Search for three-jet resonances in pp collisions at √s=7 TeV

This is a Pre-Print version of the Article - Copyright @ 2011 APSA model-independent search for three-jet hadronic resonance production in pp collisions at a center-of-mass energy of 7 TeV has been conducted by the CMS Collaboration at the LHC, using a data sample corresponding to an integrated luminosity of 35 inverse picobarns. Events with high jet multiplicity and a large scalar sum of jet transverse momenta are analyzed. The number of expected standard model background events is found to be in good agreement with the observed events. Limits are set on a model describing the production of R-parity-violating supersymmetric gluino pairs, and gluino masses in the range of 200 to 280 GeV/c^2 are excluded at a 95% confidence level for the first time.This work is supported by the FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF andWCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

Electrothermal vaporization inductively coupled plasma mass spectrometric detection of As, Sb, Se, Bi and Sn following preconcentration by in situ collection of their hydrides

Volatile hydrides of As, Se, Sb, Sn and Bi were generated from aqueous sample solutions using a tetrahydroborate reductant. The gaseous analytes were transferred to the inner wall of an electrothermal vaporizer (graphite furnace) and preconcentrated on a 1.25 \u3bcg thin-film of reduced palladium at 400\ub0C. The furnace comprised the sample introduction unit of an inductively coupled plasma mass spectrometric detection system. Absolute limits of detection (3\u3c3B) were 2.9, 3.3, 54, 5 and 1980 pg for As, Sb, Sn, Bi and Se, respectively. System efficiency for the generation and sequestration of the hydrides averaged, with the exception of Se, better than 75%. Multielement determinations of As, Se and Bi were possible using the same experimental conditions, those for Sn and Sb were accomplished in a separate run. The efficacy of this analytical approach was verified by the analysis of several marine reference materials using simple calibration standards prepared in the same manner as the samples. Good agreement with certified values was achieved for As, Sn, Sb and Se; no reference materials were available for assessment of accuracy in the case of Bi.NRC publication: Ye

Background spectral features in electrothermal vaporization inductively coupled plasma mass spectrometry: molecular ions resulting from the use of chemical modifiers

The formation of background polyatomic ions in electrothermal vaporization inductively coupled plasma mass spectrometry is reported. Vaporization temperatures ranging from 800 to 2500\ub0C were studied. Carbon-containing polyatomic ions interfere with the determination of Mg, Si, Ti, Ca and Cr. Polyatomic ions resulting from the vaporization of ascorbic acid, sodium chloride, magnesium nitrate, nickel nitrate and palladium nitrate chemical modifiers were studied. Microgram quantities of chemical modifier resulted in oxide and argide polyatomic ion intensities equivalent to picogram background equivalent masses for interfered analyte isotopes. In most cases alternative analyte isotopes free of interference were available. The formation of carbide of nitride modifier molecular ions was not observed. The argon dimer could be used as a diagnostic tool to indicate plasma loading effects and matrix suppression effects resulting from the use of chemical modifiers.NRC publication: Ye

Determination of inorganic and total mercury in biological tissues by electrothermal vaporization inductively coupled plasma mass spectrometry

A rapid method for the determination of total and inorganic mercury in biological tissues is presented using electrothermal vaporization inductively coupled plasma mass spectrometry (ETV ICP\u2013MS). Samples were solubilized using tetramethylammonium hydroxide. For the determination of total mercury sample aliquots (10 \ub5l) are dried and vaporized into the plasma. For the determination of inorganic mercury, iodoacetic acid, sodium thiosulfate and acetic acid are added to the sample, cleaving the methylmercury from the tissue. Volatile methylmercury iodide is formed and removed from the ETV as the sample dries, leaving only inorganic mercury to be quantified. A limit of detection of 0.05 \ub5g g -1 in solid samples was obtained. National Research Council of Canada reference materials DORM-2 (dogfish muscle), DOLT-2 (dogfish liver) and TORT-2 (lobster hepatopancreas) were used to assess the accuracy of the method.NRC publication: Ye

Direct analysis of solids by ultrasonic slurry electrothermal vaporization inductively coupled plasma mass spectrometry

