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| CMS-PAS-TOP-22-002 | ||
| Search for flavor-changing neutral current interactions of the top quark and Higgs boson in proton-proton collisions at $ \sqrt{s} = $ 13 TeV | ||
| CMS Collaboration | ||
| 28 September 2023 | ||
| Abstract: A search for flavor-changing neutral current interactions of the top quark (t) and Higgs boson (H) is presented. The search is based on Run 2 proton-proton collisions collected in 2016--2018 at a center-of-mass energy of 13 TeV with the CMS detector at the CERN LHC and corresponding to 138 fb$ ^{-1} $. Events containing a pair of leptons with the same-sign electric charge and at least one jet are considered. Two boosted decision trees are trained to distinguish the signal from the standard model background. No significant excess above the estimated background is observed. The results are used to constrain the branching ratio ($ \mathcal{B} $) of the top quark decaying to a Higgs boson and an up (u) or charm quark (c). The observed (expected) 95% confidence level upper limits are found to be 0.072% (0.059%) for $ \mathcal{B}\left(\mathrm{t\to Hu}\right) $ and 0.043% (0.062%) for $ \mathcal{B}\left(\mathrm{t\to Hc}\right) $. A combination of searches for flavor-changing neutral current interactions of top quarks and Higgs bosons in final states with a pair of photons or a pair of bottom quarks, with data collected by the CMS experiment, is performed. The resulting observed (expected) 95% confidence level upper limits are 0.019% (0.027%) for $ \mathcal{B}\left(\mathrm{t\to Hu}\right) $ and 0.037% (0.035%) for $ \mathcal{B}\left(\mathrm{t\to Hc}\right) $. This result constitutes the best exclusion limits to date. | ||
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Links:
CDS record (PDF) ;
CADI line (restricted) ;
These preliminary results are superseded in this paper, Submitted to PRD. The superseded preliminary plots can be found here. |
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| Figures | |
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Figure 1:
Representative Feynman diagrams for the production modes considered: FCNC-associated production of a single top quark with a Higgs boson (ST, left), and $ \mathrm{t} \overline{\mathrm{t}} $ production with the FCNC decay of the top quark to a Higgs boson and an up or charm quark (TT, right). |
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Figure 1-a:
Representative Feynman diagrams for the production modes considered: FCNC-associated production of a single top quark with a Higgs boson (ST, left), and $ \mathrm{t} \overline{\mathrm{t}} $ production with the FCNC decay of the top quark to a Higgs boson and an up or charm quark (TT, right). |
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Figure 1-b:
Representative Feynman diagrams for the production modes considered: FCNC-associated production of a single top quark with a Higgs boson (ST, left), and $ \mathrm{t} \overline{\mathrm{t}} $ production with the FCNC decay of the top quark to a Higgs boson and an up or charm quark (TT, right). |
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Figure 2:
The prefit (upper) and postfit (lower) observed and expected distributions of BDT score in the signal region for Run 2 are shown. The $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ signal is shown on the left and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ is shown on the right. The uncertainty bands include the statistical and systematic uncertainties of the analysis. |
png pdf |
Figure 2-a:
The prefit (upper) and postfit (lower) observed and expected distributions of BDT score in the signal region for Run 2 are shown. The $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ signal is shown on the left and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ is shown on the right. The uncertainty bands include the statistical and systematic uncertainties of the analysis. |
png pdf |
Figure 2-b:
