Neutrino-KAVE: An Immersive Visualization and

Fitting Tool for Neutrino Physics Education1,2Elizabeth Izatta

2Department of Electrical Engineering andComputer Science

University of California, Berkeley

3Kate Scholbergb

3Physics Department

Duke University

1Regis Kopperc

1Duke immersive Virtual Environment

Pratt School of Engineering, Duke University

ABSTRACT

Water Cherenkov neutrino detectors, like the existing Super-Kamiokande ("Super-K") and the planned Hyper-Kamiokande("Hyper-K") detectors, are used to study neutrino particle physics.These detectors consist of large vessels holding many thousandsof tons of water, as well as tens of thousands of photomultipliertubes. Such detectors produce large and multi-layered datasetswell-suited to immersive visualization and interaction. We havedeveloped a novel virtual reality (VR) application calledNeutrino-KAVE which functions as an visualization and datainteraction application. Neutrino-KAVE displays the collocationof photon sensors and their color-coded data within a to-scalerepresentation of the Super-K or Hyper-K detector, and provides anew visualization technique for neutrino interaction patterns.Neutrino-KAVE also provides both a mechanism for modifyingaspects of the presented data set, and a user interface for systemcontrol of this multifaceted application. In this paper, we describein detail our implementation and design choices. We also reporton its use cases, initial reception, and future development.

Keywords: Immersion, Computer Simulation, Visualization.

Index Terms: I.3.7 [Three-Dimensional Graphics and Realism]:Virtual Reality; H.5.2 [User Interfaces]: Interaction Styles

1 INTRODUCTION

While there are existing visualizations for the study of particlephysics[1][2], to the best of our knowledge this is among the firstreports of an immersive visualization environment for the researcharea of neutrino physics. There are existing programs used bymodern physicists for the display of experimental data, such as theSuperscan program used by our physics collaborators, but thesemay not always be ideal for the display, exploration, andevaluation of the data, especially for novice users. An immersivevisualization follows naturally from these dense, large, andspatially-distributed datasets, and encourages exploration of thedata.

We have thus created a fully immersive application for viewingdatasets and fitting events generated from the existing Super-Kamiokande detector (Super-K), and the planned Hyper-Kamiokande detector (Hyper-K) [4][7]. This application,extending the in-house Superscan application used by our physicscolleagues, places the user in a to-scale representation of eitherdetector and allows the user to explore the space, change

visualization modes, and switch between datasets called “events.”In contrast to existing 2D visualizations, our application providesa truly inside-out viewpoint, which is regarded as a more intuitiveapproach that allows better understanding of the data [3].Furthermore, our application allows for reconstruction ofproperties of neutrino events (“hand fitting”), an interactive modein which the user tweaks the parameters of the data set itself. We designed and implemented Neutrino-KAVE in a six-sided,rear-projected CAVE to provide a full 360-degree immersive viewfor our visualization. It measured 3m x 3m x 3m, with aresolution of 1050 x 1050 pixels per screen. CrystalEyes glasseswere used to provide active stereoscopy, and an InterSense IS-900Wireless tracking system provided 6-DOF head and hand trackingvia a head tracker and a five-button wand with joystick. We usedthe Syzygy library [6] to provide cluster-based rendering for ourCAVE system.

2 NEUTRINO-KAVE

2.1 Detectors and Datasets

Our application currently visualizes data sets from two Water-Cherenkov detectors: Super-K and Hyper-K. The Super-K is avertically-oriented cylinder, 41.4 meters tall 39.3 meters indiameter, which contains 13,032 photomultiplier tubes (PMTs).Hyper-K, Super-K's planned successor, will take the form of twoapproximately cylindrical tanks lying side by side, each 48 metersin width, 54 meters in height, and 250 meters in length. Hyper-Kwill contain roughly 124,000 PMTs.

a e-mail: liz@berkeley.edub e-mail: schol@phy.duke.educ e-mail: regis.kopper@duke.edu

Figure 1: Neutrino-KAVE.

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Data sets from either detector take the same form, being a list of“events” generated when neutrinos interacts with a watermolecule. This releases a pattern of energy characteristic of theinteraction, which is then captured by the PMTs in the detectorand stored as a pair of charge and time-of-impact points. After thedata are stored, the vertex of interaction, in addition to otherpieces of data, can be calculated and added to the data file.

2.2 Event Visualization

In Neutrino-KAVE, the chosen detector structure is representedby a wire-frame cylinder to an accurate scale. Placed in theirproper relative positions to this structure, all of the PMTs aredisplayed as discs. They can be colored by either their charge ortime values, and optionally scaled by their charge value. The vertex of the neutrino collision is displayed as a whitesphere. From this, for each final state particle, a wireframe coneis projected outward with a dynamically calculated Cherenkovcone angle. This extends to the walls of the detector, where acircle describing the intersection of the cone and detector isdrawn. The color of this circle represents the particle'sclassification. In addition, for each final state particle, a thick,short center line terminating in a cone is drawn extending from thevertex, indicating the direction of the Cherenkov radiation.

