Abstract
A search for the Higgs boson decaying into a pair of charm quarks is presented. The analysis uses proton–proton collisions to target the production of a Higgs boson in association with a leptonically decaying
W
or
Z
boson. The dataset delivered by the LHC at a centre-of-mass energy of
and recorded by the ATLAS detector corresponds to an integrated luminosity of 139
fb
-
1
. Flavour-tagging algorithms are used to identify jets originating from the hadronisation of charm quarks. The analysis method is validated with the simultaneous measurement of
WW
,
WZ
and
ZZ
production, with observed (expected) significances of 2.6 (2.2) standard deviations above the background-only prediction for the
(
W
/
Z
)
Z
(
→
c
c
¯
)
process and 3.8 (4.6) standard deviations for the
(
W
/
Z
)
W
(
→
c
q
)
process. The
(
W
/
Z
)
H
(
→
c
c
¯
)
search yields an observed (expected) upper limit of 26 (31) times the predicted Standard Model cross-section times branching fraction for a Higgs boson with a mass of
, corresponding to an observed (expected) constraint on the charm Yukawa coupling modifier
|
κ
c
|
<
8.5
(
12.4
)
, at the 95% confidence level. A combination with the ATLAS
(
W
/
Z
)
H
,
H
→
b
b
¯
analysis is performed, allowing the ratio
κ
c
/
κ
b
to be constrained to less than 4.5 at the 95% confidence level, smaller than the ratio of the b- and c-quark masses, and therefore determines the Higgs-charm coupling to be weaker than the Higgs-bottom coupling at the 95% confidence level.
