497 research outputs found
Final state interaction in decay
Contrary to wide-spread opinion that the final state interaction (FSI)
enhances the amplitude , we argue that FSI does not increase
the absolute value of this amplitude.Comment: 9 page
Discrete Symmetries on the Light Front and a General Relation Connecting Nucleon Electric Dipole and Anomalous Magnetic Moments
We consider the electric dipole form factor, F_3(q^2), as well as the Dirac
and Pauli form factors, F_1(q^2) and F_2(q^2), of the nucleon in the
light-front formalism. We derive an exact formula for F_3(q^2) to complement
those known for F_1(q^2) and F_2(q^2). We derive the light-front representation
of the discrete symmetry transformations and show that time-reversal- and
parity-odd effects are captured by phases in the light-front wave functions. We
thus determine that the contributions to F_2(q^2) and F_3(q^2), Fock state by
Fock state, are related, independent of the fundamental mechanism through which
CP violation is generated. Our relation is not specific to the nucleon, but,
rather, is true of spin-1/2 systems in general, be they lepton or baryon. The
empirical values of the anomalous magnetic moments, in concert with empirical
bounds on the associated electric dipole moments, can better constrain theories
of CP violation. In particular, we find that the neutron and proton electric
dipole moments echo the isospin structure of the anomalous magnetic moments,
kappa^n ~ - kappa^p.Comment: 25 pages, 1 figure. Published version. Ref. adde
Loop-Less Electric Dipole Moment of the Nucleon in the Standard Model
We point out that the electric dipole moment of the neutron in the Standard
Model is generated already at tree level to the second order in the weak
interactions due to bound-state effects, without short-distance Penguin loops.
The related contribution has a regular nonvanishing chiral limit and does not
depend on the mass splitting between s and d quarks. We estimate it to be
roughly 10^(-31)e*cm and expect a more accurate evaluation in the future. We
comment on the connection between d_n and the direct CP-violation in D decays.Comment: 10 pages, 2 figure
Kaon semileptonic decay (K_{l3}) form factors from the instanton vacuum
We investigate the kaon semileptonic decay (K_{l3}) form factors within the
framework of the nonlocal chiral quark model from the instanton vacuum, taking
into account the effects of flavor SU(3) symmetry breaking. We also consider
the problem of gauge invariance arising from the momentum-dependent quark mass
in the present work. All theoretical calculations are carried out without any
adjustable parameter, the average instanton size (rho ~ 1/3 fm) and the
inter-instanton distance (R ~ 1 fm) having been fixed. We also show that the
present results satisfy the Callan-Treiman low-energy theorem as well as the
Ademollo-Gatto theorem. Using the K_{l3} form factors, we evaluate relevant
physical quantities. It turns out that the effects of flavor SU(3) symmetry
breaking are essential in reproducing the kaon semileptonic form factors. The
present results are in a good agreement with experiments, and are compatible
with other model calculations.Comment: 12 pages, 3 figures, submitted to PR
CP violation in decay
CP violation leads to a difference between the parameters and
describing the energy distributions of the charged pions produced in the and decays. We study the
difference as a function of the relative contributions from the
QCD-penguin and the electroweak-penguin diagrams. We find that the combination
of these contributions in is very similar to the corresponding
one defining the parameter in the decays. This
observation allows a determination of the value of , using data on
Recent results from the NA48 experiment at CERN: CP violation and CKM parameter Vus
Several recent results from the NA48 experiment are presented: a measurement
, search for CP violating phenomena in decays, and
a measurement of .Comment: A talk given at the 2007 Europhysics Conference on High Energy
Physics. 3 page
On CP-Odd Effects in K_L \to 2\pi and K^{\pm} \to \pi^{\pm} \pi^{\pm} \pi^{\mp} Decays Generated by Direct CP Violation
The amplitudes of the K^{\pm} \to 3\pi and K \to 2\pi decays are expressed in
terms of different combinations of one and the same set of CP-conserving and
CP-odd parameters. Extracting the magnitudes of these parameters from the data
on K \to 2\pi decays, we estimate an expected CP-odd difference between the
values of the slope parameters g^+ and g^- of the energy distributions of "odd"
pions in K^+ \to \pi^+\pi^+\pi^- and K^- \to \pi^-\pi^-\pi^+ decays.Comment: 12 pages, no figure
Two photon decay of neutral scalars below 1.5 GeV in a chiral model for bar{q}q and bar{q}bar{q}qq states
We study the two photon decay of neutral scalars below 1.5 GeV in the context
of a recently proposed chiral model for bar{q}q and bar{q}bar{q}qq states. We
find good agreement with experimental results for the a_{0}(980)->gamma gamma.
Our calculations for f_{0}(980)->gamma gamma shows that further work is
necessary in order to understand the structure of this meson. The model
predicts Gamma(a_{0}(1450)->gamma gamma)=0.16+/-0.10KeV, Gamma(sigma->gamma
gamma)=0.47+/-0.66 KeV, Gamma(f(1370)->gamma gamma)=0.07+/-0.15 KeV,
Gamma(f(1500)->gamma gamma)=0.74+/-0.78 KeV.Comment: 6 pages, 1 figur
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