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Performance of the Belle II Electromagnetic Calorimeter in First Data
No full textThe Belle II experiment at the SuperKEKB electron-positron collider in Tsukuba, Japan began physics data taking in 2019 and will search for new physics in the flavour sector of the Standard Model as well as for dark sectors. The Belle II electromagnetic calorimeter plays a central role in photon, neutral pion and neutral hadron reconstruction, in addition to enabling advanced triggering techniques to give Belle II improved sensitivities to unique signatures of potential new physics. The calorimeter is constructed from 8736 CsI(Tl) scintillator crystals which have been equipt with new waveform sampling electronics to maintain high performance while operating in the intense beam background environment produced by SuperKEKB. This talk will present measurements of the photon and neutral pion reconstruction performance during the first physics data-taking runs of Belle II in addition to results of the first application of CsI(Tl) pulse shape discrimination at a B-Factory experiment. Through the application of pulse shape discrimination, it will be demonstrated that improvements are achieved in challenging and important areas of particle identification such as neutral hadron vs. photon identification and low momentum charged particle identification
Evolution of parton showers and parton distribution functions
No full textInitial state evolution in parton shower event generators involves parton distribution functions. We examine the probability for the system to evolve from a higher scale to a lower scale without an initial state splitting. A simple argument suggests that this probability, when multiplied by the ratio of the parton distributions at the two scales, should be independent of the parton distribution functions. We call this the PDF property. We examine whether the PDF property actually holds using pythia and deductor. We also test a related property for the deductor shower and discuss the physics behind the results
Photoionization of Astrophysically Relevant Atomic Ions at PIPE
No full textWe review recent work on the photoionization of atomic ions of astrophysical interest that has been carried out at the photon-ion merged-beams setup PIPE, a permanently installed end station at the XUV beamline P04 of the PETRA III synchrotron radiation source operated by DESY in Hamburg, Germany. Our results on single and multiple -shell photoionization of Fe, Fe, and Fe ions and on single and multiple -shell photoionization of C, C, C, Ne, and Si ions are discussed in astrophysical contexts. Moreover, these experimental results bear witness of the fact, that the implementation of the photon-ion merged-beams method at one of the world's brightest synchrotron light sources has led to a breakthrough for the experimental study of atomic inner-shell photoionization processes with ions
Evidence for a vector charmonium-like state in +c.c.
No full textWe report the measurement of e+e−→D+sD∗s2(2573)−+c.c. via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb−1 collected with the Belle detector at the Υ(4S) and nearby. We find evidence for an enhancement with a 3.4σ significance in the invariant mass of D+sD∗s2(2573)−+c.c. The measured mass and width are (4619.8+8.9−8.0(stat.)±2.3(syst.)) MeV/c2 and (47.0+31.3−14.8(stat.)±4.6(syst.)) MeV, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmoniumlike state at 4626 MeV/c2 recently reported by Belle in e+e−→D+sDs1(2536)−+c.c. The product of the e+e−→D+sD∗s2(2573)−+c.c. cross section and the branching fraction of D∗s2(2573)−→¯D0K− is measured from D+sD∗s2(2573)− threshold to 5.6 Ge
Evidence for produced in single-tag two-photon interactions
No full textWe report the first evidence for production in two-photon interactions by tagging either the electron or the position in the final state, exploring the highly virtual photon region. The search is performed in , using 825 fb of data collected by the Belle detector operated at the KEKB collider. We observe three candidates with an expected background of events, with a significance of 3.2. We obtain an estimated value for ) assuming the dependence predicted by a meson model, where is the invariant mass-squared of the virtual photon. No candidates are found
Processes, microstructure, and mechanical properties of cold-rolled medium-Mn steel
