CMS-HIG-23-002 ; ATLAS-CONF-2023-025 ; CERN-EP-2023-114 | ||
Evidence for the Higgs boson decay to a Z boson and a photon at the LHC | ||
ATLAS and CMS Collaborations | ||
7 September 2023 | ||
Phys. Rev. Lett. 132 (2024) 021803 | ||
Abstract: The first evidence for the Higgs boson decay to a Z boson and a photon is presented, with a statistical significance of 3.4 standard deviations. The result is derived from a combined analysis of the searches performed by the ATLAS and CMS Collaborations with proton--proton collision data sets collected at the CERN Large Hadron Collider (LHC) from 2015 to 2018. These correspond to integrated luminosities of around 140 fb−1 for each experiment, at a center-of-mass energy of 13 TeV. The measured signal yield is 2.2 ± 0.7 times the Standard Model prediction, and agrees with the theoretical expectation within 1.9 standard deviations. | ||
Links: e-print arXiv:2309.03501 [hep-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; Physics Briefing ; CADI line (restricted) ; |
Figures | |
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Figure 1:
Examples of Feynman diagrams for H → Zγ decay. |
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Figure 2:
The Zγ invariant mass distribution. Events from all categories in the ATLAS and CMS analyses are shown. As different ranges in mZγ are used in the two analyses, only the common subrange is visualized here. The data (points with error bars) in each category are weighted by ln(1+S/B), where S and B are the observed signal and background yields in that category, in the 120--130 GeV interval. The S and B values are derived from the fit to data. The error bars are invisible because of their small values. The fitted signal-plus-background (background) probability density functions (pdfs) in each category are also weighted in the same way and summed, and represented by a red solid (blue dashed) line. The lower panel shows the background-subtracted results with the same data and pdfs. |
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Figure 3:
The negative profile log-likelihood test statistic, where Λ represents the likelihood ratio, as a function of the signal strength μ derived from the ATLAS data (blue line), the CMS data (red line), and the combined result (black line). The different Higgs boson masses assumed by ATLAS and CMS have a negligible impact on the results. |
Summary |
In summary, a combined analysis of ATLAS and CMS searches for the Higgs boson decay to a Z boson and a photon, where the Z boson decays into an electron or muon pair, is presented. The results are based on the 13 TeV proton--proton collision data recorded by the ATLAS and CMS experiments at the CERN LHC, amounting to integrated luminosities of 139 fb−1 and 138 fb−1 respectively. Evidence for H → Zγ decay is established, with an observed significance of 3.4 standard deviations. The observed signal yield is 2.2 ± 0.7 times the Standard Model prediction. The measured H → Zγ branching fraction is ( 3.4 ± 1.1 ) × 10−3. The result agrees with the Standard Model prediction within 1.9 standard deviations. |
References | ||||
1 | ATLAS Collaboration | Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC | PLB 716 (2012) 1 | 1207.7214 |
2 | CMS Collaboration | Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC | PLB 716 (2012) 30 | CMS-HIG-12-028 1207.7235 |
3 | CMS Collaboration | Observation of a new boson with mass near 125 GeV in pp collisions at √s= 7 and 8 TeV | JHEP 06 (2013) 081 | CMS-HIG-12-036 1303.4571 |
4 | ATLAS Collaboration | The ATLAS Experiment at the CERN Large Hadron Collider | JINST 3 (2008) S08003 | |
