A
bstract
In the framework of the Standard Model effective field theory, we examine the indirect constraints on the trilinear Higgs coupling λ that arise from Higgs production in gluon-gluon-fusion ...and diphoton Higgs decays. We calculate 2-loop contributions to the
gg
→
h
and
h
→ γγ amplitudes that are affected by modifications of the trilinear Higgs-boson vertex. Based on our new results, we analyse the sensitivity of present and future measurements of the
hgg
and
h
γγ couplings to shifts in λ. Under the assumption that
O
6
= −λ (
H
†
H
)
3
is the only dimension-6 operator that alters the trilinear Higgs interactions, we find that at present the considered loop-level probes provide stronger constraints than
pp
→ 2
h
. At future high-energy colliders indirect
O
5
determinations of the trilinear Higgs coupling may be possible, making precision measurements of
gg
→
h
and
h
→ γγ a useful addition to direct extractions of λ through double-Higgs production.
A
bstract
In this article, we demonstrate that the unexpected peak at around 95 GeV as seen recently by CMS in the di-photon final state can be explained within the type-I two-Higgs-doublet model by ...means of a moderately-to-strongly fermiophobic CP-even Higgs
H
. Depending on the Higgs mass spectrum, the production of such a
H
arises dominantly from vector boson fusion or through a cascade in either
pp
→
t
t
¯
with
t
−
→
H
±
b
−
→
W
±
*
H
b
−
or
pp
→
A
with
A
→
W
∓
H
±
→
W
∓
W
±
H
or via
pp
→
W
± ∗
→
H
±
H
. In this context, we also discuss other Higgs anomalies such as the LEP excess in Higgsstrahlung and the observation of enhanced rates in
t
t
¯
h
at both the Tevatron and the LHC, showing that parameters capable of explaining the CMS di-photon signal can address the latter deviations as well. The Higgs spectra that we explore comprise masses between 80 GeV and 350 GeV. While at present all constraints from direct and indirect searches for spin-0 resonances can be shown to be satisfied for such light Higgses, future LHC data will be able to probe the parameter space that leads to a simultaneous explanation of the discussed anomalies.
A
bstract
Stringent limits on the interactions between dark matter (DM) and the standard model (SM) can be set by studying how initial-state or final-state particles recoil against missing transverse ...energy
. In this work, we improve, extend and correct LHC constraints on the interactions between DM and top quarks that are mediated by the exchange of spin-0
s
-channel resonances. A comparison of the LHC run-1 sensitivity of the two main search channels is presented, which shows that mono-jet searches are typically more restrictive than the
searches. We furthermore explore the reach of the 14 TeV LHC. The collider constraints are compared to the restrictions arising from direct and indirect detection as well as the DM relic abundance, and we also reflect on effective field theory (EFT) interpretations of the LHC exclusions.
A
bstract
Given the hints of lepton-flavour non-universality in
B
-meson decays, leptoquarks (LQs) are enjoying a renaissance. We propose novel Large Hadron Collider (LHC) searches for such ...hypothetical states that do not rely on strong production only, but can also receive important contributions from quark-lepton annihilation. For the cases of a resonant signal involving a bottom quark and a tau lepton (
b
+
τ
), a top quark and missing transverse energy (
E
T
miss
) and light-flavour jets plus
E
T
miss
, we develop realistic analysis strategies and provide detailed evaluations of the achievable sensitivities for the corresponding LQ signatures at future LHC runs. Our analyses allow us to derive a series of stringent constraints on the masses and couplings of third-generation singlet vector LQs, showing that at LHC Run III and the high-luminosity LHC the proposed search channels can probe interesting parts of the LQ parameter space addressing the
B
-physics anomalies. In view of the reach of the proposed
b
+
τ
signature, we recommend that dedicated resonance searches for this final state should be added to the exotics search canon of both ATLAS and CMS.
