Most Of The Standard Model Is Irrelevant Most Of The Time

This is cut and pasted from an answer that I provided at Physics Stack Exchange to a question regarding the impact that second and third generation quarks have in our daily lives:

Every nucleon has what are called sea quarks in it, in addition to the valence quarks that define the nucleon as a proton or neutron. Some of those sea quarks, especially the strange quarks, have some secondary relevance in practical terms regarding how the residual strong nuclear force between protons and neutrons in an atomic nucleus is calculated from first principles and how stable a free neutron is if you calculate that from first principles. Strange quarks are also found in the Λ0 baryon (which has quark structure 𝑢𝑑𝑠), which is present at a low frequency in cosmic rays, but has a mean lifetime of only about two tenths of a nanosecond and is only indirectly detected in the form of its decay products.

Strange quarks are also relevant at a philosophical level that could impact your daily life, because mesons including strange quarks called kaons, are the lightest and most long lived particles in which CP violation is observed; thus, strange quarks are what made it possible for us to learn that the laws of physics at a quantum level are not independent of an arrow of time.

You could do a lot of sophisticated engineering for a lifetime without ever knowing that second or third generation quarks existed, even nuclear engineering. Indeed, the basic designs of most nuclear power plants and nuclear weapons in use in the United States today were designed before scientists knew that they existed. The fact that protons and neutrons are made out of quarks was a conclusion reached in the late 1960s and not widely accepted until the early 1970s, although strange quark phenomena were observed in high energy physics experiments as early as the 1950s. Third generation fermions were discovered even later. The tau lepton was discovered in 1974, the tau neutrino in 1975, the b quark in 1977, and the top quark in 1995 (although its existence was predicted and almost certain in the 1970s).

Otherwise, these quarks are so ephemeral and require such concentrated energy to produce, that they have no real impact on daily life and are basically never encountered outside of high energy physics experiments, although some of them may be present in and influence to properties of distant neutron stars. Second and third generation quarks also definitely played an important part in the process of the formation of our universe shortly after the Big Bang.

The only second or third generation fermion in the Standard Model with significant practical engineering applications and an impact on daily life and on technologies that are used in the real world are muons (the second generation electron). Muons are observed in nature in cosmic rays (a somewhat misleading term since it doesn't include only photons) and in imaging technologies similar to X-rays but with muons instead of high energy photons. Muons are also used in devices designed to detect concealed nuclear isotypes. Muons were discovered in 1937, although muon neutrinos were first distinguished from electron neutrinos only in 1962, and the fact that neutrinos have mass and that different kinds of neutrinos have different masses was only established experimentally in 1998.

65 BSM Theories And Core Theory Principles That I Doubt

While I am willing to entertain arguments and evidence to the contrary, I very strongly doubt that any of the following (which are common components of beyond the Standard Model theories except the last which is part of "core theory") are true (some of which are redundant):

