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We fabricated memristive devices using focused electron beam-induced deposition (FEBID) as a direct-writing technique employing a Pt/TiO2/Pt sandwich layer device configuration. Pinching in the measured current-voltage characteristics (i-v), the characteristic fingerprint of memristive behavior was clearly observed. The temperature dependence was measured for both high and low resistive states in the range from 290 K down to about 2 K, showing a stretched exponential behavior characteristic of Mott-type variable-range hopping. From this observation, a valence change mechanism of the charge transport inside the TiO2 layer can be deduced.
The first evaluation of an ultra-high granularity digital electromagnetic calorimeter prototype using 1.0–5.8 GeV/c electrons is presented. The 25 × 106 pixel detector consists of 24 layers of ALPIDE CMOS MAPS sensors, with a pitch of around 30 μm, and has a depth of almost 20 radiation lengths of tungsten absorber. Ultra-thin cables allow for a very compact design. The properties that are critical for physics studies are measured: electromagnetic shower response, energy resolution and linearity. The stochastic energy resolution is comparable with the state-of-the art resolution for a Si-W calorimeter, with data described well by a simulation model using Geant4 and Allpix2. The performance achieved makes this technology a good candidate for use in the ALICE FoCal upgrade, and in general demonstrates the strong potential for future applications in high-energy physics.
Using (10087±44)×106 J/ψ events collected with the BESIII detector, numerous Ξ− and Λ decay asymmetry parameters are simultaneously determined from the process J/ψ→Ξ−Ξ¯+→Λ(pπ−)π−Λ¯(n¯π0)π+ and its charge-conjugate channel. The precisions of α0 for Λ→nπ0 and α¯0 for Λ¯→n¯π0 compared to world averages are improved by factors of 4 and 1.7, respectively. The ratio of decay asymmetry parameters of Λ→nπ0 to that of Λ→pπ−, ⟨α0⟩/⟨αΛ−⟩, is determined to be 0.873±0.012+0.011−0.010, where the first and the second uncertainties are statistical and systematic, respectively. The ratio is smaller than unity more than 5σ, which signifies the existence of the ΔI=3/2 transition in Λ for the first time. Beside, we test for CP violation in Ξ−→Λπ− and in Λ→nπ0 with the best precision to date.
Using e+e− collision data, corresponding to an integrated luminosity of 892pb−1 collected at center-of-mass energies from 4.84 to 4.95\,GeV with the BESIII detector, we search for the process e+e−→K+K−ψ(3770) by reconstructing two charged kaons and one D meson from ψ(3770). No significant signal of e+e−→K+K−ψ(3770) is found and the upper limits of the Born cross sections are reported at 90\% confidence level.
The ALICE Collaboration measures the production of low-mass dielectrons in pp, p-Pb and Pb-Pb collisions at the LHC. The main detectors used in the analyses are the Inner Tracking System, Time Projection Chamber and Time-Of-Flight detector, all located around mid-rapidity. The production of virtual photons relative to the inclusive yield in pp collisions is determined by analyzing the dielectron excess with respect to the expected hadronic sources. The direct photon cross section is then calculated and found to be in agreement with NLO pQCD calculations. Results from the invariant mass analysis in p-Pb collisions show an overall agreement between data and hadronic cocktail. In Pb-Pb collisions, uncorrected background-subtracted yields have been extracted in two centrality classes. A feasibility study for LHC run 3 after the ALICE upgrade indicates the possibility for a future measurement of the early effective temperature.