A
bstract
We estimate the size of the hadronic matrix elements of CP-violating three-gluon and four-gluon Weinberg operators using sum-rule techniques. In the three-gluon case, we are able to ...reproduce the expressions given in earlier works, while the four-gluon results obtained in this article are new. Our paper therefore represents the first systematic study of contributions to the electric dipole moment of the neutron due to CP-violating dimension-six and dimension-eight operators. We provide many details on both the derivation of the sum rules as well as the analysis of the uncertainties that plague our final predictions.
A
bstract
We study a new class of renormalisable simplified models for dark matter searches at the LHC that are based on two Higgs doublet models with an additional pseudoscalar mediator. In contrast ...to the spin-0 simplified models employed in analyses of Run I data these models are self-consistent, unitary and bounds from Higgs physics typically pose no constraints. Predictions for various missing transverse energy (
E
T
,miss
) searches are discussed and the reach of the 13 TeV LHC is explored. It is found that the proposed models provide a rich spectrum of complementary observables that lead to non-trivial constraints. We emphasise in this context the sensitivity of the
t
t
¯
+
E
T
,
miss
, mono-
Z
and mono-Higgs channels, which yield stronger limits than mono-jet searches in large parts of the parameter space. Constraints from spin-0 resonance searches, electroweak precision measurements and flavour observables are also derived and shown to provide further important handles to constraint and to test the considered dark matter models.
A
bstract
In the context of the Standard Model effective field theory (SMEFT) we examine the constraints on the trilinear Higgs coupling that originate from off-shell Higgs production in ...proton-proton collisions. Our calculation of the
gg
→
h
*
→
ZZ
→ 4
ℓ
process includes two-loop corrections to gluon-gluon-fusion Higgs production and one-loop corrections to the Higgs propagator and its decay. Employing a matrix-element based kinematic discriminant we determine the reach of LHC Run 3 and the high-luminosity option of the LHC in constraining the relevant SMEFT Wilson coefficients. We present constraints that are not only competitive with but also complementary to the projected indirect limits that one expects to obtain from inclusive measurements of single-Higgs production processes at future LHC runs.
A
bstract
Discovering CP-violating effects in the Higgs sector would constitute an indisputable sign of physics beyond the Standard Model. We derive constraints on the CP-violating Higgs-boson ...couplings to top and bottom quarks as well as to tau leptons from low-energy bounds on electric dipole moments, resumming large logarithms when necessary. The present and future projections of the sensitivities and comparisons with the LHC constraints are provided. Non-trivial constraints are possible in the future, even if the Higgs boson only couples to the third-generation fermions.
We propose a novel strategy to constrain the bottom and charm Yukawa couplings by exploiting Large Hadron Collider (LHC) measurements of transverse momentum distributions in Higgs production. Our ...method does not rely on the reconstruction of exclusive final states or heavy-flavor tagging. Compared to other proposals, it leads to an enhanced sensitivity to the Yukawa couplings due to distortions of the differential Higgs spectra from emissions which either probe quark loops or are associated with quark-initiated production. We derive constraints using data from LHC run I, and we explore the prospects of our method at future LHC runs. Finally, we comment on the possibility of bounding the strange Yukawa coupling.
A
bstract
Higgs decays displaced from the primary interaction vertex represent a striking experimental signature that is actively searched for by the ATLAS, CMS and LHCb collaborations. We point out ...that signals of this type appear in the context of the 2HDM+
a
model if the mixing angle
θ
of the two CP-odd weak spin-0 eigenstates is tiny and the dark matter (DM) sector is either decoupled or kinematically inaccessible. Utilising two suitable benchmark scenarios, we determine the constraints on the parameter space of the 2HDM+
a
model that are set by the existing LHC searches for long-lived particles (LLPs) in Higgs decays. We find that depending on the precise mass spectrum of the spin-0 states, mixing angles
θ
in the ballpark of a few 10
−
8
to 10
−
5
can be excluded based on LHC Run II data. This finding emphasises the unique role that searches for displaced signatures can play in constraining the parameter space of the 2HDM+
a
model. The ensuing DM phenomenology is also discussed. In particular, we show that parameter choices leading to an interesting LLP phenomenology can simultaneously explain the DM abundance observed in today’s Universe.
PDF
