CMS-PAS-HIG-18-016

CMS-PAS-HIG-18-016
Observation of Higgs boson decay to bottom quarks
CMS Collaboration
August 2018

Abstract: A search for the standard model Higgs boson decaying to a pair of bottom quarks is presented. Higgs bosons produced in association with a W or Z boson are searched for in final states including 0, 1, or 2 charged leptons and two identified b jets. The search is performed at the LHC in a data sample recorded by the CMS experiment in 2017 corresponding to 41.3 fb$^{-1}$ of pp collisions at $\sqrt{s}= $ 13 TeV. An excess of events is observed with a significance of 3.3 standard deviations, corresponding to a measured signal strength of 1.08 $\pm$ 0.34 times the standard model expectation. When combined with previous results using this production channel and data collected at 7, 8, and 13 TeV, the observed significance increases to 4.8 standard deviations and the measured signal strength is 1.01 $\pm$ 0.22. A combination of all CMS searches for $\mathrm{H}\to\mathrm{b}\bar{\mathrm{b}}$, including the four dominant production processes at the LHC, yields an observed (expected) significance of 5.6 (5.5) standard deviations and a signal strength of 1.04 $\pm$ 0.20.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PRL 121 (2018) 121801. The superseded preliminary plots can be found here.

Figures & Tables	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Left: distribution of events in the signal region for each channel sorted into bins of similar expected signal-to-background ratio, as given by the value of their corresponding discriminant. Data from Run 2 are combined into a single distribution. The bottom panel shows the ratio of the data to the background-only prediction, with the total uncertainty on the background yield indicated by the grey hatch. Right: weighted dijet invariant mass distribution for events in all channels combined in the Run 2 data. Shown are data and the VH and VZ processes with all other background processes subtracted. Weights are derived from a fit to the $m_{\rm jj}$ distribution as described in the text.
png pdf	Figure 1-a: Distribution of events in the signal region for each channel sorted into bins of similar expected signal-to-background ratio, as given by the value of their corresponding discriminant. Data from Run 2 are combined into a single distribution. The bottom panel shows the ratio of the data to the background-only prediction, with the total uncertainty on the background yield indicated by the grey hatch.
png pdf	Figure 1-b: Weighted dijet invariant mass distribution for events in all channels combined in the Run 2 data. Shown are data and the VH and VZ processes with all other background processes subtracted. Weights are derived from a fit to the $m_{\rm jj}$ distribution as described in the text.
png pdf	Figure 2: Left: best-fit value of the signal strength $\mu $, at $ {m_ {\mathrm {H}}} = $ 125.09 GeV, for the fit of all ${{\mathrm {H}} \to {{\mathrm {b}} {\overline {\mathrm {b}}}}} $ channels in Run 1 and Run 2, shown as a vertical black line with a blue uncertainty band. Also shown are the individual results of the 2016 and 2017 analyses, the Run 2 combination, and the Run 1 analysis. Right: best-fit signal strengths for the different production mechanisms, as measured in events where the Higgs boson decays to bottom quarks. Error bars indicate the 1$\sigma $ statistical (thick red), 1$\sigma $ total (thick blue), and 2$\sigma $ total (thin blue) uncertainty intervals.
png pdf	Figure 2-a: Best-fit value of the signal strength $\mu $, at $ {m_ {\mathrm {H}}} = $ 125.09 GeV, for the fit of all ${{\mathrm {H}} \to {{\mathrm {b}} {\overline {\mathrm {b}}}}} $ channels in Run 1 and Run 2, shown as a vertical black line with a blue uncertainty band. Also shown are the individual results of the 2016 and 2017 analyses, the Run 2 combination, and the Run 1 analysis.
png pdf	Figure 2-b: Best-fit signal strengths for the different production mechanisms, as measured in events where the Higgs boson decays to bottom quarks. Error bars indicate the 1$\sigma $ statistical (thick red), 1$\sigma $ total (thick blue), and 2$\sigma $ total (thin blue) uncertainty intervals.

