We present new precision predictions for semitauonic decays involving $ρ$ and $ω$ final state mesons. These decay channels offer an interesting orthogonal probe to study the existing B anomalies in semitauonic transitions and are accessible with the Belle II experiment. The predictions are based on combining existing light-cone sum-rule calculations for the form factors with measured experimental spectra from the BaBar and Belle collaborations. This allows us to reliably extrapolate the light-lepton form factor predictions to large values of the four-momentum transfer squared, $q^2$, and in turn to derive precise predictions for $R_ρ$ and $R_ω$, the ratio of the total decay rates of $B \rightarrow ρτν_τ$ and $B \rightarrow ωτν_τ$ for $τ$ final states with respect to light leptons in the SM. In addition, we investigate the impact of all four-fermi operators on the semitauonic $q^2$ spectra and these ratios.
We perform a model independent analysis to identify new physics operators which can enhance the branching ratio of $B_s^* \rightarrow μ^+ μ^-$ above its Standard Model (SM) prediction. We find that none of the new physics operators which provide a good fit to $b \rightarrow s μ^+ μ^-$ data can enhance the Br($B_s^* \rightarrow μ^+ μ^-$) above its SM value.
The precise knowledge of the QED initial state corrections is of instrumental importance in studying high luminosity measurements in $e^+e^-$ annihilation at facilities like LEP, the International Linear Collider ILC, CLIC, a Giga-$Z$ facility, and the planned FCC\_ee. Logarithmic corrections of up to $O(α^6 L^5)$ are necessary with various subleading terms taken into account. This applies to both the inclusive measurement of processes like $e^+ e^- \rightarrow γ^*/Z^*$ and also the forward-backward asymmetry. As has been shown recently, techniques from massive QCD, such as the computation of …
We put forward the framework of simplified leptoquark models: simple extensions of the Standard Model that serve as benchmarks to test the interactions of leptons with new colored degrees of freedom considered, for instance, in leptoquark or grand unification models. As a first application of the scheme, we analyze the power of precision lepton observables by computing gauge invariant two-loop radiative corrections to the lepton-photon vertex, generated here by Yukawa interactions between the lepton and new colored degrees of freedom. The result, detailed in explicit expressions for the involv…
A "Higgs factory", an electron-positron collider with center-of-mass energy of about 250 GeV, will measure the cross section of the Higgsstrahlung process, $e^+e^-\rightarrow hZ$, with sub-percent precision. This measurement is sensitive to a variety of new physics scenarios. In this paper, we study two examples. First, we compute corrections to the $e^+e^-\rightarrow hZ$ differential cross section in the effective field theory (EFT) approach, including the complete set of dimension-6 operators contributing to this process. These results are applicable to any model where the new physics mass s…
Beyond the Standard Model Higgs physics: Hunting $h \rightarrow bs$ with Higgs-strahlung at CEPC and FCC-ee
Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学）；Centro Interdisciplinario de Investigación y Enseñanza de la Ciencia (CIIEC)（科学交叉研究与教育中心）；Universidad Nacional Autónoma de México（墨西哥国立自治大学）
We have measured the ratio $σ(e^+e^-\rightarrowπ^+π^-γ)/σ(e^+e^-\rightarrow μ^+μ^-γ)$, with the KLOE detector at DA$Φ$NE for a total integrated luminosity of $\sim$ 240 pb$^{-1}$. From this ratio we obtain the cross section $σ(e^+e^-\rightarrowπ^+π^-)$. From the cross section we determine the pion form factor $|F_π|^2$ and the two-pion contribution to the muon anomaly $a_μ$ for $0.592<M_{ππ}<0.975$ GeV, $Δ^{ππ} a_μ$= $({\rm 385.1\pm1.1_{stat}\pm2.7_{sys+theo}})\times10^{-10}$. This result confirms the current discrepancy between the Standard Model calculation and the experimental measurement o…
We investigate extremely rare top quark decays at a future proton-proton collider with centre-of-mass energy of 100 TeV. We focus on two decay modes: radiative decay with a $Z$ boson, $t \rightarrow b WZ$, and flavour-changing neutral decay with a Higgs boson, $t \rightarrow h c$, the former being kinematically suppressed with a branching ratio of $\mathcal{O}(10^{-6})$, and the latter highly loop-suppresed, with a branching ratio of $\mathcal{O}(10^{-15})$. We find that $t \rightarrow b WZ$ will be very challenging to observe in top quark pair production, even within well-motivated beyond-the…
We study relativistic corrections in exclusive $S$-wave charmonium decays into proton-antiproton final state. We calculate the NRQCD corrections to the dominant decay amplitude, which depend on the nucleon twist-3 light-cone distribution amplitudes only. It is shown that in this case the collinear factorisation is also valid beyond the leading-order approximation. Our numerical estimates show that relativistic correction of relative order $v^2$ provides large numerical impact.
