scholarly journals Detection capability of Migdal effect for argon and xenon nuclei with position sensitive gaseous detectors

2020 ◽  
Author(s):  
Kiseki D Nakamura ◽  
Kentaro Miuchi ◽  
Shingo Kazama ◽  
Yutaro Shoji ◽  
Masahiro Ibe ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Experimental Approach ◽  
Isotope Separation ◽  
Mass Region ◽  
Background Rate ◽  
Argon Gas ◽  
Low Mass ◽  
Position Sensitive ◽  
Set Up ◽  
Direct Dark Matter

Abstract Migdal effect is attracting interests because of the potential to enhance the sensitivities of direct dark matter searches to the low mass region. In spite of its great importance, the Migdal effect has not been experimentally observed yet. A realistic experimental approach towards the first observation of the Migdal effect in the neutron scattering was studied with Monte Carlo simulations. In this study, potential background rate was studied together with the event rate of the Migdal effect by a neutron source. It was found that a table-top sized ~ (30cm)3 position-sensitive gaseous detector filled with argon or xenon target gas can detect characteristic signatures of the Migdal effect with sufficient rates (O(102 ~ 103) events/day). A simulation result of a simple experimental set-up showed two significant background sources, namely the intrinsic neutrons and the neutron induced gamma-rays. It is found that the intrinsic neutron background rate for the argon gas is acceptable level and some future study for the reduction of the gamma-rays from the laboratory would make the observation of the Migdal effect possible. The background for the xenon gas, on the other hand, is found to be much more serious than for the argon gas. Future works on the isotope separation as well as the reduction of the gamma-rays from the detector and laboratory will be needed before the Migdal effect observation for xenon gas case.

scholarly journals Lithium-Containing Crystals for Light Dark Matter Search Experiments

2019 ◽  
Vol 199 (1-2) ◽  
pp. 510-518 ◽  
Author(s):  
E. Bertoldo ◽  
◽  
A. H. Abdelhameed ◽  
G. Angloher ◽  
P. Bauer ◽  
...  
Keyword(s):  
Dark Matter ◽  
Neutron Flux ◽  
Mass Region ◽  
Dark Matter Search ◽  
Ideal Candidate ◽  
Low Mass ◽  
Direct Dark Matter

AbstractIn the current direct dark matter search landscape, the leading experiments in the sub-GeV mass region mostly rely on cryogenic techniques which employ crystalline targets. One attractive type of crystals for these experiments is those containing lithium, due to the fact that $$^7\hbox {Li}$$7Li is an ideal candidate to study spin-dependent dark matter interactions in the low mass region. Furthermore, $$^6\hbox {Li}$$6Li can absorb neutrons, a challenging background for dark matter experiments, through a distinctive signature which allows the monitoring of the neutron flux directly on site. In this work, we show the results obtained with three different detectors based on $$\hbox {LiAlO}_2$$LiAlO2, a target crystal never used before in cryogenic experiments.

scholarly journals Development of a position-sensitive fast scintillator (LaBr3(Ce)) detector setup for gamma-ray imaging application

2021 ◽  
Vol 253 ◽  
pp. 11005
Author(s):  
Biswajit Das ◽  
R. Palit ◽  
R. Donthi ◽  
A. Kundu ◽  
S. R. Laskar ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Geant4 Simulation ◽  
Position Information ◽  
Coincidence Technique ◽  
Imaging Application ◽  
Gamma Ray Imaging ◽  
Position Sensitive ◽  
Set Up ◽  
Detector Crystal