The prefit (upper) and postfit (lower) observed and expected distributions of BDT score in the signal region for Run 2 are shown. The $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ signal is shown on the left and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ is shown on the right. The uncertainty bands include the statistical and systematic uncertainties of the analysis. |
png pdf |
Figure 2-c:
The prefit (upper) and postfit (lower) observed and expected distributions of BDT score in the signal region for Run 2 are shown. The $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ signal is shown on the left and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ is shown on the right. The uncertainty bands include the statistical and systematic uncertainties of the analysis. |
png pdf |
Figure 2-d:
The prefit (upper) and postfit (lower) observed and expected distributions of BDT score in the signal region for Run 2 are shown. The $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ signal is shown on the left and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ is shown on the right. The uncertainty bands include the statistical and systematic uncertainties of the analysis. |
png pdf |
Figure 3:
The expected and observed limits on the anomalous coupling strength (left) and on the anomalous branching fraction (right) for Run 2 are shown. |
png pdf |
Figure 3-a:
The expected and observed limits on the anomalous coupling strength (left) and on the anomalous branching fraction (right) for Run 2 are shown. |
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Figure 3-b:
The expected and observed limits on the anomalous coupling strength (left) and on the anomalous branching fraction (right) for Run 2 are shown. |
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Figure 4:
Summary plot which shows the observed and expected results from three individual analyses and their combination. The dotted line shows the expected limit and the solid, red line shows the observed limit in all cases. The green and yellow bands show the 1 and 2 sigma ranges on the expected limits. |
| Tables | |
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Table 1:
Summary of the trigger thresholds used to select the analysis data set. The triggers require two isolated leptons, with different $ p_{\mathrm{T}} $ requirements based on the flavors of each. In the case of opposite flavor triggers, the flavor of the leading lepton is listed first. |
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Table 2:
Summary of the analysis preselection requirements. |
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Table 3:
Sources of systematic uncertainties in the yields of signal and background processes, as well as their impact on the yields in the signal regions. The impact is expressed as a one sigma range. |
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Table 4:
Observed (expected) upper limits on the $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ and $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ branching fractions for the three searches in different Higgs boson decay channels performed by the CMS Collaboration. A statistical combination of the these results is also reported. |
| Summary |
| This note presents the results of a search for flavor-changing neutral current interactions of the top quark, Higgs boson, and an up or charm quark. The search is performed in a final state with a pair of leptons of same-sign electric charge and at least one jet. Expected yields from backgrounds emerging from detector effects are estimated by extrapolating yields observed in control regions using transfer factors measured in orthogonal data samples. Expected yields from standard model processes producing a pair of prompt leptons with the same-sign electric charge are estimated from simulation. Two trained boosted decision trees are used to evaluate and classify each event. No excess above the estimated background from standard model processes is observed. The observed (expected) 95% confidence level upper limits on the branching ratio are found to be 0.072% (0.059%) for $ \mathcal{B}\left(\mathrm{t} \to \mathrm{H}\mathrm{u}\right) $ and 0.043% (0.062%) for $ \mathcal{B}\left(\mathrm{t} \to \mathrm{H}\mathrm{c}\right) $. These limits can be cast as constraints on the anomalous coupling strengths $ \kappa_{\mathrm{t}\mathrm{u}\mathrm{H}} < $ 0.071 (0.064) and $ \kappa_{\mathrm{t}\mathrm{c}\mathrm{H}} < $ 0.055 (0.065). A statistical combination of the results of this search with those of previous CMS publications searching for similar phenomena where the Higgs boson decays to a bottom quark-antiquark pair or to a pair of photons is performed. The results of this combination constrain $ \mathcal{B}\left(\mathrm{t} \to \mathrm{H}\mathrm{u}\right) < $ 0.019% (0.027%) and $ \mathcal{B}\left(\mathrm{t} \to \mathrm{H}\mathrm{c}\right) < $ 0.037% (0.035%) and represent the most stringent constraints on these interactions to date. |
| References | ||||
| 0 | S. L. Glashow, J. Iliopoulos, and L. Maiani | Weak interactions with lepton-hadron symmetry | PRD 2 (1970) 1285 | |
| 2 | M. Kobayashi and T. Maskawa | CP violation in the renormalizable theory of weak interaction | Prog. Theor. Phys. 49 (1973) 652 | |
| 3 | G. Eilam, J. L. Hewett, and A. Soni | Rare decays of the top quark in the standard and two Higgs doublet models | PRD 44 (1991) 1473 | |
| 4 | B. Mele, S. Petrarca, and A. Soddu | A new evaluation of the decay width in the standard model | PLB 435 (1998) 401 | |
| 5 | J. A. Aguilar-Saavedra | Top flavor-changing neutral interactions: theoretical expectations and experimental detection | Acta Phys. Polon. B 35 (2004) 2695 | hep-ph/0409342 |
| 6 | C. Zhang and F. Maltoni | Top-quark decay into Higgs boson and a light quark at next-to-leading order in QCD | PRD 88 (2013) 054005 | 1305.7386 |
| 7 | A. Azatov, M. Toharia, and L. Zhu | Higgs mediated flavor changing neutral currents in warped extra dimensions | PRD 80 (2009) 035016 | 0906.1990 |
| 8 | A. Azatov, G. Panico, G. Perez, and Y. Soreq | On the flavor structure of natural composite Higgs models \& top flavor violation | JHEP 12 (2014) 082 | 1408.4525 |
| 9 | S. Bejar, J. Guasch, and J. Sol \à | Loop induced flavor changing neutral decays of the top quark in a general two Higgs doublet model | NPB 600 (2001) 21 | hep-ph/0011091 |
| 10 | J. Guasch and J. Sol \à | FCNC top quark decays in the MSSM: a door to SUSY physics in high luminosity colliders? | NPB 562 (1999) 3 | |
| 11 | J. J. Cao et al. | Supersymmetry-induced flavor-changing neutral-current top-quark processes at the CERN Large Hadron Collider | PRD 75 (2007) 075021 | hep-ph/0702264 |
| 12 | J. Cao et al. | SUSY induced top quark FCNC decay $ \mathrm{t} \to \mathrm{c}\mathrm{H} $ after Run I of LHC | EPJC 74 (2014) 3058 | 1404.1241 |
| 13 | G. Eilam et al. | Top-quark rare decay $ \mathrm{t} \to \mathrm{c}\mathrm{H} $ in R-parity-violating SUSY | PLB 510 (2001) 227 | hep-ph/0102037 |
| 14 | J. A. Aguilar-Saavedra | Effects of mixing with quark singlets | PRD 67 (2003) 035003 | hep-ph/0210112 |
| 15 | W.-S. Hou | Tree level $t \to ch$ or $h \to tc$ decays | PLB 296 (1992) 179 | |
| 16 | I. Baum, G. Eilam, and S. Bar-Shalom | Scalar flavor changing neutral currents and rare top quark decays in a two H iggs doublet model 'for the top quark' | PRD 77 (2008) 113008 | 0802.2622 |
| 17 | C. Kao, H.-Y. Cheng, W.-S. Hou, and J. Sayre | Top decays with flavor changing neutral Higgs interactions at the LHC | PLB 716 (2012) 225 | 1112.1707 |
| 18 | B. Altunkaynak et al. | Flavor changing heavy Higgs interactions at the LHC | PLB 751 (2015) 135 | 1506.00651 |
| 19 | K.-F. Chen, W.-S. Hou, C. Kao, and M. Kohda | When the Higgs meets the top: Search for $ t \to ch^0 $ at the LHC | PLB 725 (2013) 378 | 1304.8037 |
| 20 | ATLAS Collaboration | Search for top quark decays $ \mathrm{t} \to \mathrm{q}\mathrm{H} $, with $ \mathrm{H} \to \gamma\gamma $, in $ \sqrt{s}= $ 13 TeV pp collisions using the ATLAS detector | JHEP 10 (2017) 129 | 1707.01404 |
| 21 | ATLAS Collaboration | Search for flavor-changing neutral currents in top quark decays $ \mathrm{t} \to \mathrm{H}\mathrm{c} $ and $ \mathrm{t} \to \mathrm{H}\mathrm{u} $ in multilepton final states in proton-proton collisions at $ \sqrt{s}= $ 13 TeV with the ATLAS detector | PRD 98 (2018) 032002 | 1805.03483 |
