Hasil untuk "Nuclear and particle physics. Atomic energy. Radioactivity"

Haruki Nakayama, Tatsuma Nishioka

Abstract We construct a holographic model of defect conformal field theories (DCFTs) with defects of codimension greater than one. Our construction generalizes the AdS/BCFT model by anchoring the end-of-the-world brane on defects at the asymptotic AdS boundary and imposing Dirichlet boundary conditions for the metric on the brane. We compute the defect entropy and defect free energy and show that the defect C $$ \mathcal{C} $$ -function is always non-negative. We further study holographic defect-localized RG flows triggered by a localized scalar field on the brane and show that the defect C $$ \mathcal{C} $$ -theorem holds. We also verify that our model reproduces the expected forms of correlation functions in DCFTs.

Wolfgang Osterhage

Alexei Sibidanov, Thomas E. Browder, Shawn Dubey et al.

Abstract Within the widely used EvtGen framework, we have added a new event generator model for B → K * ℓ + ℓ − with improved standard model (SM) decay amplitudes and possible BSM physics contributions, which are implemented in the operator product expansion in terms of Wilson coefficients. This event generator can then be used to estimate the statistical sensitivity of a simulated experiment to the most general BSM signal resulting from dimension-six operators. We describe the advantages and potential of the newly developed ‘Sibidanov Physics Generator’ in improving the experimental sensitivity of searches for lepton non-universal BSM physics and clarifying signatures. The new generator can properly simulate BSM scenarios, interference between SM and BSM amplitudes, and correlations between different BSM observables as well as acceptance bias. We show that exploiting such correlations substantially improves experimental sensitivity. As a demonstration of the utility of the MC generator, we examine the prospects for improved measurements of lepton non-universality in angular distributions for B → K * ℓ + ℓ − decays from the expected 50 ab −1 data set of the Belle II experiment, using a four-dimensional unbinned maximum likelihood fit. We describe promising experimental signatures and correlations between observables. The use of lepton-universality violating ∆-observables significantly reduces uncertainties in the SM expectations due to QCD and resonance effects and is ideally suited for Belle II with the large data sets expected in the next decade. Thanks to the clean experimental environment of an e + e − machine, Belle II should be able to probe BSM physics in the Wilson coefficients C 7 and C 7 ′ $$ {C}_7^{\prime } $$ , which appear at low q 2 in the di-electron channel.

Elizebeth Joseph, P. Sowmya, Avin Kumar et al.

Joseph Smith

Abstract We construct theories of free fermions in (2n − 1)-dimensions with SU(1, n) spacetime symmetry from the null reduction of fermions on a 2n-dimensional Ω-deformed Minkowski background for n = 2 and n = 3. These play a role in the 5d SU(1, 3)-invariant theories that are conjectured to offer a full description of certain 6d superconformal field theories. We find the (2n − 1)-dimensional manifestation of the supersymmetry of a free 2n-dimensional boson-fermion system, which we use to fix the fermion two-point functions. It is then shown that the full 2n-dimensional two-point function can be recovered through resummation. Limits of the theories are considered, and it is observed that both Galilean and Carrollian field theories appear in different regimes. We confirm that the correlation functions obey the SU(1, n) Ward identities and the representations of the fermions under this group are discussed.

M. Bertucci, A. Bosotti, A. D’Ambros et al.

This paper presents a quantitative description of field emission in superconducting rf cavities. The goal is to fully reconstruct the physics involved in the phenomenon, from electron current generation at the emitter to the radiation pattern measured by the x-ray detector. The field emission process in the cavity was reconstructed using CST Particle Studio, and then the generation of x-ray radiation and its propagation toward the detectors were modeled analytically. The entire model was then applied to the specific case of the European Spallation Source medium beta superconducting cavities, and the theoretical predictions were cross-checked with experimental data collected during cavity vertical tests.

L. K. Duchaniya, S. A. Kadam, Jackson Levi Said et al.

Abstract Teleparallel based cosmological models provide a description of gravity in which torsion is the mediator of gravitation. Several extensions have been made within the so-called teleparallel equivalent of general relativity which is equivalent to general relativity at the level of the equations of motion where attempts are made to study the extensions of this form of gravity and to describe more general functions of the torsion scalar T. One of these extensions is $$f(T,\phi )$$ f ( T , ϕ ) gravity; T and $$\phi $$ ϕ respectively denote the torsion scalar and scalar field. In this work, the dynamical system analysis has been performed for this class of theories to obtain the cosmological behaviour of a number of models. Two models are presented here with some functional form of the torsion scalar and the critical points are obtained. For each critical point, the stability behaviour and the corresponding cosmology are shown. Through the graphical representation, the equation of state parameter and the density parameters for matter-dominated, radiation-dominated and dark energy phase are also presented for both the models.

