4,237 research outputs found
The isospin symmetry breaking effects in decays
The Fermi-Watson theorem is generalized to the case of two coupled channels
with different masses and applied to final state interaction in
decays. The impact of considered effect on the phase of the scattering
is estimated and shown that it can be crucial for scattering lengths extraction
from experimental data on decays
Empirical parameterization of the K+- -> pi+- pi0 pi0 decay Dalitz plot
As first observed by the NA48/2 experiment at the CERN SPS, the \p0p0
invariant mass (M00) distribution from \kcnn decay shows a cusp-like anomaly
at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi
scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively,
has been recently reported. In the present work the Dalitz plot of this decay
is fitted to a new empirical parameterization suitable for practical purposes,
such as Monte Carlo simulations of K+- -> pi+- pi0 pi0 decays.Comment: 9 pages, 3 figures
Two-loop representations of low-energy pion form factors and pi-pi scattering phases in the presence of isospin breaking
Dispersive representations of the pi-pi scattering amplitudes and pion form
factors, valid at two-loop accuracy in the low-energy expansion, are
constructed in the presence of isospin-breaking effects induced by the
difference between the charged and neutral pion masses. Analytical expressions
for the corresponding phases of the scalar and vector pion form factors are
computed. It is shown that each of these phases consists of the sum of a
"universal" part and a form-factor dependent contribution. The first one is
entirely determined in terms of the pi-pi scattering amplitudes alone, and
reduces to the phase satisfying Watson's theorem in the isospin limit. The
second one can be sizeable, although it vanishes in the same limit. The
dependence of these isospin corrections with respect to the parameters of the
subthreshold expansion of the pi-pi amplitude is studied, and an equivalent
representation in terms of the S-wave scattering lengths is also briefly
presented and discussed. In addition, partially analytical expressions for the
two-loop form factors and pi-pi scattering amplitudes in the presence of
isospin breaking are provided.Comment: 57 pages, 12 figure
The electromagnetic effects in decay
The final state interaction of pions in decay allows one to obtain
the value of the isospin and angular momentum zero scattering length
.We take into account the electromagnetic interaction of pions and
isospin symmetry breaking effects caused by different masses of neutral and
charged pions and estimate the impact of these effects on the procedure of
scattering length extraction from decay.Comment: 8 pages,1 figur
Possibilities for Misinterpretation in ASV-Speciation Studies of Natural Waters
Die Probleme, die bei Speciesuntersuchungen von Spurenelementen mit Hilfe der Differentialpuls Anodic Stripping Voltammetrie auftreten, werden zu-sammenfassend dargestellt. Neben den bei der eigentlichen Bestimmung auftretenden Problemen, werden auch solche erwähnt, die mit der Probennahme sowie der Lagerung und Vorbehandlung der Proben in Zusammenhang stehen
Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation
A left-right symmetric model with two Higgs bi-doublet is shown to be a
consistent model for both spontaneous P and CP violation. The flavor changing
neutral currents can be suppressed by the mechanism of approximate global U(1)
family symmetry. We calculate the constraints from neural meson mass
difference and demonstrate that a right-handed gauge boson
contribution in box-diagrams with mass well below 1 TeV is allowed due to a
cancellation caused by a light charged Higgs boson with a mass range GeV. The contribution to can be suppressed from
appropriate choice of additional CP phases appearing in the right-handed
Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully
consistent with mass difference , and the mixing-induced CP
violation quantity , which is usually difficult for the
model with only one Higgs bi-doublet. The new physics beyond the standard model
can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published
versio
Search for direct CP-violation in K+- --> pi+-pi0pi0 decays
A search for direct CP-violation in K+- --> pi+-pi0pi0 decays based on 47.14
million events has been performed by the NA48/2 experiment at the CERN SPS. The
asymmetry in the Dalitz plot linear slopes A_g=(g^+ - g^-)/(g^+ + g^-) is
measured to be A_g=(1.8 +- 2.6).10^{-4}. The design of the experiment and the
method of analysis provide good control of instrumental charge asymmetries in
this measurement. The precision of the result is limited by statistics and is
almost one order of magnitude better than that of previous measurements by
other experiments.Comment: 14 page
Observation of the rare decay K_S -> pi^0mu^+mu^-
A search for the decay K_S -> pi^0mu^+mu^- has been made by the NA48/1
Collaboration at the CERN SPS accelerator. The data were collected during 2002
with a high-intensity K_S beam. Six events were found with a background
expectation of 0.22^+0.18_-0.11 event. Using a vector matrix element and unit
form factor, the measured branching ratio is B(K_S ->
pi^0mu^+mu^-)=[2.9^+1.5_-1.2(stat)+/-0.2(syst)]x10^{-9}.Comment: 19 pages, 8 figures, 4 tables. To be published in Physics Letters
Isospin breaking in Kl4 decays
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.Comment: 33 pages, 12 figure
- …