2019-06-01_All_About_Space

have for some time considered the axion as a
possible source of dark matter and an identity for
the ‘inf laton’. An axif lavon could work equally well
to solve both problems.
Another problem that the axif lavon might solve
is the deeper nature of the Higgs boson itself. “In
an article  published in July, Tommi Alanne, Simone
Blasi and I studied whether the axif lavon scalar
could be part ofabiggerscalarmultiplet–thatis,
a 'larger' unified field containing further particles –
that also includes the Higgs field, the source of
elementary-particle masses,” Goertz explains.
In other words, it seems that it’s possible that
the Higgs and the axif lavon can themselves be
unified into a particle that exhibits the properties of
both axion, flavon and Higgs in different situations.
Although the work done so far does not offer a
direct explanation for the unexpectedly low mass of
the Higgs found in real-world experiments, further
research could offer new insights into this puzzle.
Unsurprisingly, physicists are finding the idea of
the axif lavon immensely alluring – not only does
it solve some major outstanding problems, but a
single particle manifesting appeals to hopes for
a fundamental simplicity in nature, rather than
muddying the waters with countless hypothetical
particles and fields to do different jobs.
Aside from this,asGoertzhintsabove,thetheory
is predictive – if it’s correct it says certain things
about the way subatomic particles behave that can
be tested using current technology.

”[Because] the axion now inherits properties

fromtheflavon,it’spossibletosearchforitusing

flavour experiments,” Goertz continues. “In fact,

oneofthebesthopestofindtheaxiflavonisthe

existing NA62 experiment at CERN [the European

Organisation for Nuclear Research on the Swiss/

French border].”

NA62isoneofCERN’slessglamorous

experiments, and even its name is simply code for

North Area 62. While the huge cavern-filling

detectors of the 27-kilometre- (16.7-mile) long Large

HadronColliderringgetmostoftheattention,the

complex also incorporates a seven-kilometre (four-

mile)ringonitsnorthernsidecalledtheSuper

Proton Synchrotron (SPS). This smaller particle

accelerator generates collisions using a powerful

beam of positively charged protons and other

particles travelling at close to the speed of light,

andNA62isusingthisbeamtostudythedecayof

quark/antiquark pairs called kaons – an antiquark

is an ‘antimatter’ quark with the opposite electric

charge to its ‘normal’ counterpart. After several

yearsoftrialstheexperimentbeganatwo-yearrun

tocollectdatainearnestin2016.

“NA62issearchingforthedecayofakaontoa

pion and 'invisible' particles leaving the detector,”

explains Goertz. “In the Standard Model of particle

physics these particles are the neutrinos. However,

iftheaxiflavonexistsitwouldleadtoasimilar

signal, and thus be detected as an enhancement in

the data.”

NA62’s observations of these rare decay events

–sorarethattheexperimentispredictedtoonly

observe80ineachtwo-yearrun–couldatleast

hint at the axiflavon’s existence, as could the

Belle II experiment at the SuperKEKB accelerator

in Japan. But, with the new model adding Higgs

unification to the mix, Goertz hopes to be even

more conclusive: “The possible unification with the

Higgs [makes] the model even more predictive, such

that at the NA62 experiment we could basically

fully disprove it, if it exists.”

If Goertz and his colleagues are right then the

next couple of years could see a new discovery to

rival the Higgs boson itself, and finally wrap up

some of our biggest remaining mysteries about the

universe. But, sadly, for the moment we shall just

have to wait!

“It seemspossiblethattheHiggsandtheaxiflavonthemselves

can beunifiedintoaparticlethatexhibitsthepropertiesof

both axion, flavon and Higgs in different situations”

Beryllium target

Theprotonsstrikeaberyllium

target, triggering reactions to

produceabeamofonebillion

particles per second.

CEDAR

Onlyaboutsixpercentofthe

particles produced are kaons, a

combinationofastrangequark

with an anti-up or anti-down

quark. The CEDAR detector uses

characteristic radiation from the

kaonstoidentifythem.

GigaTracker

Three highly sensitive

cameras track the precise

paths of the incoming kaons.

Decay region

Astheypassacrossa65-metre(213-foot)

vacuumahandfulofunstablekaonswill

naturallydecayintoanothertypeofparticle

called a pion, releasing a neutrino and

antineutrinointheprocess.Thisisthemain

processthatNA62isdesignedtostudy.

Decay product detectors

Aseriesof‘downstream’

instruments analyse the particles

generated by the kaon decay. If the

axiflavonexiststhenitcouldgive

a boost to the expected signature

fromneutrinoparticles.

The NA62 experiment

© NRAO; CERN

The rotation

rate of

galaxies,

such as near

neighbour

Messier 33

shown here,

indicates

they contain

huge

amounts

of unseen

dark matter

Proton beam

Trillions of high-energy protons

enter the experiment through a

straighttunnel–theexperimentis

270metres(886feet)longintotal.

Solving the universe