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Measurement of the inclusive production cross section and search for additional scalars in final states at CMS
No full textTwo key measurements and two phenomenological studies of top quark pair () production with the CMS experiment at the CERN Large Hadron Collider are presented. They include the first measurement of the cross section at the new energy frontier, a detailed analysis of the threshold culminating in the first observation of bound state effects, and searches for new physics in final states, such as heavy scalars, pseudoscalars or Axion-Like Particles.The inclusive production cross section is measured for the first time at the world-record energy of , using of early LHC Run 3 data. By combining the dilepton and lepton+jets () decay channels and constraining the lepton and b tagging efficiencies \textit{in situ}, a precision of , comparable to previous measurements, is achieved. This constitutes the first measurement of proton-proton scattering at worldwide.Furthermore, a search for heavy spin-0 states decaying to using of LHC Run 2 data at in the dilepton channels is presented. The invariant mass () is combined with spin correlation observables to gain sensitivity to the spin and structure of possible new intermediate states. The analysis is supported by a detailed modeling study of off-shell production and of the interference between and tW production.An excess of events over the continuum background is observed at low values of , with spin correlations consistent with a pseudoscalar state. It is interpreted in terms of a pseudoscalar bound state , and its cross section is measured to be using a simplified model inspired by non-relativistic quantum chromodynamics. The excess is statistically significant at more than five standard deviations, constituting the first observation of bound state effects.Other interpretations of the observed excess are similarly possible. In particular, scenarios with generic pseudoscalar or scalar bosons are explored, and exclusion regions on their coupling to the top quark are derived both for the dilepton channels alone as well as in a combination with a separate analysis of the channels. In addition, Axion-Like Particles (ALPs) decaying to are considered in the case of vanishing tree-level ALP-gluon couplings, while the more generic case is investigated phenomenologically in simulation
Reversible dc-Ge to (-Sn)-Ge transformation under high shear
No full textThe pressure-synthesized phases of Ge have properties of technological interest. Such phases are generally formed after decompression from the metallic -Sn structure of Ge above 10 GPa under hydrostatic compression. Here, we subjected diamond cubic Ge (dc-Ge) to high-pressure and high-shear environments using both regular diamond anvil cells with no pressure medium and a rotational diamond anvil cell. We report both a reversible (β-Sn)-Ge to dc-Ge pathway and a significant reduction, as low as 2 GPa, in the pressure required to form the (β-Sn)-Ge phase in high-shear conditions. This lowered transition pressure may be promoted by an increase in shear-induced defects, which act as nucleation sites for the transition to the metallic (β-Sn)-Ge phase. The metallic phase formed below 8 GPa shows reversible transformation back to the diamond cubic phase upon decompression, contrasting with metallic Ge formed above 10 GPa, which irreversibly transforms into several metastable phases. This work provides insights into the behavior of Ge under pressure and high-shear environments
Self-imitating oligomeric additives enable 19% efficiency in benzo[1,2-b:4,5-b′]difuran polymer-based organic solar cells
No full textThe development of power conversion efficiency (PCE) for organic solar cells (OSCs) based on polymer donors with benzo[1,2-b:4,5-b′]-difuran building block is slower than that of those based on benzodithiophene due to uncontrollable aggregation behavior. However, the former is expected to be more promising in realizing environmentally friendly and high-performance devices. Thereby, a smart aggregation tuning strategy is needed for boosting the efficiency of this type of OSCs. Here we report solid additives designed by self-imitation strategy, which aims to control the aggregation of the donor D18-Fu, and regulate the domain expansion of the acceptor L8-BO. Three oligomeric additives, with or without halogenation, can uniformly reduce the energy loss and enhance charge generation compared to an additive-free control device. This improvement is demonstrated through a series of morphological characterizations, photophysical analyses and theoretical simulations, indicating strong interaction between additive molecules and donor & acceptor. As a result, a 19% PCE is reported in binary OSCs, which also represents the highest level for devices based on benzo[1,2-b:4,5-b′]-difuran core contained polymer donor. Apart from high performance, our study provides new insights into manipulating the competition between the donor and acceptor’s pure phase formation through new additive design methods
AgPdO , a New Subvalent Silver Oxide, Obtained from AgPdO via a High‐pressure Synthesis
No full textSubvalent silver oxides, where silver exhibits an oxidation state between 0 and + 1, have traditionally been discovered serendipitously due to a lack of systematic synthesis methods and understanding of their bonding schemes. This study presents a novel, purposeful approach to synthesizing multinary subvalent silver oxides through high-pressure techniques. By subjecting the monovalent silver oxide Ag2PdO2 to hydrostatic pressure of ∼30 GPa and laser heating at 1500 K, subvalent Ag5Pd2O4 forms besides PdO. The crystal structure of Ag5Pd2O4, determined via in situ single-crystal X-ray diffraction, reveals distinct layers of cationic silver aggregates and anionic oxopalladate units. Electronic structure calculations confirm the subvalent nature of silver in Ag5Pd2O4, showing a vanished band gap and increased electron density on silver atoms. The findings pave the way for developing materials with rich magneto-electronic functionalities, owing to the interplay between subvalent silver and transition metal cations
