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swissforextrading · 2 months

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LHCb observes a new decay mode of the charmed beauty meson

LHCb observes a new decay mode of the charmed beauty meson The LHCb collaboration recently reported the first observation of the decay of the Bc+ meson (composed of two heavy quarks, b and c) into a J/ψ charm-anticharm quark bound state and a pair of pions, π+π0. The decay process shows a contribution from an intermediate particle, a ρ+ meson that forms for a brief moment and then decays into the π+π0 pair. The Bc+ is the heaviest meson that can only decay through the weak interactions, via the decay of one heavy constituent quark. Bc+ decays into an odd number of light hadrons and a J/ψ (or other charm-anticharm quark bound states, called “charmonia”) have been studied intensively and have been found to be in remarkable agreement with the theoretical expectations. The decay of Bc+ into a J/ψ and a π+π0 pair is the simplest decay into charmonium and an even number of light hadrons. It has never been observed before, mainly because the precise reconstruction of the low-energy π0 meson through its decay into a pair of photons is very challenging in an LHC proton-proton collision environment. A precise measurement of the Bc+→J/ψπ+π0 decay will allow better understanding of its possible contribution as a background source for the study of other decays of Bc mesons as well as rare decays of B0 mesons. From the theoretical point of view, decays of Bc into J/ψ and an even number of pions are closely related to the decays of the τ lepton into an even number of pions, and to the e+e– annihilation into an even number of pions. Precise measurements of e+e– annihilation into two pions in the ρ mass region (as in the Bc decay discussed here) are crucial for the interpretation of results from the Fermilab g-2 experiment measuring the anomalous magnetic dipole moment of the muon, since low-energy e+e– annihilation into hadrons is an important source of the uncertainty of the g-2 measurements. The ratio of the probability of the new decay to that of the decay of Bc+ into J/ψπ+ has been calculated by various theorists over the last 30 years. Now these predictions can finally be compared with an experimental measurement: most predictions agree with the new result obtained by LHCb (2.80±0.15±0.11±0.16). The large number of b-quarks produced in LHC collisions and the excellent detector allows LHCb to study the production, decays and other properties of the Bc+ meson in detail. Since the meson’s discovery by the CDF experiment at the Tevatron collider, 18 new Bc+ decays have been observed (with more than five standard deviations), all of them by LHCb. Read more in the LHCb paper. ptraczyk Mon, 03/04/2024 - 10:15 Byline LHCb collaboration Publication Date Mon, 03/04/2024 - 10:06 https://home.web.cern.ch/news/news/physics/lhcb-observes-new-decay-mode-charmed-beauty-meson (Source of the original content)

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starrystvdy · 2 years

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POV: i’ve been trying to get myself to do a particle physics problem sheet all day. i’m exhausted and a bit sick but i finally manage to get myself set up to start working. i open the textbook. on my way to the right page, other subheadings catch my eye. “heavy quarkonia.” “charmonium.” “bottomonium.” i close the textbook. i go to bed.

#t.txt #nothing is real please let me sleep

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maeamian · 7 years

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One of the greatest injustices in the history of scientific naming is that the Top and Bottom quarks were nearly the Truth and Beauty quarks, but I can’t be too mad because it does mean there’s toponium and bottomonium, and that’s good for a chuckle or two.

#I still would have prefered truth and beauty #But there's solace to be taken here #It's definitely not one of the greatest injustices #But it is upsetting to me because we could have lived in that better world #And honestly we'd have Truthonium and Beautyonium so at best that portion is a lateral move #Charmonium is also a thing #Although apparently not strangeonium #Cause the light quark mesons aren't called quarkonium for reasons that probably make sense but I don't know em #Actually toponium doesn't exist either because the top quark decays too quickly to bond with its antiparticle #But if it ever did we'd have that name ready for it #Unless you're a particle physicist you probably don't need to worry about any of these specifics and can just enjoy the funny names

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spaceexp · 5 years

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Bottomonium particles don’t go with the flow

CERN - European Organization for Nuclear Research logo. 20 July, 2019 The first measurement, by the ALICE collaboration, of an elliptic-shaped flow for bottomonium particles could help shed light on the early universe

The ALICE experiment (Image: CERN)

