Corrosion processes in zirconium fluoride-sodium fluoride melts.Study of shortcut cell C/(ZrF₄ – NaF)EUT/Hastelloy

Time dependencies for the parameters (current, voltage, inner resistance) of shortcut galvanic cell Hastelloy-carbon material have been studied in NaF-ZrF₄ eutectic melt at 600…650°C. Analysis of these data, together with the data on polarization of separate electrodes at open circuit conditions, showed that shortcut current is related to the rate of corrosion of the alloy contacted with carbon, if Zr metal is absent in the system. In presence of Zr, the current corresponds to the rate of zirconium reaction with the melt (related to unit surface of the Hastelloy electrode), and can be used for studies of dissolution kinetics of Zr metal in the melt. It was found that contact of the alloy with carbon material results in the increase of corrosion rate both in pure eutectics and with the additives of LaF₃. Presence of Zr metal suppresses the corrosion process.Вивчена зміна в часі параметрів (струм, напруга, внутрішній опір) короткозамкненого гальванічного елемента хастелой/вуглецевий матеріал в евтектичному розплаві NaF-ZrF₄ при 600-650°C. Аналіз цих даних в сукупності з даними поляризаційних вимірювань на окремих електродах при розімкненому колі показав, що струм короткого замикання відповідає швидкості корозії сплаву в контакті з вуглецем при умові, якщо металічний Zr в системі відсутній. В присутності Zr цей струм визначається швидкістю взаємодії цирконію з розплавом (віднесеної до одиниці поверхні хастелою), що може бути використано для дослідження кінетики розчинення цирконію в розплаві. Встановлено, що контакт сплаву з вуглецем посилює корозію як в чисто евтектичному розплаві, так і з добавленням LaF₃. Присутність металічного Zr пригнічує корозійний процес.Исследована временная зависимость параметров (ток, напряжение, внутреннее сопротивление) короткозамкнутого гальванического элемента хастеллой/углеродный материал в эвтектическом расплаве NaF-ZrF₄ при 600-650°C. Анализ этих данных, в совокупности с данными поляризационных измерений на отдельных электродах при разомкнутой цепи, показал, что ток короткого замыкания соответствует скорости коррозии сплава в контакте с углеродом при условии, если металлический Zr в системе отсутствует. В присутствии же Zr этот ток определяется скоростью взаимодействия циркония с расплавом (отнесенной к единице поверхности хастеллоя), что может быть использовано для исследования кинетики растворения циркония в расплаве. Установлено, что контакт сплава с углеродом усиливает коррозию как в чисто эвтектическом расплаве, так и с добавками LaF₃. Присутствие же металлического Zr подавляет коррозионный процесс

Corrosion of irradiated Ni-Mo alloys in sodium fluoride - zirconium melt

The corrosion of nickel-molybdenum alloys and their constituents in a molten eutectic sodium fluoride-zirconium fluoride mixture has been studied by cyclic voltammetry, X-ray analysis, SEM and metallography. The dependence of the corrosion rate of nickel-molybdenum alloys in molten fluorides on the time of soaking in melt and irradiation with an electron beam on an electron accelerator has been investigated. It has been shown that increasing the time of contact of nickel-molybdenum alloys with fluoride melt decreases the corrosion current density, and irradiation increases it in the greater extent the higher the electron beam energy. Intercrystalline corrosion is typical of the alloys of this composition.Методами циклічної вольтамперометрії, рентгенофазового, мікроскопічного аналізів, а також металографії досліджена корозія нікель-молібденових сплавів та компонентів, які входять до їхнього складу, в розплавленій евтектичній суміші фторидів натрію та цирконію. Досліджена залежність швидкості корозії зазначених сплавів від тривалості витримки в розплаві та опромінення пучком електронів на електронному прискорювачі. Показано, що збільшення тривалості контакту нікель-молібденових сплавів з фторидним розплавом зменшує густину струму корозії, а опромінення – збільшує її в тим більшій мірі, чим більша енергія електронного пучка. Для сплавів даного складу характерна міжкристалітна корозія.Методами циклической вольтамперометрии, рентгенофазового, микроскопического анализов, а также металлографии изучена коррозия никель-молибденовых сплавов и составляющих компонентов в расплавленной эвтектической смеси фторидов натрия и циркония. Исследована зависимость скорости коррозии никель-молибденовых сплавов в расплавленных фторидах от времени выдержки в расплаве и облучения пучком электронов на электронном ускорителе. Показано, что увеличение времени контакта никель-молибденовых сплавов с фторидным расплавом уменьшает плотность тока коррозии, а облучение – увеличивает ее в тем большей мере, чем больше энергия электронного пучка. Для сплавов данного состава характерна межкристаллитная коррозия

Simultaneous Softening of sigma and rho Mesons associated with Chiral Restoration

Complex poles of the unitarized pi-pi scattering amplitude in nuclear matter are studied. Partial restoration of chiral symmetry is modeled by the decrease of in-medium pion decay constant f*_{pi}. For large chiral restoration (f*_{pi}/f_{pi} << 1), 2nd sheet poles in the scalar (sigma) and the vector (rho) mesons are both dictated by the Lambert W function and show universal softening as f*_{pi} decreases. In-medium pi-pi cross section receives substantial contribution from the soft mode and exhibits a large enhancement in low-energy region. Fate of this universality for small chiral restoration (f*_{pi}/f_{pi} ~ 1) is also discussed.Comment: 5 pages, 4-eps figures, version accepted by Phys. Rev. C (R) with minor modification

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters

Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO

Model-independent analysis of Higgs spin and CP properties in the process e+e−→ttˉΦe^+ e^- \to t \bar t \Phi

In this paper we investigate methods to study the $t\bar{t}$ Higgs coupling. The spin and CP properties of a Higgs boson are analysed in a model-independent way in its associated production with a $t\bar{t}$ pair in high-energy $e^+e^-$ collisions. We study the prospects of establishing the CP quantum numbers of the Higgs boson in the CP-conserving case as well as those of determining the CP-mixing if CP is violated. We explore in this analysis the combined use of the total cross section and its energy dependence, the polarisation asymmetry of the top quark and the up-down asymmetry of the antitop with respect to the top-electron plane. We find that combining all three observables remarkably reduces the error on the determination of the CP properties of the Higgs Yukawa coupling. Furthermore, the top polarisation asymmetry and the ratio of cross sections at different collider energies are shown to be sensitive to the spin of the particle produced in association with the top quark pair

Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

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