HAL Mines Nantes
Not a member yet
    7271 research outputs found

    Coherent J/ψJ/\psi and ψ′\psi' photoproduction at midrapidity in ultra-peripheral Pb-Pb collisions at sNN = 5.02\sqrt{s_{\mathrm{NN}}}~=~5.02 TeV

    Author
    Publication venue
    Springer Verlag (Germany)
    Publication date
    Field of study
    No full text
    International audienceThe coherent photoproduction of J/ψ\rm{J/\psi} and ψ′\rm{\psi'} mesons was measured in ultra-peripheral Pb-Pb collisions at a center-of-mass energy sNN = 5.02\sqrt{s_{\mathrm{NN}}}~=~5.02 TeV with the ALICE detector. Charmonia are detected in the central rapidity region for events where the hadronic interactions are strongly suppressed. The J/ψ\rm{J/\psi} is reconstructed using the dilepton (l+l−l^{+} l^{-}) and proton-antiproton decay channels, while for the ψ′\rm{\psi'}, the dilepton and the l+l−π+π−l^{+} l^{-} \pi^{+} \pi^{-} decay channels are studied. The analysis is based on an event sample corresponding to an integrated luminosity of about 233 μb−1{\mu b}^{-1}. The results are compared with theoretical models for coherent J/ψ\rm{J/\psi} and ψ′\rm{\psi'} photoproduction. The coherent cross section is found to be in a good agreement with models incorporating moderate nuclear gluon shadowing of about 0.65 at a Bjorken-xx of around 6×10−46\times 10^{-4}, such as the EPS09 parametrization, however none of the models is able to fully describe the rapidity dependence of the coherent J/ψ\rm{J/\psi} cross section including ALICE measurements at forward rapidity. The ratio of ψ′\rm{\psi'} to J/ψ\rm{J/\psi} coherent photoproduction cross sections was also measured and found to be consistent with the one for photoproduction off protons

    Multiharmonic Correlations of Different Flow Amplitudes in Pb-Pb Collisions at sNN=2.76\sqrt{s_{_{NN}}}=2.76  TeV

    Author
    Publication venue
    American Physical Society
    Publication date
    Field of study
    No full text
    International audienceThe event-by-event correlations between three flow amplitudes are measured for the first time in Pb-Pb collisions, using higher-order symmetric cumulants. We find that different three-harmonic correlations develop during the collective evolution of the medium when compared to correlations that exist in the initial state. These new results cannot be interpreted in terms of previous lower-order flow measurements since contributions from two-harmonic correlations are explicitly removed in the new observables. A comparison to Monte Carlo simulations provides new and independent constraints for the initial conditions and system properties of nuclear matter created in heavy-ion collisions

    New highly radioactive particles derived from Fukushima Daiichi Reactor Unit 1: Properties and environmental impacts

    Author
    Publication venue
    Elsevier
    Publication date
    Field of study
    No full text
    International audienceA contaminated zone elongated toward Futaba Town, north-northwest of the Fukushima Daiichi Nuclear Power Plant (FDNPP), contains highly radioactive particles released from reactor Unit 1. There are uncertainties associated with the physio-chemical properties and environmental impacts of these particles. In this study, 31 radioactive particles were isolated from surface soils collected 3.9 km north-northwest of the FDNPP. Two of these particles have the highest particle-associated 134+137Cs activity ever reported for Fukushima (6.1 × 105 and 2.5 × 106 Bq per particle after decay-correction to March 2011). The new, highly-radioactive particle labeled FTB1 is an aggregate of flaky silicate nanoparticles with an amorphous structure containing ~0.8 wt% Cs, occasionally associated with SiO2 and TiO2 inclusions. FTB1 likely originates from the reactor building, which was damaged by a H2 explosion, after adsorbing volatilized Cs. The 134+137Cs activity in the other highly radioactive particle labeled FTB26 exceeded 106 Bq. FTB26 has a glassy carbon core and a surface that is embedded with numerous micro-particles: Pb–Sn alloy, fibrous Al-silicate, Ca-carbonate or hydroxide, and quartz. The isotopic signatures of the micro-particles indicate neutron capture by B, Cs volatilization, and adsorption of natural Ba. The composition of the micro-particles on FTB26 reflects the composition of airborne particles at the moment of the H2 explosion. Owing to their large size, the health effects of the highly radioactive particles are likely limited to external radiation during static contact with skin; the highly radioactive particles are thus expected to have negligible health impacts for humans. By investigating the mobility of the highly radioactive particles, we can better understand how the radiation dose transfers through environments impacted by Unit 1. The highly radioactive particles also provide insights into the atmospheric conditions at the time of the Unit 1 explosion and the physio-chemical phenomena that occurred during reactor meltdown

