Searches for processes violating the Pauli Exclusion Principle in Sodium and Iodine. F. Nozzoli University & INFN Roma Tor Vergata. NPA4 Frascati, 8-12 June, 2009. Pauli Exclusion Principle (PEP) has a crucial role in physics. Experimental atomic spectra. Periodic table of elements. PEP.
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Searches for processes violating the Pauli Exclusion Principle in Sodium and Iodine
University & INFN
Roma Tor Vergata
Frascati, 8-12 June, 2009
Pauli Exclusion Principle (PEP)
has a crucial role in physics
Experimental atomic spectra
Periodic table of elements
Nuclear and condensed matter phenomenology
commutation/anti-commutation relations of a and a+ in QFT
Discovery of color in QCD
Many experimental evidences/successes but a simple and easy explanation is still missing as stressed by Feynmann.
Why test Pauli Exclusion Principle (PEP)?
Phys. Rev. Lett. 64 (1990) 705
Phys. Lett. B 242 (1990) 407
Fund. Phys. 29 (1999) 397.
...many theoretical attempts to go beyond Bose and Fermi statistics ...
small probability of admixed symmetric component
BUT also apparent PEP violations due to physics at higher energy scale
Phys. Rev. Lett. 68 (1992) 1826
superficial PEP violations due to possible substructure in composite models of quark and leptons
composite electron size
apparent PEP violations due extra dimensions: Phys. Rev. D 39 (1989) 2032
If something in fundamental physics can be tested, then it absolutely must be tested (Okun)
4 classes of experiments:
Phys. Lett. B 240 (1990) 227
Phys. Rev. Lett. 74 (1995) 4787
JETP Lett. 68 (1998) 112
Phys. Rev. Lett. 85 (2000) 2701
1) searches for PEP-forbidden electronic states in atoms
2) searches for PEP-forbidden nuclear states
J. Phys. G 17 (1991) S355.
Nucl. Phys. B (Proc. Suppl.) 28A (1992) 219
Phys. Lett. B 460 (1999) 236
Phys. Lett. B 641 (2006) 18
Int. J. Mod. Phys. A 22 (2007) 242
3) searches for PEP-forbidden electronic transitions
Phys. Lett. B 306 (1993) 218
Phys. Lett. B 408 (1997) 439
Eur. Phys. J. A 6 (1999) 361
Nucl. Phys. B (Proc. Suppl.) 87 (2000) 510
Eur. Phys. J. C 37 (2004) 421
4) searches for PEP-forbidden nuclear transitions
Underground experiment site and high radiopurity set-up allow to reduce background due to PEP-allowed transitions induced by cosmic rays or environmental radioactivity
DAMA: an observatory for rare processes @LNGS
low bckg DAMA/Ge
for sampling meas.
meas. with 100Mo
DAMA/LXe: results on rare processes
Beyond the Desert (2003) 365
EPJA27 s01 (2006) 35
DAMA/R&D set-up: results on rare processes
DAMA/Ge & LNGS Ge facility
Astrop. Phys. 7(1997)73
NPA(2009) in press
DAMA/NaI : 100 kg NaI(Tl)
Performances:N.Cim.A112(1999)545-575, EPJC18(2000)283, Riv.N.Cim.26 n. 1(2003)1-73, IJMPD13(2004)2127
Results on rare processes:
data taking completed on July 2002, last data release 2003. Still producing results
Results on DM particles:
PLB424(1998)195, PLB450(1999)448, PRD61(1999)023512, PLB480(2000)23, EPJC18(2000)283, PLB509(2001)197, EPJC23(2002)61, PRD66(2002)043503, Riv.N.Cim.26 n.1 (2003)1, IJMPD13(2004)2127, IJMPA21(2006)1445, EPJC47(2006)263, IJMPA22(2007)3155, EPJC53(2008)205, PRD77(2008)023506, MPLA23(2008)2125.
model independent evidence of a particle DM component in the galactic halo at 6.3s C.L.
