Matter-antimatter asymmetry may interfere with the detection of neutrinos

Matter-antimatter asymmetry may interfere with the detection of neutrinos
Comparison of mechanisms of favored and unfavored fragmentation of quarks. (Source: IFJ PAN). Credit: IFJ PAN

From the data collected by the LHCb detector at the Large Hadron Collider, it appears that the particles known as charm mesons and their antimatter counterparts are not produced in perfectly equal proportions. Physicists from Cracow have proposed their own explanation of this phenomenon and presented related predictions about consequences that are particularly interesting for high-energy neutrino astronomy.

In the first moments after the Big Bang, the universe was filled with equal amounts of particles and antiparticles. While it was cooling down, matter and antimatter began to merge and annihilate, becoming radiation. The matter that survived annihilation now comprises the universe, but this imbalance is poorly understood. In order to decipher this great mystery of modern science, physicists are trying to better understand all the mechanisms responsible for even the smallest disproportions in the production of particles and antiparticles. A group of scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow, associated with the LHCb experiment at the Large Hadron Collider in Geneva, recently looked into one of these processes: the asymmetry appearing at the birth of charm mesons and antimesons. The conclusions from the analysis could be of very tangible practical significance.

According to modern physics, quarks are the most important indivisible building blocks that make up matter. We know of six flavours of quarks: up (u), down (d), strange (s), charm (c), bottom (b) and top (t); each flavour also has its own antimatter counterpart (often marked with a dash above the letter, read as "bar"). Quarks are generally formed in -antiquark pairs. They are extremely sociable particles: almost immediately after coming into being, they bind into hadrons, or groups of two, three, and sometimes more quarks or antiquarks, bonded with gluons (i.e. particles transferring strong nuclear interactions). The process of combining quarks/antiquarks into complexes is called hadronization.

Unstable hadrons built from quark-antiquark pairs are called mesons. If one of the quarks in a meson is a charm quark, the particle is called a charm meson and is denoted by the letter D (or for the charm antiquark: D with a bar above it). A pair built of a charm quark and a down antiquark is a D+ meson, and one consisting of a charm antiquark and down quark is a D- meson.

In measurements conducted in the last quarter of a century, including recently as part of the LHCb experiment, an interesting asymmetry was noticed. It turned out that D+ and D- mesons are not always produced in exactly the same proportions. In the case of processes observed in LHCb, initiated in collisions of counter-current beams of high-energy protons, this asymmetry was small, less than one percent.

"Charm quarks are mainly formed during gluon collisions in so-called hard interactions, and after birth, they hadronise into D mesons. We investigated another meson formation mechanism, known as unfavoured quark fragmentation. Here, the charm is created as a result of hadronization of a light (up, down, or strange) quark or antiquark. By means of the nuances of this mechanism, the asymmetry between kaons and antikaons, i.e. K+ and K- mesons, was explained earlier. Until now, however, it has not been investigated whether a similar mechanism could explain the asymmetry between the relatively massive D+ and D- mesons," says Dr. Rafal Maciula (IFJ PAN), the first author of the publication in the journal Physical Review D.

The LHCb detector mainly measures particles diverging from the point of collision of protons at large angles to the original direction of movement of these protons. According to the Cracow-based physicists, the asymmetry in the production of D mesons should be much greater if particles produced in a forward direction are taken into account, that is, along the direction of the proton beams. This means that the currently observed disproportion may be just the tip of an iceberg. Calculations suggest that in the case of "forward" collisions, unfavoured fragmentation (d, u, s ' D) may be comparable to conventional fragmentation (c ' D). As a result, the asymmetry between D+ and D- mesons may reach a high percentage, even at lower collision energies than those currently occurring in the LHC.

The research of the physicists from the IFJ PAN may have far-reaching consequences for neutrino observatories such as the IceCube Observatory in Antarctica. This detector, in which 49 scientific institutions from 12 countries collaborate, monitors a cubic kilometre of ice, located almost a kilometre below the surface, using thousands of photomultipliers. Photomultipliers track subtle light flashes initiated by the interaction of ice-forming particles with neutrinos, elementary very weakly interacting with ordinary matter.

