 [INSPIRE]. - [3]ATLAS collaboration,
*Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Produ ction in pp Collisions at JS*=*8 Te V Using the ATLAS D etector, Phys. Rev. Lett.*114 (2015) 142001 [arXiv: 1412 . 4742] [INSPIRE]. - [4]CMS collaboration, Measurements of t\( \overline{\mathrm{t}} \)
*spin correlations and top quark polarization using dilepton final states in pp collisions at*\( \sqrt{s} \) = 8*TeV*,*Phys. Rev.***D 93**(2016) 052007 [arXiv:1601.01107] [INSPIRE]. - [5]S. von Buddenbrock et al.,
*Phenomenological signatures of additional scalar bosons at the LHC*,*Eur. Phys. J.***C 76**(2016) 580 [arXiv:1606.01674] [INSPIRE].ADSCrossRefGoogle Scholar - [6]ATLAS collaboration,
*Search for dark matter in association with a Higgs boson decaying to two photons at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*,*Phys. Rev.***D 96**(2017) 112004 [arXiv:1706.03948] [INSPIRE]. - [7]S. von Buddenbrock et al.,
*Constraints on a 2HDM with a singlet scalar and implications in the search for heavy bosons at the LHC*, arXiv:1809.06344 [INSPIRE]. - [8]ATLAS collaboration,
*Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at*\( \sqrt{s} \) = 8*TeV with ATLAS*,*JHEP***09**(2014) 112 [arXiv:1407.4222] [INSPIRE]. - [9]ATLAS collaboration,
*Fiducial and differential cross sections of Higgs boson production measured in the four-lepton decay channel in pp collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*Phys. Lett.***B 738**(2014) 234 [arXiv:1408.3226] [INSPIRE]. - [10]CMS collaboration,
*Measurement of differential cross sections for Higgs boson production in the diphoton decay channel in pp collisions at*\( \sqrt{s} \) = 8*TeV*,*Eur. Phys. J.***C 76**(2016) 13 [arXiv:1508.07819] [INSPIRE]. - [11]CMS collaboration,
*Measurement of differential and integrated fiducial cross sections for Higgs boson production in the four-lepton decay channel in pp collisions at*\( \sqrt{s} \) = 7*and*8*TeV*,*JHEP***04**(2016) 005 [arXiv:1512.08377] [INSPIRE]. - [12]ATLAS collaboration,
*Searches for Higgs boson pair production in the hh → bbτ τ, γγW W*^{∗}*, γγbb, bbbb channels with the ATLAS detector*,*Phys. Rev.***D 92**(2015) 092004 [arXiv:1509.04670] [INSPIRE]. - [13]CMS collaboration,
*Search for two Higgs bosons in final states containing two photons and two bottom quarks in proton-proton collisions at*8*TeV*,*Phys. Rev.***D 94**(2016) 052012 [arXiv:1603.06896] [INSPIRE]. - [14]CMS collaboration,
*Searches for a heavy scalar boson H decaying to a pair of*125*GeV Higgs bosons hh or for a heavy pseudoscalar boson A decaying to Zh, in the final states with h → τ τ*,*Phys. Lett.***B 755**(2016) 217 [arXiv:1510.01181] [INSPIRE]. - [15]CMS collaboration,
*Searches for heavy Higgs bosons in two-Higgs-doublet models and for t → ch decay using multilepton and diphoton final states in pp collisions at*8*TeV*,*Phys. Rev.***D 90**(2014) 112013 [arXiv:1410.2751] [INSPIRE]. - [16]ATLAS collaboration,
*Search for a high-mass Higgs boson decaying to a W boson pair in pp collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*JHEP***01**(2016) 032 [arXiv:1509.00389] [INSPIRE]. - [17]ATLAS collaboration,
