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More than 40 years since its discovery, the Z boson remains a cornerstone of particle physics research. Through its production alongside heavy-flavour quarks (bottom and charm quarks), the Z boson provides a unique window into the internal dynamics of a proton’s constituents. Specifically, it allows researchers to probe the heavy-flavour contributions to “Parton Distribution Functions” (PDFs), which describe how a proton’s momentum is distributed among its constituent quarks and gluons. Using the full LHC Run-2 dataset, the ATLAS Collaboration measured Z boson production in association with both bottom (b) and charm © quarks, the latter for the first time in ATLAS. In their new result, physicists studied Z boson decays into electron or muon pairs produced in association with “jets” of particles. They focused on jets arising from the hadronisation of b or c quarks, creating two jet “flavours”: b-jets and c-jets. Physicists developed a new multivariate algorithm that was able to identify the jet-flavour, allowing them to measure the production of both Z+b-jets and Z+c-jets processes. Researchers then took this one step further and applied a specialised fit procedure, called the ‘flavour-fit’, to determine the large background contribution due to Z production together with other flavour jets. This method is driven by data and allows a precise description of the jet flavours for every studied observable. This led to a significant improvement in the precision of the results, allowing a more stringent comparison with theoretical predictions. The Z boson provides a unique window into the internal dynamics of a proton’s constituents. So, what did they find? ATLAS researchers measured the production rates (or “cross sections”) of several physics observables. These results were then compared with theoretical predictions, probing various approaches to describe the quark distributions in protons, the most recent computational improvements in QCD calculations and the effect of different treatments of the quark masses in the predictions. For example, Figure 1a shows the differential cross section for Z+1 b-jet production as a function of the transverse momentum of the most energetic b-jet in the event. Results show that predictions treating the b-quarks as massless (blue squares and red triangles) provide the best agreement with measurements. Z+2 b-jets angular observables are in general well understood, while some discrepancies with data appear in the invariant mass of the 2 b-jets, whose spectrum is not well modelled by the studied predictions. Figure 1: Measured fiducial cross-section as a function of a) leading b-jet pT for Z+b-jets events and b) leading c-jet x_F (its momentum along the beam axis relative to the initial proton momentum) for Z+c-jets events. Data (black) are compared with several theoretical predictions testing different theoretical flavour schemes, high order accuracy calculations and intrinsic charm models. (Image: ATLAS Collaboration/CERN) Studying Z+c-jets production offered a unique possibility to investigate the hypothesis of intrinsic (valence-like) components of c-quarks in the proton. With this result, the ATLAS Collaboration contributes to the long-standing debate on the existence of this phenomenon, currently supported by experimental measurements from the LHCb Collaboration. As shown in Figure 1b, the Z+c-jets results were compared with several hypotheses for intrinsic charm content. Due to the larger experimental and theoretical uncertainty on Z+c-jets processes, the current result makes no strong statement on the intrinsic c-quark component in the proton. However, it does improve physicists’ sensitivity to this effect, as the new data will be used in future by PDF fitting groups to set tighter constraints on the intrinsic charm distribution in the proton. Overall, the new ATLAS result provides deep insights for refining theoretical predictions, thereby fostering a deeper understanding of the dynamics of heavy-flavour quark content in the proton. About the event display: Display of a candidate Z boson decaying to two muons alongside two b-jets, recorded by the ATLAS detector at a centre-of-mass collision energy of 13 TeV. Blue cones indicate the b-jets, and the red lines indicate the muon tracks. Starting from the centre of the ATLAS detector, the reconstructed tracks of the charged particles in the inner detector are shown as cyan lines. The energy deposits in the electromagnetic (the green layer) and hadronic (the red layer) calorimeters are shown as yellow boxes. The hits in the muon spectrometer (the outer blue layer) are shown as light blue blocks. (Image: ATLAS Collaboration/CERN) Learn more Measurements of the production cross-section for a Z boson in association with b-or c-jets in proton-proton collisions at 13 TeV with the ATLAS detector (arXiv:2403.15093, see figures) Measurements of the production cross-section for a boson in association with in proton–proton collisions at 13 TeV (JHEP 7 (2020) 44, arXiv:2003.11960) LHCb Collaboration, Study of Z Bosons Produced in Association with Charm in the Forward Region (Phys. Rev. Lett. 128 (2022) 82,001, arXiv:2109.08084) See also the full list of ATLAS physics results.