1. The PMNS matrix has more than four parameters or does not imply percentages that add to 100%.
2. Sterile neutrinos that oscillate with active neutrinos exist.
3. There are right handed neutrinos and left handed anti-neutrinos.*
4. Neutrinos have Majorana mass.*
5. A seesaw mechanism gives rise to neutrino mass.*
6. Neutrinoless double beta decay is possible in a manner that does not conserve lepton number.
7. Proton decay occurs.
8. There are tree level flavor changing neutral currents.
9. Lepton number is not conserved or baryon number is not conserved outside sphaleron interactions.
10. The baryon number of the universe at t=0 plus an infinitesimal amount was 0.
11. The lepton number of the universe at t=0 plus an infinitesimal amount was 0.
12. The baryon number of the universe minus the lepton number of the universe at t=0 plus an infinitesimal amount was 0.
13. Dark matter particles (other than gravitons) exist.
14. Axions exist.
15. Supersymmetric particles exist.
16. There is a fourth generation of Standard Model fermions.
17. There are pseudo-scalar, charged or different mass scalar Higgs bosons.**
18. There are fundamental fermions other than those identified in the Standard Model below the GUT scale.**
19. There are fundamental bosons not identified in the Standard Model below the GUT scale, other than gravitons and possibly one or two bosons related to neutrino mass and/or neutrino oscillation.**
20. CPT symmetry is violated under any circumstances.
21. There are any interactions involving massless carrier bosons that show CP violation.
22. There are any massless particles that interact via the weak force.
23. There are any massive particles that do not interact via the weak force.
24. There are any neutrinos with zero mass.
25. There are massless fundamental fermions.
26. Thera are leptoquarks.
27. There are tachyons.
28. Negative mass exists.
29. There are more than four dimensions of space-time, either large or tiny.***
30. Mass-energy conversation is violated locally at t=0 plus an infinitesimal amount.
31. The topology of space-time is sufficiently warped or non-local to give rise to traversable worm-holes.****
31. Fundamental physical constants vary in space-time for any reason other than energy-scale.
32. Gravitons that have non-zero rest mass exist.
33. The actual physical value of muon g-2 differs from the correctly calculated value under the Standard Model.
34. The neutron lifetime discrepancy is anything other than measurement error or a theoretical error.
35. The muonic hydrogen radius discrepancy is anything other than measurement error or a theoretical error.
37. The CKM matrix has more than four parameters or does not imply percentages that add to 100%.
38. It is possible for anything resembling life as we know it to enter a black hole without dying.
39. The observed Higgs boson has properties different from those that the Standard Model Higgs boson is predicted to have at its experimentally observed mass.**
40. Gravity behaves exactly as predicted in classical General Relativity (as applied today) in all circumstances without modification even in the extremely weak field limit.

I doubt that any of the following (which are common components of beyond the Standard Model theories) are true (some of which are redundant), but far less intensely:

1. It is impossible to derive any of the experimentally determined physical constants of the Standard Model from a deeper theory.
2. The sum of the square of the fundamental particle masses does not when evaluated at some proper energy scale such as pole masses or the Higgs vev, equal the square of the Higgs vev.
3. The probability of a transition from a first generation fermion to a third generation fermion in the CKM matrix is ever not equal to product of the probability of a transition from a first generation fermion to a possible second generation fermion and to the probability of a transition from that possible second generation fermion to a third generation fermion.
4. There are violations of lepton universality significantly greater than the square root of the ratio of the neutrino masses to the charged lepton masses.
5. Koide's rule for charged leptons is inaccurate by significantly greater than the square root of the ratio of the neutrino masses to the charged lepton masses.
6. The reason that Koide's rule works for charged leptons cannot be generalized in some manner to explain the quark and neutrino masses.
7. The differences in mass between the charged leptons and the neutrinos is unrelated to the relative strengths of the electromagnetic coupling constant and the weak force coupling constant.
8. The neutrinos have an inverse mass hierarchy.
9. The lightest neutrino mass is as large as the difference between the lightest and second lightest neutrino mass.
10. The net electric charge of the universe is non-zero.
11. Sphaleron interactions actually occur physically.
12. There is a multiverse other than an anti-universe at times before the Big Bang.
13. Cosmological inflation occurred.
14. The temperature of the Big Bang was not finite.
15. The temperature of the Big Bang can be exceeded in the universe at latter times.
16. There are (or were) primordial black holes for more than an instant.
17. There are substances in the universe with greater density than the most dense possible neutron star or the smallest possible stellar black hole.
18. Dark energy is a non-Standard Model substance of some kind (other than a gravity modification).
19. Massless gravitons do not exist.
20. Gravitational energy cannot be localized.
21. There are ever violations of mass-energy conservation involving gravity.
22. General relativity correctly models the self-interactions of gravitons.
23. The strong equivalence principle is not violated by an external field effect.
24. Lorenz violation is possible in detectable amounts for long distances (e.g. kilometers or more) in a time period comparable to the age of the universe.
25. Free glueballs (i.e confined composite structures made purely of gluons) exist.

At some point, I may want to make an additional list of the beyond the Standard Model physics theories which I do believe are possible given these constraints. But, not today.

