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CMS-EXO-17-008 ; CERN-EP-2018-202
Search for a W' boson decaying to a $\tau$ lepton and a neutrino in proton-proton collisions at $\sqrt{s} = $ 13 TeV
Phys. Lett. B 792 (2019) 107
Abstract: A search for a new high-mass resonance decaying to a tau lepton and a neutrino is reported. The analysis uses proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} = $ 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The search utilizes hadronically decaying tau leptons. No excess in the event yield is observed at high transverse masses of the $\tau$ and missing transverse momentum. An interpretation of results within the sequential standard model excludes W' boson masses below 4.0 TeV at 95% confidence level. Existing limits are also improved on models in which the W' boson decays preferentially to fermions of the third generation. Heavy W' bosons with masses less than 1.7-3.9 TeV, depending on the coupling in the non-universal G(221) model, are excluded at 95% confidence level. These are the most stringent limits on this model to date.
Figures & Tables Summary References CMS Publications
Figures

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Figure 1:
Leading order Feynman diagram of the expected signal process $ {\mathrm {W}'} \to {\tau} {\nu}$.

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Figure 2:
Branching fractions $\mathcal {B}({\mathrm {W}'})$ as a function of the mixing angle $\cot\theta _{\mathrm {E}}$, for W' boson decays in the NUGIM G(221) framework, as calculated in Refs. [2,21,22]. For $\cot\theta _{\mathrm {E}} = $ 1 the values correspond to those in the SSM, rescaled to accommodate the WH decay channel.

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Figure 3:
(Left) The $ {m_{\mathrm {T}}} $ distribution after the final selection. The black symbols with error bars show data, while the filled histograms represent the SM backgrounds. Signal examples for SSM W' bosons with masses of 0.6, 1.0, 4.0, and 5.0 TeV are shown with the open histograms. (Right) The integral transverse mass distribution, where the value in each bin is equal to the number of events with transverse mass equal to or greater than the left of the bin. The lower panels show the ratio of data to prediction, and the gray band represents the systematic uncertainties.

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Figure 3-a:
The $ {m_{\mathrm {T}}} $ distribution after the final selection. The black symbols with error bars show data, while the filled histograms represent the SM backgrounds. Signal examples for SSM W' bosons with masses of 0.6, 1.0, 4.0, and 5.0 TeV are shown with the open histograms. The lower panel shows the ratio of data to prediction, and the gray band represents the systematic uncertainties.

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Figure 3-b:
The integral transverse mass distribution, where the value in each bin is equal to the number of events with transverse mass equal to or greater than the left of the bin. The lower panel shows the ratio of data to prediction, and the gray band represents the systematic uncertainties.

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Figure 4:
Distribution of $ {p_{\mathrm {T}}} ^{{\tau}}$ in the control region. The black symbols with error bars show the data, while the histograms represent the SM backgrounds. The lower panel shows the ratio of data to prediction.

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Figure 5:
Expected (black dashed line) and observed (black solid line) 95% CL upper limits on the cross section for the production of SSM W' boson. The shaded bands around the expected limit represent the one and two standard deviation (s.d.) uncertainty intervals. The NNLO theoretical cross section with the corresponding PDF uncertainty band is also shown.

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Figure 6:
Expected (black dashed line) and observed (black solid line) 95% CL upper limits on the ratio of couplings as a function of the W' boson mass. The values above the observed limit contour are excluded. The shaded bands around the expected limit represent the one and two standard deviation (s.d.) uncertainty intervals.

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Figure 7:
Left: The width of the W' boson as a function of $M_{{\mathrm {W}'}}$ and mixing angle $\cot\theta _{\mathrm {E}}$ in the NUGIM G(221) framework. Right: Expected (black dashed line) and observed (black solid line) 95% CL upper limits on the mixing angle $\cot\theta _{\mathrm {E}}$ as a function of the W' boson mass. The region left of the solid line is excluded. The shaded bands represent the one and two standard deviation (s.d.) uncertainty bands.

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Figure 7-a:
The width of the W' boson as a function of $M_{{\mathrm {W}'}}$ and mixing angle $\cot\theta _{\mathrm {E}}$ in the NUGIM G(221) framework.

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Figure 7-b:
Expected (black dashed line) and observed (black solid line) 95% CL upper limits on the mixing angle $\cot\theta _{\mathrm {E}}$ as a function of the W' boson mass. The region left of the solid line is excluded. The shaded bands represent the one and two standard deviation (s.d.) uncertainty bands.

