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Page 1: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli
Page 2: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Pauli exclusion principle (PEP) violationThe exclusion principle was postulated by Pauli in 1925 to explain atomic spectra

and regularities of the Periodic Table of the elements.

In modern Quantum Field Theory the PEP is related to the spin statistics and

automatically arises from the anti-commutation property of the fermion creation

and destruction operators

Although all the well known successes of the PEP in explaining phenomena the

exact validity of the PEP is still an open question

Despite the fact that the foundation of PEP lies deep in the structure of Quantum

Field Theory a simple and easy explanation is still missing

General principles of quantum theory do not require that all the particles must be

either fermions or bosons, but also generalized statistics could be considered

Similar arguments have inspired many experimental tests of the PEP validity with

improved sensitivities since the first pioneering experiments in 1948

[Ph.Rev.73(1948)1472]

In particular, four classes of experiments have been considered so far:

1. searches for PEP-forbidden electronic states

2. searches for PEP-forbidden nuclear states

3. searches for PEP-forbidden electronic transitions

4. searches for PEP-forbidden nuclear transitions

Page 3: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Since 1948 many experimental tests of CNC processes have been performed

The first test was the search for possible PEP-forbidden (PEPf) electronic states

The best sensitivities obtained for 4 classes of experiments for PEPf states are:

Experimental tests for PEP violation

Experiment Result Ref.

searches for PEPf

electronic states in atoms

[12C']/[12C] < 2.5∙10-12

[Be']/[Be] < 9∙10-12

A.S. Barabash et al., JETPL 68 (1998) 112

D. Javorsek II et al., PRL 85 (2000) 2701

searches for PEPf nuclear

states[5He']/[4He] < 2∙10-15 E. Nolte et al., J. Phys. G 17 (1991) S355

searches for PEPf

electronic transitions

δ2< 4.7∙10-29

δ2< 1.1∙10-46

δ2 < 1.3∙10-47

C. Curceanu et al., JP:Con.Se. 306(2011)012036

H. Ejiri et al., NPB(Proc.Sup.) 28A (1992) 219

R. Bernabei et al., EPJC 62 (2009) 327

searches for PEPf nuclear

transitions

δ2 < 3-4∙10-55

δ2< 4.1∙10-60

R. Bernabei et al., EPJC 62 (2009) 327

G. Bellini et al., PRC 81 (2010) 034317

It is worth noting that in 1980 Amado & Primakoff [PRC 22(1908)1338] criticized the

possibility of testing the Pauli principle by looking for PEP-forbidden transitions.

However their arguments can be evaded either as demonstrated in PRL

68(1992)1826 or PRD39(1989)2032 (for example extra dimensions could lead to

apparent PEP violations)

Thus experimental tests of PEPf transitions can also investigate the deep structure

of matter and/or of space-time

Page 4: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Charge Non-Conserving (CNC) processes

Electric Charge Conservation (CC) is a fundamental law in QED

This law is correlated with gauge invariance and photon mass (Weinbergtheorem)

The possibility that CC may be broken in future unified theories and the relative implications have been discussed in last years since the first experimental test in 1959

At present no self-consistent theories have been developed, but in some modern theories (for example extra-dimensions) these processes can bepossible

In 1978 Zeldovich, Voloshin and Okun considered problems due to a

phenomenological description of CNC processes; they demonstrated that

CNC can not be due to a spontaneus breaking if photon mass is zero

CNC processes are possible if photon mass is not zero

Page 5: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Since 1959 many experimental tests fot CNC processes have been done

The first test was the search for electron decay, but other possible processes have been considered

The best sensitivities obtained for some CNC precesses are:

Experimental tests for CNC processes

Process τ (yr) Ref.