The semi-leptonic baryonic $b\to s$ decay, $Λ_b\rightarrow Λ\ell^+\ell^-$, has been studied and new angular observables and asymmetries have been proposed which can test the presence of new physics beyond the standard model.
In the framework of BLMSSM, the Higgs decays $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$ are studied where $m_V$ represents a vector meson($ρ, ω, ϕ, J/ψ, Υ$ etc.). Corrections to the CP-even and CP-odd $h^0γZ$ couplings occur via loop diagrams where new particles are involved. Actually both of them obviously influence the decay rates of $h^0\rightarrow Zγ$ and $h^0\rightarrow m_VZ$. Concretely, our obtained numerical result shows that the decay width of $h^0\rightarrow Zγ$ can be 1.3 times larger than the prediction of the Standard Model(SM). For the light mesons ($ρ,ω$), the corrections to …
The rare decays $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ are important to research new physics beyond standard model. In this work, we investigate two loop electroweak corrections to $\bar B\rightarrow X_sγ$ and $B_s^0\rightarrow μ^+μ^-$ in the minimal supersymmetric extension of the SM with local $B-L$ gauge symmetry (B-LSSM), under a minimal flavor violating assumption for the soft breaking terms. In this framework, new particles and new definition of squarks can affect the theoretical predictions of these two processes, with respect to the MSSM. Considering the constraints fro…
Babar collaboration has reported an intriguing opposite sign in the integrated decay rate asymmetry $A_{cp}(τ\rightarrow K_{s} πν_τ)$ than that of SM prediction from the known $K^{0}$ - $\bar{K^{0}}$ mixing. Babar's result deviate from the SM prediction by about 2.7$σ$. If the result stands with higher precision in the future experiments, the observed sign anomaly in the $A_{cp}(τ\rightarrow K_{s} πν_τ)$ can most likely come only from a NP. In this work we present a full angular spectrum analysis on the contribution to $A_{cp}(τ\rightarrow K_{s} πν_τ)$ coming from the tensorial term. Assuming …
At Moriond 2019, Belle collaboration announced their new measurements on $R_D$ and $R_{D^*}$ which are in agreement with their Standard Model (SM) predictions within $1.2σ$. After inclusion of these measurements, the discrepancy between the world averages and the SM predictions of $R_D$-$R_{D^*}$ comes down from $4.1σ$ to $3.1σ$. Here we do a global fit by taking all measurements in $b\rightarrow cτ\barν$ transition. We find that there are seven allowed new physics solutions, each with different Lorentz structure. Further we show that it is possible to distinguish between them by means of the …
One of the most-studied signals for physics beyond the standard model in the production of gauge bosons in electron-positron collisions is that due to the anomalous triple gauge boson couplings in the $Z γ$ final state. In this work, we study the implications of this at the ILC with polarized beams for signals that go beyond traditional anomalous triple neutral gauge boson couplings. Here we report a dimension-8 CP-conserving $Z γZ$ vertex that has not found mention in the literature. We carry out a systematic study of the anomalous couplings in general terms and arrive at a classification. We…
We present analytical results for higher order corrections to the decay spectra of inclusive semileptonic heavy hadron weak decays using the heavy quark expansion (HQE). We compute analytically the spectrum of the leptonic invariant mass for $B \rightarrow X_c \ell \barν$ up to and including terms of order $1/m_Q^3$ within the HQE at next-to-leading order (NLO) in $α_s$. The full dependence of the differential rate on the mass of the final-state quark is taken into account. We discuss the implications of our results for the precision determination of the CKM matrix element $|V_{cb}|$.
An attempt has been made to carry out a detailed analysis of quark mass matrices having structure beyond the minimal texture. In particular, keeping in mind, precision measurements of CKM parameters as well as refinements in the ranges of light quark masses, we have examined the viability of all possible combinations of hermitian texture 5 zero quark mass matrices. Interestingly, one finds that all these possibilities are now excluded by the present quark mixing data, thereby, having important implications for model building.
