[BroJoeK]

from the article: "A team of US researchers has detected a new form of elementary particle called the 'four-flavoured' tetraquark that can affect scientists' understanding of 'quark matter' "

Affect? Or effect?

"Affect" implies a negative change, i.e.: cold weather affects my health.
"Affect" can also imply a moving emotional experience, i.e.: that music affects me deeply.
Neither seems to apply here.

"Effect" is a simple, straight-forward change, i.e.: "tetraquarks can effect scientists understanding of 'quark matter' ".

But "effect" is hardly the best choice of words.
Other words like, "change", "modify" or "increase" are clearer, less nebulous.

[Quality_Not_Quantity]

"Affect" implies a negative change

That is not correct.

Affect (v) 1: have an effect on; make a difference to:

[LoneRangerMassachusetts]

Affect vs. effect - Grammarist

grammarist.com/usage/affect-effect/

Affect is usually a verb, and effect is usually a noun. To affect something is to change or influence it, and an effect is something that happens due to a cause.

The author's use is correct.