supernova triggering part i: needs and questions...end-of-life mass > 1.4 m ? (birth mass > 8...

Supernova Triggering Part I: Needs and Questions

Amanda WeinsteinIowa State University

Hierarchy of Needs• Most critical to least critical

(which does not imply itemsat 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-lifemass > 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 ordering 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-obscured 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


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 of 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?


Background :Key Numbers


• 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-studiedbackgrounds may be higherenergy and tougher to disambiguate.- Don’t yet have hard numbers

on these.

Burst over time

• Early time structure of SN neutrino flux sensitive to mass hierarchy. Good news for physics, bad news for triggering


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?


Timescale problems II: TPC vs PD• On a completely different note, we have a second timescale

problem in the mix


• TPC and PD operate on very different timescales

• PD efficiency s.t. we likely need totrigger 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)


supernova triggering part i: needs and questions...end-of-life mass > 1.4 m ? (birth mass > 8...

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