Charged Particles In Final State Research Articles

New graph-neural-network flavor tagger for Belle II and measurement of sin 2ϕ1 in B0→J/ψKS0 decays

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral B mesons produced in ϒ(4S) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using B decays to flavor-specific hadronic final states reconstructed in a 362 fb−1 sample of electron-positron collisions collected at the ϒ(4S) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40±0.43±0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use B0→J/ψKS0 decays to measure the mixing-induced and direct CP violation parameters, S=(0.724±0.035±0.009) and C=(−0.035±0.026±0.029). Published by the American Physical Society 2024

The strangeness program at GlueX

The GlueX experiment located at Jefferson Lab studies the spectrum of hadrons using photoproduction on a LH2 target in a wide variety of final states. With its detector system capable of measuring neutral and charged final state particles over almost the full solid angle, and very good particle identification capabilities, GlueX can measure many different hadrons containing strangeness. A linearly polarized photon beam allows the measurement of polarization observables, which contain information about the production mechanisms involved in generating strange particles in photoproduction. In addition, GlueX can perform precise cross-section measurements, which help to study the spectrum of strange hadrons. In this presentation, the GlueX experiment is introduced, and recent progress of its strangeness program is discussed. We present recent results on Σ0 beam asymmetries, Λ(1520) spin-density matrix elements and ongoing studies of the Λ(1405) lineshape. We also present our recent progress on measurements of ΛΛ̅ and Ξ(∗) photoproduction. Also, future prospects for strangeness measurements at GlueX are discussed.

An (e, 2e + ion) study of low-energy electron-impact ionization and fragmentation of carbon dioxide

SynopsisWe study the ionization and fragmentation of carbon dioxide (CO2) induced by low-energy (E0 = 66 eV) electron-impact using a reaction microscope. The momentum vectors of all three charged final state particles, two outgoing electrons and one fragment ion, are detected with an (e, 2e + ion) triple coincidence method. The fragmentation pathways of carbon dioxide for formation of the CO+2, CO+, O+ and C+ ions are investigated by measuring the ion kinetic energy spectra and the binding energy spectra where a binding energy resolution of 2.0 eV has been achieved in the experiment.

High-resolution (e, 2e + ion) study of electron-impact ionization and fragmentation of methane.

The ionization and fragmentation of methane induced by low-energy (E0 = 66 eV) electron-impact is investigated using a reaction microscope. The momentum vectors of all three charged final state particles, two outgoing electrons, and one fragment ion, are detected in coincidence. Compared to the earlier study [Xu et al., J. Chem. Phys. 138, 134307 (2013)], considerable improvements to the instrumental mass and energy resolutions have been achieved. The fragment products CH4 (+), CH3 (+), CH2 (+), CH(+), and C(+) are clearly resolved. The binding energy resolution of ΔE = 2.0 eV is a factor of three better than in the earlier measurements. The fragmentation channels are investigated by measuring the ion kinetic energy distributions and the binding energy spectra. While being mostly in consistence with existing photoionization studies the results show differences including missing fragmentation channels and previously unseen channels.

Low energy electron-induced break-up of the tetrahydrofuran molecule: An (e, 2e+ion) study

We study the low energy electron impact-induced ionization and fragmentation of the tetrahydrofuran molecule using the reaction microscope. All three charged final state particles, two outgoing electrons and one fragment ion are detected in coincidence. The binding energy spectra and fully differential ionization cross sections for different fragment species are determined. As result detailed insight into the ionization mechanisms can be gained and track structure simulations for the investigation of radiation action can be supported.

Reactions with three charged particles in final state

Three-particle Coulomb asymptotic states are derived. The knock-out reaction amplitude with distorted waves in the initial and final states is extracted using the Faddeev equations. The conditions are discussed under which this amplitude can be approximated by the distorted wave impulse amplitude. The influence of the Coulomb final state interaction on the differential quasielastic knock-out cross section is investigated. To this end the main singular part of the DWIA amplitude is singled out and compared with conventional approximations.