Comenius University in Bratislava

Faculty of Mathematics, Physics and Informatics

Mgr. Rastislav Hodák

Presentation of the dissertation thesis

Charge–exchange reactions in the context of massive neutrinos

in nuclear processes

to obtain the academic Philosophiae doctor degree

in the study field:

4.1.5. Nuclear and Subnuclear Physics

Bratislava 2012

The dissertation thesis was performed during the full-time study at the

Department of Nuclear Physics and Biophysics.

Submitter: Mgr. Rastislav Hodák

Department of Nuclear Physics and Biophysics,

Faculty of Mathematics, Physics and Informatics,

Comenius University,

Mlynská dolina F1,

842 48 Bratislava 4, Slovakia

Supervisor: prof. RNDr. Fedor Šimkovic, CSc.

Opponents: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Defence of the dissertation thesis will be held on the . . . . . . . . . . . . . . . . . . . . . at

. . . . . . . . . . . . . hours with the dissertation committee in the field of the PhD.

study named by the chairman of committee on the . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Study field: 4.1.5. Nuclear and Subnuclear Physics

Study program: Nuclear and Subnuclear Physics

at the Faculty of Mathematics, Physics and Informatics, Comenius Univer-

sity, Mlynská dolina F1, 842 48 Bratislava 4, room number . . . . . . . . . .

Chairman of committee:

prof. RNDr. Jozef Masarik, DrSc.

Department of Nuclear Physics and Biophysics,Faculty of Mathematics, Physics and Informatics,

Comenius University,Mlynská dolina F1, 842 48 Bratislava 4

Contents

1 Introduction 1

2 Aims 1

3 Nuclear spin-isospin responses for solar neutrinos 3

4 Nuclear spin-isospin responses for double beta decay 3

5 Relation between the 0νββ and 2νββ nuclear matrix elements 5

6 Detection of relic neutrinos 7

7 Production of intense beta neutrino emitters at facility CERN-ISOLDE

for Beta beams 10

Summary 11

Résumé 12

List of publications 12

List of conferences and workshops 14

Bibliography 15

iii

1 Introduction

Neutrinos, as one of the most important and abundant structural constituents of the

Universe, are presently the main object of interest of particle and nuclear physics,

astrophysics and cosmology. Neutrino discovery and research had enormous impact

on the development of knowledge of the structure of matter and the fundamental

interaction governing the Universe.

The essential goals of this dissertation thesis deal with the study of fundamental

neutrino properties and their interactions with nuclei in nuclear weak processes. This

issue is investigated in the context of present and planned neutrino experiments by

taking advantage of nuclear charge-exchange reactions. In charge-exchange reactions,

a proton in a target nucleus is exchanged for a neutron in the projectile nucleus, or vice-

versa, thereby transferring charge between the target and the projectile. Although such

reactions are governed by the strong nuclear force, they are closely connected to electron

capture, β-decay and ββ-decay, which are transitions governed by the weak nuclear

force. Charge-exchange reactions are also very useful for probing specific properties of

nuclei, especially those related to spin and isospin and are, therefore, used to improve

and test our fundamental understanding of nuclear structure.

2 Aims

The main tasks of the dissertation thesis are as follows:

A. The nuclear charge-exchange reaction 71Ga(3He, t)71Ge will be exploited with the

objective to measure with high precision the Gamow-Teller transition strengths to

the three lowest-lying states in 71Ge, i.e. the ground state (1/2−), the 175 keV

(5/2−) and the 500 keV (3/2−) excited states at RCNP Osaka. These are the

states, which are populated via a charged current reaction induced by neutrinos

from terrestrial 51Cr and 37Ar sources. This experiments will provide input into

the calibration of the SAGE and GALLEX solar neutrino detectors and address a

long-standing discrepancy between the measured and evaluated capture rates from

the 51Cr and 37Ar neutrino calibration sources.

B. The GT− strength distribution in the reaction 130Te(3He, t)130I will be measured

with highest possible resolution. The GT− strength defines one of the two ”legs” for

the 2νββ-decay, but also enters into the dynamics of the 0νββ-decay. The nucleus130Te is ones of the key nuclei that are presently at the center of ββ-decay studies

in nuclear physics. The results of this experiment will therefore furnish important

information about the nuclear physics relevant for ββ-decay. This information will

1

directly feed into model calculations, which are aimed at describing reliably the

nuclear physics (i.e. the decay matrix elements) around both decay variants, the

2νββ-decay and the 0νββ-decay. One must note that the level of confidence with

which a neutrino mass can be extracted in case the 0νββ-decay is observed in one

of the present counting experiments like COBRA or CUORE will ultimately be

determined by these calculations.

