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Register a new userThe meson spectrum in large-N QCD
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We present lattice results on the meson spectrum and decay constants in large-N QCD. The results are obtained in the quenched approximation for N = 2, 3, 4, 5, 6, 7 and 17 and extrapolated to infinite N.
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We present the result of our computation of the lowest lying meson masses for SU(N) gauge theory in the large $N$ limit (with $N_f/Nlongrightarrow 0$). The final values are given in units of the square root of the string tension, and with errors which account for both statistical and systematic errors. By using 4 different values of the lattice spacing we have seen that our results scale properly. We have studied various values of $N$ (169, 289 and 361) to monitor the N-dependence of the most sensitive quantities. Our methodology is based upon a first principles approach (lattice gauge theory) combined with large $N$ volume independence. We employed both Wilson fermions and twisted mass fermions with maximal twist. In addition to masses in the pseudoscalar, vector, scalar and axial vector channels, we also give results on the pseudoscalar decay constant and various remormalization factors.
The vector meson mass is computed as a function of quark mass in the large N limit of QCD. We use continuum reduction and directly compute the vector meson propagator in momentum space. Quark momentum is inserted using the quenched momentum prescription.
Recent lattice results on the meson and baryon spectrum with a focus on the determination of hadronic resonance masses and widths using a combined basis of single-hadron and hadron-hadron interpolating fields are reviewed. These mostly exploratory calculations differ from traditional lattice QCD spectrum calculations for states stable under QCD, where calculations with a full uncertainty estimate are already routinely performed. Progress and challenges in these calculations are highlighted.
Meson masses and decay constants in the large $N$ limit of SU($N$) gauge theory are determined using the twisted Eguchi-Kawai reduced model. To this end, we make use of a recently defined smearing method valid on the one-point lattice. This procedure, in combination with a variational analysis, allows to obtain reliable values for these quantities.
We present results of meson and baryon spectroscopy using the Chirally Improved Dirac operator on lattices of size 16**3 x 32 with two mass-degenerate light sea quarks. Three ensembles with pion masses of 322(5), 470(4) and 525(7) MeV and lattice spacings close to 0.15 fm are investigated. Results on ground and excited states for several channels are given, including spin two mesons and hadrons with strange valence quarks. The analysis of the states is done with the variational method, including two kinds of Gaussian sources and derivative sources. We obtain several ground states fairly precisely and find radial excitations in various channels. Excited baryon results seem to suffer from finite size effects, in particular at small pion masses. We discuss the possible appearance of scattering states in various channels, considering masses and eigenvectors. Partially quenched results in the scalar channel suggest the presence of a 2-particle state, however, in most channels we cannot identify them. Where available, we compare our results to results of quenched simulations using the same action.
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