1 / 16

A new Approach to  -Decay

COBRA. A new Approach to  -Decay. UK HEP Forum, Abingdon, May 11 th , 2003 Daniel Muenstermann University of Dortmund www.COBRA.physik.uni-dortmund.de. What is COBRA about?. COBRA aims to study -decays of Cd, Zn and Te isotopes. deals with and evolves low-level physics.

howie
Télécharger la présentation

A new Approach to  -Decay

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COBRA A new Approach to -Decay UK HEP Forum, Abingdon, May 11th, 2003 Daniel Muenstermann University of Dortmund www.COBRA.physik.uni-dortmund.de

  2. What is COBRA about? COBRA • aims to study -decays of Cd, Zn and Te isotopes. • deals with and evolves low-level physics. • is currently based in • the UK (Univ. of Oxford, K. Zuber, spokesperson) • Germany (Univ. of Dortmund) • Italy (LNGS)

  3. It might help to disclose other modifications of weak processes like right-handed weak currents • It can reveal the rest-mass of the electron neutrino on an absolute scale. n p n p e e n p n p Leptoquarks, Rp violating SUSY L=2 , Eff. Majorana masses Why is (0)-decay an opportunity? • It can determine the nature of the neutrino (Majorana vs. Dirac particle).

  4. <> Heidelberg- Moscow evidence <m>(eV) ++-ellipsoid More on ++ decays There are 3 possible modes: ++: (A,Z)  (A,Z-2) + 2 e+ (+2e) (Q - 4 mec2) +/EC: e- + (A,Z)  (A,Z-2) + e+ (+2e ) (Q - 2 mec2) EC/EC: 2 e- + (A,Z)  (A,Z-2) (+2e) (Q) EC/EC is preferred by phase space! ++ decays are dominated by right-handed weak currents !

  5. potential for a background-free experiment where mass limits grow linear in measurement time! Why is CdZnTe a favourable material? It contains 9 -isotopes, among them 116Cd: Q-Value at 2.8 MeV, above all naturally occuring -lines 130Te: has large natural abundance (34 %) sits in „compton gap“ of 208Tl direct comparison to geochemical experiments 106Cd: ++-decay at 2.7 MeV possible, but +/EC or EC/EC decays preferred by phase space

  6. Why are CdZnTe semiconductor detectorsadvantagous devices? • good energy resolution (compared to scintillators) • high density compared to gaseous ionisation detectors, large source masses • no cooling needed with CdZnTe • industrially available, commercial development in progress • in our case: source = detector • particle tracking is possible with pixel-devices (solid-state-TPC) • operation in cryogenic mode possible

  7. Reality strikes back: Current Limitations of CdZnTe • Crystal growth: large quantities: 1 cm3 cubes selected detectors: 16 cm3 cubes Therefore: Instead of few large crystals (Heidelberg-Moscow = 1-3 kg) build an array of small detectors • Large hole trapping: Use selective electron readout

  8. COBRA Idea: Build an array of CdZnTe detectors. Characteristics of COBRA: • minimal use of construction material close to the detectors necessary as • no cooling is needed • source = detector • 9 -isotopes measured simultaneously

  9. Early Achievements of COBRA • First „ad-hoc“ efforts with commercial 0.5 cm3 detector and MCA-based readout: • Veto and shield are working • 2 publications with new and improved limits: Muenstermann and Zuber: „An alternative Search for the Electron Capture of 123Te“, J. Phys. G: Nucl. Part. Phys. 29 (2003) B1-B4 Kiel, Muenstermann and Zuber: „A Search for various Double Beta Decay Modes of Cd, Te and Zn Isotopes“, nucl-ex/0301007, to be published in Nucl. Phys. A

  10. Early Achievements of COBRA Calibration spectrum with 228Th:

  11. Low energy part of the spectrum: Spectrum with and without shield: Early Achievements of COBRA • Background at 2.8 MeV: ~ 5 ·10-4 events/(keV g d) • 208Tl-peak at 2.6 MeV visible. Contamination in detector or surroundings?  Build own low-level mounting

  12. The Status of COBRA There is a 2 x 2 array of 1 cm3 detectors with • custom-built preamplifier electronics • (still) CAMAC-based event-by-event readout • passive copper and lead shielding • a plastic-scintillator based cosmic muon veto

  13. Time schedule • Next week: relocation of the setup into the Gran Sasso laboratory • Autumn 2003: First results due, decision about funding of 4 x 4 prototype due • Spring 2004: scalable 4 x 4 prototype and scalable readout electronics operational • Winter 2004: proposal for a competitive 0-decay based on CdZnTe

  14. ad hoc: COBRA compared to‘An Ideal Experiment‘ by Steve Elliot • large mass: CdZnTe detectors are available with m < 100 g  Array of detectors • good source radiopurity: Work in progress, no serious cosmogenic background • demonstrated technology: Again, work in progress • natural isotopes: Yes • source = detector: Yes • energy resolution (< 3 %): Yes • ease of operation: Yes, but ask us in autumn... • large Q value: Yes • event reconstruction: With pixel detectors (3D)

  15. Summary and Outlook COBRA • uses commercially available CdZnTe detectors to measure 9  isotopes simultaneously • has already improved 6  limits with comparably little effort • will move from the surface to the Gran Sasso underground lab for improved low-level measurements next week • is up to now a rather small collaboration, so...

  16. Last Words Join the party! Collaborators most welcome!

More Related