BBC Earth (Asia) - - Update -

What a charmer: sci­en­tists work­ing at the Large Hadron Col­lider have found a new kind of subatomic par­ti­cle. The par­ti­cle is a baryon (a par­ti­cle con­sist­ing of three quarks) named Xi-cc++, and is part of a fam­ily of ‘dou­bly charmed baryons’ whose ex­is­tence had pre­vi­ously been pre­dicted by the Stan­dard Model of par­ti­cle physics, but never ob­served. The re­search, led by Univer­sity of Glas­gow physi­cist Dr Pa­trick Spradlin, was car­ried out at the Large Hadron Col­lider’s LHCb de­tec­tor.

All the mat­ter we see around us is com­prised of pro­tons and neu­trons, which are baryons made of the lighter up and down quarks. Baryons that in­clude the heav­ier charm, top, strange or beauty quarks de­cay al­most in­stantly into pro­tons and neu­trons, mak­ing them hard to de­tect.

Many baryons have been ob­served with one heavy quark but Xi-cc++ is the first one that’s ever been seen with two heavy quarks – in this case two charm quarks.

“The prop­er­ties of the newly dis­cov­ered Xi-cc++ baryon shed light on a long­stand­ing puz­zle sur­round­ing the ex­per­i­men­tal sta­tus of baryons con­tain­ing two charm quarks, opening an ex­cit­ing new branch of in­ves­ti­ga­tion for LHCb,” said Spradlin. The new baryon is around 3.5 times heav­ier than a pro­ton or neu­tron, and has an elec­tric charge twice that of a pro­ton. The

Glas­gow team dis­cov­ered over 300 Xi-cc++ par­ti­cles lurk­ing in last year’s LHCb data.

“Find­ing a new heavy-quark baryon is of great in­ter­est as it will pro­vide a unique tool to fur­ther probe quan­tum chro­mo­dy­nam­ics, the the­ory that de­scribes the strong in­ter­ac­tion, one of the four fun­da­men­tal forces,” said re­searcher

Gio­vanni Pas­sal­eva.


The new baryon par­ti­cle con­tains two charm quarks and an up quark

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