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

Joe Davighi

Abstract We consider extending the Standard Model by an anomaly-free and possibly flavour non-universal U(1) X gauge symmetry, whose breaking gives a Z′ boson that does not affect electroweak precision observables at tree-level or via 1-loop renormalisation group (RG) running. Provided it does not also couple to electrons, such a Z′ boson would be largely invisible to an electroweak precision machine like FCC-ee or CEPC (up to small finite 1-loop matching contributions that we quantify). We show that, while this class of Z′ models can also evade tests of quark flavour violation, the constraint of anomaly-cancellation implies that valence quarks, muons, and taus are all charged under U(1) X , with the up quark charge being necessarily large. The conclusion holds even if one augments the SM by three right-handed neutrinos to try and absorb anomalies. This means such Z′ bosons cannot simultaneously hide below the TeV scale from pp → ℓℓ Drell–Yan measurements at the LHC and, even if we entertain esoteric models in which the lepton charges are numerically very small, we cannot escape dijet searches at the LHC. For equitable quark and lepton charges, pp → ℓℓ already excludes such a Z′ up to M/g ≳ 10 TeV, with a reach of 20 TeV expected by the end of the High-Luminosity LHC. The dijet bounds currently sit around 5 TeV, while sensitivity up to 10 TeV could be achieved at HL-LHC. We thus find an excellent complementarity between FCC-ee and HL-LHC in covering all anomaly-free Z′ bosons up to several TeV.

JIN Rui1, ZHONG Wuye1, , LEI Huazhen1, MA Ru1, QI Lijun1, HAN Yongchao2

In the thermionic energy conversion of Cs-charged, the work function of the electrodes, especially the effective work function of the electrode material in the Cs-absorbing state, has a decisive impact on its power generation performance. However, it is difficult to measure the work function in the high-temperature Cs environment for the test method at this stage, so establishing relevant experimental methods to evaluate the work function of the electrode material in the real environment is necessary. Based on the energy balance equation of electron flow between electrodes in thermionic energy conversion, combined with the local characteristics of electrode influence in the thermoelectric conversion process, the indirect measurement method of the effective work function of the emitter and collector was established by processing the current-volt characteristic curves under specific operating parameters. Furthermore, the data processing program was compiled by Matlab language, then the effective work function of the electrode material at different temperatures could be directly output. A series of current-volt characteristic data were obtained by using the current-volt characteristic program in the literature, and the current-volt characteristic data of Ni with only changing the temperature of the collector were tested by using a self-built plate-electrode experimental device. The parameters such as current density, voltage and electrode temperature in the current-volt characteristic results were substituted into the effective work function calculation model. The effective work functions of W emitter and Ni collector under different power generation currents under specific operating conditions subsequently were calculated separately, compared with the test values of the Cs-absorbing work function tested in the literature, which not measured under arc conditions during power generation. The results show that the effective work function of the emitter is approximately positively correlated with the Rasor index, decreasing with the increase of current density, which is caused by the Schottky effect. The changes of the effective work function of the collector with the working condition are consistent with the change trend of the influence of the collector temperature on the output power. Furthermore, there is an optimal collector temperature, in the vicinity of which the effective work function is the lowest. The average relative errors of the effective work functions of the emitter and collector and the literature values of the Cs-absorbing work function are 5.74% and 3.86%, respectively. The indirect measurement results of the effective work function can be consistent with the power generation characteristics of the thermionic energy conversion, which could be reflected in the previous test results of the Cs-absorbing work function.