A few millionths of a second after the Big Bang, the universe was so dense and hot that the quarks and gluons that make up protons, neutrons and other hadrons existed freely in what is known as the quark–gluon plasma. The ALICE experiment at the Large Hadron Collider (LHC) can recreate this plasma in high-energy collisions of beams of heavy ions of lead. However, ALICE, as well as any other collision experiments that can recreate the plasma, cannot observe this state of matter directly. The presence and properties of the plasma can only be deduced from the signatures it leaves on the particles that are produced in the collisions. In a new article, presented at the ongoing European Physical Society conference on High-Energy Physics, the ALICE collaboration reports the first measurement of one such signature – the elliptic flow – for upsilon particles produced in lead–lead LHC collisions. The upsilon is a bottomonium particle, consisting of a bottom (often also called beauty) quark and its antiquark. Bottomonia and their charm-quark counterparts, charmonium particles, are excellent probes of the quark–gluon plasma. They are created in the initial stages of a heavy-ion collision and therefore experience the entire evolution of the plasma, from the moment it is produced to the moment it cools down and gives way to a state in which hadrons can form.

Large Hadron Collider (LHC). Animation Credit: CERN

One indication that the quark–gluon plasma forms is the collective motion, or flow, of the produced particles. This flow is generated by the expansion of the hot plasma after the collision, and its magnitude depends on several factors, including: the particle type and mass; how central, or “head on”, the collision is; and the momenta of the particles at right angles to the collision line. One type of flow, called elliptic flow, results from the initial elliptic shape of non-central collisions. In their new study, the ALICE team determined the elliptic flow of the upsilons by observing the pairs of muons (heavier cousins of the electron) into which they transform, or “decay”. They found that the magnitude of the upsilon elliptic flow for a range of momenta and collision centralities is small, making the upsilons the first hadrons that don’t seem to exhibit a significant elliptic flow. The results are consistent with the prediction that the upsilons are largely split up into their constituent quarks in the early stages of their interaction with the plasma, and they pave the way to higher-precision measurements using data from ALICE’s upgraded detector, which will be able to record ten times more upsilons. Such data should also cast light on the curious case of the J/psi flow. This lighter charmonium particle has a larger flow and is believed to re-form after being split up by the plasma. Note: CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature. The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions. Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 23 Member States. Related links: ALICE experiment: https://home.cern/science/experiments/alice Large Hadron Collider (LHC): https://home.cern/science/accelerators/large-hadron-collider European Physical Society conference on High-Energy Physics: http://eps-hep2019.eu/ Science article: https://arxiv.org/abs/1907.03169 ALICE’s upgraded detector: https://home.cern/news/news/experiments/upgrading-alice-whats-store-next-two-years The curious case of the J/psi flow: https://cerncourier.com/the-curious-case-of-the-j-%CF%88-flow/ For more information about European Organization for Nuclear Research (CERN), Visit: https://home.cern/ Image (mentioned), Animation (mentioned), Text, Credits: CERN/Ana Lopes. Greetings, Orbiter.ch Full article

#space #science

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sciencecover-blog · 5 years

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physicists measure the elliptical flow of Bottomonium molecules

Physicists, in collaboration with ALICE at CERN, have announced the first measurement of the elliptical form of the Butomon particle flow consisting of its ground quark and antiquark.

Upsilone is butymonium soil particles, often called beauty quarks or antiquarks. Charming bottomonia and quark particles from charmonium particles are very good probes for quark gluon plasma. They appear in the…

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#alice #antiquark #bottomonium #charmonium #collision #elliptical #interaction #ions #molecules #physics #plasma

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spacetimewithstuartgary · 6 years

