NON-STANDARD HIGGS BOSON AND THE DECAY KL→π0l+l−

1988 ◽  
Vol 03 (17) ◽  
pp. 1677-1682 ◽  
Author(s):  
M.I. DOBROLIUBOV ◽  
A. YU. IGNATIEV
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
Upper Bounds ◽  
The Standard Model

We investigate various mechanisms of enhancement of the branching ratios of the decay KL→π0l+l− as compared to the predictions of the Standard Model. We propose a model with several Higgs doublets, which contains a Higgs boson with nearly equal couplings to e+e− and µ+µ− pairs. In this model, the branching ratio BR (KL→π0e+e−, π0µ+µ−) can be close to the present experimental upper bounds.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

scholarly journals Higgs boson production cross-section measurements and their EFT interpretation in the $$4\ell $$ decay channel at $$\sqrt{s}=$$13 TeV with the ATLAS detector

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Cross Section ◽  
Decay Channel ◽  
Branching Ratio ◽  
Proton Collision ◽  
Boson Production ◽  
Theory Approach ◽  
Higgs Boson Production ◽  
The Standard Model

AbstractHiggs boson properties are studied in the four-lepton decay channel (where lepton = e, $$\mu $$ μ ) using 139 $$\hbox {fb}^{-1}$$ fb - 1 of proton–proton collision data recorded at $$\sqrt{s}=$$ s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio for $$H\rightarrow ZZ^*$$ H → Z Z ∗ decay is measured to be $$1.34 \pm 0.12$$ 1.34 ± 0.12  pb for a Higgs boson with absolute rapidity below 2.5, in good agreement with the Standard Model prediction of $$1.33 \pm 0.08$$ 1.33 ± 0.08  pb. Cross-sections times branching ratio are measured for the main Higgs boson production modes in several exclusive phase-space regions. The measurements are interpreted in terms of coupling modifiers and of the tensor structure of Higgs boson interactions using an effective field theory approach. Exclusion limits are set on the CP-even and CP-odd ‘beyond the Standard Model’ couplings of the Higgs boson to vector bosons, gluons and top quarks.

scholarly journals Lepton-flavor-violating decays of the SM-like Higgs boson $h\rightarrow e_ie_j$, and $e_i \rightarrow e_j\, \gamma $ in a flipped 3-3-1 model

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
T T Hong ◽  
H T Hung ◽  
H H Phuong ◽  
L T T Phuong ◽  
L T Hue
Keyword(s):  
Higgs Boson ◽  
Branching Ratio ◽  
High Energy ◽  
Branching Ratios ◽  
The Other ◽  
Experimental Limit ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Charged Leptons ◽  
O 10

Abstract In the framework of the flipped 3-3-1 model introduced recently [R. M. Fonseca and M. Hirsch, J. High Energy Phys. 1608, 003 (2016)], the lepton-flavor-violating (LFV) decay $\mu \rightarrow 3e$ was predicted to have a large branching ratio (Br) close to the recent experimental limit. We will show that the Br of LFV decays of the standard-model-like (SM-like) Higgs boson decays (LFVHD) Br$(h\rightarrow e_ae_b)$ may also be large. Namely, Br$(h\rightarrow \mu\tau,e\tau)$ can reach values of $\mathcal{O}(10^{-4}){-}\mathcal{O}(10^{-5})$, which will reach the upcoming experimental sensitivities. On the other hand, for LFV decays of charged leptons (cLFV) $(e_b\rightarrow e_a\gamma)$, the branching ratios are well below experimental bounds.

B anomalies with unparticles

2021 ◽  
Vol 36 (30) ◽  
Author(s):  
Jong-Phil Lee
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
The Standard Model ◽  
Model Predictions ◽  
Best Fit

We analyze the [Formula: see text] anomalies associated with the [Formula: see text] decays in the unparticle model. The fraction of the branching ratios [Formula: see text] and other parameters related to the polarization are fitted to the experimental data by minimizing [Formula: see text]. The best-fit values are [Formula: see text] and [Formula: see text] which are still larger than the standard model predictions. We find that our results safely render the branching ratio [Formula: see text] below [Formula: see text].

scholarly journals Study of Bs0 → ℓ+ℓ−γ decays in a nonuniversal Z′ model

2019 ◽  
Vol 34 (09) ◽  
pp. 1950048 ◽  
Author(s):  
D. Banerjee ◽  
M. Kumar ◽  
P. Nayek ◽  
S. Sahoo
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
Branching Ratio ◽  
Branching Ratios ◽  
Flavor Changing ◽  
The Standard Model ◽  
Flavor Changing Neutral Current ◽  
Coupling Parameters ◽  
Text Model ◽  
Boson Coupling

We investigate [Formula: see text] decays in a nonuniversal [Formula: see text] model derived from the extension of the Standard Model (SM). Considering the [Formula: see text]-mediated flavor-changing neutral current (FCNC) effects, we calculate the branching ratio and forward–backward asymmetry [Formula: see text] for [Formula: see text] decay processes. We compare the obtained results with predictions of the SM and discuss the sensitivity of the observables to [Formula: see text] boson coupling parameters. We find that the branching ratios are enhanced by one order from SM predictions in [Formula: see text] model scenario. We also observe that the variation of forward–backward asymmetry with the [Formula: see text] boson coupling parameters portrays discrimination between NP effects and SM results.

