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36th meeting, PAC for Nuclear Physics

I. Preamble

The Chairperson of the PAC, W. Greiner, welcomed the PAC members,

the ex officio members from JINR, and reminded of the implementation
of the recommendations taken at the previous meeting.

JINR Vice-Director M. Itkis informed the PAC about the Resolution of the 111th session of the Scientific Council (February 2012) and the decisions of the Committee

of Plenipotentiaries (March 2012). The PAC notes that all of the recommendations
of the previous PAC meeting concerning JINR research in the areas of nuclear physics have been accepted by the JINR Scientific Council and Directorate.

The PAC notes with satisfaction the approval by the International Union of Pure

and Applied Chemistry of the names flerovium and livermorium for elements 114 and 116 in honour of the Flerov Laboratory of Nuclear Reactions and the Lawrence Livermore National Laboratory (USA).
II. Theme “Improvement of the JINR Phasotron and Design of Cyclotrons
for Fundamental and Applied Research”

The PAC heard a report presented by G. Karamysheva on the results of numerous activities within the theme “Improvement of the JINR Phasotron and Design of Cyclotrons for Fundamental and Applied Research” (03-2-1102-2010/2012), focused on the design and improvement of accelerators for hadron therapy applications.

Upgrade of the power supply system of the Phasotron and replacement of the
motor-generators by thyristor converter TPP-5000, which was put into operation in 2011, has led to the improvement of the working conditions for the staff and to the reduction
of power consumption by 70 kW/h.

Following the agreement between the company IBA (Ion Beam Applications)

and JINR, assembly of the C235 cyclotron was done in the DLNP Building 5. Shimming
of the vertical component of the magnetic field was performed. Test experiments with extracted proton beams will be finished by September 2012. The cyclotron is in preparation for the hospital therapy centre in Dimitrovgrad (Russia).

In collaboration with the Department of the AIC-144 Cyclotron (Krakόw, Poland),

a stable 60 MeV proton beam was extracted from the cyclotron and was used for the first time for successful treatment of the eye melanoma for 11 patients in 2011 and 4 patients
in 2012.

Recommendation. The PAC recommends continuation of this programme within
the theme “Improvement of the JINR Phasotron and Development of Cyclotrons
for Fundamental and Applied Research” in 2013–2015 with first priority.
III. Theme “Physics of Light Mesons”

The PAC heard with interest a report on the theme “Physics of Light Mesons”

(03-2-1101-2010/2012) presented by A. Kulikov. The scientific programme concerns investigations of the production, decay and interaction of light mesons aimed
at determining the symmetries and the interaction dynamics. The experiments are carried out at the intermediate energy accelerators in Jülich, Mainz, Villigen, Gatchina, and Dubna. The theme includes six projects: MEG-PEN, SPRING, PAINUC, TRITON, GDH&SPASCHARM, and MUON.

The MEG-PEN project is devoted to the study of the rare and forbidden decays +e+ and +e+ at PSI. Analysis of accumulated statistics for +e+ will provide the ever best precision of the branching ratio of this decay. For the process +e+a record

for the upper limit of the decay probability has been already achieved, and it will be further improved when more events are collected.

The SPRING project is concerned with polarization phenomena in hadron interactions. Pion production, deuteron breakup and hard bremsstrahlung processes involving the formation of 1S0 diprotons have been studied at COSY resulting in important conclusions on the interaction properties and dynamics. Polarization build-up in the proton beam using the spin-filtering method has been demonstrated. New measurements

are planned with a longitudinally polarized beam.

In the PAINUC experiment, the ± 4He interactions are studied using

the self-shunting streamer chambers developed at DLNP. The unique feature
of this apparatus is used to detect tracks of very low-energy particles.

The TRITON project is aimed at filling the gap in the programme of muon catalysed fusion reactions. The p+t fusion reaction needs to be studied. The experimental set-up

is in the construction phase.

In the GDH&SPASCHARM project, spin asymmetries in photoproduction reactions are studied at MAMI in Mainz. A solid-state polarized target of very high quality has been developed and produced at JINR and is used in these experiments. Single spin asymmetries will also be studied at Protvino with a similar polarized solid-state target.

In the MUON project, muon beams in Gatchina and Villigen are used to study some properties of solid-state materials including superfine interactions in semiconductors, properties of magnetic fluids and other compounds with unusual magnetic properties.

Recommendation. The PAC strongly recommends continuation of the theme “Physics of Light Mesons” in 2013–2015 with first priority.

