0000000000331943
AUTHOR
A. Pich
showing 11 related works from this author
tau -> pi pi pi nu(tau) decays and the a(1)(1260) off-shell width revisited
2009
The tau -> pi pi pi nu(tau) decay is driven by the hadronization of the axial-vector current. Within the resonance chiral theory, and considering the large-N-C expansion, this process has been studied in Ref. [1] (D. Gomez Dumm, A. Pich, J. Portoles, 2004). In the light of later developments we revise here this previous work by including a new off-shell width for the lightest a(1) resonance that provides a good description of the tau -> pi pi pi nu(tau) spectrum and branching ratio. We also consider the role of the rho(1450) resonance in these observables. Thus we bring in an overall description of the tau -> pi pi pi nu(tau) process in excellent agreement with our present experimental know…
Large-Nc Properties of the rho and f0(600) Mesons from Unitary Resonance Chiral Dynamics
2011
We construct pi-pi amplitudes that fulfill exact elastic unitarity, account for one loop Chiral Perturbation Theory contributions and include all 1/Nc leading terms, with the only limitation of considering just the lowest-lying nonet of exchanged resonances. Within such scheme, the Nc dependence of sigma and rho masses and widths is discussed. Robust conclusions are drawn in the case of the rho resonance, confirming that it is a stable meson in the limit of a large number of QCD colors, Nc. Less definitive conclusions are reached in the scalar-isoscalar sector. With the present quality of data, we cannot firmly conclude whether or not the Nc=3 f0(600) resonance completely disappears at larg…
Bottom quark mass from QCD sum rules for the υ system
1999
Abstract The talk presents an update of the bottom quark mass determination from QCD moment sum rules for the ϒ system by the authors [1]. Employing the MS scheme, we fund mb(mb) = 4.19 ± 0.06 GeV. The differences to our previous analysis will be discussed and we comment on the determination of th pole mass for the bottom quark.
Theoretical status of $\varepsilon'/\varepsilon$
2019
We briefly overview the historical controversy around Standard Model predictions of $\varepsilon'/\varepsilon$ and clarify the underlying physics. A full update of this important observable is presented, with all known short- and long-distance contributions, including isospin-breaking corrections. The current Standard Model prediction, $\mathrm{Re}(\varepsilon'/\varepsilon) = (14\pm 5)\cdot 10^{-4}$, is in excellent agreement with the experimentally measured value.
Isospin violation in epsilon'
2003
4 páginas, 1 tabla.-- PACS numbers: 12.39.Fe, 11.30.Er, 13.25.Es
CP Violation
1993
An overview of the phenomenology of CP violation is presented. The Standard Model mechanism of CP violation and its main experimental tests, both in the kaon and bottom systems, are discussed. (Lectures given at the 1993 Trieste Summer School and at the Escuela Latinoamericana de Fisica, ELAF'93, Argentina).
The strong coupling constant: State of the art and the decade ahead
2022
This document provides a comprehensive summary of the state-of-the-art, challenges, and prospects in the experimental and theoretical study of the strong coupling $\alpha_s$. The current status of the seven methods presently used to determine $\alpha_s$ based on: (i) lattice QCD, (ii) hadronic $\tau$ decays, (iii) deep-inelastic scattering and parton distribution functions fits, (iv) electroweak boson decays, hadronic final-states in (v) e+e-, (vi) e-p, and (vii) p-p collisions, and (viii) quarkonia decays and masses, are reviewed. Novel $\alpha_s$ determinations are discussed, as well as the averaging method used to obtain the PDG world-average value at the reference Z boson mass scale, $\…
Hard m(t) corrections as a probe of the symmetry breaking sector
1996
Non-decoupling effects related to a large $m_t$ affecting non-oblique radiative corrections in vertices ($Z\bar{b}b$) and boxes ($B$-$\bar{B}$ mixing and $\epsilon_K$) are very sensitive to the particular mechanism of spontaneous symmetry breaking. We analyze these corrections in the framework of a chiral electroweak standard model and find that there is only one operator in the effective lagrangian which modifies the longitudinal part of the $W^+$ boson without touching the oblique corrections. The inclusion of this operator affects the $Z\bar{b}b$ vertex, the $B$-$\bar{B}$ mixing and the CP-violating parameter $\epsilon_K$, generating interesting correlations among the hard $m_t^4 \log m_…
The Euclidean Adler Function and its Interplay with $\Delta\alpha^{\mathrm{had}}_{\mathrm{QED}}$ and $\alpha_s$
2023
Three different approaches to precisely describe the Adler function in the Euclidean regime at around $2\, \mathrm{GeVs}$ are available: dispersion relations based on the hadronic production data in $e^+e^-$ annihilation, lattice simulations and perturbative QCD (pQCD). We make a comprehensive study of the perturbative approach, supplemented with the leading power corrections in the operator product expansion. All known contributions are included, with a careful assessment of uncertainties. The pQCD predictions are compared with the Adler functions extracted from $\Delta\alpha^{\mathrm{had}}_{\mathrm{QED}}(Q^2)$, using both the DHMZ compilation of $e^+e^-$ data and published lattice results…
Phenomenology of the Green's function within the Resonance Chiral Theory
2003
4 páginas, 1 figura.-- Comunicación presentada en la 10ª High-Energy International Conference on Quantum ChromoDynamics celebrada del 2 al 8 de Julio de 2003 en Montpellier (Francia).-- arXiv:hep-ph/0309345v1
QCD and Strongly Coupled Gauge Theories: Challenges and Perspectives
2014
We dedicate this document to the memory of Mikhail Polikarpov, who passed away in July 2013. Misha worked with us for decades as a convener of the “Confinement” section of the Quark Confinement and Hadron Spectrum Series. He guided and expanded the scientific discussion of that topic, inspiring and under taking new research avenues. From its initial conception, he supported the enterprise of this document and organized Sect. 8, writing the part on confinement himself. He attracted the XIth Conference on Quark Confinement and the Hadron Spectrum to St. Petersburg (September 8-12, 2014; see http://phys.spbu.ru/confxi.html). His warm and kind personality, his high sense of humor, his ideas in …