We demonstrate that exclusive B decays to P-wave charmonium factorize in the non-relativistic limit provided that colour-octet contributions are taken into account, and estimate the branching fractions. Although there are very large uncertainties, we find reasonable parameter choices, where the main features of the data -- large corrections to (naive) factorization and suppression of the chi_{c2} and h_c final states -- are reproduced though the suppression of chi_{c2} is not as strong as seen in the data. Our results also provide an example, where an endpoint divergence in hard spectator-scattering factorizes and is absorbed into colour-octet operator matrix elements.
The discrepancies found between S-wave and P-wave fits for hyperon decays are reinvestigated using the heavy baryon chiral Lagrangian formalism. The agreement is found to improve through the inclusion of previously omitted diagrams. The S-waves are unaffected by this, but the P-wave predictions are modified. A correlated fit to the chiral parameters is performed and the results discussed.
We present a calculation of $η_{c}\rightarrow l^{+}l^{-}$ and $χ_{c0}\rightarrow l^{+}l^{-}$ decay widths. The amplitudes are computed within leading-order approximation using NRQCD framework. Numerical results for the branchings fractions are presented.
The pionic coupling constants in the decays of the $1^{-+}$ hybrid meson are calculated. The double Borel transformation is invoked and continuum contribution is subtracted. The decay widths of the processes $1^{-+}\to ρπ, f_1 π, πγ$ are around $40, 100, 0.3$ MeV respectively.
The double lepton pair decay modes of the K_L meson are analyzed including all contributions of order p^6 in Chiral Perturbation Theory. The experimentally established e^+ e^- e^+ e^- mode and the recently observed e^+ e^- mu^+ mu^- mode are discussed in detail.
An implicit four dimensional regularization is applied to calculate the axial-vector-vector anomalous amplitude. The present technique always complies with results of Dimensional Regularization and can be easily applied to processes involving odd numbers of $γ_5$ matrices. This is illustrated explicitely in the example of this letter.
Two-body decays of B mesons are studied by decomposing their amplitude into a sum of factorizable and non-factorizable ones. The former is estimated by using the naive factorization while the latter is calculated by using a hard pion (or kaon) approximation in the infinite momentum frame. It is seen that the non-factorizable contribution is small but not negligible in color favored decays while it is more important in color mismatched decays.
We first review the current algebra - PCAC approach to nonleptonic octet baryon 14 weak decay B (\to) (B^{\prime})(π) amplitudes. The needed four parameters are independently determined by (Ω\to Ξπ),(ΛK) and (Ξ^{-}\to Σ^{-}γ) weak decays in dispersion theory tree order. We also summarize the recent chiral perturbation theory (ChPT) version of the eight independent B (\to) (B^{\prime}π) weak (ΔI) = 1/2 amplitudes containing considerably more than eight low-energy weak constants in one-loop order.
Possible CP violating effects in $Z\rightarrow$ 3 jet decays are investigated. The analysis assumes the presence of CP violating $Zq\bar qG$ couplings. The contribution of these couplings to the $Z\rightarrow q\bar qG$ decay width is calculated for different cut algorithms, including nonzero quark masses. Various CP--odd observables are discussed and it is shown that their sensitivity can change significantly if one uses normalized or unnormalized momentum vectors for their construction. Optimal observables are proposed which allow to measure the new couplings simultaneously.
We present an update of neutral Higgs boson decays into bottom quark pairs in the minimal supersymmetric extension of the Standard Model. In particular the resummation of potentially large higher-order corrections due to the soft SUSY breaking parameters A_b and mu is extended. The remaining theoretical uncertainties due to unknown higher-order SUSY-QCD corrections are analyzed quantitatively.
The recent results from Belle of the $τ^-\toν_τπ^-e^+e^-$ analysis has incentivated us to make a reanalysis of a former work where the Structure Dependent parts are obtained using Resonance Chiral Theory. Here we rely on the same theory accounting for effects that explicitly break such symmetry. A motivation is the involved $Wπγ^\star$ vertex, utterly relevant in computing $τ^- \to ν_τπ^-$ radiative corrections.
