The Effect of Cancellation in Neutrinoless Double Beta Decay

Transcription

1 The Effect of Cancellation in Neutrinoless Double Beta Decay Manimala Mitra IPPP, Durham University July 24, 204 SUSY 204, Manchester arxiv:30.628, Manimala Mitra, Silvia Pascoli, Steven Wong Manimala Mitra Cancellation in Neutrinoless Double Beta Decay / 20

2 Outline: Neutrinoless double beta decay-the canonical interpretation The cancellation framework Phenomenological implications Sterile neutrinos R-parity violating supersymmetry Model realization Summary Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 2/ 20

3 Experimental Observation Small non-zero ev neutrino masses m i and mixing U from oscillation and non-oscillation experiments Neutrino oscillation (ν α ν β ) (From solar, atmospheric, reactor, long-baseline experiments) Non-Oscillation Cosmology, β-decay, (ββ) 0ν -decay... Oscillation Experiments Cosmology Information about mass square differences and mixing angles. m ev 2, m ev 2 Large mixing angles θ 2 34, θ Non-zero θ 3 8 (DAYA BAY, RENO) Bound from cosmology Σm i < O(0.) ev. BOSS result Σ i m i 0.35 ev ( arxiv: ) Super Kamiokande, Long Baseline T2K, MINOS, K2K; Reactor DAYA BAY, RENO,...; Solar SNO, Borexino,... Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 3/ 20

4 Contd Light Neutrinos Dirac or Majorana? Neutrino Mass Dirac or Majorana? Dirac mass, m D ν L N R lepton number is conserved Majorana mass, mν T C ν lepton number is violated by two unit Lepton number is a Global U() symmetry of standard model Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 4/ 20

5 Neutrinoless double beta decay The process is (A,Z) (A,Z +2)+2e Probing lepton number violation L and B numbers are accidental symmetries of the standard model Light neutrinos can mediate the process, if Majorana (Racah, 937; Furry 939) Majorana Nature of Light Neutrinos Schechter-Valle, PRD, 82 d L W ν u L e L Experiments at GRAN SASSO, Italy, Japan, Sudan... Existing bound on half-life from GERDA, KamLAND-Zen... Claim of observation of (ββ) 0ν -decay... d L W e L u L Promising forthcoming experiments GERDA Phase-II, Majorana, SuperNEMO Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 5/ 20

6 The light neutrino contribution Ν The half-life T 0ν /2 = G 0ν M ν 2 m ν ee 2 m e Positive claim 90 GERDA 90 G 0ν phase-space ev m ee IH NH GERDA HDM IGEX 90 QD M ν nuclear matrix element m lightest ev Planck KATRIN Planck2 m ν ee = Σm i U 2 ei effective mass of (ββ) 0ν -decay Tension between (ββ) 0ν -decay and cosmology (Fogli et al., 2008; Mitra et al., 202, 203) α, β Majorana phase, m i light neutrino masses m ν ee = m U 2 e +m 2U 2 e2 e2iα +m 3 U 2 e3 e2iβ Unknown neutrino mass spectra, absolute mass scale, CP phases Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 6/ 20

7 Experimental Results Experimental Results for 76 Ge GERDA, T 0ν /2 > yr, 90% C.L GERDA combined (IGEX+Heidelberg-Moscow) T 0ν /2 > yr, 90% C.L GERDA collaboration, 203 Experimental Results for 36 Xe EXO-200, T 0ν /2 > yr at 90% C.L EXO collaboration, 202 KamLAND-Zen, T 0ν /2 > yr at 90% C.L (Neutrino 204) KamLAND-Zen combined, T 0ν /2 > yr at 90% C.L KamLAND-Zen collaboration, 202 Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 7/ 20

