OTHER ${{\mathit H}}$ PRODUCTION PROPERTIES

${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ Production

INSPIRE   JSON  (beta) PDGID:
S126STH
Signal strength relative to the Standard Model cross section.
VALUE DOCUMENT ID TECN  COMMENT
$\bf{ 1.10 \pm0.18}$ OUR AVERAGE
$0.92$ $\pm0.19$ ${}^{+0.17}_{-0.13}$ 1
SIRUNYAN
2021R
 CMS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
$1.2$ $\pm0.3$ 2
AABOUD
2018AC
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
$1.9$ ${}^{+0.8}_{-0.7}$ 3
AAD
2016AN
 ATLS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
• • We do not use the following data for averages, fits, limits, etc. • •
$-0.27$ ${}^{+0.86}_{-0.83}$ 4
TUMASYAN
2023AI
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, boosted ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
$0.35$ ${}^{+0.36}_{-0.34}$ 5
AAD
2022M
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
$1.43$ ${}^{+0.33}_{-0.31}$ ${}^{+0.21}_{-0.15}$ 6
AAD
2020Z
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
$1.38$ ${}^{+0.36}_{-0.29}$ 7
SIRUNYAN
2020AS
 CMS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
$0.72$ $\pm0.24$ $\pm0.38$ 8
SIRUNYAN
2019R
 CMS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
$1.6$ ${}^{+0.5}_{-0.4}$ 9
AABOUD
2018AC
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
10
AABOUD
2018BK
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}{{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
$0.84$ ${}^{+0.64}_{-0.61}$ 11
AABOUD
2018T
 ATLS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
$0.9$ $\pm1.5$ 12
SIRUNYAN
2018BD
 CMS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
$1.23$ ${}^{+0.45}_{-0.43}$ 13
SIRUNYAN
2018BQ
 CMS ${{\mathit p}}{{\mathit p}}$, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
$1.26$ ${}^{+0.31}_{-0.26}$ 14
SIRUNYAN
2018L
 CMS ${{\mathit p}}{{\mathit p}}$, 7, 8, 13 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$, ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$
$1.7$ $\pm0.8$ 15
AAD
2016AL
 ATLS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$, ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, and ${{\mathit Z}}{{\mathit Z}^{*}}$
$2.3$ ${}^{+0.7}_{-0.6}$ 16, 3
AAD
2016AN
 LHC ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
$2.9$ ${}^{+1.0}_{-0.9}$ 3
AAD
2016AN
 CMS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
$1.81$ ${}^{+0.52}_{-0.50}$ ${}^{+0.58}_{-0.55}$ ${}^{+0.31}_{-0.12}$ 17
AAD
2016K
 ATLS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
$1.4$ ${}^{+2.1}_{-1.4}$ ${}^{+0.6}_{-0.3}$ 18
AAD
2015
ATLS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
$1.5$ $\pm1.1$ 19
AAD
2015BC
 ATLS ${{\mathit p}}{{\mathit p}}$, 8 TeV
$2.1$ ${}^{+1.4}_{-1.2}$ 20
AAD
2015T
 ATLS ${{\mathit p}}{{\mathit p}}$, 8 TeV
$1.2$ ${}^{+1.6}_{-1.5}$ 21
KHACHATRYAN
2015AN
 CMS ${{\mathit p}}{{\mathit p}}$, 8 TeV
$2.8$ ${}^{+1.0}_{-0.9}$ 22
KHACHATRYAN
2014H
 CMS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV
$9.49$ ${}^{+6.60}_{-6.28}$ 23
AALTONEN
2013L
 CDF ${{\mathit p}}{{\overline{\mathit p}}}$, 1.96 TeV
$< 5.8 at 95\% CL$ 24
CHATRCHYAN
2013X
 CMS ${{\mathit p}}{{\mathit p}}$, 7, 8 TeV, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$
1  SIRUNYAN 2021R search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ in final states with electrons, muons and hadronically decaying ${{\mathit \tau}}$ leptons (${{\mathit H}}$ $\rightarrow$ ${{\mathit W}}{{\mathit W}^{*}}$ , ${{\mathit Z}}{{\mathit Z}^{*}}$ , ${{\mathit \tau}}{{\mathit \tau}}$) with 137 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collision data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength corresponds to a significance of 4.7 standard deviations and is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
2  AABOUD 2018AC combine results of ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$, ${{\mathit H}}$ $\rightarrow$ ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit W}}{{\mathit W}^{*}}(\rightarrow$ ${{\mathit \ell}}{{\mathit \nu}}{{\mathit \ell}}{{\mathit \nu}}$, ${{\mathit \ell}}{{\mathit \nu}}{{\mathit q}}{{\overline{\mathit q}}}$), ${{\mathit Z}}{{\mathit Z}^{*}}(\rightarrow$ ${{\mathit \ell}}{{\mathit \ell}}{{\mathit \nu}}{{\mathit \nu}}$, ${{\mathit \ell}}{{\mathit \ell}}{{\mathit q}}{{\overline{\mathit q}}}$) with results of ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ (AABOUD 2018T), ${{\mathit \gamma}}{{\mathit \gamma}}$ (AABOUD 2018BO), ${{\mathit Z}}{{\mathit Z}^{*}}(\rightarrow$ 4 ${{\mathit \ell}}$) (AABOUD 2018AJ) in 36.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV. See their Table 14.
