DAMA Collaboration (Roma2, Roma, LNGS, IHEP/Beijing) & INR-Kiev http://people.roma2.infn.it/dama Searches for non-paulian transitions in highly radiopure NaI(Tl): previous results and perspectives SpinStat 2008 Trieste, September 22, 2008 F. Nozzoli University & INFN Roma Tor Vergata Roma2,Roma1,LNGS,IHEP/Beijing + by-products and small scale expts.: INR-Kiev + neutron meas.: ENEA-Frascati + in some studies on decays (DST-MAE project): IIT Kharagpur, India DAMA/LXe DAMA/NaI DAMA/R&D low bckg DAMA/Ge for sampling meas. meas. with Mo 100 DAMA/LIBRA http://people.roma2.infn.it/dama
DAMA/LXe: results on rare processes Dark Matter Investigation Limits on recoils investigating the DMp-129Xe elastic scattering by means of PSD Limits on DMp-129Xe inelastic scattering Neutron calibration 129Xe vs 136Xe by using PSD SD vs SI signals to increase the sensitivity on the SD component NIMA482(2002)728 PLB436(1998)379 PLB387(1996)222, NJP2(2000)15.1 PLB436(1998)379, EPJdirectC11(2001)1 foreseen/in progress Other rare processes: Electron decay into invisible channels Nuclear level excitation of 129Xe during CNC processes N, NN decay into invisible channels in 129Xe Electron decay: e e - PLB493(2000)12 Xenon01 PLB527(2002)182 Improved results on in 134Xe,136Xe CNC decay 136Xe 136Cs N, NN, NNN decay into invisible channels in DAMA/R&D set-up: results on rare NPB563(1999)97, Particle Dark Matter search with CaF (Eu) processes Astrop.Phys.7(1997)73 2 PLB465(1999)315
PRD61(2000)117301 2 decay in 136Xe 2 decay in 134Xe 2 decay in 136Ce and in 142Ce 2EC2 40Ca decay 2 decay in 46Ca and in 40Ca 2+ decay in 106Cd 2 and decay in 48Ca 2EC2 in 136Ce, in 138Ce and decay in 142Ce 2+ 0 and EC + 0 decay in 130Ba Cluster decay in LaCl3(Ce) CNC decay 139La 139Ce decay of natural Eu decay of 113Cd decay of 64Zn decay of 108Cd and 114Cd Astrop.P.5(1996)217 PLB546(2002)23 Beyond the Desert (2003) 365 EPJA27 s01 (2006) 35 Xe 136 DAMA/Ge & LNGS Ge facility Il Nuov.Cim.A110(1997)189 Astrop. Phys. 7(1997)73 NPB563(1999)97 Astrop.Phys.10(1999)115 NPA705(2002)29 NIMA498(2003)352 NIMA525(2004)535
NIMA555(2005)270 UJP51(2006)1037 NPA789(2007)15 PRC76(2007)064603 PLB658(2008)193 EPJA36(2008)167 RDs on highly radiopure NaI(Tl) set-up; several RDs on low background PMTs; qualification of many materials measurements with a Li6Eu(BO3)3 crystal (NIMA572(2007)734) measurements with 100Mo sample investigating decay in the 4 lowbckg HP Ge facility of LNGS (to appear on Nucl. Phys. and Atomic Energy) search for 7Li solar axions (NPA806(2008)388) +Many other meas. already scheduled for near future Il Nuovo Cim. A112 (1999) 545-575, EPJC18(2000)283, Riv. N. Cim. 26 n.1 (2003)1-73, IJMPD13(2004)2127 Reduced standard contaminants (e.g. U/Th of order of ppt) by material selection and growth/handling protocols. PMTs: Each crystal coupled - through 10cm long tetrasil-B light guides acting as optical windows - to 2 low background EMI9265B53/FL (special development) 3 diameter PMTs working in coincidence. Detectors inside a sealed Cu box maintained in HP Nitrogen atmosphere in slight overpressure Very low radioactive shields: 10 cm of Cu, 15 cm of Pb + shield from neutrons: Cd foils + polyethylene/paraffin+ ~ 1 m concrete moderator largely surrounding the set-up Installation sealed: A plexiglas box encloses the whole shield and is also maintained in HP Nitrogen atmosphere in slight overpressure. Walls, floor, etc. of inner installation sealed by Supronyl (210-11 cm2/s permeability).Three levels of sealing. Installation in air conditioning + huge heat capacity of shield Calibration using the upper glove-box (equipped with compensation chamber) in HP Nitrogen atmosphere in slight overpressure calibration in the same
running conditions as the production runs. Energy and threshold: Each PMT works at single photoelectron level. Energy threshold: 2 keV (from X-ray and Compton electron calibrations in the keV range and from the features of the noise rejection and efficiencies). Data collected from low energy up to MeV region, despite the hardware optimization was done for the low energy Pulse shape recorded over 3250 ns by Transient Digitizers. Monitoring and alarm system operating byfor self-controlled Main procedures of thecontinuously DAMA data taking the DMpcomputer annual modulation signature processes. ofelectronics each annual cycle autumn/winter data taking + and DAQstarts fully from renewed in summer (when 2000 cosw(t-t0)0) toward summer (maximum expected). routine calibrations for energy scale determination, for acceptance windows efficiencies by means of radioactive sources each ~ 10 days collecting typically ~10 5 evts/keV/detector + intrinsic calibration from 210 Pb (~ 7 days periods) + periodical Compton calibrations, etc. The former DAMA/NaI(Tl)~100 kg ut of operation on July 2002,still producing results)