*Search for an additional, heavy Higgs boson in the H → Z Z decay channel at*\( \sqrt{s} \) = 8*TeV in pp collision data with the ATLAS detector*,*Eur. Phys. J.***C 76**(2016) 45 [arXiv:1507.05930] [INSPIRE]. - [18]CMS collaboration,
*Search for a Higgs boson in the mass range from*145*to*1000*GeV decaying to a pair of W or Z bosons*,*JHEP***10**(2015) 144 [arXiv:1504.00936] [INSPIRE]. - [19]ATLAS collaboration,
*Search for H → γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at*7*TeV and*8*TeV with the ATLAS detector*,*Phys. Lett.***B 740**(2015) 222 [arXiv:1409.3122] [INSPIRE]. - [20]ATLAS collaboration,
*Search for the associated production of the Higgs boson with a top quark pair in multilepton final states with the ATLAS detector*,*Phys. Lett.***B 749**(2015) 519 [arXiv:1506.05988] [INSPIRE]. - [21]ATLAS collaboration, Search for the Standard Model Higgs boson produced in association with top quarks and decaying into
*b*\( \overline{b} \)*in pp collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*Eur. Phys. J.***C 75**(2015) 349 [arXiv:1503.05066] [INSPIRE]. - [22]CMS collaboration,
*Search for the associated production of the Higgs boson with a top-quark pair*,*JHEP***09**(2014) 087 [*Erratum JHEP***10**(2014) 106] [arXiv:1408.1682] [INSPIRE]. - [23]ATLAS collaboration,
*Combined measurement of the total and differential cross sections in the H → γγ and the H → Z Z*^{∗}*→*4*f decay channels at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*, ATLAS-CONF-2019-032 (2019) [INSPIRE]. - [24]CMS collaboration,
*Measurements of properties of the Higgs boson in the four-lepton final state in proton-proton collisions at*\( \sqrt{s} \) = 13 TeV, CMS-PAS-HIG-19-001 (2019) [INSPIRE]. - [25]CMS collaboration,
*Measurement of inclusive and differential Higgs boson production cross sections in the diphoton decay channel in proton-proton collisions at*\( \sqrt{s} \) = 13*TeV*,*JHEP***01**(2019) 183 [arXiv:1807.03825] [INSPIRE]. - [26]ATLAS collaboration,
*Measurement of lepton differential distributions and the top quark mass in t*\( \overline{t} \)*production in pp collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*Eur. Phys. J.***C 77**(2017) 804 [arXiv:1709.09407] [INSPIRE]. - [27]ATLAS collaboration,
*Measurement of total and differential W*^{+}*W*^{−}*production cross sections in proton-proton collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector and limits on anomalous triple-gauge-boson couplings*,*JHEP***09**(2016) 029 [arXiv:1603.01702] [INSPIRE]. - [28]ATLAS collaboration,
*Measurement of W*^{+}*W*^{−}*production in association with one jet in proton-proton collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*Phys. Lett.***B 763**(2016) 114 [arXiv:1608.03086] [INSPIRE]. - [29]CMS collaboration,
*Measurement of the W*^{+}*W*^{−}*cross section in pp collisions at*\( \sqrt{s} \) = 8*TeV and limits on anomalous gauge couplings*,*Eur. Phys. J.***C 76**(2016) 401 [arXiv:1507.03268] [INSPIRE]. - [30]CMS collaboration,
*Measurement of the t*\( \overline{t} \)*production cross section in the dilepton channel in pp collisions at*\( \sqrt{s} \) = 8*TeV*,*JHEP***02**(2014) 024 [*Erratum JHEP***02**(2014) 102] [arXiv:1312.7582] [INSPIRE]. - [31]M. Farina, C. Grojean, F. Maltoni, E. Salvioni and A. Thamm,
