Search for the Higgs Boson Decaying to W+W− in the Fully Leptonic Final State
This is a condensed description with plots for the analysis
CMS-HIG-11-024
Abstract
We report a search for the Higgs boson decaying to W
+W
− in pp collisions at sqrt(s) = 7 TeV. The data were collected at the LHC with the CMS detector, and correspond to an integrated luminosity of 4.6 fb
−1.
W
+W
− candidates are selected in events with two leptons (electrons or muons). No significant excess above Standard Model back- ground expectations is observed, and upper limits on the Higgs boson production are derived.
The presence of a Standard Model Higgs boson is excluded for a mass in the range [129 - 270] GeV/c
2 at 95% C.L.
Main Results
A search has been made for a Higgs boson decaying in a pair of W bosons in the CMS detector.
Events are classified according the exclusive jet multiplicity: 0, 1 and 2. The analysis of events with 0, 1 jets
is optimized for gg → H → WW, while the one for events with 2 jets is optimized for Vector Boson Fusion
(VBF) qq → H → WW.
A cut and count and Multivariate (Boosted Decision Tree - BDT) analysis is performed, optimized for each mass point.
The main backgrounds (W
+W
-, top, Drell Yan, W+jets) are estimated
with data-driven techniques. The uncertainty on the background normalization represent the largest source of systematics of the analysis,
together with the theoretical uncertainties on the Higgs cross section.
No evidence of Higgs boson is found and the results are interpreted as an exclusion of a wide H mass range.
With a
multivariate shape analysis, the expected exclusion range at 95% CL is between 127 and 270 GeV for a Standard Model Higgs, while the observed one is
[129 - 270] GeV/c2 at 95% C.L. using the CL
s approach.
With the
cut based analysis, the expected exclusion range at 95% CL is between 129 and 236 GeV for a Standard Model Higgs, while the observed one is
[132 - 238] GeV/c2 at 95% C.L. using the CL
s approach.
The excess of events observed for hypothesised Higgs boson masses at the
low end of the explored range makes the observed limits weaker than the
expected ones. To ascertain the origin of this excess, more data are required.
Below we report the table with detailed exclusion limits for a range of masses 110-300 GeV/c
2.
- results with the BDT analysis:
| Higgs Mass |
Observed |
Median exp. |
68% band |
95% band |
| 110 |
8.81 |
5.59 |
[4.21, 8.02] |
[3.47, 11.0] |
| 115 |
5.05 |
2.70 |
[1.97, 3.86] |
[1.62, 5.35] |
| 120 |
2.69 |
1.58 |
[1.14, 2.28] |
[0.91, 3.15] |
| 125 |
1.52 |
1.12 |
[0.80, 1.55] |
[0.60, 2.08] |
| 130 |
0.97 |
0.75 |
[0.53, 1.07] |
[0.41, 1.46] |
| 140 |
0.66 |
0.43 |
[0.31, 0.61] |
[0.25, 0.84] |
| 150 |
0.46 |
0.29 |
[0.21, 0.42] |
[0.16, 0.57] |
| 160 |
0.25 |
0.15 |