I believe that these principles would be a better and more fruitful guiding force for hypothesis generation in theoretical physics than many of those  those commonly in use today such as (1) "naturalness", (2) the "hierarchy problem", (3) the "strong CP problem", (4) the hypothesis that at at t=0 plus an infinitesimal amount the aggregate baryon number of the universe was zero and the aggregate lepton number of the universe was zero, (5) the anthropic principle, and (6) multiverse reasoning.

Footnotes and Clarifications

* To be clear, I don't claim to have the answer to the source of neutrino mass, I simply think that all of the above statements are not true and that some other mechanism than those set forth is the actual source of neutrino mass.

** This is subject to the caveat that there could be more fundamental fermions or bosons that can only combined to, or interact to give rise to dynamically, the Standard Model particles. For example, I do not rule out the possibility that the Higgs boson is a composite particle made up of a W+ boson, a W- boson, a Z boson and a photon, or that all Standard Model fundamental particles are vibration modes of a fundamental string.

*** Dimensionality might, however, be an emergent property of space-time and not fundamental.

**** I do not rule out the possibility that there are microscopic non-local connections at approximately the Planck length scale that could connection to profoundly distant points in space-time that are not traversable.

Another Modified Gravity Paper

This paper has interesting things to say, but thinking about gravity modification in terms of a particular radial distance, rather than in terms of a particular gravitational field strength seems to miss one of the core insights about any gravitational modification that must follow from MOND's phenomenological successes. I've listed the references below the fold as it is a quite nice list of papers on gravitational approaches to dark matter phenomena.

Galactic dynamics and long-range quantum gravity

Matteo Tuveri, Mariano Cadoni

(Submitted on 26 Apr 2019)

We explore in a systematic way the possibility that long-range quantum gravity effects could play a role at galactic scales and could be responsible for the phenomenology commonly attributed to dark matter. We argue that the presence of baryonic matter breaks the scale symmetry of the de Sitter (dS) spacetime generating an IR scale r0, corresponding to the scale at which the typical dark matter effects we observe in galaxies arise. It also generates a huge number of bosonic excitations with wavelength larger than the size of the cosmological horizon and in thermal equilibrium with dS spacetime. We show that for r≳r0 these excitations produce a new component for the radial acceleration of stars in galaxies which leads to the result found by McGaugh {\sl et al.} by fitting a large amount of observational data and with the MOND theory. We also propose a generalized thermal equivalence principle and use it to give another independent derivation of our result. Finally, we show that our result can be also derived as the weak field limit of Einstein's general relativity sourced by an anisotropic fluid.

Comments:	20 pages, no figures
Subjects:	General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); Other Condensed Matter (cond-mat.other); Superconductivity (cond-mat.supr-con); High Energy Physics - Theory (hep-th)
Cite as:	arXiv:1904.11835 [gr-qc]
	(or arXiv:1904.11835v1 [gr-qc] for this version)

More Archaic Admixture In Africa

A new paper (open access) continues the ongoing effort to ferret out the nature of the archaic "ghost populations" that admixed with modern humans in Africa, sometimes relatively recently as evolutionary history goes. The archaic introgression percentages inferred statistically are on the same order of magnitude as Neanderthal and Denisovan introgression into the Eurasian populations where this introgression is found.

Razib discusses this paper and another one that I blogged a few days ago at Gene Expression. He notes that the genetic case for archaic admixture in Africa is solid but that the details should be viewed with some skepticism in light of the methods used to discern it. It would be interesting to see if the details of the new paper's model could be replicated from another different set of 21 individuals from the same 15 reference populations using the same methods.

