Download The theme “Research of fundamental interactions in nucleus at low

ABSTRACT
V. B. Brudanin, A. Kovalik
The new theme “Non-accelerator neutrino physics and astrophysics” beginning at JINR from
2010 includes the following projects and directions of research:
I. Neutrino physics
1) Project NEMO. Design and construction of the NEMO-3 spectrometer, which took
about five years, was finished in 2003. The NEMO-3 detector is intended for studying double
beta-decay of nuclei available in rather large quantities (a few kg). The spectrometer installed in
the Modane underground laboratory (LSM, tunnel Frejus, France) contains almost two thousand
plastic scintillators, a track-sensitive volume consisting of 6180 drift cells, composite passive
shielding and allows investigation of samples with mass up to 10 kg. A set of currently installed
and simultaneously investigated sources includes 7 kg of the enriched 100Mo isotope, 1 kg of 82Se,
0.6 kg of 116Cd, 0.7 kg of 130Te, and some other isotopes with smaller mass (96Zr, 48Ca, 150Nd).
Setting-up operations have been finished and data acquisition is in progress now.
During the nearest five years it is supposed to carry out measurement (permanent data
taking) of 2-decay of samples installed in the NEMO-3 spectrometer. It is expected to obtain
the upper limit on existence of neutrinoless 2-decay in 100Mo at a level of ~ 1025 years, which
corresponds to the effective Majorana neutrino mass ~ 0.1–0.3 eV. It is supposed that after
accomplishment of data taking in the NEMO-3 experiment construction of a new-generation
spectrometer SuperNEMO will be started. With this setup it is planned to reach a new level of
sensitivity to the effective Majorana neutrino mass at a level of ~ 0.01 eV.
2) Project TGV. The low-background highly efficient TGV spectrometer has been
constructed from radioactively pure materials for studying rare nuclear processes — 22 and
20 decay of 48Ca as well as 2K2 and 2K0 capture in 106Cd. The basic elements of the
spectrometer are 32 planar HPGe detectors of total sensitive volume about 400 cm3 (3 kg of
germanium approximately), a cryogenic system, an electronic data acquisition system and a
system of active and passive shielding for suppression of various components of a natural
radioactive background. The spectrometer is assembled in the Modane underground laboratory
(LSM, 4800 m.w.e., tunnel Frejus, France), and search for 2K2 and 2K0 capture in 106Cd is
now under way at. An enriched 48Ca sample is purified from radioactive contaminations. The
technique of production of thin (50–100 mg/cm2) calcium foils with homogeneous surface is
developed using a method of pressing. New limits on ordinary beta-decay of 48Ca and on double
beta-decay of 48Ca to excited states of the daughter nucleus are obtained.
During the nearest two years it is supposed to perform measurement of double beta-decay
of 48Ca. Exposition of 10 g of 48Ca in the TGV spectrometer will allow us to improve the current
double beta-decay estimates for this nucleus by several-fold. Investigation with 106Cd is carried
out for the first time. It will be the first direct measurement of 2K2 and 2K0 capture. The first
estimates of this process are expected at a level of 1019–1021 years.
The sensitivity to the effective Majorana neutrino mass at a level 0.2–0.1 eV will be
reached as a result of studies within the framework of the NEMO and TGV projects.
Project G&M (GERDA–MAJORANA) A further stage in search for neutrinoless double
beta-decay is participation of DLNP in new-generation experiments GERDA and MAJORANA
with the sensitivity to the effective Majorana neutrino mass at a level of 0.01 eV and better. The
first phase of the project was started in 2009. DLNP carries out R&D and production of muon
veto system for GERDA and MAJORANA experiments, takes part in testing and tuning of 76Ge
detectors, participates in design and assembling of the GERDA test facility. The prototype
detector for the MAJORANA experiment was made from 76Ge provided by DLNP.
3) Project GEMMA. Measurement of the magnetic moment of the antineutrino (project
GEMMA) is carried out at the reactor of the Kalininskaya atomic power plant. In 2011 it is
planned to reach a sensitivity at a level of 1.2∙1011 μB, which exceeds sensitivities of modern
experiments by an order of magnitude. The GEMMA experimental setup was installed at the
reactor in 2004. Measurements started in the middle of 2005. A sensitivity level of 3.9∙1011 μB
has been reached recently (Oktober 2008), which already exceeds the sensitivity of current
experiments (1.0∙1010 μB ).
II. Astrophysics
4) EDELWEISS-II project
A Search for Cold Dark Matter with Cryogenic Detectors at Frejus Underground
Laboratory
Analysis of recent experimental data on the cosmic microwave background, combined
with other astronomical and astrophysical data, gives undoubted evidence that Universe
comprise non-luminous, nonbaryonic matter. Cosmological data indicate that only 5% of the
mass in the Universe are accounted for by ordinary substance and another <2% by neutrinos. The
unknown rest composition is dark energy (65–70%) and dark matter (about 25%). A direct
observation of the interaction of dark matter particles in a terrestrial detector would be of
tremendous importance to particle physics and cosmology.