*Lifting degeneracies in Higgs couplings using single top production in association with a Higgs boson*,*JHEP***05**(2013) 022 [arXiv:1211.3736] [INSPIRE].ADSGoogle Scholar - [32]ATLAS collaboration,
*Measurements of the Higgs boson inclusive, differential and production cross sections in the*4*f decay channel at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*, ATLAS-CONF-2019-025 (2019) [INSPIRE]. - [33]T. Sjöstrand et al.,
*An Introduction to PYTHIA 8.2*,*Comput. Phys. Commun.***191**(2015) 159 [arXiv:1410.3012] [INSPIRE]. - [34]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]. - [35]LHC Higgs Cross Section Working Group,
*Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector*, FERMILAB-FN-1025-T (2016) [INSPIRE] and online at https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHXSWG. - [36]DELPHES 3 collaboration,
*DELPHES 3, A modular framework for fast simulation of a generic collider experiment*,*JHEP***02**(2014) 057 [arXiv:1307.6346] [INSPIRE].ADSGoogle Scholar - [37]D. Dercks, N. Desai, J.S. Kim, K. Rolbiecki, J. Tattersall and T. Weber,
*CheckMATE 2: From the model to the limit*,*Comput. Phys. Commun.***221**(2017) 383 [arXiv:1611.09856] [INSPIRE].ADSCrossRefGoogle Scholar - [38]M. Cacciari, G.P. Salam and G. Soyez,
*FastJet User Manual*,*Eur. Phys. J.***C 72**(2012) 1896 [arXiv:1111.6097] [INSPIRE].ADSCrossRefGoogle Scholar - [39]K. Cranmer, G. Lewis, L. Moneta, A. Shibata and W. Verkerke,
*HistFactory: A tool for creating statistical models for use with RooFit and RooStats*, CERN-OPEN-2012-016 (2012) [INSPIRE]. - [40]ATLAS collaboration,
*Analysis of events with b-jets and a pair of leptons of the same charge in pp collisions at*\( \sqrt{s} \) = 8*TeV with the ATLAS detector*,*JHEP***10**(2015) 150 [arXiv:1504.04605] [INSPIRE]. - [41]CMS collaboration,
*Search for production of a Higgs boson and a single top quark in multilepton final states in proton collisions at*\( \sqrt{s} \) = 13*TeV*, CMS-PAS-HIG-17-005 (2017) [INSPIRE]. - [42]CMS collaboration,
*Measurement of the production cross section for single top quarks in association with W bosons in proton-proton collisions at*\( \sqrt{s} \) = 13*TeV*,*JHEP***10**(2018) 117 [arXiv:1805.07399] [INSPIRE]. - [43]CMS collaboration,
*Measurements of the pp → W Z inclusive and differential production cross section and constraints on charged anomalous triple gauge couplings at*\( \sqrt{s} \) = 13*TeV*, CMS-PAS-SMP-18-002 (2018) [INSPIRE]. - [44]ATLAS collaboration,
*Search for new phenomena in events with same-charge leptons and b-jets in pp collisions at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*,*JHEP***12**(2018) 039 [arXiv:1807.11883] [INSPIRE]. - [45]ATLAS collaboration,
*Measurements of top-quark pair spin correlations in the eμ channel at*\( \sqrt{s} \) = 13*TeV using pp collisions in the ATLAS detector*, ATLAS-CONF-2018-027 (2018) [INSPIRE]. - [46]ATLAS collaboration,
*Measurement of W*^{±}*Z production cross sections and gauge boson polarisation in pp collisions at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*, ATLAS-CONF-2018-034 (2018) [INSPIRE]. - [47]S. Alioli, P. Nason, C. Oleari and E. Re,
