A Wideband Intelligent Trigger

University Of California-Irvine, Irvine CA

Investigators

Abstract

The ability to observe very low-energy electrons is crucial for the physics reach of the Super-Kamiokande (SK) experiment at the Kamioka mine in Japan. It influences the sensitivity to a wide range of physics topics from solar neutrinos to proton decay to particle identification. This work will develop new software and hardware for a new very low-energy trigger for the SK experiment. In late 2008, all of the electronics and data acquisition components in SK were replaced, leading to an entirely new data-taking approach using real-time software triggers; however, the initial computing and storage capabilities of this system only allow an energy threshold similar to that of the previous system. The Wideband Intelligent Trigger (WIT) system will provide sufficient connectivity, storage, and CPU power to completely process the data in the un-triggered, raw stream and extract electrons with high efficiency down to a total energy of 3 MeV, which is the limit of stable and reliable event reconstruction at SK. It operates by evaluating each data block independently in a massively parallel fashion and applying new software algorithms that culminate in a two-stage vertex reconstruction. This procedure reduces the background, the processing time and the final data size to a manageable level. The new low energy threshold will: (1) improve SK's sensitivity to spectral distortions of solar neutrinos due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect, bringing new sensitivity to to the as-yet-unobserved upturn in the solar neutrino spectrum expected from large mixing angle MSW oscillations; (2) provide new functionality by acting as a galactic supernova burst trigger; and (3) by adding Gadolinium to the water, enable SK to detect neutrons with high efficiency, significantly reducing the atmospheric neutrino background to both the observation of proton decay and relic supernova neutrinos. The research supported by this award is an example of how advances in computing can extend the capabilities of existing instruments for basic research, effectively extending the physics reach and leveraging existing investments. The Kamioka Laboratory in Japan has an extensive program for involving the public, undergraduate students and K-12 students in the excitement of physics research. The postdoc and graduate student working on WIT will be integrated into these activities and lectures on the physics that comes from looking at low-energy events in Super-Kamiokande. Undergraduate students from the U.S. will work with this group in Japan during the summer for one to two months to help implement WIT and to help analyze the first data. They will maintain a collaborative relationship with faculty at a local undergraduate institution. They will also participate in the effort by attending Super-Kamiokande collaboration meetings, taking shifts at the experiment and participating in the scientific research.