The French-German-Russian experiment EDELWEISS (Expérience pour DEtecter Les
Wimps En Site Souterrain) is dedicated to the direct detection of non-baryonic cold dark matter
in the form of WIMPs trapped in the Galactic halo. To reject background caused by cosmic
radiation the experiment is located in underground laboratory, Laboratoire Souterrain de Modane
(LSM), in the Frejus tunnel between France and Italy. 1800 m rock overburden corresponding to
a depth of 4800 mwe reduces see-level muons’ flux by 6 orders and neutrons’ flux by 4 orders.
The direct detection principle consists in the measurement of the energy released by nuclear
recoils produced in an ordinary matter target by elastic collisions of WIMPs. EDELWEISS uses
high purity Germanium cryogenic detectors with simultaneous measurement of phonon and
ionization signals at a temperature about 20 mK. Recoiled nucleus produces less ionization in a
crystal than an electron does, thus analysis of phonon/ionization ratio allowing an excellent
event-by-event discrimination between nuclear recoils (induced by WIMP or neutron scattering)
and electron recoils induced by natural radioactivity. The main constraints are the extremely low
event rate (< 1 evt/kg/year) and relatively small expected WIMP-deposited energy (<100 keV).
EDELWEISS was initially been funded for a 28 detectors stage with total weight of
detectors about 10 kg. Data is acquired starting from the 2007 year summer with such a setup.
All parameters of the EDELWEISS-II have been validated in 2006-2007 with calibration
(gamma and neutron) and low energy background commissioning runs (in 2006 and beginning of
2007 only 9 detectors were used).
At EDELWEISS-II experiment next years low backgrounds physics runs will be
continued with 10 kg setup with the aim to reach sensitivity to WIMP-nucleon cross-section of
10-7 pb or better for a WIMP mass of 100 GeV. 40 additional detectors with total weight at ~15
kg (Ge/NbSi and Ge/NTD/INTERDIGIT) will be added in the two coming years to enhance
progressively the sensitivity to WIMP detection. The aim is to have to 2012 year 3500
kg(fiducial mass).d with no background events at nuclear recoil band above 15 keV threshold.
This will provide the sensitivity on the 4x10-9 pb level in successful competition with other
world leading dark matter search experiments (Xe, Ar based, and CDMS). Data analysis and
sensitivity of EDELWEISS-II will be achieved by consideration of nuclear recoil band only
(main method); but also by analysis of background changes with time, in order for search of
indirect signature of WIMPs (this will be defined by stability of background conditions). In next
few years EDELWEISS-II has excellent opportunities on most technical subgroups, most
notably new ID detectors.
Further development of EDELWEISS-II will be continued in the project called
“EURECA” (European Underground Rare Event Calorimeter Array), which will unite
EDELWEISS, CRESST and the Spanish-French experiment ROSEBUD. The aim is to explore
scalar cross sections in the 10−9 – 10−10 picobarn region with a target mass of up to one tone. This
will cover almost all predictions of SUSY models. A major advantage of EURECA is our
planned use of more that just one target material (multi target experiment for WIMP
identification). In preparation for this large-scale experiment, R&D for EURECA is provided
through the current phases of CRESST and EDELWEISS. EURECA plans to start as an
executable project at ~2010 and achieve the desired target not early than 2015. The design of the
cryogenic and shielding infrastructure requires detailed studies and careful planning. EURECA
will require significant improvements in the radiopurity of the immediate environment to achieve
the very low background rate required. This concerns gamma ray background and neutroninduced background.
Main participation of JINR in both EURECA and EDELWEISS projects will be continuous
providing of expertise on background connected problems as well conducting of measurements
of backgrounds and selection of radio-pure materials (which are needed for new detectors:
supports, cables, electronic circuits, etc). We will continue study of neutrons and radon
contamination at deep underground site. One of the tasks will be development and building of a
compact mobile high sensitive radon detector with the sensitivity on a level 100 mBq/m3 and
with gas vessel volume at few litters. Such a detector can provide significantly faster
measurements of radon levels with respect of that with commercially available radon detectors.
Availability of such equipment has high demand in the EDELWEISS project. Dubna group will
take deep involvement in WIMP data analysis and MC of detectors. JINR group is also
responsible for conducting of calibration of EDELWEISS-II project with radioactive neutron and
gamma sources.
5)Project “LESI”
“Study of interactions between light nuclei in the astrophysical energy region"
The aim of these investigations: measurement of astrophysical S-factors and effective cross
sections of the pd, dd - reactions in the astrophysical energy region 2-15 keV
The investigation of the reactions between light nuclei
pd3He +  (5.5 MeV), (1)
dd3He + n (2.5 MeV), (2)
in the ultralow energy region is of great importance for physics of few-body nucleon systems
because it could provide direct verification of fundamental symmetries in strong interactions,
such as charge symmetry, isotopic invariance, exchange of the meson currents, effect of nuclear
screening, etc. It could also help to solve a number of astrophysical problems.
