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The hadronic contribution to the running of and the electroweak mixing angle
No full textWe report on our update to \cite{Ce:2022eix} on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole.We report on our update to [1] on the hadronic running of electroweak couplings from -improved Wilson fermions with flavours. The inclusion of additional ensembles at very fine lattice spacings together with a number of techniques to split the different contributions for a better control of cutoff effects allows us to substantially improve the precision. We employ two different discretizations of the vector current to compute the subtracted Hadronic Vacuum Polarization (HVP) functions and for Euclidean time momenta up to . To reduce cutoff effects in the short distance region we apply a suitable subtraction to the TMR kernel function, which cancels the leading behaviour. The subtracted term is then computed in perturbative QCD using the Adler function and added back to compensate for the subtraction. Chiral-continuum extrapolations are performed with five values of the lattice spacing and several pion masses, including its physical value, and several fit ansätze are explored to estimate the systematics arising from model selection. Our results show excellent prospects for high-precision estimates of at the Z-pole
Radiological Zoning and Clearance Methodology of activated cables in the LHC accelerator at CERN
No full textIn the context of upgrading the Large Hadron Collider (LHC) to its High-Luminosity (HL-LHC) configuration, it is essential to conduct a thorough zoning classification and characterization of activated cables within the particle accelerator. To address this need, a methodology was developed to identify regions where materials can be cleared from regulatory control in compliance with the Swiss Radiation Protection Legislation. The study begins with optimizing the elemental composition of cables and validating Monte Carlo FLUKA simulations using high-energy resolution gamma spectrometry (GS) and total gamma counting (TGC) measurements on 19 copper cable samples, collected during the winter shutdown 2023/2024. This methodology enables performing radiological zoning and accurately defines the radiological classification of the cables installed in the LHC Points 1 and 5, including both the accelerator tunnel and service galleries, prior to dismantling. Finally, the study proposes a conservative scaling factor for cable zoning and introduces a TGC figure of merit (FOM), representing a conservative activation scenario for the copper cable types. •Developed a methodology for optimizing radioactive waste from activated cables.•Radiological zoning for activated cables in LHC during HL-LHC upgrade.•Optimized elemental compositions of cables using gamma spectrometry.•Validated FLUKA simulations with gamma spectrometry for accurate radiological classification.•Proposed a FOM for total gamma counting to benchmark copper cable activation.In the context of upgrading the Large Hadron Collider (LHC) to its High-Luminosity (HL-LHC) configuration,
it is essential to conduct a thorough zoning classification and characterization of activated cables within the
particle accelerator. To address this need, a methodology was developed to identify regions where materials
can be cleared from regulatory control in compliance with the Swiss Radiation Protection Legislation.
The study begins with optimizing the elemental composition of cables and validating Monte Carlo
FLUKA simulations using high-energy resolution gamma spectrometry (GS) and total gamma counting (TGC)
measurements on 19 copper cable samples, collected during the winter shutdown 2023/2024.
This methodology enables performing radiological zoning and accurately defines the radiological classification of the cables installed in the LHC Points 1 and 5, including both the accelerator tunnel and service
galleries, prior to dismantling.
Finally, the study proposes a conservative scaling factor for cable zoning and introduces a TGC figure of
merit (FOM), representing a conservative activation scenario for the copper cable types
Optimized BiSiO scintillation crystals grown in dynamic atmosphere for future particle physics experiments
No full textThis work deals with the optimization of bismuth silicate, Bi4Si3O12 (BSO) scintillation crystals as candidates for future high energy physics experiments at colliders involving the registration of both scintillation and Cherenkov light. Crystals with a high transparency in UV-band and a high timing resolution are required for this application. Czochralski process was employed for BSO crystal growth in Pt crucibles in a dynamic growth atmosphere. After the growth of a series of crystals in air, as well as mixed Ar-air static and dynamic atmospheres, it was shown that the mixed atmosphere minimizes Bi2O3 evaporation and reduces the amount of Pt dissolved in the melt by several times. This caused the reduction in the number of foreign inclusions in the grown crystals, providing a transparency of over 70 % in the > 300 nm range, a light output of up to 2140 ph/MeV, an energy resolution of 21.5 % at 662 keV γ-rays, while a coincidence time resolution was improved from 148 to 125 ps. •Performance of BSO crystals is enhanced by growth atmosphere optimization.•Dynamic growth atmosphere provides minimization of Bi2O3 evaporation and Pt losses.•Enhanced transparency at > 290 nm favors efficient registration of Cherenkov light.•Coincidence time resolution of 125 ps is achieved in BSO
Optimizing the Quench Protection of a 13 T NbSn Common-Coil Magnet
No full textA 13 T NbSn common-coil accelerator-type magnet is being developed at the Paul Scherrer Institute (PSI). The magnet cross-section features an innovative design with asymmetric elements and effective stress-management. Thanks to the asymmetric design narrow pole racetrack coils are not required in proximity of the magnet apertures to improve the field quality. Its magnetic design achieves adequate margin with respect to the short-sample limit while utilizing two available cables. This choice accelerates the completion of the 0.8 m long demonstrator magnet, but limits the flexibility of the conductor grading and makes the magnet quench protection more challenging. In this contribution, the strategy to limit the hot-spot temperature and peak voltage to ground reached in the magnet conductor after a quench is discussed. The electro-magnetic and thermal transients occurring during a quench discharge are simulated with the STEAM-LEDET program. Quench detection based on differential-voltage monitoring is proposed, and the expected quench detection times are evaluated in the case of quenches occurring in different coil locations. Furthermore, the performances of various quench protection systems, including energy-extraction based either on a resistor or a varistor, a CLIQ (Coupling-Loss Induced Quench) system, or combinations of these are assessed. It is shown that while energy-extraction is a viable option to protect the magnet, acceptable performance can be achieved with CLIQ while achieving a significantly lower peak voltage to ground. The lowest hot-spot temperature is obtained by combining energy extraction and CLIQ