We update the extraction of |Vub| from exclusive semileptonic B to pi decays, combining experimental partial branching fraction information with theoretical form factor calculations, using the recently revised HPQCD results for the form factors f_+ and f_0. We use Omnes representations to provide the required parametrisations of the form factors. The extracted value is 10^3 |Vub| = 3.47+/-0.29+/-0.03, in striking agreement with |Vub| extracted using all other inputs in CKM fits and showing some disagreement with |Vub| extracted from inclusive semileptonic B to pi decays.
One-loop contributions to the decay $H\rightarrow ν_l\barν_lγ$ with $l=e, μ, τ$ within standard model framework are revisited in this paper. We derive two representations for the form factors in this calculation. As a result, the computations are not only checked numerically by verifying the ultraviolet finiteness of the results but also confirming the ward identity of the amplitude. We find that the results are good stability with varying ultraviolet cutoff parameters as well as satisfy the ward identity. In phenomenological results, all the physical results are examined with the present inpu…
In this work we compute the leading logarithmic corrections to the b -> s gamma decay in a dimensional scheme which does not require any definition of the gamma5 matrix. The scheme does not exhibit unconsistencies and it is therefore a viable alternative to the t'Hooft Veltman scheme, particularly in view of the next-to-leading computation. We confirm the recent results of Ciuchini et al.
The rare $π^0 \to e^+e^-$ and $η\to μ^+μ^-$ decays are calculated in different schemes, which are seen to be essentially equivalent to and produce the same results as conventional Vector-Meson Dominance. We obtain the theoretical predictions $B(π^0 \to e^+e^-) = (6.41 \pm 0.19)\times 10^{-8}$ and $B(η\to μ^+μ^-) = (1.14 +0.06 -0.03) \times 10^{-5}$ in agreement with recent experimental data.
The inclusive decay rate b to ccs is enhanced considerably due to perturbative QCD corrections. We recalculate the dominant part of the NLO-QCD corrections, because they cannot be reconstructed from the literature and we give the full expressions in this paper. Further we include some previously neglected corrections originating from penguin diagrams. Combined with the impressive progress in the accurate determination of input parameters like charm quark mass, bottom quark mass and CKM parameters, this enables us to make a very precise prediction of the corresponding branching ratio Br (b to c…
From the $0^{++}$ glueball candidate we argue that the $1^{--}$ glueball $O$ to be near in mass to $J/ψ$. This is supported by the recent null search for $ψ^\prime \to ρπ, K^*\bar K$, while absence of distortion in the energy scan of $J/ψ\to ρπ$ indicates that $Γ_O \gg Γ_{J/ψ}$. $O$ may also play a role in the OZI violating $\bar p p \to ϕγ, ϕπ$ production puzzle.
Motivated by the recent experimental observation of exclusive chi_c events at the Tevatron, we revisit earlier studies of central exclusive scalar chi_c0 meson production, before generalising the existing formalism to include chi_c1 and chi_c2 mesons. Although chi_c0 production was previously assumed to be dominant, we find that the chi_c1 and chi_c2 rates for the experimentally considered chi_c -> J/psi gamma -> mu+ mu- gamma decay process are in fact comparable to the chi_c0 rate. We have developed a new Monte Carlo event generator, SuperCHIC, which models the central exclusive production of…
We have calculated the decay amplitude for the process $K_{S}$ $\to$ $γγ$ at one loop order in chiral perturbation theory. As a new improvement we have included the weak mass term which is only relevant for processes with external fields in the final state. This term was ignored in earlier publications for this decay. We find that the inclusion of $G_{8}^{\prime}$ brings the theoretical decay rate into a good agreement with experiment.
We examine effects of final state interactions (FSI) in kaon decays using a new scheme without the Omnes function, and show that while Delta I=1/2 rule is impossible to be explained in terms of FSI alone, $ε'/ε\sim 16.5\times 10^{-4}$ is obtained through FSI, if the calculation is concerned only with the CP-violating parts. The pi-pi contribution to the m_L-m_S mass difference is shown to be about 0.14, if the sizes of the CP conserving amplitudes A_0 and A_2 are correctly given.