*A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX*,*JHEP***06**(2010) 043 [arXiv:1002.2581] [INSPIRE].ADSCrossRefGoogle Scholar - [48]CMS collaboration, Measurements of differential cross sections for
*t*\( \overline{t} \)*production in proton-proton collisions at*\( \sqrt{s} \) = 13*TeV using events containing two leptons*, CMS-PAS-TOP-17-014 (2018) [INSPIRE]. - [49]ATLAS collaboration,
*Measurements of gluon-gluon fusion and vector-boson fusion Higgs boson production cross-sections in the H → WW*^{*}*→ eνμν decay channel in pp collisions at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*,*Phys. Lett.***B 789**(2019) 508 [arXiv:1808.09054] [INSPIRE]. - [50]ATLAS collaboration,
*Search for four-top-quark production in the single-lepton and opposite-sign dilepton final states in pp collisions at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*,*Phys. Rev.***D 99**(2019) 052009 [arXiv:1811.02305] [INSPIRE]. - [51]CMS collaboration,
*Measurements of tt differential cross sections in proton-proton collisions at*\( \sqrt{s} \) = 13*TeV using events containing two leptons*,*JHEP***02**(2019) 149 [arXiv:1811.06625] [INSPIRE]. - [52]A. Behring, M. Czakon, A. Mitov, A.S. Papanastasiou and R. Poncelet,
*Higher order corrections to spin correlations in top quark pair production at the LHC*,*Phys. Rev. Lett.***123**(2019) 082001 [arXiv:1901.05407] [INSPIRE].ADSCrossRefGoogle Scholar - [53]A. Denner and M. Pellen,
*NLO electroweak corrections to off-shell top-antitop production with leptonic decays at the LHC*,*JHEP***08**(2016) 155 [arXiv:1607.05571] [INSPIRE].ADSCrossRefGoogle Scholar - [54]B. Biedermann, A. Denner and L. Hofer,
*Next-to-leading-order electroweak corrections to the production of three charged leptons plus missing energy at the LHC*,*JHEP***10**(2017) 043 [arXiv:1708.06938] [INSPIRE].ADSCrossRefGoogle Scholar - [55]J. Baglio and N. Le Duc,
*Fiducial polarization observables in hadronic WZ production: A next-to-leading order QCD+EW study*,*JHEP***04**(2019) 065 [arXiv:1810.11034] [INSPIRE].ADSCrossRefGoogle Scholar - [56]
- [57]S. Dulat et al.,
*New parton distribution functions from a global analysis of quantum chromodynamics*,*Phys. Rev.***D 93**(2016) 033006 [arXiv:1506.07443] [INSPIRE].ADSGoogle Scholar - [58]L.A. Harland-Lang, A.D. Martin, P. Motylinski and R.S. Thorne,
*Parton distributions in the LHC era: MMHT 2014 PDFs*,*Eur. Phys. J.***C 75**(2015) 204 [arXiv:1412.3989] [INSPIRE].ADSCrossRefGoogle Scholar - [59]J. Butterworth et al.,
*PDF4LHC recommendations for LHC Run II*,*J. Phys.***G 43**(2016) 023001 [arXiv:1510.03865] [INSPIRE].ADSCrossRefGoogle Scholar - [60]ATLAS collaboration,
*Measurement of fiducial and differential W*^{+}*W*^{−}*production cross-sections at*\( \sqrt{s} \) = 13*TeV with the ATLAS detector*, arXiv:1905.04242 [INSPIRE]. - [61]T. Gehrmann et al.,
*W*^{+}*W*^{−}*Production at Hadron Colliders in Next to Next to Leading Order QCD*,*Phys. Rev. Lett.***113**(2014) 212001 [arXiv:1408.5243] [INSPIRE].ADSCrossRefGoogle Scholar - [62]M. Grazzini, S. Kallweit, S. Pozzorini, D. Rathlev and M. Wiesemann,
