Month: August 2021

Enlarge / An artist’s impression of Tcc+, a tetraquark composed of two charm quarks and an up and a down antiquark. (credit: CERN)

The exotic family of particles known as tetraquarks has a surprising new member. Dubbed T_cc⁺, it's the first tetraquark to contain two heavy quarks and two light antiquarks, and it's the longest-lived exotic matter particle yet discovered. Representatives for the LHCb collaboration at CERN's Large Hadron Collider made the announcement last week at the European Physical Society Conference on High Energy Physics in Germany, hosted jointly by Universität Hamburg and DESY.

Quarks are the most fundamental building blocks of matter, first proposed in 1964 by Murray Gell-Mann and George Zweig. Quarks come in six different flavors, all differing in mass and charge: up, down, strange, charm, bottom, and top (from lightest to the heaviest), along with their corresponding antiquarks. They typically clump together in groups of two or three to form hadrons, held together by force-carrying particles known as gluons. Ordinary baryons are hadrons that include the proton and neutron of an atom, each made up of three-quark combinations, while hadronic particles known as mesons are formed from quark-antiquark pairs. Think of quarks as the LEGO bricks of the subatomic world, mixing and matching in various combinations to form more complicated structures.

Gell-Mann thought there might be more exotic hadrons formed from quark combinations of four or even five quarks, but these existed solely in the realm of theory until quite recently. That's because such exotic heavy particles decay very rapidly into more stable byproduct particles within fractions of a second. It's those byproducts that show up in particle accelerator detectors, amounting to distinctive signatures for their heavier precursor particles. But it's extremely difficult to tease out those signatures from all the noise in the vast amounts of data produced in particle collisions.

Enlarge (credit: Getty Images | Yuichiro Chino)

Apple today said it will refuse any government demands to expand its new photo-scanning technology beyond the current plan of using it only to detect CSAM (child sexual abuse material).

Apple has faced days of criticism from security experts, privacy advocates, and privacy-minded users over the plan it announced Thursday, in which iPhones and other Apple devices will scan photos before they are uploaded to iCloud. Many critics pointed out that once the technology is on consumer devices, it won't be difficult for Apple to expand it beyond the detection of CSAM in response to government demands for broader surveillance. We covered how the program will work in detail in an article Thursday night.

Governments have been pressuring Apple to install backdoors into its end-to-end encryption system for years, and Apple acknowledged that governments are likely to make the exact demands that security experts and privacy advocates have been warning about. In a FAQ released today with the title, "Expanded Protections for Children," there is a question that asks, "Could governments force Apple to add non-CSAM images to the hash list?"

Enlarge / Cover art of the new report. (credit: IPCC)

It has been eight years since the last major report from the Intergovernmental Panel on Climate Change (IPCC), though it has produced smaller reports since then. But today, the first piece of the 6^th Assessment Report is out. Most of it should not surprise you—the basics of climate science have been known for decades. And the general outlines were already obvious: almost all of the warming is due to human activities, and, without immediate action, we're poised to blow past 1.5º C of warming.

Still, each report is a little more useful than the last, and we're going to go over what has changed in terms of the science and what has changed in how that information is being shared with the public.

The IPCC is the product of a United Nations organization that coordinates—but does not write—these reports. The writing is done by scientists from around the world who volunteer their time to create these daunting tomes that seek to summarize the entire state of scientific knowledge for all kinds of decision-makers. Each major report is split into three working groups. The first focuses on the physical science of the climate system, the second on the impacts of climate change on humans and other species, and the third on methods for mitigating climate change.