Search results for "pi pi"
showing 5 items of 5 documents
Scalar mesons moving in a finite volume and the role of partial wave mixing
2012
Phase shifts and resonance parameters can be obtained from finite-volume lattice spectra for interacting pairs of particles, moving with nonzero total momentum. We present a simple derivation of the method that is subsequently applied to obtain the pi pi and pi K phase shifts in the sectors with total isospin I=0 and I=1/2, respectively. Considering different total momenta, one obtains extra data points for a given volume that allow for a very efficient extraction of the resonance parameters in the infinite-volume limit. Corrections due to the mixing of partial waves are provided. We expect that our results will help to optimize the strategies in lattice simulations, which aim at an accurat…
Pion and kaon vector form factors
2001
We develop a unitarity approach to consider the final state interaction corrections to the tree level graphs calculated from Chiral Perturbation Theory ($\chi PT$) allowing the inclusion of explicit resonance fields. The method is discussed considering the coupled channel pion and kaon vector form factors. These form factors are then matched with the one loop $\chi PT$ results. A very good description of experimental data is accomplished for the vector form factors and for the $\pi\pi$ P-wave phase shifts up to $\sqrt{s}\lesssim 1.2$ GeV, beyond which multiparticle states play a non negligible role. In particular the low and resonance energy regions are discussed in detail and for the forme…
Hadronic τ Decays as New Physics Probes in the LHC Era
2019
We analyze the sensitivity of hadronic tau decays to non-standard interactions within the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Both exclusive and inclusive decays are studied, using the latest lattice data and QCD dispersion relations. We show that there are enough theoretically clean channels to disentangle all the effective couplings contributing to these decays, with the $\tau \to \pi\pi\nu_\tau$ channel representing an unexpected powerful New Physics probe. We find that the ratios of non-standard couplings to the Fermi constant are bound at the sub-percent level. These bounds are complementary to the ones from electroweak precision observable…
Liian hieno Pepiksi : esikoululaiset kertovat käsityksistään lastenkirjojen kuvahahmoista
2015
Tutkimus tarkastelee lastenkirjojen kuvahahmoja esikouluikäisten lasten kertomana. Tutkimus selvittää, mitä esikouluikäiset lapset kertovat käsityksistään muumista, Peppi Pitkätossusta sekä Lumikista ja seitsemästä kääpiöstä ja kyseisten hahmojen erilaisista versioista. Lastenkirjat ovat osa lapsuutta ja aikuisten lapsille tuottamaa lastenkulttuuria. Lasten tiedetään yleisesti pitävän kuvista ja katselevan kuvia ennen kirjallisen lukutaidon kehittymistä. Kuitenkin tutkimustietoa siitä, mitä lapset ajattelevat kuvakirjoista on varsin vähän. Tutkimus liittyy lapsitutkimukseen ja sillä on yhtymäkohtia lapsuudentutkimukseen sekä lapsinäkökulmaiseen tutkimukseen. Tutkimus on luonteeltaan laadull…
Charge fluctuations and electric mass in a hot meson gas
2006
Net-Charge fluctuations in a hadron gas are studied using an effective hadronic interaction. The emphasis of this work is to investigate the corrections of hadronic interactions to the charge fluctuations of a non-interacting resonance gas. Several methods, such as loop, density and virial expansions are employed. The calculations are also extended to SU(3) and some resummation schemes are considered. Although the various corrections are sizable individually, they cancel to a large extent. As a consequence we find that charge fluctuations are rather well described by the free resonance gas.