2.2.1 Fitting Mode

Besides visualization, a major use case for event display programsis as an interactive data fitting platform. Output from a detectorcomes in a raw form in which information regarding the vertex isunknown. This must be calculated by calibrating the intersectionof a geometrical cone, representing the Cherenkov radiation of theevent, against the PMT data, in such a way that the particlehypothesis best fits the given data set. This is done most often viamathematical analysis, but in some cases doing this work by handcan be more accurate, or in the case of education, beneficial. We have implemented an exploratory special fitting mode ofNeutrino-KAVE, in which the user can physically reach out andgrab either the vertex itself, or one of the cone shapes signifyingthe direction of a cone. By moving these two markers, a locationand orientation of the vertex can be specified by hand.

2.3 User Interface

Powering all of this, Neutrino-KAVE's system architecturehinges around a system state based around the currently displayeddata event. We provide a heads-up display (HUD) object that ispermanently attached to the user's hand, providing basicinformation about this state. In order to view information in moredepth, or to modify this system state, we created a 3D userinterface in the form of a hierarchical system control menu. Tokeep our application's interface simple, all menu control is basedoff the trigger button on our wand. As such, by pressing thisbutton, the system-control menu is created and locked intoposition just above the information HUD. This menu is controlledwith ray-casting[9], allowing the user to point at whichever menuitem they wish to select. Pressing again will either select thecurrently indicated item, or if no item is indicated, close the menu. From within these menus, two notable features are accessible:Data Displays and Wrist-Bound Time Playback. The former is amodule we developed to display large amounts of text to the userin a readable format. The latter is a technique to map a systemtime variable to the user's wrist rotation, which is then used tointeractively determine which data is drawn. Finally, to round out the features of Neutrino-KAVE's interface,we provided a 3D steering technique [9] to allow the user to fly

around and explore the visualization. This technique used thewand's orientation and joystick to indicate a path of motion.

3 CONCLUSIONS AND FUTURE WORK

We have described the development of the Neutrino-KAVEapplication. This immersive application provides the ability toview data from both Super-K and Hyper-K. within to-scalerepresentations. One user described Neutrino-KAVE as “moreintuitive than Superscan,” demonstrating exactly the result weaimed to achieve: an intuitive and immersive alternative toprograms traditionally used by physicists. Currently, we use Neutrino-KAVE as an outreach and educationtool to introduce new physics students and members of the publicto Super-K, Hyper-K, the T2K experiment, and water-Cherenkovdetectors [5]. Neutrino-KAVE grants them a spatial and intuitivegrasp of the function of Super-K and Hyper-K that is difficult toachieve through other means. In addition to education, there arenumerous other applications to be explored, including viewingevent data in order to hand-pick interesting events frombackground noise, and to assist with the ongoing design of theHyper-K detector. Future plans for development include numerous touch-ups andmodifications in response to user feedback, as well as running afull usability evaluation. We plan on comparing Neutrino-KAVEto Superscan in both novice and advanced users. It is also plannedto port Neutrino-KAVE to be used by head-mounted displaysystems and by desktop VR solutions in order for it to be locallyavailable to our physics colleagues and their collaborators.Finally, we hope to continue to develop Neutrino-KAVE in orderto support real time and interactive generation of event data basedon user-controlled parameters. Development of greaterinteractivity in this way could allow users to run simulations orreconstructions of event information, and view the output, allwithout leaving the CAVE.

ACKNOWLEDGEMENTS

We would like to thank Nick Bodnar, Alex Himmel, Ed Kearns,Chris Walter, the National Science Foundation, and the Super-Kcollaboration, as well as David Zielinski, Rachael Brady, andRyan P. McMahan, for all of their help and support in this project.

REFERENCES

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[2] X. Wei et al., “Case Study: Visualization of Particle Track Data,” inVisWeek 2001, Washington DC, 2001 pp. 465-468.

[3] C. Cruz-Neira, “Scientists in Wonderland,” in IEEE 1993Symposium of Research Frontiers in Virtual Reality, San Jose, CA,1993, pp. 59.

[4] S. Fukuda et al., “The Super-Kamiokande Detector,” NuclearInstruments and Methods in Physics Research A, Elsevier,Netherlands, pp. 418-462, 2003.

[5] K. Abe et al., “The T2K experiment,” Nuclear Instruments andMethods in Physics Research A, Elsevier, Netherlands, pp. 106-135,2011.

[6] B. Schaeffer and C. Goudeseune, "Syzygy: Native PC Cluster VR,"Proceedings of IEEE Virtual Reality (VR), pp. 15-22, 2003.

[7] K. Abe et al., “Letter of Intent: The Hyper-Kamiokande Experiment--- Detector Design and Physics Potential ---,” eprintarXiv;1109.3262, 2011.

[8] Izatt et al., “Super-KAVE: An Immersive Visualization Tool forNeutrino Physics,” presented at the IEEE Virtual RealityConference, Orlando, Florida, 2013.

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