CNC-β decay (71Ga) >1.4∙1027 M. Torres et al. MPLA 19 (2004) 639

p→anything >4∙1023 V.I. Tretyak & Yu.G. Zdesenko PLB 505 (2001) 59

p→invisibile >2.1∙1029 S. N. Ahmed et al. PRL 92 (2004) 102004

n→invisibile >5.8∙1029 T. Araki et al. PRL 96 (2006) 101802

pp→invisibile >5.0∙1025 H.O. Back et al. Phys. Lett. B 563 (2003) 23

nn→invisibile >1.4∙1030 T. Araki et al. PRL 96 (2006) 101802

nnp→invisibile >1.4∙1022 R.Bernabei et al., EPJA 27,s01(2006)35

npp→invisibile >2.7∙1022 R.Bernabei et al., EPJA 27,s01(2006)35

ppp→invisibile >3.6∙1022 R.Bernabei et al., EPJA 27,s01(2006)35

e-→invisible >2.4∙1024 P.Belli et al. PLB 460(1999)236

e-→νeγ >4.6∙1026 H. O. Back et al. PLB 525(2002)29

CNC-Elect. Capt. (129Xe) >3.7∙1024 P.Belli et al. PLB 465(1999)315

[S.N.Gninenko, arXiv:0707.3492]

Page 6: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

DAMA/R&DDAMA/LXe low bckg DAMA/Ge

for sampling meas.

DAMA/NaI

DAMA/LIBRA

http://people.roma2.infn.it/dama

Roma2,Roma1,LNGS,IHEP/Beijing

+ by-products and small scale expts.: INR-Kiev+ neutron meas.: ENEA-Frascati+ in some studies on bb decays (DST-MAE project): IIT Kharagpur, India

DAMA/CRYS

Page 7: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

DAMA/LXe: results on CNC processes

• Electron decay into invisible channels [Astrop.P.5(1996)217]

• Nuclear level excitation of 129Xe during CNC processes

[PLB465(1999)315]

• N, NN decay into invisible channels in 129Xe [PLB493(2000)12]

• Electron decay: e- νeγ [PRD61(2000)117301]

• CNC decay 136Xe 136Cs [Beyond the Desert(2003)365]

• N, NN, NNN decay into invisible channels in 136Xe

[EPJA27 s01 (2006) 35]

• CNC decay 139La 139Ce [UJP51(2006)1037]

DAMA/R&D set-up: results on CNC 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]

DAMA/NaI: results on CNC processes and PEPv

Page 8: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

25 x 9.7 kg NaI(Tl) in a 5x5 matrix

Two Suprasil-B light guides directly coupled to each bare crystal

Two PMTs working in coincidence at the single ph. el. threshold

5.5-7.5 phe/keV

DAMA/LIBRA set-up

• All the materials selected for low radioactivity

• Multicomponent passive shield (>10 cm of Cu, 15 cm of Pb + Cd foils,

10/40 cm Polyethylene/paraffin, about 1 m concrete, mostly outside the

installation)

• Three-level system to exclude Radon from the detectors

Glove-box for

calibration

Electronics + DAQ

Installation

Glove-box for

calibration

Electronics + DAQ

Installation

• 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 Acqiris DC270 (2chs per detector), 1 Gsample/s, 8 bit, bandwidth 250 MHz

• Data collected from single photoelectron up to MeV region, despite the hardware optimization was done for the low energy

Page 9: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

The new DAMA/LIBRA set-up ~250 kg NaI(Tl)(Large sodium Iodide Bulk for RAre processes)

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

Residual contaminations in the new DAMA/LIBRA NaI(Tl) detectors:

232Th, 238U and 40K at level of 10-12 g/g

installing DAMA/LIBRA detectors

assembling a DAMA/ LIBRA detector

filling the inner Cu box with further shield

closing the Cu box

housing the detectors

Page 10: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

...calibration procedures

• Radiopurity,performances, procedures, etc.: NIMA592(2008)297

• Results on DM particles: DM Annual Modulation Signature: EPJC56(2008)333, EPJC67(2010)39

Results on rare processes: PEP violation in Na and I: EPJC62(2009)327

Page 11: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

1) Search for non-paulian nuclear processes

This process was studied in 1997 with

DAMA/NaI set-up obtaining a sensitivity of

> 0.7 × 1025 y for 23Na (68% C.L.)

> 0.9 × 1025 y for 127I (68% C.L.)

