# ${{\boldsymbol H}^{0}}$ DECAY WIDTH INSPIRE search

The total decay width for a light Higgs boson with a mass in the observed range is not expected to be directly observable at the LHC. For the case of the Standard Model the prediction for the total width is about 4 MeV, which is three orders of magnitude smaller than the experimental mass resolution. There is no indication from the results observed so far that the natural width is broadened by new physics effects to such an extent that it could be directly observable. Furthermore, as all LHC Higgs channels rely on the identification of Higgs decay products, the total Higgs width cannot be measured indirectly without additional assumptions. The different dependence of on-peak and off-peak contributions on the total width in Higgs decays to ${{\mathit Z}}{{\mathit Z}^{*}}$ and interference effects between signal and background in Higgs decays to ${{\mathit \gamma}}{{\mathit \gamma}}$ can provide additional information in this context. Constraints on the total width from the combination of on-peak and off-peak contributions in Higgs decays to ${{\mathit Z}}{{\mathit Z}^{*}}$ rely on the assumption of equal on- and off-shell effective couplings. Without an experimental determination of the total width or further theoretical assumptions, only ratios of couplings can be determined at the LHC rather than absolute values of couplings.

VALUE (GeV) CL% DOCUMENT ID TECN  COMMENT
$<1.10$ 95 1
 2017 AV
CMS ${{\mathit p}}{{\mathit p}}$ , 13 TeV, ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$
$\bf{<0.013}$ 95 2
 2016 BA
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit Z}}{{\mathit Z}^{(*)}}$ , ${{\mathit W}}{{\mathit W}^{(*)}}$
$<1.7$ 95 3
 2015 AM
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV
$>3.5 \times 10^{-12}$ 95 4
 2015 BA
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, flight distance
$<5.0$ 95 5
 2014 W
ATLS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit \gamma}}{{\mathit \gamma}}$
$<2.6$ 95 5
 2014 W
ATLS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$
• • • We do not use the following data for averages, fits, limits, etc. • • •
$<0.026$ 95 6
 2016 BA
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit W}}{{\mathit W}^{(*)}}$
$<0.0227$ 95 7
 2015 BE
ATLS ${{\mathit p}}{{\mathit p}}$ , 8 TeV, ${{\mathit Z}}{{\mathit Z}^{(*)}}$ , ${{\mathit W}}{{\mathit W}^{(*)}}$
$<0.046$ 95 8
 2015 BA
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit Z}}$ ${{\mathit Z}^{(*)}}$ $\rightarrow$ 4 ${{\mathit \ell}}$
$<3.4$ 95 9
 2014 AA
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$
$<0.022$ 95 10
 2014 D
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit Z}}{{\mathit Z}^{(*)}}$
$<2.4$ 95 11
 2014 P
CMS ${{\mathit p}}{{\mathit p}}$ , 7, 8 TeV, ${{\mathit \gamma}}{{\mathit \gamma}}$
1  SIRUNYAN 2017AV obtain an upper limit on the width from the distribution in ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$ ( ${{\mathit \ell}}$ = ${{\mathit e}}$ , ${{\mathit \mu}}$ ) decays. Data of 35.9 fb${}^{-1}$ ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 13 TeV is used. The expected limit is 1.60 GeV.
2  KHACHATRYAN 2016BA combine the ${{\mathit W}}{{\mathit W}^{(*)}}$ result with ${{\mathit Z}}{{\mathit Z}^{(*)}}$ results of KHACHATRYAN 2015BA and KHACHATRYAN 2014D.
3  KHACHATRYAN 2015AM combine ${{\mathit \gamma}}{{\mathit \gamma}}$ and ${{\mathit Z}}$ ${{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$ results. The expected limit is 2.3 GeV.
4  KHACHATRYAN 2015BA derive a lower limit on the total width from an upper limit on the decay flight distance $\tau$ $<$ $1.9 \times 10^{-13}$ s. 5.1 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 19.7 fb${}^{-1}$ at 8 TeV are used.
5  AAD 2014W use 4.5 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 20.3 fb${}^{-1}$ at 8 TeV. The expected limit is 6.2 GeV.
6  KHACHATRYAN 2016BA derive constraints on the total width from comparing ${{\mathit W}}{{\mathit W}^{(*)}}$ production via on-shell and off-shell ${{\mathit H}^{0}}$ using 4.9 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 7 TeV and 19.4 fb${}^{-1}$ at 8 TeV.
7  AAD 2015BE derive constraints on the total width from comparing ${{\mathit Z}}{{\mathit Z}^{(*)}}$ and ${{\mathit W}}{{\mathit W}^{(*)}}$ production via on-shell and off-shell ${{\mathit H}^{0}}$ using 20.3 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at $\mathit E_{{\mathrm {cm}}}$ = 8 TeV. The K factor for the background processes is assumed to be equal to that for the signal.
8  KHACHATRYAN 2015BA derive constraints on the total width from comparing ${{\mathit Z}}{{\mathit Z}^{(*)}}$ production via on-shell and off-shell ${{\mathit H}^{0}}$ with an unconstrained anomalous coupling. 4${{\mathit \ell}}$ final states 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 are used.
9  CHATRCHYAN 2014AA use 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 expected limit is 2.8 GeV.
10  KHACHATRYAN 2014D derive constraints on the total width from comparing ${{\mathit Z}}{{\mathit Z}^{(*)}}$ production via on-shell and off-shell ${{\mathit H}^{0}}$. 4${{\mathit \ell}}$ and ${{\mathit \ell}}{{\mathit \ell}}{{\mathit \nu}}{{\mathit \nu}}$ final states 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 are used.
11  KHACHATRYAN 2014P use 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 expected limit is 3.1 GeV.
References:
 SIRUNYAN 2017AV
JHEP 1711 047 Measurements of Properties of the Higgs Boson Decaying into the Four-Lepton Final State in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 13 TeV
 KHACHATRYAN 2016BA
JHEP 1609 051 Search for Higgs Boson Off-shell Production in Proton-Proton Collisions at 7 and 8 TeV and Derivation of Constraints on its Total Decay Width
EPJ C75 335 Constraints on the Off-Shell Higgs Boson Signal Strength in the High-Mass ${{\mathit Z}}{{\mathit Z}}$ and ${{\mathit W}}{{\mathit W}}$ Final States with the ATLAS Detector
PR D90 052004 Measurement of the Higgs Boson Mass from the ${{\mathit H}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ and ${{\mathit H}}$ $\rightarrow$ ${{\mathit Z}}{{\mathit Z}^{*}}$ $\rightarrow$ 4 ${{\mathit \ell}}$ Channels with the ATLAS Detector using 25 ${\mathrm {fb}}{}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ Collision Data
PL B736 64 Constraints on the Higgs Boson Width from off-Shell Production and Decay to ${{\mathit Z}}$-Boson Pairs