Search for dark matter from the center of the Earth with 10 years of IceCube data
No full textThe nature of dark matter remains unresolved in fundamental physics. Weakly Interacting Massive Particles (WIMPs), which could explain the nature of dark matter, can be captured by celestial bodies like the Sun or Earth, leading to enhanced self-annihilation into Standard Model particles including neutrinos detectable by neutrino telescopes such as the IceCube Neutrino Observatory. This article presents a search for muon neutrinos from the center of the Earth performed with 10 years of IceCube data using a track-like event selection. We considered a number of WIMP annihilation channels (//) and masses ranging from 10 GeV to 10 TeV. No significant excess over background due to a dark matter signal was found while the most significant result corresponds to the annihilation channel for the mass GeV with a post-trial significance of . Our results are competitive with previous such searches and direct detection experiments. Our upper limits on the spin-independent WIMP scattering are world-leading among neutrino telescopes for WIMP masses GeV
Mechanistic insights into solvent-guided growth and structure of MoO nanoparticles in solvothermal synthesis
No full textUnderstanding the processes involved in the nucleation and growth of nanoparticles is essential for the development of tailored nanomaterials. Here, we investigate the solvent effects on the atomic structure and size of nanocrystalline MoO obtained from a solvothermal synthesis and deduce their reaction pathways. Detailed pair distribution function (PDF) analysis reveals the formation of distinct MoO structures, depending on the alcohol used. We show that the atomic structure and crystallite size of the formed materials are directly related to their formation pathway. In situ PDF analysis together with X-ray absorption spectroscopy of the reaction between MoCl and an alcohol solvent allows us to see that larger nanoparticles (ca. 30 nm) with the conventional MoO2 distorted rutile structure form when the initial Cl/O-ligand exchange is fast, but the subsequent condensation and crystallization are slowed down in the synthesis process. On the other hand, when the Cl/O exchange is slowed down, a [MIVClxOy]-complex is formed, and we obtain very small nanoparticles (2–3 nm) with the MoO high-pressure polymorph structure. The study shows how the chemistry of the reaction solvent affects the mechanistic pathways, and consequently the intermediate formed just prior to crystallization, which is directly applicable to the process of obtaining specific nanocrystalline materials
Enhanced UVC upconversion luminescence in Pr-doped eulytite-type phosphates
No full textUVC radiation's strong antiseptic properties make it ideal for water and surface decontamination, underscoring the need for new UVC-generating materials. In this work, Pr3+-doped Ba3La(PO4)3 and Ba2.5La1.5(PO4)2.5(SiO4)0.5 phosphors were synthesized via the Pechini method, and their structural and luminescent properties were investigated. Both compounds crystallize in a cubic eulytite-type structure and exhibit stronger 1D2 → 3H4 (575–645 nm) emission than the 3P0 → 3H4 (465–505 nm) transition. Under UV excitation, efficient 5d–4f emission is observed, while 444 nm laser excitation induces UVC upconversion via a two-photon process dominated by excited-state absorption (ESA). Optimal upconversion occurs at 1.5 % Pr3+ doping, with Ba2.5La1.5(PO4)2.5(SiO4)0.5 showing ∼30 % higher intensity than Ba3La(PO4)3 due to enhanced local disorder and crystal field effects. These materials outperform YPO4:Pr3+ phosphate in upconversion emission, highlighting their potential for use in UVC-emitting devices
Measurement of the dineutrino system kinematic variables in dileptonic top quark pair production in proton-proton collisions at = 13 TeV
No full textDifferential top quark pair production cross sections are measured in the dilepton final states ee, , and e, as a function of kinematic variables of the two-neutrino system: the transverse momentum of the dineutrino system, the minimum distance in azimuthal angle between and leptons, and in two dimensions in bins of both observables. The measurements are performed using CERN LHC proton-proton collisions at = 13 TeV, recorded by the CMS detector between 2016 and 2018, corresponding to an integrated luminosity of 138 fb. The measured cross sections are unfolded to the particle level using an unregularized least squares method. Results are compared with predictions by the standard model of particle physics, and found to be in agreement with theoretical calculations as well as Monte Carlo simulations
Vector boson scattering and anomalous quartic couplings in final states with qq or qq plus jets using proton-proton collisions at = 13 TeV
No full textA measurement is presented of the electroweak vector boson scattering production of ZV (V = W, Z) boson pairs associated with two jets in proton-proton collisions at a center-of-mass energy of 13 TeV. The data, corresponding to an integrated luminosity of 138 fb, were collected at the CERN LHC with the CMS detector during the 20162018 data-taking period. The analysis targets final states with a pair of isolated electrons or muons from Z boson decays and three or four jets, depending on the momentum of the vector boson that decays into quarks. Signal strength is measured for events characterized by a large invariant mass of two forward jets with a wide pseudorapidity gap between them. The electroweak production of ZV in association with two jets is measured with an observed (expected) significance of 1.3 (1.8) standard deviations. A combination of the analyses of ZV channel and the previously published WV channel in the lepton plus jets final state places constraints on effective field theory parameters that describe anomalous electroweak production of WW, WZ, and ZZ boson pairs in association with two jets. Several world best limits are set on anomalous quartic gauge couplings in terms of dimension-8 standard model effective field theory operators