Zhengbao Wei, Yongbo Huang, Yaping Cheng

Abstract The moon is continuously bombarded by cosmic rays, primarily Galactic Cosmic Rays (GCR) and Solar Cosmic Rays, which generate complex secondary radiation in the lunar subsurface. Secondary radiation is a critical factor that must be considered in the design of radiation protection for future manned lunar missions and the construction of lunar research bases. Based on previous studies, this study employs the Geant4 to simulate the secondary radiation produced by nuclei from hydrogen to nickel in GCR, with a particular focus on the neutron number density and flux at a depth of 10 ms below the lunar surface. The results indicate that when the abundance of heavy elements from lithium to nickel in GCR is less than 1%, their contribution to the neutron number density exceeds 6%. Additionally, we analyzed the leakage fluxes of neutrons, gamma rays, protons, and electrons during the months of strongest and weakest solar modulation from 1951 to 2016. The total neutron leakage fluxes were 1.59 n/ $$\hbox {cm}^2$$ cm 2 -s and 3.85 n/ $$\hbox {cm}^2$$ cm 2 -s, respectively, with the leakage flux proportions of the three neutron types all below 2%. Furthermore, we simulated the total leakage of neutrons and gamma rays in the energy range of 10−9 to 104 MeV during the second extreme Solar Energetic Particle (SEP) event in 2003, which lasted for 33 h. The neutron leakage during this event was 4.6 times and 1.9 times higher than during the months of strongest and weakest solar modulation, respectively; while the gamma ray leakage was 14.5 times and 6.6 times higher, respectively.

Károly Seller, Zsolt Szép, Zoltán Trócsányi

Abstract We present in the conventional equilibrium approach to leptogenesis the complete leading order prediction for the CP asymmetry factor in finite-temperature decays involving Majorana neutrinos. As thermal effects are generally not negligible, the knowledge of the high temperature behavior of the underlying particle physics model, in particular that of mass generation, is required for reliable estimates of matter–antimatter asymmetry through the mechanism of leptogenesis. We present all necessary information needed to obtain the full one-loop evaluation for the thermal CP asymmetry factors for the processes $$N_i\rightarrow \phi + L$$ N i → ϕ + L and $$\phi \rightarrow N_i+L$$ ϕ → N i + L at temperatures where they are kinematically allowed. We present a numerical comparison with previous formulae given in the literature.

Yi-Yao Li, Jing Song, Eulogio Oset et al.

Abstract We study the decay $$\Lambda _c^+ \rightarrow \Lambda \pi ^+ \pi ^+ \pi ^-$$ Λ c + → Λ π + π + π - , focusing on the production of the $$\Sigma ^*(1430)$$ Σ ∗ ( 1430 ) resonance observed by the Belle Collaboration. Interpreted as a dynamically generated state from meson-baryon interactions in the chiral unitary approach, the $$\Sigma ^*(1430)$$ Σ ∗ ( 1430 ) signal is shown to be enhanced by a triangle singularity involving intermediate $$K^{*-}$$ K ∗ - , p, and $${\bar{K}}^0$$ K ¯ 0 states. This mechanism leads to a sharp peak near 1434 MeV in the $$\pi ^+ \Lambda $$ π + Λ invariant mass distribution, in agreement with the experimental observations, and predicts a secondary peak around 1875 MeV in the $$\pi ^- \Sigma ^*(1430)$$ π - Σ ∗ ( 1430 ) spectrum tied to the triangle singularity. We also estimate the branching ratio of $$\Lambda _c^+ \rightarrow \pi ^+ \pi ^- \Sigma ^*(1430)$$ Λ c + → π + π - Σ ∗ ( 1430 ) to be about $$3.5 \times 10^{-4}$$ 3.5 × 10 - 4 . The results for the branching ratio and the $$\pi ^- \Sigma ^*(1430)$$ π - Σ ∗ ( 1430 ) mass distributions are predictions of the theoretical approach, which could be tested with reanalysis of existing data.

Y. Pulnova, T. Parkman, B. Angelov et al.

In this work, experimentally measured characteristics of a kilohertz laser-driven Cu plasma X-ray source that was recently commissioned at the ELI Beamlines facility are reported. The source can be driven either by an in-house developed high-contrast sub-20 fs near-infrared terawatt laser based on optical parametric chirped-pulse amplification technology or by a more conventional Ti:sapphire laser delivering 12 mJ and 45 fs pulses. The X-ray source parameters obtained with the two driving lasers are compared. A measured photon flux of the order up to 1012 Kα photons s−1 (4π)−1 is reported. Furthermore, experimental platforms for ultrafast X-ray diffraction and X-ray absorption and emission spectroscopy based on the reported source are described.