We evaluate the rare radiative kaon decays K_{L,S} -> 3 gamma. Applying the requirements of gauge invariance and Bose symmetry, we derive a general form of the decay amplitude, including both parity-conserving and parity-violating contributions. We employ a chiral-Lagrangian approach combined with dimensional analysis arguments to estimate the branching ratios of these decays in the standard model, obtaining values as large as B(K_L -> 3 gamma) ~ 1 x 10^{-14} and B(K_S -> 3 gamma) ~ 2 x 10^{-17}, which exceed those found previously by a few orders of magnitude. Measurements on the branching ra…
We reexamine critically the chiral expansion for the baryon magnetic moments including the contributions from loops which involve intermediate octet and decuplet baryons. We find that, contrary to some claims, the nonanalytic loop contributions of orders $m_s^{1/2}$ and $m_s ln m_s$ are of the same general size because of large coupling factors for the latter, and that the decuplet contributions are as large as the octet contributions and must be included in a consistent calculation. There is no clear evidence of the convergence of the chiral series. The adequacy of the theory will not be esta…
We rederive here in a simple and transparent way the master formula for the dominant part of large relativistic corrections to the positronium decay rate.
Recently LHCb experiments confirmed the findings of the two $P_c$ states in the $Λ_b^0 \to J/ψp π^-$ decays. In the present work, we investigate both the $Λ_b^0 \to J/ψK^- p$ and the $Λ_b^0 \to J/ψp π^-$ decays, continuing the investigations of our former works on the interactions of $J/ψN$ with its coupled channels by considering the s-/u- channel contributions. We obtain consistent results of the line-shape of the $J/ψN$ invariant mass distribution with the LHCb experiments, and favour the $P_c (4450)$ state as a $\bar{D}^* Σ_c$ bound state with $J=1/2^-$.
We revise the radiative corrections to double-Dalitz decays ($P\to\ell\bar{\ell}\ell'\bar{\ell}'$), completing the full next-to-leading order calculation in QED as compared to existing calculations. As a result, we find mild differences with respect to previous studies, that might be relevant for extracting information about the mesons transition form factors. The latter play an important role in determining the hadronic light-by-light contribution to the anomalous magnetic moment of the muon. Finally, we outline an ongoing extension of this work to the $e^+e^-\to e^+e^- P$ processes.
Non-leptonic hyperon weak decays are investigated in the SU(3) Skyrme model. We use a collective coordinate scheme, following the approach in which the symmetry breaking terms in the strong effective action are diagonalized exactly. To describe the weak interactions we use an octet dominated weak effective lagrangian that leads to a good description of the known 2πand 3πkaon decays. We show that the observed S-wave decays are reasonably well reproduced in the model. On the other hand, our calculated P-wave amplitudes do not agree with the empirical ones even though both pole and contact contri…
We present an updated discussion of $K\raπ\bar{l} l$ decays in a combined framework of chiral perturbation theory and Large--$N_c$ QCD, which assumes the dominance of a minimal narrow resonance structure in the invariant mass dependence of the $ \bar{l} l$ pair. The proposed picture reproduces very well, both the experimental $K^+\raπ^+ e^+ e^-$ decay rate and the invariant $e^+ e^-$ mass spectrum. The predicted Br$(K_S\raπ^0 e^+ e^-)$ is, within errors, consistent with the recently reported result from the NA48 collaboration. Predictions for the $K\raπμ^{+}μ^{-}$ modes are also obtained. We f…
In models where the breaking of lepton number is spontaneous a massless Goldstone boson, the Majoron ($J$), appears. We calculate the theoretically allowed range for the branching ratios of Majoron emitting charged lepton decays, such as Br($μ\to e J$) and Br($μ\to e J γ$), in a supersymmetric model with spontaneous breaking of R-parity. Br($μ\to eJ$) is maximal in the same region of parameter space for which the lightest neutralino decays mainly invisibly. A measurement of Br($μ\to eJ$) thus potentially provides information on R-parity violation complementary to accelerator searches. We also …
We calculate the branching ratios of the $K^+ \to π^0 l^+ ν_lγ(l = e, μ)$ decays, and the T-odd triple momenta correlations $ξ=\vec{q}\cdot[\vec{p}_l \times \vec{p}_π]/M^3_K$, due to the electromagnetic final state interaction, in these processes. The contributions on the order of $ω^{-1}$ and $ω^0$ to the corresponding amplitudes are treated exactly. For the branching ratios, the corrections on the order of $ω$ are estimated and demonstrated to be small. We compare the results with those of other authors. In some cases our results differ considerably from the previous ones.