| 22 | ATLAS Collaboration | Search for top-quark decays $ \mathrm{t} \to \mathrm{H}\mathrm{q} $ with 36 fb$ ^{-1} $ of pp collision data at $ \sqrt{s}= $ 13 TeV with the ATLAS detector | JHEP 05 (2019) 123 | 1812.11568 |
| 23 | CMS Collaboration | Search for the flavor-changing neutral current interactions of the top quark and the Higgs boson which decays into a pair of b quarks at $ \sqrt{s}= $ 13 TeV | JHEP 06 (2018) 102 | CMS-TOP-17-003 1712.02399 |
| 24 | CMS Collaboration | Search for flavor-changing neutral current interactions of the top quark and the Higgs boson decaying to a bottom quark-antiquark pair at $ \sqrt{s} = $ 13 TeV | JHEP 02 (2022) 169 | CMS-TOP-19-002 2112.09734 |
| 25 | CMS Collaboration | Search for Flavor-Changing Neutral Current Interactions of the Top Quark and Higgs Boson in Final States with Two Photons in Proton-Proton Collisions at $ \sqrt{s} = $ 13 TeV | no.~3, 2022 PRL 129 (2022) |
|
| 26 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | |
| 27 | 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 |
| 28 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 29 | P. Nason | A new method for combining NLO QCD with shower Monte Carlo algorithms | JHEP 11 (2004) 040 | hep-ph/0409146 |
| 30 | S. Frixione, P. Nason, and C. Oleari | Matching NLO QCD computations with parton shower simulations: the POWHEG method | JHEP 11 (2007) 070 | 0709.2092 |
| 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. 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 |
| 33 | P. Nason and G. Zanderighi | $ W^+ W^- $, $ W Z $ and $ Z Z $ production in the POWHEG-BOX-V2 | EPJC 74 (2014) 2702 | 1311.1365 |
| 34 | E. Bagnaschi, G. Degrassi, P. Slavich, and A. Vicini | Higgs production via gluon fusion in the POWHEG approach in the SM and in the MSSM | JHEP 02 (2012) 088 | 1111.2854 |
| 35 | H. B. Hartanto, B. Jager, L. Reina, and D. Wackeroth | Higgs boson production in association with top quarks in the POWHEG BOX | PRD 91 (2015) 094003 | 1501.04498 |
| 36 | S. Bolognesi et al. | On the spin and parity of a single-produced resonance at the LHC | PRD 86 (2012) 095031 | 1208.4018 |
| 37 | E. Re | Single-top Wt-channel production matched with parton showers using the POWHEG method | EPJC 71 (2011) 1547 | 1009.2450 |
| 38 | NNPDF Collaboration | Parton distributions for the LHC run II | JHEP 04 (2015) 040 | 1410.8849 |
| 39 | R. D. Ball et al. | Parton distributions from high-precision collider data | EPJC 77 (2017) | |
| 40 | T. Sjöstrand et al. | An introduction to PYTHIA 8.2 | Comput. Phys. Commun. 191 (2015) 159 | 1410.3012 |
| 41 | P. Skands, S. Carrazza, and J. Rojo | Tuning PYTHIA 8.1: the Monash 2013 Tune | EPJC 74 (2014) 3024 | 1404.5630 |
| 42 | CMS Collaboration | Event generator tunes obtained from underlying event and multiparton scattering measurements | EPJC 76 (2016) 155 | CMS-GEN-14-001 1512.00815 |
| 43 | 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 |
| 44 | 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 |
| 45 | R. Frederix and S. Frixione | Merging meets matching in MC@NLO | JHEP 12 (2012) 061 | 1209.6215 |
| 46 | \GEANTfour Collaboration | GEANT 4 --- a simulation toolkit | NIM A 506 (2003) 250 | |
| 47 | M. Czakon and A. Mitov | Top$ ++ $: A program for the calculation of the top-pair cross-section at hadron colliders | Comput. Phys. Commun. 185 (2014) 2930 | |
| 48 | P. Artoisenet, R. Frederix, O. Mattelaer, and R. Rietkerk | Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations | JHEP 03 (2013) 015 | 1212.3460 |
| 49 | CMS Collaboration | Search for new physics in same-sign dilepton events in proton-proton collisions at $ \sqrt{s} = 13\,\text {TeV} $ | EPJC 76 (2016) | |
| 50 | CMS Collaboration | Search for physics beyond the standard model in events with jets and two same-sign or at least three charged leptons in proton-proton collisions at $ \sqrt{s}=13\,{\text {tev}} $ | EPJC 80 (2020) | |
| 51 | CMS Collaboration | Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton collisions at $ \sqrt{s}=13\,\text {TeV} $ | EPJC 80 (2020) | |