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New observations to understand the phase transition in quantum chromodynamics New findings published in Nature on the formation of matter, Experiments provide information on the beginnings of the universe The building blocks of matter in our universe were formed in the first 10 microseconds of its existence, according to the currently accepted scientific picture. After the Big Bang about 13.7 billion years ago, matter consisted mainly of quarks and gluons, two types of elementary particles whose interactions are governed by quantum chromodynamics (QCD), the theory of strong interaction. In the early universe, these particles moved (nearly) freely in a quark-gluon plasma. Then, in a phase transition, they combined and formed hadrons, among them the building blocks of atomic nuclei, protons and neutrons. In the current issue of the science journal Nature, an international team of scientists presents an analysis of a series of experiments at major particle accelerators which sheds light on the nature of this transition. The scientists determined with precision the transition temperature and obtained new insights into the mechanism of cooling and freeze-out of the quark-gluon plasma into the current constituents of matter such as protons, neutrons, and atomic nuclei. The team of researchers consists of scientists from the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, and from the universities of Heidelberg and Münster (Germany), and Wroclaw (Poland). Analysis of experimental results confirm the predicted value of the transition temperature / Onehundred and twenty thousend times hotter than the interior of the sun A central result: The experiments at world-wide highest energy with the ALICE detector at the Large Hadron Collider (LHC) at the research center CERN produce matter where particles and anti-particles coexist, with very high accuracy, in equal amounts, similar to the conditions in the early universe. The team confirms, with analysis of the experimental data, theoretical predictions that the phase transition between quark-gluon plasma and hadronic matter takes place at the temperature of 156 MeV. This temperature is 120,000 times higher than that in the interior of the sun. "Snowballs in hell" The physicists analyzed more precisely the yields of a number of particles and anti-particles. "Our investigations revealed a number of surprizing discoveries. One of them is that light nuclei and their anti-particles are produced at the same temperature as protons and anti-protons, although their binding energies are about 100 times smaller than the energy corresponding to the transition temperature", explains Prof. Dr. Anton Andronic who recently joined the University of Münster from the GSI Helmholtzzentrum für Schwerionenforschung. The scientists presume that such "loosely bound objects" are formed at high temperature first as compact multi-quark objects which only later develop into the observed light nuclei and anti-nuclei. The existence of such multi-quark states was proposed a long time ago but no convincing evidence was found. "Confinement": Charm quarks travel freely in the fireball Another remarkable observation concerns a phenomenon long known but poorly understood: Normally, quarks are confined into the interior of protons and neutrons; isolated quarks have never been observed, a property which scientists describe as "confinement". In the interior of the fireball formed in nuclear collisions at high energy this confinement is lifted (deconfinement). The new study shows that charmonium states such as J/psi mesons, consisting of a pair of charm and anti-charm quarks, are produced far more often at LHC energies compared to observations at lower energies, such as at the "Relativistic Heavy Ion Collider" in the USA. Because of the higher energy density at LHC the opposite, namely a reduction of J/psi mesons through dissociation was expected. In contradistinction, enhancement was predicted 18 years ago by two of the team members (Prof. Dr. Peter Braun-Munzinger, GSI, and Prof. Dr. Johanna Stachel, Universität Heidelberg) because of deconfinement of the charm quarks. The consequences of the prediction were worked out in detail in a series of publications by the whole team. The now observed enhanced production of J/psi particles confirms the prediction: J/psi mesons can only be produced in the observed large quantities if their constituents, the charm- and anticharm quarks, can travel freely in the fireball over distances of a trillionth of a centimeter - corresponding to about ten times the size of a proton. "These observations are a first step towards understanding the phenomenon of confinement in more detail", underlines Prof. Dr. Krzysztof Redlich of the University of Wroclaw (Poland). Experiments at CERN and at Brookhaven National Laboratory The data were obtained during several years of investigations in the framework of the experiment "ALICE" at the Large Hadron Collider accelerator at the research center CERN near Geneva. In "ALICE", scientists from 41 countries investigated in collisions between two lead nuclei the state of the universe within microseconds after the Big Bang. The highest ever man-made energy densities are produced in such collisions. These result in the formation of matter (quarks and gluons) as it existed at that time in the early universe. In each head-on collision more than 30,000 particles (hadrons) are produced which are then detected in the ALICE experiment. The actual study also used data from experiments at lower energy accelerators, the "Super Proton Synchrotron" at CERN and the "Relativistic Heavy Ion Collider" at the US-Brookhaven National Laboratory on Long Island, New York.

#space #science #Astronomy #astrophysics #cosmology #CERN #brookhaven national laboratory #physics

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ladystylestores · 4 years

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CERN has discovered a very charming particle

Enlarge / Particle tracks from the LHCb detector.

