Formation of Gold Nanoparticle Self-Assembling Films in Various Polymer Matrices for SERS Substrates

Surface-enhanced Raman spectroscopy (SERS) is regarded as a versatile tool for studying the composition and structure of matter. This work has studied the preparation of a SERS substrate based on a self-assembling plasmonic nanoparticle film (SPF) in a polymer matrix. Several synthesis parameters for the SPF are investigated, including the size of the particles making up the film and the concentration and type of the self-assembling agent. The result of testing systems with different characteristics is discussed using a model substance (pseudo isocyaniniodide). These models can be useful in the study of biology and chemistry. Research results contain the optimal parameters for SPF synthesis, maximizing the SERS signal. The optimal procedure for SPF assembly is determined and used for the synthesis of composite SPFs within different polymer matrices. SPF in a polymer matrix is necessary for the routine use of the SERS substrate for various types of analytes, including solid samples or those sensitive to contamination. Polystyrene, polyvinyl alcohol (PVA), and polyethylene are investigated to obtain a polymer matrix for SPF, and various methods of incorporating SPF into a polymer matrix are being explored. It is found that films with the best signal enhancement and reproducibility were obtained in polystyrene. The minimum detectable concentration for the SERS substrate obtained is equal to 10 10 M We prepared a SERS substrate with an analytical enhancement factor of 2.7 104, allowing an increase in the detection sensitivity of analyte solutions of five orders of magnitude

Beyond Charge Transfer: The impact of auger recombination and FRET on PL quenching in an rGO-QDs system

PL intensity quenching and the PL lifetime reduction of fluorophores located close to gra‐ phene derivatives are generally explained by charge and energy transfer processes. Analyzing the PL from PbS QDs in rGO/QD systems, we observed a substantial reduction in average PL lifetimes with an increase in rGO content that cannot be interpreted solely by these two processes. To explain the PL lifetime dependence on the rGO/QD component ratio, we propose a model based on the Auger recombination of excitations involving excess holes left in the QDs after the charge transfer process. To validate the model, we conducted additional experiments involving the external engi‐ neering of free charge carriers, which confirmed the role of excess holes as the main QD PL quench‐ ing source. A mathematical simulation of the model demonstrated that the energy transfer between neighboring QDs must also be considered to explain the experimental data carefully. Together, Au‐ ger recombination and energy transfer simulation offers us an excellent fit for the average PL life‐ time dependence on the component ratio of the rGO/QD system

Measurements of production cross sections of the Higgs boson in the four-lepton final state in proton-proton collisions at √s=13TeV

Production cross sections of the Higgs boson are measured in the H→ZZ→4ℓ (ℓ=e,μ) decay channel. A data sample of proton-proton collisions at a center-of-mass energy of 13TeV, collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137fb−1 is used. The signal strength modifier μμ, defined as the ratio of the Higgs boson production rate in the 4ℓ channel to the standard model (SM) expectation, is measured to be μ=0.94±0.07(stat)+0.09−0.08(syst) at a fixed value of mH=125.38GeV. The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H→4ℓ process is measured to be 2.84+0.23−0.22(stat)+0.26−0.21(syst)fb, which is compatible with the SM prediction of 2.84±0.15fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions

Observation of a New Excited Beauty Strange Baryon Decaying to Ξ−bπ+π−

The Ξ−bπ+π− invariant mass spectrum is investigated with an event sample of proton-proton collisions at √s=13  TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140  fb−1. The ground state Ξ−b is reconstructed via its decays to J/ψΞ− and J/ψΛK−. A narrow resonance, labeled Ξb(6100)−, is observed at a Ξ−bπ+π− invariant mass of 6100.3±0.2(stat)±0.1(syst)±0.6(Ξ−b)  MeV, where the last uncertainty reflects the precision of the Ξ−b baryon mass. The upper limit on the Ξb(6100)− natural width is determined to be 1.9  MeV at 95% confidence level. The low Ξb(6100)− signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Ξc baryon states, the new Ξb(6100)− resonance and its decay sequence are consistent with the orbitally excited Ξ−b baryon, with spin and parity quantum numbers JP=3/2−