C. The 0νββ-decay nuclear matrix elements (M0ν) are not observable in any measure-

ments. Thus, they might be obtained theoretically by clarifying relations between

their numerical values and other quantities known from experiments. The goal is

to describe theoretically such a relation between the dominant Gamow-Teller part,

M0νGT , of the NME governing the neutrinoless ββ-decay and the NME M2ν

cl of the

observed two neutrino ββ-decay evaluated in the closure approximation. Benefit

of M2νcl NME is the possibility of phenomenological determination from the experi-

mental study of the GT± transition strengths in nuclear charge-exchange reactions.

D. The standard Big Bang model predicts in average about 56 of relic (anti)neutrinos

per flavor in every cm3 all over the Universe. Their direct observation will provide

strong evidence supporting the modern cosmological explanation for the origin of

the Universe. A possibility to detect relic neutrinos via neutrino capture on β-

decaying (3H - KATRIN experiment, 187Re - MARE experiment) and ββ-decaying

(100Mo - NEMO3/SuperNEMO and MOON experiments) nuclei will be studied.

A question whether double relic neutrino capture on nuclei can be an obstacle for

observation of 0νββ-decay will be addressed. A subject of interest will be also a

detection of hypothetical heavy cosmic neutrinos, which can interact via active-

sterile fermions mixing. The capture rates for these processes will be derived and

the corresponding GT transitions will be determined phenomenologically.

E. Intense relativistic (anti)neutrino beams are another unique tool required to study

fundamental properties of neutrinos such as neutrino oscillation parameters, as well

as their Majorana or Dirac nature, the lepton number conservation hypothesis and

the absolute neutrino mass scale. Such beams originate from acceleration of β-

decaying radioactive ions (”Beta beams”). Neutrino scattering at low energies on

nuclei is essential for a variety of timely applications including also cosmological

neutrinos and furnishing a new constraint to ββ calculations. In this thesis the

conceptual design study of high power targets required for the production and

extraction of two baseline radioactive isotopes, 6He and 18Ne, to be accelerated at

Beta beam decay ring will be presented.

2

3 Nuclear spin-isospin responses for solar neutrinos

Two gallium experiments GALLEX (GALLium EXperiment) located at the Gran Sasso

Underground Laboratory (LNGS) in Italy and SAGE (Russian-American Gallium Ex-

periment) located at the Baksan Neutrino Observatory in the northern Caucasus moun-

tains of Russia, had the objective to measure the flux of the low-energy part of the

solar neutrino spectrum via the 71Ga(νe, e−)71Ge charged current (CC) reaction. Both

detectors, GALLEX and SAGE, confirmed the missing solar neutrino flux even for the

low-energy pp neutrinos. The most recent values of the solar neutrino rate reported

by the two collaborations are 67.6± 4.0 (stat.)± 3.2 (sys.) SNU (GALLEX combined

with its successor experiment GNO) and 65.4+3.1−3.0 SNU (SAGE) [1, 2].

As an additional proof and to exclude unknown systematic errors, the detectors were

calibrated separately by using two strong reactor-produced neutrino sources, 51Cr and37Ar, with precisely known fluxes. The 71Ga(3He, t)71Ge charge-exchange experiment

was performed at RCNP, Osaka University to extract with high precision the Gamow-

Teller (GT) transition strengths to the three lowest-lying states in 71Ge, i.e. the ground

state (1/2−), the 175 keV (5/2−) and the 500 keV (3/2−) excited states. These are the

relevant states, which are populated via charged-current reaction induced by neutrinos

from reactor-produced 51Cr and 37Ar sources.

Following Refs. [3, 4], the GT strength relates to the GT part of the cross section

at zero momentum transfer (q = 0) in the following way:

dσGT

dΩ(q = 0) =

(µπ

)2 pfpi

NστD |Jστ |2 B(GT ), (1)

where NστD is the distortion factor, the pi(pf ) is the incoming (outgoing) linear mo-

mentum of the projectile (ejectile) (pf/pi ≈ 1) and |Jστ | is the volume integral of theeffective nucleon–nucleon interaction of Love and Franey [5, 6]. The final GT strength

(B(GT)) values extracted in this way appear in Table 1.

A precise value of 7.2 ± 2.0% for this contribution from the excited states to the71Ga(νe, e

−)71Ge cross section has been evaluated, which exceeds the 5.1% value pre-

viously used by John Bahcall. Thus, the discrepancy observed in the SAGE and

GALLEX calibration data was further confirmed.

4 Nuclear spin-isospin responses for double beta

decay

The nuclear matrix element is an essential nuclear physics ingredient, for understanding

of the double beta (ββ) decay rate. The double beta decay (2νββ) with two neutrinos

3

Table 1: Various low-energy cross sections and B(GT) values for the 71Ga(3He, t)71Ge

reaction.

