arXiv subjects

Markus Finkemeier

Publications and source records attributed to Markus Finkemeier.

17 recordsLinked to original sources

arXiv2026

Comment on "Radiative corrections to tau -> pi(K) nu_tau[gamma]: A reliable new physics test"

Arroyo-Ure\~na, Hern\'andez-Tom\'e, L\'opez-Castro, Roig, and Rosell (AHLRR) take the structure-dependent (SD) amplitude for $\tau \to P \nu_\tau \gamma$ from the resonance chiral theory result of Guo and Roig (GR10), obtaining $\delta r_{SD} = +0.15\%$ in the pion channel. The convention dictionary in footnote 2 of GR10, repeated in footnote 1 of AHLRR, has the wrong sign in its axial entry: the printed amplitudes imply $F_A^{DF} = -2\sqrt{2}\, m_P F_A^{GR}$, not $+2\sqrt{2}\, m_P F_A^{GR}$. With the corrected dictionary, the GR10 amplitude agrees with the $O(p^4)$ chiral prediction in the axial sector but carries the opposite sign to the chiral anomaly in the vector sector; the relative sign fixed in the Decker-Finkemeier addendum is confirmed in both sectors. The identification in footnote 6 of AHLRR of their value with the pre-addendum result rests on the erroneous dictionary and does not hold. The numerical impact is small: $\delta r_{SD}$ shifts from $+0.150\%$ to $+0.146\%$ in the pion channel and from $+0.18\%$ to about $+0.16\%$ in the kaon channel.

hep-ph↗

arXiv1997

The Chirally Normalized Vector Meson Dominance Model and Semihadronic Tau Decays

We discuss and test the assumptions of the chirally normalized vector meson dominance model (CN-VMD), as it is used for tau decays. We compare the CN-VMD amplitudes with those using on-shell couplings, derived directly from experimental data. We discuss in detail the $3π$, $K K π$ and $2π$ final states. We suggest that the true values for the $K_1$ widths might be larger than those quoted in the Review of Particle Physics.

hep-ph↗

arXiv1997

Reparameterization Invariance Revisited

Reparameterization invariance, a symmetry of heavy quark effective theory, appears in different forms in the literature. The most commonly cited forms of the reparameterization transformation are shown to induce the same constraints on operators that do not vanish under the equation of motion to order $1/m^2$, and to be related by a redefinition of the heavy quark field. We give a new, very straightforward proof that that the reparameterization invariance constraints apply to all orders in $α_s$ under matching to full QCD and renormalization-group running, at least up to and including $O(1/m^2)$.

hep-ph↗

arXiv1996

Theoretical Aspects of $τ\to K h (h) ν_τ$ Decays and Experimental Comparisons

Predictions for decay rates and distributions for $τ$ decays into final states with kaons are discussed and compared with recent measurements. Special emphasis is put on new constraints for the vector current contribution in the $KKπ$ decay modes. For the $Kππ$ modes, disagreements with the experimental results can be traced back to the $K_1$ widths.

hep-ph↗

arXiv1996

Structure Functions in Semihadronic Tau Decays

We review a variety of topics related to hadronic structure functions in exclusive semihadronic tau decays. We introduce the concept of structure functions and summarize the most important concepts. We then calculate the decay $τ\to 3 πν_τ$ for very small hadronic invariant mass to one loop in Chiral Perturbation Theory. New interesting features emerge with respect to the known results at tree level, in particular for the structure functions $w_D$ and $w_E$. We discuss the prospects for experimental verification of our predictions. Finally, we discuss various issues at higher $Q^2$, related to hadronic resonance physics. Here we consider $2π$, $πK$, $3 π$, $K πK$ and $πK π$ hadronic final states.

hep-ph↗

arXiv1996

Renormalizing the heavy quark effective field theory Lagrangian to order 1/m^2

The heavy quark effective field theory Lagrangian is renormalized to order 1/m^2. Our technique eliminates operators that vanish by the equation of motion by continuously redefining the heavy quark fields during renormalization. It is consequently only necessary to calculate the running of the operators that do not vanish by the equation of motion. Our results are found to be consistent with reparameterization invariance.

hep-ph↗

arXiv1996

The Scalar Contribution to $τ\to K πν_τ$

We consider the scalar form factor in $τ\to Kπν_τ$ decays. It receives contributions both from the scalar resonance $K_0^*(1430)$ and from the scalar projection of off-shell vector resonances. We construct a model for the hadronic current which includes the vector resonances $K^*(892)$ and $K^*(1410)$ and the scalar resonance $K_0^*(1430)$. The parameters of the model are fixed by matching to the $O(p^4)$ predictions of chiral perturbation theory. Suitable angular correlations of the $Kπ$ system allow for a model independent separation of the vector and scalar form factor. Numerical results for the relevant structure functions are presented.

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arXiv1995

Decay Rates, Structure Functions and New Physics Effects in Hadronic Tau Decays

Hadronic decays rates of the $τ$ lepton into multi meson final states are presented. The structure of the hadronic matrix elements for various decay modes is discussed. The formalism of structure functions allows for a detailed test of these matrix elements. Various correlations are discussed which are sensitive to possible CP violation and new physics effects in the decay modes.

