Search results for "Strangeness"

Hypernuclear Spectroscopy with Electron Beams

2011

A Λ-hyperon bound to a nuclear core, forming a hypernuclei, is a unique probe of the interior of hadronic many-body systems. Only recently, the spectroscopy of Λ-hypernuclei with electron beams was realized. Today, two places worldwide offer the possibility to study hypernuclei with high intensity continuous electron beams: MAMI at Mainz, Germany, and Jefferson Lab (JLab), Virginia. At least two different techniques exist for such studies: reaction spectroscopy, which requires two high-resolution spectrometers, one for kaons and one for the scattered electrons, and decay particle spectroscopy of hyperfragments. In the latter case a strangeness tagger in forward direction is of great advanta…

10.3 Mixing and Decay of Neutral Flavoured Mesons

2008

Progress and open questions in the physics of neutrino cross sections at intermediate energies

2014

New and more precise measurements of neutrino cross sections have renewed the interest in a better understanding of electroweak interactions on nucleons and nuclei. This effort is crucial to achieve the precision goals of the neutrino oscillation program, making new discoveries, like the CP violation in the leptonic sector, possible. We review the recent progress in the physics of neutrino cross sections, putting emphasis on the open questions that arise in the comparison with new experimental data. Following an overview of recent neutrino experiments and future plans, we present some details about the theoretical development in the description of (anti)neutrino-induced quasielastic scatter…

Predictions for pentaquark states of hidden charm molecular nature and comparison with experiment

2016

Predictions for hidden charm molecules, with and without strangeness, were made prior to the LHCb experiment. We discuss these issues and how these states can be observed in the reactions, Λ b → J / ψK − p , Λ b → J / ψη Λ, Λ b → J / ψπ − p , Λ b → J / ψK 0 Λ and Ξ − b → J / ψK − Λ by looking at the invariant mass distributions for J / ψp or J / ψ Λ.

Λb→J/ψK0Λreaction and a hidden-charm pentaquark state with strangeness

2016

We study the Lambda(b) -> J/psi K-0 Lambda reaction considering both the K-0 Lambda interaction with its coupled channels and the J/psi Lambda interaction. The latter is described by taking into account the fact that there are predictions for a hidden-charm state with strangeness that couples to J/psi Lambda By using the coupling of the resonance to J/psi Lambda from these predictions, we show that a neat peak can be observed in the J/psi Lambda invariant mass distribution, rather stable under changes of unknown magnitudes. In some cases, one finds a dip structure associated to that state, but a signal of the state shows up in the J/psi Lambda spectrum.

Observation of a Near-Threshold Structure in the K+ Recoil-Mass Spectra in e+e−→K+(Ds−D*0+Ds*−D0)

2021

We report a study of the processes of e^{+}e^{-}→K^{+}D_{s}^{-}D^{*0} and K^{+}D_{s}^{*-}D^{0} based on e^{+}e^{-} annihilation samples collected with the BESIII detector operating at BEPCII at five center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7  fb^{-1}. An excess of events over the known contributions of the conventional charmed mesons is observed near the D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0} mass thresholds in the K^{+} recoil-mass spectrum for events collected at sqrt[s]=4.681  GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5_{-2.6}^{+1.8}±2.1)  MeV/c^{2} and (…

Chiral dynamics in systems with strangeness

2002

In this talk a brief review of several problems involving systems with strangeness is made. In the first place one shows how the $\Lambda (1405)$, $\Lambda(1670)$ and $\Sigma(1620)$ states, for $S = -1$, and the $\Xi(1620)$ for $S= -2$ are generated dynamically in the context of unitarized chiral perturbation theory. The results for the $\bar{K}N$ interaction are then used to evaluate the $K^- d$ scattering length. Results obtained for the kaon selfenergy in a nuclear medium within this approach, with application to $K^-$ atoms, are also mentioned. Finally a few words are said about recent developments in the weak decay of $\Lambda$ hypernuclei and the puzzle of the $\Gamma_n/\Gamma_p$ rati…

Spin, parity and nature of the Xi(1620) resonance

2002

Using a unitary extension of chiral perturbation theory with a lowest-order s -wave SU(3) chiral Lagrangian we study low-energy meson-baryon scattering in the strangeness S = − 2 sector. A scattering-matrix pole is found around 1605 MeV which corresponds to an s -wave Ξ resonance with J P = 1 / 2 − . We identify this resonance with the Ξ ( 1620 ) state, quoted by the Particle Data Group with I = 1 / 2 but with unknown spin and parity. The addition of the S = − 2 state to the recently computed Λ ( 1670 ) , Σ ( 1620 ) , and N ( 1535 ) states completes the octet of J P = 1 / 2 − resonances dynamically generated in this chiral unitary approach.

Molecular interpretation of the XYZ states

2012

We study the vector – vector system including all the possible channels with quantum numbers charm = 0, strangeness = 0 around the energy region of 4000 MeV. New states with hidden charm around 4000MeV have been discovered by the B factories. They are intriguingly close to the D*D¯*${D^*}{ar D^*}$ and Ds*D¯s*$D_s^*ar D_s^*$ thresholds and do not have the properties of the charmonium states.We study the possible formation of D*D¯*${D^*}{ar D^*}$ and Ds*D¯s*$D_s^*ar D_s^*$ bound states in the framework of the Hidden Gauge formalism and discuss some of the models that favor the molecular assumption of some XYZ states: The hidden gauge formalism, Heavy baryon Chiral Perturbation Theory and the …

Semi-leptonic charm baryon decays in the relativistic spectator quark model

1991

We calculate the exclusive semi-leptonic charm baryon decays of the lowest lying charm baryon states into the ground state strangeness baryons using the covariant spectator quark model approach. We present results on rates,q 2- andE l -spectra as well as on the angular decay distribution in the cascade decay $$\Omega _c \to \Omega ( \to \Xi \pi ,\Lambda {\rm K})$$ .