Search results for "Chiral perturbation Theory"
showing 10 items of 294 documents
Leading SU(3)-breaking corrections to the baryon magnetic moments in Chiral Perturbation Theory
2008
We calculate the baryon magnetic moments using covariant Chiral Perturbation Theory ($\chi$PT) within the Extended-on-mass-shell (EOMS) renormalization scheme. By fitting the two available low-energy constants (LECs), we improve the Coleman-Glashow description of the data when we include the leading SU(3) breaking effects coming from the lowest-order loops. This success is in dramatic contrast with previous attempts at the same order using Heavy Baryon (HB) $\chi$PT and covariant Infrared (IR) $\chi$PT. We also analyze the source of this improvement with particular attention on the comparison between the covariant results.
Masses and magnetic moments of ground-state baryons in covariant baryon chiral perturbation theory
2012
We report on some recent developments in our understanding of the light-quark mass dependence and the SU(3) flavor symmetry breaking corrections to the magnetic moments of the ground-state baryons in a covariant formulation of baryon chiral perturbation theory, the so-called EOMS formulation. We show that this covariant ChPT exhibits some promising features compared to its heavy-baryon and infrared counterparts.
Flavor-singlet meson decay constants from Nf=2+1+1 twisted mass lattice QCD
2018
We present an improved analysis of our lattice data for the $\ensuremath{\eta}--{\ensuremath{\eta}}^{\ensuremath{'}}$ system, including a correction of the relevant correlation functions for residual topological finite size effects and employing consistent chiral and continuum fits. From this analysis we update our physical results for the masses ${M}_{\ensuremath{\eta}}=557(11{)}_{\text{stat}}(03{)}_{\ensuremath{\chi}\mathrm{PT}}\text{ }\text{ }\mathrm{MeV}$ and ${M}_{\ensuremath{\eta}}^{\ensuremath{'}}=911(64{)}_{\text{stat}}(03{)}_{\ensuremath{\chi}\mathrm{PT}}\text{ }\text{ }\mathrm{MeV}$, as well as the mixing angle in the quark flavor basis $\ensuremath{\phi}=38.8(2.2{)}_{\text{stat}}…
Weak pion production off the nucleon in covariant chiral perturbation theory
2018
Weak pion production off the nucleon at low energies has been systematically investigated in manifestly relativistic baryon chiral perturbation theory with explicit inclusion of the $\Delta$(1232) resonance. Most of the involved low-energy constants have been previously determined in other processes such as pion-nucleon elastic scattering and electromagnetic pion production off the nucleon. For numerical estimates, the few remaining constants are set to be of natural size. As a result, the total cross sections for single pion production on neutrons and protons, induced either by neutrino or antineutrino, are predicted. Our results are consistent with the scarce existing experimental data ex…
Chiral dynamics in systems with strangeness
2002
In this talk a brief review of several problems involving systems with strangeness is made. In the first place one shows how the $\Lambda (1405)$, $\Lambda(1670)$ and $\Sigma(1620)$ states, for $S = -1$, and the $\Xi(1620)$ for $S= -2$ are generated dynamically in the context of unitarized chiral perturbation theory. The results for the $\bar{K}N$ interaction are then used to evaluate the $K^- d$ scattering length. Results obtained for the kaon selfenergy in a nuclear medium within this approach, with application to $K^-$ atoms, are also mentioned. Finally a few words are said about recent developments in the weak decay of $\Lambda$ hypernuclei and the puzzle of the $\Gamma_n/\Gamma_p$ rati…
Pion Photo- and Electroproduction and the Chiral MAID Interface
2015
We discuss the extended on-mass-shell scheme for manifestly Lorentz-invariant baryon chiral perturbation theory. We present a calculation of pion photo- and electroproduction up to and including order $q^4$. The low-energy constants have been fixed by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID (http://www.kph.uni-mainz.de/MAID/chiralmaid/). We explain how our program works and how it can be used for further analysis.
Isovector electromagnetic form factors of the nucleon from lattice QCD and the proton radius puzzle
2021
Physical review / D 103(9), 094522 (2021). doi:10.1103/PhysRevD.103.094522
Chiral unitary theory: Application to nuclear problems
2001
In this talk we briefly describe some basic elements of chiral perturbation theory, $\chi PT$, and how the implementation of unitarity and other novel elements lead to a better expansion of the $T$ matrix for meson meson and meson baryon interactions. Applications are then done to the $ \pi \pi $ interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and $K^-$ atoms, and how the $\phi$ meson properties are changed in a nuclear medium.
Predictions of covariant chiral perturbation theory for nucleon polarisabilities and polarised Compton scattering
2015
We update the predictions of the SU(2) baryon chiral perturbation theory for the dipole polarisabilities of the proton, $\{\alpha_{E1},\,\beta_{M1}\}_p=\{11.2(0.7),\,3.9(0.7)\}\times10^{-4}$fm$^3$, and obtain the corresponding predictions for the quadrupole, dispersive, and spin polarisabilities: $\{\alpha_{E2},\,\beta_{M2}\}_p=\{17.3(3.9),\,-15.5(3.5)\}\times10^{-4}$fm$^5$, $\{\alpha_{E1\nu},\,\beta_{M1\nu}\}_p=\{-1.3(1.0),\,7.1(2.5)\}\times10^{-4}$fm$^5$, and $\{\gamma_{E1E1},\,\gamma_{M1M1},\,\gamma_{E1M2},\,\gamma_{M1E2}\}_p=\{-3.3(0.8),\,2.9(1.5),\,0.2(0.2),\,1.1(0.3)\}\times10^{-4}$fm$^4$. The results for the scalar polarisabilities are in significant disagreement with semi-empirical …
Pion photo- and electroproduction in relativistic baryon ChPT
2014
We present a calculation of pion photo- and electroproduction in manifestly Lorentz-invariant baryon chiral perturbation theory up to and including order q^4. We fix the low-energy constants by fitting experimental data in all available reaction channels. Our results can be accessed via a web interface, the so-called chiral MAID.