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    Measurement of electrons from beauty-hadron decays in <math><mrow><mi>p</mi><mi>p</mi></mrow></math> and Pb-Pb collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>5.02</mn></mrow></math> TeV

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    HAL CCSD
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    International audienceThe production of electrons from beauty-hadron decays was measured at midrapidity in proton-proton (pp) and central Pb-Pb collisions at center-of-mass energy per nucleon-nucleon pair sNN = 5.02 TeV, using the ALICE detector at the LHC. The cross section measured in pp collisions in the transverse momentum interval 2&lt;pT&lt;8GeV/c was compared with models based on perturbative quantum chromodynamics calculations. The yield in the 10% most central Pb-Pb collisions, measured in the interval 2&lt;pT&lt;26GeV/c, was used to compute the nuclear modification factor RAA, extrapolating the pp reference cross section to pT larger than 8 GeV/c. The measured RAA shows significant suppression of the yield of electrons from beauty-hadron decays at high pT and does not show a significant dependence above 8GeV/c within uncertainties. The results are described by several theoretical models based on different implementations of the interaction of heavy quarks with a quark-gluon plasma, which predict a smaller energy loss for beauty quarks compared to light and charm quarks

    Dielectron production in central Pb−-Pb collisions at sNN\sqrt{s_\mathrm{NN}} = 5.02 TeV

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    HAL CCSD
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    International audienceThe first measurement of the e+^+e−^- pair production at midrapidity and low invariant mass in central Pb−-Pb collisions at sNN=5.02\sqrt{s_{\mathrm{NN}}}=5.02 TeV at the LHC is presented. The yield of e+^+e−^- pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass (meem_{\rm ee}) and pair transverse momentum (pT,eep_{\rm T,ee}) ranges mee<3.5m_{\rm ee} < 3.5 GeV/c2/c^2 and pT,ee<8p_{\rm T,ee} < 8 GeV/c/c. For 0.18<mee<0.50.18 < m_{\rm ee} < 0.5 GeV/c2/c^2 the ratio of data to the cocktail of hadronic contributions without ρ\rho mesons amounts to 1.42±0.12 (stat.)±0.17 (syst.)±0.12 (cocktail)1.42 \pm 0.12 \ ({\rm stat.}) \pm 0.17 \ ({\rm syst.}) \pm 0.12 \ ({\rm cocktail}) and 1.44±0.12 (stat.)±0.17 (syst.)−0.21+0.17 (cocktail)1.44 \pm 0.12 \ ({\rm stat.}) \pm 0.17 \ ({\rm syst.}) ^{+0.17}_{-0.21} \ ({\rm cocktail}), including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an additional contribution of thermal e+^+e−^- pairs from the hadronic and partonic phases. In the intermediate-mass range (1.2<mee<2.61.2 < m_{\rm ee} < 2.6 GeV/c2/c^2), the pair transverse impact parameter of the e+^+e−^- pairs (DCAee_{\rm ee}) is used for the first time in Pb−-Pb collisions to separate displaced dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction point. The data are consistent with a suppression of e+^+e−^- pairs from cc‾{\rm c\overline{c}} and an additional prompt component. Finally, the first direct-photon measurement in the 10% most central Pb−-Pb collisions at sNN=5.02\sqrt{s_{\mathrm{NN}}}=5.02 TeV is reported via the study of virtual direct photons in the transverse momentum range 1<pT<51 < p_{\rm T} < 5 GeV/c/c. A model including prompt photons, as well as photons from the pre-equilibrium and fluid-dynamic phases, can reproduce the result, while being at the upper edge of the data uncertainties

    Classical vs. quantum corrections to jet broadening in a weakly coupled QGP

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    HAL CCSD
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    International audienceWe compute double-logarithmically enhanced corrections to q^\widehat{q} at relative order O(g2)O(g^2) in the setting of a weakly coupled quark-gluon plasma, observing how the thermal scale affects the region of phase space, which gives rise to these corrections. We furthermore clarify how the region of phase from which these corrections are borne is situated with respect to that from which the classical corrections arise at relative order O(g)O(g). This represents a significant step towards our eventual goal of understanding which class of corrections dominate, thereby pushing forward our quantitative grasp on the phenomenon of jet quenching in heavy-ion collisions

    Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector

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    American Physical Society
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    International audienceIn this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285 m long, high-finesse, near-detuned optical resonator. With about 8.5 dB of generated squeezing, up to 5.6 dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2 dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6 Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5 dB and 2 dB, respectively

    Improved Radio-Cesium Detection Using Quantitative Real-Time Autoradiography

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    ACS Publications
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    International audienceCesium-134 and -137 are prevalent, long-lived, radio-toxic contaminants released into the environment during nuclear accidents. Large quantities of insoluble, respirable Cs-bearing microparticles (CsMPs) were released into the environment during the Fukushima Daiichi nuclear accident. Monitoring for CsMPs in environmental samples is essential to understand the impact of nuclear accidents. The current detection method used to screen for CsMPs (phosphor screen autoradiography) is slow and inefficient. We propose an improved method: real-time autoradiography that uses parallel ionization multiplier gaseous detectors. This technique permits spatially resolved measurement of radioactivity while providing spectrometric data from spatially heterogeneous samples─a potential step-change technique for use after nuclear accidents for forensic analysis. With our detector configuration, the minimum detectable activities are sufficiently low for detecting CsMPs. Further, for environmental samples, sample thickness does not detrimentally affect detector signal quality. The detector can measure and resolve individual radioactive particles ≥465 μm apart. Real-time autoradiography is a promising tool for radioactive particle detection

