HAL-CEA
Not a member yet
145450 research outputs found
Sort by
Search for heavy long-lived charged particles with large ionization energy loss in proton-proton collisions at = 13 TeV
No full textInternational audienceA search for heavy, long-lived, charged particles with large ionization energy loss within the silicon tracker of the CMS experiment is presented. A data set of proton-proton collisions at a center of mass energy at = 13 TeV, collected in 2017 and 2018 at the CERN LHC, corresponding to an integrated luminosity of 101 fb, is used in this analysis. Two different approaches for the search are taken. A new method exploits the independence of the silicon pixel and strips measurements, while the second method improves on previous techniques using ionization to determine a mass selection. No significant excess of events above the background expectation is observed. The results are interpreted in the context of the pair production of supersymmetric particles, namely gluinos, top squarks, and tau sleptons, and of the Drell-Yan pair production of fourth generation (τ′) leptons with an electric charge equal to or twice the absolute value of the electron charge (e). An interpretation of a Z’ boson decaying to two τ′ leptons with an electric charge equal to 2e is presented for the first time. The 95% confidence upper limits on the production cross section are extracted for each of these hypothetical particles.[graphic not available: see fulltext
Search for high-mass resonances in a final state comprising a gluon and two hadronically decaying W bosons in proton-proton collisions at = 13 TeV
No full textInternational audienceA search for high-mass resonances decaying into a gluon, g, and two W bosons is presented. A Kaluza-Klein gluon, g, decaying in cascade via a scalar radion R, g → gR → gWW, is considered. The final state studied consists of three large-radius jets, two of which contain the products of hadronically decaying W bosons, and the third one the hadronization products of the gluon. The analysis is performed using proton-proton collision data at = 13 TeV collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of 138 fb. The masses of the g and R candidates are reconstructed as trijet and dijet masses, respectively. These are used for event categorization and signal extraction. No excess of data events above the standard model background expectation is observed. Upper limits are set on the product of the g production cross section and its branching fraction via a radion R to gWW. This is the first analysis examining the resonant WW+jet signature and setting limits on the two resonance masses in an extended warped extra-dimensional model.[graphic not available: see fulltext
Evidence for violation and measurement of -violating parameters in B J/(1020) decays in pp collisions at 13 TeV
No full textInternational audienceA pioneering machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27000 tagged B J/(1020) decays from pp collisions at 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 96.5 fb. A time- and flavor-dependent angular analysis of the KK final state is used to measure parameters of the - system. The weak phase is measured to be = 73 23 (stat) 7 (syst) mrad, which, combined with a = 8 TeV CMS result, gives = 74 23 mrad. This value differs from zero by 3.2 standard deviations, providing evidence for violation in B J/(1020) decays. All measured physics parameters are found to agree with standard model predictions where available
Future Circular Collider Feasibility Study Report: Volume 3, Civil Engineering, Implementation and Sustainability: Volume 3 Civil Engineering, Implementation and Sustainability
No full textInternational audienceVolume 3 of the FCC Feasibility Report presents studies related to civil engineering, the development of a project implementation scenario, and environmental and sustainability aspects. The report details the iterative improvements made to the civil engineering concepts since 2018, taking into account subsurface conditions, accelerator and experiment requirements, and territorial considerations. It outlines a technically feasible and economically viable civil engineering configuration that serves as the baseline for detailed subsurface investigations, construction design, cost estimation, and project implementation planning. Additionally, the report highlights ongoing subsurface investigations in key areas to support the development of an improved 3D subsurface model of the region. The report describes development of the project scenario based on the 'avoid-reduce-compensate' iterative optimisation approach. The reference scenario balances optimal physics performance with territorial compatibility, implementation risks, and costs. Environmental field investigations covering almost 600 hectares of terrain - including numerous urban, economic, social, and technical aspects - confirmed the project's technical feasibility and contributed to the preparation of essential input documents for the formal project authorisation phase. The summary also highlights the initiation of public dialogue as part of the authorisation process. The results of a comprehensive socio-economic impact assessment, which included significant environmental effects, are presented. Even under the most conservative and stringent conditions, a positive benefit-cost ratio for the FCC-ee is obtained. Finally, the report provides a concise summary of the studies conducted to document the current state of the environment
First Measurement of <math display="inline"><mi>A</mi><mo>=</mo><mn>4</mn></math> Hypernuclei and Antihypernuclei at the LHC
No full textInternational audienceIn this Letter, the first evidence of the antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number , specifically (anti) and (anti). In addition, the antiparticle-to-particle ratios for both hypernuclei ( and ) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb--Pb collisions, collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of \sqrt{s_{\mathrm{NN}}} = \SI{5.02}{\tera\electronvolt}. The yields measured for the average of the charge-conjugated states are found to be for the (anti) and for the (anti), and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of (anti) and (anti) excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within with the present measurements. Additionally, the measured (anti) and (anti) masses are compatible with the world-average values within the uncertainties
Spectroscopy of Strange Mesons and First Observation of a Strange Crypto-Exotic State with