Performances: N.Cim.A112(1999)545 EPJC18(2000)283, Riv.N.Cim.26 n. 1(2003)1, IJMPD13(2004)2127 Results on rare processes: Possible Pauli exclusion principle violation PLB408(1997)439 CNC processes PRC60(1999)065501 Electron stability and non-paulian transitions in Iodine atoms (by L-shell) PLB460(1999)235 Search for solar axions PLB515(2001)6 Exotic Matter search EPJdirect C14(2002)1 Search for superdense nuclear matter EPJA23(2005)7 Search for heavy clusters decays EPJA24(2005)51 Results on DM particles: PSD PLB389(1996)757 Investigation on diurnal effect N.Cim.A112(1999)1541 Exotic Dark Matter search PRL83(1999)4918 Annual Modulation Signature PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23,EPJ C18(2000)283, PLB509(2001)197, EPJ C23 (2002)61, PRD66(2002)043503, Riv.N.Cim.26 n.1 (2003)1-73, IJMPD13(2004)2127, IJMPA21(2006)1445, EPJC47(2006)263, IJMPA22(2007)3155, EPJC53(2008)205, PRD77(2008)023506, MPLA23(2008)2125. data taking completed on July 2002 total exposure collected in 7 annual cycles 107731 kgd
1) Search for non-paulian nuclear processes Proton emission Ep> 10 MeV Example of a process violating PEP: deexcitation of a nucleon from the shell Ni to the No lower (full) shell. The energy is converted to another nucleon at shell N through strong interaction, resulting to excitation to the unbound region. (analogy: Auger emission) PEP violating transition PEP violation parameter (mixing probability of non fermion statistics) ~ 2 PEP violating transition width PEP allowed transition width (as if the state No would be empty) 1) Search for non-paulian nuclear processes PLB 408 (1997) 439 Example of a previous results with 100 Kg low background DAMA/NaI
N x t = 2.46 1032 nuclei x s NaI(Tl) 6.13 x 107 kg x s 0 events in the 10 - 36 MeV range internal s s PLB 408 (1997) 439 proton detection efficiency 100% 4.610 33 s 1 (68% C.L.) 1) Search for non-paulian nuclear processes Calculation of PEP allowed transition direct exchange Coulomb barrier effect: low energy protons cannot escape from the nucleus ~ PLB 408 (1997) 439 Momentum distribution function of nucleons in the bound state calculated in 2 cases: a) Fermi distribution kf = 255MeV/c b) realistic distribution functions accounting for correlation effects (PRC43(1991)1155 very similar for all nuclei with A>12 used the case of 56Fe) 1) Search for non-paulian nuclear processes PLB 408 (1997) 439
average escape prob. of the excited proton Width calculated for escape and tunneling prob. of the excited proton gW(k) = gc(k) = 1 Models for momentum distribution function Limits on 2 are strongly model dependent; a cautious approach could be to consider: Assuming to have the same ~ threshold dependence of Lower limit on the mean life for nonpaulian proton emission: y for Na, 23 > 0.7 x 1025 > 0.9 x 1025 y for I 127 2) Search for non-paulian electronic transitions to L-shell Electronic configuration schema of I anion (54 electrons) in Na +Icrystal
M L PEP violating electron K s p d example of a PEP violating transition of Iodine electron to the full L-shell followed by the atomic shells rearrangement. The total released energy (x-ray + Auger electrons) is approximately equal to L-shell ionization potential ( 5 keV) 2) Search for non-paulian electronic transitions to PLB 460 (1999) 236 L-shell Exposure: 19511 kg x day 2 annual cycles with low background DAMA/NaI N x t = 1.72 1027 L-shell electrons x year N t S detection efficiency for low energy x-rays and Auger electrons 100% in large NaI(Tl) S < 413(715) 68%(90%) C.L. Considering that typical atomic transition lifetime are at timescale of ns P < few 10-42 are
