The KLOE-2 High Energy Tagger Detector

TL;DR

The paper describes the design, implementation, and initial testing of the High Energy Tagger detector at DAFNE, which measures scattered leptons to identify gamma-gamma events in electron-positron collisions.

Contribution

It introduces a novel detector system with custom electronics for precise timing and position measurements to improve gamma-gamma physics event reconstruction.

Findings

Successful commissioning of the detector system.

Achieved a timing resolution of approximately 500 ps.

Demonstrated effective bunch crossing identification.

Abstract

In order to fully reconstruct to the reaction e+e- to e+e- gamma-gamma in the energy region of the phi meson production, new detectors along the DAFNE beam line have to be installed in order to detect the scattered e+e-. The High Energy Tagger (HET) detector measures the deviation of leptons from their main orbit by determining their position and timing so to tag gamma-gamma physics events and disentangle them from background. The HET detectors are placed at the exit of the DAFNE dipole magnets, 11 m away from the IP, both on positron and electron lines. The HET sensitive area is made up of a set of 28 plastic scintillators. A dedicated DAQ electronics board based on a Xilinx Virtex-5 FPGA have been developed for this detector. It provides a MultiHit TDC with a time resolution of the order of 500 ps and the possibility to acquire data any 2.5 ns, thus allowing to clearly identify the correct bunch crossing. First results of the commissioning run are presented.