EIEIOO 2021:

The NEWS-G dark matter experiment

Daniel Durnford

Supervisor: Prof. Marie-Cécile Piro

May 7^th 2021

Daniel Durnford

EIEIOO 2021

A bit about me

BSc at the U of A:

• PICO dark matter experiment
• SNO+
• BetaCage

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MSc at Queen’s:

• NEWS-G dark matter experiment

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PhD at the U of A (Piro group):

• NEWS-G
• Scintillating bubble chamber project

Daniel Durnford

EIEIOO 2021

Low mass dark matter

Absence of canonical WIMPs [1,2] motivates searches for other low mass WIMP-like DM candidates [3,4]

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[1] D. Bauer et al, Phys. Dark Univ., 7–8, 16–23 (2015)

[2] K. Petraki et al, Int. J. Mod. Phys. A, 28(19), 1330028 (2013)

[3] K.M. Zurek, Phys. Rep., 537(3), 91 (2014)

[4] R. Essig et al, Dark Sectors and New, Light, Weakly-Coupled Particles (2013)

Daniel Durnford

EIEIOO 2021

Low mass dark matter

Minuscule energies:

Nuclear recoils of ~ 1 keV

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Daniel Durnford

EIEIOO 2021

Low mass dark matter

Minuscule energies:

Nuclear recoils of ~ 1 keV

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Low energy threshold

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Neon target, different masses

Daniel Durnford

EIEIOO 2021

Low mass dark matter

Minuscule energies:

Nuclear recoils of ~ 1 keV

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Low energy threshold

Low-A target atom

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Neon target, different masses

1 GeV DM, different targets

Daniel Durnford

EIEIOO 2021

The NEWS-G dark matter experiment

Metallic vessel filled with a noble gas mixture, with a single high voltage anode/sensor

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Low-A target atoms increases

sensitivity to low-mass

WIMPs

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Low capacitance (~0.4 pF)

decreases electronic

baseline noise

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Townsend avalanche

provides large gain

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Energy threshold ~ 10 eV !

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Spherical Proportional Counters (SPCs) to search for low-mass dark matter

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Daniel Durnford

EIEIOO 2021

Principle of operation

Daniel Durnford

EIEIOO 2021

Principle of operation

Daniel Durnford

EIEIOO 2021

Principle of operation

Daniel Durnford

EIEIOO 2021

Principle of operation

Daniel Durnford

EIEIOO 2021

Principle of operation

Daniel Durnford

EIEIOO 2021

Event reconstruction

Daniel Durnford

EIEIOO 2021

Event reconstruction

Q. Arnaud et al. (NEWS-G), Astropart. Phys. 97, 54 (2018).

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Daniel Durnford

EIEIOO 2021

NEWS-G first results

The Laboratoire Souterrain de Modane (LSM) is an underground lab in France

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Car access to the lab!

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Daniel Durnford

EIEIOO 2021

NEWS-G first results

Daniel Durnford

EIEIOO 2021

“SNOGLOBE”

Radon trap

P. O’Brien

Stainless steel skin

Next generation detector!

• More radio-pure construction materials
• Multi-layered compact shield system
• Gas filtration and monitoring
• Multi-anode sensor for more isotropic response

Daniel Durnford

EIEIOO 2021

Low energy calibration

Because the WIMP recoil spectrum is roughly exponential, most sensitivity low DM masses comes from single quanta (1e^-) events. Therefore we need to accurately characterize our energy response at this regime.

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Daniel Durnford

EIEIOO 2021

UV laser calibration

Daniel Durnford

EIEIOO 2021

UV laser calibration

Q. Arnaud et al. (NEWS-G), Phys. Rev. D 99, 102003 (2019)

Daniel Durnford

EIEIOO 2021

³⁷Ar calibration

2.8 keV

270 eV

Daniel Durnford

EIEIOO 2021

³⁷Ar calibration

In particular, the fit of the 270 eV peak gives good support for our modelling choices

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ the LSM

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ the LSM

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ the LSM

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ the LSM

The 11-anode sensor is read out in two channels (north and south)

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Physical events induce mirror signals on the opposite channel, electronic noise events do not! Possible to use this to discriminate against non-physical events

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ the LSM

The analysis of ~12 days of data with 135 mbar pure CH4 at the LSM is ongoing

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Calibration from a UV laser and 37Ar are the primary tools for understanding the detector response at the level of single ionizations

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Results expected soon, which will be the first DM limit set with hydrogen target atoms!

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ SNOLAB

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ SNOLAB

Daniel Durnford

EIEIOO 2021

SNOGLOBE @ SNOLAB

NEWS-G Collaboration

NEWS-G

December 2020

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Extra slides

Daniel Durnford

EIEIOO 2021

DM signal

The signal we would see from DM is the theoretical DM spectrum (standard halo model) convolved with our detector energy response model

Observed spectrum

DM standard Halo model

Detector energy response model

Pure CH₄

Daniel Durnford

EIEIOO 2021

Energy response model

Deposited E

Primary ionization:

• Statistics modelled with COM-Poisson
• Mean energy required for 1 primary pair is W(E) with high-energy limit W₀ (typically ~ 30 eV) and minimum energy 𝛪 (13.6 eV)
• Mean energy / pair scaled up by quenching factor Q(E) for nuclear recoils
• Dispersion controlled by Fano factor F

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Avalanche (secondary) ionization:

• Statistics modelled with Polya distribution with shape parameter 𝜃
• Mean reconstructed amplitude of 1 primary electron (1000s of avalanche pairs) is ⟨G⟩

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There’s baseline noise on top of the signal, 𝜎_b

The energy response of an SPC can be divided into two main components:

Daniel Durnford

EIEIOO 2021

Avalanche response

The distribution of the number of avalanche pairs “S” is approximately exponential

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It is known to be well-described by the Polya distribution, with shape parameter θ:

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Daniel Durnford

EIEIOO 2021

²¹⁰Pb background

Daniel Durnford

EIEIOO 2021

²¹⁰Pb background

Daniel Durnford

EIEIOO 2021

Quenching factor measurements