The paper is as follows (with a quick and dirty cut and paste with emphasis added in the abstract):

Whole-genome sequence analysis of a Pan African set of samples reveals archaic gene flow from an extinct basal population of modern humans into sub-Saharan populations

• Belen Lorente-Galdos†,
• Oscar Lao†,
• Gerard Serra-Vidal†,
• Gabriel Santpere,
• Lukas F. K. Kuderna,
• Lara R. Arauna,
• Karima Fadhlaoui-Zid,
• Ville N. Pimenoff,
• Himla Soodyall,
• Pierre Zalloua,
• Tomas Marques-Bonet and
• David ComasEmail authorView ORCID ID profile

†Contributed equally

Genome Biology201920:77

https://doi.org/10.1186/s13059-019-1684-5

©  The Author(s). 2019

• Received: 17 August 2018
• Accepted: 28 March 2019
• Published: 26 April 2019

Abstract

Background

Population demography and gene flow among African groups, as well as the putative archaic introgression of ancient hominins, have been poorly explored at the genome level.

Results

Here, we examine 15 African populations covering all major continental linguistic groups, ecosystems, and lifestyles within Africa through analysis of whole-genome sequence data of 21 individuals sequenced at deep coverage. We observe a remarkable correlation among genetic diversity and geographic distance, with the hunter-gatherer groups being more genetically differentiated and having larger effective population sizes throughout most modern-human history. Admixture signals are found between neighbor populations from both hunter-gatherer and agriculturalists groups, whereas North African individuals are closely related to Eurasian populations. Regarding archaic gene flow, we test six complex demographic models that consider recent admixture as well as archaic introgression. We identify the fingerprint of an archaic introgression event in the sub-Saharan populations included in the models (~ 4.0% in Khoisan, ~ 4.3% in Mbuti Pygmies, and ~ 5.8% in Mandenka) from an early divergent and currently extinct ghost modern human lineage.

Conclusion

The present study represents an in-depth genomic analysis of a Pan African set of individuals, which emphasizes their complex relationships and demographic history at population level.

Motivic Gravity

One of my regular readers, M.D. Sheppeard, has published a fascinating new paper in the Journal of Physics, entitled "Constraining The Standard Model In Motivic Quantum Gravity", which is open access. The abstract is as follows:

A physical approach to a category of motives must account for the emergent nature of spacetime, where real and complex numbers play a secondary role to discrete operations in quantum computation. In quantum logic, the cardinality of a set is initially replaced by a dimension of a linear space, making contact with the increasing dimensions in an operad. The operad of associahedra governs tree level scattering, and is closely related to the permutohedra and cube tiles, where cube vertices can encode components of a spinor in higher dimensional octonionic approaches. A study of rest mass generation begins with the cosmological infrared scale, set by the neutrino masses, and its related see-saw mechanism. We employ the anyonic ribbon spectrum for Standard Model states, and consider its relation to magic star algebras, giving a context for the Koide rest mass phenomenology of charged leptons and quarks.

At a "forest" level, the paper looks at how select structures in abstract algebra can yield a framework in which the particles of the Standard Model fit nicely. It isn't so much about motivic quantum gravity itself, as it is about how the logic of motivic quantum gravity can be generalized to provide a new perspective on Standard Model physics.

The article isn't very computationally intense, but does require a firm and broad understanding of abstract algebra concepts and terminology, as well as some familiarity with the prior works referenced in the paper. This is a paper that builds on prior work that is prerequisite to understanding it, rather than being an introductory review of the theory.

The motivic descriptor basically (and other feel free to correct me if I haven't gotten it quite right for an educated layman's level description) means starting with amplitudes and then examining those amplitudes to determine the nature of space-time in an emergent manner. This logic is then applied on a more general basis to the issues addressed in this paper. 

The paper also builds to a significant extent on prior work by Brannen and Koide regarding the relationships between the masses of the Standard Model particles.

Mitchell Porter discusses the paper further at the Physics Forums. He explains an important feature of the type of amplitude analysis done in the paper. "[P]olytope methods obtain the scattering amplitudes through constructions that don't involve space-time", rather than using the Feynman path integral approach which has a more obvious connection to a physical description of what is going on in the calculations, at the cost of being much more computationally intense.

New Study Pushes Back Time Depth Of Human Family Tree In Africa

The new paper dates the deepest split of populations in the human family tree at 160,000 years compared to earlier estimates closer to 70,000 years. But the broad outlines of the study's conclusions confirms prior research. 