David Senjaya

Abstract The current work looks at the quasibound states and scalar cloud of relativistic charged scalar fields in an intense Kerr–Newman black hole. The absence of numerical techniques for solving the Klein–Gordon equation in the presence of extremal black holes is a well-known issue. Due to the difficulties, the numerical study is forced to end at the near-extreme limit. We discover a new exact quasibound state solution in the extreme Kerr–Newman black hole in terms of the Double Confluent Heun function. A series termination condition (quantization formula) is obtained by imposing the polynomial conditions of the Double Confluent Heun function and quasibound state boundary conditions, i.e., an ingoing wave near the black hole’s horizon and vanishing asymptotically far away from the black hole. Using the obtained quantization formula, we investigate the existence of a charged scalar cloud’s resonance frequency and discover that it is inexistent in the extreme Kerr–Newman black hole spacetime.

R. Zaplotnik, A. Drenik, A. Vesel et al.

Production of ammonia by surface reactions of H and N atoms on surfaces not wetted by partially ionized plasma may represent an important technological issue in fusion reactors where puffing nitrogen is employed to cool plasma in the divertor region. The H and N atoms are likely to interact on such surfaces forming NH3 molecules. The interaction efficiency was studied in a laboratory setup consisting of two separate sources of either N or H atoms. Both sources enabled experiments with atoms at room temperature in the range of H-atom density of the order of 10 ^21 m ^−3 and N-atom density of the order of 10 ^20 m ^−3 . The production of ammonia was measured with a calibrated residual gas analyser. The production depended on the fluxes of both atoms onto the surface of selected materials. As a general rule, the higher H-atom flux at a constant N-atom flux caused an increase in ammonia production. The highest efficiency of up to 50% was found for nickel. It was up to 30% for tungsten, whereas for P92 alloy, it was up to about 20%. The accuracy of these results is within about ±20% of the measured values. Methods for suppressing ammonia formation in fusion reactors will have to be invented in order to enable appropriate long-term operation.

E. Sánchez, J.L. Velasco, I. Calvo et al.

Sunny Vagnozzi

The Hubble tension has now grown to a level of significance which can no longer be ignored and calls for a solution which, despite a huge number of attempts, has so far eluded us. Significant efforts in the literature have focused on early-time modifications of <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM, introducing new physics operating prior to recombination and reducing the sound horizon. In this opinion paper I argue that early-time new physics <i>alone</i> will always fall short of fully solving the Hubble tension. I base my arguments on seven independent hints, related to (1) the ages of the oldest astrophysical objects, (2) considerations on the sound horizon-Hubble constant degeneracy directions in cosmological data, (3) the important role of cosmic chronometers, (4) a number of “descending trends” observed in a wide variety of low-redshift datasets, (5) the early integrated Sachs-Wolfe effect as an early-time consistency test of <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Λ</mi></semantics></math></inline-formula>CDM, (6) early-Universe physics insensitive and uncalibrated cosmic standard constraints on the matter density, and finally (7) equality wavenumber-based constraints on the Hubble constant from galaxy power spectrum measurements. I argue that a promising way forward should ultimately involve a combination of early- and late-time (but non-local—in a cosmological sense, i.e., at high redshift) new physics, as well as local (i.e., at <inline-formula><math display="inline"><semantics><mrow><mi>z</mi><mo>∼</mo><mn>0</mn></mrow></semantics></math></inline-formula>) new physics, and I conclude by providing reflections with regards to potentially interesting models which may also help with the <inline-formula><math display="inline"><semantics><msub><mi>S</mi><mn>8</mn></msub></semantics></math></inline-formula> tension.

