CMS-PAS-EXO-21-003

CMS-PAS-EXO-21-003
Probing Majorana neutrinos and the Weinberg operator in the same-charge dimuon channel through vector boson fusion processes in proton-proton collisions at $\sqrt{s}=$ 13 TeV
CMS Collaboration
March 2022

Abstract: A first search probing Majorana neutrinos and the Weinberg operator in vector boson fusion processes at the LHC is presented. The search is performed in the same-charge dimuon final state using a proton-proton collision data set, recorded by the CMS detector, at a center-of-mass energy of 13 TeV and corresponding to a total integrated luminosity of 138 fb $^{-1}$ . The final state consists of two well-identified isolated muons with the same charge, and two jets with a large rapidity separation as well as a large dijet mass. The results are found to agree with the predictions of the standard model. Constraints are derived on model parameters accordingly. These limits significantly extend the mass range probed for heavy Majorana neutrinos compared with previous searches at the LHC. They also serve as a first test of the Weinberg operator at colliders.
Links: CDS record (PDF) ; Physics Briefing ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 131 (2023) 011803. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Example Feynman diagrams of VBF processes with heavy Majorana neutrino production (left) and processes mediated by the Weinberg operator (right) at the LHC.
png pdf	Figure 1-a: Example Feynman diagrams of VBF processes with heavy Majorana neutrino production (left) and processes mediated by the Weinberg operator (right) at the LHC.
png pdf	Figure 1-b: Example Feynman diagrams of VBF processes with heavy Majorana neutrino production (left) and processes mediated by the Weinberg operator (right) at the LHC.
png pdf	Figure 2: Post-fit distributions of ${H_{\mathrm {T}}} / {p_{\mathrm {T}}} ^{\mu _{1}}$ . For the heavy Majorana neutrino analysis, the three CRs and the two ${\Delta \phi _{\ell \ell}}$ bins in the SR are fitted simultaneously. For the Weinberg operator analysis, the three CRs and the two ${{p_{\mathrm {T}}} ^\text {miss}}$ bins in the SR are fitted simultaneously. The lines indicate the scaled expected distributions of the heavy Majorana neutrino process with $m_{N} =$ 750 GeV (solid red), 1.5 TeV (dashed red), 5.0 TeV (dotted red), and of the Weinberg operator process (blue).
png pdf	Figure 3: Upper limits on ${\| V_{\mu N} \|}^{2}$ at the 95% CL as a function of $m_{N}$ . The black dashed curve is the expected upper limit, where one and two standard deviation bands are indicated in lime green and light yellow, respectively. The solid black curve is the observed upper limit. The red dashed curve indicates observed upper limits from Ref. [9], while the blue dashed curve shows the observed upper limits from Ref. [12]. Starting from $m_{N}$ around 650 GeV, the analysis presented in this note improves upon the upper limits from those references.

Tables
png pdf	Table 1: Signal region and WZ control region definitions.

Summary

In summary, this note presents the first search for TeV mass scale Majorana neutrinos and a first probe of the Weinberg operator at the LHC. Vector boson fusion processes resulting in a dimuon final state are studied. The results agree with the predictions from the standard model, and upper limits are set on the model parameters accordingly. For heavy Majorana neutrinos, upper limits on

$|V_{\mu N}|^{2}$ are set for the mass range 750 GeV

$< m_{N} <$ 25 TeV, which is a significant improvement compared to previous searches at the LHC. The highest mass exclusion at

$|V_{\mu N}|^{2}=$ 1 is around 23.30 TeV. For the Weinberg operator, the observed (expected) 95% confidence level upper limit on the effective

$\mu\mu$ Majorana mass is

$|m_{\mu\mu}|=$ 10.84 (12.84) GeV. This is the first time such constraints have been obtained for this process.