5 | CMS Collaboration | The CMS Experiment at the CERN LHC | JINST 3 (2008) S08004 | |
6 | ATLAS and CMS Collaborations | Measurements of the Higgs boson production and decay rates and constraints on its couplings from a combined ATLAS and CMS analysis of the LHC pp collision data at √s= 7 and 8 TeV | JHEP 08 (2016) 045 | 1606.02266 |
7 | ATLAS Collaboration | A detailed map of Higgs boson interactions by the ATLAS experiment ten years after the discovery | Nature 607 (2022) 52--59 | 2207.00092 |
8 | CMS Collaboration | A portrait of the Higgs boson by the CMS experiment ten years after the discovery | Nature 607 (2022) 60--68 | CMS-HIG-22-001 2207.00043 |
9 | R. Cahn, M. Chanowitz, and N. Fleishon | Higgs particle production by Z→Hγ | PLB 82 (1979) 113 | |
10 | L. Bergstrom and G. Hulth | Induced Higgs couplings to neutral bosons in e+e− collisions | NPB 259 (1985) 137 | |
11 | M. Spira, A. Djouadi, and P. Zerwas | QCD corrections to the HZγ coupling | PLB 276 (1992) 350 | |
12 | A. Djouadi, J. Kalinowski, and M. Spira | HDECAY: A program for Higgs boson decays in the Standard Model and its supersymmetric extension | Comput. Phys. Commun. 108 (1998) 56 | hep-ph/9704448 |
13 | LHC Higgs Cross Section Working Group Collaboration | Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector | 1610.07922 | |
14 | A. Azatov, R. Contino, A. Di Iura, and J. Galloway | New Prospects for Higgs Compositeness in h→Zγ | PRD 88 (2013) 075019 | 1308.2676 |
15 | Q.-H. Cao, L.-X. Xu, B. Yan, and S.-h. Zhu | Signature of pseudo Nambu–Goldstone Higgs boson in its decay | PLB 789 (2019) 233 | 1810.07661 |
16 | I. Low, J. Lykken, and G. Shaughnessy | Singlet scalars as Higgs imposters at the Large Hadron Collider | PRD 84 (2011) 035027 | 1105.4587 |
17 | I. Low, J. Lykken, and G. Shaughnessy | Have we observed the Higgs (imposter)? | PRD 86 (2012) 093012 | 1207.1093 |
18 | M. Carena, I. Low, and C. E. Wagner | Implications of a modified Higgs to diphoton decay width | JHEP 08 (2012) 060 | 1206.1082 |
19 | C.-W. Chiang and K. Yagyu | Higgs boson decays to γγ and Zγ in models with Higgs extensions | PRD 87 (2013) 033003 | 1207.1065 |
20 | C.-S. Chen, C.-Q. Geng, D. Huang, and L.-H. Tsai | New Scalar Contributions to h → Zγ | PRD 87 (2013) 075019 | 1301.4694 |
21 | ATLAS Collaboration | A search for the Zγ decay mode of the Higgs boson in pp collisions at √s= 13 TeV with the ATLAS detector | PLB 809 (2020) 135754 | 2005.05382 |
22 | CMS Collaboration | Search for Higgs boson decays to a Z boson and a photon in proton--proton collisions at √s= 13 TeV | JHEP 05 (2022) 233 | CMS-HIG-19-014 2204.12945 |
23 | ATLAS Collaboration | Search for Higgs boson decays to a photon and a Z boson in pp collisions at √s= 7 and 8 TeV with the ATLAS detector | PLB 732 (2014) 8 | 1402.3051 |
24 | CMS Collaboration | Search for a Higgs boson decaying into a Z and a photon in pp collisions at √s= 7 and 8 TeV | PLB 726 (2013) 587 | CMS-HIG-13-006 1307.5515 |
25 | CMS Collaboration | Search for the decay of a Higgs boson in the ℓℓγ channel in proton--proton collisions at √s= 13 TeV | JHEP 11 (2018) 152 | CMS-HIG-17-007 1806.05996 |
26 | P. Nason and C. Oleari | NLO Higgs boson production via vector-boson fusion matched with shower in POWHEG | JHEP 02 (2010) 037 | 0911.5299 |
27 | 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 |
28 | P. Nason | A new method for combining NLO QCD with shower Monte Carlo algorithms | JHEP 11 (2004) 040 | hep-ph/0409146 |
