The $O(α)$ electromagnetic radiative corrections to the $B^- \rightarrow V^0 \ell^- \barν_{\ell}$ ($V$ is a vector meson and $\ell$ a charged lepton) decay rates are evaluated using the cutoff method to regularize virtual corrections and incorporating intermediate resonance states in the real-photon amplitude to extend the region of validity of the soft-photon approximation. The electromagnetic and weak form factors of hadrons are assumed to vary smoothly over the energies of virtual and real photons under consideration. The cutoff dependence of radiative corrections upon the scale $Λ$ that separates the long- and short-distance regimes is found to be mild and is considered as an uncertainty of the calculation. Owing to partial cancellations of electromagnetic corrections evaluated over the three- and four-body regions of phase space, the photon-inclusive corrected rates are found to be dominated by the short-distance contribution. These corrections will be relevant for a precise determination of the $b$ quark mixing angles by testing isospin symmetry when measurements of semileptonic rates of charged and neutral $B$ mesons at the few percent level become available. For completeness, we also provide numerical values of radiative corrections in the three-body region of the Dalitz plot distributions of these decays.
We calculate the magnetic dipole and electric quadrupole moments associated with the radiative $Ω_{Q}^{*}\rightarrowΩ_{Q}γ$ and $Ξ_{Q}^{*}\rightarrowΞ^{\prime}_{Q}γ$ transitions with $Q=b$ or $c$ in the framework of light cone QCD sum rules. It is found that the corresponding quadrupole moments are negligibly small while the magnetic dipole moments are considerably large. A comparison of the results on the considered multipole moments as well as corresponding decay widths with the predictions of the vector dominance model is performed.
The amplitudes of $K \rightarrow πγ^* \rightarrow πe^+e^-$ and $K \rightarrow ππγ$ decays have been calculated within chiral Lagrangian approach including higher-order derivative terms and meson loops. The selfconsistency of the simultaneous description of the experimental data on the nonleptonic and radiative kaon decays have been demonstrated. We estimate the effects of ``indirect'' and ``direct'' $CP$-violation in $K^0_L \rightarrow π^0 e^+e^-$ decays and discuss $CP$-violating charge asymmetries in $K^{\pm} \rightarrow π^{\pm} π^0 γ$ decays.
I present higher-order radiative corrections from collinear and soft gluon emission for the associated production of a charged Higgs boson with a $W$ boson. The calculation uses expressions from resummation at next-to-leading-logarithm accuracy. From the resummed cross section I derive analytical formulas at approximate NNLO and N$^3$LO. Total cross sections are presented for the process $b{\bar b} \rightarrow H^- W^+$ at various LHC energies. The transverse-momentum and rapidity distributions of the charged Higgs boson are also calculated.
Z-boson decay $Z \rightarrow f\tilde{f}γγ$ in the Standard Model is analysed. The distribution function on the invariant masses of the photon and fermion pairs is calculated in the leading logarithmic approximation. It is shown that this distribution function has a specific shape of a ``crest''. (To be published in Mod.Phys.Lett.A)
In this paper we shall focus on the effects of concrete models such as SM and Model III of 2HDM on the polarized and unpolarized forward-backward asymmetries of $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ decays. The obtained results of these decay modes are compared to each other. Also, we obtain the minimum required number of events for detecting each asymmetry and compare them with the number of produced $B\bar{B}$ pairs at the LHC or supposed to be produced at the Super-LHC. At the end, we conclude that the study o…
We estimate the decay rates of $η_c\rightarrow 2γ$, $η_c'\rightarrow 2γ$, and $J/ψ\rightarrow e^+ e^-$, $ψ^\prime\rightarrow e^+e^-$, by taking into account both relativistic and QCD radiative corrections. The decay amplitudes are derived in the Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired interquark potential are used to calculate the wave functions and decay widths for these $c\bar{c}$ states. We find that the relativistic correction to the ratio $R\equiv Γ(η_c \rightarrow 2γ)/ Γ(J/ ψ\rightarrow e^+ e^-)$ is negative and tends to compensate the positive contribut…
The potentialities of the production of the scalar $K\bar K$ molecules in the $ϕ$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(ϕ\rightarrowγf_0(a_0)\rightarrowγππ(πη))\approx (1÷2)\times 10^{-5}\ ,\BR(ϕ\rightarrowγ(f_0+a_0)\rightarrowγK^+K^-)\alt 10^{-6}$ and $BR(ϕ\rightarrowγ(f_0+a_0) \to γK^0\bar K^0)\alt 10^{-8}$. The mass spectra in the $ππ ,\ πη ,\ K^+K^-\ ,\ K^0\bar K^0$ channels are calculated. The imaginary part of the amplitude $ϕ\rightarrowγf_0(a_0)$ is calculated analytically. It is obtained the phase of the scalar resonance p…
Combining heavy quark effective theory and the chiral Lagrangian approach we investigate radiative decays of pseudoscalar $D$ mesons. We first reanalyse $D^{*} \rightarrow D γ$ decays within the effective Lagrangian approach using heavy quark spin symmetry, chiral symmetry Lagrangian, but including also the light vector mesons. We then investigate $D \rightarrow V γ$ decays and calculate the $D^0 \rightarrow \bar{K}^{*0} γ$ and $D^{s+} \rightarrow ρ^+ γ$ partial widths and branching ratios.