The direct analysis of solids using ultrasonic slurry electrothermal vaporization inductively coupled plasma mass spectrometry is reported. National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1632a Trace Elements in Coal (Bituminous), Total Diet SRM 1548 and National Research Council of Canada LUTS-1 Lobster Hepatopancreas RM were analysed for a number of elements including Ni, Cu, Cr, Pb, Mn and Co. As a consequence of matrix effects, most analytes were determined using the method of standard additions, although Ni, Cu, Pb and Mn in NIST coal and Pb in LUTS-1 were successfully determined by external calibration using aqueous standards. With the exception of Cr in the coal sample, excellent agreement was obtained between the concentration determined and the certified range. Monitoring of the argon dimer during the high temperature vaporization cycle was shown to be an effective means of assessing matrix effects and selecting calibration strategies for individual analytes. Calculated limits of detection range from 0.07 ng g\u20131 for Co to 3.2 ng g\u20131 for Cr in 2 mg samples.NRC publication: Ye

Determination of ultratrace levels of heavy metals in arctic snow by electrothermal vaporization inductively coupled plasma mass spectrometry

Application of electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) to the direct determination of trace heavy metals in surface samples of Arctic snow is described. Limits of detection by ETC-ICP-MS are in the fg range, viz., 29, 57, 86, 120, 140, 360, 420, 470, 870 and 3200 for Tl, Cs, Pb, Mn, Co, V, Cu, Ni, Cd and Cr, respectively. Direct quantification against simple aqueous standards is feasible using NaCl solution as a carrier. The latter was obtained in a high-purity form through dilution of the sea-water reference material National Research Council of Canada (NRCC) NASS-3. Assessment of accuracy was accomplished by analysis of the river water reference material SLRS-2 (NRCC) and by comparative analysis of the samples by electrothermal atomization atomic absorption spectrometry.NRC publication: Ye

Kinetics of release of carbon and carbon monoxide from a graphite furnace investigated by electrothermal vaporization inductively coupled plasma mass spectrometry

Detection of carbon-containing molecules released during the high temperature heating of a dry, unloaded HGA-type graphite furnace (GF) has been undertaken by interfacing the GF to an ICP-MS. Desorption of O2 (as CO) chemisorbed onto the GF surface can be discriminated from that produced as a result of continuous oxidation of the surface by gaseous O2 impurity. Because plasma-induced dissociation of CO is negligible, signals arising from C do not have to be deconvoluted from those of CO. To a first approximation, the formation of C and CO can be treated as independent processes. A theoretical analysis of the transient experimental signals is presented.NRC publication: Ye

Investigation of vapour condensation in graphite furnace atomic absorption spectrometry by the shadow spectral digital imaging techniques

Condensation of vapors of gold (analyte) and matrices of various chemical modifiers and compounds in graphite furnace atomic absorption spectrometry was investigated by using the shadow spectral digital imaging technique with a charge-coupled device camera. Spatial and temporal nonuniformity in the light scattering was observed, and these effects were attributed to the formation of condensed-phase particles during the processes of high-temperature vaporization and atomization. The materials investigated were Au, MgCl2, NaCl, (NH4)2HPO4, La(NO3)3, and a mixture Pd and Mg(NO3)2. The nonuniform distributions of the condensed-phase particle clouds were attributed to the gas-flow patterns that developed in the graphite tube furnace during heating, as well as the steep temperature gradients that developed along the longitudinal axis of the end-heated graphite tube of the Massmann-type graphite furnace. Differences observed with fast and slow rates of heating were related to thermal expansion of gas and diffusion effects. Use of either a graphite platform or a low argon purge gas flow during the high-temperature heating of the graphite furnace was found to reduce condensation of matrix vapor and to improve accuracy of continuum source background correction.NRC publication: Ye

Seawater as a multi-component physical carrier for ETV-ICP-MS

The beneficence of NASS-3 sea water in enhancing analyte response in ETV-ICP-MS was investigated from a mechanistic viewpoint. Seawater serves as a multi-component physical carrier which acts primarily to increase the transport efficiency of analytes having wide ranging volatilities. A study of the major components of seawater revealed that HCl, released upon the hydrolysis of MgCl2, is most beneficial to very volatile elements (Cd, Rb, Cs and Tl), volatilization of NaCl affects elements of intermediate volatility (Pb, Ag, In, Ga and Bi), and MgO vaporization increases the transport efficiency of involatile elements (Co). Analyte signal enhancements were reduced or signal suppression occurred when NaCl or NASS-3 was added in amounts in excess of 0.07 \u3bcg. The carrier that caused the least signal suppression when used at high concentration was HCl. Decreasing the ETV heating rate enhances the effect of the physical carrier if the matrix element and analyte co-vaporize.NRC publication: Ye