References
1	Particle Data Group Collaboration	Review of particle physics	PRD 98 (2018) 030001
2	S. Weinberg	Baryon- and lepton-nonconserving processes	PRL 43 (1979) 1566
3	GERDA Collaboration	Final results of GERDA on the search for neutrinoless double- $\beta$ decay	PRL 125 (2020) 252502	2009.06079
4	B. Fuks et al.	Probing the Weinberg operator at colliders	PRD 103 (2021) 115014	2012.09882
5	P. Minkowski	$\mu \to \mathrm{e} \gamma$ at a rate of one out of 1-billion muon decays?	PLB 67 (1977) 421
6	M. Gell-Mann, P. Ramond, and R. Slansky	Supergravity	Proceedings of the Supergravity Workshop at Stony Brook, P. Nieuwenhuizen and D. Freedman, eds.
7	T. Yanagida	Unified Theory and the Baryon Number in the Universe	Proceedings of the Workshop on the Unified Theory and the Baryon Number in the Universe, O. Sawada and A. Sugamoto, eds., (KEK)
8	R. N. Mohapatra and G. Senjanovi\ifmmode \acutec\else \'c\fi	Neutrino mass and spontaneous parity violation	PRL 44 (1980) 912
9	CMS Collaboration	Search for heavy neutral leptons in events with three charged leptons in proton-proton collisions at $\sqrt{s} =$ 13 TeV	PRL 120 (2018), no. 22, 221801	CMS-EXO-17-012 1802.02965
10	ATLAS Collaboration	Search for heavy neutral leptons in decays of $W$ bosons produced in 13 $TeV pp$ collisions using prompt and displaced signatures with the ATLAS detector	JHEP 10 (2019) 265	1905.09787
11	CMS Collaboration	Search for physics beyond the standard model in multilepton final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JHEP 03 (2020) 051	CMS-EXO-19-002 1911.04968
12	CMS Collaboration	Search for heavy majorana neutrinos in same-sign dilepton channels in proton-proton collisions at $\sqrt{s}=$ 13 TeV	JHEP 01 (2019) 122	CMS-EXO-17-028 1806.10905
13	CMS Collaboration	Search for a heavy right-handed W boson and a heavy neutrino in events with two same-flavor leptons and two jets at $\sqrt{s}=$ 13 TeV	JHEP 05 (2018) 148	CMS-EXO-17-011 1803.11116
14	ATLAS Collaboration	Search for heavy Majorana or Dirac neutrinos and right-handed $W$ gauge bosons in final states with two charged leptons and two jets at $\sqrt{s}=$ 13 TeV with the ATLAS detector	JHEP 01 (2019) 016	1809.11105
15	B. Fuks et al.	Majorana neutrinos in same-sign $W^\pm W^\pm$ scattering at the LHC: Breaking the TeV barrier	PRD 103 (2021) 055005	2011.02547
16	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
17	CMS Collaboration	Performance of the CMS Level-1 trigger in proton-proton collisions at $\sqrt{s} =$ 13 TeV	JINST 15 (2020) P10017	CMS-TRG-17-001 2006.10165
18	CMS Collaboration	The CMS trigger system	JINST 12 (2017) P01020	CMS-TRG-12-001 1609.02366
19	CMS Collaboration	Performance of electron reconstruction and selection with the CMS detector in proton-proton collisions at $\sqrt{s} =$ 8 TeV	JINST 10 (2015) P06005	CMS-EGM-13-001 1502.02701
20	CMS Collaboration	Performance of the CMS muon detector and muon reconstruction with proton-proton collisions at $\sqrt{s}=$ 13 TeV	JINST 13 (2018) P06015	CMS-MUO-16-001 1804.04528
21	CMS Collaboration	Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at $\sqrt{s} =$ 8 TeV	JINST 10 (2015) P08010	CMS-EGM-14-001 1502.02702
22	CMS Collaboration	Description and performance of track and primary-vertex reconstruction with the CMS tracker	JINST 9 (2014) P10009	CMS-TRK-11-001 1405.6569
23	CMS Collaboration	Particle-flow reconstruction and global event description with the CMS detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
24	CMS Collaboration	Performance of reconstruction and identification of $\tau$ leptons decaying to hadrons and $\nu_\tau$ in pp collisions at $\sqrt{s}=$ 13 TeV	JINST 13 (2018) P10005	CMS-TAU-16-003 1809.02816
25	CMS Collaboration	Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV	JINST 12 (2017) P02014	CMS-JME-13-004 1607.03663