IceCube registers several hundred neutrinos a day. It is known that a large proportion of them are created in the Earth's atmosphere in processes initiated by cosmic rays and taking place with the participation of protons. Other neutrinos may come from the Earth's core or from the Sun. It is assumed, however, that neutrinos with significant energies have reached the detector directly from distant cosmic sources, including supernovae, merging black holes or neutron stars.

"When interpreting data from the IceCube detector, the production of neutrinos in the Earth's atmosphere caused by ordinary cosmic radiation, including collisions involving protons, is taken into account. The thing is that some of these processes, resulting in the formation of neutrinos with high energies, take place with the participation of D mesons. Meanwhile, we show that the mechanism of production of these mesons in the atmosphere can be much more efficient than previously thought. So, if our assumptions are confirmed, some of the highly energetic neutrinos registered, now considered to be of cosmic origin, have actually appeared just above our heads and are disturbing the real picture of events in the depths of space," explains Prof. Antoni Szczurek (IFJ PAN).

When just the tip of the iceberg can be seen, inferences about what the rest of it looks like is more than risky. The model proposed by the Cracow-based physicists has the status of a hypothesis today. Perhaps it does fully describe the mechanism that occurs in reality. But it may also be that other processes are responsible for the asymmetry in the production of D mesons, maybe partially or even in their entirety.

"Fortunately, no other competitive proposal predicts such a clear increase in in the production of D mesons at lower collision energies. So to check our assumptions, it would suffice in the LHC accelerator to direct a single beam onto a stationary target, which would significantly reduce the collision energy. Our model therefore meets the criteria of very reliable science: it not only explains previous observations, but above all, it can be rapidly verified. In addition, this can be done very cheaply," says Prof. Szczurek.


Explore further

At the LHC, charmed twins will soon be more common than singles

More information: Rafał Maciuła et al, D meson production asymmetry, unfavored fragmentation, and consequences for prompt atmospheric neutrino production, Physical Review D (2018). DOI: 10.1103/PhysRevD.97.074001
Journal information: Physical Review D

Provided by The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
Citation: Matter-antimatter asymmetry may interfere with the detection of neutrinos (2018, May 25) retrieved 25 August 2019 from https://phys.org/news/2018-05-matter-antimatter-asymmetry-neutrinos.html
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May 25, 2018
A huge flaw in the Big Bang Hypothesis stimulates a scramble to paper over the cracks...for some 30 years we were told that expansion was initially very fast and then gradually slowed, the prediction was that this slowing would be measurable today...but the expansion is speeding up, not slowing down, so Dark Energy was required to paper over that crack.

And we were told that all the matter in the universe was compacted into a point and expanded out but that would have required a grand unifying theory which never materialised so they changed their minds and decided that most of the matter of the universe simply emerged from quantum fluctuations after a period of inflation even though this emergence process has never been seen since and can not be produced in the laboratory and would require equal amounts of matter and antimatter, which is not observed.

May 25, 2018
@RobertKarlStonjek (and @ anyone else reading this).

Yes. Well observed, @RKS.

And you touch upon one of the most exasperating (and most hypocritical) attempts by the Big Bang fantasy bandwagon of hack 'theoreticians' and their plethora of hack 'publish-or-perish' papering-over-the-cracks' attempts.

It has also saddened me to watch (over decades!) just how dishonest the 'BB crowd' has been.

For example, they now resort to Steady State Universe idea of 'new' matter arising from the quantum fluctuation of energy background inherent in the vacuum!

They have no shame, it seems. There they were for decades, 'pooh-poohing' and ridiculing Steady State Universe hypotheses/proponents; but in the end they have been desperately driven to STEAL the most logically/scientifically tenable idea underlying all Steady State/Recycling Energy-Matter Universe Hypotheses!