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 | H. B. Hartanto, B. J ä ger, L. Reina, and D. Wackeroth | Higgs boson production in association with top quarks in the POWHEG BOX | PRD 91 (2015) 094003 | 1501.04498 |
31 | S. Alioli, P. Nason, C. Oleari, and E. Re | NLO Higgs boson production via gluon fusion matched with shower in POWHEG | JHEP 04 (2009) 002 | 0812.0578 |
32 | ATLAS Collaboration | Measurements of Higgs boson production and couplings in the four-lepton channel in pp collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector | PRD 91 (2015) 012006 | 1408.5191 |
33 | CMS Collaboration | Measurements of properties of the Higgs boson decaying into the four-lepton final state in pp collisions at √s= 13 TeV | JHEP 11 (2017) 047 | CMS-HIG-16-041 1706.09936 |
34 | M. Vesterinen | A novel technique for studying the Z boson transverse momentum distribution at hadron colliders | NIMA 602 (2009) 432 | |
35 | W. Verkerke and D. Kirkby | The RooFit toolkit for data modeling | 2003 | |
36 | L. Moneta et al. | The RooStats Project | link | 1009.1003 |
37 | K. Cranmer and G. Lewis and L. Moneta and A. Shibata and W. Verkerke | HistFactory: A tool for creating statistical models for use with RooFit and RooStats | CERN-OPEN-2012-016, 2012 | |
38 | G. Cowan, K. Cranmer, E. Gross, and O. Vitells | Asymptotic formulae for likelihood-based tests of new physics | EPJC 71 (2011) 1554 | 1007.1727 |
39 | P. Dauncey, M. Kenzie, N. Wardle, and G. Davies | Handling uncertainties in background shapes: the discrete profiling method | JINST 10 (2015) P04015 | |
40 | I. W. Stewart and F. J. Tackmann | Theory uncertainties for Higgs and other searches using jet bins | PRD 85 (2012) 034011 | 1107.2117 |
41 | S. Gangal and F. J. Tackmann | Next-to-leading-order uncertainties in Higgs+2 jets from gluon fusion | PRD 87 (2013) 093008 | 1302.5437 |
42 | M. Grazzini and H. Sargsyan | Heavy-quark mass effects in Higgs boson production at the LHC | JHEP 09 (2013) 129 | 1306.4581 |
43 | A. Martin, W. Stirling, R. Thorne, and G. Watt | Parton distributions for the LHC | JHEP 63 (2009) 189 | 0901.0002 |
44 | J. Butterworth et al. | PDF4LHC recommendations for LHC Run II | JPG 43 (2016) 023001 | 1510.03865 |
45 | ATLAS Collaboration | Luminosity determination in pp collisions at √s= 13 TeV using the ATLAS detector at the LHC | ATLAS-CONF-2019-021, 2019 | |
46 | G. Avoni et al. | The new lucid-2 detector for luminosity measurement and monitoring in atlas | JINST 13 (2018) P07017 | |
47 | CMS Collaboration | Precision luminosity measurement in proton--proton collisions at √s= 13 TeV in 2015 and 2016 at CMS | EPJC 81 (2021) 800 | CMS-LUM-17-003 2104.01927 |
48 | CMS Collaboration | CMS luminosity measurement for the 2017 data-taking period at √s= 13 TeV | CMS-PAS-LUM-17-004 | CMS-PAS-LUM-17-004 |
49 | CMS Collaboration | CMS luminosity measurement for the 2018 data-taking period at √s= 13 TeV | CMS-PAS-LUM-18-002 | CMS-PAS-LUM-18-002 |
50 | ATLAS and CMS Collaborations | Combined Measurement of the Higgs Boson Mass in pp Collisions at √s= 7 and 8 TeV with the ATLAS and CMS Experiments | PRL 114 (2015) 191803 | 1503.07589 |
51 | CMS Collaboration | A measurement of the Higgs boson mass in the diphoton decay channel | PLB 805 (2020) 135425 | CMS-HIG-19-004 2002.06398 |
52 | S. Baker and R. D. Cousins | Clarification of the use of chi square and likelihood functions in fits to histograms | NIM 221 (1984) 437 | |
53 | CMS Collaboration | HEPData record for this analysis | link |
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Compact Muon Solenoid LHC, CERN |
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