1,167 research outputs found
Spectrofluorimetric Determination of Aliskiren in Tablets and Spiked Human Plasma through Derivatization with Dansyl Chloride
A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501Â nm with excitition at 378Â nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100â700 and 50â150Â ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52Â ng/mL in standard solution, 4.91Â ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented
Search for Pair-Produced Resonances Decaying to Quark Pairs in Proton-Proton Collisions at âs = 13ââTeV
A general search for the pair production of resonances, each decaying to two quarks, is reported. The search is conducted separately for heavier resonances (masses above 400 GeV), where each of the four final-state quarks generates a hadronic jet resulting in a four-jet signature, and for lighter resonances (masses between 80 and 400 GeV), where the pair of quarks from each resonance is collimated and reconstructed as a single jet resulting in a two-jet signature. In addition, a b-tagged selection is applied to target resonances with a bottom quark in the final state. The analysis uses data collected with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 35.9ââfbâ»Âč, from proton-proton collisions at a center-of-mass energy of 13 TeV. The mass spectra are analyzed for the presence of new resonances, and are found to be consistent with standard model expectations. The results are interpreted in the framework of R-parity-violating supersymmetry assuming the pair production of scalar top quarks decaying via the hadronic coupling λâČâČ312 or λâČâČ323 and upper limits on the cross section as a function of the top squark mass are set. These results probe a wider range of masses than previously explored at the LHC, and extend the top squark mass limits in the ËtâqqâČ scenario
Search for electroweak production of charginos and neutralinos in multilepton final states in proton-proton collisions at âs = 13 TeV
Results are presented from a search for the direct electroweak production of charginos and neutralinos in signatures with either two or more leptons (electrons or muons) of the same electric charge, or with three or more leptons, which can include up to two hadronically decaying tau leptons. The results are based on a sample of proton-proton collision data collected at sâ=13 TeV, recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fbâ»Âč. The observed event yields are consistent with the expectations based on the standard model. The results are interpreted in simplified models of supersymmetry describing various scenarios for the production and decay of charginos and neutralinos. Depending on the model parameters chosen, mass values between 180 GeV and 1150 GeV are excluded at 95% CL. These results significantly extend the parameter space probed for these particles in searches at the LHC. In addition, results are presented in a form suitable for alternative theoretical interpretations
Search for Standard Model Production of Four Top Quarks with Same-Sign and Multilepton Final States in Protonâproton Collisions at âs = 13 TeV
A search for standard model production of four top quarks (ttÂŻttÂŻ) is reported using events containing at least three leptons (e,ÎŒ) or a same-sign lepton pair. The events are produced in protonâproton collisions at a center-of-mass energy of 13TeV at the LHC, and the data sample, recorded in 2016, corresponds to an integrated luminosity of 35.9fb[superscript â1]. Jet multiplicity and flavor are used to enhance signal sensitivity, and dedicated control regions are used to constrain the dominant backgrounds. The observed and expected signal significances are, respectively, 1.6 and 1.0 standard deviations, and the ttÂŻttÂŻ cross section is measured to be 16.9[superscript +13.8][subscript â11.4] fb, in agreement with next-to-leading-order standard model predictions. These results are also used to constrain the Yukawa coupling between the top quark and the Higgs boson to be less than 2.1 times its expected standard model value at 95% confidence level
Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at âs=8 TeV using H â WW decays
The cross section for Higgs boson production in pp collisions is studied using the H â W[superscript +]W[superscript â] decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 fb[superscript â1]. The Higgs boson transverse momentum (p[subscript T]) is reconstructed using the lepton pair p[subscript T] and missing p[subscript T]. The differential cross section times branching fraction is measured as a function of the Higgs boson pTin a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 ± 8 (stat) ± 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model. Keywords: Hadron-Hadron scattering (experiments), Higgs physicsNational Science Foundation (U.S.)United States. Department of Energ
