Overview of DAQ system of J-PARC E16 experiment

Hadrons are elementary excitations of the QCD vacuum, and their properties reflect the state of the vacuum. The properties of the vacuum are theoretically suggested to be modified at finite density or temperature. Therefore, measuring hadrons under such an environment will lead to understanding of the property of QCD vacuum.

The J-PARC E16 experiment focuses on a measurement of the spectral modifications of vector mesons at nuclear density. In the experiment, 30 GeV primary proton beams are irradiated on carbon and copper targets with the interaction rate of 10 MHz to produce vector mesons, rho, omega and phi. We measure the spectra of these mesons at nuclear density from their di-lepton decay.

In order to obtain large statistics, we constructed a new spectrometer having high rate capability to detect dileptons produced in pA reaction. The total number of detector channels is 150,000 and the trigger is generated from 2,600 discriminator signals at rates of up to several MHz. DAQ system is important for handling the detectors with such a large number of channels at high rate.

The experiment has been successfully launched at a J-PARC high momentum beam line in 2020, and four commissioning runs have been carried out so far.

In this presentation, we give an overview the E16 DAQ system, particularly recent approaches for the streaming DAQ.