*W*^{+}*W production at the LHC: fiducial cross sections and distributions in NNLO QCD*,*JHEP***08**(2016) 140 [arXiv:1605.02716] [INSPIRE].ADSCrossRefGoogle Scholar - [63]K. Hamilton, T. Melia, P.F. Monni, E. Re and G. Zanderighi,
*Merging WW and WW*+*jet with MINLO*,*JHEP***09**(2016) 057 [arXiv:1606.07062] [INSPIRE].ADSCrossRefGoogle Scholar - [64]E. Re, M. Wiesemann and G. Zanderighi,
*NNLOPS accurate predictions for W*^{+}*W*^{−}*production*,*JHEP***12**(2018) 121 [arXiv:1805.09857] [INSPIRE].ADSCrossRefGoogle Scholar - [65]F. Caola, K. Melnikov, R. Röntsch and L. Tancredi,
*QCD corrections to W*^{+}*W*^{−}*production through gluon fusion*,*Phys. Lett.***B 754**(2016) 275 [arXiv:1511.08617] [INSPIRE]. - [66]B. Biedermann et al.,
*Next-to-leading-order electroweak corrections to pp → W*^{+}*W*^{−}*→*4*leptons at the LHC*,*JHEP***06**(2016) 065 [arXiv:1605.03419] [INSPIRE].ADSCrossRefGoogle Scholar - [67]GAMBIT collaboration,
*Combined collider constraints on neutralinos and charginos*,*Eur. Phys. J.***C 79**(2019) 395 [arXiv:1809.02097] [INSPIRE]. - [68]ATLAS collaboration,
*Search for Higgs boson pair production in the W W*^{(∗)}*W W*^{(∗)}*decay channel using ATLAS data recorded at*\( \sqrt{s} \) = 13*TeV*,*JHEP***05**(2019) 124 [arXiv:1811.11028] [INSPIRE]. - [69]S. Frixione, P. Nason and G. Ridolfi,
*A Positive-weight next-to-leading-order Monte Carlo for heavy flavour hadroproduction*,*JHEP***09**(2007) 126 [arXiv:0707.3088] [INSPIRE].ADSCrossRefGoogle Scholar - [70]E. Re,
*Single-top Wt-channel production matched with parton showers using the POWHEG method*,*Eur. Phys. J.***C 71**(2011) 1547 [arXiv:1009.2450] [INSPIRE].ADSCrossRefGoogle Scholar - [71]T. Jĕzo, J.M. Lindert, P. Nason, C. Oleari and S. Pozzorini,
*An NLO*+*PS generator for t*\( \overline{t} \)*and W t production and decay including non-resonant and interference effects*,*Eur. Phys. J.***C 76**(2016) 691 [arXiv:1607.04538] [INSPIRE].ADSCrossRefGoogle Scholar - [72]S. Frixione, E. Laenen, P. Motylinski, B.R. Webber and C.D. White,
*Single-top hadroproduction in association with a W boson*,*JHEP***07**(2008) 029 [arXiv:0805.3067] [INSPIRE].ADSCrossRefGoogle Scholar - [73]M. Grazzini, S. Kallweit, D. Rathlev and M. Wiesemann,
*W*^{±}*Z production at hadron colliders in NNLO QCD*,*Phys. Lett.***B 761**(2016) 179 [arXiv:1604.08576] [INSPIRE].ADSCrossRefGoogle Scholar - [74]M. Grazzini, S. Kallweit, D. Rathlev and M. Wiesemann,
*W*^{±}*Z production at the LHC: fiducial cross sections and distributions in NNLO QCD*,*JHEP***05**(2017) 139 [arXiv:1703.09065] [INSPIRE].ADSCrossRefGoogle Scholar - [75]M. Grazzini,
*Soft-gluon effects in WW production at hadron colliders*,*JHEP***01**(2006) 095 [hep-ph/0510337] [INSPIRE]. - [76]R. Frederix and M. Grazzini,
*Higher-order QCD effects in the h → Z Z search channel at the LHC*,*Phys. Lett.***B 662**(2008) 353 [arXiv:0801.2229] [INSPIRE].ADSCrossRefGoogle Scholar - [77]Y. Wang, C.S. Li, Z.L. Liu, D.Y. Shao and H.T. Li,
*Transverse-Momentum Resummation for Gauge Boson Pair Production at the Hadron Collider*,*Phys. Rev.***D 88**(2013) 114017 [arXiv:1307.7520] [INSPIRE].ADSGoogle Scholar - [78]T. Becher and M. Hager,
*Event-Based Transverse Momentum Resummation*,*Eur. Phys. J.***C 79**(2019) 665 [arXiv:1904.08325] [INSPIRE].ADSCrossRefGoogle Scholar