Observation of the (2012) baryon at the LHC
No full textA signal consistent with the (2012) baryon has been observed with a significance of in pp collisions at TeV at the LHC. In this paper, the analysis technique is described and measurements of the mass and width of the (2012) are reported, along with the first measurement of its transverse-momentum spectrum and yield. This paper corroborates the observation by Belle of this excited state and the observation that the (2012) has a rather narrow width for a strongly decaying resonance. The yield measurement is combined with a statistical thermal model calculation of strange baryon yield ratios to obtain estimates of the branching ratios. These results will improve our understanding of the internal structure and mass spectrum of excited baryon states and serve as a baseline for searches regarding modifications of these properties in high-temperature media.A signal consistent with the (2012) baryon has been observed with a significance of in pp collisions at TeV at the LHC. In this paper, the analysis technique is described and measurements of the mass and width of the (2012) are reported, along with the first measurement of its transverse-momentum spectrum and yield. This paper corroborates the observation by Belle of this excited state and the observation that the (2012) has a rather narrow width for a strongly decaying resonance. The yield measurement is combined with a statistical thermal model calculation of strange baryon yield ratios to obtain estimates of the branching ratios. These results will improve our understanding of the internal structure and mass spectrum of excited baryon states and serve as a baseline for searches regarding modifications of these properties in high-temperature media
CMS jet measurements and constraints on PDFs and
No full textA selection of recent jet measurements in proton-proton collisionsfrom the CMS Collaboration at the CERN LHC is presented.Several experimental results targeting jet production are summarized, includingdifferential measurements of the inclusive jet cross section at center-of-massenergies of = 13 TeV and 5.02 TeV, and of the dijet cross sectionat = 13 TeV.The measurements are compared to state-of-the-art theoretical predictionsat next-to-next-to-leading-order accuracy in perturbative QCD, and the strong couplingconstant is extracted simultaneously with the parton distribution functions (PDFs)of the proton at 13 TeV.A further experimental handle on is provided by a measurement of jetazimuthal correlations.Finally, a novel measurement of the energy-energy correlators inside jets is outlined. These providean additional way of determining while also constituting useful observables forprobing phase spaces dominated by nonperturbative processes like hadronization and haveapplications in the context of Monte Carlo event generator tuning
Signal shape studies and rate dependence of HFO-based gas mixtures in RPC detectors
No full textThe RPCs employed at the LHC experiments are currently operated in avalanche mode, with a mixture containing a large fraction of CHF (90% or more) with the addition of i-CH and SF in different concentrations. However, CHF and SF are fluorinated greenhouse gases (F-gases) with Global Warming Potential (GWP) of 1400 and 22800, respectively. EU regulations imposed a progressive phase-down of CHF production and consumption, aiming at strongly reducing its emission. This is already resulting in an increase of its price and reduction in availability. The most desirable long-term solution to this problem is to find an alternative, F-gases-free gas mixture, able to maintain similar detector performance. To address this challenge, the RPC ECOGasas@GIF++ collaboration (including RPC experts of ALICE, ATLAS, CMS, SHiP/LHCb, and the CERN EP-DT group) was created in 2019. The collaboration is currently studying a gas from the olefine family, the CHF (or simply HFO, with GWP 6), to be used, in combination with CO, as a substitute for CHF. This contribution will focus on the signal shape studies that have been carried out by the collaboration during dedicated beam test periods. The methodology used in the data analysis will be presented, together with the results obtained with several HFO-based gas mixtures, and with the currently employed one. Furthermore, results on the counting-rate dependence of the RPC performance, obtained by combining the muon beam with the GIF++ Cs source with different attenuation factors, will also be presented
Anomalous Dimension of a General Effective Gauge Theory I: Bosonic Sector
No full textWe classify the physical operators of the most general bosonic effective gauge theory up to dimension six using on-shell methods. Based on this classification, we compute the complete one-loop anomalous dimension employing both on-shell unitarity-based and geometric techniques. Our analysis fully accounts for the mixing of operators with different dimensions. The results broadly apply to any Effective Field Theory with arbitrary gauge symmetry and bosonic degrees of freedom. To illustrate their utility, we perform a complete cross-check of results on the renormalization of the Standard Model Effective Field Theory (SMEFT), scalar theory, and the SMEFT extended with an axion-like particle. Additionally, we present new results for axion-like particles with CP-violating interactions
Operational Experience and Performance with the ATLAS Pixel detector at the Large Hadron Collider at CERN
No full textThe tracking performance of the ATLAS detector relies critically on its 4-layer Pixel Detector. Its original part consisting in 3 layers of planar pixel sensor is continuously operating since the start of LHC collisions in 2009, while its innermost layer, the Insertable B Layer (IBL) at about 3 cm from the beam line, was installed in 2014 before the start of LHC Run2 and consists of both planar and 3D pixel sensors. As the closest detector component to the interaction point, this detector is subjected to a significant amount of radiation over its lifetime. At present, at the end of 2024 Run3 LHC collisions, ATLAS Pixel Detector on innermost layers, is operating after integrating fluence of O(10**15) 1 MeV n_eq cm-2. The ATLAS collaboration is continually evaluating the impact of radiation on the Pixel Detector. In this talk the key status and performance metrics of the ATLAS Pixel Detector are summarised at various levels of fluence and bias voltage values, putting focus on performance and operating conditions with special emphasis to radiation damage and mitigation techniques adopted, with prediction of their evolution until the end of LHC Run3 in 2026. These results provide useful indications for the optimisation of the operating conditions for the new generation of pixel trackers under construction for HL-LHC upgrades