The rare decays of mesons are higher order effects in weak interactions. The main contributions to such decay processes are from the Z-penguin, the photonpenguin and the box diagram. At the quark level, these contributions are well known. However, when considering the corresponding physical hadronic processes, a knowledge of how hadronic states are expressed in terms of quarks. In this paper, we suggest a simplistic way to relate the quark level process to the hadronic process. For simplicity, we consider here only the decays of pseudoscalar mesons. The meson-quark coupling is described in ter…
I present new results for the Standard-Model predictions of the differential decay rates for $H\to \ell^{+} \ell^{-} γ$, where $\ell=e, μ$, and the forward-backward asymmetries defined in terms of the flight direction of the photon corresponding to the lepton momenta. The results dependend on the cuts on energies and invariant masses of the final state particles. For standard choices of these cuts the branching ratios $B(H\to e \bar e γ)=5.8\cdot 10^{-5}$ and $B(H\to μ\bar μγ)=6.4\cdot 10^{-5}$ as well as the forward-backward asymmetries $\mathcal{A}^{(e)}_{\text{FB}}=0.343$ and $\mathcal{A}^{…
The amplitude of the Dalitz decay pi0 -> e+ e gamma is studied and its model-independent properties are discussed in detail. A calculation of radiative corrections is performed within the framework of two-flavour chiral perturbation theory, enlarged by virtual photons and leptons. The lowest meson dominance approximation, motivated by large N\_C considerations, is used for the description of the pi0 - gamma* - gamma* transition form factor and for the estimate of the NLO low energy constants involved in the analysis. The two photon reducible contributions is included and discussed. Previous ca…
We reexamine contributions of higher $K$-resonances to the radiative rare decays $b\rar sγ$ in the limit where both $b$- and $s$-quark are considered heavy. Using the non-relativistic quark model, and the form factor definitions consistent with the HQET covariant trace formalism, we find significant disagreement with previous work which also used heavy quark symmetry, and excellent agreement with experimental results. In particular, the two largest fractions of the inclusive $b\rar sγ$ branching ratio are found to be $(16.8\pm 6.4)\%$ for $B\rar K^{*}(892)γ$ and $(6.2\pm 2.9)\%$ for $B\rar K_{…
We estimate nonfactorizable 1/$N_c$ contributions in the $K\rightarrow 2π$ amplitudes using the approach proposed in our previous work. It is demonstrated that for the conventional (nonpenguin) operators these contributions are close in magnitude to factorizable $1/N_c$ parts and have the opposite sign. Thus, an approximate rule of discarding $1/N_c$ corrections in $K\rightarrow 2π$ decays is theoretically confirmed. As a result we find an extra suppression of the matrix element of $O_4$ ($ΔI=3/2$) and an extra enhancement of the matrix element of $O_1$ ($ΔI=1/2$). The parameter $B$ describing…
In view of the recent experimental developments on the experimental side in the $η\to π^0 γγ$ decay, and the fact that the Particle Data Group in the on line edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of \cite{eta}, a reevaluation of the decay width of the $η$ in this channel has been done, reducing its uncertainty by almost a factor of two. The new input of the PDG is used and invariant mass distributions and total widths are compared with the most recent results from AGS, MAMI and preliminary ones of KL…
Motivated by recent experimental results and ongoing measurements, we review the chiral perturbation theory prediction for radiative Ke3 decays (neutral kaons). Special emphasis is given on the stability of the inner bremsstrahlung-dominated relative branching ratio vs. the Ke3 form factors, and on the separation of the structure dependent amplitude in differential distributions over the phase space. For the structure dependent terms, an assessment of the order p^6 corrections is given. In particular, a full next-to-leading order calculation of the axial component is performed. The experimenta…