Background 

Africa is the origin of modern humans within the past 300 thousand years. To infer the complex demographic history of African populations and adaptation to diverse environments, we sequenced the genomes of 92 individuals from 44 indigenous African populations. 

Results 

Genetic structure analyses indicate that among Africans, genetic ancestry is largely partitioned by geography and language, though we observe mixed ancestry in many individuals, consistent with both short- and long-range migration events followed by admixture. Phylogenetic analysis indicates that the San genetic lineage is basal to all modern human lineages. The San and Niger-Congo, Afroasiatic, and Nilo-Saharan lineages were substantially diverged by 160 kya (thousand years ago). In contrast, the San and Central African rainforest hunter-gatherer (CRHG), Hadza hunter-gatherer, and Sandawe hunter-gatherer lineages were diverged by ~ 120–100 kya. Niger-Congo, Nilo-Saharan, and Afroasiatic lineages diverged more recently by ~ 54–16 kya. Eastern and western CRHG lineages diverged by ~ 50–31 kya, and the western CRHG lineages diverged by ~ 18–12 kya. The San and CRHG populations maintained the largest effective population size compared to other populations prior to 60 kya. Further, we observed signatures of positive selection at genes involved in muscle development, bone synthesis, reproduction, immune function, energy metabolism, and cell signaling, which may contribute to local adaptation of African populations. 

Conclusions 

We observe high levels of genomic variation between ethnically diverse Africans which is largely correlated with geography and language. Our study indicates ancient population substructure and local adaptation of Africans.

Shaohua Fan, et al., "African evolutionary history inferred from whole genome sequence data of 44 indigenous African populations", 20 Genome Biology 82 (April 26, 2019). 

https://doi.org/10.1186/s13059-019-1679-2

Up-Down Asymmetry In Charmed Baryon Decays?

Baryons (see below for background) tend to be less quirky than mesons, with fewer exceptions to the plain vanilla general rules regarding what types are possible and how they decay. But charmed baryons decaying to form baryons and mesons where a down quark replaces a charm quark have now been observed to have one quirk.

While it isn't inherently obvious on the face of the Standard Model physical laws, theoretical calculations to date have predicted based upon the Standard Model's physical laws, have predicted that there should be no detectible asymmetry between up type and down type quarks in these decays. But, in fact, an asymmetry has been observed in at least two different experiments in the decays of charmed baryons with numerical values that are consistent with an absolute value of a 1.00 when an asymmetry of zero is expected. 

One of the prior data experimental values is inconsistent with zero at the 2.94 sigma level. Another is inconsistent with zero at the 8.55 sigma level (a significance that would normally count as the discovery of "new physics"). This study looked at twelve different kinds of charmed baryon decays where results consistent with 1.00 at the one sigma level were observed which were inconsistent with an asymmetry of zero at 6.14 sigma or more in each case.

The main reason that these results aren't making headlines, in addition to the fact that they involve a rather obscure and hard to understand property of baryon decays in the Standard Model, is not that there is really any question about what the experimental results show or the statistical significance of those results. Instead, the concern that has boded caution is that the theoretical predictions in the literature might be flaws in some way.

But, these results are notable, because if the theoretical predictions in the literature are correct, then these experiments are observing beyond the Standard Model physics that have to be explained with some tweak to the Standard Model regarding differences in a novel property other than mass and electric charge between the up type quarks and the down type quarks, that had previously never been observed or predicted (probably without the need for a new particle or force).

