---
title: "Supernova Neutrino Burst Observatory Interactive Lab | Sandbox Physics"
description: "When should a sudden jump in neutrino events trigger a supernova alarm?"
canonical_url: "https://sandboxphysics.com/labs/supernova-neutrino-burst/"
language: "en"
page_type: "lab"
alternate_languages:
  zh-CN: "https://sandboxphysics.com/zh/labs/supernova-neutrino-burst/"
last_modified: "2026-10-27"
---

Neutrinos · D11 · Catch the first message

# Supernova Neutrino Burst Observatory

**When should a sudden jump in neutrino events trigger a supernova alarm?** When background alone would rarely produce it, even after you count every window you searched. Fix the expected background rate first. If you slide a time window through the data and pick the busiest stretch, the chance for that one window understates the false-alarm risk. Bound the chance that any window gets that busy; the single-window chance times the number of windows is one such bound.

Catch a simulated neutrino burst in a spherical scintillation detector. Freeze the event times, scan a trigger window across them, and follow one interaction from its flash of light to the collection sphere.

> Interactive simulation: open this page in a web browser to change the parameters and run the model.

This is a teaching simulation, not SN 1987A data and not a replica of JUNO, SNO+ or SNEWS. Events follow prescribed Poisson time profiles with an illustrative yield, and the counts scale with distance and exposure. Each flash is an ideal isotropic point, the refractive index is fixed and the whole sphere collects light. The Lab does not infer energy, flavor, direction or distance. The trigger uses only timestamps. Scan probabilities are conservative bounds for a known, steady background; they are not calibrated discovery significances or operational alerts. Sources and assumptions are listed below.

The same forty-second record

## The detector is quiet, then suddenly busy.

### Recorded event timeline

Show injected expectation

Mint bars: sampled counts. Shading: peak window. Solid line: selected event; dashed line: replay clock. Optional gold line: injected expectation, not recovered luminosity. Zero is the prescribed arrival onset at Earth.

Set a trigger on the same timestamps

### When would you trigger?

Window duration $2\,\mathrm{s}$ Count threshold $12$ Assumed background $0.2\,\mathrm{s^{-1}}$

- **Fixed-window tail at peak**: $\text{—}$
- **Threshold false-trigger bound**: $\text{—}$

Conditional on the assumed stationary background. Overlapping windows are dependent; the union bound remains valid. Changing settings after seeing the sample adds uncounted choices. No sigma, annual rate or real alert is inferred.

### The sliding-window scan

Every full window is evaluated on a fixed quarter-second grid. The first crossing is a simulated decision time, not a fitted stellar collapse time.

Look at one interaction

### From a point flash to the sphere

Event index

Ideal prompt isotropic light; 64 rays are geometric samples, not photoelectron yield. The full 5 m collection sphere and fixed index 1.5 omit scintillation delay, absorption, scattering and sensor response.

Model assumptions & primary sources

Illustrative mean: 120 detected candidates at 10 kpc and exposure one, scaled by exposure and inverse square of distance. Exposure changes candidate yield only; it does not resize the schematic sphere or scale the independently controlled background. Cooling is a truncated exponential over 30 seconds; Fast onset mixes 30% of a 0.4 second component and 70% cooling. Background is stationary Poisson. Uniform vertices fill the inner 4 m sphere, carry no sky direction and do not enter the trigger. No energy, cross-section, efficiency or flavor model; no SN 1987A events are reproduced.

- [SNEWS 2.0 · 2021](https://arxiv.org/abs/2011.00035)
- [SNEWS alert software · 2024](https://arxiv.org/abs/2406.17743)
- [DUNE supernova detection · 2021](https://link.springer.com/article/10.1140/epjc/s10052-021-09166-w)
- [Neutrino Physics with JUNO · 2015](https://arxiv.org/abs/1507.05613)

[Read SN 1987A →](https://sandboxphysics.com/stories/neutrinos/sn1987a-burst/) [Explore the global history →](https://sandboxphysics.com/stories/neutrinos/)

Physics tutorial

## A trigger is a decision, not a discovery.

**Background** In SN 1987A, independent underground instruments each recorded a short burst of neutrinos, and these bursts were linked to a stellar explosion seen in the sky. Today SNEWS combines reports from many detectors to give early warning, but each detector first has to decide whether its own stream of events looks unusual.