How ungrateful and lame can the current 'professional cosmology theorizing/publishing crowd' get?

Shame on them. :(

May 25, 2018
RC,
I would be interested in knowing your angle on Garrett Lise, E8 and Irwin Clee....

May 25, 2018
A huge flaw in the Big Bang Hypothesis...for some 30 years we...expansion was initially very fast and then gradually slowed, the...slowing would be measurable today...but the expansion is speeding up, not slowing down, so Dark Energy was required.. that crack.
And we were told...[/q
I am a layman so perhaps I have less right to voice an opinion. I admit now that I tend to lean towards mainstream but I am also a bit of a 'rebel'. I find it ironic that the very person who used the phrase 'BB' on radio (Sir F. Hoyle) was not a proponent of that theory. In turn I don't see the terms DM, DE, D. Vortex etc. as tablets of stone, as it were. For me they are just a way of saying 'there is something going on there and we don't know what's causing it. I like to read about alternative theories as well as mainstream so I can form some opinion. Some disapprove of that approach...but that doesn't matter, it's all interesting stuff and I have no ego to bruise...now, who said that? Ha!


May 25, 2018
A huge...Big Bang Hypothesis...for some 30 years we...expansion was initially very fast and then gradually slowed, the...slowing..measurable today...but the expansion is speeding up, not slowing down, so Dark Energy was required.. that crack.
And we were told... [/q ]

I am a layman so perhaps I have less right to voice an opinion. I admit that I tend to lean towards mainstream but I am also a bit of a 'rebel'. I find it ironic that the very person who used the phrase 'BB' on radio (Sir F. Hoyle) was not a proponent of that theory. In turn I don't see the terms DM, DE, D. Vortex etc. as tablets of stone, as it were. For me they are just a way of saying 'there is something going on there and we don't know what's causing it. I like to read about alternative theories as well as mainstream so I can form some opinion. Some disapprove of that approach...doesn't matter, it's all interesting stuff and I have no ego to bruise...now, who said that? Ha! Whoops 2 posts.


May 26, 2018
sir To my mind the Big Bang is the explosion due to action of anti matter on matter. The result was dark matter and energy. The first energy is a sound having frequency ten to the power ten hertz.

May 26, 2018
@Whydening Gyre.

Hi, mate; long time no 'speak'!, as it were. My fault; been very busy; only have time for one or two posts now and then. I trust you/yours have been well. Anyhow, fortunately, I always 'make time' for reading-only through PO articles/discussions, as always; and I happened across this:
RC,
I would be interested in knowing your angle on Garrett Lise, E8 and Irwin Clee....
As Garret Lisi himself admits, E8-Theory is incomplete construct; and any 'predictions' based on it are not to be relied upon.

Just like all 'modern' abstract mathematical/geometrical/statistical 'theories/models', it is itself merely abstract 'mathturbation' and/or heuristic 'fitting exercise'; and NOT any sort of 'fundamental-entities/processes-derived PHYSICALLY REAL explanation/description started from reality-based fundamentals themselves.

Re Klee Irwin: He too admits statistically/etc-based QM 'theorizings' are 'heuristic exercises'.

Enough said, WG? :)


May 27, 2018
@Whydening Gyre.

Hi, mate; long time no 'speak'!, as it were. My fault; been very busy;

No, mine. Dealing with senior parent issues...
RC,
I would be interested in knowing your angle on Garrett Lise, E8 and Irwin Clee....

As Garret Lisi himself admits, E8-Theory is incomplete construct; and any 'predictions' based on it are not to be relied upon.
...
Re Klee Irwin: He too admits statistically/etc-based QM 'theorizings' are 'heuristic exercises'.

Enough said, WG? :)

Sure.
As I've expressed to Lisi, any/all pattern summations observed are strictly a product of our own brain structure and process. As such, they must be questioned rigorously.


May 30, 2018
Looks like we will have to wait until we get off planet neutrino detectors to continue research. Unless there is a way to tell the difference in the origin of the neutrino.

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