Tropidophis celiae

Number of pages: 8Geological SciencesIntegrative Biolog

Uzbudni hadronski spektar u QCD Coulombovoj baždarnosti

We discuss progress in understanding the light- and heavy-quark excited hadron spectrum from Coulomb gauge QCD. For light-quark systems, we highlight the insensitivity to spontaneous chiral symmetry breaking, which predicts Wigner parity-degeneracy in the highly-excited hadron spectrum and allows the quark-mass momentum dependence to be experimentally probed. For heavy-quark meson decays, we invoke the Franck-Condon principle, a consequence of small velocity changes for heavy quarks, to extract qualitative, but model-independent, structure insight from the momentum distribution of the decay products.Opisujemo postignuća u razumijevanju uzbudnog hadronskog spektra lakih i teških kvarkova u okviru QCD Coulombove baždarnosti. Za sustave lakih kvarkova ističemo neosjetljivost na spontano lomljenje kiralne simetrije, što predskazuje Wignerovu degeneraciju po parnosti hadronskog spektra visoke uzbude i omogućuje mjerenje impulsne ovisnosti o masi kvarka. Za teško-kvarkovske mezonske raspade, uključujemo Franck-Condonovo načelo radi postizanja približnog, ali neovisnog o modelu, shvaćanja strukture na osnovi impulsnih raspodjela čestica u raspadima

Uzbudni hadronski spektar u QCD Coulombovoj baždarnosti

We discuss progress in understanding the light- and heavy-quark excited hadron spectrum from Coulomb gauge QCD. For light-quark systems, we highlight the insensitivity to spontaneous chiral symmetry breaking, which predicts Wigner parity-degeneracy in the highly-excited hadron spectrum and allows the quark-mass momentum dependence to be experimentally probed. For heavy-quark meson decays, we invoke the Franck-Condon principle, a consequence of small velocity changes for heavy quarks, to extract qualitative, but model-independent, structure insight from the momentum distribution of the decay products.Opisujemo postignuća u razumijevanju uzbudnog hadronskog spektra lakih i teških kvarkova u okviru QCD Coulombove baždarnosti. Za sustave lakih kvarkova ističemo neosjetljivost na spontano lomljenje kiralne simetrije, što predskazuje Wignerovu degeneraciju po parnosti hadronskog spektra visoke uzbude i omogućuje mjerenje impulsne ovisnosti o masi kvarka. Za teško-kvarkovske mezonske raspade, uključujemo Franck-Condonovo načelo radi postizanja približnog, ali neovisnog o modelu, shvaćanja strukture na osnovi impulsnih raspodjela čestica u raspadima

Computer science approach to the stellar fabric of violent starforming regions in AGN

In order to analyse the large numbers of Seyfert galaxy spectra available at present, we are testing new techniques to derive their physical parameters fastly and accurately. We present an experiment on such a new technique to segregate old and young stellar populations in galactic spectra using machine learning methods. We used an ensemble of classifiers, each classifier in the ensemble specializes in young or old populations and was trained with locally weighted regression and tested using ten-fold cross-validation. Since the relevant information concentrates in certain regions of the spectra we used the method of sequential floating backward selection offline for feature selection. Very interestingly, the application to Seyfert galaxies proved that this technique is very insensitive to the dilution by the Active Galactic Nucleus (AGN) continuum. Comparing with exhaustive search we concluded that both methods are similar in terms of accuracy but the machine learning method is faster by about two orders of magnitude.Comment: 4 pages, 1 figure, Contribution to IAU Symp. 222, The interplay among Black Holes, Stars and ISM in Galactic Nuclei, Gramado, Brazil, 200

Three body systems with strangeness and exotic systems

We report on four $\Sigma$'s and three $\Lambda$'s, in the 1500 - 1800 MeV region, as two meson - one baryon S-wave $(1/2)^+$ resonances found by solving the Faddeev equations in the coupled channel approach, which can be associated to the existing $S$ = -1, $J^P= 1/2^+$ low lying baryon resonances. On the other hand we also report on a new, hidden strangeness $N^*$ state, mostly made of $K \bar{K} N$, with mass around 1920 MeV, which we think could be responsible for the peak seen in the $\gamma p \to K^+ \Lambda$ around this energy. Finally we address a very novel topic in which we show how few body systems of several $\rho$ mesons can be produced, with their spins aligned up to J=6, and how these states found theoretically can be associated to several known mesons with spins J=2,3,4,5,6.Comment: Talk at the 21st European Conference on Few Body Problems in Physics, Salamanca, Sep. 201

Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB

We present results of a dark matter search performed with a 0.6 kg day exposure of the DAMIC experiment at the SNOLAB underground laboratory. We measure the energy spectrum of ionization events in the bulk silicon of charge-coupled devices down to a signal of 60 eV electron equivalent. The data are consistent with radiogenic backgrounds, and constraints on the spin-independent WIMP-nucleon elastic-scattering cross section are accordingly placed. A region of parameter space relevant to the potential signal from the CDMS-II Si experiment is excluded using the same target for the first time. This result obtained with a limited exposure demonstrates the potential to explore the low-mass WIMP region (<10 GeV/$c^{2}$) of the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB.Comment: 11 pages, 11 figure

Theoretical study of incoherent phi photoproduction on a deuteron target

We study the photoproduction of phi mesons in deuteron, paying attention to the modification of the cross section from bound protons to the free ones with the aim of comparing with recent results at LEPS. For this purpose we take into account Fermi motion in single scattering and rescattering of the phi to account for phi absorption on a second nucleon as well as the rescattering of the proton. We find that the contribution of the double scattering is much smaller than the typical cross section of gamma p to phi p in free space, which implies a very small screening of the phi production in deuteron. The contribution from the proton rescattering, on the other hand, is found to be not negligible compared to the cross section of gamma p to phi p in free space, and leads to a moderate reduction of the phi photoproduction cross section on a deuteron at forward angles if LEPS set up is taken into account. The Fermi motion allows contribution of the single scattering in regions forbidden by phase space in the free case. In particular, we find that for momentum transferred squared close to the maximum value, the Fermi motion changes drastically the shape of d sigma / dt, to the point that the ratio of this cross section to the free one becomes very sensitive to the precise value of t chosen, or the size of the bin used in an experimental analysis. Hence, this particular region of t does not seem the most indicated to find effects of a possible phi absorption in the deuteron. This reaction is studied theoretically as a function of t and the effect of the experimental angular cuts at LEPS is also discussed, providing guidelines for future experimental analyses of the reaction.Comment: 17 pages, 16 figure