71Ge Jπ of dσ/dΩ dσ/dΩ % GT B(GT)

Eχ level (θ = 0) (q = 0) (×10−2)

[keV ] [mb/sr] [mb/sr]

g.s. 1/2− 0.777(9) 0.786(9) 92% 8.5240175 5/2− 0.070(4) 0.071(4) 40% 0.34(26)

500 3/2− 0.169(4) 0.171(4) 87% 1.76(14)

in the final state is an allowed second order weak process. The Gamow-Teller double

beta decay (M2νGT ) nuclear matrix element between the initial (0

g.s.i ) and final (0

g.s.f )

ground states is given by

M2νGT =

∑m

< 0g.s.f ∥∑k

σkτ+k ∥1+m >< 1+m∥

∑k

σkτ+k ∥0

g.s.i >

12Qββ(0

g.s.f ) + E(1+m)− E0

, (2)

where E(1+m)− E0 is the energy difference between the intermediate 1+m state and the

initial ground state and the sum∑

k runs over all the neutrons of the decaying nucleus.

The sum over m refers to all states in the intermediate nucleus, which are connected

to the double beta decay mother and daughter states via two ordinary beta decay

Gamow-Teller matrix elements.

Experimentally, these matrix elements can be accessed directly through (p, n) type

charge-exchange reactions, givingMm(GT−) and through the (n, p) type charge-exchange

reaction, giving Mm(GT+). For the Gamow-Teller double beta decay (M2νGT ) nuclear

matrix element can we write

M2νGT =

∑m

Mm(GT−) Mm(GT+)12Qββ(0

g.s.f ) + E(1+m)− E0

. (3)

The magnitude of these nuclear matrix elements can be derived from Gamow-Teller

transition strengths (B(GT )) via

|Mm(GT±)|2 = (2Ji + 1) Bm(GT±), (4)

where Ji is the total angular momentum of the initial state.

Charge-exchange studies are therefore an important tool capable of giving insight

into the details of the weak nuclear response. The high-resolution (3He, t) charge-

exchange experiment at 420 MeV on the double beta decaying nuclei 128Te and 130Te

was performed at RCNP, Osaka University to extract the GT strength distribution in

an attempt to further understand the nuclear matrix elements for the ββ-decay.

4

Table 2: Energies and spins of states populated in the 128Te(3He, t)128I and the130Te(3He, t)130I reactions. There are two tables side by side for each isotope. In

column one are quoted excitation energies and spins from Ref. [7]. Column three

lists the percentage of the cross section at q = 0 attributed to a GT transition. The

extracted B(GT−) values are listed in column four.

128I 130I

Ex (Ref. [7]) Jπ Ex Jπ GT % B(GT−) Ex (Ref. [7]) Jπ Ex Jπ GT % B(GT−)

[keV ] [keV ] [keV ] [keV ]

0.0 1+ 0 1+ 84 0.079(8) 43.3 (1− 4)+ 43 1+ 80 0.072(9)

133.6 2− 134 2− 0 - 224.0 3+ 224 3+ 0 -

220.9 1+, 2+, 3+ 221 1+ 73 0.021(4) 353.7 (2− 5)− 354 2− 0 -

426.3 1+, 3+ 426 1+ 71 0.020(5) 485 1+ 86 0.073(6)

639 1+ 74 0.057(10) 680 1+ 57 0.027(11)

1037 2− 0 - 768.4 (2− 5)− 768 2− 0 -

1153 1+ 69 0.084(19) 843 1+ 73 0.027(5)

1222 1+ 79 0.121(16) 977 1+ 83 0.038(4)

1373 1+ 52 0.022(11) 1101 1+ 69 0.062(14)

1437 1+ 63 0.020(6) 1216 1+ 65 0.047(13)

1478 1+ 58 0.018(7) 1342 1+ 70 0.043(10)

1548 1+ 65 0.022(6) 1476 1+ 78 0.067(10)

1607 1+ 40 0.011(8) 1600 1+ 60 0.039(14)

Σ = 0.829(50) Σ = 0.746(45)

The extraction of the GT strength from the GT part of the cross section follows

the recipe according to Eq. (1). The B(GT−) values for the isolated states are listed

in Table 2 for both nuclei, 128Te and 130Te.

The GT distributions for the two reactions were found to be qualitatively similar.

Deduced from the presently accepted ββ-decay half-lives, the decay of 128Te is enhanced

by a factor of two over its neighbor 130Te, due to the larger nuclear matrix element.

However, this experiment does not exhibit a significant difference between the B(GT−)

distributions.