Search for resonant and nonresonant new phenomena in high-mass dilepton final states at √s = 13 TeV

A search is presented for physics beyond the standard model (SM) using electron or muon pairs with high invariant mass. A data set of proton-proton collisions collected by the CMS experiment at the LHC at √s = 13 TeV from 2016 to 2018 corresponding to a total integrated luminosity of up to 140 fb−1 is analyzed. No significant deviation is observed with respect to the SM background expectations. Upper limits are presented on the ratio of the product of the production cross section and the branching fraction to dileptons of a new narrow resonance to that of the Z boson. These provide the most stringent lower limits to date on the masses for various spin-1 particles, spin-2 gravitons in the Randall-Sundrum model, as well as spin-1 mediators between the SM and dark matter particles. Lower limits on the ultraviolet cutoff parameter are set both for four-fermion contact interactions and for the Arkani-Hamed, Dimopoulos, and Dvali model with large extra dimensions. Lepton flavor universality is tested at the TeV scale for the first time by comparing the dimuon and dielectron mass spectra. No significant deviation from the SM expectation of unity is observed

Search for supersymmetry in proton-proton collisions at √s = 13 TeV in events with high-momentum Z bosons and missing transverse momentum

A search for new physics in events with two highly Lorentz-boosted Z bosons and large missing transverse momentum is presented. The analyzed proton-proton collision data, corresponding to an integrated luminosity of 137 fb−1, were recorded at √s = 13 TeV by the CMS experiment at the CERN LHC. The search utilizes the substructure of jets with large radius to identify quark pairs from Z boson decays. Backgrounds from standard model processes are suppressed by requirements on the jet mass and the missing transverse momentum. No significant excess in the event yield is observed beyond the number of background events expected from the standard model. For a simplified supersymmetric model in which the Z bosons arise from the decay of gluinos, an exclusion limit of 1920 GeV on the gluino mass is set at 95% confidence level. This is the first search for beyond-standard-model production of pairs of boosted Z bosons plus large missing transverse momentum

Search for decays of the 125 GeV Higgs boson into a Z boson and a ρ or ϕ meson

Decays of the 125 GeV Higgs boson into a Z boson and a ρ0(770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at √s = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb−1. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04-1.31% and 0.31-0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740-940 and 730-950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels

Measurements of the differential cross sections of the production of Z + jets and γ + jets and of Z boson emission collinear with a jet in pp collisions at √s = 13 TeV

Measurements of the differential cross sections of Z + jets and γ + jets production, and their ratio, are presented as a function of the boson transverse momentum. Measurements are also presented of the angular distribution between the Z boson and the closest jet. The analysis is based on pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb−1 recorded by the CMS experiment at the LHC. The results, corrected for detector effects, are compared with various theoretical predictions. In general, the predictions at higher orders in perturbation theory show better agreement with the measurements. This work provides the first measurement of the ratio of the differential cross sections of Z + jets and γ + jets production at 13 TeV, as well as the first direct measurement of Z bosons emitted collinearly with a jet

Measurements of pp→ZZ production cross sections and constraints on anomalous triple gauge couplings at √s=13TeV

The production of Z boson pairs in proton-proton (pppp) collisions, pp→(Z/γ∗)(Z/γ∗)→2ℓ2ℓ′, where ℓ,ℓ′=e or μ, is studied at a center-of-mass energy of 13TeV with the CMS detector at the CERN LHC. The data sample corresponds to an integrated luminosity of 137fb−1, collected during 2016-2018. The ZZ production cross section, σtot(pp→ZZ)=17.4±0.3(stat)±0.5(syst)±0.4(theo)±0.3(lumi) pb, measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region 60<mℓ+ℓ−<120GeV is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings

Search for dark matter produced in association with a leptonically decaying Z boson in proton-proton collisions at √s=13TeV

A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass energy of 13TeV, collected by the CMS experiment at the LHC in 2016-2018, corresponding to an integrated luminosity of 137fb−1. The search uses the decay channels Z→ee and Z→μμ. No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from direct-detection experiments. The results are also interpreted in the context of models of invisible Higgs boson decays, unparticles, and large extra dimensions