We investigate the radiative process of the $Λ_b\rightarrow Λγ$ in the standard model as well as models with one or two compact universal extra dimensions. Using the form factors entered to the low energy matrix elements, calculated via light cone QCD in full theory, we calculate the total decay width and branching ratio of this decay channel. We compare the results of the extra dimensional models with those of the standard model on the considered physical quantities and look for the deviations of the results from the standard model predictions at different values of the compactification scale…
In view of the recent interest in the decays of mesons into a pair of light leptons, a computation of the QED radiative corrections to the decay of $π^{0}$ into an electron-positron pair is presented here. The results indicate that the peak value of the differential decay rate is reduced by about $50 \%$, because of soft-photon radiation. The number of $e^{+}e^{-}$ pairs having invariant masses in an energy bin of 0.5 MeV centered around $m_π$ is found to be about $20 \%$ smaller than the one it would be if radiative corrections were neglected.
We obtain a lower limit on the compactification scale of extra dimension via comparison of the branching ratio in the baryonic $Λ_b\rightarrow Λμ^+ μ^-$ decay channel recently measured by CDF collaboration and our previous theoretical study. We also use the newly available form factors calculated via light cone QCD sum rules in full theory to analyze the flavour changing neutral current process of the $Σ_b \rightarrow Σ\ell^+ \ell^-$ in universal extra dimension scenario in the presence of a single extra compact dimension. We calculate various physical quantities like branching ratio, forward-…
We present a new contribution to the $K_L\rightarrow γγ$ amplitude, which is ${\cal{O}}(p^4)$ within the counting rules of chiral perturbation theory. This direct (non-pole) amplitude, obtained from short-distance $s \rightarrow d γ$ quark diagrams of order $e G_F α_s/π$, and similar $s \rightarrow d γγ$ diagrams, can account for about half of the experimental amplitude. Closely following the description of the $π^0\rightarrow γγ$ and $K_L\rightarrow γγ$ processes in the variants of the same low-energy QCD, we find that both of these processes are anomalous in the same sense. Then, by the anom…
One of the possible modes suggested for detecting the Higgs particle is $pp\rightarrow ZZ\rightarrow\ell^+\ell^-ν\barν$, where the Higgs appears as a resonance on a Jacobian background. Unfortunately there are QCD background processes which mimic the final state and we are obliged to impose stringent kinematic cuts to remove them. However, in doing so we also remove a significant fraction of the signal. In this report we suggest a method, based on examining the distribution of the final state charged leptons, which could allow us to relax our cuts and thus salvage the signal.
Combining heavy quark effective theory and the chiral Lagrangian approach we investigate D meson radiative decays. First, we reanalyse $D^{*} \rightarrow D γ$ decays using heavy quark spin symmetry, chiral symmetry Lagrangian, but including also the light vector mesons. Then, we calculate branching ratios $D \rightarrow V γ$. We make some comments on the Cabbibo suppressed decays $D \to ρ/ ωγ$ and the branching ratios of $D \rightarrow P P γ$ decays.
