CMSEXO17011 ; CERNEP2018028  
Search for a heavy righthanded W boson and a heavy neutrino in events with two sameflavor leptons and two jets at $\sqrt{s} = $ 13 TeV  
CMS Collaboration  
29 March 2018  
JHEP 05 (2018) 148  
Abstract: A search for a heavy righthanded W boson ($ \mathrm{ W_R } $) decaying to a heavy righthanded neutrino and a charged lepton in events with two sameflavor leptons (e or $ \mu $) and two jets, is presented. The analysis is based on protonproton collision data, collected by the CMS Collaboration at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb$^{1}$. No significant excess above the standard model expectation is seen in the invariant mass distribution of the dilepton plus dijet system. Assuming that couplings are identical to those of the standard model, and that only one heavy neutrino flavor ${\mathrm {N_R}}$ contributes significantly to the $ \mathrm{ W_R } $ decay width, the region in the twodimensional ($ {m_{ \mathrm{ W_R } }} $, $ {m_{{\mathrm {N_R}} }} $) mass plane excluded at 95% confidence level extends to approximately ${m_{ \mathrm{ W_R } }} = $ 4.4 TeV and covers a large range of righthanded neutrino masses below the $ \mathrm{ W_R } $ boson mass. This analysis provides the most stringent limits on the $ \mathrm{ W_R } $ mass to date.  
Links: eprint arXiv:1803.11116 [hepex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; 
Figures  
png pdf 
Figure 1:
Kinematic distributions for events in the low dilepton mass control region with the DY SF applied. The dilepton mass (upper) and the scalar sum of all jet transverse momenta (lower) for the ee DY plus two jets selection are shown on the left. The $ {m_{\ell \ell \text {jj}}} $ (upper) and the dilepton transverse momentum (lower) for the $ {\mu} {\mu} $ DY plus two jets selection are shown on the right. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 1a:
Dilepton mass distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 1b:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 1c:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 1d:
Dilepton mass Scalar sum of all jet transverse momenta $ {m_{\ell \ell \text {jj}}} $ Dilepton transverse momentum distribution for events in the low dilepton mass control region with the DY SF applied, for the ee DY plus two jets selection. for the $ {\mu} {\mu} $ DY plus two jets selection. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 2:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the electron (left) and muon (right) channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 2a:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the electron channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 2b:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the low $ {m_{\ell \ell \text {jj}}} $ control region with the DY SF applied for the muon channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 3:
Kinematic distributions for events in the flavor control region with the DY SF applied. The dilepton mass (upper left), the $ {m_{\ell \ell \text {jj}}} $ (upper right), the scalar sum of all jet transverse momenta (lower left), and the number of jets (lower right) are shown. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 3a:
The dilepton mass distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 3b:
The $ {m_{\ell \ell \text {jj}}} $ sdistribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 3c:
The scalar sum of all jet transverse momenta distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 3d:
The number of jets distribution for events in the flavor control region with the DY SF applied. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. 
png pdf 
Figure 4:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the electron (left) and muon (right) channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plots represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. 
png pdf 
Figure 4a:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the electron channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. 
png pdf 
Figure 4b:
The $ {m_{\ell \ell \text {jj}}} $ distribution in the signal region for the muon channel. The uncertainty bands on the simulated background histograms include only statistical uncertainties. The uncertainty bars in the ratio plot represent combined statistical uncertainties of data and simulation. The gray error band around unity represents the systematic uncertainty on the simulation. 
png pdf 
Figure 5:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the electron channel on the left and for the muon channel on the right. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. 
png pdf 
Figure 5a:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the electron channel. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. 
png pdf 
Figure 5b:
Expected and observed 95% CL upper limits on the product of $\sigma ({\mathrm {p}} {\mathrm {p}}\to {\mathrm {W_R}})$ and branching fraction $B({\mathrm {W_R}} \to \ell \ell \text {jj})$ for the muon channel. The inner (green) band and the outer (yellow) band indicate the expected 68% and 95% CL exclusion regions. 
png pdf 
Figure 6:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the electron channel on the left and for the muon channel on the right. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thindotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. 
png pdf 
Figure 6a:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the electron channel. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thindotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. 
png pdf 
Figure 6b:
Upper limit on the cross section for different $ {\mathrm {W_R}} $ and ${\mathrm {N_R}}$ mass hypotheses, for the muon channel. The expected and observed exclusions are shown as the dotted (blue) curve and the solid (red) curve, respectively. The thindotted (blue) curves indicate the region in ($ {m_{{\mathrm {W_R}}}} $, ${m_{{\mathrm {N_R}}}})$ parameter space that is expected to be excluded at 68% CL in the case that no signal is present in the data. 
