Search results for "Strangeness"
showing 10 items of 118 documents
The S01 − Λ(1405) and − Λ(1670) resonances in meson-baryon unitarized coupled channel chiral perturbation theory
2003
Abstract The s-wave meson-baryon system with strangeness S = −1 and isospin I = 0 is studied using the Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry. The needed two particle irreducible potential is taken from lowest order Chiral Perturbation Theory in a relativistic formalism. The K N, πΣ, νΛ , and KΞ two-body channels have been included. Off-shell behavior is parameterized in terms of low energy constants, which outnumber those assumed in previous works and provide a better fit to the data. The masses, widths and branching ratios of the Λ(1405) and Λ(1670) resonances are determined. In our model, we find no one but two resonances in the Λ(1405) region.
Evidence for the Strangeness-Changing Weak DecayΞb−→Λb0π−
2015
Using a pp collision data sample corresponding to an integrated luminosity of 3.0 fb^{-1}, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay Ξ_{b}^{-}→Λ_{b}^{0}π^{-}. No b hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be f_{Ξ_{b}^{-}}/f_{Λ_{b}^{0}}B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-})=(5.7±1.8_{-0.9}^{+0.8})×10^{-4},where f_{Ξ_{b}^{-}} and f_{Λ_{b}^{0}} are the b→Ξ_{b}^{-} and b→Λ_{b}^{0} fragmentation fractions, and B(Ξ_{b}^{-}→Λ_{b}^{0}π^{-}) is the branching fraction. Assuming f_{Ξ_{b}^{-}}/f_{Λ_{b}^{0}} is bounded b…
The Mainz A4 parity violation experiment (single spin asymmetries in elastic scattering)
2005
Abstract The A4 experiment at the MAMI facility in Mainz measures a parity violating single spin asymmetry in the scattering of longitudinally polarized electrons off unpolarized protons. The longitudinal single spin asymmetry is parity violating and arises from the interference of the weak and electromagnetic one-boson exchange amplitude. It is sensitive to the strangeness contribution to the electromagnetic form factors of the nucleon. Recently the transverse single spin asymmetry has gained much interest. It is purely electromagnetic in origin and arises from the interference of the one-photon with the two-photon exchange amplitude. It is a time-odd quantity and sensitive to the imaginar…
Nuclear tests for the strange charge from factor of the nucleon
1992
Abstract It is shown that the measurements of elastic and inelastic scattering of neutrinos and parity-violating asymmetry of longitudinally polarized electrons on spin-isospin zero nuclei would yield model independent information about the strangeness charge form factor. Nunerical estimates of the contribution of this form factor are presented for 4 He, 12 C and 16 O nuclei in impulse approximation using strangeness vector from factors of the nucleon recently suggested in the literature. A general relation between the P -odd asymmetry in electron scattering and the cross sections of neutrino and unpolarized electron scattering on spin zero nuclei is obtained.
Three body systems with strangeness and exotic systems
2010
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 …
A MOLECULAR INTERPRETATION FOR THE $D^*_{s2}(2573)$, THE PREDICTION OF NOVEL EXOTIC CHARMED MESONS AND NARROW N*, Λ* RESONANCES AROUND 4.3 GeV
2011
In this talk we review the vector-vector and vector-baryon interaction within the hidden gauge formalism in a coupled channel unitary approach. The vector-vector interaction is studied for all the sectors not studied before: C = 0; S = 1 (hidden-charm), C = 1, S = 1, and the flavor exotic sectors C = 1; S = -1, 2 and C = 2; S = 0, 1, 2. We find nine states, four of them in the C = 1; S = 1 sector, where one can be identified with the [Formula: see text] and it is interpreted as a D* K* molecular state. The other five resonances are found in the flavor exotic sectors C = 1; S = -1, C = 2; S = 0, 1 and can be considered as [Formula: see text], D* D* and [Formula: see text] molecular states. …
Longitudinal dynamics of multiple conserved charges
2021
Abstract It is the goal of the RHIC BES program and the future FAIR and NICA facilities to produce compressed baryonic matter. In experiments such as these, strong gradients in baryon density are expected, and therefore the diffusion of baryon number could play a major role in the description of the fireball. The constituents of the produced matter carry a multitude of conserved charges, namely the baryon number, strangeness and electric charge, so that the diffusion currents of conserved charge couple with each other. Therefore, baryon density gradients in the above-mentioned high-density collision experiments will generate equalizing currents in all conserved charges. In common fluid dyna…
Dynamically generatedN*andΛ*resonances in the hidden charm sector around 4.3 GeV
2011
The interactions of $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\Sigma}}_{c}$-$\mathrm{D\ifmmode \bar{}\else \={}\fi{}}{\ensuremath{\Lambda}}_{c}$, ${\mathrm{D\ifmmode \bar{}\else \={}\fi{}}}^{*}{\ensuremath{\Sigma}}_{c}$-${\mathrm{D\ifmmode \bar{}\else \={}\fi{}}}^{*}{\ensuremath{\Lambda}}_{c}$, and related strangeness channels, are studied within the framework of the coupled-channel unitary approach with the local hidden gauge formalism. A series of meson-baryon dynamically generated relatively narrow ${N}^{*}$ and ${\ensuremath{\Lambda}}^{*}$ resonances are predicted around 4.3 GeV in the hidden charm sector. We make estimates of production cross sections of these predicted res…
Correlators of left charges and weak operators in finite volume chiral perturbation theory
2002
We compute the two-point correlator between left-handed flavour charges, and the three-point correlator between two left-handed charges and one strangeness violating \Delta I=3/2 weak operator, at next-to-leading order in finite volume SU(3)_L x SU(3)_R chiral perturbation theory, in the so-called epsilon-regime. Matching these results with the corresponding lattice measurements would in principle allow to extract the pion decay constant F, and the effective chiral theory parameter g_27, which determines the \Delta I = 3/2 amplitude of the weak decays K to \pi\pi as well as the kaon mixing parameter B_K in the chiral limit. We repeat the calculations in the replica formulation of quenched c…
S=--1 Meson-Baryon Scattering in Coupled Channel Unitarized Chiral Perturbation Theory
2002
The $s-$wave meson-baryon scattering amplitude is analyzed for the strangeness $S=-1$ and isospin I=0 sector in a Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry. Four two-body channels have been considered: $\bar K N$, $\pi \Sigma $, $\eta \Lambda $, $ K \Xi$. The needed two particle irreducible matrix amplitude is taken from lowest order Chiral Perturbation Theory in a relativistic formalism. Off-shell behaviour is parameterized in terms of low energy constants, which outnumber those assumed in previous works and provide a better fit to the data. The position of the complex poles in the second Riemann sheet of the scattering amplitude determine masses and widths of …