Weak radiative decays of beauty baryons into strange baryons, induced by the electroweak penguin, are estimated by using a quark model approach. Relations between formfactors in the semileptonic and in the weak radiative decays are derived within the heavy quark effective theory. The partial decay widths are found to be of the order of $10^{-15}{\rm MeV}$ for $Λ_b\rightarrowΛγ$ and $Ξ_b\rightarrowΞγ$ and of the oder of $10^{-13}{\rm MeV}$ for $Ω_b\rightarrowΩγ$. The $Ω_b$ radiative decay is thus expected at the sizable branching ratio of approximately $10^{-4}$.
We calculate the contribution of the weak annihilation to the $B\rightarrow ργ$ decay amplitude by means of QCD sum rules using the photon light-cone wave function. We find that this long-distance contribution amounts to about 10\% of the leading short-distance effect in $B^-\rightarrow ρ^-γ$. On the other hand, weak annihilation is the dominant source of the corresponding $D$ meson decays and according to our estimates, yields branching ratios of $O(10^{-4})$ for $D^0\rightarrow \bar{K}^{*0}γ$, $O(10^{-5})$ for $D_s\rightarrow ρ^+γ$, and $O(10^{-6})$ for $D^-\rightarrow ρ^-γ$ and for $D^0\rig…
We evaluate the feasibility of measuring the $Z$ polarization from a heavy Higgs signal in the decay channel $H\rightarrow ZZ \rightarrow \ell^+ \ell^-ν\barν$. Including gluon fusion production of the Higgs, continuum production of $Z$ pairs and the QCD background of single $Z$ production with a missing jet, we find that the average value of a new variable to measure the $Z$ polarization, as a function of transverse mass, will demonstrate the existence of a Higgs boson for heavy Higgs masses up to 800 GeV at the LHC with an integrated luminosity of 10$^5$ pb$^{-1}$.
We investigate charged lepton flavor violating processes $μ\rightarrow e γ$, $μ\rightarrow e e \overline{e}$ and $μ-e$ conversion in nuclei for a class of three-loop radiative neutrino mass generation models with electroweak multiplets of increasing order. We find that, because of certain cancellations among various one-loop diagrams which give the dipole and non-dipole contributions in effective $μe γ$ vertex and Z-penguin contribution in effective $μe Z$ vertex, the flavor violating processes $μ\rightarrow eγ$ and $μ-e$ conversion in nuclei become highly suppressed compared to $μ\rightarrow …
The radiative decay of the massive neutrino $ν_i \rightarrow ν_j γ$ in a circularly polarized electromagnetic wave is investigated within the Standard theory with lepton mixing. The decay probability in the wave field does not contain a threshold factor $\sim ( 1 - m_i / m_j )$ as opposed to the decay probability in a vacuum or in a constant uniform external field. The phenomenon of the gigantic enhancement ( $\sim 10^{33}$ ) of the neutrino decay probability in external wave field is discovered. The probability of the photon splitting into the neutrino pair is obtained. (Published in Phys.Let…
We present a discussion of radiative decays $χ_{cJ}\rightarrowγρ(ω, ϕ)$. The decay amplitudes are computed within the QCD factorisation framework. NRQCD has been used in the heavy meson sector as well as a collinear expansion in order to describe the overlap with light mesons in the final state. The colour-singlet contributions to all helicity amplitudes have been computed using the light-cone distribution amplitudes of twist-2 and twist-3. All obtained expressions are well defined at least in the leading-order approximation. The colour-octet contributions have also been studied in the Coulomb…
We consider radiative corrections to the decay rate $Γ(H\rightarrow ZZ)$ of the heavy {\it CP}-even Higgs boson of the minimal supersymmetric model to two $Z$ bosons. We perform a one loop Feynman diagram calculation in the on-mass-shell renormalization scheme, and include the third generation of quarks and squarks. The tree level rate is suppressed by a mixing angle factor and decreases as $1/M_H$ for large $M_H$. The corrected rate overcomes this suppression and increases with $M_H$ for $M_H > 500$~GeV. The corrections can be very large and depend in detail on the top squark masses and $A$-t…
