NEXT Searching for the ββ0ν decay with a HPGXe TPC Pau Novella (CIEMAT) On behalf of the NEXT Collaboration TAUP09, Rome. Pau Novella [CIEMAT]. 1
Overview ● The NEXT experiment ● The SOFT TPC Concept ● Energy and tracking functions ● Physics Case ● Status of the NEXT project ● Summary TAUP09, Rome. Pau Novella [CIEMAT]. 2
The NEXT experiment Search for the ββ0ν process with a high pressure gas xenon (HPGXe) TPC Measure the ββ2ν decay of 136 Xe T 2ν 1/2 > 10 22 year T 0 ν 1/2 > 1.2 10 24 year NEXT-100: 100 kg 136 Xe @ LSC Degenerate region: <m ν >~ 100 meV Scalability to 1-ton detector Energy Resolution HPGXe F. Feruglio et Al., Nucl. Phys. B 637 (2002) BKG rejection TAUP09, Rome. Pau Novella [CIEMAT]. 3
The NEXT experiment Why a Xenon Gas TPC? High Q ββ : 2480 keV 136 Xe Scintillation/Ionization The Gothard experiment Purification, reusability Phys. Lett. B 434(1998)407 Easy to enrich Long ββ2ν mode Liquid xenon Gas xenon YES Scalability YES YES Compactness NO Gas Xe TPC 3.3 kg 136 Xe Cryogenics Complexity H.P. 5 bars YES Fully Active YES NO Topology YES 6.6% FWHM @ Q ββ YES E. resolution YES 95.6% rejection of single e TAUP09, Rome. Pau Novella [CIEMAT]. 4
The SOFT Concept Separated-Optimized Function for Tracking: a TPC with separately optimized technical solutions for energy and tracking Energy function Cathode: E measurement T0 measurement (scin.) Optimized for E resolution and T0 efficiency Tracking function Anode: tracking Totally active detector Optimized for fine Two different readout planes pixelization Inner walls with reflective material How do we implement such energy and tracking functions in the NEXT TPC? TAUP09, Rome. Pau Novella [CIEMAT]. 5
The SOFT Concept Energy measurement Energy resolution: a must for ββ0ν experiments 136 Xe Intrinsic energy resolution: δ E/E ~ 3·10 -3 FWHM @ Q ββ Ionization only Lxe T=-110ºC Intrinsic resolution worsens Lxe due to technical factors... T=-30ºC HPGXe NEXT target: 1% FWHM @ Q ββ Bolotnikov et Al. Nucl. Ins. Meth A 396 (1997) TAUP09, Rome. Pau Novella [CIEMAT]. 6
Readout technology for the energy function Electroluminiscence Xe Secondary EL amplification is lineal scintillation Small fluctuations (no gain) Better resolution than Q amplification NEXT PMT: Hamamatsu R8520-06SEL (modified version of the XENON PMT) Fit Width Pressure up to 10 bars TAUP09, Rome. Pau Novella [CIEMAT]. 7
The SOFT Concept Tracking function A gas TPC provides also event topology information... Tracking : random walk, ionization topology: Width: ~ 1cm Length ~ 30-40 cm ββ signature: twisted track connected to 2 blobs BKG signature: any other topology Single e ββ0ν event visualization TAUP09, Rome. Pau Novella [CIEMAT]. 8
Readout technologies for tracking function Radiopure device Requirements Low cost per unit of sensitive area Small size suitable for tracking Electroluminiscence Charge amplification Alternative: Micromegas SiPM (MPPC) Hybrid TPC: gain-EL Wave length shifter Operation in pure Xe with EL grid APD (LAPD) Gain, dark current TAUP09, Rome. Pau Novella [CIEMAT]. 9
The SOFT Concept The SOFT NEXT TPC Steel vessel Cathode Anode EL grid 5mm gap γ ~20 kV 10 6 γ /e e 1% FWHM @ Q ββ Reflective material SiPM/APD/MM TTX Sparse PMT plane tracking E, t 0 Drift lenght: 140 cm Pitch ~1.5 cm Diameter: 140 cm 108 kg of xenon Pressure: 10 bars TAUP09, Rome. Pau Novella [CIEMAT]. 10
Physics Case Physics Case Main background: 2.6 γ from 208 Tl ββ2ν background is negligible for 1% FWHM @ Qbb 214 Bi, 208 Tl: mimic the ββ signal if a second e is generated γ interact with Xe via Photoelectric and Compton Neither double Compton nor pair are bkg in our ROI NEXT will measure the backgrounds with depleted xenon TAUP09, Rome. Pau Novella [CIEMAT]. 11
Physics Case Background rejection handles Fully active detector: 208 Tl and 214 Bi decays in vessel/RO External backgrounds can be rejected defining a fiducial volume tracks fully contained may become a bkg Event topology: Events with more than one track Tracks with only one blob TAUP09, Rome. Pau Novella [CIEMAT]. 12
Physics Case Background rejection power Expected number of bkg events (Bi,Tl) Event Selection cuts: contained in fiducial volume only one track F.Iguaz, University of Zaragoza ββ topology Rejection factors (1% FWHM): 214 Bi in vessel: 3.5·10 -7 214 Bi in RO plane: 3.7·10 -7 208 Tl in vessel: 3.5·10 -6 208 Tl in RO plane: 4·10 -6 Gothard experiment: ββ topology lead to 1/30 rejection factor. TAUP09, Rome. Pau Novella [CIEMAT]. 13
Physics Case Sensitivity to the ββ0ν process Just to show the physics potential of the NEXT-100 detector... Most conservative scenario: 1% FWHM @ Qbb Contamination in vessel and readout planes according market QRPA (V.A. Rodin et Al., Nuc. Phys. A766 (2006)) Minimum set of cuts on topology For 500 kg·year: T 0 ν 1/2 = 1.8·10 26 year @ 90% C.L. Background: <10 -3 count/keV/kg/year To be improved: more radiopure materials for vessel and readout <m ν > <100 meV fully exploiting topological signature Improving energy resolution TAUP09, Rome. Pau Novella [CIEMAT]. 14
The NEXT project The NEXT Collaboration: Spokesperson: J.J. Gómez Cadenas (gomez@mail.cern.ch) CEA, IRFU, Saclay, France New collaborators welcome! LBNL, USA Institutional Support: U. Coimbra, Approved by the Scientific Portugal Committee of the LSC Partially funded by MICINN Spain: IFAE, CIEMAT, U. Santiago, IFIC, ITACA, UPV, U. Zaragoza TAUP09, Rome. Pau Novella [CIEMAT]. 15
The NEXT project NEXT @ Canfranc Underground Laboratory LOI submitted to the Scientific Committee. NEXT project is approved. Milestones: NEXT-1 (2009-2011): Demonstrate the technology NEXT-10 (2011-2013): Radiopure 1/10 scale detector @ LSC NEXT-100 (2013-2018): 100 kg 136 Xe detector @ LSC TAUP09, Rome. Pau Novella [CIEMAT]. 16
Summary NEXT project is meant to search for the ββ0ν decay with a HPGXe TPC The TPC is defined according to the SOFT concept: good energy resolution and track reconstruction NEXT-100 will explore the degenerate region of neutrino masses. Very promising physics potential A LOI has been submitted and NEXT has been approved by the LSC This is a first step towards a 1-ton detector, but NEXT Collaboration needs to grow up with new members from all over the world! TAUP09, Rome. Pau Novella [CIEMAT]. 17
Thank you for your attention! TAUP09, Rome. Pau Novella [CIEMAT]. 18
Recommend
More recommend
