Is Dark Matter Hiding in Plain Sight?

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The ATLAS Collaboration originated the look for semi-visible jets, a possible dark matter signature occurring from dark quarks and gluons in a highly connecting dark sector. Despite the obstacles and no direct findings, this unique research study sets the very first limitations on semi-visible jet production, leading the way for more nuanced dark matter searches in the future.

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”).

Semi Visible Jet Event Display

The ATLAS Collaboration has actually performed the very first look for semi-visible jets, a possible signature for the existence of dark matter particles. These are assumed to take place when 2 protons connect, creating an intermediate particle that then changes into 2 jets. Credit: ATLAS Collaboration/ CERN

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.

ATLAS Physics Dark Matter Hiding in Plain Sight

Figure 1: The information, background and 6 forecasted signal circulations covering a representative conciliator mass and unnoticeable portion variety are overlaid for the azimuthal angular distinction in between the 2 semi-visible jets prospects. Excellent contract in between information and background is observed. Credit: ATLAS Collaboration/ CERN

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.

Expected and Observed Exclusion Contours for Semi-Visible Jets Signal

Figure 2: The anticipated and observed exemption shapes for semi-visible jets signal as a function of conciliator mass on the x-axis, and the unnoticeable portion on the y-axis. Mediator masses on the left-hand side of the red strong line are omitted for the offered unnoticeable portion. Credit: ATLAS Collaboration/ CERN

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.