Tables  
png pdf 
Table 1:
Transfer factors applied to the number of events in the flavor control region to estimate the number of $ {{\mathrm {t}\overline {\mathrm {t}}}} $ events in the $ {{\mathrm {e}} {\mathrm {e}}\text {jj}} $ and $ {{\mu} {\mu} \text {jj}}$ signal regions. 
png pdf 
Table 2:
Effect of systematic uncertainties in candidate reconstruction efficiencies, energy scale and resolutions on the signal and background yields. The Signal column shows the range of uncertainties computed at each of the $ {\mathrm {W_R}} $ mass points. The Background column indicates the range of the uncertainties for the different backgrounds. 
png pdf 
Table 3:
Uncertainties affecting the $ {m_{\ell \ell \text {jj}}} $ distribution shape and normalization. The uncertainties in the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ SFs affect the $ {{\mathrm {t}\overline {\mathrm {t}}}} $ background, the uncertainties in the DY PDF and the DY factorization and renormalization scales affect the DY+jets background, and the uncertainty in the integrated luminosity affects both signal and backgrounds. 
png pdf 
Table 4:
Number of expected events for signal, DY+jets, $ {{\mathrm {t}\overline {\mathrm {t}}}} $, Other, and All backgrounds, as well as the observed number of events in different $ {\mathrm {W_R}} $ mass windows. All uncertainties are included in the expected number of events. In each table cell, the entry is of the form (mean $\pm $ stat $\pm $ syst). 
Summary 
A search for a righthanded analogue of the standard model W boson in the decay channel of two leptons and two jets has been presented. The analysis is based on protonproton collision data collected at $\sqrt{s} = $ 13 TeV by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb$^{1}$. No significant excess over the standard model background expectations is observed in the invariant mass distribution of the dilepton plus dijet system. Thus the 2.8$\sigma$ excess previously observed in data recorded by CMS at 8 TeV is not confirmed. Assuming that couplings are identical to those of the standard model, a region in the twodimensional plane ($ {m_{ \mathrm{ W_R } }} $, $ {m_{{\mathrm {N_R}} }} $) covering a large range of righthanded neutrino masses is excluded at 95% confidence level. A $ \mathrm{ W_R } $ boson decaying into a righthanded heavy neutrino with a mass ${m_{{\mathrm {N_R}} }}=1/2 {m_{\mathrm{ W_R }}}$ is excluded at 95% confidence level up to a mass of 4.4 TeV, providing the most stringent limit to date. 
References  
1  J. C. Pati and A. Salam  Lepton number as the fourth color  PRD 10 (1974) 275, .[Erratum: \it Phys. Rev. D\/ \bf 11 (1975) 703, \DOI10.1103/PhysRevD.11.703.2]  
2  R. N. Mohapatra and J. C. Pati  A natural leftright symmetry  PRD 11 (1975) 2558  
3  G. Senjanovic and R. N. Mohapatra  Exact leftright symmetry and spontaneous violation of parity  PRD 12 (1975) 1502  
4  W.Y. Keung and G. Senjanovic  Majorana neutrinos and the production of the righthanded charged gauge boson  PRL 50 (1983) 1427  
5  P. Adhya, D. R. Chaudhuri, and A. Raychaudhuri  Decay and decoupling of heavy righthanded Majorana neutrinos in the LR model  EPJC 19 (2001) 183  hepph/0006260 
6  P. S. B. Dev, R. N. Mohapatra, and Y. Zhang  Heavy righthanded neutrino dark matter in leftright models  MPLA 32 (2017) 1740007  1610.05738 
7  R. N. Mohapatra and G. Senjanovic  Neutrino mass and spontaneous parity violation  PRL 44 (1980) 912  
8  M. GellMann, P. Ramond, and R. Slansky  Complex spinors and unified theories  in Supergravity, P. V. Nieuwenhuizen and D. Z. Freedman, eds., p. 315 Elsevier, 1979 Conference number C790927  1306.4669 
9  CMS Collaboration  Search for heavy neutrinos and $ \mathrm {W} $ bosons with righthanded couplings in protonproton collisions at $ \sqrt{s} = $ 8 TeV  EPJC 74 (2014) 3149  CMSEXO13008 1407.3683 
