Page 20 - BBC Focus - August 2017
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DISCOVERIES
The new baryon particle
contains two charm quarks
and an up quark
PH Y S I C S
NEW SUBATOMIC PARTICLE
DISCOVERED AT CERN
What a charmer: scientists working at the Large been seen with two heavy quarks – in this case
Hadron Collider have found a new kind of two charm quarks.
subatomic particle. The particle is a baryon (a “FINDING A “The properties of the newly discovered Xi-
particle consisting of three quarks) named Xi-cc++, cc++ baryon shed light on a longstanding puzzle
and is part of a family of ‘doubly charmed baryons’ NEW HEAVY- surrounding the experimental status of baryons
whose existence had previously been predicted by containing two charm quarks, opening an
the Standard Model of particle physics, but never QUARK exciting new branch of investigation for LHCb,”
observed. The research, led by University of said Spradlin. The new baryon is around 3.5
Glasgow physicist Dr Patrick Spradlin, was carried BARYON IS times heavier than a proton or neutron, and has PHOTOS: ALAMY, NASA/HUBBLE SPACE TELESCOPE/STSC, GETTY, FLPA
out at the Large Hadron Collider’s LHCb detector. an electric charge twice that of a proton. The
All the matter we see around us is comprised of OF GREAT Glasgow team discovered over 300 Xi-cc++
protons and neutrons, which are baryons made of INTEREST” particles lurking in last year’s LHCb data.
the lighter up and down quarks. Baryons that “Finding a new heavy-quark baryon is of great
include the heavier charm, top, strange or beauty interest as it will provide a unique tool to further
quarks decay almost instantly into protons and probe quantum chromodynamics, the theory
neutrons, making them hard to detect. that describes the strong interaction, one of the PHOTOS: CERN, GETTY
Many baryons have been observed with one four fundamental forces,” said researcher
heavy quark but Xi-cc++ is the first one that’s ever Giovanni Passaleva.
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