Related papers: 1/N_c and epsilon'/epsilon

It is widely believed that hadronisation leads to 1/Q corrections to e+e- event shapes. We show that there are further corrections, proportional to (ln Q)^A/Q with A=4C_A/beta_0~=1.6, associated with hadron masses and whose relative…

We report on the status of our dynamical simulations of a $SU (N_c )$ gauge theory with $N_c=3-6$ and $N_f =4$ fundamental fermions. These ensembles can be used to study the Large $N_c$ scaling of weak matrix elements in the GIM limit…

We derive expressions for pion electroproduction amplitudes in the 1/N_c expansion of QCD, and obtain from them linear relations between the electromagnetic multipole amplitudes that hold at all energies. The leading-order relations in…

We present a leading-order pQCD calculation of the helicity-flip $\Delta\to N\gamma^*$ matrix element $G_0$ (Coulomb quadrupole amplitude $C2$), taking into account the transverse momenta of the quarks and the contribution from the gluons.…

We report progress in our lattice study of hadronic weak matrix elements relevant for the Delta I = 1/2 rule and epsilon-prime. The presented results are from our first runs on a quenched ensemble with beta=6.0 and a dynamical Nf=2 ensemble…

It is shown that if, from the starting point of a universal rank-one mass matrix long favoured by phenomenologists, one adds the assumption that it rotates (changes its orientation in generation space) with changing scale, one can…

Strong isospin-breaking (IB) effects in CP-even and CP-odd K-->pi pi decays are computed to next-to-leading order (NLO) in the chiral expansion. The impact of these corrections on the magnitude of the Delta I=1/2 Rule and on the size of the…

Experiments at CERN and Fermilab have been competing each other to improve the measurement of a CP violation parameter, epsilon'/epsilon. Fermilab KTeV-E832 recently announced their final result, Re(epsilon'/epsilon) = [19.2 +- 2.1] x…

Using the method of asymptotic sum rules we estimated the size of $O(m_s p_\pi^4)$ and $O(m_s^2 p_\pi^2)$ corrections to $\pi K$ scattering amplitude in large $N_c$ limit. These corrections arise from the sixth order effective chiral…

I summarize the status of the $\Delta I=1/2$ rule in $K\to\pi\pi$ decays within an {\it analytic} approach based on the dual representation of QCD as a theory of weakly interacting mesons for large $N$, where $N$ is the number of colours.…

We investigate the magnetic susceptibility of the QCD vacuum with the $1/N_c$ corrections taken into account, based on the instanton vacuum. Starting from the instanton liquid model we derive the gauged light-quark partition function in the…

We consider one loop QCD corrections and renormalization group running of the neutrinoless double beta decay amplitude focusing on the short-range part of the amplitude (without the light neutrino exchange) and find that these corrections…

The semileptonic decay $\Lambda_c \to \Lambda \ell \nu$ is considered in the framework of heavy quark effective theory beyond the leading order in the $1/m_c$ expansion. According to our estimate the polarization variable will receive only…

The CP violating parameter epsilon'/epsilon is computed using the low-energy dynamics of a chiral theory supplemented by vector resonances. The divergent contributions coming from strong pi-pi scattering are tamed by vector-meson exchange…

This thesis deals with the study of baryon spectra in the context of the $1/N_c$ expansion. The standard tool to study baryon properties is the constituent quark model. The results are naturally model dependent. The $1/N_c$ expansion…

Estimates of the CP violating observable $\varepsilon'/\varepsilon$ have gained some attention in the past few years. Depending on the long-distance treatment used, they exhibit up to $2.9\sigma$ deviation from the experimentally measured…

We present the calculation of the short-distance power corrections to the CP-violation parameter $\varepsilon_K$ coming from dimension-8 operators in the $\Delta S=2$ effective Hamiltonian. A first estimate of this contribution, obtained…

Following the 1999 analysis of Gambino, Haisch and one of us, we stress that all the recent NLO analyses of $\varepsilon'/\varepsilon$ in the Standard Model (SM) suffer from the renormalization scheme dependence present in the electroweak…

The parameter epsilon_K, that quantifies CP violation in kaon mixing, is the observable setting the strongest constraints on new physics with a generic flavour and CP structure. While its experimental uncertainty is at the half percent…

We derive expressions for pion photoproduction amplitudes in the 1/N_c expansion of QCD, and obtain linear relations directly from this expansion that relate electromagnetic multipole amplitudes at all energies. The leading-order relations…