The QCD corrections of the process h → ηbZ

2018 ◽  
Vol 33 (15) ◽  
pp. 1830008
Author(s):  
Rong-Fei Zhu ◽  
Tai-Fu Feng ◽  
Hai-Bin Zhang
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Quantum Chromodynamics ◽  
Branching Ratio ◽  
Tree Level ◽  
Relative Correction ◽  
Loop Level ◽  
The Standard Model ◽  
Key Parameter

We investigate the 125 GeV Higgs boson decay to a pseudoscalar quarkonium [Formula: see text] and [Formula: see text] boson. We calculate the quantum chromodynamics (QCD) one-loop corrections to the branching ratio of the process, [Formula: see text], both in the Standard Model (SM) and in the two Higgs double models (THDM). Adding the QCD one-loop corrections, the branching ratio of [Formula: see text] in the SM is [Formula: see text]. The relative correction of that QCD one-loop level relative to the tree level of [Formula: see text] is around 76% in the SM. Similarly, the relative correction in the THDM also can be around 75%. The key parameter, [Formula: see text], can affect the relative correction in the THDM.

scholarly journals DIMINISHED UPPER BOUNDS ON THE UNIFICATION MASS SCALES FOR HEAVY HIGGS BOSON MASSES

2006 ◽  
Vol 21 (03) ◽  
pp. 209-212
Author(s):  
V. ELIAS ◽  
S. HOMAYOUNI ◽  
D. J. JEFFREY
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Higgs Sector ◽  
Upper Bounds ◽  
Higher Order ◽  
Scalar Coupling ◽  
Scalar Couplings ◽  
The Standard Model ◽  
Β Function ◽  
Heavy Higgs Boson

We consider dominant three-, four- and five-loop contributions to λ, the quartic scalar coupling-constant's β-function in the Standard Model. We find that these terms accelerate the evolution of λ to nonperturbative values, thereby lowering the unification bound for which scalar-couplings are still perturbative. We also find that these higher order contributions imply a substantial lowering of λ itself before the anticipated onset of nonperturbative physics in the Higgs sector.

Search for New Particles Decaying into $b \bar{b}$ Associated with W± Bosons at Tevatron

2005 ◽  
Vol 20 (15) ◽  
pp. 3294-3296
Author(s):  
◽  
Yoshio Ishizawa
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Cross Section ◽  
Production Cross ◽  
W Bosons ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Upper Limit ◽  
The Standard Model ◽  
New Particles

We present searches for new particles decaying into [Formula: see text] and produced in association with W± bosons in [Formula: see text] collisions at [Formula: see text]. The searches focus on the Standard Model Higgs boson or Technicolor particle decaying into [Formula: see text] using approximately 162 pb-1 of the dataset accumulated by the Collider Detector at Fermilab. The number of events and mass distribution are consistent with the Standard Model expectations and we set a 95% confidence level upper limit on the production cross section times branching ratio as a function of the new particle mass.

scholarly journals FURTHER STUDIES OF HIGGS PROPERTIES AT AN ILC γγ COLLIDER

2013 ◽  
Vol 28 (18) ◽  
pp. 1350085 ◽  
Author(s):  
XIAO-GANG HE ◽  
SIAO-FONG LI ◽  
HSIU-HSIEN LIN
Keyword(s):  
Angular Distribution ◽  
Higgs Boson ◽  
Standard Model ◽  
Decay Mode ◽  
Branching Ratio ◽  
Current Data ◽  
Decay Modes ◽  
The Standard Model ◽  
Shell Production

Recently the ATLAS and CMS experiments at the LHC have found a Higgs-like boson h with a mass around 125 GeV from several decay modes. The decay mode h →γγ is one of the most important modes in studying whether h is actually the Standard Model (SM) Higgs boson. Current data indicate that h→γγ has a branching ratio larger than the SM prediction for h being identified as the SM Higgs boson. To decide whether the h discovered at the LHC is the SM Higgs boson, more data are needed. We study how γγ collider can help to provide some of the most important information about the Higgs boson properties. We show that a γγ collider can easily verify whether the enhanced h →γγ observed at the LHC hold. Different models can be tested by studying Higgs boson decay to γZ. Studying angular distribution of the γγ through on-shell production of h and its subsequent decays into a γγ pair can decide whether the Higgs-like boson h at the LHC is a spin-0 or a spin-2 boson.

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