5 Relation between the 0νββ and 2νββ nuclear

matrix elements

Observing the 0νββ-decay would tell us that the total lepton number is not a con-

served quantity, and that neutrinos are massive Majorana fermions. Answering these

questions is obviously a crucial part of the search for the “Physics Beyond the Standard

Model”. Consequently, experimental searches for the 0νββ-decay, of ever increasing

sensitivity, are pursued worldwide (for a recent review of the field, see e.g. [8]). How-

5

ever, interpreting existing results as a determination of the neutrino effective mass,

and planning new experiments, is impossible without the knowledge of the correspond-

ing nuclear matrix elements. Their determination, and a realistic estimate of their

uncertainty, are therefore an important part of the problem.

The nuclear matrix elements M0ν for the 0νββ-decay must be evaluated using

tools of nuclear structure theory. Unfortunately, there are no observable that could be

simply and directly linked to the magnitude of 0νββ nuclear matrix elements and that

could be used to determine them in an essentially model independent way. Here, a

novel relation between the dominant Gamow-Teller part, M0νGT , of the NME governing

the neutrinoless ββ-decay and the NME M2νcl of the observed two neutrino ββ-decay

evaluated in the closure approximation is discussed.

The relation is based on the evaluation of the auxiliary functions C0νGT (r) and C

2νcl (r)

that describe the dependence of the corresponding nuclear matrix elements on the

distance r between the pair of neutrons that is transformed in the ββ-decay into a pair

of protons. Thus expressions

M0νGT =

∫ ∞

0

C0νGT (r)dr, M2ν

cl =

∫ ∞

0

C2νcl (r)dr,

and

C0νGT (r) = H(r, E)× C2ν

cl (r), (5)

with neutrino potential H(r, E) represents the required relation.

However, while the matrix elements M2ν and M2νcl depend only on the transition

strengths and energies of the 1+ virtual intermediate states (they are pure GT quan-

tities), the function C2νcl (r) gets contribution from all multipoles. Thus, the relation

that has been found is an indirect one; even if M2νcl would be precisely known, the

evaluation of the function C2νcl (r) requires additional nuclear theory input.

While the nuclear matrix elementsM2ν are simply related to the 2νββ half-life T 2ν1/2,

and are therefore known for the nuclei in which T 2ν1/2 has been measured, the closure

matrix elements M2νcl need be determined separately. There are several ways how to

accomplish this task:

(i) Rely on a nuclear model (e.g. QRPA or nuclear shell model), adjust parameters

in such a way that the experimental value of M2ν is correctly reproduced, and

use the model to evaluate M2νcl .

(ii) Use the measured GT− and GT+ strength functions and assume coherence (i.e.

same signs) among states with noticeable strengths in both channels. In this way

an upper limit of M2νcl can be obtained.

6

Table 3: The 2νββ-decay closure nuclear matrix element |M2νcl | evaluated using the

Single State Dominance hypothesis (SSD) and with help of the measuredGT± strengths

in charge-exchange reactions (ChERs). The adopted values of the 2νββ-decay half-lives

T 2ν−exp1/2 , taken from Ref. [9] are also shown.

SSD ChER

Nucleus T 2ν−exp1/2 [y] |M2ν | [MeV −1] |M2ν

cl | |M2ν | [MeV −1] |M2νcl |

48Ca 4.4× 1019 - - 0.083 0.220 [10]

76Ge 1.5× 1021 - - 0.159 0.522 [11]

96Zr 2.3× 1019 - - - 0.222 [12]

100Mo 7.1× 1018 0.208 0.350 [13] - -

116Cd 2.8× 1019 0.187 0.349 [13] 0.064 0.305 [14]

128Te 1.9× 1024 0.019 0.0327 [13] - -

(iii) Finally, one could invoke the so called “Single State Dominance hypothesis” [15]

according to which the sum in

M2ν =∑m

⟨f ||στ+||m⟩⟨m||στ+||i⟩Em − (Mi +Mf )/2

, (6)

is exhausted by its first term. The measured β-decay and EC ft values then

make it possible to determine both the M2ν and M2νcl .

Obviously, none of these methods is exact, but their combination has, perhaps, a

chance of constraining the value of M2νcl substantially. Examples of application of the

latter two items are shown in Table 3. That method can be used, obviously, only for

the nuclei where the corresponding experimental data are available.

Until this discrepancy is resolved, it is difficult to employ M2νcl in order to constrain

the magnitude of the 0νββ matrix elements M0νGT .