G. Aad, B. Abbott, D. C. Abbott et al.

Abstract In a special run of the LHC with $$\beta ^{\star } = 2.5$$ β ⋆ = 2.5  km, proton–proton elastic-scattering events were recorded at $$\sqrt{s} = 13$$ s = 13  TeV with an integrated luminosity of $$340~\upmu {\text {b}}^{-1}$$ 340 μ b - 1 using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from $$-t = 2.5 \cdot 10^{-4}$$ - t = 2.5 · 10 - 4  GeV $$^{2}$$ 2 to $$-t = 0.46$$ - t = 0.46  GeV $$^{2}$$ 2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section $$\sigma _{\text {tot}}$$ σ tot , parameters of the nuclear slope, and the $$\rho $$ ρ -parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit $$t \rightarrow 0$$ t → 0 . These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for $$\sigma _{\text {tot}}$$ σ tot and $$\rho $$ ρ are $$\begin{aligned} \sigma _{\text {tot}}(pp\rightarrow X) = 104.7 \pm 1.1 \; \text{ mb },\quad \rho = 0.098 \pm 0.011 . \end{aligned}$$ σ tot ( p p → X ) = 104.7 ± 1.1 mb , ρ = 0.098 ± 0.011 . The uncertainty in $$\sigma _{\text {tot}}$$ σ tot is dominated by the luminosity measurement, and in $$\rho $$ ρ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.

Kartalović Nenad M., Kovačević Uroš D., Nikezić Dušan P. et al.

The study considers the impact of the environmental contamination by the electromagnetic radiation of electron beam generator and high-energy radioactive source on the memory components. Electron beam generator can be used for injecting particle energy into the plasma of the fusion system based on a Marx generator, while radioactive source as a simulator of high-energy ionizing radiation that can be caused by the neutron-induced activation of plasma surrounding structures or released from deuterium-tritium fusion reaction. The effects of gamma radiation of high-energy radioactive source and electric field of the electron beam generator on EPROM and EEPROM semiconductor computer memory, were investigated. An older memory types were deliberately chosen for the reason that their more robust construction will better protect them from the effects of ionizing and non-ionizing radiation. The results obtained under well-controlled conditions show a high degree of non-resistance of the semiconductor technology to the expected electromagnetic pollution of the electron beam generator and high-energy radioactive source. This conclusion raises doubts on the possibility of simultaneous application of electron beam generator, consequently fusion system and nanotechnologies with the increasing need for miniaturization of electronic components.

Mehdi Ayouz, Alexandre Faure, Jonathan Tennyson et al.

Cross-sections and thermally averaged rate coefficients for vibration (de-)excitation of a water molecule by electron impact are computed; one and two quanta excitations are considered for all three normal modes. The calculations use a theoretical approach that combines the normal mode approximation for vibrational states of water, a vibrational frame transformation employed to evaluate the scattering matrix for vibrational transitions and the UK molecular R-matrix code. The interval of applicability of the rate coefficients is from 10 to 10,000 K. A comprehensive set of calculations is performed to assess uncertainty of the obtained data. The results should help in modelling non-LTE spectra of water in various astrophysical environments.

Pedro Agostini, Tolga Altinoluk, Néstor Armesto

Abstract We compute multi-gluon production in the Color Glass Condensate approach in dilute-dense collisions, $$\hbox {p}A$$ p A , extending previous calculations up to four gluons. We include the contributions that are leading in the overlap area of the collision but keep all orders in the expansion in the number of colors. We develop a diagrammatic technique to write the numerous color contractions and exploit the symmetries to group the diagrams and simplify the expressions. To proceed further, we use the McLerran–Venugopalan and Golec–Biernat–Wüsthoff models for the projectile and target averages, respectively. We use a form of the Lipatov vertices that leads to the Wigner function approach for the projectile previously employed, that we generalise to take into account quantum correlations in the projectile wave function. We provide analytic expressions for integrated and differential two gluon cumulants and show a smooth dependence on the parameters defining the projectile and target Wigner function and dipole, respectively. For four gluon correlations we find that the second order four particle cumulant is negative, so a sensible second Fourier azimuthal coefficient can be defined. The effect of correlations in the projectile on this result results qualitatively and quantitatively large.