The R-parity conserving MSSM in light of the decay $B_s\rightarrowμ^+μ^-$ with near-SM branching ratio is an interesting platform for studying the complementarity between direct and indirect searches for beyond the SM physics. Based on this, we have analysed the possible impact of the $B_s\rightarrowμ^+μ^-$ observation on the posterior sample from the global fit of a 30-parameter MSSM (MSSM-30), and the related Wilson Coefficients. The MSSM-30 is a systematically constructed, symmetry-guided, MSSM parametrization, as opposed to the traditional frames (e.g. pMSSM) with crude treatment of flavor…
Charged Lepton Flavor Violation (cLFV) processes like $ μ\rightarrow e γ$ are rare decay processes, that are another signature of physics beyond Standard Model (BSM). These processes have been studied in various models, that could explain neutrino oscillations and mixings. In this work, we present bounds on cLFV decay $ μ\rightarrow e γ$ in a $ μ$-$ τ$ symmetric SUSY SO(10) theory, using type I seesaw mechanism. The updated constraints on BR($ μ\rightarrow e γ$) from MEG experiment, recently measured value of Higgs mass at LHC and value of $θ_{13}$ from reactor data have been used. We present …
We suggest a discriminant analysis of new physics beyond the standard model through a detection of photon polarization in a radiative B meson decay. This analysis is investigated in SUSY SU(5) GUT with right-handed neutrino and left-right symmetric models. New physics search via CP asymmetry in the same process are also evaluated in each model for comparison. We show that new physics can be found via detecting the photon polarization in a parameter space of TeV energy scale.
Anomalies in semi-leptonic $B$ decays could indicate new physics beyond the standard model(SM). There is an older puzzle in non-leptonic $B \to πK$ decays. The new particles, leptoquarks and diquarks, required to solve the semi-leptonic and the non-leptonic puzzles can also generate neutrino masses and mixing at loop level. We show that a consistent framework to explain the $B$ anomalies and the neutrino masses is possible and we make predictions for certain rare nonleptonic $B$ decays.
The article outlines the recent developments in the theoretical and computational approaches to the higher-order electroweak effects needed for the accurate interpretation of MOLLER and Belle II experimental data, and shows how new-physics particles enter at the one-loop level. By analyzing the effects of $Z'$-boson on the polarization asymmetry, we show how this hypothetical interaction carrier may influence the future experimental results.
In this paper, we present general one-loop form factors for $H\rightarrow γ^* γ^*$ in $R_ξ$ gauge, considering all cases of two on-shell, one on-shell and two off-shell for final photons. The calculations are performed in standard model and in arbitrary beyond the standard models which charged scalar particles may be exchanged in one-loop diagrams. Analytic results for the form factors are shown in general forms which are expressed in terms of the Passarino-Veltman functions. We also confirm the results in previous computations which are available for the case of two on-shell photons. The $ξ$-…
Lepton flavor violation decays are channels which may lead to fundamental discoveries in the forthcoming years and this make it an exciting research field for beyond the Standard Model searches. In this work, we present an analysis of the lepton flavor violation decays $l_α\rightarrow 3l_β$ in Minimal R-symmetric Supersymmetric Standard Model. The prediction for BR($l_α\rightarrow 3l_β$) depend on the off-diagonal entries of the slepton mass matrix. The contributions to Wilson coefficients can be classified into Higgs penguins, photon penguins, Z penguins, and box diagrams. It shows the contri…
The implications of the latest measurement of the branching fraction of B($ b\rightarrow s γ$) of b hadrons, which is another signature of New Physics beyond Standard Model is presented here. The quark transitions $ b \rightarrow s $, $ b \rightarrow d $ do not happen at tree level in the Standard Model as the Z boson does not couple to quarks of different flavour. In this work the present bounds on the quark transition $ b \rightarrow s $ within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which there are three independent soft SUSY breaking parameters $ …
