The linker molecule LAT is a critical substrate of the tyrosine kinases activated upon TCR engagement. Phosphorylated LAT binds Grb2, PLC-gamma1, and other signaling molecules. We demonstrate that human LAT is palmitoylated and that palmitoylated LAT predominantly localizes into glycolipid-enriched microdomains (GEMs). Although the LAT transmembrane domain is sufficient for membrane localization, palmitoylation at C26 and C29 is essential for efficient partitioning into GEMs. LAT palmitoylation is necessary for its tyrosine phosphorylation. After T cell activation, most tyrosine-phosphorylated LAT molecules and a fraction of PLC-gamma1 and other signaling molecules are present in GEMs. LAT is central to T cell activation and is a novel linker molecule shown to require targeting to membrane microdomains for signaling.
Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50° above and below the Galactic center (GC), with a width of about 40° in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE ∼ E−2) than the inverse Compton emission from electrons in the Galactic disk, or the gamma rays produced by the decay of pions from proton–interstellar medium collisions. There is no significant spatial variation in the spectrum or gamma-ray intensity within the bubbles, or between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; the edges of the bubbles also line up with features in the ROSAT X-ray maps at 1.5–2 keV. We argue that these Galactic gamma-ray bubbles were most likely created by some large episode of energy injection in the GC, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last ∼10 Myr. Dark matter annihilation/decay seems unlikely to generate all the features of the bubbles and the associated signals in WMAP and ROSAT; the bubbles must be understood in order to use measurements of the diffuse gamma-ray emission in the inner Galaxy as a probe of dark matter physics. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population.
Alessandro Conigli, Dalibor Djukanovic, Georg von Hippel
et al.
We present an update of our lattice QCD determination of the hadronic contribution to the running of the electromagnetic coupling, $Δα_{\mathrm{had}}^{(5)}(-Q^2)$, and of the electroweak mixing angle in the space-like momentum region up to $Q^2=12\ \mathrm{GeV}^2$. The calculation is based on CLS ensembles with $N_f=2+1$ flavours of $O(a)$-improved Wilson fermions, covering five lattice spacings between $0.039$ and $0.085$ fm and a range of pion masses, including the physical point. A refined analysis employing a telescopic window strategy allows for a clean separation of systematic effects across Euclidean distance scales. Statistical precision is further enhanced through low-mode averaging, combined with a spectral reconstruction of the vector-vector correlator at long distances on the most chiral ensembles. We confirm significant tensions of up to $7σ$ at space-like virtualities around $Q^2= 1\ \mathrm{GeV}^2$ between our lattice results for $Δα_{\mathrm{had}}^{(5)}(-Q^2)$ and the corresponding data-driven estimates based on $e^+e^-$ cross section data. Combining our lattice data with perturbative QCD via the Euclidean split technique, we obtain at the $Z$-pole $Δα_{\mathrm{had}}^{(5)}(M_Z^2) = 0.027813(33)_{\mathrm{lat}}(35)_{\mathrm{pQCD}}$, which is more than two times more precise than recent data-driven estimates. Our result deviates slightly, by $1-2σ$, from the value produced by global electroweak fits. For the electroweak mixing angle, we present the hadronic contribution to its running and provide a precise determination of the octet-singlet mixing component $\barΠ^{(0,8)}$, in good agreement with phenomenological models but with significantly higher precision.
Jason Aebischer, Atakan Tugberk Akmete, Riccardo Aliberti
et al.
The kaon physics programme, long heralded as a cutting-edge frontier by the European Strategy for Particle Physics, continues to stand at the intersection of discovery and innovation in high-energy physics (HEP). With its unparalleled capacity to explore new physics at the multi-TeV scale, kaon research is poised to unveil phenomena that could reshape our understanding of the Universe. This document highlights the compelling physics case, with emphasis on exciting new opportunities for advancing kaon physics not only in Europe but also on a global stage. As an important player in the future of HEP, the kaon programme promises to drive transformative breakthroughs, inviting exploration at the forefront of scientific discovery.
The parametric error on the QCD-coupling can be a dominant source of uncertainty in several important observables. One way to extract the coupling is to compare high order perturbative computations with lattice evaluated moments of heavy quark two-point functions. The truncation of the perturbative series is a sizable systematic uncertainty that needs to be under control. In this contribution we give an update on our study arXiv:hep-lat/2203.07936v1 on this issue. We measure pseudo-scalar two-point functions in volumes of $L=2$ fm with twisted-mass Wilson fermions in the quenched approximation. We use full twist, the non-perturbative clover term and lattice spacings down to $a=0.010$ fm to tame the large discretization effects. Our results show that both the continuum extrapolations and the extrapolation of the $Λ$-parameter to the asymptotic perturbative region are very challenging.
V. Daniel Elvira, Steven Gottlieb, Oliver Gutsche
et al.
Software and Computing (S&C) are essential to all High Energy Physics (HEP) experiments and many theoretical studies. The size and complexity of S&C are now commensurate with that of experimental instruments, playing a critical role in experimental design, data acquisition/instrumental control, reconstruction, and analysis. Furthermore, S&C often plays a leading role in driving the precision of theoretical calculations and simulations. Within this central role in HEP, S&C has been immensely successful over the last decade. This report looks forward to the next decade and beyond, in the context of the 2021 Particle Physics Community Planning Exercise ("Snowmass") organized by the Division of Particles and Fields (DPF) of the American Physical Society.