6 Detection of relic neutrinos

Fundamental particles as relic neutrinos are an essential ingredient of the standard Big

Bang Model - the best present description of our Universe. This model predicts in

average about 56 of relic (anti)neutrinos per flavor in every cm3 all over the Universe

[16]. Their direct observation will provide strong evidence supporting the modern

cosmological explanation for the origin of the Universe.

7

It has been carried out a detailed analysis of nuclear physics and kinematical as-

pects of single nuclear β-decay and relic neutrino capture on β-radioactive nuclei. We

focussed on 3H and 187Re isotopes to be used in the forthcoming KATRIN [17] and in

the planned MARE [18] experiments, respectively.

The KATRIN experiment, dedicated to the measurement of electron neutrino mass

from endpoint electron energy spectrum of β-decay of tritium, can, in principle, also

search for cosmic neutrinos via neutrino capture reaction

νe +3 H((1/2)+) →3 He((1/2)+) + e−. (7)

This experiment (in construction phase) aims to measure mν with sensitivity of 0.2 eV

using about 50 µg of tritium corresponding to 5× 1018 T2 molecules. For this amount

of target nuclei, it has been found the number of neutrino capture events

Nνcapt(KATRIN) ≈ 4.2× 10−6 ην

⟨ην⟩yrs−1. (8)

The MARE project will investigate the β-decay of 187Re with absorbers of metallic

rhenium or AgReO4. In this case the neutrino capture reaction

νe +187 Re((5/2)+) → 187Os((1/2)−) + e− , (9)

is considered. This experiment foresees a 760 grams bolometer. For this amount of

rhenium the number of neutrino capture events is

Nνcapt(MARE) ≃ 6.7× 10−8 ην

⟨ην⟩yrs−1. (10)

One can see that with both 3H and 187Re target nuclei the relic neutrino capture

rate event numbers are extremely small and unobservable in the present and near future

experiments. Even taking into account the gravitational clustering of relic neutrinos

at the level of ην/⟨ην⟩ ≃ 103− 104 [19] can hardly change this conclusion. However, we

noted that scaling MARE experiment up to several hundreds of kilograms of rhenium

would offer an event rate significantly larger than in KATRIN experiment.

A new generation of 2νββ-decay detectors with radioactive material at the ton scale

are under considerations and construction, e.g. MOON (100Mo) [20] and others [21].

There is a question whether due to a large amount of target isotope the relic neutrino

induced double beta decay (νββν) on nuclei,

νe + (A,Z) → (A,Z + 2) + 2e− + νe, (11)

can be observed. The main objective of the above mentioned experiments is searching

for 0νββ-decay. In the presence of the relic neutrino background there may appear

8

Table 4: The number of heavy neutrino capture events for three different reactions and

a given amount of the daughter isotope. Three different masses of heavy neutrino mh

are considered. Etresh. is the threshold energy of the reaction, B(A,Z) is the strength

of the allowed beta transition and |Ueh| is a mixing matrix.

Nuclear Etresh. Mass B(A,Z) Nνh/(|Ueh|2. ην⟨ην⟩).[yrs

−1]

transition [MeV] [kg] mh = 1 MeV mh = 5 MeV mh = 10 MeV3He →3 H 1.04 1 5.65 - 1.5× 104 7.3× 104

106Cd →106 Ag 1.22 10 < 2.34 - < 7.0× 102 < 3.5× 103

100Mo →100 Tc 0.19 10 1.05 1.3× 102 4.1× 104 1.6× 104

a legal question if they can mimic 0νββ-decay by lepton number conserving double

neutrino capture (ννββ) on nuclei

2νe + (A,Z) → (A,Z + 2) + 2e−. (12)

As an example we consider the MOON detector with 1 ton of 100Mo [20]. For the

number of single N ννcapt and double N

ννcapt relic neutrino capture events we get

Nννcapt(MOON) ≃ 8.8× 10−20 ην

⟨ην⟩yrs−1

Nννcapt(MOON) ≃ 1.0× 10−48

(ην⟨ην⟩

)2

yrs−1. (13)

Thus, the relic neutrino induced double beta decay processes presented in Eqs. (11)

and (12) are not observable in the future generation of the double β-decay experiments.

Further, the possibility of detection of the heavy cosmic sterile neutrinos was ad-

dressed. The sterile neutrinos would be a significant ingredient for our understanding

of the origin of neutrino masses and mixing. The heavy sterile Majorana neutrino νh

with sufficiently large mass can induce the inverse nuclear β-decays on stable isotope

(A,Z),νh + (A,Z) → (A,Z ∓ 1) + e±, (14)

for which the single β-decay is forbidden energetically. As an example we consider

heavy neutrino induced β-decays of three different isotopes: 3He(1/2+) → 3H(1/2+),106Cd(0+) → 106Ag(1+) accompanied by emission of positron and 100Mo(0+) → 100Tc(1+)

with emission of an electron. We found that experiments with a sufficient amount of

detector material may have a chance to detect the heavy cosmic neutrino signals (see

Table 4).

