Risk assessment for the installation and maintenance activities of a low-speed tidal energy converter

The study presented in this paper, is part of the Deep Green project, which includes the development of a power converter/device for employment in low-speed tidal currents. It mainly focuses on the initial steps to investigate the ways on how to minimize the risks during handling, operation and maintenance (O&M) activities of the full-scale device particularly in offshore operations. As a first tep, the full-scale device offshore installation and O&M tasks are considered. The overall risk analysis and decision making methodology is presented including the Hazard Identification (HAZID) approach which is complemented with a risk matrix for various consequence categories including personnel Safety (S), Environmental impact (E), Asset integrity (A) and Operation (O). In this way, all the major risks involved in the mentioned activities are identified and actions to prevent or mitigate them are presented. The results of the HAZID analysis are also demonstrated. Finally, the last section of this paper presents the discussion, conclusions and future actions for the above-mentioned activities regarding the full-scale device

Collider Effects of Unparticle Interactions in Multiphoton Signals

A new model of physics, with a hidden conformal sector which manifests itself as an unparticle coupling to Standard Model particles effectively through higher dimensional operators, predicts strong collider signals due to unparticle self-interactions. We perform a complete analysis of the most spectacular of these signals at the hadron collider, pp -> 4photon and pp ->2photon,2gluon. These processes can go through the three-point unparticle self interactions as well as through some s and t channel diagrams with one and/or two unparticle exchanges. We study the contributions of individual diagrams classified with respect to the number of unparticle exchanges and discuss their effect on the cross sections at the Tevatron and the LHC. We also restrict the Tevatron bound on the unknown coefficient of the three-point unparticle correlator. With the availability of data from Tevatron, and the advent of the data emerging from the LHC, these interactions can provide a clear and strong indication of unparticle physics and distinguish this model from other beyond the standard model scenarios.Comment: 28 pages, 16 figure

Constraints on Dark Photon from Neutrino-Electron Scattering Experiments

A possible manifestation of an additional light gauge boson $A^\prime$, named as Dark Photon, associated with a group $U(1)_{\rm B-L}$ is studied in neutrino electron scattering experiments. The exclusion plot on the coupling constant $g_{\rm B-L}$ and the dark photon mass $M_{A^\prime}$ is obtained. It is shown that contributions of interference term between the dark photon and the Standard Model are important. The interference effects are studied and compared with for data sets from TEXONO, GEMMA, BOREXINO, LSND as well as CHARM II experiments. Our results provide more stringent bounds to some regions of parameter space.Comment: 22 pages, 6 figures, 2 tables, text improved, fig.6 updated, references adde

Rare Decay of the Top t -> cgg in the Standard Model

We calculate the one-loop flavor changing neutral current top quark decay t -> cgg in the Standard Model. We demonstrate that the rate for t -> cgg exceeds the rate for a single gluon emission t -> cg by about two orders of magnitude, while the rate for t -> cq barq (q=u) is slightly smaller than for t -> cg.Comment: 22 pages, 4 figures and 2 tables. Typo in Eq.2.1 corrected, text slightly modified, references added. Version to appear in Phys.Rev.

Rare B_s -> \gamma \nu \bar{\nu} decay with polarized photon and new physics effects

Using the most general, model independent effective Hamiltonian, the rare B_s ->\gamma \nu \bar{\nu} decay with polarized photon is studied. The sensitivity of the branching ratio and photon polarization to the new Wilson coefficients are investigated. It is shown that these physical observables are sensitive to the vector and tensor type interactions, which would be useful in search of new physics.Comment: 9 pages, 5 figure

CP Asymmetry in Charged Higgs Decays in MSSM

We discuss and compare the charge-parity (CP) asymmetry in the charged Higgs boson decays H -> \bar{u}_i d_j for the second and third generation quarks in the minimal supersymmetric standard model. As part of the analysis, we derive some general analytical formulas for the imaginary parts of two-point and three-point scalar one-loop integrals and use them for calculating vectorial and tensorial type integrals needed for the problem under consideration. We find that, even though each decay mode has a potential to yield a CP asymmetry larger than 10%, further analysis based on the number of required charged Higgs events at colliders favors the \bar{t}b, \bar{c}b, and \bar{c}s channels, whose asymmetry could reach 10-15% in certain parts of the parameter space.Comment: 25 pages, 9 figures. Discussion about charged Higgs observability added, typos corrected, accepted for publication in PR