10  CMS Collaboration  Search for heavy neutrinos or thirdgeneration leptoquarks in final states with two hadronically decaying $ \tau $ leptons and two jets in protonproton collisions at $ \sqrt{s}= $ 13 TeV  JHEP 03 (2017) 077  CMSEXO16016 1612.01190 
11  CMS Collaboration  Search for the thirdgeneration scalar leptoquarks and heavy righthanded neutrinos in final states with two tau leptons and two jets in protonproton collisions at $ \sqrt{s} = $ 13 TeV  JHEP 07 (2017) 121  CMSEXO16023 1703.03995 
12  CMS Collaboration  Search for a heavy composite Majorana neutrino in the final state with two leptons and two quarks at $ \sqrt{s} = $ 13 TeV  CMSEXO16026 1706.08578 

13  ATLAS Collaboration  Search for heavy neutrinos and righthanded $ \mathrm {W} $ bosons in events with two leptons and jets in pp collisions at $ \sqrt{s}= $ 7 TeV with the ATLAS detector  EPJC 72 (2012) 2056  1203.5420 
14  ATLAS Collaboration  Search for third generation scalar leptoquarks in pp collisions at $ \sqrt{s} = $ 7 TeV with the ATLAS detector  JHEP 06 (2013) 033  1303.0526 
15  ATLAS Collaboration  Search for heavy Majorana neutrinos with the ATLAS detector in pp collisions at $ \sqrt{s}= $ 8 TeV  JHEP 07 (2015) 162  1506.06020 
16  CMS Collaboration  The CMS experiment at the CERN LHC  JINST 3 (2008) S08004  CMS00001 
17  CMS Collaboration  The CMS trigger system  JINST 12 (2017) P01020  CMSTRG12001 1609.02366 
18  CMS Collaboration  Particleflow reconstruction and global event description with the CMS detector  JINST 12 (2017) P10003  CMSPRF14001 1706.04965 
19  CMS Collaboration  Performance of electron reconstruction and selection with the CMS detector in protonproton collisions at $ \sqrt{s} = $ 8 TeV  JINST 10 (2015) P06005  CMSEGM13001 1502.02701 
20  CMS Collaboration  Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s} = $ 7 TeV  JINST 7 (2012) P10002  CMSMUO10004 1206.4071 
21  M. Cacciari, G. P. Salam, and G. Soyez  The anti$ {k_{\mathrm{T}}} $ jet clustering algorithm  JHEP 04 (2008) 063  0802.1189 
22  M. Cacciari, G. P. Salam, and G. Soyez  FastJet user manual  EPJC 72 (2012) 1896  1111.6097 
23  M. Cacciari and G. P. Salam  Pileup subtraction using jet areas  PLB 659 (2008) 119  0707.1378 
24  CMS Collaboration  Jet energy scale and resolution in the CMS experiment in pp collisions at 8 TeV  JINST 12 (2017) P02014  CMSJME13004 1607.03663 
25  S. Agostinelli et al.  GEANT4a simulation toolkit  NIMA 506 (2003) 250  
26  T. Sjostrand et al.  An introduction to PYTHIA 8.2  CPC 191 (2015) 159  1410.3012 
27  R. D. Ball et al.  Parton distributions with LHC data  NPB 867 (2013) 244  1207.1303 
28  J. Alwall et al.  The automated computation of treelevel and nexttoleading order differential cross sections, and their matching to parton shower simulations  JHEP 07 (2014) 079  1405.0301 
29  NNPDF Collaboration  Parton distributions for the LHC run II  JHEP 04 (2015) 040  1410.8849 
30  P. Nason  A new method for combining NLO QCD with shower Monte Carlo algorithms  JHEP 11 (2004) 040  hepph/0409146 
31  S. Frixione, P. Nason, and C. Oleari  Matching NLO QCD computations with parton shower simulations: the POWHEG method  JHEP 11 (2007) 070  0709.2092 
32  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  1002.2581 
33  E. Re  Singletop Wtchannel production matched with parton showers using the POWHEG method  EPJC 71 (2011) 1547  1009.2450 
34  CMS Collaboration  Event generator tunes obtained from underlying event and multiparton scattering measurements  EPJC 76 (2016) 155  CMSGEN14001 1512.00815 
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  0706.2569 
36  R. Frederix and S. Frixione  Merging meets matching in MC@NLO  JHEP 12 (2012) 061  1209.6215 
37  CMS Collaboration  CMS luminosity measurements for the 2016 data taking period  CMSPASLUM17001  CMSPASLUM17001 
38  J. Butterworth et al.  PDF4LHC recommendations for LHC Run II  JPG 43 (2016) 023001  1510.03865 
39  ATLAS and CMS Collaborations  Procedure for the LHC Higgs boson search combination in summer 2011  CMSNOTE2011005 
Compact Muon Solenoid LHC, CERN 