9

Neutrino

Source

Decay

Ring

Ion production

ISOL target &

Ion source

Proton Driver

SPL

SPS

Acceleration to

medium energy

Bunching ring

and RCS

PS

Acceleration to final energy

PS & SPS

Experiment

Ion acceleration

Linac

Beam preparation

ECR pulsed

Experiment

Figure 1: Schematic layout of a possible Beta beams facility proposed at CERN.

7 Production of intense beta neutrino emitters at

facility CERN-ISOLDE for Beta beams

The Beta beams were proposed by Piero Zucchelli in 2002 [22]. This is a concept of a

large scale facility, based on existing CERN accelerators, aiming to provide pure and

collimated ultra-relativistic beams of electron (anti)neutrinos with help of accelerated

β-decaying radioactive ions circulating in a storage decay ring (see Fig. 1 [22]). This

type of intense source of electron (anti)neutrinos directed towards a remote under-

ground neutrino detector [23] with a dramatic increase of the interaction cross section

in the detector is planned to be used for a measurement of νe → νµ oscillations, offer-

ing a unique chance for establishing a value of the θ13 mixing angle and CP violating

phase [24]. Following Refs. [25, 26] consider low-energy Beta beams as a tool to study

the isospin and spin–isospin nuclear response. They proposed to use charged current

neutrino–nucleus interactions as a supplementary probe of the many virtual transitions

involved in 0νββ-decay.

An important part of the feasibility study of the Beta beams is dedicated to the

ion production, which would allow the production of intense (anti)neutrino fluxes for

physical experiments.

10

In this contribution the progress concerning the conceptual design study of high

power targets needed for the production and extraction of two baseline isotopes (6He

and 18Ne) used for Beta beams project is reviewed. An effective approach for the

production and extraction of the short-lived radionuclide 6He in yet unmatched yields,

using the so-called Isotope Separation On Line (ISOL) method at the ISOLDE facility

(CERN) is presented. The production of the baseline β− emitter 6He is achieved with

fast neutrons on a thick beryllium oxide target with the 9Be(n, α)6He reaction. On-

line experimental data confirmed that the required production rates of 6He isotopes

for antineutrino beams is feasible [27]. The proposed concept of 18Ne production with

target based on circulating sodium fluorine salts needs validation by a precise deter-

mination of the reaction cross-sections and by prototyping the loop to obtain relevant

operating parameters and efficiencies. Approved experimental program scheduled for

static molten salt unit at CERN-ISOLDE is planned for the production and release of18Ne including systematic experimental study of physical characteristics of the NaF

molten salt (Ne diffusion, viscosity, surface tension, etc.).

Summary

A realistic description of neutrino-nucleus interactions at low- and intermediate-energy

region is important for the interpretation of measurements by many neutrino experi-

ments. The understanding of their sensitivity to neutrino properties, evaluation of the

neutrino fluxes and spectra depend on the accuracy to which the neutrino-nucleus cross

sections are known. The Gamow-Teller transitions dominates the fundamental weak

nuclear processes at low energies with massive neutrinos like electron capture, single

beta decay, double beta decay and scattering of neutrinos on nuclei. In this thesis

charge-exchange nuclear reactions, in which a proton in one nucleus is exchanged for

a neutron in the other nucleus during a fast collision, were used to provide a unique

insight into Gamow-Teller transitions associated with these weak nuclear processes.

The charge-exchange experiments were realized at RCNP Osaka in collaboration with

University of Muenster. Subject of interest were problems related with scattering of

neutrinos on 71Ga (SAGE and GALLEX experiments), double beta decay of 128,130Te

(CUORE experiment), a possible relation between the 2νββ-decay and 0νββ-decay

nuclear matrix elements in view of measurement of involved Gamow-Teller transitions,

capture of relic neutrinos on single beta (KATRIN and MARE experiments) and double

beta (NEMO3/SuperNEMO and MOON experiments) decaying nuclei as well as the

concept of Beta beams, which might allow to investigate even Gamow-Teller forbidden

transitions in future.

11

Résumé

Realistický opis interakcie neutrín s jadrami v oblasti nízkych a stredných energií

je dôležitý pri fyzikálnej interpretácií výsledkov rôznych neutrínových experimentov.