The company is rumored to launch 50-Series RTX GPUs earlier than expected.

An international research team led by the University of Göttingen has demonstrated experimentally that electrons in naturally occurring double-layer graphene move like particles without any mass, in the same way that light travels.

Furthermore, they have shown that the current can be “switched” on and off, which has potential for developing tiny, energy-efficient transistors – like the light switch in your house but at a nanoscale.

The Massachusetts Institute of Technology (MIT), USA, and the National Institute for Materials Science (NIMS), Japan, were also involved in the research. The results were published in Nature Communications (“Probing the tunable multi-cone band structure in Bernal bilayer graphene”).

Silicon-based electronics are approaching their physical limitations and new materials are needed to keep up with current technological demands. Two-dimensional (2D) materials have a rich array of properties, including superconductivity and magnetism, and are promising candidates for use in electronic systems, such as transistors. However, precisely controlling the properties of these materials is extraordinarily difficult.

There’s a reason airlines won’t let you put your laptop in your checked luggage; the lithium-ion battery poses a serious fire hazard. But why? Lithium is incredibly reactive.

For instance, pure lithium violently interacts with seemingly innocuous water, releasing heat and forming highly flammable hydrogen. This reactivity, however, is exactly why lithium makes a great material for batteries, and why it is a critical mineral for the green energy transition.

Lithium-ion batteries are widely used in electric vehicles. Plus, they can store energy produced by renewable resources like solar and wind.

Intrinsically stretchable quantum dot light-emitting diodes. Credit: Institute for Basic Science.

Intrinsically stretchable quantum dot-based light-emitting diodes achieved record-breaking performance.

A team of South Korean scientists led by Professor KIM Dae-Hyeong of the Center for Nanoparticle Research within the Institute for Basic Science has pioneered a novel approach to stretchable displays. The team announced the first development of intrinsically stretchable quantum dot light-emitting diodes (QLEDs).

Rice University physicists have discovered a phase-changing quantum material — and a method for finding more like it — that could potentially be used to create flash-like memory capable of storing quantum bits of information, or qubits, even when a quantum computer is powered down.

Phase-Changing Materials and Digital Memory

Phase-changing materials have been used in commercially available non-volatile digital memory. In rewritable DVDs, for example, a laser is used to heat minute bits of material that cools to form either crystals or amorphous clumps. Two phases of the material, which have very different optical properties, are used to store the ones and zeros of digital bits of information.

Microsoft on Tuesday launched a native OneNote app for visionOS, showing the company’s commitment to its customers who use Apple Vision Pro. This comes after the company released Microsoft Office apps for Apple’s mixed reality headset.

A Product Manager from the company confirmed the news in a blog post. According to Microsoft, “OneNote will make use of the infinite canvas of spatial computing and can appear side-by-side with other great Microsoft apps” already available for Apple Vision Pro. For those unfamiliar, OneNote is Microsoft’s note-taking software.

Microsoft says that the visionOS version has “many of the features available on OneNote for iPad.” This includes the ability to write notes, make a digital notebook, highlight important notes, create To Do tags, lock notes with a password, synchronize with OneDrive, and share with other people.

An international research team led by the University of Göttingen has demonstrated experimentally that electrons in naturally occurring double-layer graphene move like particles without any mass, in the same way that light travels. Furthermore, they have shown that the current can be “switched” on and off, which has potential for developing tiny, energy-efficient transistors—like the light switch in your house but at a nanoscale.