arXiv subjects
Publications and source records attributed to M. Majewski.
Silicon detectors operating in the harsh mixed-hadron radiation environment of modern high-energy physics experiments suffer progressive bulk damage, manifesting macroscopically as a steady rise in leakage current.
The active layer in a perovskite solar cell is usually composed of a polycrystalline thin film. Fabrication of this layer by solution processing is a promising candidate for up-scaling to the mass market. However, the evolution of an evaporating and simultaneously crystallizing thin film is not yet fully understood. To contribute to the understanding of the formation of thin films, we develop a geometrical model that deals with the effect of the interplay between solvent evaporation and crystal growth on the dry film morphology. The possible film formation mechanisms are investigated, depending on the processing conditions. We find eleven formation pathways leading to four distinct morphologies. It is shown how these formation pathways can be utilized by adapting the process parameters to the material properties. Pinhole-free and flat films can be fabricated if the evaporation rate is high in comparison to the crystal growth rate. Alternatively, providing a high crystal number density on the substrate can lead to the desired film morphology at low drying rates. The generality of the model makes it applicable to any evaporating and simultaneously crystallizing thin film.
Perovskite solar cells (PSC) are promising potential competitors to established photovoltaic technologies due to their superior efficiency and low-cost solution processability. However, the limited understanding of the crystallization behaviour hinders the technological transition from lab-scale cells to modules. In this work, we perform Phase Field (PF) simulations of the doctor-bladed film formation to obtain mechanistic and morphological information that is experimentally challenging to access. PF simulations are validated extensively using in- and ex-situ experiments for different solvent evaporation rates. The well-known transition from a film with many pinholes, for a low evaporation rate, to a smooth film, for high evaporation rates, is recovered in simulation and experiment. From the simulation, the transition can be assigned to the change in the ratio of evaporation to crystallization rate because of two distinct mechanisms. Firstly, for larger evaporation rates, nuclei appear at higher concentrations, which favors nucleation as compared to growth. Secondly, the growth of the crystals is confined in a thinner film, which limits their vertical size. Both effects are expected to be valid independent of the specific chemistry of the chosen experimental system, as long as the evaporation time of the solvent is comparable to the crystallization time.
The purpose of this study is to inspect the combined effect of reinforcement shape and packing on the macroscopic behaviour of particulate composites. The introduced micromechanical approach modifies the Morphologically Representative Pattern scheme with the Replacement Mori-Tanaka Model. The statistical volume elements have randomly placed inclusions with a selected shape. Four shapes of inhomogeneities are studied: a sphere, a prolate spheroid, three prolate spheroids crossing at right angles, and a drilled spheroid. The concentration tensors of non-ellipsoidal inhomogeneities are found numerically using simple simulations of a single particle. The extension to the regime of non-linear material behaviour is performed by employing the tangent or secant incremental linearization of the material response. The results are compared with the outcomes of numerical simulations and predictions of the classical mean-field models based on the Eshelby solution, e.g., the Mori-Tanaka model or the Self-Consistent scheme. It is found that the proposed modification of the Morphologically Representative Pattern approach can be used as an alternative to computational homogenization in the case of elastic-plastic composites with different shapes and packings of particles.
The Large Hadron Collider beauty (LHCb) detector is designed to detect decays of b- and c- hadrons for the study of CP violation and rare decays. At the end of the LHC Run 2, many of the LHCb measurements remained statistically dominated. In order to increase the trigger yield for purely hadronic channels, the hardware trigger will be removed, and the detector will be read out at 40 MHz. This, in combination with the five-fold increase in luminosity, requires radical changes to LHCb's electronics, and, in some cases, the replacement of entire sub-detectors with state-of-the-art detector technologies. The Vertex Locator (VELO) surrounding the interaction region is used to reconstruct the collision points (primary vertices) and decay vertices of long-lived particles (secondary vertices). The upgraded VELO will be composed of 52 modules placed along the beam axis divided into two retractable halves. The modules will each be equipped with 4 silicon hybrid pixel tiles, each read out by 3 VeloPix ASICs. The total output data rate anticipated for the whole detector will be around 1.6 Tbit/s. The highest occupancy ASICs will have pixel hit rates of approximately 900 Mhit/s, with the corresponding output data rate of 15 Gbit/s. The LHCb upgrade detector will be the first detector to read out at the full LHC rate of 40 MHz. The VELO upgrade will utilize the latest detector technologies to read out at this rate while maintaining the required radiation-hard profile and minimizing the detector material.