8 Contd The half-life for 76 Ge, T/2 0ν = yr, 68% CL. H. V. Klapdor-Kleingrothaus et al., 2004 The half-life for 76 Ge, T/2 0ν = yr, 68% CL. H. V. Klapdor-Kleingrothaus et al., 2006 GERDA combined rules out the positive claim for almost all of the NME calculations. The individual bound is still consistent Dev, Goswami, Mitra and Rodejohann, PRD, 203 Ge (yr) 76 T / GCM IBM (R)QRPA NSM EXO % C.L KamLAND-Zen 90% C.L T /2 Xe (yr) Combined 90% C.L. KK 68% C.L KamLAND-Zen rules out the positive claim for most of the NME calculation How to overcome the mutual conflict between two different sets of experiments? From A. Gando et al., 202 Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 8/ 20

9 Contd Escaping the mutual conflict between two different experiments? Different experiments that use different isotopes Experiment A Measurement of half-life Experiment B Bound on half-life. Result of experiment A is constrained Possible solution Effect of Interference In a realistic model of neutrino mass generation more than one contribution can be present in (ββ) 0ν -decay can interfere Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 9/ 20

10 Contd: Previous and recent studies additional contributions in (ββ) 0ν -decay R parity violating supersymmetry (Mohapatra 986; Hirsch et al, 995; Choi et al, 2002; Allanach et al, ) Left Right symmetry (Hirsch et al., PLB, 96, Tello et al., PRL, 20, Goswami et al., JHEP, 202, Barry et al., JHEP, 203, Vogel et al., PRD, 2003; Patra et al., 202) Quasi-dirac neutrinos (Petcov, Ibarra, 200) Sterile neutrinos ( S. Pascoli et al., 202; M. Blennow et al., 200; M. Mitra, F. Vissani, G. Senjanović, 202; Meroni et al, 202 ) Models with right handed neutrinos at colliders ( Keung, Senjanovic, 83; A. Datta et al., 994; Kersten, Smirnov, 2007; P. S. Bhupal Dev, Franceschini, Mohapatra, 202; Chang-Hun Lee et al., 203; P.S.Bhupal Dev, Apostolos Pilaftsis, Un-ki Yang, 203; S. P. Das et al., 202; Atre et al., 2009; F. Del. Aguila et al., ) Light neutrino and sterile neutrino contribution Light neutrino and squark-gluino contributions in RPV Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 0/ 20

11 Cancellation in (ββ) 0ν -decay Two large contributions in (ββ) 0ν -decay Interference T 0ν /2 = G 0ν ( η 2 M 2 + η 2 2 M cosα η η 2 M M 2 ) η and η 2 are two different contributions. α relative phase Cancellation between two contributions in isotope A. η M,A = η 2 M 2,A Infinite half-life T 0ν /2 (A) Any bound on the half-life of the isotope A can be escaped. The half-life of any other isotope B is larger than no interference T/2 0ν (B) = GB 0ν η2 (M,B M,A M 2,B ) 2 M 2,A Manimala Mitra Cancellation in Neutrinoless Double Beta Decay / 20

12 Contd Cancellation between active and sterile neutrino contributions n h heavy Majorana neutrinos N i mixing V li mass M i. M 2 i > p2 (200) 2 MeV 2 ; p intermediate momentum Half-life T /2 = G 0ν M ν η ν +M N η N 2 η ν = U 2 ei m i/m e, η N = V 2 ei m p/m i Cancellation in isotope A η N = η ν Mν M N Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 2/ 20

13 Contd The half-life in isotope B is larger T/2 0ν (B) = GB m ν 2 ee 0ν m e M 2 ν,b ( M ) ν,a M 2 N,B M N,A M ν,b The redefined effective mass is suppressed m eff ee = m ν ee ( M ν,a M N,B M N,A M ν,b ) Positive claim 90 GERDA 90 GERDA IH GERDA HDM IGEX 90 QD 0. GERDA HDM IGEX 90 GERDA Phase II QD ev Ν m ee 0.0 NH eff m ee ev 0.0 IH T 0Ν 2 6 x0 27 yr 0.00 Planck KATRIN Planck NH Planck KATRIN Planck m lightest ev m lightest ev Larger value of the lightest mass is required The tension with cosmology is even more stringent Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 3/ 20