Nina M. Coyle, Carlos E. M. Wagner

Abstract The QED hadronic vacuum polarization function plays an important role in the determination of precision electroweak observables and of the anomalous magnetic moment of the muon. These contributions have been computed from data, by means of dispersion relations affecting the electron positron hadronic cross sections, or by first principle lattice-QCD computations in the Standard Model. Today there is a discrepancy between the two approaches for determining these contributions, which affects the comparison of the measurement of the anomalous magnetic moment of the muon with the theoretical predictions. In this article, we revisit the idea that this discrepancy may be explained by the presence of a new light gauge boson that couples to the first generation quark and leptons and has a mass below the GeV scale. We discuss the requirements for its consistency with observations and the phenomenological implications of such a gauge extension.

CAI Boshuai;YU Tianjun;LIN Xuan;ZHANG Jilong;WANG Zhixuan;YUAN Cenxi

The random forest algorithm was applied to study the nuclear binding energy and charge radius. The regularized root-mean-square of error (RMSE) was proposed to avoid overfitting during the training of random forest. RMSE for nuclides with Z, N>7 is reduced to 0.816 MeV and 0.020 0 fm compared with the six-term liquid drop model and a three-term nuclear charge radius formula, respectively. Specific interest is in the possible (sub) shells among the superheavy region, which is important for searching for new elements and the island of stability. The significance of shell features estimated by the so-called shapely additive explanation method suggests (Z, N)=(92, 142) and (98, 156) as possible subshells indicated by the binding energy. Because the present observed data is far from the N=184 shell, which is suggested by mean-field investigations, its shell effect is not predicted based on present training. The significance analysis of the nuclear charge radius suggests Z=92 and N=136 as possible subshells. The effect is verified by the shell-corrected nuclear charge radius model.

Liang Zhao, Enrico Landi, Susan T. Lepri et al.

The exact coronal origin of the slow-speed solar wind has been under debate for decades in the Heliophysics community. Besides the solar wind speed, the heavy ion composition, including the elemental abundances and charge state ratios, are widely used as diagnostic tool to investigate the coronal origins of the slow wind. In this study, we recognize a subset of slow speed solar wind that is located on the upper boundary of the data distribution in the O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>7</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>/O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula> versus C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>/C<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>5</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula> plot (O-C plot). In addition, in this wind the elemental abundances relative to protons, such as N/P, O/P, Ne/P, Mg/P, Si/P, S/P, Fe/P, He/P, and C/P are systemically depleted. We compare these winds (“upper depleted wind” or UDW hereafter) with the slow winds that are located in the main stream of the O-C plot and possess comparable Carbon abundance range as the depletion wind (“normal-depletion-wind”, or NDW hereafter). We find that the proton density in the UDW is about 27.5% lower than in the NDW. Charge state ratios of O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>7</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>/O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>6</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>, O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>7</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>/O, and O<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mn>8</mn><mo>+</mo></mrow></msup></semantics></math></inline-formula>/O are decreased by 64.4%, 54.5%, and 52.1%, respectively. The occurrence rate of these UDW is anti-correlated with solar cycle. By tracing the wind along PFSS field lines back to the Sun, we find that the coronal origins of the UDW are more likely associated with quiet Sun regions, while the NDW are mainly associated with active regions and HCS-streamer.

The CMS collaboration, A. Tumasyan, W. Adam et al.

Jarah Evslin

Abstract In a soliton sector of a quantum field theory, it is often convenient to expand the quantum fields in terms of normal modes. Normal mode creation and annihilation operators can be normal ordered, and their normal ordered products have vanishing expectation values in the one-loop soliton ground state. The Hamiltonian of the theory, however, is usually normal ordered in the basis of operators which create plane waves. In this paper we find the Wick map between the two normal orderings. For concreteness, we restrict our attention to Schrodinger picture scalar fields in 1+1 dimensions, although we expect that our results readily generalize beyond this case. We find that plane wave ordered n-point functions of fields are sums of terms which factorize into j-point functions of zero modes, breather and continuum normal modes. We find a recursion formula in j and, for products of fields at the same point, we solve the recursion formula at all j.

