Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userIsospin Breaking in $K_{ell 4}$ Decays of the Charged Kaon
124
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The charged $K_{ell 4}$ decay, $K^+topi^+pi^-ell^+ u_{ell}$ is studied in the framework of chiral perturbation theory based on the effective Lagrangian including mesons, photons, and leptons. We give analytic expressions for the two vectorial form factors, $f$ and $g$, calculated at one-loop level in the presence of Isospin breaking effects. These expressions may then be used to disentangle the Isospin breaking part from the measured form factors and hence improve the accuracy in the determination of $pipi$ scattering parameters from $K_{ell 4}$ experiments.
rate research
Read More
In the presence of photons, the neutral $K_{ell 4}$ decay, $K^0topi^0pi^-ell^+ u_ell$, can be parameterized in terms of three vectorial, one anomalous, and one tensorial form factors. We present here analytic expressions of two vectorial form factors, $f$ and $g$, calculated at one-loop level in the framework of chiral perturbation theory based on the effective Lagrangian including mesons, photons, and leptons. These expressions may then be used to disentangle the Isospin breaking part from the measured form factors and hence improve the accuracy in the determination of $pipi$ scattering parameters from $K_{ell 4}$ experiments.
We use chiral perturbation theory to evaluate the scattering amplitude for the process Pi^+ K^- to Pi^+ K^- at leading and next-to-leading orders in the chiral counting and in the presence of isospin breaking effects. We also discuss the influence of the latter on the combination of the S-wave Pi K scattering lengths which is relevant for the 2S - 2P energy levels shift of K Pi atoms.
Data on Ke4 decays allow one to extract experimental information on the elastic pi pi scattering amplitude near threshold, and to confront the outcome of the analysis with predictions made in the framework of QCD. These predictions concern an isospin symmetric world, while experiments are carried out in the real world, where isospin breaking effects - generated by electromagnetic interactions and by the mass difference of the up and down quarks - are always present. We discuss the corrections required to account for these, so that a meaningful comparison with the predictions becomes possible. In particular, we note that there is a spectacular isospin breaking effect in Ke4 decays. Once it is taken into account, the previous discrepancy between NA48/2 data on Ke4 decays and the prediction of pi pi scattering lengths disappears.
We evaluate the size of isospin breaking corrections to form factors $f$ and $g$ of the $K_{ell 4}$ decay process $K^+topi^+pi^-ell^+ u_{ell}$ which is actually measured by the extended NA48 setup at CERN. We found that, keeping apart the effect of Coulomb interaction, isospin breaking does not affect modules. This is due to the cancelation between corrections of electromagnetic origin and those generated by the difference between up and down quark masses. On the other hand, electromagnetism affects considerably phases if the infrared divergence is dropped out using a minimal subtraction scheme. Consequently, the greatest care must be taken in the extraction of $pipi$ phase shifts from experiment.
A novel approach to reconstruct inclusive $bar{B} to X_{s} ell^{+}ell^{-}$ decays is presented. The method relies on isopsin symmetry to extrapolate the semi-inclusive signature $X_{b}to K^{+} ell^{+}ell^{-} X$ to the fully inclusive rate in $B^{+}$ and $B^{0}$ decays. We investigate the possibility to measure branching fractions and other observables such as lepton universality ratios and $CP$ asymmetries. As a proof of concept, fast simulation is used to compare the $X_{b}to K^{+} ell^{+}ell^{-} X$ signature with a fully inclusive approach. Several experimental advantages are seen which have the potential to make measurements of inclusive $bar{B} to X_{s} ell^{+}ell^{-}$ decays tractable at a hadron collider.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