Pochopenie citlivosti dát vzhľadom na vlastnosti neutrín, ako aj kalkulácia tokov a

spektier neutrín závisia od presnosti popisu účinných prierezov interakcií neutrín s

jadrami. Gamow-Tellerovské prechody dominujú v oblasti nízkych energií v rámci

fundamentálnych slabých jadrových procesov s hmotnými neutrínami, medzi ktoré pa-

tria napr. elektrónový záchyt, beta rozpad, dvojitý beta rozpad a rozptyl neutrín

na jadrách. V tejto dizertačnej práci boli študované nábojovo-výmenné reakcie, pri

ktorých počas rýchlych zrážok je protón z jedného jadra vymenený za neutrón z druhého

jadra, poskytujúce nahliadnutie do GT prechodov súvisiacich so slabými jadrovými

procesmi. Nábojovo-výmenné experimenty boli zrealizované v zariadení RCNP Osaka

v kolaborácii s Univerzitou v Muensteri. Predmetom záujmu boli problémy spojené s

rozptylom neutrín na jadre 71Ga (SAGE a GALLEX experimenty), dvojitý beta rozpad

jadier 128,130Te (CUORE experiment), vzťah medzi jadrovými maticovými elementmi

2νββ-rozpadu a 0νββ-rozpadu vzhľadom na merania GT prechodov, záchyt relikt-

ných neutrín na β- (KATRIN a MARE experimenty) a ββ- (NEMO3/SuperNEMO

a MOON experimenty) rozpadajúcich sa jadrách, ako aj koncept Beta zväzkov, ktoré

nám umožnia v budúcnosti preskúmať aj zakázané GT prechody.

List of publications

I. T. Stora et al. (2012):

A high intensity 6He beam for the β-beam neutrino oscillation facility:

European Physics Letters, Volume 98, Issue 3, Art. No. 32001.

II. D. Frekers et al. (2011):

The 71Ga(3He, t) reaction and the low-energy neutrino response:

Physics Letters B, Volume 706, Issues 2–3, Pages 134–138.

Cited by: Abazajian, K.N. et al., arXiv:1204.5379v1 [hep-ph] (2012).

III. R. Hodák, T. Stora and T. M. Mendonca (2011):

Production of high intensity Beta beams at the ISOLDE facility:

Workshop on Calculation of Double-Beta-Decay Matrix Elements (MEDEX’11):

American Institute of Physics Conference Proceedings, Volume 1417, Pages 52-56.

IV. R. Hodák and T. Stora (2011):

Production of high intensity Beta Beams at the ISOLDE facility (Extended

12

Abstract):

Student Science Conference, FMFI UK, Bratislava, Page 212.

V. F. Šimkovic, R. Hodák, A. Faessler and P. Vogel (2011):

Relation between the 0νββ and 2νββ nuclear matrix elements reexamined:

Physical Review C, Volume 83, Issue 1, Art. No. 015502.

Cited by: Zuber, K., arXiv:1201.4665 [nucl-ex] (2012).

VI. A. Faessler, R. Hodák, S. Kovalenko and F. Šimkovic (2011):

Tritium and rhenium as a probe of cosmic neutrino background:

Journal of Physics G: Nuclear and Particle Physics, Volume 38, Number 7, Art.

No. 075202.

Cited by: Alikhanov, I., arXiv:1204.4396 [astro-ph.CO] (2012);

Li, Y.F. et al., JCAP 1108, 006 (2011);

Li, Y.F. et al., Phys.Lett. B 698, 430-437 (2011).

VII. R. Hodák, F. Šimkovic, S. Kovalenko and A. Faessler (2011):

Towards the detection of light and heavy relic neutrinos:

Progress in Particle and Nuclear Physics, Volume 66, Issue 2, Pages 452–456.

VIII. R. Hodák (2010):

Capturing relic neutrinos with β- and double β-decaying nuclei (Extended Ab-

stract):

Student Science Conference, FMFI UK, Bratislava, Page 280.

IX. M. G. Saint-Laurent et al. (2009):

Comparison Of Expected Yields For Light Radioactive Beams At SPIRAL-1

And 2:

International Symposium on Exotic Nuclei (EXON):

American Institute of Physics Conference Proceedings, Volume 1224, Pages 482-

491.

X. R. Hodák, S. Kovalenko and F. Šimkovic (2009):

Capturing relic neutrinos with β- and double β-decaying nuclei:

Workshop on Calculation of Double-Beta-Decay Matrix Elements (MEDEX’09):

American Institute of Physics Conference Proceedings, Volume 1180, Pages 50-54.

XI. T. M. Mendonca, R. Hodák and T. Stora (2012):

Opportunities for neutrino experiments at ISOLDE:

NuFact’11, XIIIth International Workshop on Neutrino Factories, Superbeams

and Beta-beams, CERN and University of Geneva:

Submitted to IOP conference series.

