Towards 6D Little String Theory of Particles

A model for particles based on preons in chiral, vector and tensor/graviton supermultiplets of unbroken global supersymmetry is engineered. The framework of the model is little string theory. Phenomenological predictions are discussed.

The Fate of Supersymmetry in Quantum Field Theories

We analyze the significance of supersymmetry in two topological models and the standard model (SM). We conclude that the two topological field theory models favor hidden supersymmetry. The SM superpartners, instead, have not been found.

Recent progress of CERN RD50 Collaboration

The objective of the CERN RD50 Collaboration is to develop radiation hard semiconductor detectors for very high luminosity colliders, in particular, for the upgrade of the large hadron collider (LHC) which itself is scheduled to be operational in 2007. The approach of the RD50 has two major research lines, material engineering and device engineering. These are further subdivided into projects covering defect characterization and engineering, new detector materials, detector characterization, new detector structures and full detector systems. Presently, 264 members from 53 institutes are actively participating in the RD50 Collaboration. Detectors made of defect engineered substrates, e.g. high resistivity magnetic Czochralski (MCz-Si), epitaxial silicon (Epi-Si) on Czochralski silicon (Cz-Si) substrate, intentionally thermal donor (TD) compensated p-type MCz-Si and oxygen enriched (DOFZ) silicon, have been demonstrated by the RD50 Collaboration. An overview and highlights of the results of these defect engineering techniques were given in this report.

Recent progress of CERN 39-cryogenic tracking detectors collaboration

Significant progress was made by the CERN RD39 collaboration in the development of super radiation-hard cryogenic silicon detectors for applications in experiments at LHC, in particular after its future luminosity upgrade. The detailed modeling shows that the electric field in irradiated silicon detectors can easily be manipulated by the filling state of two deep defect levels at cryogenic temperature. Advanced radiation hard detectors using charge or current injection and the current injected detectors(CID) were developed by RD39. The results show that CID detectors can be operated at the temperature of 100?200 K with much improved charge collection efficiency(CCE) as compared with RT operation. Future studies are developing ultra-hard cryogenic silicon detectors for the LHC upgrade, where the radiation hardness is required up to 1016 neq/cm2, at which trapping will limit the charge collection depth to the range of 20 to 50 μm regardless of the depletion depth. The key of our approach is to use freeze-out trapping to affect CCE.

Density functional theory calculation of the properties of carbon vacancy defects in silicon carbide

As a promisingmaterial for quantumtechnology,silicon carbide(SiC)has attracted great interest inmaterials science.Carbon vacancy is a dominant defect in 4H-SiC.Thus,understanding the properties of this defect is critical to its application,and the atomic and electronic structures of the defects needs to be identified.In this study,density functional theorywas used to characterize the carbon vacancy defects in hexagonal(h)and cubic(k)lattice sites.The zero-phonon line energies,hyperfine tensors,and formation energies of carbon vacancies with different charge states(2−,−,0,+and 2+)in different supercells(72,128,400 and 576 atoms)were calculated using standard Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof methods.Results show that the zero-phonon line energies of carbon vacancy defects are much lower than those of divacancy defects,indicating that the former is more likely to reach the excited state than the latter.The hyperfine tensors of VC+(h)and VC+(k)were calculated.Comparison of the calculated hyperfine tensor with the experimental results indicates the existence of carbon vacancies in SiC lattice.The calculation of formation energy shows that the most stable carbon vacancy defects in the material are VC 2+(k),VC+(k),VC(k),VC−(k)and VC 2−(k)as the electronic chemical potential increases.

Angular dependence of nanoparticle generation in the matrix assembly cluster source

The matrix assembly cluster source(MACS)represents a bridge between conventional instruments for cluster beam deposition(CBD)and thelevel of industrial production.The method is based on Ar^+ion sputtering of a pre-condensed Ar-M matrix(where M,is typically a metal such asAg).Each Ar^+ion produces a collision cascade and thus the formation of metal clusters is in the matrix,which are then sputtered out.Here wepresent an experimental and computational investigation of the cluster emission process,specifically its dependence on the Ar^+ion angle of in cidence and the cluster emission angle.We find the in cide nee angle strongly in flue nces the emerging cluster flux,which is assigned to thespatial location of the deposited primary ion energy relative to the cluster into the matrix.We also found an approximately constant anglebetween the incident ion beam and the peak in the emitted cluster distribution,with value between 99°and 109°.

Energy budget of cosmological first-order phase transition in FLRW background

We study the hydrodynamics of bubble expansion in cosmological first-order phase transition in the Friedmann-Lema??treRobertson-Walker(FLRW) background with probe limit. Different from previous studies for fast first-order phase transition in flat background, we find that, for slow first-order phase transition in FLRW background with a given peculiar velocity of the bubble wall, the efficiency factor of energy transfer into bulk motion of thermal fluid is significantly reduced, thus decreasing the previously-thought dominated contribution from sound wave to the stochastic gravitational-wave background.

Complex Ga_(2)O_(3) polymorphs explored by accurate and general-purpose machine-learning interatomic potentials

Ga_(2)O_(3) is a wide-band gap semiconductor of emergent importance for applications in electronics and optoelectronics.However,vital information of the properties of complex coexisting Ga_(2)O_(3) polymorphs and low-symmetry disordered structures is missing.We develop two types of machine-learning Gaussian approximation potentials(ML-GAPs)for Ga_(2)O_(3) with high accuracy forβ/κ/α/δ/γpolymorphs and generality for disordered stoichiometric structures.We release two versions of interatomic potentials in parallel,namely soapGAP and tabGAP,for high accuracy and exceeding speedup,respectively.Both potentials can reproduce the structural properties of all the five polymorphs in an exceptional agreement with ab initio results,meanwhile boost the computational efficiency with 5×102 and 2×105 computing speed increases compared to density functional theory,respectively.Moreover,the Ga_(2)O_(3) liquid-solid phase transition proceeds in three different stages.This experimentally unrevealed complex dynamics can be understood in terms of distinctly different mobilities of O and Ga sublattices in the interfacial layer.

Five-quark components in baryons

While several experiments based on the Drell-Yan process have revealed the presence of light antiquarks in the proton,the experimental signatures for strange quark components remain consistent with 0.Phenomenological studies of meson photoproduction on nucleons with hadronic models indicate that the underprediction of the NΔ transition strengths by the three quark model may be attributed to the missing 'meson cloud' contributions.If qqqqq configurations are included in the baryon wave functions the conclusions that emerge are that (a) a combination of at least three different qqqqq configurations are required for a satisfactory description of the nucleon properties and (b) that the vanishing of the axial form factor of the N(1535) resonance is a natural consequence of the cancellation of the contributions of the qqq and qqqqq configurations.

Time-dependent Calculations for Two-proton Decay Width with Schematic Density-dependent Contact Pairing Interaction

We calculate the two-proton decay width of the6 Be nucleus employing the schematic densitydependent contact potential for the proton-proton pairing interaction. The decay width is calculated with a time-dependent method, in which the two-proton emission is described as a time-evolution of a threebody meta-stable state. Model-dependence of the two-proton decay width has been shown by comparing the results obtained with the two different pairing models, schematic density-dependent contact and Minnesota interactions, which have zero and finite ranges, respectively.