[0.11, 0.22] |
[0.10, 0.31] |
| 170 |
0.27 |
0.17 |
[0.13, 0.24] |
[0.10, 0.34] |
| 180 |
0.29 |
0.25 |
[0.18, 0.35] |
[0.14, 0.48] |
| 190 |
0.37 |
0.37 |
[0.27, 0.54] |
[0.21, 0.74] |
| 200 |
0.53 |
0.52 |
[0.37, 0.73] |
[0.29, 1.02] |
| 250 |
0.85 |
0.96 |
[0.69, 1.41] |
[0.56, 1.93] |
| 300 |
1.25 |
1.09 |
[0.77, 1.57] |
[0.62, 2.16] |
| 350 |
1.02 |
0.98 |
[0.70, 1.40] |
[0.58, 1.95] |
| 400 |
1.38 |
1.04 |
[0.77, 1.47] |
[0.63, 2.09] |
| 450 |
1.08 |
1.44 |
[1.02, 2.08] |
[0.80, 3.01] |
| 500 |
1.14 |
1.91 |
[1.27, 2.91] |
[0.96, 4.31] |
| 550 |
2.05 |
2.76 |
[1.88, 4.26] |
[1.39, 6.14] |
| 600 |
1.92 |
3.85 |
[2.44, 6.22] |
[1.73, 10.3] |
 |
png, pdf |
Exclusion limit with shape analysis |
- results with the cut-based analysis:
| Higgs Mass |
Observed |
Median exp. |
68% band |
95% band |
| 110 |
8.7 |
6.6 |
[4.8, 9.3] |
[3.7, 13.0] |
| 115 |
4.0 |
3.2 |
[2.3, 4.4] |
[1.9, 6.3] |
| 120 |
2.4 |
1.9 |
[1.4, 2.6] |
[1.1, 3.7] |
| 130 |
1.2 |
0.8 |
[0.6, 1.2] |
[0.5, 1.7] |
| 140 |
0.6 |
0.5 |
[0.4, 0.7] |
[0.3, 1.0] |
| 150 |
0.5 |
0.4 |
[0.3, 0.6] |
[0.2, 0.7] |
| 160 |
0.3 |
0.2 |
[0.2, 0.3] |
[0.1, 0.4] |
| 170 |
0.3 |
0.2 |
[0.2, 0.3] |
[0.1, 0.4] |
| 180 |
0.2 |
0.3 |
[0.2, 0.4] |
[0.2, 0.6] |
| 190 |
0.2 |
0.4 |
[0.2, 0.6] |
[0.2, 0.8] |
| 200 |
0.6 |
0.6 |
[0.4, 0.9] |
[0.4, 1.2] |
| 250 |
1.1 |
1.3 |
[0.7, 1.8] |
[0.7, 2.5] |
| 300 |
1.7 |
1.5 |
[1.1, 2.1] |
[0.8, 3.0] |
| 350 |
1.5 |
1.4 |
[1.1, 2.0] |
[0.8, 2.9] |
| 400 |
1.7 |
1.6 |
[1.1, 2.2] |
[0.8, 3.1] |
| 450 |
1.8 |
1.8 |
[1.3, 2.8] |
[1.0, 4.0] |
| 500 |
2.3 |
2.6 |
[1.8, 3.9] |
[1.4, 5.9] |
| 550 |
3.9 |
3.6 |
[2.5, 5.4] |
[1.9, 8.5] |
| 600 |
5.9 |
5.0 |
[3.5, 7.9] |
[2.8, 12.8] |
 |
png, pdf |
Exclusion limit with cut-based analysis |
Paper figures
 |
png, pdf |
Δφ ll in the 0-jet bin at WW selection level |
 |
png, pdf |
Δφ ll in the 1-jet bin at WW selection level |
 |
png, pdf |
dilepton invariant mass in the 0-jet bin at Higgs selection level |
 |
png, pdf |
dilepton invariant mass in the 1-jet bin at Higgs selection level |
 |
png, pdf |
BDT output in the 0-jet bin for opposite flavor final state |
 |
png, pdf |
BDT output in the 0-jet bin for same flavor final state |
 |
png, pdf |
BDT output in the 1-jet bin for opposite flavor final state |
 |
png, pdf |
BDT output in the 1-jet bin for same flavor final state |
Paper tables
Yields at the WW selection level
Backgrounds are rescaled to the data-driven expectations
| njets |
data |
all bkg. |
qq→WW |
gg→WW |
ttbar+tW |
W+jets |
| 0-jet |
1359 |
1364.8 ± 9.3 |
980.6 ± 5.2 |
58.8 ± 0.7 |
147.3 ± 2.5 |
99.3 ± 5.0 |
| 1-jet |
909 |
951.4 ± 9.8 |
416.8 ± 3.6 |
23.8 ± 0.5 |
334.8 ± 3.0 |
74.3 ± 4.6 |
| 2-jet |
703 |
714.8 ± 13.5 |
154.7 ± 2.2 |
5.1 ± 0.2 |
413.5 ± 2.7 |
37.9 ± 3.6 |
| njets |
WZ/ZZ |
DY→ll |