The pseudoscalar mesons with the masses higher than 1 GeV are assumed to belong to the meson decuplet including the glueball as the basis state supplementing the standard $SU(3)_F$ nonet of light $q\bar{q}$ states $(u,d,s)$. The decuplet is investigated by means of an algebraic approach based on hypothesis of vanishing the exotic $SU(3)_F$ commutators of "charges" and their time derivatives. These commutators result in a system of equations determining contents of the isoscalar octet state in the physical isoscalar mesons as well as the mass formula including all masses of the decuplet: $\pi(1300)$, K(1460), $\eta(1295)$, $\eta(1405)$ and $\eta(1475)$. The physical isoscalar mesons $\eta_i$, are expressed as superpositions of the "ideal" $q\bar{q}$ states ($N$ and $S$) and the glueball $G$ with the mixing coefficient matrix following from the exotic commutator restrictions. Among four one-parameter families of the calculated mixing matrix (numerous solutions result from bad quality of data on the $\pi(1300)$ and K(1460) masses) there is one family attributing the glueball-dominant composition to the $\eta(1405)$ meson. Similarity between the pseudoscalar and scalar decuplets, analogy between the whole spectra of the $0^{-+}$ and $0^{++}$ mesons and affinity of the glueball with excited $q\bar{q}$ states are also noticed.
In this paper we compute the square lattice random sites percolation thresholds in case when sites from the 4th and the 5th coordination shells are included for neighbourhood. The obtained results support earlier claims, that (a) the coordination number and the space dimension are insufficient for building universal formulae for percolation thresholds and (b) that percolation threshold may not decrease monotonically with lattice site coordination number.
The relation between the ratio Gamma_{ee}(psi')/Gamma_{ee}(J/psi) and Gamma_{2gamma}(eta_{c}')/Gamma_{2gamma}(eta_{c}), expressed in terms of the configuration mixing amplitudes induced by the contact spin-spin interaction of quarks in the ground and radial excitation states, is shown to give, after the inclusion of the newly derived relativistic corrections, the radiative eta_{c}'- and η_c-width ratio in fair accord with recent experiments. The dynamical model is proposed to derive the ratio of relative probability of the ground (eta_{c}(2980))- and first radial excitation (eta_{c}'(3640))-state formation in gamma-gamma collisions followed by their decay into the pi\bar{K}K and p\bar{p} channels.
We compare the virtues of two options for the isospin (I=1 or 2) of the apparently exotic dibarion resonance d_1^*(1956), as it is noticed by the DIB2gamma Collaboration (JINR) in the reaction pp -> 2 gamma X below the pion threshold, and using recent results following from the RMC Collaboration (TRIUMF) measurement of the relative probability of the double-photon pion capture in the pi-mesic deuterium atoms.
It is shown that the symmetry algebra of quantum superintegrable system can be always chosen to be u(N),N being the number of degrees of freedom.
The amplitudes of hadron-hadron forward elastic scattering at high energy a re investigated on the basis of analiticity and crossing-symmetry which is valid in QCD. The universal uniformizing variable for them is proposed and the formulae for crossing-even and crossing-odd amplitudes are derived. The same parameters in these formulae determine the real and imaginary (total cross sections) parts of the amplitudes. The analysis of the parameters determined from experimental data clearly points to the quark-gluon stracture of hadrons. The total cross sections for hyperon-proton scattering are predicted. They are consistent with experimental data and, in particular, with the new SELEX-collaboration measurement $σ_{tot}(Σ^{-} p)$.
Two properties of Calogero wave functions for rational Calogero models are studied: (i) the representation of the wave functions in terms of the exponential of Lassalle operators, (ii) the $sL(2,\rr)$ structure of the Calogero--Moser wave functions.
The Calogero model with negative harmonic term is shown to be equivalent to the set of negative harmonic oscillators. Two time-independent canonical transformations relating both models are constructed: one based on the recent results concerning quantum Calogero model and one obtained from dynamical $sL(2,\rr)$ algebra. The two-particle case is discussed in some detail.
Some experiments on LEAR obtained unusual behavior of the $p\bar p$ interaction near the threshold. The experiments on $p\bar p$ forvard scattering detected zeros and big variation of $\rho$ and at the same time a smooth rising of ${\sigma}_{tot}$ with lowing energy. Many models has difficulties in explanating this fact. In the PS170 experiment with a good statistical accuracy the unexpected behavior of the proton electromagnetic form factor was found. All these experiments can be considered as an indication for the existence of a low lying $p\bar p$ bound state 'baryonium'. This statement coincides with that made for interpretation of the energy dependence of the total cross-section $e^{+}e^{-}\to hadrons$ in FENICE. There is a model (based on analyticity) which explained aforementioned experiments and the fact that this 'baryonium' is not seen in the OBELIX $p\bar p$ annihilation cross-section. Thus LEAR experiments and FENICE one are consistent near $p\bar p$ threshold and compatible with the existence of 'baryonium'.
On the basis of the relation between values of the coupling constants determined from data fit it is concluded that the dominating constituent of the $Θ$ meson is the glueball. The possibility that $Θ$ meson decays into two $σ(750)$ mesons is suggested.
The representations of the oscillator algebra introduced by Brzezinski et al. (Phys. Lett. B 311 (1993), 202) are classified.