**Why it matters** A nearby source can produce a rush of interactions; a distant one may leave only a few. A lower count threshold catches more weak bursts, but steady background can cross it too. This Lab keeps sampling, replay and that decision apart.

Start with the essentials

- **Focus question**: How much does a convincing-looking cluster depend on your window, threshold and assumed background?
- **One-sentence intuition**: The same timestamps can lead to different trigger decisions, and a peak found by scanning many windows needs a probability bound for the whole scan, because its single-window tail alone is not the false-alarm probability.

### Core mathematical model

#### Expected signal count from distance and exposure

$$
\bar N_s=120\,a\left(\frac{10\,\mathrm{kpc}}{d}\right)^2
$$

The normalization is illustrative and does not predict counts for any named instrument. Relative exposure changes only the signal yield; the background has its own control, and the schematic chamber keeps the same size.

#### Assumed cooling profile

$$
F(t)=\frac{1-e^{-t/\tau}}{1-e^{-30\,\mathrm{s}/\tau}},\qquad 0\le t\le30\,\mathrm{s}
$$

Signal events arrive as a Poisson process whose rate changes in time; the expected number up to any moment is the mean yield times this cumulative profile. Fast onset adds a short component that carries 30% of the signal. There is no hydrodynamic supernova or flavor-evolution calculation behind it.

#### Count the events in one full window

$$
C_j=\sum_i\mathbf 1\{u_j-W<t_i\le u_j\},\qquad C_j\ge k\ \Rightarrow\ \text{candidate trigger}
$$

Window end times sit on a fixed quarter-second grid. The rule uses only the observed timestamps; the model's origin labels, the event vertices and the injected onset time do not enter the trigger.

#### Correct for scanning many windows

$$
p_k=\Pr\{\mathrm{Poisson}(bW)\ge k\},\quad\Pr\{\max_j C_j\ge k\}\le\min(1,Mp_k)
$$

The union bound stays conservative even though the windows overlap. It assumes a known, steady Poisson background. It covers one fixed choice of window and threshold; it does not cover retuning after looking at the record, or continuous monitoring over a year.

#### Light travel time from one flash

$$
L=-\mathbf r\cdot\hat{\mathbf q}+\sqrt{(\mathbf r\cdot\hat{\mathbf q})^2+R^2-|\mathbf r|^2},\qquad t_{\mathrm{hit}}=\frac{nL}{c}
$$

Each representative ray starts at the selected event vertex and ends on the same ideal 5 m collection sphere. The refractive index is 1.5, coordinates are in meters and optical times are in nanoseconds. The number of rays is not a photoelectron yield. The scintillation emission delay and the detector response are left out.

### Common difficulties

#### One window's tail is not the whole search

**Typical misconception** The smallest single-window tail is the false-alarm probability for the entire scan.

**Better mental model** Picking the peak gives a fluctuation many chances to appear. The scan bound counts every window on the prescribed grid; any further choice of model or settings needs its own correction.

#### Uniform vertices do not point to a star

**Typical misconception** The bright pattern inside the sphere shows the direction of the supernova.

**Better mental model** The deposits are prescribed to be uniform, only to illustrate the optics. The model has no directional interaction, no triangulation and no sky reconstruction.

### Run the experiment

1. 01

   #### Catch a burst

   Acquire Galactic burst and replay the event clock. Watch the half-second counts and the first threshold crossing.

   **What to observe:** The clock plays back a record that is already frozen; it does not generate new events. Gold marks the selected vertex and recent interactions, and mint marks the events collected so far.

2. 02

   #### Keep the record, change the decision

   Change the window duration and the count threshold in the analysis panel.

   **What to observe:** The event times stay fixed, but the peak count, the candidate crossing and the false-trigger bound all change together.