The quark model was an intellectual revolution for physics. Physicists were faced with an ever-growing zoo of unstable particles that didn’t seem to have a role in the Universe around us. Quarks explained all that through an (at least superficially) simple set of rules that built all of these particles through combinations of two or three quarks.

While that general outline seems simple, the rules by which particles called “gluons” hold the quarks together in particles are fiendishly complex, and we don’t always know their limits. Are there reasons that particles seem to stop at collections of three quarks?

With the advent of ever-more powerful particle colliders, we’ve found some indications that the answer is “no.” Reports of four-quark and even five-quark particles have appeared in different experiments. But questions remain about the nature of the interactions in these particles. Now, CERN has announced a new addition to growing family of tetraquarks, a collection two charm quarks and two anti-charm quarks.

How do you put that together?

The quark-based particles we’re most familiar with, the proton and neutron, are composed of three of the lightest quarks bound tightly together via gluons. We’ve also discovered heavier versions of these familiar particles, where one of the up or down quarks is replaced by a heavier quark, like a strange or bottom. In addition, there is a large collection of unstable particles, collectively called mesons, that involve two quarks of various masses, also held together by gluons.

So, what happens when you try to cram more quarks in? We’re not entirely sure. There are two possibilities that are being considered. In one case, the new high-quark-count particles are made the same way that familiar ones are: gluons bind them tightly together into a single particle. An alternative, however, is that the large number of quarks comes about because two more familiar particles are tightly associated. So, a tetraquark could simply be a tight association of a pair of two-quark particles. A pentaquark would be put together from a two-quark meson associating with a three-quark particle.

Unfortunately, we’ve found it difficult to tell these two options apart. These high-quark-count particles tend to decay extremely rapidly to familiar particles, and it’s generally only the decay of those latter particles that we can track. That makes it challenging to determine exactly what’s going on further back. So, the more ways we can look at these things, the better. And that brings us to the latest results from CERN, in which a team of scientists has analyzed the data from the first few runs of the LHC.

The data comes out of the LHCb experiment, a detector that’s specialized in particles containing the very heavy bottom (or beauty) quark. But it’s capable of picking up heavier quarks more generally. And the new particle has a lot of heavier quarks.

Needs more charm

So far, all the high-quark-count particles we’ve found have been a mix of mostly lighter up and down quarks, with a couple of their heavier peers thrown in. But the CERN team was interested in looking for combinations where all the quarks were either charm or anti-charm. Charm quarks are from the middle generation of quarks; charm and strange are heavier than up or down but far lighter than top or bottom.

How would we find something like that? Conveniently, a four-charm particle should decay through an intermediate state that involves a pair of two-charm particles. And these we know very well as the J/ψ particle. (Two groups found this particle at roughly the same time and, in a rare moment of compromise, the names given to it by both of them have stuck.) Since we know how J/ψ particles decay, we can simply look for pairs of decays coming out of a single proton-proton collision.

The decay of J/ψ particles can, in turn, be recognized by the appearance of a muon-antimuon pair that originates from a single location. (Muons can be thought of as heavier, unstable cousins of the electron.) Since there should be two of the J/ψ particles, then we need to look for two pairs of muon tracks in the aftermath of a collision.

So, the researchers scanned a range of energies for an excess of these events. And they find one in the appropriate energy range for a four-charm particle that is five standard deviations from the expected background noise. That means it meets the standard for discovery in particle physics.

The new particle, currently unnamed, is the first with more than three quarks that is composed entirely of one type of quark, as well as the first to be composed entirely of heavier quarks. And, given that the specific quark is called “charm,” its existence opens vast possibilities for puns‐and that’s without even getting into the fact that the technical term for the full family of particles containing these quarks is “charmonium.”

What’s its deal?

But the big question hasn’t been answered: what’s the nature of the new particle? We don’t know if it’s simply two J/ψ particles in tight association or whether there’s a single particle composed of four charm quarks. The answer is fairly important, since it would provide information on the strong force that governs all quark-gluon interactions.

Still, the more of these particles we have to study, the greater the chances are that we’ll be able to determine the details of what it takes to build them. So, while it would have been nice if this particle immediately heralded the solution to an outstanding question, its discovery is likely to represent progress toward a solution.

The arXiv. Abstract number: 2006.16957 (About the arXiv).

