scholarly journals Light Higgs searches in $$ t\overline{t}\phi $$ production at the LHC

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Duarte Azevedo ◽  
Rodrigo Capucha ◽  
Emanuel Gouveia ◽  
António Onofre ◽  
Rui Santos
Keyword(s):  
Top Quark ◽  
Mass Range ◽  
Higgs Doublet ◽  
Mass Region ◽  
Reconstruction Method ◽  
Arbitrary Mass ◽  
Quark Pairs ◽  
Yukawa Couplings ◽  
Low Mass ◽  
Mass Reconstruction

Abstract In this paper we propose a new reconstruction method to explore the low mass region in the associated production of top-quark pairs ($$ t\overline{t} $$ t t ¯ ) with a generic scalar boson (ϕ) at the LHC. The new method of mass reconstruction shows an improved resolution of at least a factor of two in the low mass region when compared to previous methods, without the loss of sensitivity of previous analyses. It turns out that it also leads to an improvement of the mass reconstruction of the 125 GeV Higgs for the same production process. We use an effective Lagrangian to describe a scalar with a generic Yukawa coupling to the top quarks. A full phenomenological analysis was performed, using Standard Model background and signal events generated with MadGraph5_aMC@NLO and reconstructed using a kinematic fit. The use of CP-sensitive variables allows then to maximize the distinction between CP-even and CP-odd components of the Yukawa couplings. Confidence Levels (CLs) for the exclusion of ϕ bosons with mixed CP (both CP-even and CP-odd components) were determined as a function of the top Yukawa couplings to the ϕ boson. The mass range analysed starts slightly above the ϒΥ mass up to 40 GeV, although the analysis can be used for an arbitrary mass. If no new light scalar is found, exclusion limits at 95% CL for the absolute value of the CP-even and CP-odd Yukawa are derived. Finally, we analyse how these limits constrain the parameter space of the complex two-Higgs doublet model (C2HDM).

scholarly journals Constraints to Dark Matter from Inert Higgs Doublet Model

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Marco Aurelio Díaz ◽  
Benjamin Koch ◽  
Sebastián Urrutia-Quiroga
Keyword(s):  
Dark Matter ◽  
Higgs Doublet ◽  
Mass Region ◽  
Missing Energy ◽  
Energy Channel ◽  
Dark Matter Relic Density ◽  
Low Mass ◽  
Doublet Model ◽  
Two Jets ◽  
Matter Detection

We study the Inert Higgs Doublet Model and its inert scalar HiggsHas the only source for dark matter. It is found that three mass regions of the inert scalar Higgs can give the correct dark matter relic density. The low mass region (between 3 and 50 GeV) is ruled out. New direct dark matter detection experiments will probe the intermediate (between 60 and 100 GeV) and high (heavier than 550 GeV) mass regions. Collider experiments are advised to search forD±→HW±decay in the two jets plus missing energy channel.

scholarly journals Searches for low-mass dimuon resonances

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
R. Aaij ◽  
◽  
C. Abellán Beteta ◽  
T. Ackernley ◽  
B. Adeva ◽  
...  
Keyword(s):  
Cross Sections ◽  
Center Of Mass ◽  
Mass Range ◽  
Higgs Doublet ◽  
Proton Collision ◽  
Proton Proton ◽  
Center Of Mass Energy ◽  
Lhcb Detector ◽  
Low Mass ◽  
Proton Proton Collision

Abstract Searches are performed for a low-mass dimuon resonance, X, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data sample corresponding to an integrated luminosity of 5.1 fb−1 and collected with the LHCb detector. The X bosons can either decay promptly or displaced from the proton-proton collision, where in both cases the requirements placed on the event and the assumptions made about the production mechanisms are kept as minimal as possible. The searches for promptly decaying X bosons explore the mass range from near the dimuon threshold up to 60 GeV, with nonnegligible X widths considered above 20 GeV. The searches for displaced X → μ+μ− decays consider masses up to 3 GeV. None of the searches finds evidence for a signal and 90% confidence-level exclusion limits are placed on the X → μ+μ− cross sections, each with minimal model dependence. In addition, these results are used to place world-leading constraints on GeV-scale bosons in the two-Higgs-doublet and hidden-valley scenarios.