Search for Low Mass Vector Resonances Decaying to Quark-Antiquark Pairs in Proton-Proton Collisions at âs = 13 TeV
A search is reported for a narrow vector resonance decaying to quark-antiquark pairs in proton-proton collisions at âs = 13 TeV, collected with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 2.7 fbâ»Âč. The vector resonance is produced at large transverse momenta, with its decay products merged into a single jet. The resulting signature is a peak over background in the distribution of the invariant mass of the jet. The results are interpreted in the framework of a leptophobic vector resonance and no evidence is found for such particles in the mass range of 100-300 GeV. Upper limits at 95% confidence level on the production cross section are presented in a region of mass-coupling phase space previously unexplored at the LHC. The region below 140 GeV has not been explored by any previous experiments
Search for supersymmetry in events with at least one photon, missing transverse momentum, and large transverse event activity in proton-proton collisions at âs = 13 TeV
A search for physics beyond the standard model in final states with at least one photon, large transverse momentum imbalance, and large total transverse event activity is presented. Such topologies can be produced in gauge-mediated supersymmetry models in which pair-produced gluinos or squarks decay to photons and gravitinos via short-lived neutralinos. The data sample corresponds to an integrated luminosity of 35.9 fb[superscript â1] of proton-proton collisions at sâ=13 TeV recorded by the CMS experiment at the LHC in 2016. No significant excess of events above the expected standard model background is observed. The data are interpreted in simplified models of gluino and squark pair production, in which gluinos or squarks decay via neutralinos to photons. Gluino masses of up to 1.50-2.00 TeV and squark masses up to 1.30-1.65 TeV are excluded at 95% confidence level, depending on the neutralino mass and branching fraction. Keywords: Hadron-Hadron scattering (experiments); Supersymmetry; Photon productio
Search for a new scalar resonance decaying to a pair of Z bosons in proton-proton collisions at âs=13 TeV
A search for a new scalar resonance decaying to a pair of Z bosons is performed in the mass range from 130 GeV to 3 TeV, and for various width scenarios. The analysis is based on proton-proton collisions recorded by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fbâ»Âč at a center-of-mass energy of 13 TeV. The Z boson pair decays are reconstructed using the 4â, 2â2q, and 2â2Îœ final states, where â = e or ÎŒ. Both gluon fusion and electroweak production of the scalar resonance are considered, with a free parameter describing their relative cross sections. A dedicated categorization of events, based on the kinematic properties of associated jets, and matrix element techniques are employed for an optimal signal and background separation. A description of the interference between signal and background amplitudes for a resonance of an arbitrary width is included. No significant excess of events with respect to the standard model expectation is observed and limits are set on the product of the cross section for a new scalar boson and the branching fraction for its decay to ZZ for a large range of masses and widths. Keywords: Hadron-Hadron scattering (experiments); Higgs physic
Charged-Particle Nuclear Modification Factors in PbPb and pPb Collisions at âsNN = 5.02 TeV
The spectra of charged particles produced within the pseudorapidity window |η| 20 GeV, R][subscript pA] exhibits weak momentum dependence and shows a moderate enhancement above unity.National Science Foundation (U.S.)United States. Department of Energ
Non-Gaussian elliptic-flow fluctuations in PbPb collisions at â s NN = 5.02 TeV
Event-by-event fluctuations in the elliptic-flow coefficient v are studied in PbPb collisions at s =5.02 TeV using the CMS detector at the CERN LHC. Elliptic-flow probability distributions p(v ) for charged particles with transverse momentum 0.3<p <3.0GeV/c and pseudorapidity |η|<1.0 are determined for different collision centrality classes. The moments of the p(v ) distributions are used to calculate the v coefficients based on cumulant orders 2, 4, 6, and 8. A rank ordering of the higher-order cumulant results and nonzero standardized skewness values obtained for the p(v ) distributions indicate non-Gaussian initial-state fluctuations. BesselâGaussian and elliptic power fits to the flow distributions are studied to characterize the initial-state spatial anisotropy. 2 NN 2 T 2 2
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