A shot of good news from Gaza; CERN’s big small find; and nature’s unexpected light show

First round of polio vaccination completed in Gaza; CERN measures ultra-rare kaon decay; and thunderclouds can produce gamma-ray bursts.

During the first round of UNRWA’s oral polio vaccination drive in Gaza. | Photo Credit: UNRWA

Gaza’s kids get oral polio vaccine

“A RARE positive story from Gaza: the first round of the polio vaccination campaign ended successfully,” posted Philippe Lazzarini, the Commissioner General of the UN Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) on his official X account on September 16. According to his post, UNRWA and partners vaccinated hundreds of thousands of children, reaching 90 per cent coverage. “Our next challenge is to provide children with their second dose at the end of September.” UNRWA’s report on this second round is awaited.

This oral polio vaccination campaign targeting children aged ≤10 years is in response to the identification of circulating vaccine-derived poliovirus type 2 in wastewater in Gaza and a single confirmed case of paralytic poliomyelitis in a young child.

Writing in the latest issue of The Lancet, three US public health specialists from George Washington University—Ronald Waldman, Robert Steinglass, and Phillip Nieburg—said: “Now that an operational platform is in place, we believe that the second round should include vaccination against measles, which has consistently been the deadliest vaccine-preventable disease in humanitarian emergencies.”

As with poliovirus, they said, past coverage with injectable measles vaccine has been high in Gaza but has been falling, and with the collapse of the healthcare system, many children are unlikely to have been vaccinated last year. “Treatment of complications of measles will be difficult, if not impossible. Due to the very rapid rate of transmission and the dangerous environment, vaccinating after an outbreak occurs might be too late—prevention is by far the best, if not the only, life-saving measure,” they added. “High population density, inadequate shelter, poor sanitation, and under-nutrition are all major risk factors for infection, severity, and death, and all are features of the deplorable conditions for those people living in Gaza. The imminent arrival of cooler temperatures adds to the urgency to vaccinate against this disease, which can cause the death of up to 15 per cent of those infected…. There is good reason that, for nearly 50 years, mass measles vaccination campaigns have become a standard early intervention in conflict... and other humanitarian settings; the risk of a measles outbreak and accompanying high mortality is just too great,” they wrote.

The NA62 experiment is roughly 270 m long and is housed in the TCC8 and ECN3 caverns in CERN’s North Area. | Photo Credit: M. Brice/CERN

CERN measures ultra-rare kaon decay

AT a seminar on September 24, the NA62 collaboration at the Geneva-based CERN presented the first experimental observation of the ultra-rare decay of the charged kaon into a charged pion and a chargeless neutrino-antineutrino pair (K⁺→ π⁺υῡ). This finding could open a new path to discover physics beyond the current understanding of how the building blocks of matter interact based on the Standard Model (SM).

The process K⁺→ π⁺υῡ is very sensitive to new physics beyond the SM description. The SM predicts that less than 1 in 10 billion kaons will decay this way. The NA62 experiment was designed and constructed specifically to measure this ultra-rare kaon decay.

Experiments, including NA62, have previously seen evidence of this process, but this is the first time it has been measured with a statistical significance of five standard deviations (or 5 sigma), crossing the threshold conventionally required to claim a discovery in particle physics.

Kaons are produced by a high-intensity proton beam from the CERN Super Proton Synchrotron colliding with a stationary target. This creates a beam of secondary particles with almost a billion particles per second flying into the NA62 detector, about 6 per cent of which are charged kaons. The detector identifies and measures precisely each kaon and its decay products, except neutrinos, the identification of which is deduced from the missing energy in the final state of the process.

The new result is based on the combination of data taken by the NA62 experiment in 2021-22 and a previously published result based on the 2016-18 dataset. The fraction of K+ that decayed via the channel K⁺→ π⁺υῡ was measured to be about 13.0 in 100 billion. With a relative precision of 25 per cent, this is the most precise measurement of the decay to date. The result is about 50 per cent higher than the SM prediction but is compatible with it given the overall uncertainty. But this could also be due to new particles that increase the likelihood of this decay. With data taking ongoing, NA62 is set to be able to test the possibility of new physics in this decay within the next few years.

An artist’s impression of NASA’s high-flying ER-2 airplane that carries instrumentation of the ALOFT mission to record gamma rays (coloured purple for illustration) from thunderclouds. | Photo Credit: NASA/ALOFT Team

More in a thundercloud than meets the eye

THERE is more to thunderclouds than rain and lightning. Along with visible light emissions, thunderclouds can produce intense bursts of gamma rays, the most energetic form of light, that last for millionths of a second. The clouds can also glow steadily with gamma rays for seconds to minutes at a time. New observations from NASA’s ER-2 research aircraft have now found a new kind of gamma-ray emission that is shorter in duration than the steady glows and longer than the microsecond bursts. Researchers have called it a flickering gamma-ray flash. The discovery fills the missing link in scientists’ understanding of thundercloud radiation and provides new insights into the mechanisms that produce lightning. This could lead to more accurate lightning risk estimates for people, aircraft, and spacecraft, according to NASA’s Goddard Space Flight Center (GSFC) release. The international research team, led by the University of Bergen, Norway, included researchers from NASA’s Marshall Space Flight Center, the GSFC, the U.S. Naval Research Laboratory, and universities in the US, Mexico, Colombia, and Europe. The findings were published in two papers in the October 2 issue of Nature.

The discovery was made while flying a battery of detectors aboard the ER-2 in a series of flights in July 2023. It flew a few kilometres above tropical thunderclouds in the Caribbean and Central America. The  payload was developed for the Airborne Lightning Observatory campaign called ALOFT. The researchers had hoped that the ALOFT instruments would observe fast radiation bursts known as terrestrial gamma-ray flashes (TGFs) that were first discovered in 1992. Despite their high intensity, few TGFs were spotted during previous aircraft-based studies. However, this time around they saw 130 TGFs. But the flickering gamma-ray flashes were a complete surprise, according to Nikolai Østgaard of the University of Bergen. The team found over 25 of these new flashes, each lasting 50-200 ms.

Scientists believe that the abundance of fast bursts and the discovery of intermediate-duration flashes could be among the most important thundercloud discoveries in a decade or more.