The PAC encourages DLNP to continue the research aimed at searching

for the lepton flavor violation. In particular, the PAC supports participation in R&D studies for the COMET experiment.
IV. Continuation of the projects under the theme “Physics of Light Mesons”

Project SPRING (“Spin physics at hadron storage rings”)

The PAC heard a report presented by A. Kulikov on the SPRING project carried

out at the COSY facility. The measurements using polarized beams and/or polarized
jet targets are of special interest allowing for deeper understanding of the spin-dependent characteristics of interactions. The PAC notes new important results obtained
in the reported period.

Experiments at the ANKE set-up were focused on processes with the formation

of 1S0 diprotons in the final state. These processes provide information on high-energy transfer reactions similar to those obtained from the well-known processes with deuterons in the final state.

The main goal of the PAX experiment is to measure the transversity distribution

in nucleons. Essential progress has been attained in the study of the method of polarizing
the beam proposed for this experiment, the so-called “spin filtering” technique.
The measurements have confirmed the validity of this effect and the correct understanding of its nature.

Recommendation. The PAC appreciates the high quality of investigations fulfilled within the SPRING project and recommends its continuation in 2013–2015 with first priority.

Project MEG-PEN-II (“Precise investigation of rare pion decays and search
for forbidden muon decays”)

The PAC heard a report presented by N. Khomutov on the MEG-PEN-II project, which is a continuation of a many-year programme of precision studies of rare

and forbidden decays of muons and pions at low energies. Analysis of the experimental data collected on the +e+ decay is expected to reach an accuracy comparable with
the precision of the calculations of this decay. A record-breaking value of the upper limit
on the branching ratio of the +e+ decay has been obtained.

Recommendation. The PAC highly appreciates the quality of research conducted within the MEG-PEN-II project and recommends continuation of this activity until
the end of 2015 with first priority.
V. Completion of the PAINUC project (“A study of pion interactions with helium nuclei at intermediate energies”)

The PAC heard a report by G. Pontecorvo on the programme of studies of pion interactions with helium nuclei at intermediate pion energies (below the D-resonance).

The project is aimed at revealing whether the production of single gammas (akin to prompt photons) observed in p± 4He interactions depends on the incident pion energy –– as well
as of the influence of the nuclear matter density on the D-resonance excitation.
The programme also includes studies of 3-prong reaction channels, in particular pion absorption, involving low-energy strongly ionizing secondaries. To this end,
a semiempirical model has been developed for the excitation of collective resonances.
The collaboration also intends to study the possibility of improving the muon neutrino mass, given the small number of such direct measurements. Recently, the collaboration
has overcome serious difficulties in the extraction of pion beams from the DLNP Phasotron. The pion beam intensity still has to be improved.

Recommendation. The PAC considers PAINUC to be an experiment of great interest and recommends continuation of the studies under way by the PAINUC collaboration within the framework of the topic “Physics of Light Mesons”. The PAC advises the collaboration
to successfully complete the extraction of pion beams and to present a new project as soon as possible.
VI. Recent development of ECR ion sources at FLNR

The PAC discussed in detail the report by S. Bogomolov concerning

the development of ECR ion sources. The PAC strongly supports the efforts
of the research team and the FLNR Directorate in this direction, noting that this activity
is an important part of the scientific programme allowing the Laboratory to reach
a considerable increase of beam intensity needed for further studies.

Recommendation. The PAC recommends starting preparations for the installation
of the DECRIS SC ion source in 2013.
VII. Scientific reports

The PAC highly appreciated the report “Summary of experimental results

on collinear cluster tri-partition studies” presented by D. Kamanin. The PAC notes
the interesting results obtained by the group and recommends continuation
of this promising study.

The PAC heard with interest the report “Neutron lifetime measurement in material traps: state of the art and prospects” presented by Yu. Pokotilovsky. The group has identified a new material for improving the UCN storage time constant and thereby

the precision of the experimental determination of the neutron lifetime.
VIII. Poster session

The PAC was pleased with the high quality of the presentations of new results

and proposals by young scientists in the field of nuclear physics research
and its applications. The best posters: “Superassymetric fission of transactinide nuclei”
by G. Knyazheva, “The 10He resonant states observed in correlation measurements
of the 8Не(3Н,р)10Не reaction” by S. Krupko, and “Moss biomonitoring in Albania using GIS technologies” by Z. Goryainova. The PAC recommends them for presentation
at the session of the Scientific Council in September 2012.
IX. Next meeting of the PAC

The next meeting of the PAC for Nuclear Physics will be held

on 24–25 January 2013.

Its tentative agenda will include:

  • Reports and recommendations on themes and projects to be completed in 2013

  • Development of the IREN facility

  • Status of the DANSS project

  • Consideration of new projects

  • Poster presentations of new results and proposals by young scientists in the field of nuclear physics research

  • Scientific reports (including on transmutation).

Walter Greiner

Chairperson of the PAC

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