Example of a process PEP violating:deexcitation of a nucleon from the shell Ni to theN0 lower (full) shell

The energy is converted to another nucleon atshell N through strong interaction, resulting toexcitation to the unbound region (analogy:Augér emission)

PEP forbidden transitions (1/2)Underground experimental site and highly radiopure set-up allow to reduce

background due to PEP-allowed transitions induced by cosmic rays and due

to environmental radioactivity

PEPf

transition

internal ’s

PLB 408 (1997) 439

Page 12: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Electronic configuration schema of I anion (54 electrons) in Na+I- crystal

K

L

M

s p d

example of a PEP violating transition of Iodine electron to the full L-shell followedby the atomic shells rearrangement

The total released energy (X-ray + Augér electrons) is approximately equal to L-shell ionization potential ( ≈ 5 keV)

PEP violating electron

PEP forbidden transitions (2/2)

2) Search for non-paulian electronic transitions to L-shell

In 1999 DAMA searched for this process in DAMA/NAI obtaining the sensitivity:

τ > 4.2×1024 yr (68% C.L.) [P. Belli et al., PLB 460 (1999) 236]

Page 13: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

PEP-violating nuclear processes (1/2)

Above 10 MeV background due to very high energy muons

possibly surviving the mountain.

Continous line:

bkg muon events

evaluated by MC

not 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.)

EPJC 62 (2009) 327570h running time, optimized for very high energy

For PEP violatingnuclear processes:events where just one detector fires

Mainly particlesfrom internal contaminants

Page 14: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

I II II II I

III III III III

III III III III III

III III III III III

I II II II I

Lower limit on the mean life for non-paulianproton emission in frame b) (90% C.L.):

> 2 x 1025 y for 23Na > 2.5 x 1025 y for 127I

cautious approach:

PEP-violating nuclear processes (2/2)

IV

a) Fermi momentum distribution with

kF = 255 Mev/c

b) 56Fe momentum distribution accounting

for correlation effects

EPJC 62 (2009) 327

Page 15: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Exposure: 0.53 ton × yr

This limit can also be related to a possible finite size of the electron in composite models of

quarks and leptons providing superficial violation of the PEP

de2 < 1.28 10-47 (90% C.L.).

PV > 4.7 x 1030 s (90% C.L.)

excluded

considering normal electromagneticdipole transition to Iodine K-shell:

0 ≈ 6 x 10-17 s

one order of magnitude more stringent

than the previous one (ELEGANTS V)

PEP-violating electron processes

The obtained upper limit on the electron size is:

r0 < 5.710-18 cm (energy scale E > 3.5 TeV)[PRL 68(1992)1826]

EPJC 62 (2009) 327

Page 16: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Possible electron decay CNC:

e-→νeγ

e-→νe ν ν

e-→nothing

e-+(A,Z) → νe+(A,Z)* [CNC electron capture]

(A,Z) → νe+(A,Z+1)*+νe [CNC β-decay]

electron disappearance

Searches for invisible decays are also related with extra-dimensions:

Probably, our world is a brane inside higher-dimensional space

Particles can escape from the brane to extra dimensions

“The presence and properties of the extra dimensions will be investigated

by looking for any loss of energy from our 3-brane into the bulk” [N.Arkani-

Hamed et al., PLB 429(1998)263]

Thus we could expect disappearance of e, p, n...

η(p→nothing) = 9.2×1034 y η(e → nothing) = 9.0×1025 yr[S.L.Dubovsky, JHEP 01(2002)012]

Page 17: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

CNC Electron capture (1/5)e-+(A,Z) → νe+(A,Z)* This process is more probable by K-shell electrons!

