We consider an extension of the standard model (SM) with an inert Higgs doublet and three Majorana singlet fermions to address both origin and the smallness of neutrino masses and dark matter (DM) ...problems. In this setup, the lightest Majorana singlet fermion plays the role of DM candidate and the model parameter space can be accommodated to avoid different experimental constraints such as lepton flavor violating processes and electroweak precision tests. The neutrino mass is generated at one-loop level a la Scotogenic model and its smallness is ensured by the degeneracy between the CP-odd and CP-even scalar members of the inert doublet. Interesting signatures at both leptonic and hadronic colliders are discussed.
A
bstract
We suggest a minimal model for GeV-scale Majorana Dark Matter (DM) coupled to the standard model lepton sector via a charged scalar singlet. We show that there is an anti-correlation ...between the spin-independent DM-Nucleus scattering cross section (
σ
SI
) and the DM relic density for parameters values allowed by various theoretical and experimental constraints. Moreover, we find that even when DM couplings are of order unity,
σ
SI
is below the current experimental bound but above the neutrino floor. Furthermore, we show that the considered model can be probed at high energy lepton colliders using e.g. the mono-Higgs production and same-sign charged Higgs pair production.
A
bstract
We analyse scalar leptoquark pair production at the LHC with predictions including
t
-channel lepton exchange contributions up to next-to-leading order (NLO) in QCD. In particular, we ...calculate NLO-QCD predictions for off-diagonal production channels, i.e. channels that involve two different leptoquark eigenstates and are driven solely by diagrams involving Standard Model leptons in the
t
-channel at leading order, as opposed to diagonal channels where a pair of the same leptoquark eigenstate is produced. We find that reliable theoretical predictions for both channels require NLO accuracy. The relative importance of the off-diagonal modes depends strongly on the considered scenario. In a generic model involving
R
2
and
S
3
leptoquarks, at large values of the Yukawa couplings off-diagonal contributions initiated by valence quarks can be up to an order of magnitude higher than the diagonal production. However, we also find that in phenomenologically viable scenarios addressing the flavour anomalies off-diagonal production is generally negligible, with a few exceptions of 10%–30% of the total rate depending on the treatment of the charm density in the proton.
In this letter, we propose an extension of the scotogenic model where singlet Majorana particle can be dark matter (DM) without the need of a highly suppressed scalar coupling of the order O(10−10). ...For that, the SM is extended with three singlet Majorana fermions, an inert scalar doublet, and two (a complex and a real) singlet scalars, with a global Z4 symmetry that is spontaneously broken into Z2 at a scale higher than the electroweak one by the vev of the complex singlet scalar. In this setup, the smallness of neutrino mass is achieved via the cancellation between three diagrams a la scotogenic, a DM candidate that is viable for a large mass range; and the phenomenology is richer than the minimal scotogenic model.
The measurement of the Higgs quartic coupling modifier between a Higgs boson pair and a vector boson pair, κ2V, is expected to be achieved from vector-boson fusion (VBF) production of a Higgs boson ...pair. However, this process involves another unmeasured parameter, the trilinear Higgs self-coupling modifier κλ. A sensitivity analysis should target both parameters. Since the LHC cannot avoid the gluon fusion pollution, which becomes severe for non-SM κλ, an electron-proton collider is more appropriate for the comprehensive measurement. In this regard, we study the VBF production of a Higgs boson pair in the bb¯bb¯ final state at the LHeC and FCC-he. Performing detailed analysis using simulated dataset, we devise the search strategy specialized at the LHeC and FCC-he and give a prediction for the sensitivity to both κ2V and κλ. We find that the two electron-proton colliders have high potential: the LHeC has similar exclusion prospects as the HL-LHC; the FCC-he is extremely efficient, excluding the parameter space outside κ2V∈0.8,1.2 and κλ∈1,2.5 at 95% C.L. for the total luminosity of 10 ab−1 and 10% uncertainty on the background yields.