We investigate the radiative $B_{c} \to D_{s1} γ$ transition in the framework of QCD sum rules. In particular, we calculate the transition form factors responsible for this decay in both weak annihilation and electromagnetic penguin channels using the quark condensate, mixed and two-gluon condensate diagrams as well as propagation of the soft quark in the electromagnetic field as non-perturbative corrections. These form factors are then used to estimate the branching ratios of the channels under consideration. The total branching ratio of the $B_{c} \to D_{s1} γ$ transition is obtained to be i…
Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons ($γ_1$ and $γ_2$) and the electron ($e^-$) in the triple cascade process $\bar{p}p\rightarrow{}^3D_3\rightarrow{}^3P_2+γ_1\rightarrow(ψ+γ_2) +γ_1 \rightarrow (e^- + e^+) +γ_2 +γ_1$, when $\bar{p}$ and $p$ are arbitrarily polarized. We also derive six different partially integrated angular distribution functions which give the angular distributions of one or two particles in the final state. Our results show that by measuring the two-particle angular distribution of $γ_1$ and $γ_2$ and…
Radiative $\bar{B}^0(\bar{B}^0_s)\rightarrow J/ψγ$ decays provide an interesting case to test our understanding of (non)perturbative QCD and eventually to probe physics beyond the standard model. Recently, the LHCb Collaboration has reported an upper bound, updating the results of the BABAR Collaboration. Previous theoretical predictions based on QCD factorization or perturbative QCD have shown large variations due to different treatment of nonfactorizable contributions and meson-photon transitions. In this paper, we report on a novel approach to estimate the decay rates, which is based on a r…
In the framework of perturbative QCD, the radiative decays $J/ψ\rightarrowγη^{(\prime)}$ are revisited in detail, where the involved one-loop integrals are evaluated analytically with the light quark masses kept. We have found that the sum of loop integrals is insensitive to the light quark masses and the branching ratios $\mathcal{B}(J/ψ\rightarrowγη^{(\prime)})$ barely depend on the shapes of $η^{(\prime)}$ distribution amplitudes. With the parameters of $η-η^{\prime}$ mixing extracted from low energy processes and $J/ψ\rightarrowγη^{(\prime)}$ by means of nonperturbative matrix elements $\l…
We show that there are two reasons why the partial width for the transition $Γ_1(Υ(3S)\rightarrow γχ_{b1}(1P))$ is suppressed. Firstly, the spin-averaged matrix element (m.e.) $\bar{I(3S|r|1P_J)}$ is small, being equal to 0.023 GeV$^{-1}$ in our relativistic calculations. Secondly, the spin-orbit splittings produce relatively large contributions, giving $I(3S|r|1P_2)=0.066$ GeV$^{-1}$, while due to large cancellation the m.e. $I(3S|r|1P_1)=-0.020$ GeV$^{-1}$ is small and negative; at the same time the magnitude of $I(3S|r|1P_0)=-0.063$ GeV$^{-1}$ is relatively large. These m.e. give rise to th…
Weak vector boson scattering (VBS) at the LHC provides an excellent source of information on the structure of quartic gauge couplings and possible effects of physics beyond the SM in electroweak symmetry breaking. Parameterizing deviations from the SM within an effective field theory at tree level, the dimension-8 operators, which are needed for sufficiently general modeling, lead to unphysical enhancements of cross sections within the accessible energy range of the LHC. Preservation of unitarity limits is needed for phenomenological studies of the $VVjj$ events which signify VBS. Here we deve…
Bardeen-Buras-Gérard have proposed a large N$_c$ method to evaluate hadronic weak matrix elements to attack for instance the determination of the $ΔI= \frac{1}{2}$-rule and $\mathrm{Re}(\frac{ε'}ε)$. Here we test this method to the determination of the form factor parameters $a_+$ and $b_+$ in the decays $K^+ \rightarrow π^+ \ell^+ \ell^- $ and $K_S \rightarrow π^0 \ell^+ \ell^-$. The results are encouraging: in particular after a complete treatment of Vector Meson Dominance (VMD).
