A
bstract
We deploy an advanced Machine Learning (ML) environment, leveraging a multi-scale cross-attention encoder for event classification, towards the identification of the
gg
→
H
→
hh
→
b
b
¯
b
b
...¯
process at the High Luminosity Large Hadron Collider (HL-LHC), where
h
is the discovered Standard Model (SM)-like Higgs boson and
H
a heavier version of it (with
m
H
>
2
m
h
). In the ensuing boosted Higgs regime, the final state consists of two fat jets. Our multi-modal network can extract information from the jet substructure and the kinematics of the final state particles through self-attention transformer layers. The diverse learned information is subsequently integrated to improve classification performance using an additional transformer encoder with cross-attention heads. We showcase that our approach surpasses current alternative methods used to establish sensitivity to this process in performance, whether solely based on kinematic analysis or combining this with mainstream ML approaches. Then, we employ various interpretive methods to evaluate the network results, including attention map analysis and visual representation of Gradient-weighted Class Activation Mapping (Grad-CAM). Finally, we note that the proposed network is generic and can be applied to analyse any process carrying information at different scales. Our code is publicly available for generic use (
https://github.com/AHamamd150/Multi-Scale-Transformer-Encoder
).
In this study, we focus on the bosonic decays of light charged Higgs bosons in the 2-Higgs Doublet Model (2HDM) Type-I. We quantify the Branching Ratios (BRs) of the
H
±
→
W
±
h
and
H
±
→
W
±
A
...channels and show that they could be substantial over several areas of the parameter space of the 2HDM Type-I that are still allowed by Large Hadron Collider (LHC) and other experimental data as well as theoretical constraints. We suggest that
H
±
→
W
±
h
and/or
H
±
→
W
±
A
could be used as a feasible discovery channel alternative to
H
±
→
τ
ν
.
A
bstract
The
A
→
Z
(*)
h
decay signature has been highlighted as possibly being the first testable probe of the Standard Model (SM) Higgs boson discovered in 2012 (
h
) interacting with Higgs ...companion states, such as those existing in a 2-Higgs Doublet Model (2HDM), chiefly, a CP-odd one (
A
). The production mechanism of the latter at the Large Hadron Collider (LHC) takes place via
b
b
¯
-annihilation and/or
gg
-fusion, depending on the 2HDM parameters, in turn dictated by the Yukawa structure of this Beyond the SM (BSM) scenario. Among the possible incarnations of the 2HDM, we test here the so-called Type-II, for a twofold reason. On the one hand, it intriguingly offers two very distinct parameter regions compliant with the SM-like Higgs measurements, i.e., where the so-called ‘SM limit’ of the 2HDM can be achieved. On the other hand, in both configurations, the
AZh
coupling is generally small, hence the signal is strongly polluted by backgrounds, so that the exploitation of Machine Learning (ML) techniques becomes extremely useful. In this paper, we show that the application of advanced ML implementations can be decisive in establishing such a signal. This is true for all distinctive kinematical configurations involving the
A → Z
(*)
h
decay, i.e., below threshold (
m
A
<
m
Z
+
m
h
), at its maximum (
m
Z
+
m
h
<
m
A
< 2
m
t
) and near the onset of
t
t
¯
pair production (
m
A
≈ 2
m
t
), for which we propose Benchmark Points (BPs) for future phenomenological analyses.
The detection of a heavy neutral CP-even Higgs boson of the
B
-
L
Supersymmetric Standard Model (BLSSM),
h
′
, with
m
h
′
≃
400
GeV
, at the Large Hadron Collider (LHC) for a center-of-mass energy of
...s
=
14
TeV
, is investigated. The following production and decay channels are considered:
g
g
→
h
′
→
ZZ
→
4
ℓ
and
(with
being the Missing Transverse Energy (MET)), where
ℓ
=
e
,
μ
, with integrated luminosity
L
int
=
300
fb
-
1
(Run 3). Furthermore, we also look into the di-Higgs channel
g
g
→
h
′
→
hh
→
b
b
¯
γ
γ
at the High-Luminosity LHC (HL-LHC) with an integrated luminosity of
L
int
=
3000
fb
-
1
. We demonstrate that promising signals with high signal-to-background statistical significance (
S
/
B
) can be obtained through the three aforementioned channels.
We show how, in the B−L extension of the SM (BLSM) with an Inverse Seesaw (IS) mechanism for neutrino mass generation, a light Z′ state with moderate couplings to SM objects, hence ‘dark’ in its ...nature, can be associated, in conjunction with light sterile neutrinos, to some present day data anomalies, such as the anomalous magnetic moment of the muon as well as a possible signal indicating the existence of sterile neutrinos in neutrino beam experiments.
We present a reinterpretation study of existing results from the CMS Collaboration, specifically, searches for light Beyond the Standard Model (BSM) Higgs pairs produced in the chain decay
p
p
→
H
SM
...→
h
h
(
a
a
)
into a variety of final states, in the context of the CP-conserving 2-Higgs Doublet Model (2HDM) Type-I. Through this, we test the Large Hadron Collider (LHC) sensitivity to a possible new signature,
p
p
→
H
SM
→
Z
A
→
Z
Z
h
, with
Z
Z
→
j
j
μ
+
μ
-
and
h
→
b
b
¯
. We perform a systematic scan over the 2HDM Type-I parameter space, by taking into account all available theoretical and experimental constraints, in order to find a region with a potentially visible signal. We investigate the significance of it through a full Monte Carlo simulation down to the parametrised detector level. We show that such a signal is an alternative promising channel to standard four-body searches for light BSM Higgs bosons at the LHC already with an integrated luminosity of
L
=
300
fb
-
1
. For a tenfold increase of the latter, discovery should be possible over most of the allowed parameter space.
Motivated by results recently reported by the CMS Collaboration about an excess in the di-photon spectrum at about 96 GeV, especially when combined with another long-standing anomaly at the same ...value in the bb¯ invariant mass spectrum in four-jet events collected at LEP, we show that a possible explanation to both phenomena can be found at 1σ level in a generic 2-Higgs Doublet Model (2HDM) of Type-III in presence of a specific Yukawa texture, wherein Lepton Flavour Violating (LFV) (neutral) currents are induced at tree level. Bounds from Higgs data play a major role in limiting the parameter space of this scenario, yet we find solutions with mH=125 GeV and mh=96 GeV consistent with current theoretical and experimental bounds.
A
bstract
In scenarios beyond the Standard Model (BSM) characterised by charged (
W
′) or neutral (
Z
′) massive gauge bosons with large width, resonant mass searches are not very effective, so that ...one has to exploit the tails of the mass distributions measured at the Large Hadron Collider (LHC). In this case, the LHC sensitivity to new physics signals is influenced significantly by systematic uncertainties associated with the Parton Distribution Functions (PDF), particularly in the valence quark sector relevant for the multi-TeV mass region. As a BSM framework featuring such conditions, we consider the 4-Dimensional Composite Higgs Model (4DCHM), in which multiple
W
′ and
Z
′ broad resonances are present, with strongly correlated properties. By using the QCD tool xFitter, we study the implications on
W
′ and
Z
′ searches in Drell-Yan (DY) lepton decay channels that follow from the reduction of PDF uncertainties obtained through combining high-statistics precision measurements of DY lepton-charge and forward-backward asymmetries. We find that the sensitivity to the BSM states is greatly increased with respect to the case of base PDF sets, thereby enabling one to set more stringent limits on (or indeed discover) such new particles, both independently and in correlated searches.
PDF