The investigation of the pd- and dd-reactions could help to understand the process of
primordial nucleosynthesis in the stars. The measurement of the cross sections for reactions
between light nuclei in the stars at ultralow energies is very important for testing the models of
stars dynamics and evolution. Obtaining information on the size of electron screening of
interacting nuclei can help to explain the existing deficit of light nuclei (except 4He) in stars and
the Galaxy to test applicability of the standard model to the description of all processes occurring
in the Sun.
In 2010 - 2012 researches of following reactions will be carried out:
dd → 3He + n; dd → t + p
2010
The aim: research of the dependence of the astrophysical S-factor and the dd-reaction crosssection on the deuteron collision energy in the region of 2-8 keV; determination of the
contribution to the dd-reaction cross-section due to the electron screening effect of the
interacting deuterons in metal deuterides.
1. Modernization of the Hall accelerator: increase in a total ion current with conservation of
energy distribution of accelerated ion flux; reduction of the beam divergence of
accelerated ions. Formation of an ion beam in a frequency mode with a pulse repetition
rate of ~1 Hz.
2. Development and creation of ZrD, ZrD2, Ta2D, TiD2 targets by reactive magnetron
sputtering.
3. Development and creation of a technique of measurement of deuteron distribution in
depth of targets using the ERD method (experiments on Van de Graaf accelerator) and
the method of the target surface research by means of the Auger-spectrometer.
4. Development and construction of an annular semiconductor silicon detector for
registration of protons and tritons generated in the dd-reaction.
5. Carrying out of experiments using the Auger-spectrometer and the ERD method to
inspect the target surface and to measure the deuterium distribution in depth of the target
before and after the dd-experiment.
6. Investigations of the dd-reactions in the region of ultralow energies of deuteron collisions
of 2-8 keV using the Hall accelerator and the created deuterated metal targets.
7. Preparation of research results for publication.
2011
The aim: measurement of the values of the astrophysical S-factor and the pd-reaction crosssection in the region of ultralow energies of proton-deuteron collisions of 2-10 keV;
determination of the contribution to the pd-reaction cross-section due to the electron screening
effect of the interacting protons with deuterons in metal deuterides.
1. Obtaining of intense beams of accelerated protons in the energy region of 3-15 keV with
the use of the Hall accelerator.
2. Modernization of the system of registration from the pd-reaction (Eγ = 5.5 MeV).
3. Manufacturing of ZrD, ZrD2, Ta2D, TiD2 targets by reactive magnetron sputtering.
4. Investigation of the pd-reaction (pd→3He + γ (5.5 MeV)) in the energy region of protons
incident on the target (from 3 to 15 keV) using targets of ZrD2, ZrD, TaD2, TiD2 and D2O.
5. Carrying out of experiments using the Auger-spectrometer and the ERD method to
inspect the target surface and to measure the deuterium distribution in depth of the target
before and after the dd-experiment.
6. Quantitative determination of the influence of the electron screening effect on the
increase of the pd-reaction cross-section with decreasing proton-deuteron collision
energy.
7. Carrying out of experiments on the Van de Graaf accelerator to measure the deuterium
distribution in depth of the target and to inspect the target surface using the Augerspectrometer before and after the pd-experiment.
8. Preparation of the pd-reaction research results for publication.
2012
The aim: investigation of the dependence of the astrophysical S-factor and d3He-reaction
cross-section on the 3Не-ions–deuteron collision energy in the region of 2-6 keV; determination
of the contribution to the d3He-reaction cross-section due to the electron screening effect of 3Не
nuclei interacting with deutrons in metal deuterides.
1. Formation of a 3Не ion beam with intensity of 1014 1/pulse and surface density j ~ 1
A/сm2 to study d3Не-reaction (d3Не → p (14.7 MeV) + α (3.7 MeV)) in the 3Не-ion
energy region of 3-15 keV.
2. Development and construction of an annular semiconductor silicon detector for
registration of protons and alpha-particles formed in the d3Не-reaction.
3. Manufacturing of ZrD, ZrD2, Ta2D, TiD2 targets by reactive magnetron sputtering.
4. Carrying out of d3Не-experiment to measure the dependence of the astrophysical S-factor
and d3Не-reaction cross-section on the energy of collision of 3Не nuclei with deuterons
using the Hall accelerator and D2O, ZrD2, ZrD, Ta2D, TiD2 targets.
5. Carrying out of experiments using the Auger-spectrometer and the ERD method to
inspect the target surface and to measure the deuterium distribution in depth of the target
before and after the d3He-experiment.
6. Determination of the contribution to the d3Не-interaction cross-section due to the electron
screening effect.