14 Contd Manimala Mitra Cancellation in Neutrinoless Pascoli, Mitra, Double Wong, Beta 203 Decay 4/ 20 Additional light sterile neutrinos may lead to cancellation between light and heavy sterile neutrinos The light and heavy neutrino contributions η l = (Σ im i Uei 2 +Σ km 4k Ue4 2 k ), η N = m e j m p V 2 en j M Nj Cancellation condition η l M l = η N M N Cancellation between active and sterile neutrino for 36 Xe and implications for 76 Ge Re 3 H 65 Ni 64 Cu Re 3 H 63 Ni 64 Cu U e Ν2Β GERDA S 20 F Ferm i 2 Bugey Borexino Π eν PS9 U e GERDA S 20 F Ferm i 2 Bugey Borexino Π eν PS m 4 GeV m 4 GeV

15 Contd 0.0 NA3 0.0 NA3 VeN L3 PS9 DELPHI K eν CHARM VeN L3 PS9 DELPHI K eν CHARM GERDA M N GeV GERDA M N GeV Atre et al., 2009; Mitra, Vissani, Senjanovic, 202; Mitra, Pascoli, Wong, 203 Bound on mass-mixing plane is less stringent in the presence of cancellation!! Ue4 2 < κ m 4 ( M ν,xe M N,Ge M N,Xe M ν,ge ) Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 5/ 20

16 Contd Similar suppression of the effective mass for RPV scenario Large gluino contribution in (ββ) 0ν -decay R. N. Mohapatra, Phys. ReV. D34, 986 Light neutrino and gluino exchange. Light neutrino and squark exchange Interference in (ββ) 0ν -decay Meroni, Petcov, Simkovic, 202; Simkovic et al., 200; Faessler et al., 20 d c e L d c e L d c ul ũl χ/ g χ/ g ũl ul ul χ/ g χ/ g ũl ul e L χ/ g χ/ g dr e L e L d c e L d c dr ul d c dr ul GERDA 90 GERDA GERDA HDM IGEX GERDA HDM IGEX 90 T 0Ν 2.5x0 26 yr QD T 0Ν 2.5x0 26 yr QD eff m ee ev 0.0 IH T 0Ν 2 6x0 27 yr eff m ee ev 0.0 IH T 0Ν 2 6x0 27 yr 0.00 NH Planck KATRIN Planck NH Planck KATRIN Planck m lightest ev m lightest ev Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 6/ 20

17 Model Realization-Extended Seesaw Models with sterile neutrinos N and S. The mass matrix 0 α T m T D M n = α µ m T S m D m S m R C. S. Kim, S. K. Kang, 2006 Two widely separated LNV scale µ and M R with µ M R Two masses of the sterile neutrinos m N m T S m R m S and m N m R Active-sterile neutrino mixings m D /m S and m D /m R. Negligible contribution from sterile neutrino N in (ββ) 0ν -decay Inverse seesaw with one small lepton number violating scale µ (Mohapatra 986; Mohapatra, Valle, 986; Wyler et al., 983; E. Witten, 986). Quasi-degenerate neutrinos small LNV signatures (Kersten, Smirnov, 2007) Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 7/ 20

18 Contd Cancellation between the active neutrino and the sterile neutrino S in isotope 36 Xe µ = ( )( mr MN,Xe m 2 S M ν,xe ) m e m p m R GeV 5.00 m R GeV 0.00 m N GeV GERDA 90 GERDA HDM IGEX 90 m S 0 4 GeV GERDA 90 GERDA HDM IGEX Μ GeV Μ GeV Bound from KamLAND-Zen is satisfied. GERDA limit is saturated for sterile neutrino mass for m N O(00) MeV Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 8/ 20

19 Summary Effect of interference is important. Should be taken into account The mutual conflict between two different experiments can be resolved A realistic model of neutrino mass generation may lead to additional contributions in neutrinoless double beta decay Interference between two large contributions Cancellation between two different contribution can escape any constraint of half-life However, non-trivial effect in the half-life prediction of other isotopes If (ββ) 0ν -decay is not observed Light neutrinos can be Dirac or cancellation between two contributions Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 9/ 20

20 Thank You Manimala Mitra Cancellation in Neutrinoless Double Beta Decay 20/ 20