The BDX-MINI detector for Light Dark Matter search at JLab

This paper describes the design and performance of a compact detector, BDX-MINI, that incorporates all features of a concept that optimized the detection of light dark matter in the MeV-GeV mass range produced by electrons in a beam dump. It represents a reduced version of the future BDX experiment expected to run at JLAB. BDX-MINI was exposed to penetrating particles produced by a 2.176 GeV electron beam incident on the beam dump of Hall A at Jefferson Lab. The detector consists of 30.5 kg of PbWO$$_4$$ 4 crystals with sufficient material following the beam dump to eliminate all known particles except neutrinos. The crystals are read out using silicon photomultipliers. Completely surrounding the detector are a passive layer of tungsten and two active scintillator veto systems, which are also read out using silicon photomultipliers. The design was validated and the performance of the robust detector was shown to be stable during a six month period during which the detector was operated with minimal access.

SLAC T-510: Experimental validation of particle-level simulations of radio emission from particle cascades

The SLAC T-510 experiment was designed to measure radio emission from particle cascades in a controlled laboratory setting and compare measurements with predictions from particle-level simulations. An electron beam incident upon a dense dielectric target produced a particle cascade in the presence of a strong magnetic field. We previously reported the agreement between data and simulations within systematic uncertainties, the largest being the reflection of radio emission within the target. A follow-up experiment has since been carried out to characterize the reflections and include them in simulations. In this contribution we report these new results. The uncertainties in the experiment are greatly reduced, and the features in the observed emission are well understood.

Single-layer and bilayer graphene superlattices: collimation, additional Dirac points and Dirac lines

We review the energy spectrum and transport properties of several types of one-dimensional superlattices (SLs) on single-layer and bilayer graphene. In single-layer graphene, for certain SL parameters an electron beam incident on an SL is highly collimated. On the other hand, there are extra Dirac points generated for other SL parameters. Using rectangular barriers allows us to find analytical expressions for the location of new Dirac points in the spectrum and for the renormalization of the electron velocities. The influence of these extra Dirac points on the conductivity is investigated. In the limit of δ -function barriers, the transmission T through and conductance G of a finite number of barriers as well as the energy spectra of SLs are periodic functions of the dimensionless strength P of the barriers, , with v F the Fermi velocity. For a Kronig–Penney SL with alternating sign of the height of the barriers, the Dirac point becomes a Dirac line for P = π /2+ nπ with n an integer. In bilayer graphene, with an appropriate bias applied to the barriers and wells, we show that several new types of SLs are produced and two of them are similar to type I and type II semiconductor SLs. Similar to single-layer graphene SLs, extra ‘Dirac’ points are found in bilayer graphene SLs. Non-ballistic transport is also considered.