86859005
Instrumentation for Theory-Inspired Photocathode Development within the Large Area Picosecond Photodetector (LAPPD) Project
Abstract We have designed and are commissioning a laboratory for the growth and characterization of photocathodes at Argonne National Laboratory. Two growth facilities, a versatile ultra high vacuum growth chamber and an industrial photomultiplier production facility, allow the investigation of fundamental aspects of the cathode growth and the development, modification and implementation of recipes in an industrial production environment. The instrumentation allows the study of optical properties, electrical behaviors and spectral response of the cathode.
55912862
Alkali Antimonide Photocathodes in a Can
The next generation of x-ray light sources will need reliable, high quantum efficiency photocathodes. These cathodes will likely be from the alkali antimonide family, which currently holds the record for highest average current achieved from a photoinjector. In this work, we explore a new option for delivering these cathodes to a machine which requires them: use of sealed commercial vacuum tubes. Several sealed tubes have been introduced into a vacuum system and separated from their housing, exposing the active photocathode on a transport arm suitable for insertion into an injector. The separation was achieved without large loss of QE. These cathodes have been compared to those grown via traditional methods, both in terms of QE and in terms of crystalline structure, and found to be similar.
118071326
High Performance Photocathodes based on Molecular Beam Epitaxy Deposition for Next Generation Photo Detectors and Light Sources
The development of high-performance photocathodes is a key challenge for future accelerator and particle physics applications. In this paper photocathode growth through molecular beam epitaxy is introduced as a promising technique to obtain robust, highly efficient alkali-antimonide based photocathodes. Recent research shows that the quantum efficiency of photocathodes can be significantly enhanced through control of the photocathode crystallinity. Molecular beam epitaxy allows for cost-effective growth of large-area photocathodes with excellent control of the stoichiometry and crystallinity, making photocathodes with peak quantum efficiencies exceeding 35% routine.
117836636
Re-analysis of the $\Lambda(1520)$ photoproduction reaction
Based on previous studies that support the important role of the $N^*(2120) D_{13}$ resonance in the $\gamma p \to K^+ \Lambda(1520)$ reaction, we make a re-analysis of this $\Lambda(1520)$ photoproduction reaction taking into account the recent CLAS differential cross-section data. In addition to the contact, $t-$channel $\bar K$ exchange, $s-$channel nucleon pole and $N^*(2120)$ [previously called $N^*(2080)$] resonance contributions, which have been already considered in previous works, we also study the $u-$channel $\Lambda(1115)$ hyperon pole term. The latter mechanism has always been ignored in all theoretical analysis, which has mostly relied on the very forward $K^+$ angular LEPS data. It is shown that when the contributions from the $N^*(2120)$ resonance and the $\Lambda(1115)$ hyperon are taken into account, both the new CLAS and the previous LEPS data can be simultaneously described. We also show that the contribution from the $u-$channel $\Lambda(1115)$ pole term produces an enhancement for large $K^+$ angles, and it becomes more and more relevant as the photon energy increases, being essential to describe the CLAS differential cross sections at backward angles. Furthermore, we find that the new CLAS data also favor the existence of the $N^*(2120)$ resonance, and that these measurements can be used to further constrain its properties.
62797135
Faddeev fixed center approximation to the $N\bar{K}K$ system and the signature of a $N^*(1920)(1/2^+)$ state
We perform a calculation for the three-body NK-barK scattering amplitude by using the fixed-center approximation to the Faddeev equations, taking the interaction between N and K-bar, N and K, and K-bar and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three-body scattering amplitude and suggest that a NK-barK hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N* resonance around 1920 MeV with spin-parity J{sup P}=1/2{sup +}. The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible application in similar problems, as an explorative tool to determine bound or quasibound three-hadron systems.
124596955
Hadron Dynamics with Vector Mesons: Matching Theory and Experiment to Identify New Resonances
In this paper, we discuss the γp → KΣ and γn → KΣ reactions, with a peculiar behavior around the K∗0Λ threshold, due to a 1/2− resonance around 2035 MeV. Similarly, we discuss a BES experiment, J/ψ → ηK∗0K̄∗0 decay, which supports the existence of a new h1 resonance around 1830 MeV that was predicted from the vector–vector interaction. A short discussion is then made about recent advances in the charm and beauty sectors.
118554249
A new perspective on the $\Delta_{5/2^{+}}(2000)$ puzzle
We argue that $\Delta_{5/2^{+}}(2000)(\ast\ast),$ cataloged as a resonance in the Particle Data Book Review (PDG), should be interpreted instead as two distinctive resonances, $\Delta_{5/2^{+}}(\sim1740)$ and $\Delta_{5/2^{+}}(\sim2200)$. Our argument is based on a solution of the $\pi\Delta\rho$ problem in a Fixed Center Approximation (FCA) to the Fadeev equations. $\Delta_{5/2^{+}}(\sim1740)$ can then be interpreted as a $\pi-(\Delta \rho)_{N(1675)}$ bound state. As a corollary $\Delta_{1/2^{+}}(1750)(\ast)$ can be understood as a $\pi N_{1/2^{-}}(1650)$ bound state.