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arXiv1995

Tau Decays into Kaons

Predictions for semi-leptonic decay rates of the tau lepton into two and three meson final states with one or two kaons are derived, including a discussion of K_S pi- K_S, K_L pi- K_L and K_S pi- K_L. The hadronic matrix elements are expressed in terms of form factors, which can be predicted by chiral Lagrangians supplemented by informations about all possible low-lying resonances in the different channels. Isospin symmetry relations among the different final states are carefully taken into account. The calculated branching ratios are compared with measured decay rates where data are available.

hep-ph↗

arXiv1995

Radiative Corrections to pi_{l2} and K_{l2} Decays

We report on our reexamination of the radiative corrections to $π_{l2}$ and $K_{l2}$ decays. We perform a matching calculation, using a specific model with vector meson dominance in the long distance part and the parton model in the short distance part. By considering the dependence on the matching scale and on the hadronic parameters, and by comparing with model independent estimates, we scrutinize the model dependence of the results. For the pseudoscalar meson decay constants, we extract the values $f_π= (92.1 \pm 0.3)\,\mbox{MeV}$ and $f_K = (112.4 \pm 0.9) \, \mbox{MeV}$. For the ratios $R_π$ and $R_K$ of the electronic and muonic decay modes, we predict $R_π= (1.2354 \pm 0.0002) \cdot 10^{-4}$ and $R_K = (2.472 \pm 0.001) \cdot 10^{-5}$.

hep-ph↗

arXiv1995

Radiative Corrections to $\pi_{l2}$ and $K_{l2}$ Decays

We reexamine radiative corrections to $\pi_{l2}$ and $K_{l2}$ decays. We perform a matching calculation, including vector and axial vector resonances as explicit degrees of freedom in the long distance part. By considering the dependence on the matching scale and on the hadronic parameters, and by comparing with model independent estimates, we scrutinize the model dependence of the results. For the pseudoscalar meson decay constants, we extract the values f_pi = (92.1 \pm 0.3) MeV and f_K = (112.4 \pm 0.9) MeV. For the ratios R_pi and R_K of the electronic and muonic decay modes, we predict R_pi = (1.2354 \pm 0.0002) 10^{-4} and R_K = (2.472 \pm 0.001) 10^{-5}.

hep-ph↗

arXiv1994

Radiative Corrections to K_l2 decays

We consider $K_{l2}$ decays to the order $O(α)$. We perform a matching calculation, using a specific model with vector meson dominance in the long distance part and the parton model in the short distance part. By considering the dependence on the matching scale and on the hadronic parameters, and by comparing with the leading model independent predictions, we scrutinize the model dependence of the results.

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arXiv1994

Radiative Corrections to the Decay $τ\toπν_τ$

We have calculated the radiative corrections to the decay $τ\to π(K) ν_τ$, taking to account internal bremsstrahlung and structure dependent radiation in the radiative decay and point meson, hadronic structure dependent and short distance contributions in the virtual corrections. We display the spectra of the photon energy and of the pion-photon invariant mass in the decay $τ\toπν_τγ$ and compare with the PHOTOS Monte-Carlo. Our result for the radiative correction to the ratio $Γ(τ\toπν_τ(γ))/ Γ(π\toμν_μ(γ))$ is $δR_{τ/π} = \left(0.16 \pm 0.14 \right) \%$ and for the ratio $Γ(τ\to Kν_τ(γ))/ Γ(K\toμν_μ(γ))$, we obtain $δR_{τ/K } = \left(0.90 \pm 0.22 \right) \%$.

hep-ph↗

arXiv1994

Short and Long Distance Effects in the Decay $τ\to πν_τ(γ)$

We calculate the radiative corrections to the decays $τ\to M ν_τ$ and $π\to l ν_ł$, where the meson $M$ is $M=π$ or $K$ and the lepton $l$ is $l = e$ or $μ$. We perform a complete calculation, which includes internal bremsstrahlung and structure dependent radiation in the radiative decays and point meson, hadronic structure dependent and short distance contributions in the virtual corrections. Our result for the radiative correction to the ratio $Γ(τ\toπν_τ(γ))/ Γ(π\toμν_μ(γ))$ is $δR_{τ/π} = \left(0.16_{\T - 0.14}^{\T+0.09}\right) \%$. For the ratio $Γ(τ\to Kν_τ(γ)) / Γ(K\to μν_μ(γ))$, we obtain $δR_{τ/K } = \left(0.90_{\T - 0.26}^{\T + 0.17}\right) \%$. For completeness we have also calculated the ratio of the electronic and muonic decay modes of the pion.

hep-ph↗

arXiv1994

Addendum To Our Paper: "Radiative Tau Decays With One Pseudoscalar Meson"

In a previous paper we have calculated the decay $τ\toπν_τγ$. We used a given relative sign between the internal bremsstrahlung and the structure dependent radiation, which has been used by several other authors before. However, we believe that there are good arguments why the opposite sign is the physical one. We briefly discuss these arguments and then investigate how the predictions for the decay $τ\toπν_τγ$ are affected by this sign.

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arXiv1993

Pseudoscalar Mass Effects in Decays of Taus with Three Pseudoscalar Mesons

We study the effects of non-vanishing pseudoscalar masses in $τ$ decays into three mesons. The hadronic matrix elements are obtained by using the generalized structure of the chiral currents with nonvanishing pseudoscalar masses and implementing the low-lying resonances in the different channels. We demonstrate that suitable angular distributions are sensitive to the mass effects in the chiral Langrangian. Numerical results for the rele\-% vant structure functions are given for the decay modes $τ\rightarrow νπ^-π^-π^+$, $νK^-π^-π^+$ and $νK^-π^-K^+$.

hep-ph↗

arXiv1993

Radiative Corrections to the decay tau -> pi (K) nu_tau

We have calculated the O(alpha) radiative corrections to the tau decay tau -> pi (K) nu, taking into account both the point meson contribution and the structure dependent radiation. We find for the ratio Gamma(tau -> pi nu (gamma)) / Gamma(pi -> mu nu (gamma)) a radiative correction of + 1.2% and for Gamma(tau -> K nu (gamma)) / Gamma(K -> mu nu (gamma)) one of + 2.0%. We compare our results with an earlier estimation and with experimental data.

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