A
bstract
We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs ...couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and
e
+
e
−
Linear Collider machines, accurate theoretical predictions are required. We study the radiative corrections to the triple Higgs coupling
hhh
and to
hZZ
,
hW W
couplings in the context of the IHDM. By combining several theoretical and experimental constraints on parameter space, we show that extra particles might modify the triple Higgs coupling near threshold regions. Finally, we discuss the effect of these corrections on the double Higgs production signal at the
e
+
e
−
LC and show that they can be rather important.
A
bstract
In dark-matter annihilation channels to hadronic final states, stable particles — such as positrons, photons, antiprotons, and antineutrinos — are produced via complex sequences of ...phenomena including QED/QCD radiation, hadronisation, and hadron decays. These processes are normally modelled by Monte Carlo (MC) event generators whose limited accuracy imply intrinsic QCD uncertainties on the predictions for indirect-detection experiments like F
ermi
-LAT, P
amela
, I
ce
C
ube
or A
ms
–02. In this article, we perform a comprehensive analysis of QCD uncertainties, meaning both perturbative and nonperturbative sources of uncertainty are included — estimated via variations of MC renormalization-scale and fragmentation-function parameters, respectively — in antimatter spectra from dark-matter annihilation, based on parametric variations of the P
ythia
8 event generator. After performing several retunings of light-quark fragmentation functions, we define a set of variations that span a conservative estimate of the QCD uncertainties. We estimate the effects on antimatter spectra for various annihilation channels and final-state particle species, and discuss their impact on fitted values for the dark-matter mass and thermally-averaged annihilation cross section. We find dramatic impacts which can go up to
O
(40) GeV for uncertainties on the dark-matter mass and up to
O
(10%) for the annihilation cross section. We provide the spectra in tabulated form including QCD uncertainties and code snippets to perform fast dark-matter fits, in this github repository.
A
bstract
We explore the potential of the Large Hadron Collider (LHC) in detecting a signal originating from the production of a heavy SU(2)
R
charged gauge boson that then decays into a top-bottom ...quark pair via the mediation of a right-handed neutrino,
pp
→
W
R
→
N
R
ℓ
→ (
ℓ
′
tb
)
ℓ
. Such a channel, that we study in the context of the minimal Left-Right Symmetric Model, contrasts with conventional smoking-gun signatures targeted experimentally and phenomenologically in which only light quarks are involved. We propose a selection strategy aimed at extracting such a top-bottom signal and we estimate the resulting sensitivity of the LHC to the model. Our results demonstrate the potential impact of such a search and we therefore urge the experimental collaborations to carry out a similar analysis in the light of present and future data.
Motivated by the recent galactic center gamma-ray excess identified in the Fermi-LAT data, we perform a detailed study of QCD fragmentation uncertainties in the modeling of the energy spectra of ...gamma-rays from Dark-Matter (DM) annihilation. When Dark-Matter particles annihilate to coloured final states, either directly or via decays such as W(*) q ′, photons are produced from a complex sequence of shower, hadronisation and hadron decays. In phenomenological studies their energy spectra are typically computed using Monte Carlo event generators. These results have however intrinsic uncertainties due to the specific model used and the choice of model parameters, which are difficult to asses and which are typically neglected. We derive a new set of hadronisation parameters (tunes) for the PYTHIA 8.2 Monte Carlo generator from a fit to LEP and SLD data at the Z peak. For the first time we also derive a conservative set of uncertainties on the shower and hadronisation model parameters. Their impact on the gamma-ray energy spectra is evaluated and discussed for a range of DM masses and annihilation channels. The spectra and their uncertainties are also provided in tabulated form for future use. The fragmentation-parameter uncertainties may be useful for collider studies as well.
We study the sensitivity of certain observables to the anomalous right tensorial coupling in single top production at the LHC at s=13 TeV. The observables consist of asymmetries constructed from the ...energy and angles of the decay products of the top quark produced in single top production through the t-channel. The computation is done at leading order (LO) and next-to-leading order (NLO) in the strong coupling in the five-flavor scheme. We have estimated projected limits on the anomalous coupling, both at the parton level without cuts and at the particle level with cuts. We find that the asymmetries are robust with respect to the higher-order QCD corrections and are indeed a very good probe of this anomalous coupling of the top. Hence, they can be used as experimental probes of the same.
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