scholarly journals Constraints on coloured scalars from global fits

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Otto Eberhardt ◽  
Víctor Miralles ◽  
Antonio Pich
Keyword(s):  
Top Quark ◽  
Scalar Potential ◽  
Higgs Doublet ◽  
Model Parameters ◽  
Simple Extension ◽  
Minimal Flavour Violation ◽  
Yukawa Couplings ◽  
Flavour Violation ◽  
The One ◽  
Potential Parameters

Abstract We consider a simple extension of the electroweak theory, incorporating one SU(2)L doublet of colour-octet scalars with Yukawa couplings satisfying the principle of minimal flavour violation. Using the HEPfit package, we perform a global fit to the available data, including all relevant theoretical constraints, and extract the current bounds on the model parameters. Coloured scalars with masses below 1.05 TeV are already excluded, provided they are not fermiophobic. The mass splittings among the different (charged and CP-even and CP-odd neutral) scalars are restricted to be smaller than 20 GeV. Moreover, for scalar masses smaller than 1.5 TeV, the Yukawa coupling of the coloured scalar multiplet to the top quark cannot exceed the one of the SM Higgs doublet by more than 80%. These conclusions are quite generic and apply in more general frameworks (without fine tunings). The theoretical requirements of perturbative unitarity and vacuum stability enforce relevant constraints on the quartic scalar potential parameters that are not yet experimentally tested.

scholarly journals The muon g – 2 for low-mass pseudoscalar Higgs in the general 2HDM

2018 ◽  
Vol 179 ◽  
pp. 01022
Author(s):  
Adriano Cherchiglia ◽  
Dominik Stöckinger ◽  
Hyejung Stöckinger-Kim
Keyword(s):  
Large Deviation ◽  
Higgs Doublet ◽  
Type Ii ◽  
Parameter Region ◽  
Yukawa Couplings ◽  
The Standard Model ◽  
Low Mass ◽  
Doublet Model ◽  
Two Higgs Doublet Model ◽  
Theory And Experiment

The two-Higgs doublet model is a simple and attractive extension of the Standard Model. It provides a possibility to explain the large deviation between theory and experiment in the muon g – 2 in an interesting parameter region: light pseudoscalar Higgs A, large Yukawa coupling to τ-leptons, and general, non-type II Yukawa couplings are preferred. This parameter region is explored, experimental limits on the relevant Yukawa couplings are obtained, and the maximum possible contributions to the muon g – 2 are discussed.

scholarly journals ON THE TWO-LOOP DECOUPLING CORRECTIONS TO τ-LEPTON AND b-QUARK RUNNING MASSES IN THE MSSM

2010 ◽  
Vol 25 (12) ◽  
pp. 2437-2456 ◽  
Author(s):  
A. V. BEDNYAKOV
Keyword(s):  
Top Quark ◽  
Bottom Quark ◽  
Higgs Doublet ◽  
Effective Theory ◽  
Theory Approach ◽  
Supersymmetric Extension ◽  
Yukawa Couplings ◽  
Quantum Numbers ◽  
Fermion Masses ◽  
B Quark

Masses of heavy Standard Model (SM) fermions (top-quark, bottom-quark and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and τ-lepton have the same quantum numbers with respect to SU(2) group and in the MSSM acquire their masses due to interactions with the same Higgs doublet. As a consequence, for large values of tan β parameter corresponding Yukawa couplings also become large and together with tan β can significantly enhance radiative corrections. In the case of b-quark two-loop [Formula: see text] contribution to the relation between running bottom-quark mass in QCD and MSSM is known in literature. This paper is devoted to calculation of the NNLO corrections proportional to Yukawa couplings. For the τ-lepton obtained contribution can be considered as a good approximation to the full two-loop result. For the b-quark numerical analysis given in the paper shows that only the sum of strong and Yukawa corrections can play such a role.