Wγ |
DY→ττ |
| 0-jet |
33.0 ± 0.5 |
16.6 ± 4.0 |
26.8 ± 3.5 |
2.4 ± 0.5 |
| 1-jet |
28.7 ± 0.5 |
39.4 ± 6.4 |
13.0 ± 2.6 |
20.6 ± 0.4 |
| 2-jet |
15.1 ± 0.3 |
56.1 ± 11.7 |
10.8 ± 3.6 |
21.6 ± 2.1 |
Yields at the Higgs selection level
- cut based approach in the 0-jet category:
| mH |
DY→ll |
ttbar+tW |
W+jets |
WZ+ZZ+Wγ |
WW |
all bkg. |
H→WW |
data |
| 120 |
8.8 ± 9.2 |
6.7 ± 1.0 |
14.7 ± 4.7 |
6.1 ± 1.5 |
100.3 ± 7.2 |
136.7 ± 12.7 |
15.7 ± 0.8 |
136 |
| 130 |
13.7 ± 7.8 |
10.6 ± 1.6 |
17.6 ± 5.5 |
7.4 ± 1.6 |
142.2 ± 10.0 |
191.5 ± 14.0 |
45.2 ± 2.1 |
193 |
| 160 |
3.4 ± 3.4 |
10.5 ± 1.4 |
3.0 ± 1.5 |
2.2 ± 0.4 |
82.6 ± 5.4 |
101.7 ± 6.8 |
122.9 ± 5.6 |
111 |
| 200 |
2.7 ± 3.7 |
23.3 ± 3.1 |
3.4 ± 1.5 |
3.2 ± 0.3 |
108.2 ± 4.5 |
140.8 ± 6.8 |
48.8 ± 2.2 |
159 |
| 250 |
0.3 ± 0.6 |
36.2 ± 4.8 |
6.7 ± 2.1 |
5.7 ± 0.7 |
101.8 ± 4.5 |
150.8 ± 6.9 |
23.5 ± 1.1 |
152 |
| 300 |
0.7 ± 1.9 |
41.6 ± 5.4 |
6.5 ± 2.1 |
7.0 ± 0.7 |
87.5 ± 3.9 |
143.3 ± 7.2 |
20.2 ± 0.9 |
147 |
| 400 |
0.2 ± 0.2 |
35.9 ± 4.7 |
5.5 ± 1.8 |
9.3 ± 1.1 |
59.8 ± 2.7 |
110.8 ± 5.8 |
17.5 ± 0.8 |
109 |
- breakdown by channel for one mass (uncertainty on signal reporting also theory systematics) (mH=120 GeV)
- cut based approach in the 1-jet category:
| mH |
DY→ll |
ttbar+tW |
W+jets |
WZ+ZZ+Wγ |
WW |
all bkg. |
H→WW |
data |
| 120 |
6.6 ± 2.3 |
17.2 ± 1.0 |
5.4 ± 2.4 |
3.2 ± 0.6 |
27.0 ± 4.7 |
59.5 ± 5.9 |
6.5 ± 0.3 |
72 |
| 130 |
5.3 ± 2.5 |
25.6 ± 1.4 |
6.5 ± 2.5 |
4.0 ± 0.6 |
38.5 ± 6.6 |
79.9 ± 7.7 |
17.6 ± 0.8 |
105 |
| 160 |
4.2 ± 1.4 |
27.9 ± 1.4 |
3.2 ± 1.4 |
1.9 ± 0.3 |
33.7 ± 5.5 |
70.8 ± 6.0 |
60.2 ± 2.6 |
86 |
| 200 |
14.6 ± 5.3 |
59.4 ± 2.8 |
5.2 ± 1.8 |
2.2 ± 0.1 |
49.3 ± 2.2 |
130.8 ± 6.7 |
25.8 ± 1.1 |
111 |
| 250 |
12.9 ± 6.8 |
83.8 ± 3.9 |
5.9 ± 2.1 |
3.3 ± 0.2 |
60.3 ± 2.8 |
166.2 ± 8.6 |
14.8 ± 0.6 |
158 |
| 300 |
12.8 ± 4.8 |
83.6 ± 3.9 |
6.2 ± 2.2 |
3.8 ± 0.4 |
57.5 ± 2.7 |
163.9 ± 7.1 |
13.7 ± 0.6 |
168 |
| 400 |
8.3 ± 3.2 |
60.6 ± 2.9 |
6.2 ± 2.1 |
3.9 ± 0.5 |
44.6 ± 2.2 |
123.6 ± 5.3 |
12.2 ± 0.5 |
128 |
- breakdown by channel for one mass (uncertainty on signal reporting also theory systematics) (mH=120 GeV)
- cut based approach in the 2-jet category:
| mH |
DY→ll |
ttbar+tW |
W+jets |
WZ+ZZ+Wγ |
WW |
all bkg. |
H→WW |
data |
| 120 |
1.9 ± 1.4 |
5.5 ± 2.8 |
0.7 ± 0.6 |
1.8 ± 1.5 |
1.3 ± 0.2 |
11.3 ± 3.6 |
1.1 ± 0.1 |
8 |
| 130 |
2.7 ± 1.9 |
6.5 ± 3.2 |
0.7 ± 0.6 |
1.8 ± 1.5 |
1.6 ± 0.2 |
13.3 ± 4.0 |
2.7 ± 0.2 |
10 |
| 160 |
2.7 ± 1.9 |
8.4 ± 3.9 |
1.2 ± 0.8 |
1.8 ± 1.5 |
1.9 ± 0.2 |
15.9 ± 4.6 |
12.2 ± 0.7 |
12 |
| 200 |
3.2 ± 2.1 |
9.4 ± 4.2 |
1.2 ± 0.8 |
1.8 ± 1.5 |
2.2 ± 0.2 |
17.8 ± 5.0 |
8.4 ± 0.5 |
13 |
| 250 |
3.3 ± 2.1 |
12.2 ± 5.2 |
1.2 ± 0.8 |
1.9 ± 1.5 |
3.3 ± 0.3 |
21.8 ± 5.9 |
5.6 ± 0.3 |
19 |
| 300 |
3.3 ± 2.1 |
14.1 ± 5.8 |
