Month: July 2020

Enlarge / World Health Organization (WHO) Chief Scientist Soumya Swaminathan attends a press conference organized by the Geneva Association of United Nations Correspondents (ACANU) amid the COVID-19 outbreak, caused by the novel coronavirus, on July 3, 2020 at the WHO headquarters in Geneva. (credit: Getty | Fabrice Coffrini)

If you happened to read The New York Times this week, you may be under the false impression that the World Health Organization significantly changed its stance on whether the pandemic coronavirus, SARS-CoV-2, spreads by lingering in the air.

Around midday Thursday, the paper declared: “W.H.O., in Reversal, Affirms Virus May Be Airborne Indoors.” The paper also called it an “admission” and, in a subsequent article, said the WHO had “conceded.” The articles both noted that a group of more than 200 researchers had also published a commentary piece this week urging the WHO and other public health bodies to acknowledge and address the potential for airborne transmission of SARS-CoV-2.

The problem: the WHO did not change its stance on airborne transmission. And, as such, it did not issue any new recommendations or guidance on how people can stay safe.

Enlarge / Particle tracks from the LHCb detector. (credit: Brookhaven National Lab)

The quark model was an intellectual revolution for physics. Physicists were faced with an ever-growing zoo of unstable particles that didn't seem to have a role in the Universe around us. Quarks explained all that through an (at least superficially) simple set of rules that built all of these particles through combinations of two or three quarks.

While that general outline seems simple, the rules by which particles called "gluons" hold the quarks together in particles are fiendishly complex, and we don't always know their limits. Are there reasons that particles seem to stop at collections of three quarks?

With the advent of ever-more powerful particle colliders, we've found some indications that the answer is "no." Reports of four-quark and even five-quark particles have appeared in different experiments. But questions remain about the nature of the interactions in these particles. Now, CERN has announced a new addition to growing family of tetraquarks, a collection two charm quarks and two anti-charm quarks.