Supernova Triggering Part I: Needs and Questions Amanda Weinstein - - PowerPoint PPT Presentation

Supernova Triggering Part I: Needs and Questions

Amanda Weinstein Iowa State University

Hierarchy of Needs

• Most critical to least critical

(which does not imply items at top not important)

• Ideally, automatically enable

items at top when designing for the items on the bottom.

• We need a similar pyramid

for DAQ requirements

10/9/2017 Amanda Weinstein DUNE DAQ

Self-trigger a SNB at d < 15 kpc and record physics data Caveat: This is my approximation and should not be taken as “blessed” by the SNB group Self-trigger a SNB at d > 15 kpc Externally trigger (e.g. SNEWS) a SNB at d < 15 kpc and record physics data Externally trigger (e.g. SNEWS) a SNB at d < 15 kpc and record physics data

Supernova Flowchart

End-of-life mass > 1.4 M◉? (Birth mass > 8 M◉) No Yes White dwarf Yes Possible thermo- nuclear supernova Black hole CC SNe, neutron star

Explosion succeeds ? Binary companion ?

End-of-life mass > 1.4 M◉? (Birth mass > 8 M◉)

Core mass > 3 M◉?

We want these

What physics do we want to capture?

Potentially detect Si- burning phase before explosion in neutrinos Potentially useful information at later times (up to ~30s)

Intertwined info about shock development and neutrino physics

Spectral Features

• Different oscillation physics in

neutrino’s journey from proto- neutron star to us

• MSW effects (r > 200 km)
• “Collective oscillations:” (r < 200

km)

• Vacuum oscillations (once away

from star)

• Flavor-specific burst evolution

carries information about mass

• rdering and SN processes
• Key requirements:
• Energy resolution <10% (in our

control)

• Energy threshold ~ 5 MeV (mostly

in our control)

• Statistics (only partly in our

control)

Dasgupta, Dighe, Raffelt and Smirnov

• Well-determined light curves
• Time-integrated and time-

resolved energy spectra

What physics do we want to capture?

• We want self-triggering and whatever

pointing we can get (alerts to other experiments)

• Recall that in early period EM radiation does

not escape, but neutrinos do

• Neutrinos crucial with weak or dust-
• bscured SNe
• “Failed” SNe: have a distinct neutrino

signature (e.g. continuously hardening spectrum, abrupt cutoff)

• Pointing information: allows optical, infrared

telescopes to be ready and on target

• Elastic scattering events are best for this but

we don’t get many

Factors controlling statistics

10/9/2017 Amanda Weinstein DUNE DAQ

Distance (inverse square law)

• Energy resolution degradation
• Detector inefficiencies
• Not having prompt light (worse t0)
• Other losses (e.g. neutrons)

Failure to trigger/record events near threshold(can ameliorate by dumping raw data in long window) Does the 90% number include both

• f these?

SNB Trigger

• What can this mean?
• External burst trigger :a vetted alert we send to other experiments
• Internal burst trigger: triggering on the supernova as a whole, i.e on a multi-event

signature that occurs over a period of time

• Pros:
• could be as simple as looking for characteristic rate changes
• Increases robustness against “wiggles” of radiological and other backgrounds
• Cons/challenges: potential for severe model-dependence
• Triggering at the event level, i.e. reacting to the present a cluster of “SN-like”

interactions

• This raises questions like: what exactly do we mean by an “SN-like” event?
• These two things are not mutually exclusive—the second is essential to

accomplishing the first.

• Question: how do DAQ operations change, locally and globally, if an SN trigger is

received?

10/9/2017 Amanda Weinstein DUNE DAQ

Background :Key Numbers

10/9/2017 Amanda Weinstein DUNE DAQ

• Prototype radiological

background: Ar 39

• 1 Bq/kg, so 107 Hz per 10 kt

detector

• ~2000 hits per drift window from

all Ar 39 in 1x2x6 vs. ~30 from actual neutrino

• Individual Ar 39 events low

energy and produce isolated hits

• # channels needed for rejection

(variable) (K. Warburton)

• Full disambiguation: 2 to 3
• Raw ADC threshold (2-6,

threshold dependent)

• Individual Ar 39
• Note: Ar 39 rejection requires

some level of time information

• Time resolution better than

100 ticks (between 20/30 -100 depending on binning)

• Note: other less-studied

backgrounds may be higher energy and tougher to disambiguate.

• Don’t yet have hard numbers
• n these.

Burst over time

• Early time structure of SN neutrino flux sensitive to mass hierarchy.

Good news for physics, bad news for triggering

10/9/2017 Amanda Weinstein DUNE DAQ

Timescale problems I

• Neutronization burst spike is clean, and low-latency, but far from guaranteed!
• SNB-like event density over a longer time period could be characteristic. BUT longer latency (in normal

hierarchy, increase in events may not be recognizable for as long as 0.1 seconds) .

• Do we try for a single robust model independent criteria, or just multiple burst triggers based on

different scenarios?

10/9/2017 Amanda Weinstein DUNE DAQ

Timescale problems II: TPC vs PD

• On a completely different note, we have a second timescale

problem in the mix

10/9/2017 Amanda Weinstein DUNE DAQ

• TPC and PD operate on very different

timescales

• PD efficiency s.t. we likely need to

trigger most SN events off TPC

• Question: How do we ensure we get

max # events with PD information and hence good t0s?

Questions in Summary

• What defines a single-event SNB trigger?
• How local is local, in space and time? I.e. how many channels and how large a time

bucket do we need to define a single-event SN trigger without other (e.g. radiological) backgrounds swamping us?

• We’ve made some progress on this with Ar 39 but still fear the unknown unknowns.
• How do we reconcile the timescales of the different systems (TPC vs. PD)?
• What defines a burst-level trigger?
• How big a chunk of the burst do we need to accumulate data from before the burst-

level trigger is robust?

• How do we reduce our model dependence in the burst-level trigger definition?
• What do we tolerate in terms of fake rate internally vs. in terms of alert rate?
• What precisely does DAQ do in response to an SNB trigger? (see part II)
• What is the maximal amount of compression we can tolerate before losing 5 MeV

threshold and/or degrading energy resolution at low energies? (relevant to external triggering)

10/9/2017 Amanda Weinstein DUNE DAQ