In spite of prolonged polemics, the agreement on the existence of N(1710) P11 resonance has not until now been reached, and the Particle Data Group declares it as a 3-star resonance only. We show that the proper inclusion of inelastic channels in the coupled-channel formalism indisputably demands the existence of N(1710) P11 state, and that it presumably stays "hidden" within the continuum ambiguity of any typical single channel partial wave analyses. Consequently, its Particle Data Group confidence rating should be raised to a 4-star resonance.

A model-independent method for the determination of Breit-Wigner resonance parameters is presented. The method is based on eliminating the dependence on the choice of channel basis by analyzing the trace of the K and T matrices in the coupled-channel formalism, rather than individual matrix elements of the multichannel scattering matrix.of Particle Physics [1] by the Particle Data Group (PDG). Each resonance in the Review has been parametrized in two ways. First, there are Breit-Wigner parameters, i.e. the resonance mass M R , decay width Γ R , and branching ratios x a (the ratio between the partial width into channel a and the total width). Alternatively, T -matrix complex poles (Re W p and −2 Im W p ), as well as complex residues (moduli |r|, and phases θ) are given in [1]. Breit-Wigner parameters obtained in various partial-wave analyses vary quite substantially, partly because details of those analyses are different; i.e. the number and character of the included channels, different parameterization schemes, analyticity constraints for scattering amplitudes, the choice of background models, and the method of unitarization (if at all) of the S matrix. However, it is also the case that the methods for extracting resonance parameters are different: Argand-plot fits [2], Breit-Wigner fits with background [3], direct fits of analysis parameters [4,5], or model specific schemes which extract T matrix poles [6,7,8].In this Letter we present a model-independent

The Zagreb analysis partial-wave T matrices included in the Review of Particle Physics [by the Particle Data Group (PDG)] contain Breit-Wigner parameters only. As the advantages of pole over Breit-Wigner parameters in quantifying scattering matrix resonant states are becoming indisputable, we supplement the original solution with the pole parameters. Because of an already reported numeric error in the S 11 analytic continuation [Batinić et al., Phys. Rev. C 57, 1004(E) (1997); arXiv:nucl-th/9703023], we declare the old BATINIC 95 solution, presently included by the PDG, invalid. Instead, we offer two new solutions: (A) corrected BATINIC 95 and (B) a new solution with an improved S 11 π N elastic input. We endorse solution (B).

Inspired by anomalies which the standard scattering matrix pole-extraction procedures have produced in a mathematically well defined coupled-channel model, we have developed a new method based solely on the assumption of partial-wave analyticity. The new method is simple and applicable not only to theoretical predictions but to the empirical partial-wave data as well. Since the standard pole-extraction procedures turn out to be the lowest-order term of the proposed method the anomalies are understood and resolved. 11.55.Fv, 14.20.Gk, 25.40.Ny. Introduction. The determination of the scattering matrix (S-matrix) is considered to be the major objective of both, scattering theory and energy-dependent analysis of scattering data. The collection of S-matrix poles in the "unphysical" Riemann sheet is related to resonance mass spectrum [1, 2] so obtaining them is the crucial goal of any partial-wave analysis. There is, however, a long lasting (and yet unresolved) controversy on the resonances' physical properties. It is not clear whether physical mass and decay width of a resonance are given by the "conventional" resonance parameters like Breit-Wigner mass and the decay width, or by resonance pole parameters-real part and −2× imaginary part of pole [3,4]. In the case of baryon resonances, the compromise is achieved in a way that all the conventional, as well as pole parameters are collected in the Review of Particle Physics (RPP) [5].The motivation for this work came from the fact that pole parameters we extracted from our coupled-channel partial waves [6] by a standard model-independent pole searching method (speed plot [3]) were not unique. The obtained pole positions varied from one reaction to another. The time-delay [7], another method of choice for resonance pole extraction was employed, but with similar outcome. This anomalous behavior challenged common sense and the conclusion was drawn that either our partial-wave analysis or the applied pole extraction methods were incorrect. The extraction methods were carefully examined, and those methods were determined to be at fault. This effort resulted in a new model-independent extraction method free from this anomaly. In addition, we calculated elastic pole residues, and the obtained values were in quite good agreement with others published in the RPP [5]. Since there are no RPP estimates for elastic residues yet, this result lends support to provide them.It is important to draw a distinction between the timedelay signal as resonance's "smoking gun", and utilization of the time-delay (or speed plot) for the extraction

OPERA is part of the CNGS project and it is an experiment dedicated to the observation of long-baseline nu(mu) into nu(tau) oscillations through tau appearance. Resistive Plate Chambers (RPCs) with bakelite electrodes are used to instrument the 2 cm gaps between the magnetized iron slabs of the two spectrometers. The RPC installation ended in may 2004 on the first spectrometer and in march 2005 on the second one. Before the installation, every RPC is subjected to a complete test chain in order to reject the poorer quality detectors. The tests are performed in dedicated facilities to ensure the proper RPC gluing, to measure its electrical properties and to verify the response to cosmic rays and the intrinsic noise levels. We have also tested the long term stability of real size OPERA RPC prototypes operated at cosmic ray fluxes for more than one year. On small size prototypes we are performing studies on the gas' mixtures in order to reduce the total charge released in the gas for each detector count. The validation of the installed RPCs has been performed with pure nitrogen. A small part of them has been also tested with the gas mixture Ar/C2H2F4/i - C4H10/SF6 = 75.4/20/4/0.6