The radiative decays of heavy mesons and heavy baryons are studied in a formalism which incorporates both the heavy quark symmetry and the chiral symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy hadrons consist of two pieces: one from gauging electromagnetically the strong-interaction chiral Lagrangian, and the other from the anomalous magnetic moment interactions of the heavy baryons and mesons. Due to the heavy quark spin symmetry, the latter contains only one independent coupling constant in the meson sector and two in the baryon sector. These coupling constant…
Adding a scalar singlet provides one of the simplest extensions of the Standard Model. In this work we briefly review the latest constraints on the mass and mixing of the new Higgs boson and study its production and decay at the LHC. We mainly focus on double Higgs production in the $hh \rightarrow b \bar{b} WW \rightarrow b \bar{b} \ell^+ ν\ell^- \barν$ decay channel. This decay is found to be efficient in a region of masses of the heavy Higgs boson of 260 - 500 GeV, so it is complementary to the 4$b$ channel, more efficient for Higgs bosons having masses greater than 500 GeV. We analyse this…
A status report on the theory of radiative rare $B$ decays in the standard model is presented, with focus on inclusive decays $B \rightarrow X_{(s,d)}\, γ$ and exclusive decays $B \rightarrow (K^\ast,ω,ρ) \, γ$. CP asymmetries are also briefly discussed.
We analyze the semileptonic $ B_{s} \rightarrow D_{s2}^{*}(2573)\ell\bar{ν}_{\ell}$ transition, where $\ell=τ,~μ$ or $e$, within the standard model. We apply the QCD sum rule approach to calculate the transition form factors entering the low energy Hamiltonian defining this channel. The fit functions of the form factors are used to estimate the total decay widths and branching fractions in all lepton channels. The orders of branching ratios indicate that this transition is accessible at LHCb in near future.
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 examine the parameter space of supersymmetric models with $R$-parity violating interactions of the form $λ' L Q D^c$ to explain the various anomalies observed in $b \rightarrow s \ell \ell$ transitions. To generate the appropriate operator in the low energy theory, we are led to a region of parameter space where loop contributions dominate. In particular, we concentrate on parameters for which diagrams involving winos, which have not been previously considered, give large contributions. Many different potentially constraining processes are analyzed, including $τ\rightarrow μμμ$, $B_s-\bar{B…
In rare $B$ meson decays $B\rightarrow K \ell^+ \ell^-$, a possible contribution of $\ell^+\ell^-$ emission via photon from the "spectator" quark $q$ ($q=u,d$) in the $B$ meson $(q\bar{b})$ is investigated in addition to the conventional one $\bar{b} \rightarrow \bar{s} +γ\rightarrow \bar{s}+\ell^+ + \ell^-$. If such a contribution is sizable compared with the standard estimation of $B\rightarrow K \ell^+ \ell^-$, we will observe visible difference between $d Γ(B^0\rightarrow K^0 \ell^+ \ell^-)/d q^2$ and $d Γ(B^+\rightarrow K^+ \ell^+ \ell^-)/d q^2$ in $q^2$ dependence ($q^2 \equiv m_{\ell\el…
The rare semileptonic $B_c \rightarrow D_{s,d}\, \ell^+ \ell^-$ decays are studied in the universal extra dimension with a single extra dimension scenario. The sensitivity of differential and total branching ratios, polarization asymmetries of final state leptons to the compactification parameter is presented, both for muon and tau decay channels. Comparing with the standard model, the obtained results indicate that there are new contributions to the physical observables. Considering the ability of available experiments, it would be useful to study these effects.
We present the full $\mathcal{O}(α)$ electroweak radiative corrections to the process $e^+e^- \rightarrow t \bar{t} γ$ at the International Linear Collider (ILC). The computation is performed with the help of the GRACE-Loop system. We present the total cross-section and the top quark forward-backward asymmetry ($A_{FB}$) as a function of the center-of-mass energy and compare them with the process $e^+e^- \rightarrow t \bar{t}$. We find that the value of $A_{FB}$ in $t \bar{t} γ$ production is larger than $A_{FB}$ in $t\bar{t}$ production. It is an important result for the measurement of the to…
In this paper we analyze the dilepton mass square $q^2$ dependency of single lepton polarization asymmetries and CP violation for $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-, \ell=μ,τ)$ in the 2HDM context. Also, we study the averages of these asymmetries in the domain $4 m_{\ell}^2<q^2< (m_B-m_{{K}_0^{*}})^2$. Our study manifests that the investigation of the above-mentioned asymmetries for $\overline{B}\rightarrow \overline{K}_0^*(1430) \ell^+\ell^-$ processes could provide useful information for probing new Higgs bosons in the future B-physics experiments.