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Figure 8:
Expected (black dashed line) and observed (black solid line) 95% CL model-independent upper limits on the product of cross section, branching fraction, and acceptance for a resonance decaying into the $ {\tau} {\nu}$ channel. The shaded bands represent the one and two standard deviation (s.d.) uncertainty bands.
Tables

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Table 1:
Expected yields for the signal and background events compared to the measured event yields in data, for three regions of ${m_{\mathrm {T}}}$. Also shown are the total systematic uncertainties in the estimate of the event numbers.
Summary
A search for new physics in final states with a hadronically decaying $\tau$ lepton and missing transverse momentum has been performed by the CMS experiment, using proton-proton collision data at the center-of-mass energy $\sqrt{s} = $ 13 TeV with an integrated luminosity of 35.9 fb$^{-1}$. No significant excess compared to the standard model expectation is observed in the transverse mass of the tau and missing transverse momentum. A sequential standard model W' boson is excluded in the mass range 0.4 $ < M_{\mathrm{W'}} < $ 4.0 TeV at 95% confidence level. Couplings that are weaker than assumed in the sequential standard model can be excluded down to values of $ 7 \times 10^{-2} $ for $M_{\mathrm{W'}} = $ 1 TeV. Within the nonuniversal gauge interaction SU(2)xSU(2)xU(1) model, the lower limit on the W' boson mass depends on the coupling constant and varies from 1.7 to 3.9 TeV at 95% confidence level. For $\cot\theta_{\mathrm{E}} > $ 1, these results obtained in the tau channel provide the most stringent constraints on this model to date. In addition, a model-independent limit is provided allowing the results to be interpreted in other models giving the same final state with similar kinematic distributions.
References
1 G. Altarelli, B. Mele, and M. Ruiz-Altaba Searching for new heavy vector bosons in $ {\mathrm{p}}\mathrm{\bar{p}} $ colliders Z. Phys. C 45 (1989) 109, .[Erratum: \DOI10.1007/BF01556677]
2 C.-W. Chiang, N. G. Deshpande, X.-G. He, and J. Jiang The family $ SU(2)_l \times SU(2)_h \times U(1) $ model PRD 81 (2010) 015006 0911.1480
3 X. Li and E. Ma Gauge model of generation nonuniversality PRL 47 (1981) 1788
4 D. J. Muller and S. Nandi Top flavor: a separate $ SU(2) $ for the third family PLB 383 (1996) 345 hep-ph/9602390
5 E. Malkawi, T. M. P. Tait, and C. P. Yuan A model of strong flavor dynamics for the top quark PLB 385 (1996) 304 hep-ph/9603349
6 K. Hsieh, K. Schmitz, J.-H. Yu, and C. P. Yuan Global analysis of general $ SU(2) \times SU(2) \times U(1) $ models with precision data PRD 82 (2010) 035011 1003.3482
7 CMS Collaboration Search for $ \mathrm{W'} $ decaying to tau lepton and neutrino in proton-proton collisions at $ \sqrt{s} = $ 8 TeV PLB 755 (2016) 196 CMS-EXO-12-011
1508.04308
8 ATLAS Collaboration Search for high-mass resonances decaying to $ \tau\nu $ in pp collisions at $ \sqrt{s} = $ 13 TeV with the ATLAS detector PRL 120 (2018) 161802 1801.06992
9 CMS Collaboration Search for high-mass resonances in final states with a lepton and missing transverse momentum at $ \sqrt{s} = $ 13 TeV JHEP 06 (2018) 128 CMS-EXO-16-033
1803.11133
10 CMS Collaboration Search for a heavy resonance decaying into a $ \mathrm{Z} $ boson and a vector boson in the $ \nu \bar{\nu} \mathrm{\mathrm{q}} \mathrm{\mathrm{\bar{q}}} $ final state JHEP 07 (2018) 075 CMS-B2G-17-005
1803.03838
11 CMS Collaboration Search for dijet resonances in proton-proton collisions at $ \sqrt{s} = $ 13 TeV and constraints on dark matter and other models PLB 769 (2017) 520 CMS-EXO-16-032
1611.03568
12 CMS Collaboration Search for heavy resonances decaying to a top quark and a bottom quark in the lepton+jets final state in proton-proton collisions at 13 TeV PLB 777 (2018) 39 CMS-B2G-17-010
1708.08539
13 E. Boos, V. Bunichev, L. Dudko, and M. Perfilov Interference between $ \mathrm{W'} $ and $ \mathrm{W} $ in single-top quark production processes PLB 655 (2007) 245 hep-ph/0610080
14 T. Sjostrand et al. An introduction to PYTHIA 8.2 Comp. Phys. Comm. 191 (2015) 159 1410.3012
15 R. D. Ball et al. Impact of heavy quark masses on parton distributions and LHC phenomenology NPB 849 (2011) 296 1101.1300
16 R. D. Ball et al. Parton distributions with LHC data NPB 867 (2013) 244 1207.1303
17 P. Skands, S. Carrazza, and J. Rojo Tuning PYTHIA 8.1: the Monash 2013 tune EPJC 74 (2014) 3024 1404.5630
18 R. Gavin, Y. Li, F. Petriello, and S. Quackenbush $ \mathrm{W} $ physics at the LHC with FEWZ 2.1 CPC 184 (2013) 208 1201.5896