| 52 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 53 | CMS Collaboration | Technical proposal for the phase-II upgrade of the Compact Muon Solenoid | CMS Technical proposal CERN-LHCC-2015-010, CMS-TDR-15-02, 2015 CDS |
|
| 54 | 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 |
| 55 | CMS Collaboration | Electron and photon reconstruction and identification with the CMS experiment at the CERN LHC | JINST 16 (2021) P05014 | |
| 56 | 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 |
| 57 | M. Cacciari, G. P. Salam, and G. Soyez | The anti-$ k_{\mathrm{T}} $ jet clustering algorithm | JHEP 04 (2008) 063 | 0802.1189 |
| 58 | M. Cacciari, G. P. Salam, and G. Soyez | FastJet user manual | EPJC 72 (2012) 1896 | 1111.6097 |
| 59 | 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 |
| 60 | CMS Collaboration | Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV | JINST 13 (2018) | CMS-BTV-16-002 1712.07158 |
| 61 | E. Bols et al. | Jet flavour classification using DeepJet | JINST 15 (2020) P12012- | |
| 62 | CMS Collaboration | Performance of the DeepJet b tagging algorithm using 41.9 fb$ ^{-1} $ of data from proton-proton collisions at 13 TeV with Phase-1 CMS detector | CMS Detector Performance Note CMS-DP-2018-058, 2018 CDS |
|
| 63 | CMS Collaboration | A new calibration method for charm jet identification validated with proton-proton collision events at $ \sqrt{s} = $ 13 TeV | JINST 17 (2021) P03014 | |
| 64 | T. Chen and C. Guestrin | Xgboost: A scalable tree boosting system | in Proceedings of the 22nd ACM SIGKDD International Conference on Knowledge Discovery and Data Mining, KDD '16, New York, NY, USA (2016) link |
|
| 65 | F. Pedregosa et al. | Scikit-learn: Machine learning in Python | Journal of Machine Learning Research 12 (2011) 2825 | |
| 66 | CMS Collaboration | Precision luminosity measurement in proton-proton collisions at $ \sqrt{s} = $ 13 TeV in 2015 and 2016 at CMS | EPJC 81 (2021) 800 | CMS-LUM-17-003 2104.01927 |
| 67 | CMS Collaboration | CMS luminosity measurement for the 2017 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS Physics Analysis Summary, 2018 link |
CMS-PAS-LUM-17-004 |
| 68 | CMS Collaboration | CMS luminosity measurement for the 2018 data-taking period at $ \sqrt{s} = $ 13 TeV | CMS Physics Analysis Summary, 2019 link |
CMS-PAS-LUM-18-002 |
| 69 | S. Catani, D. de Florian, M. Grazzini, and P. Nason | Soft gluon resummation for Higgs boson production at hadron colliders | JHEP 07 (2003) 028 | hep-ph/0306211 |
| 70 | M. Cacciari et al. | The t anti-t cross-section at 1.8-TeV and 1.96-TeV: A Study of the systematics due to parton densities and scale dependence | JHEP 04 (2004) 068 | hep-ph/0303085 |
| 71 | A. Kalogeropoulos and J. Alwall | The syscalc code: A tool to derive theoretical systematic uncertainties | 1801.08401 | |
| 72 | CMS Collaboration | Measurement of the inclusive and differential wz production cross sections, polarization angles, and triple gauge couplings in pp collisions at $ \sqrt{s} = $ 13 tev | ||
| 73 | B. Biedermann, A. Denner, and M. Pellen | Complete nlo corrections to w+w+ scattering and its irreducible background at the lhc | JHEP 10 (2017) 124 | |
| 74 | LHC Higgs Cross Section Working Group | Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector | link | 1610.07922 |
| 75 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |
| 76 | T. Junk | Confidence level computation for combining searches with small statistics | NIM A 434 (1999) 435 | |
| 77 | A. L. Read | Presentation of search results: the $ \text{CL}_{s} $ technique | JPG 28 (2002) 2693 | |
| 78 | G. Cowan, K. Cranmer, E. Gross, and O. Vitells | Asymptotic formulae for likelihood-based tests of new physics | EPJC 71 (2011) | |
| 79 | Particle Data Group | Review of Particle Physics | Chin. Phys. C 40 (2016) 100001 | |
| 80 | ATLAS, CMS, LHC Higgs Combination Group | Procedure for the LHC Higgs boson search combination in Summer 2011 | technical report, CERN, Geneva, 2011 | |
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