total exposure (7 annual cycles) 0.29 ton x yr
The new DAMA/LIBRA set-up ~250 kg NaI(Tl)
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)
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
installing DAMA/LIBRA detectors
assembling a DAMA/ LIBRA detector
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
Some on residual contaminants in new NaI(Tl) detectors
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
a/e pulse shape discrimination has practically 100% effectiveness in the MeV range
The measured a yield in the new DAMA/LIBRA detectors ranges from 7 to some tens a/kg/day
From time-amplitude method. If 232Th chain at equilibrium: it ranges from 0.5 ppt to 7.5 ppt
232Th residual contamination
First estimate: considering the measured aand 232Th activity, if 238U chain at equilibrium 238U contents in new detectors typically range from 0.7 to 10 ppt
238U residual contamination
live time = 570 h
238U chain splitted into 5 subchains: 238U 234U 230Th 226Ra 210Pb 206Pb
Thus, in this case: (2.1±0.1) ppt of 232Th; (0.35 ±0.06) ppt for 238U
and: (15.8±1.6) Bq/kg for 234U + 230Th; (21.7±1.1) Bq/kg for 226Ra; (24.2±1.6) Bq/kg for 210Pb.
natK residual contamination
The analysis has given for the natK content in the crystals values not exceeding about 20 ppb
129I and 210Pb
129I/natI ≈1.710-13 for all the new detectors
... more on NIMA592(2008)297
210Pb in the new detectors: (5 − 30) mBq/kg.
No sizeable surface pollution by Radon daugthers, thanks to the new handling protocols
A) Search for non-paulian nuclear processes
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)
Ep> 10 MeV
for 23Na and 127I:
PEP violating transition
PEP violation parameter
(mixing probability of non fermion statistics)
PEP violating transition width
PEP allowed transition width (as if the state No would be empty)
Calculation of PEP allowed transition
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)
Coulomb barrier effect: low energy protons cannot escape from the nucleus
The former results obtained with 100 Kg low background DAMA/NaI
For PEP violating nuclear processes: events where just one detector fires.
PLB 408 (1997) 439
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
PLB 408 (1997) 439
Є proton detection efficiency ≈ 100%
Assuming to have the same threshold dependence of
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:
Lower limit on the mean life for non-paulian proton emission: > 0.7 x 1025 y for 23Na, > 0.9 x 1025 y for 127I
First results on PEP-violating nuclear processes with DAMA/LIBRA
570h running time, optimized for very high energy
At very high energy (E > 10 MeV) background is due to the very high energy muons possibly surviving the mountain.
For PEP violating nuclear processes:
events where just one detector fires.
BKG Muon events evaluated by MC non present in the inner core (veto)
For E > 10 MeV
17 events in the upper/lower plane of detector (10 cryst.)
0 events in the central planes of detector (14 cryst.)
Lower limit on the mean life for non-paulian proton emission: > 2 x 1025 y for 23Na, > 2.5 x 1025 y for 127I
DAMA/LIBRA expected sensitivity in case of 3 yr of data taking optimized for high energy
SpinStat08 in Foundation of Physics, to appear
events where just one detector fires.
no background contribution is expected in the 9 NaI(Tl) detectors in the inner core (c) of DAMA/LIBRA during ~ 1000 days exposure in the 10 - 35 MeV energy interval interesting for PEP
Reachable by DAMA/LIBRA with 3 yr exposure optimized for high energy and without any simulated muon background subtraction
> 1 order of magnitude improvement with respect to available limits for 23Na and 127I
B) Search for non-paulian electronic transitions
PEP violating electron
Electronic configuration schema of I anion (54 electrons) in Na+I- crystal
example of a PEP violating transition of Iodine electron to the full k-shell followed by the atomic shells rearrangement. The total released energy (x-ray + Auger electrons) is approximately equal to k-shell ionization potential ( ≈ 32 keV)
First results on PEP-violating electronic transitions with DAMA/LIBRA
Exposure: 0.53 ton × yr
tPV> 4.7 x 1030 s (90% C.L.)
normal electromagnetic dipole transition to Iodine K-shell:
t0 ≈6 x 10-17 s
de2 < 1.28 10-47 (90% C.L.).
one order of magnitude more stringent than the previous one (ELEGANTS V)
(VIP sensitivity with a different approach in Cu sample is 10-28 with final goal 10-31)
This limit can also be related to a possible finite size of the electron in composite models of quarks and leptons providing supercial violation of the PEP; the obtained upper limit on the electron size is: r0 < 5.710-18 cm (energy scale of E > 3.5 TeV).