LIANG Qixuan;ZHANG Feng;TAN Haizhou;FAN Jilin;LI Xianghui

The quantitative interpretation of remaining oil saturation has a great significance for improving oil production and guiding the follow-up development of oil fields. The characteristic gamma rays are recorded to determine the remaining oil saturation, which is from the interaction of high energy neutron emitted by the pulsed neutron logging tool and the element of carbon and oxygen. The interpretation results of the remaining oil saturation are affected by the mineral composition of rock and clay types. In order to understand the influence of lithology on the inelastic gamma ratio of carbon to oxygen and the capture gamma ratio of silicon and calcium, the MCNP was employed to obtain the gamma energy spectrum response of formation with different lithology, porosity and saturation. The results show that when the difference of C/O is calculated by the traditional interpretation model, the influence of lithology on C/O difference results in the interpretation error of remaining oil saturation. So an improved interpretation model was proposed to enhance the precision of saturation by introducing the lithological effects. Meanwhile, the results of the simulation example and field example show that the improved C/O interpretation model guarantees the saturation interpretation accuracy requirements of the sandstone formation and the error of calculation saturation is less than 10% in the mixed formation.

Giuseppe Gaetano Luciano, Luciano Petruzziello

Abstract We exhibit a theoretical calculation of the parameter $$\beta $$ β appearing in the generalized uncertainty principle (GUP) with only a quadratic term in the momentum. A specific numerical value is obtained by comparing the GUP-deformed Unruh temperature with the one predicted within the framework of Caianiello’s theory of maximal acceleration. The physical meaning of this result is discussed in connection with constraints on $$\beta $$ β previously fixed via both theoretical and experimental approaches.

Fabio Ludolf Cacais, José Ubiratan Delgado, Victor Manuel Loayza et al.

The dissemination of the activity is performed from radionuclide sources prepared in a sequence of dilutions and weighing methods. In this process, the activity of the source can be estimated statistically from the deposited mass and the activity concentration of the master solution. After preparation, the activity is obtained from absolute or relative measurement methods. However, the methods of activity determinations used may not fulfill the necessary independence of the conventional statistical approach due to the presence of possible correlations between activities that arise with the use of the same standardized sources or with the same method of quantity measurements. In this paper, Bayesian estimates for the relative deviation of activities and their uncertainty were obtained in order to evaluate the performance of the main sources’ preparation method. The estimate result (0.55 ± 0.27) % for a data set of radionuclide standardization performed between 2017 and 2018 at LNMRI, although close to zero, shows one should investigate possible effects affecting the preparation and measurement of the sources. This Bayesian estimate was validated by monte carlo simulation method.

Tuan Q. Do, W. F. Kao

Abstract We will study the cosmological implications of the five dimensional scalar–vector and scalar-Kalb–Ramond model. In particular, a new set of Bianchi type I power-law analytic solution will be obtained for this model. The cosmic no-hair conjecture can be shown to break down in the presence of the scalar–vector and scalar-Kalb–Ramond couplings. The effect of the Kalb–Ramond field in the presence of the power-law solution will be shown explicitly. We will also show that the presence of a phantom field does, however, destabilize the corresponding Bianchi type I power-law inflationary solutions.

Kei-Ichi Kondo

Abstract For the Yang–Mills theory coupled to a single scalar field in the fundamental representation of the gauge group, we present a gauge-independent description of the Brout–Englert–Higgs mechanism by which massless gauge bosons acquire their mass. The new description should be compared with the conventional gauge-dependent description relying on the spontaneous gauge symmetry breaking due to a choice of the non-vanishing vacuum expectation value of the scalar field. In this paper we focus our consideration on the fundamental scalar field which extends the previous work done for the Yang–Mills theory with an adjoint scalar field. Moreover, we show that the Yang–Mills theory with a gauge-invariant mass term is obtained from the corresponding gauge-scalar model when the radial degree of freedom (length) of the scalar field is fixed. The result obtained in this paper is regarded as a continuum realization of the Fradkin–Shenker continuity and Osterwalder–Seiler theorem for the complementarity between Higgs regime and Confinement regime which was given in the gauge-invariant framework of the lattice gauge theory. Moreover, we discuss how confinement is investigated through the gauge-independent Brout–Englert–Higgs mechanism by starting with the complementary gauge-scalar model.