Tables
png pdf	Table 1: The contributions of the main uncertainty sources to the measurement of $\mu $ in the 2017 data. The total uncertainty is decomposed into four components: theory, size of simulated samples, experimental, and statistical. Detailed decompositions into specific sources are included for the experimental, statistical, and theory components. Due to correlations in the combined fit between nuisance parameters in different sources, the sum in quadrature for each source does not in general equal the total uncertainty of each component.
png pdf	Table 2: Expected and observed significances, in number of standard deviations, and observed signal strengths for the VH production process with ${{\mathrm {H}} \to {{\mathrm {b}} {\overline {\mathrm {b}}}}}$. Results are shown separately for 2017 data, combined Run 2 (2016 and 2017 data), and for the combination of the Run 1 and Run 2 data. For the 2017 analysis, results are shown separately for the individual $\mu $ value for each channel from a combined simultaneous fit to all channels. All results are obtained for $ {m_ {\mathrm {H}}} = $ 125.09 GeV.

Summary

A combination of all CMS search results for the $\mathrm{H}\to\mathrm{b}\bar{\mathrm{b}}$ decay is performed, including all four primary production processes at the LHC: VH (reported above), gluon fusion [40], vector boson fusion [46], and associated production with top quarks [30,43,44]. The observed signal significance is 5.6 standard deviations, where 5.5 are expected, and the measured signal strength is $\mu= $ 1.04$^{+0.20}_{-0.19}$, which is compatible with the expected rate for the SM Higgs boson. Figure 2 summarizes the signal strengths for the various production mechanisms measured in $\mathrm{H}\to\mathrm{b}\bar{\mathrm{b}}$ events, and the combined $\mathrm{H}\to\mathrm{b}\bar{\mathrm{b}}$ result. This result represents the first observation of $\mathrm{H}\to\mathrm{b}\bar{\mathrm{b}}$ decay by the CMS experiment.

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 $ \sqrt{s} = $ 7 and 8 TeV	JHEP 06 (2013) 081	CMS-HIG-12-036 1303.4571
4	F. Englert and R. Brout	Broken symmetry and the mass of gauge vector mesons	PRL 13 (1964) 321
5	P. W. Higgs	Broken symmetries, massless particles and gauge fields	PL12 (1964) 132
6	P. W. Higgs	Broken symmetries and the masses of gauge bosons	PRL 13 (1964) 508
7	G. S. Guralnik, C. R. Hagen, and T. W. B. Kibble	Global conservation laws and massless particles	PRL 13 (1964) 585
8	P. W. Higgs	Spontaneous symmetry breakdown without massless bosons	PR145 (1966) 1156
9	T. W. B. Kibble	Symmetry breaking in non-Abelian gauge theories	PR155 (1967) 1554
10	ATLAS Collaboration	Measurement of Higgs boson production in the diphoton decay channel in pp collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector	PRD 90 (2014) 112015	1408.7084
11	CMS Collaboration	Observation of the diphoton decay of the Higgs boson and measurement of its properties	EPJC 74 (2014) 3076	CMS-HIG-13-001 1407.0558
12	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
13	CMS Collaboration	Measurement of the properties of a Higgs boson in the four-lepton final state	PRD 89 (2014) 092007	CMS-HIG-13-002 1312.5353
14	ATLAS Collaboration	Observation and measurement of Higgs boson decays to WW$ ^* $ with the ATLAS detector	PRD 92 (2015) 012006	1412.2641
15	ATLAS Collaboration	Study of (W/Z)H production and Higgs boson couplings using H $ \rightarrow $ WW$ ^{\ast} $ decays with the ATLAS detector	JHEP 08 (2015) 137	1506.06641