    Inclusive psi(2S)-to-J/psi ratio at forward rapidity in pp collisions at sqrt(s) = 13.6 TeV with ALICE

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    HAL CCSD
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    International audienc

    Exploring new physics up to the MeV energy scale with XENONnT

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    HAL CCSD
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    International audienceThe XENON collaboration primarily focuses on detecting the first direct evidence for the existence of Dark Matter (DM) in the Universe using xenon double-phase time projection chamber detectors. The latest iteration of XENON experiments, XENONnT, is currently accumulating scientific data at the LNGS underground laboratory in Italy with a target mass of 5.9 tonnes of liquid xenon. The exceptional level of radioactivity reduction achieved in XENONnT makes it suitable for a broad range of rare-events searches beyond DM. Among these searches, the exploration of double-weak decays is of great interest. In particular, the Xe124 double electron capture and two-neutrino/neutrinoless double beta decay of Xe136 represent promising channels to investigate in XENONnT. These processes exhibit an expected electronic recoil signal that can reach up to the few MeV energy scale, which falls within a different region of interest than the standard DM search. We have demonstrated the ability of xenon dual-phase TPCs to conduct such research, validating the expansion of the physics reach accessible by this detector technology. This presentation will cover the latest results and current status of high-energy searches with the XENONnT experiment

    Elemental analysis by XRF and HE-PIXE on silver coins from the 16th-17th centuries and on a gilded crucifix from the 12th century

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    Springer
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    International audienceObjects from the Dobrée Museum (Grand Patrimoine de Loire- Atlantique, conservation unit), silver coins minted in Nantes between the years 1561 and 1599 and a twelfth-century fire-gilded crucifix were studied. The goal is to analyze trace elements in coins to determine silver sources and measure the thickness of the fire-gilding layer to provide information about the manufacturing technique of the crucifix. We focused on X-ray emission-based analysis, especially High Energy Particle Induced X-ray Emission (HE-PIXE) developed at Arronax cyclotron and handheld X-Ray Fluorescence (p-XRF) used at Arc’Antique laboratory. In this paper, four coins have been analyzed with HE-PIXE and p-XRF and three different locations on the crucifix. We detected indium and gold as silver markers in coins and we measured the thickness of the layer of gold on the crucifix. Those data are helpful to answer historical questions relative to the objects

    First measurement of the absorption of 3He‾^{3}\overline{\rm He} nuclei in matter and impact on their propagation in the galaxy

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    Nature Publishing Group [2005-....]
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    International audienceAntimatter particles such as positrons and antiprotons abound in the cosmos. Much less common are light antinuclei, composed of antiprotons and antineutrons, which can be produced in our galaxy via high-energy cosmic-ray collisions with the interstellar medium or could also originate from the annihilation of the still undiscovered dark-matter particles. On Earth, the only way to produce and study antinuclei with high precision is to create them at high-energy particle accelerators like the Large Hadron Collider (LHC). Though the properties of elementary antiparticles have been studied in detail, knowledge of the interaction of light antinuclei with matter is rather limited. This work focuses on the determination of the disappearance probability of \ahe when it encounters matter particles and annihilates or disintegrates. The material of the ALICE detector at the LHC serves as a target to extract the inelastic cross section for \ahe in the momentum range of 1.17≤p<101.17 \leq p < 10 GeV/cc. This inelastic cross section is measured for the first time and is used as an essential input to calculations of the transparency of our galaxy to the propagation of 3He‾^{3}\overline{\rm He} stemming from dark-matter decays and cosmic-ray interactions within the interstellar medium. A transparency of about 50% is estimated using the GALPROP program for a specific dark-matter profile and a standard set of propagation parameters. For cosmic-ray sources, the obtained transparency with the same propagation scheme varies with increasing 3He‾^{3}\overline{\rm He} momentum from 25% to 90%. The absolute uncertainties associated to the 3He‾^{3}\overline{\rm He} inelastic cross section measurements are of the order of 10%−-15%. The reported results indicate that 3He‾^{3}\overline{\rm He} nuclei can travel long distances in the galaxy, and can be used to study cosmic-ray interactions and dark-matter decays

    Constraining hadronization mechanisms with Λc+\rm \Lambda_{\rm c}^{+}/D0^0 production ratios in Pb-Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

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    HAL CCSD
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    International audienceThe production of prompt Λc+\rm \Lambda_{\rm c}^{+} baryons at midrapidity (∣y∣<0.5|y|<0.5) was measured in central (0-10%) and mid-central (30-50%) Pb-Pb collisions at the center-of-mass energy per nucleon-nucleon pair sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV with the ALICE detector. The Λc+\rm \Lambda_{\rm c}^{+} production yield, the Λc+\rm \Lambda_{\rm c}^{+}/D0^0 production ratio, and the Λc+\rm \Lambda_{\rm c}^{+} nuclear modification factor RAAR_{\rm AA} are reported. The results are more precise and more differential in transverse momentum (pTp_{\rm T}) and centrality with respect to previous measurements. The Λc+\rm \Lambda_{\rm c}^{+}/D0^0 ratio, which is enhanced with respect to the pp measurement for 4<pT<84< p_{\rm T} < 8 GeV/cc, is described by theoretical calculations that model the charm-quark transport in the quark-gluon plasma and include hadronization via both coalescence and fragmentation mechanisms

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