Ralph Blumenhagen, Max Brinkmann, Andriana Makridou et al.

Abstract We investigate string-phenomenological questions of Hull’s exotic superstring theories with Euclidean strings/branes and multiple times. These are known to be plagued by pathologies like the occurrence of ghosts. On the other hand, these theories exhibit de Sitter solutions. Our special focus lies on the question of the coexistence of such de Sitter solutions and ghost-free brane worlds. To this end, the world-sheet CFT description of Euclidean fundamental strings is generalized to include also the open string/D-brane sector. Demanding that in the “observable” gauge theory sector the gauge fields themselves are non-ghosts, a generalization of the dS swampland conjecture is found.

Seyed Faroogh Moosavian, Ashoke Sen, Mritunjay Verma

Abstract We construct Lorentz invariant and gauge invariant 1PI effective action for closed and open superstrings and demonstrate that it satisfies the classical BV master equation. We also construct the quantum master action for this theory satisfying the quantum BV master equation and generalize the construction to unoriented theories. The extra free field needed for the construction of closed superstring field theory plays a crucial role in coupling the closed strings to D-branes and orientifold planes.

M.S. Terman, N. Mataji Kojouri, H. Khalafi

Monitoring the power distribution of reactor core is one of the most challenging issues in the safe operation of nuclear reactors. The Number and arrangement of detectors in a core monitoring system should be determined in a way that maximum amount of information about core states is extracted, while avoiding duplication of similar and correlated measurements. Information theory is the best method to deal with the problem of optimal number and placement of instruments. In this paper, the effects of reactor fuel burn-up on the optimal number and arragement of in-core fixed detectors of Tehran Research Reactor has been investigated using information theory. Comparison the results for the two modes, with and without consideration of the fuel burn-up, shows that by considering fuel burn-up in the placement problem, more information can be extracted from measurements of the detectors. Also, for an equal number of detectors, determined arrangement by considering fuel burn-up, mostly provide larger share of total available information in the data set. Using the optimal arrangement, maximum information can be obtained from minimum number of the detectors, which leads to considerable decrease in the cost of construction, implementation, operation, and maintenance of the in-core detectors for monitoring of neutron flux.

W. F. Bergan, I. V. Bazarov, C. J. R. Duncan et al.

Particle storage rings are a rich application domain for online optimization algorithms. The Cornell Electron Storage Ring (CESR) has hundreds of independently powered magnets, making it a high-dimensional test-problem for algorithmic tuning. We investigate algorithms that restrict the search space to a small number of linear combinations of parameters (“knobs”) which contain most of the effect on our chosen objective (the vertical emittance), thus enabling efficient tuning. We report experimental tests at CESR that use dimension-reduction techniques to transform an 81-dimensional space to an 8-dimensional one which may be efficiently minimized using one-dimensional parameter scans. We also report an experimental test of a multiobjective genetic algorithm using these knobs that results in emittance improvements comparable to state-of-the-art algorithms, but with increased control over orbit errors.

Keisuke Harigaya, Kyohei Mukaida, Masaki Yamada

Abstract We revisit the non-thermal dark matter (DM) production during the thermalization and reheating era after inflation. The decay of inflaton produces high-energy particles that are thermalized to complete the reheating of the Universe. Before the thermalization is completed, DM can be produced from a collision between the high-energy particles and/or the ambient plasma. We calculate the DM abundance produced from these processes for the case where the cross section of the DM production is proportional to the n-th power of the center of mass energy. We find that the collision between the high-energy particles is almost always dominant for n ≳ 4 while it is subdominant for n≲2. The production from the ambient plasma is dominant when n≲3 and the reheating temperature is of the order of or larger than the DM mass. The production from a collision between the high-energy particle and the ambient plasma is important for n ≲ 2 and the reheating temperature is much lower than the DM mass.

Stefano Calí, Suzanne Klaver, Marcello Rotondo et al.