3. 03

   #### Try background alone

   Acquire Background only, restore this record’s background assumption, then lower the threshold.

   **What to observe:** A background fluctuation can set off the trigger. The probability bound says how rare that is under the stated background; it does not turn the trigger into a stellar discovery.

4. 04

   #### Follow one interaction

   Select an event on the timeline, choose Follow this flash in 3D, then drag the optical clock.

   **What to observe:** Representative light rays stop on the collection sphere, and the histogram is computed from those same path lengths. The burst clock and the optical clock describe different time scales.

Physical conclusion

A useful burst trigger needs a time record, a stated background hypothesis and a clearly defined search. The light flash shows how one interaction is collected; on its own it does not establish the source in the sky.

## Related experiments and articles

Continue exploring

### How detectors see a neutrino

A neutrino leaves only light, charge or a pair of signals close in time. How does each detector turn that into a direction, an energy or a source?

1. [Lab **Reactor Antineutrino Coincidence** Select prompt and delayed signals against accidental pairs.](https://sandboxphysics.com/labs/reactor-coincidence/)
2. [Lab **Cherenkov Light & Detector Rings** Turn charged-particle geometry into a recorded light pattern.](https://sandboxphysics.com/labs/cherenkov-rings/)
3. [Lab **Liquid Argon Time Projection Chamber** Turn electron arrival times and wire projections into calibrated slice centroids.](https://sandboxphysics.com/labs/liquid-argon-tpc/)
4. [Lab **IceCube: From Sensor Hits to a Track** Infer a track direction from the recorded sensor times.](https://sandboxphysics.com/labs/icecube-reconstruction/)
5. [You are here **Supernova Neutrino Burst Observatory** Scan a frozen burst record, then inspect one interaction at the optical timescale.](https://sandboxphysics.com/labs/supernova-neutrino-burst/)
6. [Lab **Neutrino Sky Search Observatory** Search frozen neutrino directions and compare a local hotspot with paired finite-grid background trials.](https://sandboxphysics.com/labs/neutrino-sky-search/)

Neutrinos · Reading path

### Build a new way to observe the sky

Articles on this path that use this experiment, followed by the other experiments they suggest.

1. [Article **SN 1987A: a supernova seen from underground**](https://sandboxphysics.com/stories/neutrinos/sn1987a-burst/)
2. [Lab **Reactor Antineutrino Coincidence**](https://sandboxphysics.com/labs/reactor-coincidence/)
3. [Lab **Cherenkov Light & Detector Rings**](https://sandboxphysics.com/labs/cherenkov-rings/)

Neutrinos · Reading path

### Read evidence, data and worldwide contributions

Articles on this path that use this experiment, followed by the other experiments they suggest.

1. [Article **When can a few neutrino events become evidence?**](https://sandboxphysics.com/stories/neutrinos/few-neutrino-events-statistical-evidence/)

Fields & matter · Starter path

## From a field to an electron microscope

Map an electric field and steer a charged particle. Then find the electron's wavelength and use electron beams to see a crystal and a surface.

[Start here → **Make an Electric Field Visible** Move the probe around a dipole and check that the field always points downhill on the potential landscape. Observe · 8 min](https://sandboxphysics.com/labs/electric-field/)

1. [1 Make an Electric Field Visible](https://sandboxphysics.com/labs/electric-field/)
2. [2 A Charge Bending through Fields](https://sandboxphysics.com/labs/charged-particle/)
3. [3 Electron Wavelength & Voltage](https://sandboxphysics.com/labs/electron-wavelength/)
4. [4 Electron Diffraction & Reciprocal Space](https://sandboxphysics.com/labs/electron-diffraction/)
5. [5 TEM Bright Field, Dark Field & SAED](https://sandboxphysics.com/labs/tem-mode-selector/)
6. [6 SEM Secondary-Electron Topography](https://sandboxphysics.com/labs/sem-topography/)

[View the full path →](https://sandboxphysics.com/topics/fields-and-matter/#starter-path)