What takes place if dark-matter particles are produced inside a jet of Standard-Model particles? This causes an unique detector signature called semi-visible jets! The ATLAS Collaboration has actually created the very first look for semi-visible jets, trying to find them in a basic production mode where 2 protons connect by exchanging an intermediate particle, which is then transformed into 2 jets.
The evasive nature of dark matter stays among the greatest secrets in particle physics. Most of the searches have up until now tried to find occasions where a “weakly interacting” dark-matter particle is produced together with an understood Standard-Model particle. Since the dark-matter particle can not be seen by the ATLAS detector, scientists search for an imbalance of transverse momentum (or “missing energy”).
However, some theoretical designs anticipate a “strongly interacting” dark sector, with dark quarks and gluons as reproductions of Standard-Model quarks and gluons. Semi- noticeable jets would develop when dark quarks decay partly to Standard-Model quarks and partly to steady dark hadrons (the “invisible fraction”). Since they are produced in sets, usually in addition to extra Standard-Model jets, the missing out on energy emerges when all the jets are not totally stabilized. The instructions of the missing out on energy is frequently lined up with among the semi-visible jets, as can be seen in case screen above.
This makes look for semi-visible jets really tough, as this occasion signature can likewise develop due to mis-measured jets in the detector. For their brand-new search, physicists needed to make certain all such impacts had actually been represented. To do this, they concentrated on a couple of observables: the originality of the positioning and magnitude of transverse momentum, and the angle in between the semi-visible jets. They likewise examined circumstances with various unnoticeable portions and moderating particle masses.
After accounting for all the Standard-Model processes adding to this occasion geography, scientists discovered no tip of semi-visible jets. As can be seen from Figure 1, which reveals the angular distinction in between the 2 semi-visible jet prospects, the information follows the Standard-Model background shape. Dark- matter signals were anticipated to have a somewhat various shape.
The look for semi-visible jets really tough, as its occasion signature can likewise develop due to mis-measured jets in the detector. How did ATLAS scientists conquer this difficulty?
This unique outcome sets the very first limitations on this particular semi-visible-jet production situation, displayed in Figure 2 as functions of both the conciliator mass and the unnoticeable portion. The search is more delicate at intermediate worths of the unnoticeable portion, and omits conciliator masses as much as 2.7 TeV. Researchers were likewise able to report the variety of information occasions observed representing the occasion choice requirements. This sets essential foundation for future look for dark matter, allowing physicists to develop semi-visible-jet designs that take into consideration the existing restrictions on this signature.
There’s still a lot delegated check out! ATLAS scientists prepare to methodically study all possible signatures from the strong dark sector landscape, which might consist of exposed signatures like the one thought about in this search. As the ATLAS experiment continues to grow its massive dataset, it will supply brand-new chances for expedition and brand-new choices to extend the look for semi-visible jets.