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In particle physics, a hadron is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the electric force. Most of the mass of ordinary matter comes from two hadrons: the proton and the neutron, while most of the mass of the protons and neutrons is in turn due to the binding energy of their constituent quarks, due to the strong force.
The omega baryons are a family of subatomic hadron particles that are represented by the symbol
Ω
and are either neutral or have a +2, +1 or −1 elementary charge. They are baryons containing no up or down quarks. Omega baryons containing top quarks are not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s, which is about a twentieth of the timescale for strong interactions, and therefore that they do not form hadrons.
A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them.
In particle physics, the baryon number is a strictly conserved additive quantum number of a system. It is defined as
A tetraquark, in particle physics, is an exotic meson composed of four valence quarks. A tetraquark state has long been suspected to be allowed by quantum chromodynamics, the modern theory of strong interactions. A tetraquark state is an example of an exotic hadron which lies outside the conventional quark model classification. A number of different types of tetraquark have been observed.
Exotic baryons are a type of hadron with half-integer spin, but with a quark content different from the three quarks (qqq) present in conventional baryons. An example would be pentaquarks, consisting of four quarks and one antiquark (qqqqq̅).
The LHCb experiment is one of eight particle physics detector experiments collecting data at the Large Hadron Collider at CERN. LHCb is a specialized b-physics experiment, designed primarily to measure the parameters of CP violation in the interactions of b-hadrons. Such studies can help to explain the matter-antimatter asymmetry of the Universe. The detector is also able to perform measurements of production cross sections, exotic hadron spectroscopy, charm physics and electroweak physics in the forward region. The LHCb collaboration, who built, operate and analyse data from the experiment, is composed of approximately 1260 people from 74 scientific institutes, representing 16 countries. Chris Parkes succeeded on July 1, 2020 as spokesperson for the collaboration to Giovanni Passaleva. The experiment is located at point 8 on the LHC tunnel close to Ferney-Voltaire, France just over the border from Geneva. The (small) MoEDAL experiment shares the same cavern.
Exotic hadrons are subatomic particles composed of quarks and gluons, but which — unlike "well-known" hadrons such as protons, neutrons and mesons — consist of more than three valence quarks. By contrast, "ordinary" hadrons contain just two or three quarks. Hadrons with explicit valence gluon content would also be considered exotic. In theory, there is no limit on the number of quarks in a hadron, as long as the hadron's color charge is white, or color-neutral.
b-tagging is a method of jet flavor tagging used in modern particle physics experiments. It is the identification of jets originating from bottom quarks.
The Xi baryons or cascade particles are a family of subatomic hadron particles which have the symbol Ξ and may have an electric charge of +2 e, +1 e, 0, or −1 e, where e is the elementary charge.
Neutral B meson oscillations are one of the manifestations of the neutral particle oscillation, a fundamental prediction of the Standard Model of particle physics. It is the phenomenon of B mesons changing between their matter and antimatter forms before their decay. The
B
s meson can exist as either a bound state of a strange antiquark and a bottom quark, or a strange quark and bottom antiquark. The oscillations in the neutral B sector are analogous to the phenomena that produce long and short-lived neutral kaons.
The
B
s meson is a meson composed of a bottom antiquark and a strange quark. Its antiparticle is the
B
s meson, composed of a bottom quark and a strange antiquark.
The X(3872) is an exotic meson candidate with a mass of 3871.68 MeV/c2 which does not fit into the quark model because of its quantum numbers. It was first discovered in 2003 by the Belle experiment in Japan and later confirmed by several other experimental collaborations. Several theories have been proposed for its nature, such as a mesonic molecule or a diquark-antidiquark pair (tetraquark).
Z(4430) is a mesonic resonance discovered by the Belle experiment. It has a mass of 4430 MeV/c2. The resonant nature of the peak has been confirmed by the LHCb experiment with a significance of at least 13.9 σ. The particle is charged and is thought to have a quark content of
c
c
d
u
, making it a tetraquark candidate. It has the spin-parity quantum numbers JP = 1+.
In particle physics, B mesons are mesons composed of a bottom antiquark and either an up, down, strange or charm quark. The combination of a bottom antiquark and a top quark is not thought to be possible because of the top quark's short lifetime. The combination of a bottom antiquark and a bottom quark is not a B meson, but rather bottomonium, which is something else entirely.
The D mesons are the lightest particle containing charm quarks. They are often studied to gain knowledge on the weak interaction. The strange D mesons (Ds) were called "F mesons" prior to 1986.
The Y(4140) particle is an electrically neutral exotic hadron candidate that is about 4.4 times heavier than the proton. It was observed at Fermilab and announced on 17 March 2009. This particle is extremely rare and was detected in only 20 of billions of collisions.
XYZ particles, also referred to as XYZ states, are recently discovered heavy mesons whose properties do not appear to fit the standard picture of charmonium and bottomonium states. They are therefore types of exotic meson. The term arises from the names given to some of the first such particles discovered: X(3872), Y(4260) and Zc(3900), although the symbols X and Y have since been deprecated by the Particle Data Group.
The Xi double-charm baryon, denoted as , is a Xi baryon composed of two charm quarks and one up quark.
Sheldon Leslie Stone was a distinguished professor of physics at Syracuse University. He is best known for his work in experimental elementary particle physics, the Large Hadron Collider beauty experiment (LHCb), and B decays. He made significant contributions in the areas of data analysis, LHCb detector design and construction, and phenomenology.
References
- 1 2 3 4 5 Agaev, S.S.; Azizi, K.; Sundu, H. (February 2022). "Newly observed exotic doubly charmed meson ". Nuclear Physics B. 975: 115650. arXiv: 2108.00188 . doi:10.1016/j.nuclphysb.2022.115650.
- 1 2 Aaij, R.; Abdelmotteleb, A. S. W.; Abellán Beteta, C.; Abudinen Gallego, F. J.; Ackernley, T.; Adeva, B.; Adinolfi, M.; Afsharnia, H.; Agapopoulou, C.; Aidala, C. A.; Aiola, S. (2022-06-16). "Observation of an exotic narrow doubly charmed tetraquark". Nature Physics: 1–4. doi:10.1038/s41567-022-01614-y. ISSN 1745-2481.
- ↑ "What to Know About the Newly Discovered Tetraquark at the Large Hadron Collider". Gizmodo. Retrieved 2021-09-27.
- ↑ "Twice the charm: long-lived exotic particle discovered". CERN. Retrieved 2021-09-29.
- ↑ Aaij, R.; Abdelmotteleb, A. S. W.; Beteta, C. Abellán; Gallego, F. J. Abudinen; Ackernley, T.; Adeva, B.; Adinolfi, M.; Afsharnia, H.; Agapopoulou, C.; Aidala, C. A.; Aiola, S. (2022-06-16). "Study of the doubly charmed tetraquark T⁺_cc". Nature Communications. 13 (1): 3351. doi:10.1038/s41467-022-30206-w. ISSN 2041-1723.
- ↑ "LHCb experiment spots extraordinary double charmed tetraquark". Nikhef. Retrieved 2021-09-27.
- ↑ Wood, Charlie (2021-09-27). "'Impossible' Particle Discovery Adds Key Piece to the Strong Force Puzzle". Quanta Magazine. Retrieved 2021-09-27.
- ↑ Turner, Ben (2021-08-05). "New 'doubly charming' particle could help unlock the secrets of how matter is built". livescience.com. Retrieved 2021-09-27.