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littlejoe59 · 5 years

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The LHCb collaboration has spotted a new particle, dubbed the ψ3(1D). Its mass and other properties place it squarely in the charmonium family that includes the better-known J/ψ particle, which was the first particle containing a “charm quark” to be discovered and won its discoverers a Nobel prize in physics.

#technology

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outsidetheknow · 5 years

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New top story on Hacker News: Monads as a Programming Pattern

Monads as a Programming Pattern 2 by charmonium | 0 comments on Hacker News.

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#Hacker News charmonium Monads as a Programming Pattern https://news.ycombinator.com/item?id=20673506

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scienceblogtumbler · 4 years

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First Ten Years of the LHC: The Adventure Continues

After ten years in operation, the CERN particle accelerator located on the border between France and Switzerland has reshaped the physics of elementary particles. It will restart in 2021 with even better-performing facilities.

The LHC (Large Hadron Collider) has now been running at full capacity for a decade, together with the four experiments that detect the particles produced by collisions between protons, one of the components of atomic nuclei. At a rate of around 30 million times a second, the huge accelerator collides protons at speeds close to that of light, in a tunnel measuring 27 kilometres in circumference.

The thousands of researchers, engineers and technicians taking part in this unprecedented scientific venture at CERN near Geneva (Switzerland) seek to shed more light on the physics of elementary particles and hence on the fundamental laws of the Universe. Ever since the launch of the most extraordinary particle physics experimental facility ever designed, there has been a wealth of surprises and discoveries, including a Nobel prize along the way. And this is only just the beginning. With the installations currently being upgraded to boost their performance, the project is scheduled to last until at least 2037.

A huge instrument

The LHC is based on a simple principle: every time the accelerated protons collide, their accumulated kinetic energy is transformed into “grains” of matter, as a result of the equivalence between matter and energy. These newly-formed particles provide clues about the elementary processes that gave rise to them. Around twenty years ago, the proponents of the LHC calculated that, in order to detect significant phenomena, the protons needed to reach an energy of 7 teraelectronvolts (TeV), roughly that of a mosquito in flight but squeezed into a volume a trillion times smaller. This is why such a huge accelerator was needed, as well as four exceptional detectors, ATLAS, CMS, LHCb and ALICE, to observe the tiny particles produced by the collisions. ATLAS, for example, is a 40-metre long cylinder that has a diameter of 22 metres and a weight of 7,000 tonnes, while CMS, with a 15-metre diameter and a length of 21.5 metres, weighs in at a staggering 12,500 tonnes.

Higgs boson produced together with two top quarks in ATLAS.

CERN / ATLAS

French scientists have played a significant role in each of these international collaborations. As Laurent Vacavant, deputy scientific director at the CNRS’s National Institute of Nuclear and Particle Physics (IN2P3), explains, “France provides 14% of the CERN budget and covers 10% of the cost of the detectors. Specifically, ten IN2P3 laboratories are involved in the four experiments, with 250 researchers, 280 engineers and technicians, and around a hundred PhD students working on a permanent basis, in addition to about 150 staff from the CEA’s Institute for Research into the Fundamental Laws of the Universe.” Over the past ten years, French teams, alongside 600 institutes and universities from across the world, have been involved in designing and building the detectors and analysing the results, as well as in operating and maintaining the facilities.

The Higgs boson finally detected

The LHC brings together several experiments designed to find answers to a number of distinct or related problems. ATLAS and CMS are what are called discovery detectors. As Vacavant points out, “with their tens of millions of sensors, they can collect data in every possible area”, which enabled them to finally track down a particle that, ten years ago, was purely hypothetical: the Higgs boson. The existence of this particle, thought to give nearly all other molecules their mass, had been predicted since 1964, but never detected.

Detection in the CMS of the Higgs boson decaying into 4 leptons (one of the ways it was discovered in 2012).

CERN / CMS

Yet the power of the LHC enabled surprisingly fast progress to be made. As Isabelle Wingerter-Seez, in charge of Atlas-France until 2017, explains, “at the start, we thought it would take five or six years before we spotted anything. But as early as 2011 we began to notice a signal emerge from the noise, and in 2012 we were able to confirm that the Higgs boson was there!” Didier Contardo, who heads CMS-France, recalls: “we knew how best to detect it, the experiments and the analysis chain proved to be as successful as expected – if not more so – and both detectors observed the same thing at the same level of accuracy.” The discovery was announced on 4 July, 2012 in the CERN main auditorium. And the following year, François Englert and Peter Higgs, the scientists who had hypothesised the boson back in 1964, were awarded the Nobel prize (having died in 2011, Robert Brout could not receive the award).