Abstract Radiative corrections to $${B} \rightarrow {D} \ell {{\nu } _\ell } $$ B→Dℓνℓ decays may have an impact on predictions and measurements of the lepton flavour universality observables $$\mathcal {R}({{D} ^+})$$ R(D+) and $$\mathcal {R}({{D} ^0})$$ R(D0) . In this paper, a comparison between recent calculations of the effect of soft-photon corrections on $$\mathcal {R}({{D} ^+})$$ R(D+) and $$\mathcal {R}({{D} ^0})$$ R(D0) , and corrections generated by the widely used package Photos is given. The impact of long-distance Coulomb interactions, which are not simulated in Photos, is discussed. Furthermore, the effect of high-energy photon emission is studied through pseudo-experiments in an LHCb-like environment. It is found that over- or underestimating these emissions can cause a bias on $$\mathcal {R}({D})$$ R(D) as high as 7%. However, this bias depends on individual analyses, and future high precision measurements require an accurate evaluation of these QED corrections.

Andrzej Góźdź, Włodzimierz Piechocki, Grzegorz Plewa

Abstract We present the quantum model of the asymptotic dynamics underlying the Belinski–Khalatnikov–Lifshitz (BKL) scenario. The symmetry of the physical phase space enables making use of the affine coherent states quantization. Our results show that quantum dynamics is regular in the sense that during quantum evolution the expectation values of all considered observables are finite. The classical singularity of the BKL scenario is replaced by the quantum bounce that presents a unitary evolution of considered gravitational system. Our results suggest that quantum general relativity has a good chance to be free from singularities.

Bricio Mares Salles, A. Z. Mesquita, Marley Rosa Luciano

Nuclear research reactors are often found in open pools, allowing visibility of the core and the bluish luminosity of the Cherenkov radiation. In general, the thermal energy released in these reactors is monitored by chambers that measure neutron flux, because this is proportional to the power. There are other methods used to measure the power, including measure of the fuel rod central temperature and the energy balance in the heat exchanger. The brightness of Cherenkov radiation is caused by the emission of visible electromagnetic radiation (in the blue band) by charged particles that pass through an insulating medium (water in nuclear research reactors) at a speed greater than that of light in this medium. This effect was characterized by Pavel Cherenkov, earning him the Nobel Prize in physics in 1958. The objective of the present project is to develop an innovative and alternative method to monitor the power of nuclear research reactors. This will be done by analyzing and monitoring the intensity of luminosity generated by the Cherenkov radiation in the reactor core. This method will be valid for powers up to 250 kW, because above this value the brightness is saturated, as determined by previous studies. The reactor that will be used to test the method is the IPR R1 Triga, located at the Nuclear Technology Development Center (CDTN), currently with a maximum operating power of 250 kW. This project complies with the recommendations of the International Atomic Energy Agency (IAEA) on the safety of reactors. It will provide more redundancy and diversification in this measurement and will not interfere with the operation of the reactor.

Tainá Olivieri Chaves, Ana Cristina Murta Dovales, Luiz Antônio Ribeiro da Rosa et al.

Computed tomography (CT) scanning is a relatively high-dose procedure which use has been rapidly increasing in many countries, although a decline has been observed recently in some developed countries. Relatively little is known about CT usage in Brazil. A recent report showed that number of CT procedures among outpatients of the Brazilian public healthcare system (SUS) tripled from 2001 to 2011 and about 13% of all CTs procedures were underwent among pediatric and young adult patients. In the present study, we aimed to evaluate CT use in the private healthcare system, where the larger availability of CT scanners may result in a different CT usage pattern. We evaluated data from 15,892 CT procedures underwent by children and young adults (<20 years) between 2005 and 2015 in a private general hospital in the city of Rio de Janeiro. These procedures represented about 8% of the overall number of CT scans in the hospital over the study period. The number of CT examinations increased 10% per year, from 902 in 2005 to 2,376 in 2015. Head/neck was the most frequently examined body anatomical region for all age groups, except for patients aged 15-19 years for whom abdomen/pelvis was the most common scanned region. One third of the patients underwent more than one CT examination in the hospital during the study period, with multiple CT exams increasing with patient age. The greater availability of other diagnostic imaging examinations in the private setting, such as magnetic resonance and ultrasound, could have contributed to the lower proportion of pediatric and young adult CT in the study hospital. The rapid increase of pediatric CT usage in the public and private healthcare setting reinforces the need for initiatives to avoid unwarranted CT exposure in Brazil.