In NaI(Tl) detectors the possible excited states that can be produced by this process are: 127I four possible excited states: 57.6 keV, 202.8 keV, 375 keV and 418 keV23Na one excited state at 440 keV

We search for γ emitted in de-excitation processes

238.6 keV(212Pb)

338.3 keV(228Ac)

DAMA/LIBRA high-energy distribution

This process is followed by relaxation of the atomic shellswith emissions at energy = electron disappeared boundingenergy Eb

Na: EK = 1.1 keV

I: EK = 33.3 keV

We choose preliminarly to study the production of 127I in the excited level 418 keV

To improve our sensitivity and reduce the background we search for events in coincidence

Each CNC electron capture in Iodine produces X-rays/Augér electrons at 33.3 keV and γ emission due to de-

excitation processes of 127I (for example for the 418 keV level γ energies 418 keV, 203 keV and 360 keV)

Exposure 0.87 ton × yr

Page 18: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

CNC Electron capture (2/5)With Montecarlo simulation (3600000 events) we obtain:

Expected distribution for

events in coincidence

with multiplicity 2

Peak at 33.3 keV Fixing the energy

window 24.7-41.9keV

in one detector

We expect a peak

at energy 418 keV

due to 127I de-

excitation

Selection of events in coincidence with multiplicity 2 in DAMA/LIBRA (0.87 ton×yr

exposure) in the energy window 24.7-41.9 keV for the first one and 371.6-464.4 keV for

the second one gives 26273 candidates events for this process

Using 1ζ-approach we obtain for the expected signal S < 162 events (68% C.L.)

Considering that each Iodine has 2 electron in K-shell we obtain:

η > 1.9 × 1024 yr (68% C.L.)

Efficiency for this

coincidence is 4.5%

EGSnrc Montecarlo simulation EG

Sn

rcM

on

teca

rlo s

imu

latio

n

Page 19: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

CNC Electron capture (3/5)

Montecarlo expectation Experimental data

The experimental data with multiplicity 2 don’t show the expected structures for

events in coincidence: No evidence for any signal!

No correlated events in coincidence!

Comparison of experimental data distribution

with Montecarlo expectation

Page 20: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

CNC Electron capture (4/5)Data selection with multiplicity 2 and the first event

in the energy window 24.7-41.9 keV reduces the

background of a factor larger than 103

Fittting data with a sum of an exponential function

for the continous background and the expected peak

we obtain: S = - (260 ± 296) events

χ2/dof=1.04

Best limits previously obtained for this process by:

DAMA/NaI for the production of excited levels of 127I: η> 2.4·1023 yr

[P.Belli et al., PRC 60(1999)065501]

DAMA/LXe for the production of excited levels of 129Xe: η>3.7·1024 yr

[P.Belli et al., PLB 465(1999)315]

The obtained limit is the best one available for this process in NaI(Tl)

Using Feldman and Cousins procedure:

S < 264 events (90% C.L.), corresponding to:

τ>1.2 × 1024 yr (90% C.L.)

Page 21: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

CNC Electron capture (5/5)The transition probability for the CNC process can be written in therm of a process

mediated by photon exchange or by W-boson exchange:

[Nuclear Data Sheet 112(2011)1647; T. Kibèdi et al., NIMA 589(2008)202]

The CC process can be estimated theoretically (i-initial state, f-final state, n all the

possible intermediate states)

Considering the excited state at 418 keV and the obtained limit: τ > 1.2 × 1024 yr (90% C.L.)

Page 22: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Preliminary analysis exploits the total DAMA/LIBRA published

exposure: 0.87 ton × yr212Pb γ-emission at 238.6 keV estimated by MC considering the

experimental energy resolution

Fit of the energy distribution in the region [193, 293] keV with a

sum of: (i) an exponential; (ii) energy distribution due to 212Pb

decay; (iii) the possible signal due to the CNC process searched

for obtained activity of the possible e → νeγ decay

(χ2/d.o.f. = 1.2): A = - (1.2±1.3) mBq

By Feldman & Cousins procedure: A<0.42 mBq (68% C.L.) and:

[J.N. Bahcall, Rev. Mod. Phys. 50, 881 (1978)]

Exposure 0.87 ton × yr

This process has been here considered to complete the study on electron decay although the presence of a

residual contamination of 212Pb in the set-up (peaked at 238.6 keV) limits the sensitivity in the vicinity

of the peak at Eγ ≈ mec2/2 = 255.5 keV searched for .

