Representation of the particle showers created through cosmic rays colliding in Earth’s higher environment. Credit score: Simon Swordy (U. Chicago), NASA
Scientists have an issue with cosmic rays—they produce too many muons on the Earth’s floor. Cascades of muons are byproducts of high-energy cosmic rays as they collide with nuclei within the higher environment, and scientists see extra muons at Earth’s floor than usual physics fashions are expecting.
Explaining those extra muons has been a problem for a number of years. However now a workforce of researchers say they may be able to give an explanation for the excess through invoking “gluon condensation” within the first cascade collision. Their paintings has been printed in The Astrophysical Magazine.
Each 2nd, hundreds of thousands of high-energy cosmic rays touring at just about the velocity of sunshine bombard Earth’s higher environment, the place they collide with atomic nuclei, basically nitrogen, oxygen and argon. The nuclei explode into a bath of debris, basically pions, kaons and baryons. Those then decay into basically muons, the heavier replica of the electron. (About 90% of the muons come from decays of pions and kaons.)
Those muons undergo just a small calories loss as they continue in the course of the environment till they achieve the skin. (Their skill to achieve the skin, regardless of their lifetime being too quick to it seems that achieve this, is triumphally defined through particular relativity.) About one muon in keeping with square-centimeter reaches the Earth’s floor in keeping with minute, with a mean calories of four GeV however an overly wide calories spectrum.
But, in comparison to the result of usual physics fashions derived from particle accelerator experiments comparable to on the Massive Hadron Collider and the Tremendous Proton Synchrotron at CERN, too many muons are seen on the floor. For muon energies between 6 and 16 exa-electronvolts (1.0 to two.5 joules!), the muon flux is 30% to 60% upper than anticipated.
“Even if the analysis concerning the muon puzzle is turning into increasingly more detailed,” Bingyang Liu and his colleagues from East China Commonplace College write, “the reality stays elusive, necessitating additional investigations.”
In tackling the surplus drawback, the workforce wrote that they “generally tend to consider” that the primary distinction between experiments and concept is the preliminary collision in air showers—when the high-energy cosmic ray particle first interacts with a nucleus within the environment. (Those incoming cosmic rays may have energies as excessive because the “Oh my God” particle seen in 1991, which had an calories of 320 exa-eV. That is 25 million occasions the best accelerator energies created on Earth, 13 TeV at CERN.)
Twenty-five years in the past it used to be proposed that during ultrahigh-energy collisions, because the incoming cosmic ray particle (basically protons and helium nuclei) collides with hadrons in atmospheric nuclei, the gluon distribution within the hadrons may go through condensation, forming a gluon condensate. The formation of those gluon condensates would then affect the hadrons therefore produced, which in flip impacts the general muon manufacturing.
Hadrons are debris consisting of 2 or extra quarks—examples are the proton and neutron, with 3 quarks each and every, and pions and kaons with two quarks. Simply as molecules are composed of atoms held in combination through {the electrical} drive, hadrons are composed of quarks held in combination through the robust drive.
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A photon carries {the electrical} drive between electrically charged electrons and protons in atoms and molecules and is described through the speculation of quantum electrodynamics (QED); gluons raise the robust drive between quarks and is described through quantum chromodynamics (QCD).
The adaptation is that, while photons haven’t any electric fee, gluons are charged—charged with the colours of the robust drive. (Quarks, in fact, additionally raise considered one of 3 kinds of colour fee.) This “nonlinearity” makes states ruled through the robust drive a lot more complicated than atoms and molecules. Even with the quantum box concept QCD, robust interplay states are very tough to research, fashion and compute.
We all know that sped up electrical fees emit QED radiation (photons), and those will give a contribution to the hadron cascades from the preliminary cosmic ray collision. So too, sped up coloured quarks (and gluons themselves) emit QCD radiation (gluons). Not like the uncharged photons even though, the gluons have their very own fee and subsequently emit additional radiation, resulting in a lot larger particle showers.
Gluon distributions in hadrons would possibly shape “gluon condensates.” Such high-energy states include numerous gluons at a undeniable calories degree that may generate various the constituent quarks of hadrons, making the hadron cascades more practical, and extending the choice of pions and odd quarks, which make-up kaons.
In a reference body focused at the cascades’ center-of-mass, virtually all to be had collision calories is used to provide those pions and kaons, and therefore produce the general muon that streams to the skin.
The researchers used the gluon condensation fashion described through QCD to research the preliminary collision of the cascades in an try to get to the bottom of the muon extra drawback.
They discovered that transient quark-gluon plasmas may also be shaped through the excessive collision energies of gluons; specifically, their theoretical research discovered that the semblance of a quark–gluon plasma results in an greater choice of odd quarks and antistrange quarks.
“The incidence of the gluon condensate calls for a better collision calories,” they wrote, “and we discover that it results in extra odd quarks (antiquarks) manufacturing than within the quark-gluon plasma stipulations.”
After an advanced calculation, the workforce discovered that the manufacturing of odd quark pairs used to be two to ten occasions better—relying on calories—when starting with a gluon condensate state than in the event that they started with a quark-gluon plasma state.
They conclude through writing, “In high-energy collision experiments, the prevailing analysis means that QGP [quark-gluon plasmas] would possibly happen, however making an allowance for best the traditional QGP impact can not remedy the muon extra drawback within the air bathe. We believe that GC [gluon condensate] would possibly happen in extraordinarily high-energy collisions.
“Within the GC state, the manufacturing of odd quarks will likely be a great deal enhanced,” thus resulting in extra muons at Earth’s floor than would in a different way be the case with out gluon condensates.
Additional information:
Bingyang Liu et al, Explaining Muon Extra in Cosmic Rays The use of the Gluon Condensation Fashion, The Astrophysical Magazine (2024). DOI: 10.3847/1538-4357/ad6b9a
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