3  AAD 2016AN: In the fit, relative branching ratios are fixed to those in the Standard Model. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125.09 GeV.
4  TUMASYAN 2023AI measure boosted ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ ($p_T$ $>$ 200 GeV) in ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production using 138 fb${}^{-1}$ of data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The differential cross section for the Higgs $p_T$ is shown in their Fig. 8 and Table V. Limits on eight Wilson coefficients at 68$\%$ and 95$\%$ CL are shown in their Fig. 10 and Table VI.
5  AAD 2022M measure ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ in ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production using 139 fb${}^{-1}$ of data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. See their Fig. 14. The signal strengths and 95$\%$ CL cross section upper limits with simplified template cross section bins are given in their Figs. 18 and 19, respectively.
6  AAD 2020Z measure $\sigma _{{{\mathit t}} {{\overline{\mathit t}}} {{\mathit H}}}$ $\cdot{}B({{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$) to be $1.64$ ${}^{+0.38}_{-0.36}{}^{+0.17}_{-0.14}$ fb in 139 fb${}^{-1}$ of data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV.
7  SIRUNYAN 2020AS measure $\sigma _{{{\mathit t}} {{\overline{\mathit t}}} {{\mathit H}}}\cdot{}B({{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$) to be $1.56$ ${}^{+0.34}_{-0.32}$ fb in 137 fb${}^{-1}$ of data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV.
8  SIRUNYAN 2019R search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ in 35.9 fb${}^{-1}$ of data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
9  AABOUD 2018AC search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit W}}{{\mathit W}^{*}}(\rightarrow$ ${{\mathit \ell}}{{\mathit \nu}}{{\mathit \ell}}{{\mathit \nu}}$, ${{\mathit \ell}}{{\mathit \nu}}{{\mathit q}}{{\overline{\mathit q}}}$), ${{\mathit Z}}{{\mathit Z}^{*}}(\rightarrow$ ${{\mathit \ell}}{{\mathit \ell}}{{\mathit \nu}}{{\mathit \nu}}$, ${{\mathit \ell}}{{\mathit \ell}}{{\mathit q}}{{\overline{\mathit q}}}$) in 36.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV. See their Table 13 and Fig. 13.
10  AABOUD 2018BK use 79.8 fb${}^{-1}$ data for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ and ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$ (${{\mathit \ell}}$ = ${{\mathit e}}$, ${{\mathit \mu}}$) and 36.1 fb${}^{-1}$ for other decay channels at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. A significance of 5.8 standard deviations is observed for ${\mathit m}_{{{\mathit H}}}$ = 125.09 GeV and its signal strength without the uncertainty of the ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ cross section is $1.32$ ${}^{+0.28}_{-0.26}$. Combining with results of 7 and 8 TeV (AAD 2016K), the significance is 6.3 standard deviations. Assuming Standard Model branching fractions, the total ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production cross section at 13 TeV is measured to be $670$ $\pm90$ ${}^{+110}_{-100}$ fb.
