The Hunt for neutrinoless double beta decay with the NEXT …next.ific.uv.es/DocDB/0000/000099/001/PANIC2014_Lorca.pdf · 2015-05-25 · The NEXT Concept 9 Control of Background:

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The Hunt for neutrinoless double beta decay with the NEXT experiment

a nextOn behalf of the CollaborationDavid Lorca

Outlook

experiment requirements The NEXT Concept NEXT-DEMO: R&D and Results NEXT-100

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��0⌫

experiment requirements

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Energy Resolution

��0⌫

(T 0⌫1/2)

�1 = G0⌫(Q,Z) |M0⌫ |2 m2��

Expected Decay Rate Experimental Sensitivity

Main Experimental Requirements

Control of Backgrounds Scalability (Mass vs Cost)

T1/2 / a · ✏ ·r

M · t�E ·B

4

0 0.2 0.4 0.6 0.8 1.0

(E1+E2)/Q

2νββ

0νββ

experiment requirements��0⌫

selection of the appropriate technology to resolve events from the continuous mode and radioactive backgrounds

Energy Resolution

��0⌫��2⌫

Neutrinoless double beta decay spectrum

T1/2 / a · ✏ ·r

M · t�E ·B

Energy (MeV)2.1 2.15 2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 2.6

Even

ts /

5 Ke

V

0

2

4

6

8

10

12

14

16

18

100 meV, exposure = 500 kg year

bb0nu

Tl208

Bi214

Total background

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experiment requirements��0⌫

Main background is natural radioactivity of detector

components and surroundings

Control of Backgrounds (combined with ER)

T1/2 / a · ✏ ·r

M · t�E ·B

��0⌫

6

experiment requirements��0⌫

New results have pushed down the upper limit, creating the necessity to increase the detector mass up to the ton scale (for now)

Scalability (Mass vs Cost)

hundreds kg1 ton

10 ton

m��

T1/2 / a · ✏ ·r

M · t�E ·B

The NEXT Concept

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NEXT, a high pressure gaseous Xenon TPC with EL amplification

The NEXT Concept

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NEXT, a high pressure gaseous Xenon TPC with EL amplification

Energy Resolution : HPXe TPC combined with EL amplification provides excellent

energy resolution

EnergyResolution%

Density, g/cm3

E� = 662 keV

LXe, T = �30oC

LXe, T = �110oC

HPXe : FanoFactor = 0.15± 0.02

�E < 1 % FWHM at 2458 keV (Q��)

The NEXT Concept

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Control of Background: HPXe provides topological reconstruction of the events

X (mm)-60 -40 -20 0 20 40 60

Y (m

m)

-60

-40

-20

0

20

40

60

X (mm)40 60 80 100 120 140 160

Y (m

m)

-100

-80

-60

-40

-20

0

20

✔

✔✔

✘

SIGNAL BACKGROUND

• Signal: a twisted track, 10 cm long, with two energy blobs at the end.

!• Background: single electrons, 85% of the time accompanied by an X-ray.

NEXT, a high pressure gaseous Xenon TPC with EL amplification

The NEXT Concept

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Scalability (Mass vs Cost)

Xenon is the cheapest and easiest to enrich of all isotopes.

• Source: increases by a factor 8

• Background: increases by a factor 4

��

L

r Doubling r&L S/N x2

NEXT, a high pressure gaseous Xenon TPC with EL amplification

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Detection Process

• Charged particles propagate through Xenon ionizing and exciting its atoms.

• Calorimetry provided by a plane of PMTs located behind a transparent cathode (energy

plane), with t0.

• Event topology reconstructed by a plane of SiPMs (tracking

plane).

EL amplification provides lineal gain, exploiting the excellent

Fano factor in gas

NEXT-DEMO at IFIC

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Gas systemDAQ HV modules

SiPM electronics

PMT electronics

Pressure vessel

Pressure Vessel and Detection Planes

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HHV Anode SiPMs

Cathode PMTs

Ports for Calibration Sources

Energy Plane

Tracking Plane

Field Cage and Light Tube

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CATHODE

ANODEGATE

DRIFT REGION (300 mm)

EL REGION (5 mm)

SHIELDBUFFER REGION (100 mm)

TPB Coated

Internal View

NEXT-DEMO Field Cage

Signals in NEXT-DEMO

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Primary Scintillation (S1) t0 of event

Electroluminescense (S2)

Drift Time: Z axis (~1mm/us)

NEXT-DEMO NEW Results

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X-ray energy deposition (~30 keV) used for calibration Distributed all over the volume