The one-loop calculation of the amplitude for the Higgs decay H-->γγ due to virtual W's in the unitary gauge is presented. As the Higgs does not directly couple to the massless photons, the one-loop amplitude is finite. The calculation is performed in a straightforward way, without encountering divergences. In particular, artifacts like dimensional regularization are avoided. This is achieved by judiciously routing the external momenta through the loop and by combining the integrands of the amplitudes before carrying out the integration over the loop momentum. The present result satisfies the …
We critically reexamine the prospects for the observation of the $ΔL=2$ lepton-number-violating process $\eeWW$ using the $e^-e^-$ option of a high-energy $e^+e^-$ collider (NLC). We find that, except in the most contrived scenarios, constraints from neutrinoless double beta decay render the process unobservable at an NLC of $\sqrt{s}<2$ TeV. Other $ΔL=2$ processes such as $\ggllww$, $\egnllw$, $\eennll$ ($\ell=μ,τ$), and $\egeww$, which use various options of the NLC, require a $\sqrt{s}$ of at least 4 TeV for observability.
We present a calculation of the width for $χ_{cJ}\rightarrow e^{+}e^{-}$ decay. The amplitude of the process is computed within the NRQCD framework. The leading-order contribution is described by two terms associated with the two different integration domains in the electromagnetic loop describing two-photon annihilation of the heavy quark-antiquark pair. The corresponding operators are defined in the framework of NRQCD. The matrix element of one of these operators describes a configuration with an ultrasoft photon and can be associated with the higher Fock state of the heavy meson. In order t…
We present an on-shell renormalization scheme for the neutralino and chargino mass matrices for two R-parity violating models, namely bilinear R-parity violation and the munuSSM with one right-handed neutrino superfield. We discuss in both models how to obtain neutrino masses and mixing angles correctly as well as differences to the existing DRbar calculations. Both models predict correlations between neutrino mixing angles and ratios of R-parity violating decays such as neutralino_1 -> l W which can be tested for example at the LHC. We point out that there are cases where one has to include t…
The value of the $η- η'$ mixing angle $θ_P$ is phenomenologically deduced from a rather exhaustive and up-to-date analysis of data including strong decays of tensor and higher-spin mesons, electromagnetic decays of vector and pseudoscalar mesons, $J/ψ$ decays into a vector and a pseudoscalar meson, and other transitions. A value of $θ_P$ between $-17^\circ$ and $-13^\circ$ is consistent with all the present experimental evidence and the average $θ_P=-15.5^\circ\pm 1.3^\circ$ seems to be favoured.
We discuss the systematic decomposition of all dimension-7 (d=7) lepton number violating operators. These d=7 operators produce momentum enhanced contributions to the long-range part of the neutrinoless double beta decay amplitude and thus are severely constrained by existing half-live limits. In our list of possible models one can find contributions to the long-range amplitude discussed previously in the literature, such as the left-right symmetric model or scalar leptoquarks, as well as some new models not considered before. The d=7 operators generate Majorana neutrino mass terms either at t…
We perform a comprehensive analysis of the decays of charginos and neutralinos in the Minimal Supersymmetric Standard Model where the neutralino $χ_1^0$ is assumed to be the lightest supersymmetric particle. We focus, in particular, on the three-body decays of the next-to-lightest neutralino and the lightest chargino into the lightest neutralino and fermion-antifermion pairs and include vector boson, Higgs boson and sfermion exchange diagrams, where in the latter contribution the full mixing in the third generation is included. The radiative corrections to the heavy fermion and SUSY particle m…
Two-pion transitions in charmonium and bottomonium are considered with the leading relativistic effects taken into account. The contribution of the chromo- magnetic interaction of the charmed quarks to the amplitude of the decay $ψ(2S) \to ππJ/ψ$ is estimated from the available data. This contribution is enhanced by a factor of three in the decay $η_c(2S) \to ππη_c$ and should produce a noticeable modification of the rate and the spectrum in the latter decay. It is argued that the peculiar observed spectrum in the decay $Υ(3S) \to ππΥ$ arises due to a dynamical suppression of the leading nonre…