scholarly journals Light charged Higgs boson scenario in 3-Higgs doublet models

2017 ◽  
Vol 32 (23n24) ◽  
pp. 1750145 ◽  
Author(s):  
A. G. Akeroyd ◽  
Stefano Moretti ◽  
Kei Yagyu ◽  
Emine Yildirim
Keyword(s):  
Higgs Boson ◽  
Top Quark ◽  
Vacuum Expectation ◽  
Higgs Doublet ◽  
Charged Higgs Boson ◽  
Higgs Bosons ◽  
Tree Level ◽  
Yukawa Couplings ◽  
Charged Higgs ◽  
Charged Higgs Bosons

The constraints from the measurements of the [Formula: see text] decay rate on the parameter space of 3-Higgs Doublet Models (3HDMs), where all the doublets have nonzero vacuum expectation values, are studied at the next-to-leading order in QCD. In order to naturally avoid the presence of flavour changing neutral currents at the tree level, we impose two softly-broken discrete [Formula: see text] symmetries. This gives rise to five independent types of 3HDMs that differ in their Yukawa couplings. We show that in all these 3HDMs (including the case of type-II-like Yukawa interactions) both masses of the two charged Higgs bosons [Formula: see text] and [Formula: see text] can be smaller than the top mass [Formula: see text] while complying with the constraints from [Formula: see text]. As an interesting phenomenological consequence, the branching ratios of the charged Higgs bosons decay into the [Formula: see text] final states can be as large as [Formula: see text] when their masses are taken to be below [Formula: see text] in two of the five 3HDMs (named as Type-Y and Type-Z). This light charged Higgs boson scenario provides a hallmark 3HDM signature that cannot be realised in [Formula: see text] symmetric 2-Higgs doublet models. We find that in the Type-Y and Type-Z 3HDMs the scenario with [Formula: see text], [Formula: see text] is ruled out by the direct searches at the LHC, but in the Type-Y 3HDM [Formula: see text] and [Formula: see text] is allowed by [Formula: see text] and direct searches at LEP2, Tevatron and LHC due to the reduced sensitivity of these searches to the degenerate case [Formula: see text]. The cases where only one or both charged Higgs bosons are above the top quark mass are also naturally allowed in the both Type-Y and Type-Z 3HDMs.

scholarly journals Detection capability of Migdal effect for argon and xenon nuclei with position sensitive gaseous detectors

2020 ◽  
Author(s):  
Kiseki D Nakamura ◽  
Kentaro Miuchi ◽  
Shingo Kazama ◽  
Yutaro Shoji ◽  
Masahiro Ibe ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Experimental Approach ◽  
Isotope Separation ◽  
Mass Region ◽  
Background Rate ◽  
Argon Gas ◽  
Low Mass ◽  
Position Sensitive ◽  
Set Up ◽  
Direct Dark Matter

Abstract Migdal effect is attracting interests because of the potential to enhance the sensitivities of direct dark matter searches to the low mass region. In spite of its great importance, the Migdal effect has not been experimentally observed yet. A realistic experimental approach towards the first observation of the Migdal effect in the neutron scattering was studied with Monte Carlo simulations. In this study, potential background rate was studied together with the event rate of the Migdal effect by a neutron source. It was found that a table-top sized ~ (30cm)3 position-sensitive gaseous detector filled with argon or xenon target gas can detect characteristic signatures of the Migdal effect with sufficient rates (O(102 ~ 103) events/day). A simulation result of a simple experimental set-up showed two significant background sources, namely the intrinsic neutrons and the neutron induced gamma-rays. It is found that the intrinsic neutron background rate for the argon gas is acceptable level and some future study for the reduction of the gamma-rays from the laboratory would make the observation of the Migdal effect possible. The background for the xenon gas, on the other hand, is found to be much more serious than for the argon gas. Future works on the isotope separation as well as the reduction of the gamma-rays from the detector and laboratory will be needed before the Migdal effect observation for xenon gas case.

scholarly journals Neutrino masses, vacuum stability and quantum gravity prediction for the mass of the top quark

