Belle II Detector
Science & Technology

New Insights Into Dark Matter: Belle II Yields First Results in Search of the Z’ Boson

Electrons and positrons collide inside the Belle II detector. Credit score: in poor health./©: Belle II

The Belle II experiment began about one yr in the past. Bodily Assessment Letters has now revealed the preliminary outcomes of the detector. The work offers with a brand new particle in the context of darkish matter, which accounts for about 25 p.c of the universe.

The Belle II experiment has been gathering information from bodily measurements for about one yr now. After a number of years of rebuilding work, each the SuperKEKB electron-positron accelerator and the Belle II detector have been improved in contrast with their predecessors in order to realize a 40-fold greater information price. Scientists at 12 German analysis establishments are concerned in establishing and working the detector, creating analysis algorithms, and analyzing the information. Johannes Gutenberg College Mainz (JGU) supported this undertaking by creating and programming particular electronics for monitoring the pixel vertex detector.

With the assist of Belle II, scientists are in search of traces of new physics that can be utilized to clarify the unequal incidence of matter and anti-matter and the mysterious darkish matter. One of the to date undiscovered particles that the Belle II detector is in search of is the Z’ boson – a variant of the Z boson, which acts as an trade particle for the weak interplay.

The Belle II detector searches for the Z’ boson. This particle might reveal itself by an sudden excessive quantity of muon pairs with reverse fees, as proven right here. Credit score: in poor health./©: Belle II

So far as we all know, about 25 p.c of the universe consists of darkish matter, whereas seen matter accounts for just below 5 p.c of the vitality funds. Each kinds of matter appeal to one another via gravity. Dark matter thus kinds a sort of template for the distribution of seen matter. This may be seen, for instance, in the association of galaxies in the universe.

The Z’ boson might play an attention-grabbing function in the interplay between darkish and visual matter, it could possibly be in reality a sort of mediator between the two kinds of matter). The Z’ boson can – not less than theoretically – end result from the collision of electrons (matter) and positrons (anti-matter) in the SuperKEKB after which decay into invisible darkish matter particles.

The Z’ boson can thus assist scientists to know the conduct of darkish matter. What’s extra, the discovery of the Z’ boson might additionally clarify different observations that aren’t in step with the Normal Mannequin, the elementary principle of particle physics.

However how can the Z’ boson be detected in the Belle II detector? In a roundabout way – that a lot is certain. Theoretical fashions and simulations predict that the Z’ boson might reveal itself via interactions with muons, the heavier kin of electrons. If scientists uncover an unusually excessive quantity of muon pairs of reverse cost after the electron/positron collisions in addition to sudden deviations in vitality and momentum conservation, this could be an necessary indication of the Z’ boson. Nevertheless, the new Belle II information has not but offered any indication of the Z’ boson. However with the new information, the scientists can restrict the mass and coupling strengths of the Z’ boson with beforehand unattainable accuracy.

These preliminary outcomes come from the evaluation of a small quantity of information collected throughout the start-up part of SuperKEKB in 2018. Belle II went into full operation on March 25, 2019. Since then, the experiment has been gathering information whereas constantly bettering the collision price of electrons and positrons. As soon as the experiment is completely tuned, it should present significantly extra information than in the just lately revealed analyses. The physicists thus hope to realize new insights into the nature of darkish matter and different unanswered questions.

Reference: “Search for an Invisibly Decaying Z Boson at Belle II in e+eμ+μ(e±μ) Plus Lacking Vitality Remaining States” by I. Adachi et al. (Belle II Collaboration), 6 April 2020, Bodily Assessment Letters.
DOI: 10.1103/PhysRevLett.124.141801

The German working teams in the Belle II experiment are funded by the following establishments and applications:

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