16	CMS Collaboration	Measurement of Higgs boson production and properties in the WW decay channel with leptonic final states	JHEP 01 (2014) 096	CMS-HIG-13-023 1312.1129
17	ATLAS Collaboration	Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector	JHEP 04 (2015) 117	1501.04943
18	CMS Collaboration	Evidence for the 125 GeV Higgs boson decaying to a pair of $ \tau $ leptons	JHEP 05 (2014) 104	CMS-HIG-13-004 1401.5041
19	CMS Collaboration	Observation of Higgs boson decays to a pair of tau leptons	PLB 779 (2017) 283	CMS-HIG-16-043 1708.00373
20	CMS Collaboration	Measurements of properties of the Higgs boson decaying to a W boson pair in pp collisions at $ \sqrt{s}= $ 13 TeV	Submitted to: PL(2018)	CMS-HIG-16-042 1806.05246
21	ATLAS Collaboration	Measurements of the Higgs boson production and decay rates and coupling strengths using pp collision data at $ \sqrt{s}= $ 7 and 8 TeV in the ATLAS experiment	EPJC 76 (2016) 6	1507.04548
22	CMS Collaboration	Precise determination of the mass of the Higgs boson and tests of compatibility of its couplings with the standard model predictions using proton collisions at 7 and 8 TeV	EPJC 75 (2015) 212	CMS-HIG-14-009 1412.8662
23	CMS Collaboration	Study of the mass and spin-parity of the Higgs boson candidate via its decays to Z boson pairs	PRL 110 (2013) 081803	CMS-HIG-12-041 1212.6639
24	ATLAS Collaboration	Evidence for the spin-0 nature of the Higgs boson using ATLAS data	PLB 726 (2013) 120	1307.1432
25	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 $ \sqrt{s}= $ 7 and 8 TeV	JHEP 08 (2016) 045	1606.02266
26	ATLAS and CMS Collaborations	Combined measurement of the Higgs boson mass in pp collisions at $ \sqrt{s}= $ 7 and 8 TeV with the ATLAS and CMS experiments	PRL 114 (2015) 191803	1503.07589
27	CMS Collaboration	Measurements of properties of the Higgs boson decaying into the four-lepton final state in pp collisions at $ \sqrt{s} = $ 13 TeV	JHEP 11 (2017) 47	CMS-HIG-16-041 1706.09936
28	ATLAS Collaboration	Combined measurement of differential and total cross sections in the $ H \rightarrow \gamma \gamma $ and the $ H \rightarrow ZZ^* \rightarrow 4\ell $ decay channels at $ \sqrt{s} = $ 13 TeV with the ATLAS detector	Submitted to PLB	1805.10197
29	ATLAS Collaboration	Measurement of the Higgs boson mass in the $ H\rightarrow ZZ^* \rightarrow 4\ell $ and $ H \rightarrow \gamma\gamma $ channels with $ \sqrt{s}=13 TeV pp $ collisions using the ATLAS detector	Submitted to PLB	1806.00242
30	CMS Collaboration	Observation of $ \mathrm{t\overline{t}} $H production	PRL 120 (2018) 231801	CMS-HIG-17-035 1804.02610
31	ATLAS Collaboration	Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector	, Submitted to PLB	1806.00425
32	S. Heinmeyer et al.	Handbook of LHC Higgs Cross Sections: 3. Higgs Properties	CERN-2013-004	1307.1347
33	S. Weinberg	A model of leptons	PRL 19 (1967) 1264
34	Y. Nambu and G. Jona-Lasinio	Dynamical model of elementary particles based on an analogy with superconductivity. I	PR122 (1961) 345
35	ATLAS Collaboration	Evidence for the $ \mathrm{H}\rightarrow\mathrm{b\bar{b}} $ decay with the ATLAS detector	JHEP 12 (2017) 24	1708.03299
36	CMS Collaboration	Evidence for the Higgs boson decay to a bottom quark-antiquark pair	PLB 780 (2018) 501	CMS-HIG-16-044 1709.07497
37	ATLAS Collaboration	Search for the $ \mathrm{b}\overline{\mathrm{b}} $ decay of the Standard Model Higgs boson in associated (W/Z)H production with the ATLAS detector	JHEP 01 (2015) 069	1409.6212