Charmed Baryon Weak Decays with Decuplet Baryon and SU(3) Flavor Symmetry

Chao-Qiang Geng, Chia-Wei Liu, Tien-Hsueh Tsai, Yao Yu

(Submitted on 25 Apr 2019)

We study the branching ratios and up-down asymmetries in the charmed baryon weak decays of Bc→BDM with Bc(D) with Bc(D) anti-triplet charmed (decuplet) baryon and M pseudo-scalar meson states based on the flavor symmetry of SU(3)F. We propose equal and physical-mass schemes for the hadronic states to deal with the large variations of the decuplet baryon momenta in the decays in order to fit with the current experimental data. We find that our fitting results of (Bc→BDM) are consistent with the current experimental data in both schemes, while the up-down asymmetries in all decays are found to be sizable, consistent with the current experimental data, but different from zero predicted in the literature. We also examine the the processes of Ξ0c→Σ′0KS/KL and derive the asymmetry between the KL/KS modes being a constant.

Comments:	13 pages, no figure
Subjects:	High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
Cite as:	arXiv:1904.11271 [hep-ph]
	(or arXiv:1904.11271v1 [hep-ph] for this version)

The conclusion of the paper explains that:

We have studied the decay branching ratios and up-down asymmetries in the charmed baryon weak decays of Bc → BDM based on the flavor symmetry of SU(3)F . It is interesting to emphasize that these Bc decays with the decuplet spin-3/2 baryon receive only nonfactorizable contributions. We have shown that our fitting results for B(Bc → BDM) are consistent with the current experimental data in both pm and em schemes. In particular, the em scheme leads to a much smaller number for the χ 2 fit than the pm one, resulting in that the predicted values of B(Bc → BDM) in the em scheme contain much less uncertainties than those in the pm one. We have demonstrated that the isospin relations for the decay branching ratios in Eq. (18) are scheme- and model-independent. It is also interesting to note that the vanishing rates for the Cabibbo allowed decays of Ξ+ c → Σ ′+K¯ 0 and Ξ+ c → Ξ ′0π + have not been supported by the experimental data yet. 

For the up-down asymmetries, we have found that they are sizable, which are different from the prediction of zero due to the vanishing D-wave contributions in the literature. In particular, we have obtained that α(Bc → BDM) = −1.00+0.34 −0 for all decay modes in the em scheme, while they range from −1 to −0.42 at 1σ level in the pm scheme, consistent with the current only available data of αex(Λ+ c → Ξ ′0K+) = −1.00 ± 0.34 [11] for the up-down asymmetry. To justify the SU(3)F approach, we have proposed to search for α(Λ+ c → ∆++K−), which is predicted to be −0.86+0.44 −0.14, in the future experiments, as the the decay has the largest branching rate among Bc → BDM. 

In addition, we have examined the processes of Ξ0 c → Σ ′0KS/KL, which contain both Cabibbo allowed and doubly-suppressed contributions. We have predicted the KL − KS asymmetry of R(Ξ0 c → Σ ′0KS/KL) is −0.106, which depends on neither model/scheme nor the data fitting. Clearly, this asymmetry is a clean result in the SU(3)F approach, which should be tested by the experiments.

Background Regarding Observed Baryons 

So far, 24 of the 40 possible spin-1/2 baryons and 19 of the 35 possible spin-3/2 baryons have been observed. Sixteen spin-1/2 baryons and sixteen spin-3/2 baryons have yet to be observed. All of the baryons that have not yet been observed have at least one bottom quark but not more than one charm quark (24), at least two charm quarks (6), or a bottom quark and two charm quarks (2).

We have observed ten different single bottom baryons (both kinds of bottom lambda, four of the six kinds of bottom sigma, three of the four kinds of bottom Xi and one of the two kinds of bottom Omega), and one kind of double charmed Xi.

We have not yet observed any double charmed bottom, double bottom, triple charmed, or triple bottom baryons.

This pattern of discovery is to be expected, because baryons with heavier quarks are created only in higher energy collisions and are rare even then.

The least massive observed baryon, and the only one that is stable in all circumstances is the proton which has a rest mass of 938.272046(21) MeV. Neutrons (which are the second lightest observed baryons) are stable when bound in a nucleus, but have a mean lifetime of a bit less than fifteen minutes as free particles.

As a result of their extremely short mean lifetimes and the high energies needed to create new baryons of these types, baryons other than the proton and neutron are almost never observed outside particle colliders.