Impact of Sb degrees of freedom on the charge density wave phase diagram of the kagome metal CsV3_3Sb5_5

Elucidating the microscopic mechanisms responsible for the charge density wave (CDW) instability of the AV$_3$Sb$_5$ (A=Cs, K, Rb) family of kagome metals is critical for understanding their unique properties, including superconductivity. In these compounds, distinct CDW phases with wave-vectors at the $M$ and $L$ points are energetically favorable, opening the possibility of tuning the type of CDW order by appropriate external parameters. Here, we shed light on the CDW landscape of CsV$_3$Sb$_5$ via a combination of first-principles calculations and phenomenology, which consists of extracting the coefficients of the CDW Landau free-energy expansion from density functional theory. We find that while the main structural distortions of the kagome lattice in the staggered tri-hexagonal CDW phase are along the nearest-neighbor V-V bonds, distortions associated with the Sb ions play a defining role in the energy gain in this and all other CDW states. Moreover, the coupling between ionic displacements from different unit cells is small, thus explaining the existence of multiple CDW instabilities with different modulations along the c-axis. We also investigate how pressure and temperature impact the CDW phase of CsV$_3$Sb$_5$. Increasing pressure does not change the staggered tri-hexagonal CDW ground state, even though the $M$-point CDW instability disappears before the $L$-point one, a behavior that we attribute to the large nonlinear coupling between the order parameters. Upon changing the temperature, we find a narrow regime in which another transition can take place, toward a tri-hexagonal Star-of-David CDW phase. We discuss the implications of our results by comparing them with experiments on this compound

An application of fuzzy-AHP to ship operational energy efficiency measures

Lowering fuel consumption of ships has gained a great deal of attention in maritime industry with regards to both environmental and economic concerns. The potential for fuel economy in shipping ranging between 25% to 75% is possible by using existing technology and practices and technical improvements in the design of new ship. Despite the existence of many technology and design-based approaches, limitations of emerging these measures has led to discussions about the potential energy savings through operational changes. In this study, operational measures were examined within the scope of Ship Energy Efficiency Management Plan (SEEMP) adopted by International Maritime Organization (IMO). We applied the Analytic Hierarchy Process (Fuzzy-AHP) approach, one of multi-criteria decision making (MCDM) techniques, to prioritize the weight of each measure. Fuzzy AHP effectively reflects the vagueness of human thinking with interval values, and shows the relative importance of operational measures - which can be the fundamental decision making data for decision makers (ships' masters, operating companies and ship owners) - by providing a strategic approach to identify energy efficient solutions

The Casimir Force in Randall Sundrum Models

We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the evaluation of the Casimir force between two parallel plates. We impose the condition that the result reproduce the experimental measurements within the known uncertainties in the force and the plate separation, and get an upper bound kR < 20 if the curvature parameter k of AdS_5 is equal to the Planck scale. Although the upper bound decreases as k decreases, kR ~ 12, which is the required value for solving the hierarchy problem, is consistent with the Casimir force measurements. For the case where the 5th dimension is infinite, the correction to the Casimir force is very small and negligible.Comment: 16 pages, 2 figures, references added, text improved, accepted for publication in PR

Constraining Non-minimal Dark Sector Scenarios with the COHERENT Neutrino Scattering Data

Abelian dark sector scenarios embedded into the two-Higgs doublet model are scrutinized within the Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) experiment, which was first measured by the COHERENT Collaboration in 2017 with an ongoing effort to improve it since then and recently released data for the CsI target in 2022. In the theoretical framework, it is assumed that there is a $U(1)$ gauge group in the dark sector with a non-zero kinetic mixing with the hypercharge field. The COHERENT data for the targets CsI and liquid argon (LAr) are treated in both single and multi bin bases to constrain the multi dimensional parameter space, spanned by the dark gauge coupling, kinetic mixing parameter and the dark photon mass, of totally seven different representative scenarios which are also compared and contrasted among each other to find out about the most sensitive one to the data. The effect of refined quenching factor is also addressed.Comment: 27 pages, 3 tables, 6 figures, references organized and new ones adde