Kinematic searches. Relativity. Uncertainty. Best candidate: Using molecular tritium, daughter will be Kai Zuber 25

Transcription

1 Kinematic searches Relativity Uncertainty Best candidate: Using molecular tritium, daughter will be Kai Zuber 25

2 Tritium beta decay Half-life :12.3 years Matrix element: 5.55 Endpoint energy: about kev Kai Zuber 26

3 Kurie plot Kai Zuber 27

4 First measurements How to measure? Kai Zuber 28

5 Electrostatic spectrometer Kai Zuber 29

6 More experiments 1972 Bergkvist m<55 ev 1980 Lubimov m= 35 ev!!! Livermore, Los Alamos, Zurich, x Troitzk, Mainz m <2.35 ev Before about 1995: Always negative m 2 far away from zero, some systematic effects were not understood Kai Zuber 30

7 Tritium beta decay Kai Zuber 31

8 Mainz experiment C. Kraus et al., Eur. Phys. J. C 40 (2005) Kai Zuber 32

9 MAC-E Filter spectrometer (Mainz, Troitzk, KATRIN) Magnetic Adiabatic Collimation combined with an Electrostatic filter L = constant of motion Kai Zuber 33

10 KATRIN The next generation (ultimate spectrometer?): Aimed sensitivity of 0.2 ev Kai Zuber 34

11 KATRIN- The next step

12 Take the long way home...

13 Alternative ways??? Fraction of events in endpoint region E scales with (Q-E) 3, lower endpoints? Q=2.47 kev Use of cryo-bolometers MARE project, stopped due to experimental limitations Kai Zuber 37

14 Alternative ways? Excited state transitions? C.M. Cattadori et al., NPA 748 (2005) Combined with Penning trap measurement : Endpoint of 155 ± 24 ev Endpoint of 350 ± 150 ev B.J. Mount et al., PRL 103 (2009) J.S.E. Wieslander et al., PRL 103 (2009) Kai Zuber 38

15 Project 8 B. Monreal, J. Formaggio, PRD 80 (2009) Cyclotron frequency of relativistic particles Emission of microwaves to be detected by antenna array Kai Zuber 39

16 Electron capture (EC) and neutrino mass Measures the neutrino mass (not anti-neutrino mass like beta decay) Radiative EC, internal bremsstrahlung - De-excitation spectrum depends on neutrino mass - Calorimetric measurement Kai Zuber 40

17 The case of Ho-163 Endpoint of internal bremsstrahlungs spectrum Current bound : m < 225 ev P.F. Springer et al., Phys. Rev. A 35 (1987) Kai Zuber 41

18 EC signal Very low Q-value allows only M-capture and higher shells Again, precision mass measurement is neccesssary Kai Zuber 42

19 Ho-163 measurement Use cryodetectors Kai Zuber 43

20 Holmes and ECHO ECHO HOLMES HOLMES ECHO Kai Zuber 44

21 Kinks in beta decay Kai Zuber 45

22 The famous 17 kev neutrino (around 1990) Tritium Sulphur-35 Finally ruled out (almost as much positive than negative observations) Kai Zuber 46

23 Double beta decay (A,Z) (A,Z+2) +2 e - + 2ν e (A,Z) (A,Z+2) + 2 e - - 2νββ 0νββ 2 requirements: - Neutrinos are Majorana particles - Neutrinos must have a non-vanishing rest mass (helicity) The smaller the neutrino mass the longer the half-life

24 Requirements - I 1.) m(a,z) > m(a,z+2) 2.) Single beta decay must be forbidden (m (A,Z) < m (A,Z+1)) or at least strongly suppressed (large change in angular momentum)

25 Example: Ge-76 There are only 35 isotopes in nature for double electron emission Kai Zuber 49

26 Signal information (A,Z) (A,Z+2) e - - Signal: One new isotope (ionised), two electrons (fixed total energy) - Single electron energies - Angle between electrons - Sum energy of both electrons - Daughter ion (A,Z+2) - Gamma rays (eg. four 511 kev photons in β + β + or excited state transitions)