We have characterized a Cerium doped Lanthanum Bromide (LaBr3(Ce) ) crystal coupled with the position-sensitive photo-multiplier system for the gamma-ray imaging application. One can use this detector set-up for the scanning of high purity germanium detectors for pulse shape analysis in gamma-ray spectroscopy experiments and the image formation of an object by Compton back-scattering . The sensor has been tested for energy, timing and position information of the gamma-rays interacting within the detector crystal. The GEANT4 simulation results are consistent with the experimental results. We have reconstructed the image of irradiation spots in different positions throughout the detector crystal. Position resolution is found to be around 3.5 mm with the 2 mm collimated gamma-rays. The 2-d image of hexagonal Bismuth Germanate (BGO) crystal and a cylindrical LaBr3(Ce) crystal have been reconstructed in coincidence technique. The performance of the detector for imaging application has been investigated by coincidence technique in GEANT4 simulation and compared with the experimental data. We have reconstructed the 2-d images of objects with various geometrical shapes by Compton back-scattered events of the gamma-rays. This position-sensitive detector can be used as an absorber of a Compton camera for the image reconstruction of an extended radioactive source. One can also use this kind of set-up as in radiation imaging and many other applications where the energy and source position of the gamma-ray is the main interest.

scholarly journals Small Mass but Strong Information: Diagnostic Ions Provide Crucial Clues to Correctly Identify Histone Lysine Modifications

Proteomes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Alaa Hseiky ◽  
Marion Crespo ◽  
Sylvie Kieffer-Jaquinod ◽  
François Fenaille ◽  
Delphine Pflieger
Keyword(s):  
Amino Acid ◽  
Small Mass ◽  
Mass Region ◽  
Amino Acid Sequences ◽  
Lysine Modification ◽  
Lysine Residues ◽  
Two Factors ◽  
Low Mass ◽  
Diagnostic Ions

(1) Background: The proteomic analysis of histones constitutes a delicate task due to the combination of two factors: slight variations in the amino acid sequences of variants and the multiplicity of post-translational modifications (PTMs), particularly those occurring on lysine residues. (2) Methods: To dissect the relationship between both aspects, we carefully evaluated PTM identification on lysine 27 from histone H3 (H3K27) and the artefactual chemical modifications that may lead to erroneous PTM determination. H3K27 is a particularly interesting example because it can bear a range of PTMs and it sits nearby residues 29 and 31 that vary between H3 sequence variants. We discuss how the retention times, neutral losses and immonium/diagnostic ions observed in the MS/MS spectra of peptides bearing modified lysines detectable in the low-mass region might help validate the identification of modified sequences. (3) Results: Diagnostic ions carry key information, thereby avoiding potential mis-identifications due to either isobaric PTM combinations or isobaric amino acid-PTM combinations. This also includes cases where chemical formylation or acetylation of peptide N-termini artefactually occurs during sample processing or simply in the timeframe of LC-MS/MS analysis. Finally, in the very subtle case of positional isomers possibly corresponding to a given mass of lysine modification, the immonium and diagnostic ions may allow the identification of the in vivo structure.

EVOLUTION OF SHELL STRUCTURE IN NUCLEI

2011 ◽  
Vol 20 (08) ◽  
pp. 1663-1675 ◽  
Author(s):  
A. BHAGWAT ◽  
Y. K. GAMBHIR
Keyword(s):  
Shell Structure ◽  
Crucial Role ◽  
Field Model ◽  
Mean Field ◽  
Mass Region ◽  
The Other ◽  
Mean Field Model ◽  
Relativistic Mean Field ◽  
Shell Closures ◽  
Low Mass

Systematic investigations of the pairing and two-neutron separation energies which play a crucial role in the evolution of shell structure in nuclei, are carried out within the framework of relativistic mean-field model. The shell closures are found to be robust, as expected, up to the lead region. New shell closures appear in low mass region. In the superheavy region, on the other hand, it is found that the shell closures are not as robust, and they depend on the particular combinations of neutron and proton numbers. Effect of deformation on the shell structure is found to be marginal.

scholarly journals Dimensioning a Call Center: Simulation or Queue Theory?

