An event generator for supernova neutrinos in argon Steven Gardiner - - PowerPoint PPT Presentation

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An event generator for supernova neutrinos in argon

Steven Gardiner Emilija Pantjc Robert Svoboda

University of California, Davis

Christopher Grant

Boston University

Weak Interactjons and Neutrinos

21 June 2017

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Outline

• Motjvatjon for argon-based supernova neutrino detectors
• Event reconstructjon challenges (why is this hard?)
• MARLEY: Model of Argon Reactjon Low Energy Yields

– Ingredients in our model – Example simulatjon results

• Current studies and future prospects

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Water- and argon-based neutrino detectors have complementary sensitjvitjes to SN neutrinos

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Supernova neutrino detectjon with water Cherenkov detectors

• Inverse beta decay is the

dominant reactjon

• Number of detected

photons gives a positron energy measurement

• From there, reconstructjng

the antjneutrino energy is straightgorward

inverse beta decay

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The need for a supernova neutrino simulatjon tool

• Simulatjons are needed to understand LArTPC

response to SN neutrinos

• A number of neutrino event generators exist, but

the emphasis is on high-energy physics

• In the low tens-of-MeV regime, nuclear structure

details become quite important!

• We have developed a new generator to help us

understand the response of 40Ar to SN neutrinos

– Nuclear data measurements (levels, gammas,

matrix elements) can help us

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Bob Marley illustration by Zero Anixter

Model of Argon Reactjon Low Energy Yields

• Event generator for

supernova neutrinos on

40Ar

• Current version does CC

(dominant channel)

• Framework allows adding

new reactjons, target nuclei, etc.

• In use by DUNE for SN

simulatjons

• Also has users from several
• ther liquid argon

experiments

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MARLEY event generatjon fmowchart

Transmission coeffjcient model

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World’s B(GT) data for 40Ar

• Measurements using (p,n)

scatuering vs. 40Ti beta decay show signifjcant disagreements

• Hard to calculate and hard to

measure!

• Karakoç, et al. Phys. Rev. C 89,

064313 (2014) refers to a third measurement that remains unpublished

• Must be supplemented by

theory at higher energies

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MARLEY’s cross sectjon agrees with similar calculatjons

• ver much of the relevant energy range
• Low energies = forbidden transitjons make a small contributjon below

MARLEY’s hard cutof

• High energies = forbidden transitjons start to dominate near 100 MeV

n e u t r i n

• e

n e r g y ( M e V ) 2 4 6 8 1 )

2

c r

• s

s s e c t i

• n

( c m

4 4 −

1

4 3 −

1

4 2 −

1

4 1 −

1

4 −

1

3 9 −

1

3 8 −

1

• +

e

*

K

4

→ A r

4

+

e

ν T

• t

a l c r

• s

s s e c t i

• n

f

• r

M A R L E Y

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MARLEY transmission coeffjcient model

• Unbound states in MARLEY de-excite according to the Hauser-Feshbach

model

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• W. Hauser and H. Feshbach, Physical Review 87, 366 (1952)

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Successfully used for many years to describe nuclear cross sectjons

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Work contjnues to refjne the input parameters (e.g., RIPL-3)

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Used in many SN neutrino theory papers (in combinatjon with RPA, QRPA, etc.)

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Two key assumptjons: 1. compound nucleus 2. reciprocity theorem (tjme-reversal invariance)

• Final states are sampled using decay widths

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• Nuclear potentjal from Koning & Delaroche global optjcal model
• A. J. Koning and J. P. Delaroche, Nuclear Physics A 713 3-4 (2003)
• Solve radial Schrödinger equatjon numerically in matching region
• Match to asymptotjc solutjon, extract transmission coeffjcient

MARLEY transmission coeffjcient model

Transmission coeffjcient represents the probability of penetratjng the nuclear surface

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1 2 3 4 5 6 5 1 1 5 2 2 5 3

L i v e r m

• r

e s u p e r n

• v

a s p e c t r u m

83.7% 14.6% 1.5%

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Current studies and future prospects

Model of Argon Reactjon Low Energy Yields

• MARLEY development is ongoing

– Interfaces to other codes (e.g., LArSofu) – Physics improvements – Preparatjon of data for other reactjon channels

• A variety of reconstructjon topics are beginning to

be addressed using MARLEY events

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De-excitatjon vs. bremsstrahlung γ

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Nucleon emission tagging

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Event t0 determinatjon

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SN triggering

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MC-based smearing matrix for SNOwGLoBES

• ACED: Argon Capture Experiment at DANCE

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Measurement of 40Ar thermal neutron capture cross sectjon and event-by-event gammas

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Addresses key uncertaintjes in liquid argon response to low energy neutrons

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First data this fall

The Detector for Advanced Neutron Capture Experiments at Los Alamos

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Conclusion

Model of Argon Reactjon Low Energy Yields

• Nuclear efects greatly complicate supernova

neutrino event reconstructjon in argon

• MARLEY is a new generator specifjcally

targetjng supernova neutrinos in 40Ar

• Studies are underway to learn how to

reconstruct these events in DUNE

• A direct measurement of these cross sectjons

would be very valuable!

– See C. McGrew’s CAPTAIN talk for one

proposed experiment

• Want to become a MARLEY user or developer?

Email me at support@marleygen.org for more informatjon