38	CMS Collaboration	Search for the standard model Higgs boson produced in association with a W or a Z boson and decaying to bottom quarks	PRD 89 (2014) 012003	CMS-HIG-13-012 1310.3687
39	CDF and D0 Collaborations	Evidence for a particle produced in association with weak bosons and decaying to a bottom-antibottom quark pair in Higgs boson searches at the Tevatron	PRL 109 (2012) 071804	1207.6436
40	CMS Collaboration	Inclusive search for a highly boosted Higgs boson decaying to a bottom quark-antiquark pair	PRL 120 (2018) 071802	CMS-HIG-17-010 1709.05543
41	ATLAS Collaboration	Search for the Standard Model Higgs boson produced in association with top quarks and decaying into $ \mathrm{b}\overline{\mathrm{b}} $ in pp collisions at $ \sqrt{s} = $ 8 TeV with the ATLAS detector	EPJC 75 (2015) 349	1503.05066
42	ATLAS Collaboration	Search for the Standard Model Higgs boson decaying into $ \mathrm{b}\overline{\mathrm{b}} $ produced in association with top quarks decaying hadronically in pp collisions at $ \sqrt{s}= $ 8 TeV with the ATLAS detector	JHEP 05 (2016) 160	1604.03812
43	CMS Collaboration	Search for the standard model Higgs boson produced in association with a top-quark pair in pp collisions at the LHC	JHEP 05 (2013) 145	CMS-HIG-12-035 1303.0763
44	CMS Collaboration	Search for the associated production of the Higgs boson with a top-quark pair	JHEP 09 (2014) 087	CMS-HIG-13-029 1408.1682
45	ATLAS Collaboration	Search for the Standard Model Higgs boson produced by vector-boson fusion and decaying to bottom quarks in $ \sqrt{s}= $ 8 TeV pp collisions with the ATLAS detector	JHEP 11 (2016) 112	1606.02181
46	CMS Collaboration	Search for the standard model Higgs boson produced through vector boson fusion and decaying to $ \mathrm{b}\overline{\mathrm{b}} $	PRD 92 (2015) 032008	CMS-HIG-14-004 1506.01010
47	CMS Collaboration	The CMS experiment at the CERN LHC	JINST 3 (2008) S08004	CMS-00-001
48	CMS Collaboration	Particle-flow reconstruction and global event description with the cms detector	JINST 12 (2017) P10003	CMS-PRF-14-001 1706.04965
49	M. Cacciari, G. P. Salam, and G. Soyez	The anti-$ k_{t} $ jet clustering algorithm	JHEP 04 (2008) 063	0802.1189
50	M. Cacciari, G. P. Salam, and G. Soyez	FastJet User Manual	EPJC 72 (2012) 1896	1111.6097
51	M. Cacciari and G. P. Salam	Dispelling the $ N^{3} $ myth for the $ k_t $ jet-finder	PLB 641 (2006) 57	hep-ph/0512210
52	M. Cacciari and G. P. Salam	Pileup subtraction using jet areas	PLB 659 (2008) 119	0707.1378
53	GEANT4 Collaboration	GEANT4 --- a simulation toolkit	NIMA 506 (2003) 250
54	P. Nason	A new method for combining NLO QCD with shower Monte Carlo algorithms	JHEP 11 (2004) 040	hep-ph/0409146
55	S. Frixione, P. Nason, and C. Oleari	Matching NLO QCD computations with parton shower simulations: the POWHEG method	JHEP 11 (2007) 070	0709.2092
56	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
57	K. Hamilton, P. Nason, and G. Zanderighi	MINLO: Multi-Scale Improved NLO	JHEP 10 (2012) 155	1206.3572
58	G. Luisoni, P. Nason, C. Oleari, and F. Tramontano	HW$ ^{\pm} $/HZ + 0 and 1 jet at NLO with the POWHEG BOX interfaced to GoSam and their merging within MiNLO	JHEP 10 (2013) 083	1306.2542
59	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
60	R. Frederix and S. Frixione	Merging meets matching in MC@NLO	JHEP 12 (2012) 061	1209.6215
61	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
62	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