    Iodine local environment in high pressure borosilicate glasses: An X-ray photoelectron spectroscopy and X-ray absorption spectroscopy investigation

    Author
    Publication venue
    Elsevier
    Publication date
    Field of study
    No full text
    International audience• Iodine is dissolved as iodide (I − ) in high pressure borosilicate glasses. • Both alkali and alkaline-earth cations act as a charge compensator to I − species. • The absence of iodate (I 5+ ) suggests that there is a complex interplay between I − species and oxygen species within the glass structure

    Energy dependence of ϕ\phi meson production at forward rapidity in pp collisions at the LHC

    Author
    Publication venue
    Springer Verlag (Germany)
    Publication date
    Field of study
    No full text
    International audienceThe production of ϕ\phi mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region 2.5<y<42.5< y < 4. Measurements of the differential cross section d2σ/dydpT\mathrm{d}^2\sigma /\mathrm{d}y \mathrm{d}p_{\mathrm {T}} are presented as a function of the transverse momentum (pTp_{\mathrm {T}}) at the center-of-mass energies s=5.02\sqrt{s}=5.02, 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at s=5.02\sqrt{s}=5.02 and 13 TeV are also studied in several rapidity intervals as a function of pTp_{\mathrm {T}}, and as a function of rapidity in three pTp_{\mathrm {T}} intervals. A hardening of the pTp_{\mathrm {T}}-differential cross section with the collision energy is observed, while, for a given energy, pTp_{\mathrm {T}} spectra soften with increasing rapidity and, conversely, rapidity distributions get slightly narrower at increasing pTp_{\mathrm {T}}. The new results, complementing the published measurements at s=2.76\sqrt{s}=2.76 and 7 TeV, allow one to establish the energy dependence of ϕ\phi meson production and to compare the measured cross sections with phenomenological models. None of the considered models manages to describe the evolution of the cross section with pTp_{\mathrm {T}} and rapidity at all the energies

    Commissioning of the Muon Forward Tracker and preparation of data analysis (LHC, CERN)

    Author
    Publication venue
    HAL CCSD
    Publication date
    Field of study
    No full text
    National audienc

    Inclusive J/ψ\text {J}/\psi production at midrapidity in pp collisions at s=13\sqrt{s} = 13 TeV

    Author
    Publication venue
    Springer Verlag (Germany)
    Publication date
    Field of study
    No full text
    International audienceWe report on the inclusive J/ψ\text {J}/\psi production cross section measured at the CERN Large Hadron Collider in proton–proton collisions at a center-of-mass energy s = 13\sqrt{s}~=~13 TeV. The J/ψ\text {J}/\psi mesons are reconstructed in the e+e−\text {e}^{+}\text {e}^{-} decay channel and the measurements are performed at midrapidity (∣y∣<0.9|y|<0.9) in the transverse-momentum interval 0<pT<400<p_{\mathrm{T}} <40 GeV/cc, using a minimum-bias data sample corresponding to an integrated luminosity Lint=32.2 nb−1L_{\text {int}} = 32.2~\text {nb}^{-1} and an Electromagnetic Calorimeter triggered data sample with Lint=8.3 pb−1L_{\text {int}} = 8.3~\mathrm {pb}^{-1}. The pTp_{\mathrm{T}}-integrated J/ψ\text {J}/\psi production cross section at midrapidity, computed using the minimum-bias data sample, is dσ/dy∣y=0=8.97±0.24 (stat)±0.48 (syst)±0.15 (lumi) μb\text {d}\sigma /\text {d}y|_{y=0} = 8.97\pm 0.24~(\text {stat})\pm 0.48~(\text {syst})\pm 0.15~(\text {lumi})~\mu \text {b}. An approximate logarithmic dependence with the collision energy is suggested by these results and available world data, in agreement with model predictions. The integrated and pTp_{\mathrm{T}}-differential measurements are compared with measurements in pp collisions at lower energies and with several recent phenomenological calculations based on the non-relativistic QCD and Color Evaporation models

    Ten years after the NPP accident at Fukushima : review on fuel debris behavior in contact with water

    Author
    Publication venue
    HAL CCSD
    Publication date
    Field of study
    No full text
    International audienceFollowing the NPP accident, several hundred tons of heat-generating corium and fuel debris have been cooled permanently by millions of m3 of flowing. Knowledge on the interaction with water is cruc..

    Spin7 instantons in 8 dimensions

    Author
    Publication venue
    HAL CCSD
    Publication date
    Field of study
    No full text
    International audienc

    Charm 10th Charm in media (theory)

    Author
    Publication venue
    HAL CCSD
    Publication date
    Field of study
    No full text
    International audienc

    875

    full texts

    7,271

    metadata records
    Updated in last 30 days.
    HAL Mines Nantes
    Access Repository Dashboard
    Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