2009 ◽  
Vol 2 (2) ◽  
pp. 34 ◽  
Author(s):  
Marco Aurélio Carino Bouzada
Keyword(s):  
Analytical Method ◽  
Analytical Methods ◽  
Call Center ◽  
Experimental Approach ◽  
Call Centers ◽  
Experimental Methods ◽  
New Approach ◽  
Alternative Methodology ◽  
Queue Theory ◽  
Set Up

The objective of this paper is to establish a dichotomy - opposing analytical methods (such as Queue Theory) to experimental methods (such as Simulation) and discussing their adequateness to complex operations - set up in the matter of dimensioning the handling capacity of a large brazilian call centers company. The literature related to the application of such methods at call centers is reviewed, and the way the question is treated nowadays by the company is described. Then an experimental approach is suggested to be implemented as an alternative methodology to deal with the issue, instead of the analytical method in use. The results obtained are used to justify the adequacy of the experimental approach to the modern call centers operation, as long as it is possible to have the model closer to reality. The main implication points to a better understanding of the operation achieved with the new approach

scholarly journals Improving the performance of 241Am-Be for PGNAA applications using a proper shielding for neutron source and the NaI detector

2010 ◽  
Vol 25 (3) ◽  
pp. 205-211 ◽  
Author(s):  
Hamed Panjeh ◽  
Hashem Hakimabad ◽  
Lalle Motavalli
Keyword(s):  
Gamma Rays ◽  
Energy Region ◽  
Gamma Ray ◽  
Region Of Interest ◽  
High Rate ◽  
Prompt Gamma ◽  
Peak Resolution ◽  
Set Up ◽  
Gamma Ray Detector

The gamma ray spectrum resolution from a 241Am-Be source-based prompt gamma ray activation analysis set-up has been observed to increase in the energy region of interest with enclosing the NaI detector in a proper neutron and gamma ray shield. We have investigated the tact that the peak resolution of prompt gamma rays in the region of interest from the set-up depends on the source activity to the great extent, size and kind of the detector and the geometry of the detector shield. In order to see the role of a detector shield, five kinds of the detector shield were used and finally the proper kind was introduced. Since the detector shield has an important contribution in the reduction of the undesirable and high rate gamma rays coming to the gamma ray detector, a good design of a proper shield enables the elimination of the unwanted events, such as a pulse pile-up. By improving the shielding design, discrete and distinguishable photoelectric peaks in the energy region of interest have been observed in the spectrum of prompt gamma rays.

scholarly journals On the origin of the bimodal rotational velocity distribution in stellar clusters: rotation on the pre-main sequence

2020 ◽  
Vol 495 (2) ◽  
pp. 1978-1983
Author(s):  
Nate Bastian ◽  
Sebastian Kamann ◽  
Louis Amard ◽  
Corinne Charbonnel ◽  
Lionel Haemmerlé ◽  
...  
Keyword(s):  
Main Sequence ◽  
Rotational Velocity ◽  
Open Clusters ◽  
Observational Constraints ◽  
Stellar Clusters ◽  
Period Distribution ◽  
Low Mass ◽  
Rotational Distribution ◽  
Set Up ◽  
Pms Stars

ABSTRACT We address the origin of the observed bimodal rotational distribution of stars in massive young and intermediate age stellar clusters. This bimodality is seen as split main sequences at young ages and also has been recently directly observed in the Vsini distribution of stars within massive young and intermediate age clusters. Previous models have invoked binary interactions as the origin of this bimodality, although these models are unable to reproduce all of the observational constraints on the problem. Here, we suggest that such a bimodal rotational distribution is set-up early within a cluster’s life, i.e. within the first few Myr. Observations show that the period distribution of low-mass ($\lesssim\! 2 \, \mathrm{M}_\odot$) pre-main-sequence (PMS) stars is bimodal in many young open clusters, and we present a series of models to show that if such a bimodality exists for stars on the PMS that it is expected to manifest as a bimodal rotational velocity (at fixed mass/luminosity) on the main sequence for stars with masses in excess of ∼1.5 M⊙. Such a bimodal period distribution of PMS stars may be caused by whether stars have lost (rapid rotators) or been able to retain (slow rotators) their circumstellar discs throughout their PMS lifetimes. We conclude with a series of predictions for observables based on our model.

Sign in / Sign up

Export Citation Format

Share Document