63	R. Frederix, E. Re, and P. Torrielli	Single-top $ t $-channel hadroproduction in the four-flavour scheme with POWHEG and aMC@NLO	JHEP 09 (2012) 130	1207.5391
64	E. Re	Single-top Wt-channel production matched with parton showers using the POWHEG method	EPJC 71 (2011) 1547	1009.2450
65	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
66	NNPDF Collaboration	Parton distributions from high-precision collider data	EPJC 77 (2017) 663	1706.00428
67	T. Sjostrand et al.	An Introduction to PYTHIA 8.2	CPC 191 (2015) 159--177	1410.3012
68	CMS Collaboration	Event generator tunes obtained from underlying event and multiparton scattering measurements	EPJC 76 (2016) 155	CMS-GEN-14-001 1512.00815
69	P. Skands, S. Carrazza, and J. Rojo	Tuning PYTHIA 8.1: the Monash 2013 tune	EPJC 74 (2014) 3024	1404.5630
70	G. Ferrera, M. Grazzini, and F. Tramontano	Higher-order QCD effects for associated WH production and decay at the LHC	JHEP 04 (2014) 039	1312.1669
71	G. Ferrera, M. Grazzini, and F. Tramontano	Associated ZH production at hadron colliders: the fully differential NNLO QCD calculation	PLB 740 (2015) 51	1407.4747
72	G. Ferrera, M. Grazzini, and F. Tramontano	Associated WH production at hadron colliders: a fully exclusive QCD calculation at NNLO	PRL 107 (2011) 152003	1107.1164
73	G. Ferrera, G. Somogyi, and F. Tramontano	Associated production of a Higgs boson decaying into bottom quarks at the LHC in full NNLO QCD	PLB 780 (2018) 346--351	1705.10304
74	O. Brein, R. V. Harlander, and T. J. E. Zirke	vh@nnlo --- Higgs Strahlung at hadron colliders	CPC 184 (2013) 998	1210.5347
75	R. V. Harlander, S. Liebler, and T. Zirke	Higgs Strahlung at the Large Hadron Collider in the 2-Higgs-Doublet Model	JHEP 02 (2014) 023	1307.8122
76	A. Denner, S. Dittmaier, S. Kallweit, and A. Muck	HAWK 2.0: A Monte Carlo program for Higgs production in vector-boson fusion and Higgs strahlung at hadron colliders	CPC 195 (2015) 161	1412.5390
77	LHC Higgs Cross Section Working Group	Handbook of LHC Higgs Cross Sections: 4. Deciphering the Nature of the Higgs Sector		1610.07922
78	M. Czakon and A. Mitov	Top++: A Program for the Calculation of the Top-Pair Cross-Section at Hadron Colliders	CPC 185 (2014) 2930	1112.5675
79	Y. Li and F. Petriello	Combining QCD and electroweak corrections to dilepton production in FEWZ	PRD 86 (2012) 094034	1208.5967
80	S. Kallweit et al.	NLO QCD+EW predictions for V+jets including off-shell vector-boson decays and multijet merging	JHEP 04 (2016) 021	1511.08692
81	CMS Collaboration	Measurement of differential cross sections for top quark pair production using the $ \text{lepton}{+}\text{jets} $ final state in proton-proton collisions at 13 TeV	PRD 95 (2017) 092001	CMS-TOP-16-008 1610.04191
82	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
83	J. M. Butterworth, A. R. Davison, M. Rubin, and G. P. Salam	Jet substructure as a new Higgs search channel at the LHC	PRL 100 (2008) 242001	0802.2470
84	T. Junk	Confidence level computation for combining searches with small statistics	NIMA 434 (1999) 435	hep-ex/9902006
85	A. L. Read	Presentation of search results: The CLs technique	JPG 28 (2002) 2693
86	ATLAS and CMS Collaborations, LHC Higgs Combination Group	Procedure for the LHC Higgs boson search combination in Summer 2011	ATL-PHYS-PUB 011-11/CMS NOTE 2011-005
87	G. Cowan, K. Cranmer, E. Gross, and O. Vitells	Asymptotic formulae for likelihood-based tests of new physics	EPJC 71 (2011) 1554	1007.1727