No full textInternational audienceWe measured the strange-meson spectrum in the scattering reaction with the COMPASS spectrometer at CERN. Using the world's largest sample of this reaction, we performed a comprehensive partial-wave analysis of the mesonic final state. It substantially extends the strange-meson spectrum covering twelve states with masses up to 2.4 GeV/. We observe the first candidate for a crypto-exotic strange meson with and find and states consistent with predictions for the ground states
Changes in Antarctic surface conditions and potential for ice shelf hydrofracturing from 1850 to 2200
No full textInternational audienceA mixed statistical-physical approach is used to emulate the spatio-temporal variability of the Antarctic Ice Sheet surface mass balance and surface melt rates of a regional climate model. We demonstrate the ability of this simple method to extend existing regional climate simulations to periods, scenarios, or climate models that were not originally simulated. This method is useful to quickly populate ensembles of surface mass balance and melt rates, which are needed to constrain ice sheet model ensembles. Here we apply this method to estimate (i) the changes in Antarctic surface mass balance over 1850-2200 and the associated effect on sea level and (ii) the changes in potential for ice shelf hydrofracturing.After weighting 16 climate models to obtain a realistic distribution of the equilibrium climate sensitivity, we find a likely contribution of surface mass balance to sea level rise of -2.2 to -0.4 cm from 1900 to 2010 and -3.4 to -0.1 cm from 2000 to 2099 under the SSP1-2.6 scenario versus -4.4 to -1.4 cm under SSP2-4.5, and -7.8 to -4.0 cm under SSP5-8.5. The contribution from 2000 to 2200 is highly uncertain: between -10 and -1 cm in SSP1-2.6 and between -33 and +6 cm in SSP5-8.5 depending on the climate model.Based on a criterion on the presence of liquid water beyond firn saturation in our emulated ensemble, we estimate the surface conditions that make ice shelves prone to hydrofracturing. Our results suggest that a majority of Antarctic ice shelves could remain safe from hydrofracturing under the SSP1-2.6 scenario, but all of them could become prone to hydrofracturing before 2150 under the SSP5-8.5 scenario.</p
Imaging biomineralizing bacteria in the native-state with X-ray fluorescence microscopy
No full textInternational audienceUnderstanding the interactions between metal-based nanoparticles and biological systems in complex environments (e.g., the human body, soils, and marine settings) remains challenging, especially at the single-cell and nanoscale levels. Capturing the dynamics of these interactions, such as metal distribution, nanoparticle growth, or degradation, in their native state (in vivo) is particularly difficult. Here, we demonstrate the direct measurement of iron content in hydrated, magnetite-biomineralizing magnetotactic bacteria using synchrotron-based nanobeam–scanning X-ray fluorescence microscopy combined with a liquid cell environment. In addition to X-ray fluorescence imaging, we collected iron chemical speciation information from individual bacteria in liquid using X-ray absorption spectroscopy. To follow biomineralization in situ, we developed a microfluidic device to track magnetite nanoparticle formation over several hours under the X-ray beam. This approach highlights the potential of X-ray fluorescence microscopy in liquid cell setups to provide elemental and chemical insights into biological processes at the single-cell level. Combining X-ray nanobeam techniques with liquid cell devices will enable more “on-chip” experiments on metals in biological contexts to be conducted at the synchrotron
Characterization and performance of the Apollon main short-pulse laser beam following its commissioning at 2 PW level
No full textInternational audienceWe present the results of the second commissioning phase of the short-focal-length area of the Apollon laser facility, located in Saclay, France. This phase was conducted using the main laser beam (F1), scaled to a peak power of 2 PetaWatts. Under the tested conditions, the F1 beam delivered on-target pulses with a maximum energy of up to 45 J and a duration of 22 fs. Several diagnostics were deployed to assess the facilitys performance. Key measurements included the on-target focal spot and its spatial stability, along with characterizations of secondary sources generated by irradiating solid targets. These evaluations aim at assisting users in designing future experiments. The laser-target interactions were thoroughly characterized, with emissions of energetic ions, X-rays, and neutrons recorded, demonstrating good laser-to-target coupling efficiency. Additionally, we successfully demonstrated the simultaneous operation of the F1 beam with the auxiliary 0.5 PW F2 beam of Apollon, enabling dual-beam operation. This commissioning phase paves the way for the next stage in 2025, which will involve scaling the F1 beam to 8 PW, progressing towards the ultimate goal of achieving 10 PW power
Ultralow-Temperature Thermodynamics and Optical Coherence of Narrow Linewidth Optical Emitters
No full textThe coherence properties of optical emitters in crystals are critical for quantum technologies and optical frequency metrology. Cooling to sub-kelvin temperatures can significantly enhance their coherence, making it essential to identify the key parameters governing emitter and host crystal behavior in this ultra cold regime. We investigate a Czochralski-grown europium doped yttrium orthosilicate crystal, and we report measurements of the heat capacity, a parameter fundamental to evaluating thermal noise limits in metrology schemes based on spectral hole stabilization in such samples. In parallel, we characterize optical coherence via photon echo measurements as a function of temperature. Below 1 K, where phonon contributions diminish, two-level systems (TLS) associated with crystal imperfections may emerge as a limiting factor. A linear-in-temperature term in the heat capacity serves as a signature of TLS, and from our data, we establish an upper bound on this contribution. This, combined with the optical homogeneous linewidth from photon-echo measurements being constant in the interval from 300 mK to 2 K demonstrates a minimal TLSrelated effects in our sample. These findings highlight the promise of ultralow-temperature operation for enhancing the performance of optical quantum devices based on doped crystals