1.1 ± 0.8 |
1.9 ± 1.5 |
3.4 ± 0.3 |
23.7 ± 6.4 |
4.2 ± 0.2 |
20 |
| 400 |
3.3 ± 2.1 |
14.1 ± 5.8 |
1.1 ± 0.8 |
1.9 ± 1.5 |
3.5 ± 0.3 |
23.8 ± 6.4 |
2.5 ± 0.1 |
20 |
Other figures
Kinematic variables at the WW selection level
 |
 |
 |
Δφ ll the 0-jet / 1-jet / 2-jet bin at the Higgs selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
 |
 |
 |
dilepton invariant mass the 0-jet / 1-jet / 2-jet bin at the WW selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
 |
 |
 |
leading lepton pT the 0-jet / 1-jet / 2-jet bin at the WW selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
 |
 |
 |
trailing lepton pT the 0-jet / 1-jet / 2-jet bin at the WW selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
 |
 |
 |
dilepton pT the 0-jet / 1-jet / 2-jet bin at the WW selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
 |
 |
 |
transverse mass the 0-jet / 1-jet / 2-jet bin at the WW selection level |
| png, pdf |
png, pdf |
png, pdf |
other formats |
Kinematic variables at the Higgs selection level
 |
 |
Δφ ll in the 0-jet / 1-jet at the Higgs selection level |
| png, pdf |
png, pdf |
other formats |
 |
 |
dilepton invariant mass in the 0-jet / 1-jet at the Higgs selection level |
| png, pdf |
png, pdf |
other formats |
 |
 |
leading lepton pT in the 0-jet / 1-jet at the Higgs selection level |
| png, pdf |
png, pdf |
other formats |
 |
 |
trailing lepton pT in the 0-jet / 1-jet at the Higgs selection level |
| png, pdf |
png, pdf |
other formats |
 |
 |
transverse mass in the 0-jet / 1-jet at the Higgs selection level |
| png, pdf |
png, pdf |
other formats |
Cuts evolution
 |
 |
cuts evolution in 0-jet for mH = 130 / 140 GeV. |
| png, pdf |
png, pdf |
other formats |
Cut based exclusion limits
 |
 |
0-jet opposite flavor / same flavor. |
| png, pdf |
png, pdf |
other formats |
 |
 |
1-jet opposite flavor / same flavor. |
| png, pdf |
png, pdf |
other formats |
 |
2-jet. |
| png, pdf |
other formats |
 |
 |
0+1+2 jets combined limit, zoom at low mass. |
| png, pdf |
png, pdf |
other formats |
Shape based exclusion limits
- Boosted Decision Tree results
- Dilepton invariant mass resuts:
The following describe the distribution of the dilepton invariant mass used to extract the limits:
 |
 |
 |
 |
Delta Phi ll in the 0-jet OF / 0-jet SF / 1-jet OF / 1-jet SF at the Higgs selection level except mll selection |
| png, pdf |
png, pdf |
png, pdf |
png, pdf |
other formats |
The following figures show the results obtained with the mll:
 |
0+1+2 jet combined. Zoom at low mass. |
| png, pdf |
other formats |
Signal Injection test
The figure shows the test where, on top of the expected background, we injected a signal of Higgs boson with
mH=124 GeV. Results are obtained with asymptotic CLs approximation with BDT shape analysis.
