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Radiolytic ROS production mechanism under proton flash conditions : combination of experimental and simulation investigation
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Weak supersymmetric su(N|1) quantum systems
No full textInternational audienceIn this paper, we present several examples of supersymmetric quantum mechanical systems with weak superalgebra su(N|1). One of them is the weak su(N|1) oscillator. It has a singlet ground state, N + 1 degenerate states at the first excited level, etc. Starting from the level k = N + 1, the system has complete supersymmetric multiplets at each level involving 2N degenerate states. Due to the fact that the supermultiplets are not complete for k ≤ N, the Witten index represents a nontrivial function of β. This system can be deformed with keeping the algebra intact. The index is invariant under such deformation. The deformed system is not exactly solved, but the invariance of the index implies that the energies of the states at the first N levels of the spectrum are not shifted, and we are dealing with a quasi-exactly solvable system. Another system represents a weak generalization of the superconformal mechanics with N complex supercharges. Also in this case, starting from a certain energy, the spectrum involves only complete supersymmetric 2N-plets. (There also exist normalizable states with lower energies, but they do not have normalizable superpartners. To keep supersymmetry, we have to eliminate these states.
226Ra and 137Cs determination by inductively coupled plasma mass spectrometry: state of the art and perspectives including sample pretreatment and separation steps
No full textInternational audienceAchieving precise and accurate quantification of radium (226Ra) and cesium (137Cs) by inductively coupled plasma mass spectrometry (ICP-MS) is of particular interest in the field of radiological monitoring and more widely in environmental and biological sciences. However, the accuracy and sensitivity of the quantification depend on the analytical strategy implemented. Eliminating interferences during the sample handling step and/or during the analysis step is critical since presence of matrix elements can lead to spectral and non-spectral interferences in ICP-MS. Consequently, before the ICP-MS analysis, multiple sample preparation approaches have been applied to purify and/or pre-concentrate environmental and biological samples containing radium and cesium through years, such as (co)-precipitation, solid phase extraction (SPE) or dispersive SPE (dSPE). Separation steps using liquid chromatography and capillary electrophoresis can also be useful in complement with the abovementioned sample preparation techniques. The most attractive sample handling technique remains SPE but efficiency of the extraction procedures is currently limited by sorbent specificity. Indeed, with the recent advances in ICP-MS instrumentation, it becomes indispensable to eliminate residual interferences and improve sensitivity. It is in this direction that it will be possible to meet analytical challenges, e.g. analyzing radium and cesium at concentrations below the pg L−1 range in complex matrices of small volumes, as they are found for instance in pore waters or in biological samples. Development of new innovative sorbents based for example on hybrid and nanostructured materials has been reported with the aim of enhancing sorbent specificity and/or capacity. In the present review, the performances of the different analytical approaches are discussed, followed by an overview of applications
K<math altimg="si1.svg"><msubsup><mrow/><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math>K<math altimg="si1.svg"><msubsup><mrow/><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math> and K<math altimg="si1.svg"><msubsup><mrow/><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>0</mn></mrow></msubsup></math>K± femtoscopy in pp collisions at <math altimg="si2.svg"><msqrt><mrow><mi>s</mi></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>5.02</mn></math> and 13 TeV
No full textInternational audienceFemtoscopic correlations with the particle pair combinations KS0KS0 and KS0K± are studied in pp collisions at s=5.02 and 13 TeV by the ALICE experiment. At both energies, boson source parameters are extracted for both pair combinations, by fitting models based on Gaussian size distributions of the sources, to the measured two-particle correlation functions. The interaction model used for the KS0KS0 analysis includes quantum statistics and strong final-state interactions through the f0(980) and a0(980) resonances. The model used for the KS0K± analysis includes only the final-state interaction through the a0 resonance. Source parameters extracted in the present work are compared with published values from pp collisions at s=7 TeV and the different pair combinations are found to be consistent. From the observation that the strength of the KS0KS0 correlations is significantly greater than the strength of the KS0K± correlations, the new results are compatible with the a0 resonance being a tetraquark state of the form (q1,q2‾,s,s‾), where q1 and q2 are u or d quarks
Measurement of the groomed jet radius and momentum splitting fraction in pp and PbPb collisions at TeV
No full textInternational audienceThis article presents groomed jet substructure measurements in pp and Pb-Pb collisions at sNN=5.02 TeV with the ALICE detector. The soft drop grooming algorithm provides access to the hard parton splittings inside a jet by removing soft wide-angle radiation. We report the groomed jet momentum splitting fraction, zg, and the (scaled) groomed jet radius, θg. Charged-particle jets are reconstructed at midrapidity using the anti-kT algorithm with resolution parameters R=0.2 and R=0.4. In heavy-ion collisions, the large underlying event poses a challenge for the reconstruction of groomed jet observables, since fluctuations in the background can cause groomed parton splittings to be misidentified. By using strong grooming conditions to reduce this background, we report these observables fully corrected for detector effects and background fluctuations for the first time. A narrowing of the θg distribution in Pb-Pb collisions compared to pp collisions is seen, which provides direct evidence of the modification of the angular structure of jets in the quark-gluon plasma. No significant modification of the zg distribution in Pb-Pb collisions compared to pp collisions is observed. These results are compared with a variety of theoretical models of jet quenching, and provide constraints on jet energy-loss mechanisms and coherence effects in the quark-gluon plasma
How radiolysis impacts astatine speciation?