Point-like events, Range ~0.6 mm (10 bar)

mm-80 -60 -40 -20 0 20 40 60 80

mm

-80

-60

-40

-20

0

20

40

60

80

0

10

20

30

40

50

60

70

X-ray 2D distributionX-ray production

Entries 29741 / ndf 2χ 48.37 / 36

Prob 0.08157

Constant 0.001± 6.441 Slope 3.96e-06± -3.54e-05

s)µDrift Time (140 160 180 200 220 240 260 280 300

Cha

rge

(pho

toel

ectro

ns)

610

615

620

625

630

635 Entries 29741 / ndf 2χ 48.37 / 36

Prob 0.08157

Constant 0.001± 6.441 Slope 3.96e-06± -3.54e-05

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NEXT-DEMO NEW Results

X (mm)-50 -40 -30 -20 -10 0 10 20 30 40 50

Y (m

m)

-50

-40

-30

-20

-10

0

10

20

30

40

50

0.90

0.95

1.00

1.05

1.10

1.15

Two dimensional normalized response to X-ray depositions

X-rays allow: Spatial calibration of the light tube.

Electrons attachment correction. Temporal fluctuations correction in

the EL generation.

e� lifetime ⇠ 28ms

X-ray

Compton

Escape

Photoelectric

Corrected Na-22 spectrum

NEXT-DEMO NEW Results

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• 1.62 % FWHM energy resolution for 511 keV and

5.69% for 30 keV over a fiducial volume of 60x60x300 mm

!

•Extrapolate to 0.73% and 0.62% FHHM to the Qbb value

NEXT Coll: arXiv:1407.3966

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Drift Field (V/cm)150 200 250 300 350 400 450 500 550 600

s)µ

Drif

t Vel

ocity

(mm

/

0.5

0.6

0.7

0.8

0.9

1

1.1

MagboltzData

Drift Velocity as a function of drift field

Drift Field (V/cm)150 200 250 300 350 400 450 500 550 600

/s)

2 (c

mLD

30

40

50

60

70

80

90

100

110

120

MagboltzData

Longitudinal diffusion coefficient vs drift field

Point-like depositions allow the measurement of high pressure xenon properties such a drift

velocities and longitudinal diffusion

NEXT-DEMO NEW Results

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3D reconstruction of electronCs-137

muon

• Tracking reconstruction of events • Higher energy deposition at electron

track end-point

NEXT Coll: arXiv:1306.0471

NEXT-DEMO Results

NEXT-100

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NEXT-100 Pressure Vessel Detector Overall Cross Section

Main Cylindrical VesselTorispheric Heads

Energy Plane, PMTsCu Shield

PMT FTs

Vac. Manifold

HV/Press. relief/Flow/Vac. PortsHV Cable Cu Shield Bars

F.C. InsulatorField Cage Rings

Reflectors

Shielding, External, Cu on Pb

EL mesh planes

EL HV F.T.Cathode Tracking Plane, SiPM

Cu Shield

D. Shuman (LBNL) NEXT-100 Pressure Vessel, Nov. 1, 2011 November 2, 2011 13 / 20

~7200 SiPMs

60 PMTs

HPXe TPC containing 100 kg of Xenon at 15 bar

Tracking Plane

Energy Plane

Technical Design Report (TDR)NEXT Coll: arXiv:1202.0721 NEXT Coll: arXiv:1211.3961

Radiopurity Control

NEXT-100

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Rejection

Total Background

Tl-208 Bi-214Fiducial E>2MeV 67.86% 0.25% 0.01%

ROI 95.52% 8.99% 64.66%

1 track 74.60% 1.86% 12.54%

2 blobs 73.76% 9.60% 9.89%

��0⌫

⇠ 10�7

5 · 10�4 ckky

m�� ⇠ 100meV0 200 400 600 800 1000

0

100

200

300

400IBM-2QRPAISM

mββ

(meV

)

exposure (kg yr)

NEXT-100

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Status: Seismic platform, lead castle, gas system, emergency recovery system and vessel completed.

•2015: underground operations start with non-enriched Xenon •2016-2020: physics with enriched Xenon (100 kg in stock)

Castle and seismic structure Video

NEXT-100 VesselPlatform for NEXT-100 at LSC

Schedule:

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SUMMARY

The NEXT concept satisfies the main requirements of a neutrinoless double beta decay experiment.

NEXT-DEMO has demonstrated the main issues of such technology.

NEXT-100 plans to explore sensitivities below 100 meV of neutrino mass.

Possibility to scale up.

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The NEXT Collaboration

Neutrinoless Experiment with a Xenon TPC

IFIC (Valencia) • U. Santiago de Compostela • U. Politécnica Valencia • U. Zaragoza • U. A. Madrid • U. Girona

LBNL • Texas A&M • Iowa State U. U. Coimbra • U. Aveiro JINR

U. A. Nariño