The observation of anomalies in the charged current $b\rightarrow c\bar{\ell}ν_{\ell}$ transitions hints the possibility of the existence of new physics beyond the standard model. Inspired by the work done in the beauty quark sector, we explore new physics in the charm quark sector with $c \rightarrow (s,d)\bar{\ell}ν_{\ell}$ charged current transitions. We analyze the decay modes $D_{(s)}^+ \to η^{(')} \bar{\ell} ν_{\ell}$ within an effective Lagrangian framework which includes both standard model and new physics contributions. We use the available experimental measurements of the semileptoni…
We study the quark flavor violating Higgs-boson decay $h \rightarrow \bar b s + b \bar s$ in the Minimal Supersymmetric Standard Model (MSSM). The decay is analyzed first in a model independent, and in a second step in the minimal flavor violationg (MFV) Constrained MSSM. The experimental constraints from $B$-Physics observables (BPO) and electroweak precision observables (EWPO) are also calculated and imposed on the parameter space. It is shown that in some cases the EWPO restrict the flavor violating parameter space stronger than the BPO. In the model independent analysis values of ${\cal O}…
Theoretical Uncertainties and Phenomenological Aspects of $B \rightarrow X_s γ$ Decay
我们分析的不确定性的理论预测的包容性分支比$BR[B \rightarrow X_s γ]$。我们发现，主导的不确定性，在领导秩序的表达来自其$μ$依赖。我们讨论了一个下一个领先的顺序计算$B \rightarrow X_s γ$一般条款和检查到何种程度的$μ$的依赖性可以减少在这样的计算。我们提出了对标准模型和双希格斯模型参数的限制，这些参数来自于对$b \rightarrow s γ$衰变的测量。目前的理论不确定性不允许明确限制标准模型参数远远超出其他实验的限制。双希格斯双重模型的边界仍然非常强，尽管比最近文献中的边界弱得多。在双Higgs模型中，$b \rightarrow s γ$、$Z \rightarrow b \bar{b}$和$b \rightarrow c τ\barν_τ$过程足以给出$M_{H^{\pm}}-tan β$平面上最严格的边界。
We calculate the mass difference between the $Υ$ and $η_b$ and the $Υ$ leptonic width from lattice QCD using the Highly Improved Staggered Quark formalism for the $b$ quark and including $u$, $d$, $s$ and $c$ quarks in the sea. We have results for lattices with lattice spacing as low as 0.03 fm and multiple heavy quark masses, enabling us to map out the heavy quark mass dependence and determine values at the $b$ quark mass. Our results are: $M_Υ -M_{η_b} = 57.5(2.3)(1.0) \,\mathrm{MeV}$ (where the second uncertainty comes from neglect of quark-line disconnected correlation functions) and decay…
Inspired by the observation of the pentaquark states $P_{c}(4312),P_{c}(4440)$ and $P_{c}(4457)$ at LHCb, photoproduction of these three $P_{c}$ states via the interaction $γp\rightarrow J/ψp$ is investigated in an effective Lagrangian approach. The $t$-channel Pomeron exchange diffractive process is considered as the main background for the $J/ψ$ photoproduction. The numerical results show that the theoretical cross section, which is calculated by assuming a branching ratio $Br[P_{c}\rightarrow J/ψp]\simeq 3\%$, is consistent with the existing experimental data of the $ γp\rightarrow J/ψp$ pr…
We present a complete one-loop computation of the $H^\pm \rightarrow W^\pm Z$ decay in the aligned two-Higgs-doublet model. The constraints from the electroweak precision observables, perturbative unitarity, vacuum stability and flavour physics are all taken into account along with the latest Large Hadron Collider searches for the charged Higgs. It is observed that a large enhancement of the branching ratio can be obtained in the limit where there is a large splitting between the charged and pseudo-scalar Higgs masses as well as for the largest allowed values of the alignment parameter $ς_u$. …
We conduct a numerical study over the constrained MSSM (CMSSM), Next-to-MSSM (NMSSM) and $U(1)$ extended MSSM (UMSSM) to probe the allowed mass ranges of the charged Higgs boson and its dominant decay patterns, which might come into prominence in near future collider experiments. {We present results obtained from a limited scan for CMSSM} as a basis and compare its predictions with the extended models. We observe within our data that a wide mass range is allowed as $0.5(1) \lesssim m_{H^{\pm}} \lesssim 17$ TeV in UMSSM (NMSSM). We find that the dominant decay channel is mostly $H^{\pm}\rightar…
In this work the vector boson scattering process is investigated through the reaction $pp\rightarrow 2 \mathrm{jets} + W^\ast W^\ast \rightarrow 2 \mathrm{jets} + lν_l l'ν_l'$, where $W^\ast$ denote in general off-shell $W^+$, in the EFT approach with the HL-LHC and HE-LHC experiments in mind. We have investigated the discovery potential of certain classes of the EFT "models" of both the SMEFT and HEFT bases with the particular emphasis on using the EFT "models" in their region of validity. A novel method has been proposed for determining the discovery regions of physics beyond the SM, describ…