Inspired by the recent experimental results which show deviations from the standard model (SM) predictions of $b\rightarrow s \ell^+\ell^-$ transitions, we study the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended by the inverse seesaw mechanism. The trilinear $R$-parity violating terms, together with the chiral mixing of sneutrinos, induce the loop contributions to the $b\rightarrow s \ell^+\ell^-$ anomaly. We study the parameter space of the single-parameter scenario $C^{\rm NP}_{9,μ}=-C^{\rm NP}_{10,μ}=C_{\rm V}$ and the double-parameter scenario $(C_{\rm V},C…
It is shown that an alternative form of the parity-nonconserving (PNC) transition electromagnetic current resolves partly a puzzle with the Hara theorem. New formulation of it has allowed PNC weak radiative hyperon transitions of the charged hyperons $Σ^{+} \Rightarrow p + γ$ and $Ξ^{-} \Rightarrow Σ^{-} + γ$ revealing hitherto unseen transition toroid dipole moment.
By using the GRACE-Loop system, we calculate the full $\mathcal{O}(α)$ electroweak radiative corrections to the process $e^+e^- \rightarrow e^+e^- γ$, which is important for future investigations at the International Linear Collider (ILC). With the GRACE-Loop system, the calculations are checked numerically by three consistency tests: ultraviolet finiteness, infrared finiteness, and gauge-parameter independence. The results show good numerical stability when quadruple precision is used. In the phenomenological results, we find that the electroweak corrections to the total cross section range f…
Radiative corrections to the subprocess of annihilation of quark-antiquark pair of prompt photon production in proton-proton collisions at NICA energies $\sqrt{\mathbf{s}}$= 10 GeV
Baku State University（巴库国立大学）；Institute of Physical Problems, Baku State University（巴库国立大学物理问题研究所）
Using form factors enrolled to the transition matrix elements and calculated via light-cone QCD sum rules including next-to-leading order corrections in the strong coupling constant, we provide a systematic analysis of the $ B_s\rightarrow f_0 (980)\ell^+\ell^- $ both in the standard and universal extra dimension models. In particular, we discuss sensitivity of the differential branching ratio and various double lepton polarization asymmetries on the compactification factor of extra dimension and show how the results of the extra dimension model deviate from the standard model predictions. The…
Double polarized forward-backward asymmetries in $B\rightarrow K_{1}(1270,1400)\ell^{+}\ell^{-}$ with $\ell=μ, τ$ decays are studied, using most general non-standard local four-fermi interactions, where the mass eigenstates $K_{1}(1270)$ and $K_{1}(1400)$ are the mixture of $^{1}{P}_{1}$ and $^{3}{P}_{1}$ states with the mixing angle $θ_{K}$. We have calculated the expressions of nine doubly polarized forward-backward asymmetries and it is presented that the polarized lepton pair forward-backward asymmetries are greatly influenced by the new physics. Therefore, these asymmetries are interestin…
This paper considers the implications of the heavy quark and chiral symmetries for the semi-leptonic decay $B \rightarrow D^* X \ell \bar ν_\ell$. The general kinematic analysis for decays of the form {\sl pseudoscalar meson $\rightarrow$ vector meson $+$ pseudoscalar meson $+$ lepton $+$ anti-lepton} is presented. This formalism is applied to the above exclusive decay which allows the differential decay rate to be expressed in a form that is ideally suited for the experimental determination of the different form factors for the process through angular distribution measurements. Heavy quark an…
Higgs boson radiative decays of the form $H\rightarrow f\bar{f}γ$ are calculated in the Standard Model using the complete one-loop expressions for the decay amplitudes. Contributions to the radiative width from leptons and light quarks are given. We also present $e\bar{e}$ invariant mass distributions for $H\rightarrow e\bar{e}γ$, which illustrate the importance of the photon pole contribution and the effects of the box diagrams.
