Search for doubly charged Higgs boson production in multi-lepton final states using 139 fb$$^{-1}$$ of proton–proton collisions at $$\sqrt{s}$$ = 13 TeV with the ATLAS detector

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jats:titleAbstract</jats:title>jats:pA search for pair production of doubly charged Higgs bosons (jats:inline-formulajats:alternativesjats:tex-math$$H^{\pm \pm }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula>), each decaying into a pair of prompt, isolated, and highly energetic leptons with the same electric charge, is presented. The search uses a proton–proton collision data sample at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 139 fbjats:inline-formulajats:alternativesjats:tex-math$$^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msup <mml:mrow /> mml:mrow mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> recorded by the ATLAS detector during Run 2 of the Large Hadron Collider (LHC). This analysis focuses on same-charge leptonic decays, jats:inline-formulajats:alternativesjats:tex-math$$H^{\pm \pm } !\rightarrow \ell ^{\pm } \ell ^{\prime \pm }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> <mml:mspace /> mml:mo→</mml:mo> mml:msup mml:miℓ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miℓ</mml:mi> mml:mrow mml:mo′</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> where jats:inline-formulajats:alternativesjats:tex-math$$\ell , \ell ^\prime !=!e, \mu , \tau $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miℓ</mml:mi> mml:mo,</mml:mo> mml:msup mml:miℓ</mml:mi> mml:mo′</mml:mo> </mml:msup> <mml:mspace /> mml:mo=</mml:mo> <mml:mspace /> mml:mie</mml:mi> mml:mo,</mml:mo> mml:miμ</mml:mi> mml:mo,</mml:mo> mml:miτ</mml:mi> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, in two-, three-, and four-lepton channels, but only considers final states which include electrons or muons. No evidence of a signal is observed. Corresponding upper limits on the production cross-section of a doubly charged Higgs boson are derived, as a function of its mass jats:inline-formulajats:alternativesjats:tex-math$$m(H^{\pm \pm })$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:mim</mml:mi> mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo)</mml:mo> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, at 95% confidence level. Assuming that the branching ratios to each of the possible leptonic final states are equal, jats:inline-formulajats:alternativesjats:tex-math$$\mathcal {B}(H^{\pm \pm } \rightarrow e^\pm e^\pm ) = \mathcal {B}(H^{\pm \pm } \rightarrow e^\pm \mu ^\pm ) = \mathcal {B}(H^{\pm \pm } \rightarrow \mu ^\pm \mu ^\pm ) = \mathcal {B}(H^{\pm \pm } \rightarrow e^\pm \tau ^\pm ) = \mathcal {B}(H^{\pm \pm } \rightarrow \mu ^\pm \tau ^\pm ) = \mathcal {B}(H^{\pm \pm } \rightarrow \tau ^\pm \tau ^\pm ) = 1/6$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:mie</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:mie</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:mie</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miμ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:miμ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miμ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:mie</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miτ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:miμ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miτ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:miB</mml:mi> mml:mrow mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo→</mml:mo> mml:msup mml:miτ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:msup mml:miτ</mml:mi> mml:mo±</mml:mo> </mml:msup> mml:mo)</mml:mo> </mml:mrow> mml:mo=</mml:mo> mml:mn1</mml:mn> mml:mo/</mml:mo> mml:mn6</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, the observed (expected) lower limit on the mass of a doubly charged Higgs boson is 1080 GeV (1065 GeV) within the left-right symmetric type-II seesaw model, which is the strongest limit to date produced by the ATLAS Collaboration. Additionally, this paper provides the first direct test of the Zee–Babu neutrino mass model at the LHC, yielding an observed (expected) lower limit of jats:inline-formulajats:alternativesjats:tex-math$$m(H^{\pm \pm })$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:mim</mml:mi> mml:mo(</mml:mo> mml:msup mml:miH</mml:mi> mml:mrow mml:mo±</mml:mo> mml:mo±</mml:mo> </mml:mrow> </mml:msup> mml:mo)</mml:mo> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> = 900 GeV (880 GeV).</jats:p>

Description

Acknowledgements: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; ANID, Chile; CAS, MOST and NSFC, China; Minciencias, Colombia; MEYS CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF and MPG, Germany; GSRI, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DSI/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TENMAK, Türkiye; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada and CRC, Canada; PRIMUS 21/SCI/017 and UNCE SCI/013, Czech Republic; COST, ERC, ERDF, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union; Investissements d’Avenir Labex, Investissements d’Avenir Idex and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and MINERVA, Israel; Norwegian Financial Mechanism 2014–2021, Norway; NCN and NAWA, Poland; La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya and PROMETEO and GenT Programmes Generalitat Valenciana, Spain; Göran Gustafssons Stiftelse, Sweden; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [96].

Keywords
5107 Particle and High Energy Physics, 51 Physical Sciences
Journal Title
The European Physical Journal C
Conference Name
Journal ISSN
1434-6044
1434-6052
Volume Title
83
Publisher
Springer Science and Business Media LLC