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Guillem Domènech ◽  
Mark Goodsell ◽  
Christof Wetterich
Keyword(s):  
Quantum Gravity ◽  
Top Quark ◽  
Quark Mass ◽  
Scalar Potential ◽  
Planck Scale ◽  
Neutrino Masses ◽  
Top Quark Mass ◽  
Vacuum Stability ◽  
Intermediate Scale ◽  
Yukawa Couplings

Abstract A general prediction from asymptotically safe quantum gravity is the approximate vanishing of all quartic scalar couplings at the UV fixed point beyond the Planck scale. A vanishing Higgs doublet quartic coupling near the Planck scale translates into a prediction for the ratio between the mass of the Higgs boson MH and the top quark Mt. If only the standard model particles contribute to the running of couplings below the Planck mass, the observed MH∼ 125 GeV results in the prediction for the top quark mass Mt∼ 171 GeV, in agreement with recent measurements. In this work, we study how the asymptotic safety prediction for the top quark mass is affected by possible physics at an intermediate scale. We investigate the effect of an SU(2) triplet scalar and right-handed neutrinos, needed to explain the tiny mass of left-handed neutrinos. For pure seesaw II, with no or very heavy right handed neutrinos, the top mass can increase to Mt ∼ 172.5 GeV for a triplet mass of M∆ ∼ 108GeV. Right handed neutrino masses at an intermediate scale increase the uncertainty of the predictions of Mt due to unknown Yukawa couplings of the right-handed neutrinos and a cubic interaction in the scalar potential. For an appropriate range of Yukawa couplings there is no longer an issue of vacuum stability.

scholarly journals Small Mass but Strong Information: Diagnostic Ions Provide Crucial Clues to Correctly Identify Histone Lysine Modifications

Proteomes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Alaa Hseiky ◽  
Marion Crespo ◽  
Sylvie Kieffer-Jaquinod ◽  
François Fenaille ◽  
Delphine Pflieger
Keyword(s):  
Amino Acid ◽  
Small Mass ◽  
Mass Region ◽  
Amino Acid Sequences ◽  
Lysine Modification ◽  
Lysine Residues ◽  
Two Factors ◽  
Low Mass ◽  
Diagnostic Ions

(1) Background: The proteomic analysis of histones constitutes a delicate task due to the combination of two factors: slight variations in the amino acid sequences of variants and the multiplicity of post-translational modifications (PTMs), particularly those occurring on lysine residues. (2) Methods: To dissect the relationship between both aspects, we carefully evaluated PTM identification on lysine 27 from histone H3 (H3K27) and the artefactual chemical modifications that may lead to erroneous PTM determination. H3K27 is a particularly interesting example because it can bear a range of PTMs and it sits nearby residues 29 and 31 that vary between H3 sequence variants. We discuss how the retention times, neutral losses and immonium/diagnostic ions observed in the MS/MS spectra of peptides bearing modified lysines detectable in the low-mass region might help validate the identification of modified sequences. (3) Results: Diagnostic ions carry key information, thereby avoiding potential mis-identifications due to either isobaric PTM combinations or isobaric amino acid-PTM combinations. This also includes cases where chemical formylation or acetylation of peptide N-termini artefactually occurs during sample processing or simply in the timeframe of LC-MS/MS analysis. Finally, in the very subtle case of positional isomers possibly corresponding to a given mass of lysine modification, the immonium and diagnostic ions may allow the identification of the in vivo structure.

scholarly journals Invariant-mass distribution of top-quark pairs and top-quark mass determination

2020 ◽  
Vol 44 (9) ◽  
pp. 091001
Author(s):  
Wan-Li Ju ◽  
Guoxing Wang ◽  
Xing Wang ◽  
Xiaofeng Xu ◽  
Yongqi Xu ◽  
...  
Keyword(s):  
Invariant Mass ◽  
Mass Distribution ◽  
Top Quark ◽  
Quark Mass ◽  
Invariant Mass Distribution ◽  
Mass Determination ◽  
Top Quark Mass ◽  
Quark Pairs ◽  
Top Quark Pairs
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