We study the ππN system by solving the Faddeev equations, for which the input twobody t-matrices are obtained by solving the Bethe-Salpeter equation in the coupled channel formalism. The potentials for the ππ, πN sub-systems and their coupled channels are obtained from chiral Lagrangians, which have been earlier used to study resonances in these systems successfully. In this work, we find a resonance in the ππN system with a mass of 1704−i375/2 MeV and with quantum numbers I = 1/2, J π = 1/2 + . We identify this state with the N * (1710). This peak is found where the energies of the ππ sub-system fall in the region of the σ resonance. We do not find evidence for the Roper resonance in our study indicating a more complex structure for this resonance, nor for any state with total isospin I = 3/2 or 5/2. IntroductionThe excited states of the nucleon have been studied extensively theoretically as well as experimentally. This is evident from the fact that many of these states, especially those in the energy region below 1750 MeV, have been assessed either three or four stars by the particle data group (PDG) [1]. Even then, there are some resonances in this low energy region which still need unanimous agreement on their characteristics or existence, e.g., the J π = 1/2 + resonances in the isospin 1/2 domain. The N * (1440) or Roper resonance is a subject of continuous debate and the existence of the N * (1710) is even questioned. The quark models face difficulties in reproducing both these states [2,3,4]. In case of the N * (1710), some partial wave analyses [5,6] do not find any pole corresponding to it, while others claim a * kanchan@ific.uv.es † amartine@ific.uv.es ‡ oset@ific.uv.es 1 clear manifestation of this resonance [7,8,9,10]. On the other hand, the authors of [11] claim an indisputable existence of the N * (1710) from their study of the πN → ηN reaction in the coupled channel formalism and suggest that the status of this resonance should be improved from three-star to four-star.Another controversy about the N * (1710) started after the finding of a narrow peak in the γA → (K + n)X reaction at LEPS [12], suggesting the existence of a pentaquark state which some groups associated to a SU(3) antidecuplet to which the N * (1710) would also belong (see, for example, [13,14]). In order to be compatible with the Θ + , the N * (1710) is required to be narrow. However, the width of this resonance is not known precisely, with the widths listed in [1] ranging from ∼ 90 -480 MeV. The authors of [15] re-analyzed the πN → KΛ reaction and found that a narrow width of the N * (1710) [1] was incompatible with the data and proposed the existence of another narrow resonance in this energy region. The partial wave analyses group who do not find a pole for the N * (1710) suggested to look for other resonance in this energy region as a possible narrow, non-strange partner of the θ + [16,17]. The debate on this issue has continued with new analyses which do not find a signal for the θ + , as a consequence of which, the ca...

A study of meson-baryon systems with total strangeness -1 is made within a framework based on the chiral and hidden local symmetries. These systems consist of octet baryons, pseudoscalar and vector mesons. The pseudoscalar meson-baryon (PB) dynamics has been earlier found determinant for the existence of some strangeness -1 resonances, for example, $\Lambda(1405)$, $\Lambda(1670)$, etc. The motivation of the present work is to study the effect of coupling the closed vector meson-baryon (VB) channels to these resonances. To do this, we obtain the $PB \rightarrow PB$ and $VB \rightarrow VB$ amplitudes from the t-channel diagrams and the $PB \leftrightarrow VB$ amplitudes are calculated using the Kroll-Ruddermann term where, considering the vector meson dominance phenomena, the photon is replaced by a vector meson. The calculations done within this formalism reveal a very strong coupling of the VB channels to the $\Lambda(1405)$ and $\Lambda(1670)$. In the isospin 1 case, we find an evidence for a double pole structure of the $\Sigma (1480)$ which, like the isospin 0 resonances, is also found to couple strongly to the VB channels. The strong coupling of these low-lying resonances to the VB channels can have important implications on certain reactions producing them.Comment: Minor typos corrected (in Eq.(22) and axis-labels of some figures

We calculate the time evolution of the X(3872) abundance in the hot hadron gas produced in the late stage of heavy ion collisions. We use effective field Lagrangians to obtain the production and dissociation cross sections of X(3872). In this evaluation we include diagrams involving the anomalous couplings πD * D * and XD * D * and also the couplings of the X(3872) with charged D and D * mesons. With these new terms the X(3872) interaction cross sections are much larger than those found in previous works. Using these cross sections as input in rate equations, we conclude that during the expansion and cooling of the hadronic gas, the number of X(3872), originally produced at the end of the mixed QGP/hadron gas phase, is reduced by a factor of 4.

Abstract:We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of KD and KD * are induced and identified with the narrow D * s0 (2317) and D * s1 (2460) resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis KD ( * ) , and a two-channel basis KD ( * ) , ηD ( * ) s . By means of an extended Lüscher method we determine poles of the continuum t-matrix, bound by about 40 MeV with respect to the KD and KD * thresholds, which we identify with the D * s0 (2317) and D * s1 (2460) resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state D * s0 (2317) contains a KD component in an amount of about 70%, while the state D * s1 (2460) contains a similar amount of KD * . We argue that the present lattice simulation results do not still allow us to determine which are the missing channels in the bound state wave functions and we discuss the necessary information that can lead to answer this question.

A study of nonstrange meson-baryon systems has been made with the idea of understanding the properties of the low-lying 1/2 − N * and ∆ resonances. The coupled channels are built by considering the pseudoscalar and vector mesons together with the octet baryons. The formalism is based on obtaining the interactions from the lowest order chiral Lagrangian when dealing with pseudoscalar mesons and relying on the hidden local symmetry in case of the vector mesons. The transition between the two systems is obtained by replacing the photon by a vector meson in the Kroll-Ruderman theorem for the photoproduction of pseudoscalar mesons. The subtraction constants, required to calculate the loop-function in the scattering equations, are constrained by fitting the available experimental data on some of the reactions with pseudoscalar meson-baryon final states. As a consequence, we find resonances which can be related to N * (1535), N * (1650) (with a double pole structure), N * (1895) and ∆(1620). We conclude that these resonances can be, at least partly, interpreted as dynamically generated resonances and that the vector mesons play an important role in determining the dynamical origin of the low-lying N * and ∆ states. a kanchan@if.usp.br