Electrons decays in NaI(Tl) crystals, Cu surrounding the crystals (a total copper mass of 1646 kg has been

considered) and crystals light guides (total light guides mass is 50 kg) [the relative contribution are 22% for

copper and 2.6% for light guides] are considered.

Effective efficiency: <ε>=ΣiεiNi/ΣiNi=12.2%

DAMA/LIBRA

preliminary

e-→γνe (1/3)

Page 23: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Further analysis: we selected the 7 detectors (of the 25 ones in DAMA/LIBRA) which have thelower contribution from 212Pb residual contamination in the set-up; exposure is 0.25 ton × yr

The same fitting procedure used above has been applied in the same energy range

The fit (χ2/d.o.f. = 1.1) gives for the possible e → νeγ decay the

activity: A=−(1.0 ± 2.2) mBq

Using Feldmann and Cousins procedure: A<1.3 mBq at 68% C.L.

Largely comparable with the limit obtained above with total

exposure

Best limits previously obtained by:

- 6.5 kg LXe (99.5% 129Xe) DAMA/Lxe: τ > 2.0×1026 yr (90% C.L.) [P.Belli et al., PRD 1(2000)117301]

-10.96 kg HP-Ge HD-MW: τ > 1.9×1026 yr (68% C.L.) [H.V. Klapdor-Kleingrothaus et al., PLB 644(2007)109]

- ~4 ton PXE scintillator BOREXINO: τ > 4.6×1026 yr (90% C.L.) [H. O. Back et al., PLB 525(2002)29]

Our best limit: τ > 4.0×1025 yr

ε2e→γν < 2.6×10−98

It is the best-one with NaI(Tl) detectors, the previous one

was: η > 3.5×1023 yr [E.L. Koval’chuk et al. JETP Lett. 29, 145 (1979)]

Exposure 0.25 ton × yr

e-→γνe (2/3)

Page 24: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

e-→γνe (3/3)This process gives the most restrictive limit on ε2 (<2.3·10−99 [PLB 525(2002)29]) but from

some theoretical considerations this may be not the best way to test CNC:

• Photon mass non-zero needs a non-spontaneous symmetry breaking to preserve QED

• The emission of two or more photons is more probable than the emission of one photon

• Electron decay in neutrinos with a coupling constant g (very little) should beaccompained by a huge amount of photons each one transporting a very little amount ofenergy

Electron decay probability:

it has been demonstrated that

[L. B. Okun et al., Phys. Lett. B 78 (1978) 597 ; M. B. Voloshin et al., Sov. Phys. JETP Lett. 28 (1978) 145 ]

Thus, this may be not the best way to study for Charge Non-Conservation; but,despite problems with a theoretical treatment of this electron’s decay mode, it isnecessary to remind that any “a priori” argument could give wrong results.So experimental tests of the underlying principles of physics should be continueddespite temporary difficulties and lack of theoretical motivation.

Page 25: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Process τ (yr) (this work) τ (yr) (previous best limit) [Ref.]

e-→νγ>1.3×1025 (68% C.L.)

>4.6×1026 (90% C.L.) [H. O. Back et al., PLB 525(2002)29]

(in NaI) >3.5×1023 (68% C.L.) [E.L. Koval’chuk et al., JETPL29(1979)145 ]

EC-CNC (127I) >1.2×1024 (90% C.L.) >2.4·1023 (90% C.L.) [P.Belli et al., PRC 60(1999)065501]

We obtain the best limits available on the life-time of CNC processes for NaI(Tl)

detectors and the best limits available on CNC electron capture.

For the PEP-forbidden transitions the obtained limits on electron transition

probability by DAMA/LIBRA is the best available in literature.

For nuclear transition BOREXINO obtained a more stringent limit in 2010

Processδ2 (yr) DAMA/LIBRA

[EPJC 62 (2009) 327]δ2 (yr) (best limit by other experiments) [Ref.]