26	CMS Collaboration	Performance of missing transverse momentum reconstruction in proton-proton collisions at $\sqrt{s} =$ 13 TeV using the CMS detector	JINST 14 (2019) P07004	CMS-JME-17-001 1903.06078
27	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	1405.0301
28	P. Nason and G. Zanderighi	$W^+ W^-$ , $W Z$ and $Z Z$ production in the POWHEG-BOX-V2	EPJC 74 (2014) 2702	1311.1365
29	J. M. Campbell, R. K. Ellis, and C. Williams	Vector boson pair production at the LHC	JHEP 07 (2011) 018	1105.0020
30	J. Alwall et al.	MadGraph 5: going beyond	JHEP 06 (2011) 128	1106.0522
31	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
32	T. Sjostrand et al.	An introduction to PYTHIA 8.2	CPC 191 (2015) 159	1410.3012
33	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
34	CMS Collaboration	Extraction and validation of a new set of CMS PYTHIA8 tunes from underlying-event measurements	EPJC 80 (2020) 4	CMS-GEN-17-001 1903.12179
35	J. Alwall et al.	Comparative study of various algorithms for the merging of parton showers and matrix elements in hadronic collisions	EPJC 53 (2008) 473--500	0706.2569
36	NNPDF Collaboration	Parton distributions for the LHC Run II	JHEP 04 (2015) 040	1410.8849
37	NNPDF Collaboration	Parton distributions from high-precision collider data	EPJC 77 (2017) 663	1706.00428
38	GEANT4 Collaboration	GEANT4--a simulation toolkit	NIMA 506 (2003) 250
39	M. Cacciari, G. P. Salam, and G. Soyez	FastJet user manual	EPJC 72 (2012) 1896	1111.6097
40	M. Cacciari, G. P. Salam, and G. Soyez	The anti- ${k_{\mathrm{T}}}$ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
41	CMS Collaboration	Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV	JINST 13 (2018) P05011	CMS-BTV-16-002 1712.07158
42	CMS Collaboration	Reconstruction and identification of $\tau$ lepton decays to hadrons and $\nu_\tau$ at CMS	JINST 11 (2016) P01019	CMS-TAU-14-001 1510.07488
43	D. Rainwater, R. Szalapski, and D. Zeppenfeld	Probing color-singlet exchange in $Z+2$ -jet events at the CERN LHC	PRD 54 (Dec, 1996) 6680
44	CMS Collaboration	Study of vector boson scattering and search for new physics in events with two same-sign leptons and two jets	PRL 114 (2015) 051801	CMS-SMP-13-015 1410.6315
45	A. L. Read	Presentation of search results: The CL $_{\text{s}}$ technique	JPG 28 (2002) 2693
46	T. Junk	Confidence level computation for combining searches with small statistics	NIMA 434 (1999) 435	hep-ex/9902006
47	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727
48	CMS Collaboration	Precision luminosity measurement in proton-proton collisions at $\sqrt{s} =$ 13 TeV in 2015 and 2016 at CMS		CMS-LUM-17-003 2104.01927
49	CMS Collaboration	CMS luminosity measurement for the 2017 data-taking period at $\sqrt{s} =$ 13 TeV	CMS-PAS-LUM-17-004	CMS-PAS-LUM-17-004
50	CMS Collaboration	CMS luminosity measurement for the 2018 data-taking period at $\sqrt{s} =$ 13 TeV	CMS-PAS-LUM-18-002	CMS-PAS-LUM-18-002
51	ATLAS Collaboration	Measurement of the inelastic proton-proton cross section at $\sqrt{s} =$ 13 TeV with the ATLAS detector at the LHC	PRL 117 (2016) 182002	1606.02625
52	CMS Collaboration	Measurement of the inelastic proton-proton cross section at $\sqrt{s}=$ 13 TeV	JHEP 07 (2018) 161	CMS-FSQ-15-005 1802.02613
53	CMS Collaboration	Jet energy scale and resolution performance with 13 TeV data collected by CMS in 2016-2018	CDS
54	A. Ballestrero et al.	Precise predictions for same-sign W-boson scattering at the LHC	EPJC 78 (2018) 671	1803.07943
55	J. Butterworth et al.	PDF4LHC recommendations for LHC Run II	JPG 43 (2016) 023001	1510.03865
56	CMS Collaboration	Measurement of the inclusive and differential Higgs boson production cross sections in the leptonic WW decay mode at $\sqrt{s} =$ 13 TeV	JHEP 03 (2021) 003	CMS-HIG-19-002 2007.01984