 |
 |
mH=124 GeV signal injected for cut-based / BDT-based. Zoom at low mass. |
| png, pdf |
png, pdf |
other formats |
Fermiophobic Higgs limits
 |
 |
Fermiophobic Higgs limit in low / full mass. |
| png, pdf |
png, pdf |
other formats |
| Higgs Mass |
Observed |
Median exp. |
68% band |
95% band |
| 110 |
2.0 |
2.3 |
[1.6, 3.7] |
[1.1, 6.0] |
| 115 |
1.6 |
2.0 |
[1.3, 3.1] |
[1.0, 5.1] |
| 120 |
1.4 |
1.7 |
[1.1, 2.5] |
[0.8, 4.0] |
| 130 |
1.3 |
1.5 |
[1.0, 2.4] |
[0.7, 3.8] |
| 140 |
1.1 |
1.4 |
[1.0, 2.2] |
[0.7, 3.6] |
| 150 |
1.0 |
1.3 |
[0.9, 2.1] |
[0.6, 3.4] |
| 160 |
0.8 |
1.0 |
[0.7, 1.6] |
[0.5, 2.7] |
| 170 |
0.7 |
1.0 |
[0.6, 1.5] |
[0.4, 2.4] |
| 180 |
0.8 |
1.1 |
[0.7, 1.8] |
[0.5, 3.0] |
| 190 |
1.0 |
1.4 |
[0.9, 2.2] |
[0.7, 3.8] |
| 200 |
1.3 |
1.7 |
[1.1, 2.7] |
[0.8, 4.5] |
| 250 |
2.3 |
3.0 |
[2.0, 5.0] |
[1.4, 9.0] |
| 300 |
3.3 |
4.0 |
[2.7, 6.5] |
[1.9, 10.5] |
| 350 |
4.4 |
5.5 |
[3.7, 8.3] |
[2.6, 12.8] |
| 400 |
6.3 |
7.8 |
[5.2, 12.0] |
[3.7, 17.8] |
| 450 |
8.9 |
10.9 |
[7.3, 16.9] |
[5.2, 26.1] |
| 500 |
11.6 |
14.2 |
[9.4, 21.7] |
[6.6, 34.3] |
| 550 |
14.9 |
18.7 |
[12.6, 28.6] |
[8.8, 45.1] |
| 600 |
18.9 |
24.8 |
[16.4, 38.3] |
[11.7, 59.7] |
EPS 2011 vs post EPS 2011
We have reanalyzed the dataset presented at EPS 2011 conference with the new analysis (1.1 fb
-1). We find the same excess shown before, while the excess is no more there in the full dataset minus the EPS dataset. We conclude that it was a statistical fluctuation.
 |
 |
Current analysis performed on EPS2011 / post-EPS2011 dataset. |
| png, pdf |
png, pdf |
other formats |
Selections definition
WW selection
The following cuts constitute what in the paper is called
WW selection (which in independent on the Higgs mass)
| Selection [units] |
ee,μμ |
eμ |
| pTmax [GeV/c] |
20 |
20 |
| pTmin [GeV/c] |
15 |
10 |
| third lepton veto |
applied |
applied |
| opposite-sign requirement |
applied |
applied |
| mll [GeV/c2] |
20 |
12 |
| projected MET [GeV] |
40 |
20 |
| Z mass veto |
applied |
--- |
| Δφ(ll-jetmax) [dg.] |
165 |
--- |
| top veto |
applied |
applied |
| pTll [GeV/c] |
45 |
45 |
Higgs selection
The following cuts constitute what in the paper is called
Higgs selection (which is
dependent on the Higgs mass)
| mH |
pTmax |
pTmin |
mll |
Δφll |
mT |
| [GeV/c2] |
[GeV/c] |
[GeV/c] |
[GeV/c2] |
dg. |
[GeV/c2] |
| 115 |
20 |
10(15) |
40 |
115 |
[80,110] |
| 120 |
20 |
10(15) |
40 |
115 |
[80,120] |
| 130 |
25 |
10(15) |
45 |
90 |
[80,125] |
| 140 |
25 |
15 |
45 |
90 |
[80,130] |
| 150 |
27 |
25 |
50 |
90 |
[80,150] |
| 160 |
30 |
25 |
50 |
60 |
[90,160] |
| 170 |
34 |
25 |
50 |
60 |
[110,170] |
| 180 |
36 |
25 |
60 |
70 |
[120,180] |
| 190 |
38 |
25 |
80 |
90 |
[120,190] |
| 200 |
40 |
25 |
90 |
100 |
[120,200] |
| 250 |
55 |
25 |
150 |
140 |
[120,250] |
| 300 |
70 |
25 |
200 |
175 |
[120,300] |
| 350 |
80 |
25 |
250 |
175 |
[120,350] |
| 400 |
90 |
25 |
300 |
175 |
[120,400] |
| 450 |
110 |
25 |
350 |
175 |
[120,450] |
| 500 |
120 |
25 |
400 |
175 |
[120,500] |
| 550 |
130 |
25 |
450 |
175 |
[120,550] |
| 600 |
140 |
25 |
500 |
175 |
[120,600] |
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