In this paper, we explore the collider phenomenology of the charged Higgs boson in the context of a generic Beyond Standard Model scenario with extended gauge and scalar sectors. In such scenarios, the charged Higgs boson can decay via the $W^{'}Z/ WZ^{'}$ channels. We formulate a search strategy for the $H^{\pm}$ in the channel $σ(g b \rightarrow H^{\pm}t)\mathcal{BR}(H^{\pm} \rightarrow W' Z)$ considering the interesting cascade decay chain $H^{\pm} \rightarrow W^{'} Z \rightarrow W^{\pm} Z Z$. We find that the charged Higgs can be discovered in final states with multiple hard leptons and/ o…
Models beyond the Standard Model with extra scalars have been highly motivated by the recent discovery of a Higgs boson. The Two Higgs Doublet Model Type III considers the most general case for the scalar potential, allowing mixing between neutral CP-even and CP-odd scalar fields. This work presents the results of the study on the $t\rightarrow cγ$ decay at one loop level if neutral flavor changing is generated by top-charm-Higgs coupling given by the Yukawa matrix. For instance, a value for the branching ratio $Br(t\rightarrow cγ)\sim 10^{-6}$ for $\tanβ=2.5$ and general neutral Higgs mixing …
Several experimental proposals expect to confirm the recent measurement of the coherent elastic neutrino-nucleus scattering (CEvNS). Motivated in particular by the next generation experiments of the COHERENT collaboration, we study their sensitivity to different tests of the Standard Model and beyond. We analyze the resolution that can be achieved by each future proposed detector in the measurement of the weak mixing angle; we also perform similar analysis in the context of Non-Standard Interaction (NSI) and in the case of an oscillation into a sterile neutrino state. We show that the future p…
We demonstrate how the measurements of the Higgs-fermion and Higgs-gauge boson couplings can be interpreted in terms of physics beyond the Standard Model in a model-independent way. That is, we describe deviations from the Standard Model by effective $d=6$ operators made of Higgs fields and gauge fields, under the hypothesis that the new physics may show up in the Higgs sector only and the effective operators are generated at tree level. While the effective operator coefficients are independent in general, the completion of the theory at high energies will lead to specific correlations which w…
Koike et al. proposed the charged lepton flavor violation (CLFV) decay of the muonic atom $μ^-e^-\rightarrow e^-e^-$ as one of the promising processes to search for new physics beyond the standard model. It was found that the attractive interaction of leptons with the nucleus enhances the transition rate of the $μ^-e^-\rightarrow e^-e^-$ process. We report on our improved analysis of this process by taking into account the distortion of the out-going electrons in the nuclear Coulomb potential and the relativistic treatment of the muon and the electrons. As results, we found significant enhance…
Recently several measurements in the neutral current sector $b\rightarrow s l^+l^-$ ($l=e$ or $μ$) as well as in the charged current sector $b \rightarrow c τ\barν$ show significant deviations from their Standard Model predictions. It has been shown that two different new physics solutions can explain all the anomalies in $b\rightarrow s l^+l^-$ sector. Both these solutions are in the form of linear combinations of the two operators $(\bar{s}γ^αP_Lb)(\barμγ_αμ)$ and $(\bar{s}γ^αP_Lb)(\barμγ_αγ_5μ)$. We show that the longitudinal polarization asymmetry of the muons in $B^*_s\rightarrow μ^+\,μ^-…
Parity-violating Moller scattering measurements are a powerful probe of new physics effects, and the upcoming high-precision experiments will require a new level of accuracy for electroweak radiative corrections (EWC). First, we perform the updated calculations of one-loop EWC for Moller scattering asymmetry using two different approaches: semi-automatic, precise, with FeynArts and FormCalc as base languages, and "by hand", with reasonable approximations. In addition, we provide a tuned comparison between the one-loop results obtained in two different renormalization schemes: on-shell and cons…