We reanalyse the magnetic moments of the baryon octet, decuplet, and antidecuplet within the framework of the chiral quark-soliton model, with SU(3) symmetry breaking taken into account. We consider the contributions of the mixing of higher representations to the magnetic moment operator arising from the SU(3) symmetry breaking. Dynamical parameters of the model are fixed by experimental data for the magnetic moments of the baryon octet and from the masses of the octet, decuplet and of $Θ^{+}$. The magnetic moment of $Θ^{+}$ depends rather strongly on the pion-nucleon sigma term and reads $-1.…
We present new calculations of the differential decay rates for $H\to \ell^+\ell^- γ$ with $\ell=e$ or $μ$ in the Standard Model. The branching fractions and forward-backward asymmetries, defined in terms of the flight direction of the photon relative to the lepton momenta, depend on the cuts on energies and invariant masses of the final state particles. For typical choices of these cuts we find the branching ratios $B(H\to e \bar e γ)=5.8\cdot 10^{-5}$ and $B(H\to μ\bar μγ)=6.4\cdot 10^{-5}$ and the forward-backward asymmetries $\mathcal{A}^{(e)}_{\text{FB}}=0.343$ and $\mathcal{A}^{(μ)}_{\te…
We examine, in a number of Standard Model extensions, whether the decays $A \to WW/ZZ$ of a neutral pseudoscalar (Higgs) resonance can have branching ratios at the percent level and we determine the possible size of $B(A \to WW/ZZ)$ relative to the respective branching ratios of a scalar boson $H$. The branching ratios of the these decay modes and the total widths $Γ_A$, $Γ_H$ are computed in the minimal supersymmetric extension of the SM, in a type-II two-Higgs doublet extension (2HDM), in a 2HDM with 4 chiral fermion generations, in a 2HDM with additional heavy vector-like quarks, and in a t…
The $\b$ decay does not receive any nonspectator contributions and hence its theoretical calculation is relatively clean. Two different methods are employed for the study of $\b$. In the first method, both $b$ and $s$ quarks are treated as heavy and leading $1/m_s$ as well as $1/m_b$ corrections are included. The branching ratio and the asymmetry parameter $α$ are found to be $(0.7-1.5)\times 10^{-3}$ and $0.18$, respectively. In the second method, only the $b$ quark is treated as heavy. The prediction of the decay rate is very sensitive to the choice of the $q^2$ dependence for form factors. …
We present an improved calculation of $B\to$ light vector form factors from light-cone sum rules, including one-loop radiative corrections to twist-2 and twist-3 contributions, and leading order twist-4 corrections. The total theoretical uncertainty of our results at zero momentum transfer is typically 10% and can be improved, at least in part, by reducing the uncertainty of hadronic input parameters. We present our results in a way which details the dependence of the form factors on these parameters and facilitates the incorporation of future updates of their values from e.g. lattice calculat…
Branching fractions and CP-violating asymmetries of charmless $\bar B_s\to PP, VP, VV$ decays (P and V denoting pseudoscalar and vector mesons, respectively) are re-examined in the framework of QCD factorization (QCDF). We take into account subleading power corrections to the penguin annihilation topology and to color-suppressed tree amplitudes that are crucial for resolving the CP puzzles and rate deficit problems with penguin-dominated two-body decays and color-suppressed tree-dominated $π^0π^0$ and $ρ^0π^0$ modes in the $B_{u,d}$ sector. Many of the $B_s\to h_1h_2$ decays can be related to …
We revisit the effect of CP violating anomalous top-quark couplings in $t\bar{t}$ production and decay. We consider $t\bar{t}$ production through gluon fusion (and light $q{\bar q}$ annihilation) followed by top-quark decay into $bW$ or $b\ellν$. We find explicit analytic expressions for all the triple products generated by the anomalous couplings that fully incorporate all spin correlations. Our results serve as a starting point for numerical simulations for the LHC.