11  AABOUD 2018T search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ in 36.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
12  SIRUNYAN 2018BD search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$, ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ in the all-jet final state with 35.9 fb${}^{-1}{{\mathit p}}{{\mathit p}}$ collision data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
13  SIRUNYAN 2018BQ search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ in final states with electrons, muons and hadronically decaying ${{\mathit \tau}}$ leptons (${{\mathit H}}$ $\rightarrow$ ${{\mathit W}}{{\mathit W}^{*}}$ , ${{\mathit Z}}{{\mathit Z}^{*}}$ , ${{\mathit \tau}}{{\mathit \tau}}$) with 35.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collision data at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV. The quoted signal strength corresponds to a significance of 3.2 standard deviations and is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
14  SIRUNYAN 2018L use up to 5.1, 19.7 and 35.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7, 8, and 13 TeV, respectively. The quoted signal strength corresponds to a significance of 5.2 standard deviations and is given for ${\mathit m}_{{{\mathit H}}}$ = 125.09 GeV. ${{\mathit H}}$ decay channels of ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit \tau}}{{\mathit \tau}}$, and ${{\mathit b}}{{\overline{\mathit b}}}$ are used. See their Table 1 and Fig. 2 for results on individual channels.
15  AAD 2016AL search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit \gamma}}{{\mathit \gamma}}$ in 4.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and ${{\mathit b}}{{\overline{\mathit b}}}$, ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, and ${{\mathit Z}}{{\mathit Z}^{*}}$ in 20.3 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV. This paper combines the results of previous papers, and the new result of this paper only is: ${{\mathit \mu}}$ = $1.6$ $\pm2.6$.
16  AAD 2016AN perform fits to the ATLAS and CMS data at $\mathit E_{{\mathrm {cm}}}$ = 7 and 8 TeV.
17  AAD 2016K use up to 4.7 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and up to 20.3 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The third uncertainty in the measurement is theory systematics. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125.36 GeV.
18  AAD 2015 search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit \gamma}}{{\mathit \gamma}}$ in 4.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 20.3 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The quoted result on the signal strength is equivalent to an upper limit of 6.7 at 95$\%$ CL and is given for ${\mathit m}_{{{\mathit H}}}$ = 125.4 GeV.
19  AAD 2015BC search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The corresponding upper limit is 3.4 at 95$\%$ CL. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
20  AAD 2015T search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ resulting in multilepton final states (mainly from ${{\mathit W}}{{\mathit W}^{*}}$, ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit Z}}{{\mathit Z}^{*}}$) in 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The quoted result on the signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV and corresponds to an upper limit of 4.7 at 95$\%$ CL. The data sample is independent from AAD 2015 and AAD 2015BC.
21  KHACHATRYAN 2015AN search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$ in 19.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The quoted result on the signal strength is equivalent to an upper limit of 4.2 at 95$\%$ CL and is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
22  KHACHATRYAN 2014H search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production with ${{\mathit H}}$ decaying to ${{\mathit b}}{{\overline{\mathit b}}}$, ${{\mathit \tau}}{{\mathit \tau}}$, ${{\mathit \gamma}}{{\mathit \gamma}}$, ${{\mathit W}}{{\mathit W}^{*}}$, and ${{\mathit Z}}{{\mathit Z}^{*}}$, in 5.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 19.7 fb${}^{-1}$ at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125.6 GeV.
23  AALTONEN 2013L combine all CDF results with $9.45 - 10.0$ fb${}^{-1}$ of ${{\mathit p}}{{\overline{\mathit p}}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 1.96 TeV. The quoted signal strength is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV.
24  CHATRCHYAN 2013X search for ${{\mathit t}}{{\overline{\mathit t}}}{{\mathit H}}$ production followed by ${{\mathit H}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$, one top decaying to ${{\mathit \ell}}{{\mathit \nu}}$ and the other to either ${{\mathit \ell}}{{\mathit \nu}}$ or ${{\mathit q}}{{\overline{\mathit q}}}$ in 5.0 fb${}^{-1}$ and 5.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 and 8 TeV. A limit on cross section times branching ratio which corresponds to ($4.0 - 8.6$) times the expected Standard Model cross section is given for ${\mathit m}_{{{\mathit H}}}$ = $110 - 140$ GeV at 95$\%$ CL. The quoted limit is given for ${\mathit m}_{{{\mathit H}}}$ = 125 GeV, where 5.2 is expected for no signal.
References