Higgs boson decaying into 2 bottom quarks, produced in association with two top quarks.

CERN / CMS

Still no sign of new physics

The Higgs boson provided the missing piece of the Standard Model of physics (SMP), which describes all known elementary particles and their interactions (except for gravity). ATLAS and CMS, however, were also designed to discover unknown elementary particles and uncover new physics not described by the Model. To explain the nature of dark matter (article in French), the value of physical constants, or the absence of antimatter (article in French) in the Universe, it is necessary to go beyond the SMP – except that, much to everyone’s surprise, ten years of hard work failed to produce any evidence of new physics: “we didn’t spot even the tiniest hint of something that didn’t fit the Standard Model,” Wingerter-Seez explains.

The LHCb was designed to study the slight asymmetries between matter and antimatter.

Cyril FRESILLON/LHC/CNRS Photothèque

Could it be that new physics simply doesn’t exist? Or that it exists in ways that haven’t yet been thought up? Or are its signals more exotic than those sought by the detectors? Nobody knows as yet. Therefore, having followed the most obvious leads, the experimenters are now hunting painstakingly for new clues. “We’re searching in less accessible areas for unusual processes, complex observables, models of new physics that were in principle less popular, and so on,” Contardo confirms.

Consequently, after the initial euphoria of its discovery, researchers have now embarked on a meticulous study of the Higgs boson, in particular to determine how it interacts with each of the known particles of matter. For example, in 2018 they observed its coupling to the top quark (the most massive elementary particle known to date) and its interaction with the bottom quark. What the scientists are hoping for is that they may spot some small discrepancies from the predictions of the Standard Model.

However, the surprise might come from the LHCb experiment, which studies the decay of particles called B mesons. According to the SMP, matter and antimatter are almost identical in every way. And yet there is absolutely no antimatter in the Universe, which is one of the great mysteries of fundamental physics. This prompted specialists to compare the properties of B mesons and B anti-mesons, with the aim of detecting a possible difference that might provide a clue.

A B Meson decaying into two muons.

CERN / LHCb

Although this isn’t the case for the time being, LHCb has nonetheless observed a number of odd phenomena in the past few years: for instance, some mesons can decay either into electrons or into their heavier cousins, muons. However, as Renaud Le Gac, who leads LHCb-France, explains, “the Standard Model states that the two processes should be perfectly identical, but according to our data this is not exactly true. Although at this stage the differences are not yet significant, they provide the most promising route to observing physics beyond the SMP.”

Quarks galore

The CERN researchers have also made some other exciting discoveries within the framework of the Standard Model. For instance, whereas until now only particles made up of two or three quarks (such as protons and neutrons) were known, in 2017 the LHCb experiment produced a subatomic particle composed of five quarks, the pentaquark. This has helped improve the modelling of quarks and of the strong interaction, which binds together both quarks and the components of the atomic nucleus.

Representation of the hypothetical internal structure of a pentaquark.

CERN / LHCb

The strong force and its mediators, gluons, are also the focus of research carried out at the ALICE detector, which studies a highly remarkable state of matter called quark-gluon plasma or QGP. The latter is obtained by colliding the nuclei of lead atoms, producing an extremely hot and dense “soup” made up of quarks and gluons, which are normally confined within protons and neutrons. This is thought to be the state the Universe was in, a microsecond after the Big Bang.

As Cvetan Cheshkov, deputy physics coordinator of ALICE, explains, “the energy produced in the LHC enables us to obtain the hottest, densest and longest-lived QGP ever observed.” Aside from breaking new records, this makes it possible to study the QGP in greater detail and determine its specific characteristics using new experimental methods. For the first time last year, for example, the physicists at ALICE detected particles known as charmonium, which are formed from the plasma, when quarks and gluons recombine. This shows that the particles were in a free state just before then. According to Cheshkov,“this is one of the clearest indications that a QGP really was produced.”