We analyze and compute, within a number of standard model (SM) extensions, the cross sections $σ_{A\to VV'}$ for the production of a heavy neutral pseudoscalar Higgs boson/spin-zero resonance at the LHC and its subsequent decays into electroweak gauge bosons. For comparison we calculate also the corresponding cross sections for a heavy scalar. The SM extensions we consider include a type-II two-Higgs doublet model (2HDM), a 2HDM with 4 chiral fermion generations, the minimal supersymmetric extension of the SM (MSSM), and top-color assisted technicolour models. Presently available phenomenologi…
The anti-kaon nucleon system close to threshold is analyzed in view of the new accurate DEAR kaonic hydrogen data. The calculations are performed using chiral SU(3) effective field theory in combination with non-perturbative schemes based on coupled channels. Several variants of such approaches are compared with experimental data and the differences in the results are discussed. Coulomb and isospin breaking effects turn out to be important and are both taken into account. The pole structure of the Lambda(1405) resonance close to the anti-kaon nucleon threshold is critically examined.
The possibility of the unexplained Kolar events, recorded in the 70's and 80's, being due to the decays of dark matter particles of mass in the range of 5--10 GeV is pointed out.
We present a re-analysis of the decay $\bsgamma$ in the Minimal Supersymmetric Standard Model with radiatively induced breaking of $SU(2) \times U(1)$. We extend this analysis to regions of the supersymmetric parameter space wider than those previously studied. Results are explicitly presented for $m_t=150\GeV$. We emphasize the consequences for future searches of charged Higgs and charginos from a measurement of the branching ratio for this decay compatible with the Standard Model prediction. In spite of the strong sensitivity of this decay to the effects of supersymmetry, we find that, at th…
The extension of Majorana neutrino mass mechanism of the neutrinoless double-beta decay ($0νββ$) with the inclusion of right-handed leptonic and hadronic currents is revisited. While only the exchange of light neutrinos is assumed, the $s_{1/2}$ and $p_{1/2}$-states of emitted electrons as well as recoil corrections to the nucleon currents are taken into account. Within the standard approximations the decay rate is factorized into a sum of products of kinematical phase-space factors, nuclear matrix elements and the fundamental parameters that characterize the lepton number violation. Unlike in…
The calculation of perturbative corrections to the spectral moments observable in hadronic $τ$ decays is reconsidered. The exact order-$α_s^3$ results and the resummation procedure of Le~Diberder and Pich are compared with a partial resummation of the perturbative series based on the analysis of so-called renormalon chains. The perturbative analysis is complemented by a model-independent description of power corrections. For the contributions of dimension four and six in the OPE, it is demonstrated how infrared renormalon ambiguities in the definition of perturbation theory can be absorbed by …
I revisit here the decoupling theorem in top-quark productions/decays, which states that the angular distribution of any final-particle produced in those processes does not depend on any possible nonstandard top-quark decay interactions at their leading order when certain conditions are satisfied. Towards a simple, intuitive and visual understanding of this theorem, I will study to what extent we could explain why such a theorem holds without relying on any specific/detailed calculations.
The ILL experiment, one of the "reactor anomaly" experiments, is re-examined. ILL's baseline of 8.78 m is the shortest of the short baseline experiments, and it is the experiment that finds the largest fraction of the electron anti-neutrinos disappearing -- over 20%. Previous analyses, if they do not ignore the ILL experiment, use functional forms for chisquare which are either totally new and unjustified, are the magnitude chi-square (also termed a "rate analysis"), or utilize a spectral form for chi-square which double counts the systematic error. We do an analysis which utilizes the standar…
We critically re-examine the case for and against a sizeable right-handed component in the $b\to c$ charged current coupling with a strength $ξ$ relative to the conventional left-handed current. Using data from CLEO on the decay $B\to D^*\ell ν$, as well as our knowledge of $V_{cb}$ extracted from both inclusive and exclusive processes, we are able to determine the presently allowed parameter space for $ξ$ via HQET. We then identify several observables which could be measured at $B$ factories to either strengthen these constraints or otherwise observe right-handed currents. This parameter spac…