No full textMedium-Mn steel has drawn tremendous attention recently for automotive lightweight applications, because of its excellent combination of high strength and superior formability. The present work aims at an in-depth understanding of the process-microstructure-property relationship in medium-Mn steel. The influence of various process parameters (i.e., cold rolling, intercritical-annealing temperature, intercritical-annealing time, and cooling procedures after intercritical annealing) on microstructure and mechanical properties was investigated in medium-Mn steel Fe-12Mn-3Al-0.05C (wt%). Scanning electron microscopy (SEM) in combination with electron backscattered diffraction (EBSD) technique was employed to characterize the microstructural features of the ultrafine-grained (UFG) medium-Mn steel, namely the grain size, grain morphology, orientation distribution, and phase fraction, etc. In order to investigate the kinetics of austenite reversion and mechanical stability of retained austenite, synchrotron high-energy X ray diffraction (HEXRD) was applied to in situ monitor the evolution of the amount of austenite during intercritical annealing as well as tensile deformation, respectively. The elemental partitioning behavior in medium-Mn steel was characterized by three dimensional atom probe tomography (3D-APT). The results indicate that cold rolling promotes homogeneous austenite nucleation, which is mainly responsible for fast austenite reversion kinetics. Among the other process parameters, the intercritical-annealing temperature is the most relevant for determining the microstructure features (e.g. the amount and stability of austenite, grain morphology, and grain size etc.) and mechanical performance. Ductility of the investigated medium-Mn steel strongly replies on the amount of retained austenite, and it is less sensitive to the mechanical stability of retained austenite. In addition, carbon segregation to the ferrite-austenite phase boundaries was for the first time observed in medium-Mn steel by adjusting cooling conditions after intercritical annealing, resulting in a discontinuous yielding phenomenon and an increase in yield strength as well as mechanical stability of retained austenite. The new insights provide novel opportunities to engineer interphase boundaries at an atomic scale in multiphase steel in order to tailor mechanical properties
Effect of non-mesogenic chiral terphenylate on the formulation of room temperature ferroelectric liquid crystal mixtures suitable for display applications
No full textBy varying the concentration of a chiral terphenylate dopant in a four-component achiral phenyl pyrimidine-based host mixture we have formulated six ferroelectric liquid crystal mixtures. Though the dopant is non-mesogenic it is observed that only 2 wt% of it induces polarity in the host mixture at 32 °C. With increasing concentration, the mixtures show ferroelectric behavior even below ambient temperature down to at least 12 °C. Optical polarizing microscopy, differential scanning calorimetry, dielectric and electro-optic studies reveal that with respect to temperature range, phase sequence, spontaneous polarization, optical tilt angle and switching time the formulated mixtures are suitable for ferroelectric based liquid crystal displays
Bond-stretching force constants and vibrational frequencies in ternary zinc-blende alloys: A systematic comparison of (In,Ga)P, (In,Ga)As and Zn(Se,Te)
No full textWe present element-specific effective bond-stretching force constants and Einstein frequencies of (In,Ga)P ternary alloys determined by temperature-dependent extended x-ray absorption fine structure spectroscopy. The bond-stretching force constants of both bond species show a nearly linear composition dependence between the values of GaP and InP. In contrast, the corresponding Einstein frequencies are different for the two bond species over the whole compositional range. Furthermore, we demonstrate that the composition dependence of bond-stretching force constants and Einstein frequencies for (In,Ga)P, (In,Ga)As, and Zn(Se,Te) is mostly caused by the associated bond length changes. Remaining deviations may be explained by coupling effects between different bond species within the alloy
Review of Particle Physics
No full textThe Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,324 new measurements from 878 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on High Energy Soft QCD and Diffraction and one on the Determination of CKM Angles from B Hadrons
Tailoring the breathing behavior of functionalized materials by using the mixed-metal concept
No full textMixed-metal metal-organic frameworks with two or more metals distributed over crystallographically equivalent sites are gaining growing attention in various research areas. We have extended the range of available mixed-metal frameworks of the MIL-53-NH2 family by combining aluminum with scandium, vanadium, chromium or iron. In contrast to other already reported mixed-metal MIL-53 materials, the developed MIL-53(Al,M)-NH2 materials (M = Sc, V, Cr, Fe), which contain 2-aminoterephthalate as linker instead of terephthalate, will enable subsequent post-synthetic modifications. All developed materials have been thoroughly characterized with standard methods as well as X-ray absorption spectroscopy to prove the exclusive incorporation of the employed metals into the MIL-53-NH2 framework structure and to verify the absence of impurity phases. Nitrogen physisorption measurements revealed that the choice of the metal combinations and ratios had a strong influence on the breathing behavior. Furthermore, post-synthetic modification reactions of the amine groups with maleic anhydride showed that the metal combination had a dramatic impact on the resulting modification degrees. Thus, the flexibility of the pore systems can be tailored by a careful selection of suitable metal combinations for these materials