Heavy ion collisions recorded by ALICE on 25 November 2015.

CERN / ALICE

In addition, the scientists were also able to specify the nature of the quark-gluon plasma. While according to theoretical models, it was expected that the primordial Universe, given its enormously high temperature, resembled a gas, it turns out that its properties were probably more like those of a liquid; what’s more, a liquid of a very special kind, since it is able to flow without any friction at all – in other words, a state of matter with no known equivalent.

Tiny droplets of QGP have also recently been observed. Half way between an extensive plasma and a collection of particles, they bridge the gap between the elementary theory of quarks and gluons, and the hydrodynamic models of the QGP used to describe its expansion and cooling.

While the LHC has already provided some answers, it has also raised new questions, some of them mind-boggling. To find the solutions, all the teams are endeavouring to crank up the performance of the accelerator and detectors, which are scheduled to resume operation in 2021. Some of the upgrades are being carried out in preparation for what is called the High-Luminosity LHC, which, after all of the analysis hardware and software have been adapted, will from 2027 see the number of collisions per second increase at least five-fold at the centre of the detectors. As Vacavant points out, “to date we have collected only 5% of the data that the LHC will produce during its lifetime.” What will particle physicists find out when they analyse this mountain of data? No one knows. However, Vacavant is convinced that “in the constant dialectical relationship between theoretical and experimental advances, we are now in a phase where it is up to the experimenters to clear the ground ahead.” In any case, one thing is certain. The LHC’s first ten years are merely the beginning of this extraordinary scientific adventure.

source https://scienceblog.com/515727/first-ten-years-of-the-lhc-the-adventure-continues/

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swissforextrading · 2 months

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LHCb observes a new decay mode of the charmed beauty meson

LHCb observes a new decay mode of the charmed beauty meson The LHCb collaboration recently reported the first observation of the decay of the Bc+ meson (composed of two heavy quarks, b and c) into a J/ψ charm-anticharm quark bound state and a pair of pions, π+π0. The decay process shows a contribution from an intermediate particle, a ρ+ meson that forms for a brief moment and then decays into the π+π0 pair. The Bc+ is the heaviest meson that can only decay through the weak interactions, via the decay of one heavy constituent quark. Bc+ decays into an odd number of light hadrons and a J/ψ (or other charm-anticharm quark bound states, called “charmonia”) have been studied intensively and have been found to be in remarkable agreement with the theoretical expectations. The decay of Bc+ into a J/ψ and a π+π0 pair is the simplest decay into charmonium and an even number of light hadrons. It has never been observed before, mainly because the precise reconstruction of the low-energy π0 meson through its decay into a pair of photons is very challenging in an LHC proton-proton collision environment. A precise measurement of the Bc+→J/ψπ+π0 decay will allow better understanding of its possible contribution as a background source for the study of other decays of Bc mesons as well as rare decays of B0 mesons. From the theoretical point of view, decays of Bc into J/ψ and an even number of pions are closely related to the decays of the τ lepton into an even number of pions, and to the e+e– annihilation into an even number of pions. Precise measurements of e+e– annihilation into two pions in the ρ mass region (as in the Bc decay discussed here) are crucial for the interpretation of results from the Fermilab g-2 experiment measuring the anomalous magnetic dipole moment of the muon, since low-energy e+e– annihilation into hadrons is an important source of the uncertainty of the g-2 measurements. The ratio of the probability of the new decay to that of the decay of Bc+ into J/ψπ+ has been calculated by various theorists over the last 30 years. Now these predictions can finally be compared with an experimental measurement: most predictions agree with the new result obtained by LHCb (2.80±0.15±0.11±0.16). The large number of b-quarks produced in LHC collisions and the excellent detector allows LHCb to study the production, decays and other properties of the Bc+ meson in detail. Since the meson’s discovery by the CDF experiment at the Tevatron collider, 18 new Bc+ decays have been observed (with more than five standard deviations), all of them by LHCb. Read more in the LHCb paper. ptraczyk Mon, 03/04/2024 - 10:15 Byline LHCb collaboration Publication Date Mon, 03/04/2024 - 10:06 https://home.cern/news/news/physics/lhcb-observes-new-decay-mode-charmed-beauty-meson (Source of the original content)

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