Experimental Method of Temperature and Strain Discrimination in Polymer Composite Material by Embedded Fiber-Optic Sensors Based on Femtosecond-Inscribed FBGs

Experimental method of temperature and strain discrimination with fiber Bragg gratings (FBGs) sensors embedded in carbon fiber-reinforced plastic is proposed. The method is based on two-fiber technique, when two FBGs inscribed in different fibers with different sensitivities to strain and/or temperature are placed close to each other and act as a single sensing element. The nonlinear polynomial approximation of Bragg wavelength shift as a function of temperature and strain is presented for this method. The FBGs were inscribed with femtosecond laser by point-by-point inscription technique through polymer cladding of the fiber. The comparison of linear and nonlinear approximation accuracies for array of embedded sensors is performed. It is shown that the use of nonlinear approximation gives 1.5–2 times better accuracy. The obtained accuracies of temperature and strain measurements are 2.6–3.8°C and 50–83 με in temperature and strain range of 30–120°C and 0–400 με, respectively

Measurement of nuclear modification factors of gamma(1S)), gamma(2S), and gamma(3S) mesons in PbPb collisions at root s(NN)=5.02 TeV

The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at √sNN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S)) > RAA(ϒ(2S)) > RAA(ϒ(3S)). The suppression of ϒ(1S) is larger than that seen at √sNN = 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT, rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. © 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.Peer reviewe

Distributed Bragg Reflector Laser Based on Composite Fiber Heavily Doped with Erbium Ions

A distributed Bragg reflector (DBR) laser with a specially designed, heavily Er3+-doped composite fiber of a length as short as 1.8 cm is demonstrated. The DBR laser, pumped by a 980 nm laser diode with power of up to 370 mW, generates single-frequency radiation at a wavelength of 1535 nm with a narrow instantaneous linewidth of 3+-doped fiber laser parameters pave the way toward a broad range of practical applications from telecommunications and sensing to scientific research

Single-Frequency Ring Fiber Laser with Random Distributed Feedback Provided by Artificial Rayleigh Scattering

Femtosecond (fs) laser inscription technology allows for the production of in-fiber disordered structures with an enhanced level of Rayleigh backscattering with relatively few induced losses. These properties enable the application of these structures as reflectors in fiber lasers. In this study, a narrow-linewidth erbium fiber laser with random distributed feedback provided by a fs-induced random structure in a ring cavity configuration was developed. A single-frequency regime was observed over the entire lasing power range. At a maximum output power of 7.8 mW, the linewidth did not exceed 0.75 kHz

Search for resonant pair production of Higgs bosons decaying to bottom quark-antiquark pairs in proton-proton collisions at 13 TeV

A search for a narrow-width resonance decaying into two Higgs bosons, each decaying into a bottom quark-antiquark pair, is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 35.9 fb$^{-1}$ at $\sqrt{s}=$ 13 TeV recorded by the CMS detector at the LHC. No evidence for such a signal is observed. Upper limits are set on the product of the production cross section for the resonance and the branching fraction for the selected decay mode in the resonance mass range from 260 to 1200 GeV

Measurement of Dijet Angular Distributions and Search for Quark Compositeness in pp Collisions at sqrts=7sqrt{s} = 7 TeV

Dijet angular distributions are measured over a wide range of dijet invariant masses in pp collisions at sqrt(s) = 7 TeV, at the CERN LHC. The event sample, recorded with the CMS detector, corresponds to an integrated luminosity of 36 inverse picobarns. The data are found to be in good agreement with the predictions of perturbative QCD, and yield no evidence of quark compositeness. With a modified frequentist approach, a lower limit on the contact interaction scale for left-handed quarks of Lambda = 5.6 TeV is obtained at the 95% confidence level