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Charm production and fragmentation fractions at midrapidity in pp collisions at TeV
No full textInternational audienceMeasurements of the production cross sections of prompt , , , , , and charm hadrons at midrapidity in protonproton collisions at TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum () are provided with improved precision and granularity. The ratios of -differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken- (). The measurements of () baryon production extend the measured intervals down to ~GeV. These measurements are used to determine the charm-quark fragmentation fractions and the production cross section at midrapidity () based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons , , , , and, for the first time, , and of the strongly-decaying J/ mesons. The first measurements of and fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to ee and ep collisions. The production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations
Thermal dilepton production in heavy-ion collisions at beam-energy-scan (BES) energies
No full textInternational audienceThe lepton pair production rate at finite temperature and at next-to-leading-order (NLO) is calculated for quark-gluon plasma at non-zero baryon density. Yields are obtained using a (3+1)D multicomponent simulation capable of reproducing hadronic observables measured in the RHIC Beam Energy Scan. Spectra of intermediate invariant mass dileptons are compared with measurements from the STAR collaboration. The result of a study where the temperature information obtained from the dilepton spectrum from heavy-ion collisions performed at different energies and centralities is presented
Photoproduction of J/psi and dileptons in events with nuclear overlap
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Measurement of (2S) production as a function of charged-particle pseudorapidity density in pp collisions at = 13 TeV and p-Pb collisions at = 8.16 TeV with ALICE at the LHC
No full textInternational audienceProduction of inclusive charmonia in pp collisions at center-of-mass energy of = 13 TeV and p–Pb collisions at center-of-mass energy per nucleon pair of = 8.16 TeV is studied as a function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states (J/ψ, ψ(2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2.5 < y< 4.0 for pp collisions, and 2.03 < y< 3.53 and −4.46 < y< −2.96 for p–Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (|η| < 1.0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The ψ(2S) yield increases with the charged-particle pseudorapidity density. The ratio of ψ(2S) over J/ψ yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of J/ψ and ψ(2S) yields with respect to charged-particle pseudorapidity density. Results for the ψ(2S) yield and its ratio with respect to J/ψ agree with available model calculations.[graphic not available: see fulltext
Hydrogen Peroxide (H2O2) production in response to multiple beam irradiation of protons at UHDR
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Two-particle transverse momentum correlations in <math><mrow><mi>p</mi><mi>p</mi></mrow></math> and <math><mi>p</mi></math>-Pb collisions at energies available at the CERN Large Hadron Collider
No full textInternational audienceTwo-particle transverse momentum differential correlators, recently measured in Pb-Pb collisions at energies available at the CERN Large Hadron Collider (LHC), provide an additional tool to gain insights into particle production mechanisms and infer transport properties, such as the ratio of shear viscosity to entropy density, of the medium created in Pb-Pb collisions. The longitudinal long-range correlations and the large azimuthal anisotropy measured at low transverse momenta in small collision systems, namely pp and p-Pb, at LHC energies resemble manifestations of collective behavior. This suggests that locally equilibrated matter may be produced in these small collision systems, similar to what is observed in Pb-Pb collisions. In this work, the same two-particle transverse momentum differential correlators are exploited in pp and p-Pb collisions at s=7TeV and sNN=5.02TeV, respectively, to seek evidence for viscous effects. Specifically, the strength and shape of the correlators are studied as a function of the produced particle multiplicity to identify evidence for longitudinal broadening that might reveal the presence of viscous effects in these smaller systems. The measured correlators and their evolution from pp and p-Pb to Pb-Pb collisions are additionally compared to predictions from Monte Carlo event generators, and the potential presence of viscous effects is discussed
Latest development of α emitter imaging and quantification on a large Field Of View
No full textInternational audienceCurrently, the characterization of the nature and spatial distribution of radionuclides in a sample is time consuming and fastidious. Indeed, it necessarily requires the use of two distinct analytical techniques and detectors of a different nature. Moreover, the resolutions of the two methods are often different from each other because they also depend on the nature of the detector used, which makes it difficult to integrate and interpret these two types of measurements together.To overcome these limitations and to simplify and accelerate the measurement process, it is now possible to use a digital autoradiograph capable of combining the measurement of the spatial distribution with the ability to separate and quantify each radionuclide.For this purpose, a set of temporal and energy spectrometry techniques had to be specifically developed. On the one hand, the use of instruments capable of recording the location of each decay product allows measuring the evolution of the activity of the sample and thus, to deduce the contributions of several radionuclides. On the other hand, the development of an innovative method of autoradiography spectroscopy in particle energy also allows separating them by measuring their initial energy. Even if the efficiency of energy spectrum reconstruction is low (4.4%) compared to the efficiency of a simple autoradiograph (50%), this novel measurement approach offers the opportunity to select areas on an autoradiograph to perform an energy spectrum analysis within that area.From an application point of view, this opens up possibilities for theragnostic applications that typically use two radionuclides. Further upstream, it can optimize the production and distribution challenge of α radionuclides by allowing the identification and characterization of individual radionuclides in radionuclide chains such as 225Ac
Cluster formation near midrapidity - can the mechanism be identified experimentally?
No full textInternational audienceThe formation of weakly bound clusters in the hot and dense environment at midrapidity is one of the surprising phenomena observed experimentally in heavy-ion collisions from a low center of mass energy of =2.5 GeV up to a ultra-relativistic energy of =5 TeV. Three approaches have been advanced to describe the cluster formation: coalescence at kinetic freeze-out, cluster formation during the entire heavy-ion collision by potential interaction between nucleons and deuteron production by hadronic reactions. We identify experimental observables, which can discriminate these production mechanisms for deuterons
Tailoring an efficient computational methodology for studying ligand interactions with heavy radiometals in solution: the case of radium
No full textThe availability of metallic radioelements, with only short-lived isotopes, at trace quantities, does not allow simple, straightforward evaluation of their chemical properties, although they represent societal issues of primary importance (environmental contamination, uses in nuclear medicine, etc.). A strategy is presented to establish a cost-effective computational methodology that is radiometal-specific and accurate to supplement the limited experimental data with a focus on complexation properties. With radium as application, the most suitable DFT methods have been selected by comparison with structures and interaction energies determined by state-of-the-art calculations. Scarce Ra2+ complexation constants are available, but combined through isodesmic-like reactions (e.g. transmetallation), they allow for error cancellation mechanisms. Then, a radiometal-specific cavity is fitted in an implicit solvent model to reproduce solvation effects. The equilibrium constants can finally be calculated accurately, i.e. with a precision of 1 logarithmic unit, provided that the relativistic spin–orbit interaction is taken into account. The relevance of this methodology is illustrated with macropa, an 18-membered macrocyclic ligand recently considered for developing 223Ra radiotherapeutics, highlighting that the design of an innovative chelator by assuming transferability of neighboring element chemistry can only be suboptimal
The DMAPS upgrade of the Belle II vertex detector
No full textInternational audienceThe Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028. One proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk). This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development