scholarly journals O(αs) CORRECTIONS TO B→ Xse+e-DECAY IN THE 2HDM

2001 ◽  
Vol 16 (33) ◽  
pp. 2151-2167 ◽  
Author(s):  
G. K. YEGHIYAN
Keyword(s):  
Branching Ratio ◽  
Resonance Region ◽  
Higgs Doublet ◽  
New Physics ◽  
Energy Scale ◽  
Order Effects ◽  
Renormalization Scale ◽  
Dilepton Invariant Mass ◽  
The Standard Model ◽  
Higher Order Effects

O(αs) QCD corrections to the inclusive B→Xse+e-decay are investigated within the two-Higgs doublet extension of the standard model (2HDM). The analysis is performed in the so-called off-resonance region; the dependence of the obtained results on the choice of the renormalization scale is examined in details. It is shown that O(αs) corrections can suppress the B→Xse+e-decay width up to 1.5–3 times (depending on the choice of the dilepton invariant mass s and the low-energy scale μ). As a result, in the experimentally allowed range of the parameter space, the relations between the B→Xse+e-branching ratio and the new physics parameters are strongly affected. It is also found that though the renormalization scale dependence of the B→Xse+e-branching is significantly reduced, higher order effects in the perturbation theory can still be non-negligible.

scholarly journals Exploring the low $$\tan \beta $$ region of two Higgs doublet models at the LHC

2021 ◽  
Vol 81 (9) ◽  
Author(s):  
Wei Su ◽  
Martin White ◽  
Anthony G. Williams ◽  
Yongcheng Wu
Keyword(s):  
Higgs Mass ◽  
Branching Ratio ◽  
Higgs Doublet ◽  
Tree Level ◽  
Order Effects ◽  
Type I ◽  
Benchmark Point ◽  
Two Higgs Doublet Models ◽  
The Impact ◽  
Higher Order Effects

AbstractCurrent interpretations of the LHC results on two Higgs doublet models (2HDM) underestimate the sensitivity due to neglecting higher order effects. In this work, we revisit the impact of these effects using the current cross-section times branching ratio limits of the $$A\rightarrow hZ, H \rightarrow VV$$ A → h Z , H → V V and $$H\rightarrow hh$$ H → h h channels. With a degenerate heavy Higgs mass $$m_\varPhi $$ m Φ , we find that the LHC searches gain sensitivity to the small $$\tan \beta $$ tan β region after including loop corrections, even close to $$\cos (\beta -\alpha )=0$$ cos ( β - α ) = 0 which is not reachable at tree level for all types of 2HDM. For a benchmark point with $$m_\varPhi =300$$ m Φ = 300 GeV, $$\tan \beta <1.8(1.2)$$ tan β < 1.8 ( 1.2 ) can be probed for the Type-I(II) 2HDM model for $$\cos (\beta -\alpha )=0$$ cos ( β - α ) = 0 . When the deviation from $$\cos (\beta -\alpha )=0$$ cos ( β - α ) = 0 is larger, the region for which current searches have exclusion potential becomes larger.

scholarly journals Charged Higgs contribution on Bc → (Ds, Ds*) l+l−

2020 ◽  
Vol 2020 (5) ◽  
Author(s):  
P Maji ◽  
S Biswas ◽  
P Nayek ◽  
S Sahoo
Keyword(s):  
Branching Ratio ◽  
Form Factors ◽  
Higgs Doublet ◽  
New Physics ◽  
Model Parameters ◽  
Type I ◽  
The Standard Model ◽  
Charged Higgs ◽  
Lepton Polarization ◽  
Meson States

Abstract In this paper, we study rare semileptonic decays of the $B_c$ meson in the context of type-I, II, and III two Higgs doublet models. We follow the relativistic quark model for parameterizing the form factors used in matrix elements of weak transitions between the corresponding meson states. We investigate observables such as branching ratio, lepton polarization asymmetry, forward–backward asymmetry, etc. and analyze the dependence of these quantities on the model parameters. We have found that there is noticeable sensitivity to these observables for the charged Higgs boson, which may provide a powerful probe to the standard model and new physics beyond it.

