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arXiv2013

Quenching of Cross Sections in Nucleon Transfer Reactions

Cross sections for proton knockout observed in (e,e'p) reactions are apparently quenched by a factor of ~0.5, an effect attributed to short-range correlations between nucleons. Here we demonstrate that such quenching is not restricted to proton knockout, but a more general phenomenon associated with any nucleon transfer. Measurements of absolute cross sections on a number of targets between 16O and 208Pb were analyzed in a consistent way, with the cross sections reduced to spectroscopic factors through the distorted-wave Born approximation with global optical potentials. Across the 124 cases analyzed here, induced by various proton- and neutron-transfer reactions and with angular momentum transfer l=0-7, the results are consistent with a quenching factor of 0.55. This is an apparently uniform quenching of single-particle motion in the nuclear medium. The effect is seen not only in (d,p) reactions but also in reactions with A=3 and 4 projectiles, when realistic wave functions are used for the projectiles.

nucl-ex↗

arXiv2013

Excitation Function of the nat-Ta(p,x)178m2-Hf Reaction

178m2-Hf is an extremely interesting isomeric state due to its potential energy capacity level. One possible way to obtain it is by irradiation of a nat-Ta sample with a high-current proton accelerator. Up to now, there was no information in the international experimental nuclear data base (EXFOR) for this reaction. Irradiations of nat-Ta samples performed for other purposes provide an opportunity to address this question. This paper presents the 172m2-Hf independent production cross-sections determined by gamma-ray spectrometry. The nat-Ta(p,x)172m2-Hf excitation function is studied in the 20-3500 MeV energy range. Comparisons with results by several nuclear models (ISABEL, Bertini, INCL4.5+ABLA07, PHITS, CASCADE07, and CEM03.02) used as event-generators in modern transport codes are also reported. However, since such models are generally not able to separately predict ground and isomeric states of reaction products, only 178-Hf independent and cumulative cross-section data are compared.

nucl-ex↗

arXiv2013

Krypton-85 in the atmosphere

Measurement results are presented on 85Kr content in the atmosphere over the European part of Russia in 1971-1995 based on the analysis of the commercial krypton, which is separated from air by industrial plants. Our results are by 15 per cent lower then 85Kr activites observed over West Europe. According our prediction by 2030 85Kr content in the atmosphere over Europe will amount to 1,5-3 Bq in m3 air. Average 85Kr release to the atmosphere from regeneration of spent nuclear fuel (SNF) is estimated, some 180 TBq per a ton SNF. It is advisable to recommence monitoring of 85Kr content within Russia.

physics.ao-ph↗

arXiv2013

Features of adsorbed radioactive chemical elements and their isotopes distribution in iodine air filters AU-1500 at nuclear power plants

The main aim of research is to investigate the physical features of spatial distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the iodine air filters of the type of AU1500 in the forced exhaust ventilation systems at the nuclear power plant. The gamma activation analysis method is applied to accurately characterize the distribution of the adsorbed radioactive chemical elements and their isotopes in the granular filtering medium in the AU1500 iodine air filter after its long term operation at the nuclear power plant. The typical spectrum of the detected chemical elements and their isotopes in the AU1500 iodine air filter, which was exposed to the bremsstrahlung gamma quantum irradiation, produced by the accelerating electrons in the tantalum target, are obtained. The spatial distributions of the detected chemical element 127I and some other chemical elements and their isotopes in the layer of absorber, which was made of the cylindrical coal granules of the type of SKT3, in the AU1500 iodine air filter are also researched. The possible influences by the standing acoustic wave of air pressure in the iodine air filter on the spatial distribution of the chemical elements and their isotopes in the iodine air filter are discussed. The comprehensive analysis of obtained research results on the distribution of the adsorbed chemical elements and their isotopes in the absorber of iodine air filter is performed.

physics.ao-ph↗

arXiv2013

Next-Generation Liquid-Scintillator-Based Detectors: Quantums Dots and Picosecond Timing

