Search results for "Particle Data Group"
showing 10 items of 21 documents
Exotic states in the S=1 N-pi-K system and low-lying 1/2+ S=-1 resonances
2010
In this manuscript we discuss about our study of the $N \pi \bar{K}$ and the NπK systems made by solving the Faddeev equations with the two-body t-matrices obtained by solving the Bethe-Salpeter equations with the potentials obtained from chiral dynamics. In the strangeness = -1 case, we found that all the Λ and Σ resonances listed by the particle data group, with spin-parity 1/2+ , in the 1550-1800 MeV region get generated due to the involved three-body dynamics. This motivated us to study the strangeness =1 three-body system, i.e., NπK , where we did not find any evidence for the Θ + (1542) but found a broad bump around 1700 MeV which has a κ (800)N structure.
Measurement of the branching ratios of the decays Ξ0→Σ+e−ν¯e and Ξ0¯→Σ+¯e+νe
2007
Abstract From 56 days of data taking in 2002, the NA48/1 experiment observed 6316 Ξ 0 → Σ + e − ν ¯ e candidates (with the subsequent Σ + → p π 0 decay) and 555 Ξ 0 ¯ → Σ + ¯ e + ν e candidates with background contamination of 215 ± 44 and 136 ± 8 events, respectively. From these samples, the branching ratios BR ( Ξ 0 → Σ + e − ν ¯ e ) = ( 2.51 ± 0.03 stat ± 0.09 syst ) × 10 −4 and BR ( Ξ 0 ¯ → Σ + ¯ e + ν e ) = ( 2.55 ± 0.14 stat ± 0.10 syst ) × 10 −4 were measured allowing the determination of the CKM matrix element | V us | = 0.209 −0.028 +0.023 . Using the Particle Data Group average for | V us | obtained in semileptonic kaon decays, we measured the ratio g 1 / f 1 = 1.20 ± 0.05 of the …
Measurement of the proton scalar polarizabilities at MAMI
2019
The electric (αE1) and magnetic (βM1) scalar polarizabilities describe the response of the nucleon to an applied electric or magnetic field. They are not only fundamental properties related to the internal structure and dynamics of the nucleon, but they are important also in other areas of physics, such as atomic structure. The values of αE1 and βM1 quoted by the Particle Data Group were determined using data on the unpolarized differential cross-section of the Compton scattering $\gamma p \to \gamma p$. The measurement of the beam asymmetry Σ3, provides an alternative approach to the extraction of the scalar polarizabilities, with different sensitivity and systematics compared to the unpol…
Nucleon resonances inπNscattering up to energiess⩽2.0GeV
2007
A meson-exchange model for pion-nucleon scattering was previously constructed using a three-dimensional reduction scheme of the Bethe-Salpeter equation for a model Lagrangian involving $\ensuremath{\pi},\ensuremath{\eta},N,\ensuremath{\Delta},\ensuremath{\rho}$, and \ensuremath{\sigma} fields. We thereby extend our previous work by including the $\ensuremath{\eta}N$ channel and all the $\ensuremath{\pi}N$ resonances with masses $~2$ GeV, up to the $F$ waves. The effects of the $\ensuremath{\pi}\ensuremath{\pi}N$ channels are taken into account by introducing an effective width in the resonance propagators. The extended model gives an excellent fit to both $\ensuremath{\pi}N$ phase shifts an…
Low lying axial-vector mesons as dynamically generated resonances
2005
We make a theoretical study of the s-wave interaction of the nonet of vector mesons with the octet of pseudoscalar mesons starting from a chiral invariant Lagrangian and implementing unitarity in coupled channels. By looking for poles in the unphysical Riemann sheets of the unitarized scattering amplitudes, we get two octets and one singlet of axial-vector dynamically generated resonances. The poles found can be associated to most of the low lying axial-vector resonances quoted in the Particle Data Book: $b_1(1235)$, $h_1(1170)$, $h_1(1380)$, $a_1(1260)$, $f_1(1285)$ and two poles to the $K_1(1270)$ resonance. We evaluate the couplings of the resonances to the $VP$ states and the partial de…
Pole positions and residues from pion photoproduction using the Laurent-Pietarinen expansion method
2014
We have applied a new approach to determine the pole positions and residues from pion photoproduction multipoles. The method is based on a Laurent expansion of the partial wave T-matrices, with a Pietarinen series representing the regular part of energy-dependent and single-energy photoproduction solutions. The method has been applied to multipole fits generated by the MAID and GWU/SAID groups. We show that the number and properties of poles extracted from photoproduction data correspond very well to results from $\pi$N elastic data and values cited by Particle Data Group (PDG). The photoproduction residues provide new information for the electromagnetic current at the pole position, which …
Baryonic Resonances from Baryon Decuplet-Meson Octet Interactions and the Exotic Resonance , ,
2005
Using the lowest order chiral Lagrangian we study s -wave interactions of the baryon decuplet with the octet of pseudoscalar mesons. We find two bound states in the flavour SU (3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU (3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star 3 2 − resonances listed by the Particle Data Group. In particular, the Ξ(1820), the Λ1520) and the Σ(1670) states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the various ch…
Exploring the D* rho system within QCD sum rules
2013
We present a study of the D* rho system made by using the method of QCD sum rules to determine the mass of possible resonances generated in the same system. Using isospin and spin projectors, we investigate the different configurations and obtain evidences for three D* mesons with isospin I = 1/2, spin S = 0, 1, 2 and with masses 2500 +/- 67, 2523 +/- 60, and 2439 +/- 119 MeV, respectively. The last state can be associated with D-2*(2460) ( spin 2) listed by the Particle Data Group, while one of the first two might be related to D* (2640), with unknown spin parity. In the case of I = 3/2 we also find evidences of three states with spin 0, 1, and 2, respectively, with masses 2467 +/- 82, 242…
Measurement of the Dalitz plot slope parameters of the K±→π±π+π− decay
2007
Abstract The distribution of the K ± → π ± π + π − decays in the Dalitz plot has been measured by the NA48/2 experiment at the CERN SPS with a sample of 4.71 × 10 8 fully reconstructed events. With the standard Particle Data Group parameterization the following values of the slope parameters were obtained: g = ( − 21.134 ± 0.017 ) % , h = ( 1.848 ± 0.040 ) % , k = ( − 0.463 ± 0.014 ) % . The quality and statistical accuracy of the data have allowed an improvement in precision by more than an order of magnitude, and are such as to warrant a more elaborate theoretical treatment, including pion–pion rescattering, which is in preparation.
η→π0γγdecay within a chiral unitary approach revisited
2008
In view of the recent experimental developments in η→π^(0)γ γ decay, and the fact that the Particle Data Group in the online edition of 2007 reports sizable changes of the radiative decay widths of vector mesons used as input in the theoretical calculations of E. Oset, J. R. Pelaez, and L. Roca [Phys. Rev. D 67, 073013 (2003)], a reevaluation of the decay width of the in this channel has been done, reducing its uncertainty by almost a factor of 2. The new input of the Particle Data Group is used, and invariant mass distributions and total widths are compared with the most recent results from the AGS and MAMI experiments, and preliminary ones of KLOE. The agreement of the theory with the AGS…