We investigate the thermodynamic geometry of the quark-meson model at finite temperature, T, and quark number chemical potential, μ. We extend previous works by the inclusion of fluctuations exploiting the functional renormalization group approach. We use recent developments to recast the flow equation into the form of an advection-diffusion equation. We adopt the local potential approximation for the effective average action. We focus on the thermodynamic curvature, R, in the (μ,T) plane, in proximity of the chiral crossover, up to the critical point of the phase diagram. We find that the inclusion of fluctuations results in a smoother behavior of R near the chiral crossover. Moreover, for small μ, R remains negative, signaling the fact that bosonic fluctuations reduce the capability of the system to completely overcome the fermionic statistical repulsion of the quarks. We investigate in more detail the small μ region by analyzing a system in which we artificially lower the pion mass, thus approaching the chiral limit in which the crossover is actually a second order phase transition. On the other hand, as μ is increased and the critical point is approached, we find that R is enhanced and a sign change occurs, in agreement with mean field studies. Hence, we completely support the picture that R is sensitive to a crossover and a phase transition, and provides information about the effective behavior of the system at the phase transition.
The photoelectric effect describes the ejection of an electron upon absorption of one or several photons. The kinetic energy of this electron is determined by the photon energy reduced by the binding energy of the electron and, if strong laser fields are involved, by the ponderomotive potential in addition. It has therefore been widely taken for granted that for atoms and molecules, the photoelectron energy does not depend on the electron’s emission direction, but theoretical studies have questioned this since 1990. Here, we provide experimental evidence that the energies of photoelectrons emitted against the light propagation direction are shifted toward higher values, while those electrons that are emitted along the light propagation direction are shifted to lower values. We attribute the energy shift to a nondipole contribution to the ponderomotive potential that is due to the interaction of the moving electrons with the incident photons.
The ALICE experiment at the LHC investigates the properties of the hot and dense nuclear matter created in heavy-ion collisions. By comparing the particle production in pp and p-Pb collisions, possible nuclear initial state effects can be isolated. Measurements of the ω meson pT-spectra in pp and p-Pb collisions not only allow for a determination of the nuclear modification factor RpPb, but also provide insight into the fragmentation process and serve as vital input for decay background simulations for direct photons. In this contribution, measurements of the ω meson production in pp and p-Pb collisions at √sNN=5.02 TeV are presented. This includes the signal extraction and various corrections of the ω meson yields, leading to their production cross sections and the first measured nuclear modification factor RpPb of the ω meson at LHC energies.
Observation of χcJ → 3(K⁺K⁻)
(2024)
By analyzing (27.12±0.14)×108 𝜓(3686) events collected with the BESIII detector operating at the BEPCII collider, the decay processes 𝜒𝑐𝐽→3(𝐾+𝐾−) (𝐽=0, 1, 2) are observed for the first time with statistical significances of 8.2𝜎, 8.1𝜎, and 12.4𝜎, respectively. The product branching fractions of 𝜓(3686)→𝛾𝜒𝑐𝐽, 𝜒𝑐𝐽→3(𝐾+𝐾−) are presented and the branching fractions of 𝜒𝑐𝐽→3(𝐾+𝐾−) decays are determined to be ℬ𝜒𝑐0→3(𝐾+𝐾−)=(10.7±1.8±1.1)×10−6, ℬ𝜒𝑐1→3(𝐾+𝐾−)=(4.2±0.9±0.5)×10−6, and ℬ𝜒𝑐2→3(𝐾+𝐾−)=(7.2±1.1±0.8)×10−6, where the first uncertainties are statistical and the second are systematic.
Using data samples with an integrated luminosity of 6.4~fb−1 collected by the BESIII detector operating at the BEPCII storage ring, the process of e+e−→γϕJ/ψ is studied. The processes of e+e−→ϕχc1,c2, χc1,c2→γJ/ψ are observed with a significance of more than 10σ. The s√-dependent cross section of e+e−→ϕχc1,c2 is measured between 4.600 and 4.951~GeV, and evidence of a resonance structure is found for the first time in the ϕχc2 process. We also search for the processes of e+e−→γX(4140), γX(4274) and γX(4500) via the γϕJ/ψ final state, but no obvious structures are found. The upper limits on the production cross section times the branching fraction for these processes at the 90% confidence level are reported.