No full textInternational audienceThis work deals with the impact of chloroform radiolysis on astatine chemistry. Astatine-211 is a promising radionuclide for the targeted alpha therapy of cancers. Yet, the production of 211 At based radiopharmaceuticals is often complicated by radiolysis due to its own decay, leading to solvent degradation and then impacting astatine chemical state and radiolabeling efficiency. A better understanding of the radiolysis phenomenon is thus necessary. Two experiments are performed: (1) pH measurement during the At extraction in chloroform medium, (2) pH determination calculated from the HCl chemical yield which is obtained during the radiolysis of chloroform medium by γ-ray. In both cases, the pH values are determined at 2.0 ± 0.5. Then, it is possible to predict the acidic conditions during the 211 At production by HCl radiolytic yield determination. This work demonstrated that the radiolysis induced by At during its production in CHCl3 medium should be taken into account as it has a significant effect on acid-basic conditions. The work helps understanding the mechanisms of production of a major impurity generated from 211 At radiolysis in chloroform which alters its radiochemistry, allowing for the identification of solutions to counteract these unwanted effects
Study of Injection Line of the Cyclotrons C70XP of Arronax
No full textInternational audienceThe cyclotron C70XP is an accelerator built for the production of non-conventional radionuclides for nuclear medicine, research in physics, radio-chemistry and biology. Its injection section has been designed for 4 types of ions (HH⁺, D-, He2+ & H⁻), 3 types of ions reach the end of the beamline (H⁺, He2+ & D⁺) at the maximum energy of 70 MeV (H⁻ & He2+). It is important that regular and standard runs provide similar beam features with a good emittance quality. An investigation, focused on the beam in the injection, cover beam measurements and potential beam geometry constraints. The beam transverse characteristics in the injection line has been studied with an Allison-type emittance meter and a simple instrumented collimator installed inside the injection line *. With these 2 devices, it is scrutinized how the beam emittance evolves as a function of settings of the injection magnets and the source parameters **. Dependencies found between the emittance, beam hotspots and tunings are discussed, as well as the protection performed by the collimator. Future of this work with a potential collimator design is introduced
enhancement with non-thermalized bottom quarks in nuclear collisions at Large Hadron Collider
No full textInternational audienceWe study production in high-energy nuclear collisions in a transport approach with dissociation and regeneration at finite temperatures. Due to the rare production in p+p collisions and the strong combination of uncorrelated and quarks in the quark-gluon plasma, the yield is clearly enhanced in the nuclear collisions at the Large Hadron Collider. Besides, the centrality and momentum-dependent yield of sensitively reflect the thermalization degree of bottom quarks. And the newly observed experimental data favors a far from the thermal bottom quark distribution in the quark-gluon plasma
Pourbaix diagram of astatine revisited: experimental investigations
No full textInternational audienceThe Pourbaix diagram of an element displays its stable chemical forms with respect to the redox potential and pH of the solution, whose knowledge is fundamental for understanding and anticipating the chemistry of the element in a specified solution. Unlike most halogens, the Pourbaix diagram in the aqueous phase for astatine (At, Z = 85) is still under construction. In particular, the predominant domains of two astatine species assumed to exist under alkaline conditions, At and AtO(OH), need to be refined. Through high-performance ion-exchange chromatography, electromobility measurements, and competition experiments, the existence of At and AtO(OH) has been confirmed and the associated standard potential has been determined for the first time (0.86 ± 0.05 V vs the standard hydrogen electrode). On the basis of these results, a revised version of astatine’s Pourbaix diagram is proposed, covering the three oxidation states of astatine that exist in the thermodynamic stability range of water: At(-I), At(I), and At(III) (as , , AtO(+), AtO(OH), and AtO(OH)$^-