Liquid-scintillator-based detectors are a robust technology that scales well to large volumes. For this reason, they are attractive for experiments searching for neutrinoless double-beta decay. A combination of improved photo-detection technology and novel liquid scintillators may allow for the extraction of particle direction in addition to the total energy of the particle. Such an advance would find applications beyond searches for neutrinoless double-beta decay.

physics.ins-det↗

arXiv2013

The initial results of research on two-step cascades in the Dalat research reactor

By the financial support of Vietnam Atomic Energy Commission and kind cooperation of Frank Laboratory, in the year of 2005 a measure system based on summation of amplitude pulses was established on the tangential channel of Dalat Research Reactor. After a serial of testing, the measure system was explored. In this, we would like to show the initial results were gotten with 36-Cl isotope.

nucl-ex↗

arXiv2013

Coupling constant for $Λ(1405)\bar{K}N$

The value of the $Λ(1405){\bar K}N$ coupling constant $g_{Λ(1405)\bar{K}N}$ is obtained by fitting it to the experimental data on the total cross sections of the $K^-p \to π^0Σ^0$ reaction. On the basis of an effective Lagrangian approach and isobar model, we show that the value $|g_{Λ(1405)\bar{K}N}| = 1.51 \pm 0.10$ could be extracted from the available experimental data by assuming that the $s-$channel $Λ(1405)$ resonance plays a dominant role, whereas, the background contributions from the $s-$channel $Λ(1115)$, $t-$channel $K^*$ and $u-$channel nucleon pole processes are small and can be neglected. However, the $u-$channel nucleon pole diagram may also give an important contribution in the present calculations. After the background contributions are taken into account, the above value of $g_{Λ(1405)\bar{K}N}$ is reduced to $|g_{Λ(1405)\bar{K}N}| = 0.77 \pm 0.07$, which is not supported by the previous calculations and the recent CLAS measurements. The theoretical calculations on differential cross sections are also presented, which can be checked by future experiments.

nucl-th↗

arXiv2013

Properties of non-q\bar{q} XYZ mesons and results of a search for the H-dibaryon

A number of charmonium- and bottomonium-like meson states have been observed that have properties that do not match well to expectations for the simple quark-antiquark substructure suggested by the constituent quark model. Some of them are electrically charged and decay to final states containing hidden charmonum or bottomonium mesons and, thus, must contain at least four quarks. Common properties of these so-called XYZ mesons are partial widths for decays to hidden quarkonium states plus light hadrons that are much larger than corresponding partial widths for established quarkonium mesons. I review some recent results from the Belle experiment, including the recent discovery of two charged bottomium-like states, the Z_b(10610)^+ and Z_b(10650)^+, that decay to pi^+pi^- h_b(mS) (m=1,2) and pi^+ Upsilon(nS) (n=1,2,3) final states. In addition, I present recent Belle results from a search for H-dibaryon production in inclusive Upsilon(1S) and Upsilon(2S) decays.

nucl-ex↗

arXiv2013

Heavy ion collisions in the 1A GeV regime: how well do we join up to astrophysics?

The derivation of information useful for understanding the physics inside compact stars from HIC observations is a difficult task. Complications due to finite size, different chemistry, non-adiabatic compression, incomplete stopping and structural effects must be overcome. This can only be convincingly achieved by a successful simulation of many experimental observables varying incident energy, system size and isospin content. Using now available systematic FOPI data in the SIS energy range we try to trace the path to take.

nucl-ex↗

arXiv2013

Thermalized Non-Equilibrated Matter against Random Matrix Theory, Quantum Chaos and Direct Interaction: Warming up

The idea of a thermalized non-equilibrated state of matter offers a conceptually new understanding of the strong angular asymmetry. In this compact review we present some clarifications, corrections and further developments of the approach, and provide a brief account of results previously discussed but not reported in the literature. The cross symmetry compound nucleus $S$-matrix correlations are obtained (i) starting from the unitary $S$-matrix representation, (ii) by explicitly taking into account a process of energy equilibration, and (iii) without taking the thermodynamic limit of an infinite number of particles in the thermalized system. It is conjectured that the long phase memory is due to the exponentially small total spin off-diagonal resonance intensity correlations. This manifestly implies that the strong angular asymmetry intimately relates to extremely small deviations of the eigenfunction distribution from Gaussian law. The spin diagonal resonance intensity correlations determine a new time/energy scale for a validity of random matrix theory. Its definition does not involve overlaps of the many-body interacting configurations with shell model non-interacting states and thus is conceptually different from the physical meaning (inverse energy relaxation time) of the spreading widths introduced by Wigner. Exact Gaussian distribution of the resonance wave functions corresponds to the instantaneous phase relaxation. We invite the nuclear reaction community for the competition to describe, as the first challenge, the strong forward peaking in the typically evaporation part of the proton spectra. This is necessary to initiate revealing long-term misconduct in the heavily cross-disciplinary field, also important for nuclear industry applications.