> 4.2 x 1024 y (68% C.L) Also limit on electron stability for the process: e- 3, majoron+ or anything invisible. The new DAMA/LIBRA set-up ~250 kg NaI(Tl) (Large sodium Iodide Bulk for RAre processes) As a result of a second generation R&D for more radiopure NaI(Tl) by exploiting new chemical/physical radiopurification techniques (all operations involving crystals and PMTs - including photos - in HP Nitrogen atmosphere) installing DAMA/LIBRA detectors assembling a DAMA/ LIBRA detector detectors during installation; in the central and right up detectors the new shaped Cu shield surrounding light guides (acting also as optical windows) and PMTs was not yet applied filling the inner Cu box with further shield closing the Cu box housing the detectors view at end of detectors installation in the Cu box DAMA/LIBRA~250 ~250kg kgNaI(Tl) NaI(Tl) DAMA/LIBRA (Largesodium sodiumIodide IodideBulk
Bulkfor forRAre RAreprocesses) processes) (Large As a result of a second generation R&D for more radiopure NaI(Tl) by exploiting new chemical/physical radiopurification techniques (all operations involving crystals and PMTs - including photos - in HP Nitrogen atmosphere) PMT +HV divider etching staff at work in clean room Cu etching with super- and ultrapure HCl solutions, dried and sealed in HP N2 storing new crystals improving installation and environment An example: the Cu etching The Cu etching was performed in a clean room following a devoted protocol: vessel I: pre-washing of the brick in iper-pure waterc vessel II: washing in 1.5l of HCl 3M super-pure vessel III: first rinse with iper-pure water (bath) vessel IV: second rinse with iper-pure water (current) vessel V: washing in 1.5l of HCl 0.5M ultra-pure etching staff at work in clean room vessel VI: first rinse with iper-pure water (bath) vessel VII: second rinse with iper-pure water (current) vessel VIII: third rinse with iper-pure water (current)
bricks dried with selected clean towels and HP N2 flux bricks sealed in two envelopes (one inside the other) flowed and filled with HP N2 Very clean materials (teflon and high purity OFHC copper, selected vessels and gloves) were used. Special tools were also used to help managing the bricks to minimize the contact with gloves. The residual contaminants in HCl are certified by the producer, in particular standard contaminants are quoted: 10 ppb for natK and 1 ppb or U/Th for super-pure HCl and 100 ppt of natK and 1 ppt for U/Th in case of ultra-pure HCl. For each brick the bath was changed and after each step the solution of the bath was analysed with ICP-MS technique. Residual contaminants were checked in order to optimize the choice of the materials (in particular for gloves) and the cleaning procedure. After cleaning, each brick was stored underground. Polyethylene/ paraffin 25 x 9.7 kg NaI(Tl) in a 5x5 matrix two Suprasil-B light guides directly coupled to each bare crystal For details, radiopurity,performances, procedures, etc. NIMA592(2008)297 Installation Glove-box for calibration Electronics + DAQ two PMTs working in coincidence at the single ph. el. threshold 1m concrete from GS rock
Dismounting/Installing protocol (with Scuba system) All the materials selected for low radioactivity Multicomponent passive shield Three-level system to exclude Radon from the detectors Calibrations in the same running conditions as production runs Installation in air conditioning + huge heat capacity of shield Monitoring/alarm system; many parameters acquired with the production data Pulse shape recorded by Waweform Analyzer TVS641A (2chs per detector), 1 Gsample/s, 8 bit, bandwidth 250 MHz Data collected from low energy up to MeV region, despite the Shield from environmental radioactivity Heavy shield: >10 cm of Cu, 15 cm of Pb + Cd foils, 10/40 cm Polyethylene/paraffin, about 1 m concrete (mostly outside the installation) High radiopure materials, most underground since at least about 15 years New shaped Cu shield Pb and Cu etching and handling in clean room. surrounding light Storage underground in packed HP N2 atmosphere guides and PMTs Three-level system to exclude Radon from the detectors:
Walls and floor of the inner installation sealed in Supronyl (210-11 cm2/s permeability). Whole shield in plexiglas box maintained in HP Nitrogen atmosphere in slight overpressure with respect to environment Detectors in the inner Cu box in HP Nitrogen atmosphere in slight overpressure with respect to environment Residual radioactivity in some components of the Cu box (95% C.L.) Sensitivity limited by the method Residual contaminants in some components of the passive shield (95% C.L.) ome on residual contaminants in new NaI(Tl) detector Second generation R&D for new DAMA/LIBRA crystals: new selected powders, physical/chemical radiopurification, new selection of overall materials, new protocol for growing and handling /e pulse shape discrimination has practically 100% effectiveness in the MeV range The measured yield in the new DAMA/LIBRA detectors ranges from 7 to some tens /kg/day e From time-amplitude method. If 232Th chain at equilibrium: it ranges from 0.5 ppt to 7.5 ppt Th residual contamination 232 U residual contaminationFirst estimate: considering the measured and 232 Th activity, if 238U chain at equilibrium 238U
contents in new detectors typically range from 0.7 live time = 570 h to 10 ppt 238 238 U chain splitted into 5 subchains: U 234U 230Th 226Ra 210Pb 206Pb 3 238 Thus, in this case: (2.10.1) ppt of 2 and: (15.81.6) Bq/kg for for 210Pb. 4 1 nat 5 234 U+ 230 Th; (21.71.1) Bq/kg for K residual contamination The analysis has given for the nat K content in the crystals values not exceeding about 20 ppb I and 129
Th; (0.35 0.06) ppt for 232 226 U 238 Ra; (24.21.6) Bq/kg double coincidences Pb 210 I/natI 1.710-13 for all the new detectors 210 Pb in the new detectors: (5 30) Bq/kg. 129 No sizeable surface pollution by Radon daugthers, thanks to the new handling ... more on NIMA592(2008)297 Infos about DAMA/LIBRA data taking EPJC56(2008)333 NIMA592(2008)297 DAMA/LIBRA test runs: from March 2003 to September 2003 DAMA/LIBRA normal operation:
from September 2003 to August 2004 High energy runs for TDs: September 2004 to allow internal s identifications identification (approximative exposure 5000 kg d) DAMA/LIBRA normal operation: from October 2004 Data released here: four annual cycles: 0.53 ton yr calibrations: acquired 44 M events from sources acceptance window eff: acquired 2 M events/keV DAMA/NaI (7 years) + DAMA/LIBRA (4 years) Two remarks: total exposure: 300555 kgday = 0.82 tonyr One PMT problems after 6 months. Detector out of trigger from Sep. 2003 to the 2008 update. Now again in operation. Residual cosmogenic 125I presence in the first year in some detectors (this motivates the Sept. 2003 as starting time) DAMA/LIBRA is continuously running Perspectives for PEP investigations with DAMA/LIBRA 1) Search for non-paulian nuclear processes Radiopurities of the new DAMA/LIBRA detectors (and
set up) are improved by respect to the case of DAMA/NaI. Very low background expected also in the 10 - 36 MeV energy window. Exposure larger than the previous 6.13 x 107 kg x s can be achieved in 4 days of dedicate high energy data taking. WORK IN PROGRESS 2) Search for non-paulian electronic transitions to Lshell Iodine L-shell EPJC56(2008)333 NIMA592(2008)2 97 The present DAMA/LIBRA collected exposure 0.53 tons x year is a factor 10 larger than 19511 kg x day of previous PLB 460 (1999) 236. The background in the 5 keV region has been improved of a factor 2. The DAMA/LIBRA sensitivity to electronic non-paulian transitions to a full L-shell in Iodine is at level of: > 1.5 x 1025 years at 68% C.L Perspectives for PEP investigations with DAMA/LIBRA 3) Search for non-paulian electronic transitions to K-shell example for a DAMA/LIBRA detector
Iodine K-shell Pb: a= (293) Bq/kg No sizeable surface pollution by Radon daugthers, thanks to the new handling protocols 210Pb in the new DAMA/LIBRA detectors typically ranges: (5 30) Bq/kg. 210 Pb peak is absent in most of the new DAMA/LIBRA detectors. 210 I/natI (1.70.1)1013 129 = The amount of cosmogenic 129I (+) is at the same level (1.710-13) for all the new detectors (if used for dating the > few x 10 years 25 NaI powders extracted from ore with an age of order of 50 Myr) ... more on NIMA592(2008) 297 And more, a DAMA/LIBRA upgrade allowing 1 keV threshold is WORK IN PROGRESS planned. Possible investigation of Sodium K-shell (1
keV). CONCLUSION S Lifetimes at level of 1025 years both for non-paulian nuclear processes and for non-paulian electronic transitions can be investigated by DAMA/LIBRA. Non-paulian mixing probability at level of P<10 -54 for nucleons and P<10 -42 for e If something in fundamental can be explored. physics can be tested, then it absolutely must be tested
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