Electron

transition<1.28×10-47 (90% C.L.) <1.1·10-46 (68% C.L.) ELEGANTSV [NPB(PS) 28A(1992)219]

Nuclear

transition<3-4×10-55 (90% C.L.) <4.1·10-60 (90% C.L.) BOREXINO [PRC 81 (2010) 034317]

Page 26: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Process ε2 (this work) ε2 (previous best limit) [Ref.]

e-→νγ <2.6×10-98 (68% C.L.) <2.3×10-99 (90% C.L.) [H. O. Back et al., PLB 525(2002)29]

EC-CNC γ <2.5×10-25 (90% C.L.) <9.6·10-26 (90% C.L.) [P.Belli et al., PRC 60(1999)065501]

EC-CNC W <5.0×10-39 (90% C.L.) <4.8×10-40 (90% C.L.) [P.Belli et al., PRC 60(1999)065501]

To compare experimental sensitivity on CNC studied in different processes

in 1978 Bahcall proposed a parametrization for CNC admixtures in weak

interactions [J.N. Bahcall, Rev. Mod. Phys. 50, 881 (1978)]

The violation parameter is given by ε2 ≈ λCNC/λCC ≈ ηCC/ηCNC

For CNC Electron Capture the process can be mediated by photon or W-boson and

the ηCC is given by theoretical estimation with an high uncertainty on parameters

used for

In this work we studied the possible production of 127I at the excited level 418 keV,

to optimize the ε2 determination it’s needed to study the lower excited level (for 127I

the 57.6 keV excited level)

Page 27: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Perspectives for further CNC investigations with DAMA/LIBRA (1/2)

Other possible studies:

Complete the search for 23Na and 127I CNC

Electron-Capture investigating other excited

states

Search for possible nucleons disappearance

(neutron, proton, diproton...)

Study for possible electrons disappearance

Possible studies on electron disappearance from L-shelll can be pursued

Considering ηe→invisible (from K-shell) ≈ 0.024 ηe→invisible (from L-shell) [PLB 460

(1999) 236] and that the electron PEP-forbidden transitions give the same

experimental signal of electron disappearance for this electron’s decay

From ηe→invisible (K-shell) < 4.7 × 1030 s we can estimate an experimental

sensitivity for ηe→invisible (from L-shell) ≈ 1025 years

CNC processes are correlated to other fundamental questions, in particular

searches for invisible decays are related also with: extra-dimensions and Pauli

Exclusion Principle violation

Page 28: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

[S.L.Dubovsky, JHEP 01(2002)012]

Search for particle disappearance can constrain theoretical models with

extradimensions where particles are considered localized in a three-brane

world. In this scenario particles at low energy are described by the

eigenvalue: E=E0-iΓ/2 where Γ is a resonance which can be interpreted as a

four-dimensional metastable particle

Particles disappearance is due to tunneling from the three-brane world to the

extra-dimension. Γ depends on the number of extradimensions “n”

For electron disappearance considering k ≈ Planck mass ≈ 1019 GeV the best

available limit on ηe→nothing constrains the number of extradimension to n > 2

(ηe→nothing for n=3 is 9×1025 yr)

The estimated sensitivity on ηe→nothing could be used to give a more stringent

limit on the number of extradimensions

Perspectives for further CNC investigations with DAMA/LIBRA (2/2)

Page 29: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

Search for non-paulianelectronic transitions to L-shell

Accessible sensitivity with

DAMA/LIBRA ηe→invisible ≈ 1025 years

The lowering of the software energy

threshold of the experiment down to about 1

keV may give the possibility to investigate for

the first time processes involving Sodium K-

shell (≈1 keV)

Perspectives for PEP investigations with DAMA/LIBRA

Search for non-paulian electronic transitions to K-shellDAMA/LIBRA upgrade (2010)

• Replacement of all the PMTs with higher Q.E. ones

• Goal: lowering the energy thresholds

PLB 460 (1999) 236

Page 30: Pauli exclusion principle (PEP) violationpeople.roma2.infn.it/~dama/pdf/ect_dimarco.pdf · Pauli exclusion principle (PEP) violation The exclusion principle was postulated by Pauli

“If something in fundamental physics can be tested, then it absolutely must be tested“ [L.B. Okun]


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