scholarly journals DIRECT CP ASYMMETRY IN INCLUSIVE RARE B-DECAYS IN 2HDM

2001 ◽  
Vol 16 (23) ◽  
pp. 3805-3822 ◽  
Author(s):  
H. H. ASATRYAN ◽  
H. M. ASATRIAN ◽  
G. K. YEGHIYAN ◽  
G. K. SAVVIDY
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Renormalization Scale ◽  
Cp Asymmetry ◽  
Rate Asymmetry ◽  
The Standard Model ◽  
Model Predictions

The direct CP asymmetry in the inclusive B → Xdγ and B → Xde+e-decays is investigated in the two-Higgs doublet extension of the Standard Model (2HDM). The investigation is performed in the lowest nonvanishing order of the perturbation theory using the existing restrictions on the 2HDM parameters space. It is shown that the direct CP asymmetry in the B → Xdγ decay can deviate significantly from the Standard Model predictions. In the presence of only one source of CP violation (the CKM matrix weak phase) aCP(B → Xdγ) can have the sign opposite to that in the SM. The new source of CP violation can make |aCP(B → Xdγ)| arbitrary small (unlike the SM case) and hence unmeasurable. Quantitatively, the obtained results suffer from the uncertainty of the choice of renormalization scale. As for the B → Xde+e-rate asymmetry, its renormalization scale dependence in the lowest nonvanishing order does not allow to conclude if this quantity is efficient for testing new physics beyond the Standard Model.

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 NEW PHYSICS UPPER BOUND ON THE BRANCHING RATIO OF Bs → l+l-γ

2007 ◽  
Vol 22 (18) ◽  
pp. 1319-1328 ◽  
Author(s):  
ASHUTOSH KUMAR ALOK ◽  
S. UMA SANKAR
Keyword(s):  
Upper Bound ◽  
Axial Vector ◽  
Branching Ratio ◽  
New Physics ◽  
Large Contribution ◽  
Beyond The Standard Model ◽  
Standard Model Expectation ◽  
Model Expectation ◽  
The Standard Model ◽  
Large Enhancement

We consider the effect of new physics on the branching ratio of Bs → l+l-γ where l = e, μ. If the new physics is of the form scalar/pseudoscalar, then it makes no contribution to Bs → l+l-γ, unlike in the case of Bs → l+l-, where it can potentially make a very large contribution. If the new physics is in the form of vector/axial-vector operators, then the present data on B → (K, K*) l+l- does not allow a large enhancement for B(Bs → l+l- γ). If the new physics is in the form of tensor/pseudotensor operators, then the data on B → (K, K*) l+l- gives no useful constraint but the data on B → K* γ does. Here again, a large enhancement of B(Bs → l+l-γ), much beyond the Standard Model expectation, is not possible. Hence, we conclude that the present data on b → s transitions allow a large boost in B(Bs → l+l-) but not in B(Bs → l+l-γ).

scholarly journals Searching for new physics in charm radiative decays

2018 ◽  
Vol 33 (32) ◽  
pp. 1850194
Author(s):  
Aritra Biswas ◽  
Sanjoy Mandal ◽  
Nita Sinha
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Radiative Decays ◽  
Symmetric Model ◽  
Leading Order ◽  
Photon Polarization ◽  
Long Distance ◽  
The Standard Model ◽  
Distance Effects

We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for [Formula: see text] decay is enhanced by more than [Formula: see text] as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left–right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics in spite of the large long distance effects. We find that there is a large region within the allowed parameter space of the model with a vector-like quark and an additional left–right symmetry, where, the photon polarization can be dominantly right-handed.

scholarly journals Beyond $$M_{t\bar{t}}$$: learning to search for a broad $$t\bar{t}$$ resonance at the LHC