quant-ph↗

arXiv2013

First measurements of spin correlations in the np -> d pi^0 reaction

The transverse spin correlations Axx and Ayy in the np-> d pi^0 reaction have been measured for the first time in quasi-free kinematics at the COSY-ANKE facility using a polarised deuteron beam incident on a polarised hydrogen cell target. The results obtained for neutron energies close to 353 MeV and 600 MeV are in good agreement with the partial wave analysis of data on the isospin-related pp-> d pi^+ reaction, though the present results cover also the small-angle region, which was largely absent from these data.

nucl-ex↗

arXiv2013

Experiment Anti-Helium (Production of Nuclei and Anti-Nuclei. Limits for "exotic" particles of long lifetime)

Data are recalled on the relative yields of charged pions,charged kaons,protons,antiprotons,tritiun nuclei, anti-tritium, He3 nuclei and anti-He3 antinuclei produced at 0 degrees by 200-240 GeV/c protons on Beryllium and Aluminium targets. A search for the production of long-lived particles with charges 2/3, 1, 4/3, is described; for negative particle production the upper limits obtained at the 95% Confidence Level were at the level of 10-11 with respect to the production of known particles.

nucl-ex↗

arXiv2013

First Beam Observation and Near Future Plans at SPring-8 LEPS2 Experiments

The first photon beam was successfully produced by laser Compton backscattering at the LEPS2 beamline, which was newly constructed at SPring-8 for the purpose to increase the beam intensity one order of magnitude more than that of the LEPS experiments and to achieve the large acceptance coverage with high resolution detectors. The BGOegg electromagnetic calorimeter with associated detectors are being set up at the LEPS2 experimental building for the physics programs, including the searches for $η$'-bound nuclei and highly excited baryon resonances. In parallel to the BGOegg experiments, the LEPS2 charged particle spectrometer will be prepared inside the 1 Tesla solenoidal magnet, transported from the BNL-E949 experiment.

physics.ins-det↗

arXiv2013

The OscSNS White Paper

There exists a need to address and resolve the growing evidence for short-baseline neutrino oscillations and the possible existence of sterile neutrinos. Such non-standard particles require a mass of $\sim 1$ eV/c$^2$, far above the mass scale associated with active neutrinos, and were first invoked to explain the LSND $\bar ν_μ\rightarrow \bar ν_e$ appearance signal. More recently, the MiniBooNE experiment has reported a $2.8 σ$ excess of events in antineutrino mode consistent with neutrino oscillations and with the LSND antineutrino appearance signal. MiniBooNE also observed a $3.4 σ$ excess of events in their neutrino mode data. Lower than expected neutrino-induced event rates using calibrated radioactive sources and nuclear reactors can also be explained by the existence of sterile neutrinos. Fits to the world's neutrino and antineutrino data are consistent with sterile neutrinos at this $\sim 1$ eV/c$^2$ mass scale, although there is some tension between measurements from disappearance and appearance experiments. In addition to resolving this potential major extension of the Standard Model, the existence of sterile neutrinos will impact design and planning for all future neutrino experiments. It should be an extremely high priority to conclusively establish if such unexpected light sterile neutrinos exist. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, built to usher in a new era in neutron research, provides a unique opportunity for US science to perform a definitive world-class search for sterile neutrinos.