27 2νββ All even-even ground state transitions are (A,Z) (A,Z+2) +2 e - + 2ν e Fermi s Golden rule: Single electron spectrum dλ = 2πδ(E 0 E f ) f m,β < f H β m >< m H β i > E i E m p ν E e 2 Angular distribution with β = p/e Sum energy spectrum: dn de E(Q E)5 (1+ 2E + 4E E E 4 30 ) Kai Zuber 51

28 0νββ Any L=2 process can contribute to 0νββ R p violating SUSY V+A interactions Extra dimensions (KK- states) Leptoquarks Double charged Higgs bosons Compositeness Heavy Majorana neutrino exchange Light Majorana neutrino exchange... Nice interplay with LHC 1 / T 1/2 = PS * NME 2 *ε 2

29 Light Majorana neutrinos 2 m ν = U ei m ν i = c 12 i ε m ν = 2 U ei m ν i i 2 c 13 2 m 1 + s 12 2 c 13 2 e iα 1 m + s e iα 2 m 3 1 / T 1/2 = PS * NME 2 * (<m ν > / m e ) 2 Schechter and Valle 1982: Independent of mechanism for neutrinoless DBD Majorana neutrino mass will appear in higher order! Actual calculation: M. Duerr, M. Lindner, A. Merle, JHEP 1106,091 (2011)

30 Spectral shapes 0νββ: Peak at Q-value of nuclear transition Measured quantity: Half-life Dependencies (BG limited) T 1/2 a ε (M t/δe B) 1/2 link to neutrino mass 1 / T 1/2 = PS * ME 2 * (m ν / m e ) 2 Sum energy spectrum of both electrons

31 Perfect world experiment No background δ function as peak 100 % abundance 100% detection efficiency Infinite measuring time Infinite mass T 1 1/ 2 aε Mt ΔEB Life is easy, the rest is just details Kai Zuber 55

32 Back of an envelope This is the 50 mev option, just add 0 s to moles and kgs if you want smaller neutrino masses Τ 1/2 = ln2 a N A M t / N ββ (τ>>t) ( Background free) For half-life measurements of yrs 1 event/yr you need source atoms This is about 1000 moles of isotope, implying about 100 kg Now you only can loose: nat. abundance, efficiency, background,...

33 Experimental approaches There is no super-isotope! 11 isotopes of interest Isotope AME 2003 Q- values 2012 Ca ± ± 0.84 Ge ± ± Se ± ± 0.3 Zr ± ± 2.2 Mo ± ± 0.17 Pd ± ± 0.64 Cd ± ± 0.13 Sn ± ± 0.39 Te ± ± Xe ± ± 0.37 Nd ± ± 0.20 Candles GERDA, Majorana SuperNEMO, LUCIFER MOON, AMore COBRA Tin.Tin CUORE, SNO+ EXO, KamLAND-Zen, NEXT, XMASS MCT

34 Mass hierarchies and DBD 76 Ge T 1/2 = 1.19 x yr 1 Claim of evidence yrs yrs yrs H.V. Klapdor-Kleingrothaus et al. Phys. Lett. B 586, 198 (2004) yrs 3 normal inverted 1.) Is the claimed evidence correct? GERDA phase I 2.) Can we probe the inverted hierarchy? 3.) What about the normal hierarchy?

35 Heidelberg Moscow Experiment Isotope of interest: 76Ge Still only 1 decay per year per 10 kg Ge Background obtained 0.1 count/kev/kg/yr

36 Ge-spectrum 0ν peak region Kai Zuber 60

37 Evidence? H.V. Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198 (2004) Mod.Phys.Lett.A21: (2006) Very controversial discussion in the community H.V. Klapdor-Kleingrothaus et al., Eur.Phys.J. A12 (2001)

38 KamLAND - Zen Using 400 kg of Xe (91.7% enriched in Xe-136) T 1/2 > 1.9 x years (90%CL) A. Gando, PRL 111, (2013) Data taking after purification started Dec. 2013, 110m Ag down by more than an order of magnitude K. Zuber