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Sunghoon Jung ◽  
Dongsub Lee ◽  
Ke-Pan Xie
Keyword(s):  
Invariant Mass ◽  
Common Knowledge ◽  
Resonance Region ◽  
Invariant Mass Spectrum ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Angular Correlations ◽  
Additional Information ◽  
The Standard Model ◽  
Learning Technique

Abstract A resonance peak in the invariant mass spectrum has been the main feature of a particle at collider experiments. However, broad resonances not exhibiting such a sharp peak are generically predicted in new physics models beyond the Standard Model. Without a peak, how do we discover a broad resonance at colliders? We use machine learning technique to explore answers beyond common knowledge. We learn that, by applying deep neural network to the case of a $$t\bar{t}$$tt¯ resonance, the invariant mass $$M_{t\bar{t}}$$Mtt¯ is still useful, but additional information from off-resonance region, angular correlations, $$p_T$$pT, and top jet mass are also significantly important. As a result, the improved LHC sensitivities do not depend strongly on the width. The results may also imply that the additional information can be used to improve narrow-resonance searches too. Further, we also detail how we assess machine-learned information.

Study of the semileptonic Bc → ηcτ−v̄τ decay in W′ model

2021 ◽  
Author(s):  
S. Mahata ◽  
P. Maji ◽  
S. Biswas ◽  
S. Sahoo
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Experimental Results ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Text Model

Recently, many discrepancies between the Standard Model (SM) predictions and experimental results have been found in [Formula: see text] quark transitions. Motivated by these discrepancies, we investigated the semileptonic [Formula: see text] decay in [Formula: see text] model. In this paper, we have estimated different decay observables such as branching ratio, lepton flavor universality (LFU) ratio [Formula: see text] and forward–backward asymmetry in the SM as well as in the [Formula: see text] model. In [Formula: see text] model, we find significant deviations from the SM for the observables except for the forward–backward asymmetry. This deviation gives us a possible indication of new physics (NP).

scholarly journals Status of the NA62 Experiment

2020 ◽  
Vol 234 ◽  
pp. 01012
Author(s):  
M. Piccini
Keyword(s):  
Data Analysis ◽  
Standard Model ◽  
Indirect Effects ◽  
Branching Ratio ◽  
New Physics ◽  
Single Event ◽  
Model Framework ◽  
The Standard Model ◽  
Better Than

The decay $ {K^ + } \to {\pi ^ + }v\bar v $, with a very precisely predicted branching ratio of less than 10−10 in the Standard Model framework, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of such decay with a decay-in-flight technique, novel for this channel. The main goal of NA62 is to measure such Branching Ratio of $ {K^ + } \to {\pi ^ + }v\bar v $ with an accuracy better than 20%. This will be achieved by collecting up to 100 $ {K^ + } \to {\pi ^ + }v\bar v $ events with a background contamination at the level of 10%. The NA62 detector was commissioned in 2014 and 2015 and the experiment took physics data from 2015 to 2018. NA62 has already published the result of the 2016 data analysis. The 2017 data analysis is in progress, the single event sensitivity reached and the evaluation of the main backgrounds will be shown in this contribution.

ONE LOOP-INDUCED WZH COUPLING IN THE TWO HIGGS DOUBLET MODEL

1989 ◽  
Vol 04 (28) ◽  
pp. 2757-2766 ◽  
Author(s):  
THOMAS G. RIZZO
Keyword(s):  
Standard Model ◽  
Higgs Doublet ◽  
New Physics ◽  
Tree Level ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Charged Higgs ◽  
Doublet Model ◽  
The One ◽  
Two Higgs Doublet Model

Although absent at the tree level in models with only doublet and singlet Higgs representations, the WZH coupling can be induced at the one-loop level. We examine the size of this induced coupling in the two Higgs doublet model due to fermion as well as Higgs/gauge boson loops. Such couplings could provide a new mechanism for charged Higgs production at colliders and are ‘backgrounds’ to new physics beyond the Standard Model. We find, however, that these couplings are very weak for all regions of the parameter space explored.

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