The lightest observed baryon other than the nucleons is the electrically neutral lambda with a mass of 

1,115.683±0.006 MeV. The most massive observed baryon is the spin-3/2, electrically neutral bottom Xi at 5,945.5±0.8±2.2 eV. In theory, the most massive possible three quark baryon would be the triple bottom Omega with an expected mass on the order of 14 to 15 GeV.

The longest lived observed baryon with spin-3/2 is the Omega with a mean lifetime of (8.21±0.11)×10⁻¹¹seconds. The spin-3/2, electrically neutral bottom Xi is the second longest mean lifetime for an observed spin-3/2 baryon of (3.1±2.5)×10⁻²² seconds. The most short lived observed spin-3/2 baryon, the Delta (all four types) has a mean lifetime of (5.63±0.14)×10⁻²⁴ seconds.

The longest lived observed baryon with spin-1/2 other than the nucleons is the electrically neutral Xi with a mean lifetime of (2.90±0.09)×10⁻¹⁰ seconds. The most short lived observed spin-1/2 baryon, the single positively charged charmed sigma has a mean lifetime of >1.43×10⁻²² seconds. 

No three quark baryons not predicted by the Standard Model have been observed.

Baryon Nomenclature

A baryon is a composite particle with either three valence quarks, or three valence anti-quarks. The most common types of baryons, by far, which are of the former type, are protons and neutrons.

Baryons have total angular momentum a.k.a. spin a.k.a. "J" of either 1/2 or 3/2. For each type of baryon made of quarks there is exactly one anti-baryon made of the corresponding anti-quarks. 

In all there are 75 possible types of baryons with three valence quarks (40 spin-1/2 and 35 spin-3/2) and 75 corresponding types of possible anti-baryons in their ground state. There are also more massive excited states of baryons with short lifetimes that are not well understood. Pentaquarks are strictly speaking baryons and have five valence quarks, but only a small number of not entirely certain observations have been made of them and they are not very well characterized yet.

The base name of a baryon is based upon how many quarks that are not up or down quarks are present. If none are present, it is an Omega baryon. If only one is present it is a Xi baryon. If two are present it is usually called a Sigma baryon unless the up or down quarks present have opposite spins, in which case it is called a Lambda baryon. If all three quarks are up or down quarks and it has spin-3/2, it is a Delta baryon. If all three quarks are up or down and it has spin-1/2, it is called a proton or a neutron (a.k.a. Nucleons). Anomalously a bottom Xi baryon is also known as a "Cascade B" baryon.

If a baryon has any bottom quarks the prefix bottom is added if there is one of them, double bottom is added if there are two of them, and triple bottom is added if there are three of them. If a baryon has any charm quarks, the prefix charmed is added if there is one of them, double charmed is added if there are two of them, and triple charmed is added if there are three of them. If both charm quarks and bottom quarks are present, the charm quark prefix is placed first and the bottom quark prefix is placed second. Symbolically this is indicated with lettered subscripts to right of the symbol.

In the case of the six possible spin-1/2 Xi baryon with three different types of quarks (i.e. a charmed Xi, a bottom Xi or a charmed bottom Xi) where there are two possible configurations with the same quark content, the suffix "prime" is added to the configuration that is expected to have the higher mass. (A Lambda baryon would have been the unprimed version of the corresponding Sigma baryon which would have been the primed version, if there wasn't a separate Lambda designation). A "prime" baryon is indicated symbolically with a ' mark in the superscript between the symbol and its electric charge.

The name also does not distinguish between spin-1/2 and spin-3/2 baryons with the same quark content, but a "*" in front of the electric charge (if any) denotes spin-3/2 baryons.

These names do not, themselves, reveal where the up or down quarks present are up quarks or down quarks. This is revealed symbolically, however, by noting the electric charge of the baryon for baryons that can have more than one electric charge which will be ++, +, 0, - or --. The charge is indicated in superscripts to the right of the symbol.

Excited states are indicated with the symbol for the ground state (or N for nucleons) followed by the mass in MeV rounded to the nearest integer in parenthesis.