physics.ins-det↗

arXiv2013

Evidence for a pion condensate formation in pp interactions at U-70

A high multiplicity study (project Thermalization, experiment E-190) is carried out on U-70 accelerator at IHEP (Protvino, Russia). This project is aimed at searching for collective phenomena. It is known that pions are mainly produced at the 50 GeV-proton beam accelerator. Their mean energy decreases while multiplicity increasing. Bose-Einstein condensate (BEC) can be formed in this system. The theoretical and experimental studies of BEC have been performed since 70es. Within the framework of an ideal pion gas model M. Gorenstein and V. Begun have shown that sharp growth of fluctuations of the neutral pion number will be a signal of BEC formation with the increase of the total multiplicity (neutral and charged particle sum). SVD-2 Collaboration (JINR, IHEP and SINP MSU) investigated fluctuations of the neutral pion number in pp interactions at 50 GeV/c incident beam on U-70 versus the total multiplicity and has revealed noticeable growth of the scaled variance with the total multiplicity increase. The growth of these fluctuations reaches more than 7 standard deviations for the scaled variance at the total multiplicity about 30 pions as opposed to the tendency for the simulated events. This growth has been observed both in the registered photons and restored neutral pions.

hep-ex↗

arXiv2013

Numerical simulation of non-steady state neutron kinetics of the TRIGA Mark II reactor Vienna

This paper presents an algorithm for numerical simulations of non-steady states of the TRIGA MARK II reactor in Vienna, Austria. The primary focus of this work has been the development of an algorithm which provides time series of integral neutron flux after reactivity changes introduced by perturbations without the usage of thermal-hydraulic / neutronic numerical code systems for the TRIGA reactor in Vienna, Austria. The algorithm presented takes into account both external reactivity changes as well as internal reactivity changes caused by feedback mechanisms like effects caused by temperature changes of the fuel and poisoning effects. The resulting time series have been compared to experimental results.

physics.ins-det↗

arXiv2013

In-situ gamma spectrometry measurements of time-dependent Xenon-135 inventory in the TRIGA Mark II reactor Vienna

In this work, it has been shown that the time dependent Xe-135 inventory in the TRIGA Mark II reactor in Vienna, Austria can be measured via gamma spectrometry even in the presence of strong background radiation. It is focussing on the measurement of (but not limited to) the nuclide Xe-135. The time dependent Xe-135 inventory of the TRIGA Mark II reactor Vienna has been measured using a temporary beam line between one fuel element of the core placed onto the thermal column after shutdown and a detector system located just above the water surface of the reactor tank. For the duration of one week, multiple gamma ray spectra were recorded automatically, starting each afternoon after reactor shutdown until the next morning. One measurement series has been recorded over the weekend. The Xe-135 peaks were extracted from a total of 1227 recorded spectra using an automated peak search algorithm and analyzed for their time-dependent properties. Although the background gamma radiation present in the core after shutdown was large especially in the lower energy range, the Xe-135 peak located at 249.8 keV could be extracted from the most spectra where present and could be compared to theoretical calculations.

physics.ins-det↗

arXiv2013

The MAJORANA DEMONSTRATOR: A Search for Neutrinoless Double-beta Decay of Germanium-76

The {\sc Majorana} collaboration is searching for neutrinoless double beta decay using $^{76}$Ge, which has been shown to have a number of advantages in terms of sensitivities and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated and that neutrinos are Majorana particles and would simultaneously provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region, $15 - 50$ meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of $\sim$1 count/t-y or lower in the region of the signal. The {\sc Majorana} collaboration, with funding support from DOE Office of Nuclear Physics and NSF Particle Astrophysics, is constructing the {\sc Demonstrator}, an array consisting of 40 kg of p-type point-contact high-purity germanium (HPGe) detectors, of which $\sim$30 kg will be enriched to 87% in $^{76}$Ge. The {\sc Demonstrator} is being constructed in a clean room laboratory facility at the 4850' level (4300 m.w.e.) of the Sanford Underground Research Facility (SURF) in Lead, SD. It utilizes a compact graded shield approach with the inner portion consisting of ultra-clean Cu that is being electroformed and machined underground. The primary aim of the {\sc Demonstrator} is to show the feasibility of a future tonne-scale measurement in terms of backgrounds and scalability.

physics.ins-det↗