13

XII. P. Puppe et al. (2012):

High resolution (3He, t) reaction on the double beta decaying nuclei 128Te and130Te:

To be published in Phys. Rev. C.

List of conferences and workshops

i. Poster session on the occasion of 50th anniversary of Department of Nuclear Physics

(1961-2011), FMFI Comenius University, Bratislava, Slovakia, 7. December, 2011.

”Production of intense beta neutrino emitters at CERN-ISOLDE for Beta beams”;

”Study of charge - exchange reactions at RCNP Osaka”.

ii. ”Production of high intensity Beta beams at the ISOLDE facility (25 min)”,

MEDEX’11, Prague, Czech Republic, 13. - 16. June, 2011.

iii. ”Conceptual design of a molten sodium salt loop target for neutrino production

for the beta-beams (25 min)”, The 4th High Power Targetry Workshop, Malmo,

Sweden, 2. - 6. May, 2011.

iv. ”Production of high intensity Beta beams at the ISOLDE facility (20 min)”, Stu-

dent Science Conference, FMFI, Comenius University, Bratislava, 19. April, 2011.

v. ”Towards the detection of relic neutrinos (35 min)”, International School of Nuclear

Physics, 32nd Course - Particle and Nuclear Astrophysics, Erice, Italy, 16 .- 24.

September, 2010.

vi. ”Capturing relic neutrinos with β- and double β-decaying nuclei (20 min)”, Student

Science Conference, FMFI, Comenius University, Bratislava, 28. April, 2010.

vii. ”Detection of Big Bang relic neutrinos (25 min)”, 11th Small Triangle Meeting,

Kysak, Slovak Republic, 20. - 23. September, 2009.

viii. ”Capturing relic neutrinos with beta and double beta decays (25 min)”, MEDEX’09,

Prague, Czech Republic, 15. - 19. June, 2009.

14

Bibliography

[1] F. Kaether et al., Phys. Lett. B 685, 47 (2010).

[2] J. Abdurashitov, Phys. Rev. C 80, 015807 (2009).

[3] T. Taddeucci et al., Nucl. Phys. A 469, 125 (1987).

[4] C. Goodman et al., Phys. Rev. Lett. 44, 1755 (1980).

[5] W. Love and M. Franey, Phys. Rev. C 24, 1073 (1981).

[6] M. Franey and W. Love, Phys. Rev. C 31, 488 (1985).

[7] Brookhaven National Laboratory, National Nuclear Data Center (2012), URL

http://www.nndc.bnl.gov.

[8] F. T. Avignone, S. R. Elliott, and J. Engel, Rev. Mod. Phys. 80, 481 (2008).

[9] A. S. Barabash, Phys. Rev. C 81, 035501 (2010).

[10] K. Yako et al., Phys. Rev. Lett. 103, 012503 (2009).

[11] E. W. Grewe et al., Phys. Rev. C 78, 044301 (2008).

[12] H. Dohmann et al., Phys. Rev. C 78, 041602R (2008).

[13] P. Domin, S. G. Kovalenko, F. Šimkovic, and S. V. Semenov, Nucl. Phys. A 753,

337 (2005).

[14] S. Rakers et al., Phys. Rev. C 71, 054313 (2005).

[15] J. Abad, A. Morales, R. Nunez-Lagos, and A. Pacheco, Ann. Fiz. A 80, 9 (1984).

[16] C. Giunti and C. Kim, Fundamentals of Neutrino Physics and Astrophysics (Ox-

ford U. Press, 2007).

[17] A. Osipowicz et al. (KATRIN Collaboration) (2001), arXiv: 0109033v1 [hep-ex].

15

[18] E. Andreotti et al. (MARE Collaboration), Nucl. Instrum. Meth. A 572, 208

(2007).

[19] R. Lazauskas, P. Vogel, and C. Volpe, J. Phys. G: Nucl. Part. Phys. 35, 025001

(2008).

[20] H. Ejiri, Mod. Phys. Lett. A 22, 1277 (2007).

[21] F. Avignone, S. Elliott, and J. Engel, Rev. Mod. Phys 80, 481 (2008).

[22] P. Zucchelli, Phys. Lett. B 532, 166 (2002).

[23] C. Orme (2010), arXiv: 1004.0939v1 [hep-ph].

[24] C. Volpe, Prog. Part. Nucl. Phys. 64, 325 (2010).

[25] C. Volpe, J. Phys. G 31, 903 (2005).

[26] R. Lazauskas and C. Volpe, Nucl. Phys. A 792, 219 (2007).

[27] T. Stora, in Proceedings of the Workshop European Strategy for Future Neutrino

Physics, edited by A. Blondel and F. Dufour (CERN, Geneva, 2009), p. 110.

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