We discuss on the search for the right-handed weak interaction effects in the SU(2)$_L \times$SU(2)$_R$ model with lepton doublets $(ν_\ell, \ell^-)_L$ and $(N_\ell, \ell^-)_R$ ($\ell = e, μ, τ)$. We will point out that only the chance of the observation of the right-handed weak interaction effect will be in the rare decay $K^+ \rightarrow π^- μ^+ μ^+$.
The X(3872) radiative decay is discussed by employing a two-meson multichannel model with the charmonium components, which explains many of the other observed features of X(3872). We have found that the ratio of the branching fractions of the X(3872) radiative decays, $R_γ=\text{Br}(X(3872)\rightarrowψ(2S)γ)$ / Br$(X(3872)\rightarrow J/ψγ)$, is 1.1 $\sim$ 3.4 if one assumes that the decay occurs only from the charmonium components. The invariant mass spectra of $cc^{bar}$($2P$)$\rightarrow J/ψγ$ and $cc^{bar}$($2P$)$\rightarrow ψ(2S) γ$ are also investigated. It is found that an enhancement ap…
We fit the unfolded data of $\bar{B}^0\rightarrow D^{*+} \ell \overlineν$ from the Belle experiment, where $\ell \equiv e, μ$, using a method independent of heavy quark symmetry to extrapolate to zero-recoil and extract the value of $|V_{cb}|$. This results in $|V_{cb}| = (41.9^{~+2.0}_{~-1.9})\times 10^{-3}$, which is robust to changes in the theoretical inputs and very consistent with the value extracted from inclusive semileptonic $B$ decays.
We study the decay $B_c \rightarrow D_s^* γ$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}sγ$ transition and the other occurs through weak annihilation accompanied by a photon emission.The electromagnetic penguin contribution is estimated by perturbative QCD and found to be $4.68\times10^{-18}$ GeV. In particular, we find the contribution of the weak annihilation is $6.25\times10^{-18}GeV$ which is in the same order as that of the electromagnetic penguin. The total decay rate $Γ(B_c \rightarrow D_s^* γ)$ is predicted to be $1.45\…
QCD radiative correction to Higgs $\rightarrow$ two photons decay rate is calculated. Below the threshold we found negligible correction, thus supporting results obtained earlier by Djouadi et all [7]. Above the threshold radiative correction appears to be large for both real and imaginary part of H $γγ$ vertex. This leads to radiative correction for $Γ$(H $\rightarrow γγ$) to be of order 20--100 percents at $m_{t}=150 GeV$. Possible applications of our results for Higgs search at Next Linear Colliders (NLC) are briefly discussed.
A new particle of mass around 125 GeV is known to have loop induced couplings to $gg$ and $γγ$. More specific to the Higgs interpretation are tree level couplings to $W$ and $Z$. A small but clean signal of the Higgs coupling to $W$ arises from associated production of a Higgs, with $H\rightarrowγγ$. We consider this signal in light of a large NLO enhancement of the irreducible background.
We comparatively analyze the flavor changing neutral current process of the $Λ_b \rightarrow Λ\ell^+ \ell^-$ in the standard model as well as topcolor-assisted technicolor model using the form factors calculated via light cone QCD sum rules in full theory. In particular, we calculate the decay width, branching ratio and lepton forward-backward asymmetry related to this decay channel. We compare the results of the topcolor-assisted technicolor model with those of the standard model and debate how the results of the topcolor-assisted technicolor model depart from the standard model predictions. …
At present, there are many experimental and theoretical results for $J/ψ\rightarrowη_{c}+γ$ process, while the results are inconsistent based on different methods and considerations. In this paper, the light cone sum rules method is used in studying the radiative decay $J/ψ\rightarrowη_{c}+γ$. We give the transition form factor of this process based on the leading twist distribution amplitude of $η_{c}$ meson, with this form factor further obtain the decay width. Our result is consistent with those of other sum rules. A comparison of our result with others' about the decay width is also presen…
