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1. Detailed report on the measurement of the positive muon anomalous magnetic moment to 0.20 ppm

   https://doi.org/10.1103/PhysRevD.110.032009  

   Aguillard, D P; Albahri, T; Allspach, D; Anisenkov, A; Badgley, K; Baeßler, S; Bailey, I; Bailey, L; Baranov, V A; Barlas-Yucel, E; et al (August 2024, Physical Review D)

   We present details on a new measurement of the muon magnetic anomaly, $a_{\mu }=(g_{\mu }-2)/2$. The result is based on positive muon data taken at Fermilab’s Muon Campus during the 2019 and 2020 accelerator runs. The measurement uses $3.1\mathrm{GeV}/c$polarized muons stored in a 7.1-m-radius storage ring with a 1.45 T uniform magnetic field. The value of $a_{\mu }$is determined from the measured difference between the muon spin precession frequency and its cyclotron frequency. This difference is normalized to the strength of the magnetic field, measured using nuclear magnetic resonance. The ratio is then corrected for small contributions from beam motion, beam dispersion, and transient magnetic fields. We measure $a_{\mu }=116592057\left(25\right)\times {10}^{-11}$(0.21 ppm). This is the world’s most precise measurement of this quantity and represents a factor of 2.2 improvement over our previous result based on the 2018 dataset. In combination, the two datasets yield $a_{\mu }\left(\mathrm{FNAL}\right)=116592055\left(24\right)\times {10}^{-11}$(0.20 ppm). Combining this with the measurements from Brookhaven National Laboratory for both positive and negative muons, the new world average is $a_{\mu }\left(\exp \right)=116592059\left(22\right)\times {10}^{-11}$(0.19 ppm). Published by the American Physical Society2024 

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2. Mulan: a part-per-million measurement of the muon lifetime and determination of the Fermi constant

   https://doi.org/10.21468/SciPostPhysProc.5.016  

   Carey, Rebecca; Gorringe, Tim; Hertzog, David (January 2021, SciPost Physics Proceedings)

   The part-per-million measurement of the positive muon lifetime anddetermination of the Fermi constant by the MuLan experiment at the PaulScherrer Institute is reviewed. The experiment used an innovative,time-structured, surface muon beam and anear-4 \pi π ,finely-segmented, plastic scintillator positron detector. Two in-vacuummuon stopping targets were used: a ferromagnetic foil with a largeinternal magnetic field, and a quartz crystal in a moderate externalmagnetic field. The experiment acquired a dataset of 1.6 \times 10^{12} 1.6 × 10 12 positive muon decays and obtained a muon lifetime \tau_{\mu} = 2\, 196\, 980.3(2.2) τ μ = 2 196 980.3 ( 2.2 ) ~ps(1.0~ppm) and Fermi constant G _F = 1.166\, 378\, 7(6) \times 10^{-5} F = 1.166 378 7 ( 6 ) × 10 − 5 GeV ^{-2} − 2 (0.5~ppm). The thirty-fold improvement in \tau_{\mu} τ μ has proven valuable for precision measurements in nuclear muon captureand the commensurate improvement in G _F F has proven valuable for precision tests of the standard model. 

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3. Measurement of the effective leptonic weak mixing angle

   https://doi.org/10.1007/JHEP12(2024)026  

   Aaij, R; Abdelmotteleb, A_S W; Abellan_Beteta, C; Abudinén, F; Ackernley, T; Adefisoye, A A; Adeva, B; Adinolfi, M; Adlarson, P; Agapopoulou, C; et al (December 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> Usingppcollision data at$$ \sqrt{s} $$ $\sqrt{s}$= 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb⁻¹, the forward-backward asymmetry in thepp→Z/γ^*→μ⁺μ⁻process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is$$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023, $$ ${sin}^2{\theta }_{\mathrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023,$ where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract$$ {\sin}^2{\theta}_{\textrm{eff}}^{\ell } $$ ${sin}^2{\theta }_{\mathrm{eff}}^{\ell }$from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit. 

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4. The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3

   https://doi.org/10.1088/1748-0221/19/05/P05063  

   Aad, G; Abbott, B; Abbott, DC; Abdallah, J; Abeling, K; Abidi, SH; Aboulhorma, A; Abovyan, S; Abramowicz, H; Abreu, H; et al (May 2024, Journal of Instrumentation)

   Abstract The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector. 

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5. A measurement of the K+ → π+μ+μ− decay

   https://doi.org/10.1007/JHEP11(2022)011  

   Cortina Gil, E.; Kleimenova, A.; Minucci, E.; Padolski, S.; Petrov, P.; Shaikhiev, A.; Volpe, R.; Numao, T.; Petrov, Y.; Velghe, B.; et al (November 2022, Journal of High Energy Physics)

   A bstract A sample of 2 . 8 × 10 4 K + → π + μ + μ − candidates with negligible background was collected by the NA62 experiment at the CERN SPS in 2017–2018. The model-independent branching fraction is measured to be (9 . 15 ± 0 . 08) × 10 − 8 , a factor three more precise than previous measurements. The decay form factor is presented as a function of the squared dimuon mass. A measurement of the form factor parameters and their uncertainties is performed using a description based on Chiral Perturbation Theory at $$ \mathcal{O} $$ O ( p 6 ). 

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