19 Y. Li and F. Petriello Combining QCD and electroweak corrections to dilepton production in FEWZ PRD 86 (2012) 094034 1208.5967
20 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
21 Y. G. Kim and K. Y. Lee Early LHC bound on the $ \mathrm{W'} $ boson mass in the nonuniversal gauge interaction model PLB 706 (2012) 367 1105.2653
22 L. Edelhauser and A. Knochel Observing nonstandard $ \mathrm{W'} $ and $ \mathrm{Z'} $ through the third generation and Higgs lens 1408.0914
23 CMS Collaboration The CMS trigger system JINST 12 (2017) P01020 CMS-TRG-12-001
1609.02366
24 CMS Collaboration The CMS experiment at the CERN LHC JINST 3 (2008) S08004 CMS-00-001
25 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
26 NNPDF Collaboration Parton distributions for the LHC Run II JHEP 04 (2015) 040 1410.8849
27 S. G. Bondarenko and A. A. Sapronov NLO EW and QCD proton-proton cross section calculations with MCSANC-v1.01 CPC 184 (2013) 2343 1301.3687
28 J. R. Andersen et al. Les Houches 2013: Physics at TeV colliders: Standard model working group report 1405.1067
29 S. Frixione, P. Nason, and C. Oleari Matching NLO QCD computations with parton shower simulations: the POWHEG method JHEP 11 (2007) 070 0709.2092
30 P. Nason A new method for combining NLO QCD with shower Monte Carlo algorithms JHEP 11 (2004) 040 hep-ph/0409146
31 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
32 S. Alioli, P. Nason, C. Oleari, and E. Re NLO single-top production matched with shower in POWHEG: $ s $- and $ t $-channel contributions JHEP 09 (2009) 111 0907.4076
33 E. Re Single-top Wt-channel production matched with parton showers using the POWHEG method EPJC 71 (2011) 1547 1009.2450
34 S. Frixione, P. Nason, and G. Ridolfi A positive-weight next-to-leading-order Monte Carlo for heavy flavour hadroproduction JHEP 09 (2007) 126 0707.3088
35 GEANT4 Collaboration GEANT4--a simulation toolkit NIMA 506 (2003) 250
36 CMS Collaboration Particle-flow reconstruction and global event description with the CMS detector JINST 12 (2017) P10003 CMS-PRF-14-001
1706.04965
37 CMS Collaboration Performance of the CMS missing transverse momentum reconstruction in $ {\mathrm{p}}{\mathrm{p}} $ data at $ \sqrt{s} = $ 8 TeV JINST 10 (2015) P02006 CMS-JME-13-003
1411.0511
38 M. Cacciari, G. P. Salam, and G. Soyez The anti-$ {k_{\mathrm{T}}} $ jet clustering algorithm JHEP 04 (2008) 063 0802.1189
39 M. Cacciari, G. P. Salam, and G. Soyez FastJet user manual EPJC 72 (2012) 1896 1111.6097
40 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
41 CMS Collaboration Electron and photon performance in CMS with the full 2016 data sample CDS
42 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
43 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
44 CMS Collaboration Performance of reconstruction and identification of $ \tau $ leptons in their decays to hadrons and $ \nu_{\tau} $ in LHC Run II CMS-PAS-TAU-16-002 CMS-PAS-TAU-16-002
45 CMS Collaboration Observation of the Higgs boson decay to a pair of $ \tau $ leptons with the CMS detector PLB 779 (2018) 283 CMS-HIG-16-043
1708.00373
46 CMS Collaboration Search for dark matter produced with an energetic jet or a hadronically decaying $ \mathrm{W} $ or $ \mathrm{Z} $ boson at $ \sqrt{s} = $ 13 TeV JHEP 07 (2017) 014 CMS-EXO-16-037
1703.01651
47 CMS Collaboration Performance of missing energy reconstruction in 13 TeV pp collision data using the CMS detector CMS-PAS-JME-16-004 CMS-PAS-JME-16-004
48 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
49 M. Botje et al. The PDF4LHC working group interim recommendations 1101.0538
50 S. Alekhin et al. The PDF4LHC working group interim report 1101.0536
51 J. Butterworth et al. PDF4LHC recommendations for LHC Run II JPG 43 (2016) 023001 1510.03865
52 CMS Collaboration Measurement of the inelastic proton-proton cross section at $ \sqrt{s} = $ 13 TeV Submitted to \it JHEP CMS-FSQ-15-005
1802.02613
53 CMS Collaboration CMS luminosity measurement for the 2016 data taking period CMS-PAS-LUM-17-001 CMS-PAS-LUM-17-001
54 G. Cowan ``Statistics", Ch. 39 in Particle Data Group, C. Patrignani et al., ``Review of particle physics" CPC 40 (2016) 100001
55 M. Baak, S. Gadatsch, R. Harrington, and W. Verkerke Interpolation between multi-dimensional histograms using a new non-linear moment morphing method NIMA 771 (2015) 39 1410.7388
56 ATLAS Collaboration Search for a new heavy gauge boson resonance decaying into a lepton and missing transverse momentum in 36 fb$^{-1}$ of pp collisions at $ \sqrt{s} = $ 13 TeV with the ATLAS experiment EPJC 78 (2018) 401 1706.04786
Compact Muon Solenoid
LHC, CERN