B meson

In particle physics, B mesons are mesons composed of a bottom antiquark and either an up (
B+
), down (
B0
), strange (
B0
s
) or charm quark (
B+
c
). 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.

Each B meson has an antiparticle that is composed of a bottom quark and an up (
B
), down (
B0
), strange (
B0
s
) or charm antiquark (
B
c
) respectively.

List of B mesons

B mesons
Particle Symbol Anti-particle Quark
content
Charge Isospin
(I)
Spin and parity
(JP)
Rest mass
(MeV/c2)
S C B' Mean lifetime
(s)
Commonly decays to
B meson
B+

B

u

b
+1 1/2 0 5279.29±0.15 0 0 +1 (1.638±0.004)×10−12 See
B±
decay modes
B meson
B0

B0

d

b
0 1/2 0 5279.61±0.16 0 0 +1 (1.520±0.004)×10−12 See
B0
decay modes
Strange B meson
B0
s

B0
s

s

b
0 0 0 5366.79±0.23 −1 0 +1 (1.510±0.005)×10−12 See
B0
s
decay modes
Charmed B meson
B+
c

B
c

c

b
+1 0 0 6275.1±1.0 0 +1 +1 (0.507±0.009)×10−12 See
B±
c
decay modes


B

B
oscillations

The neutral B mesons,
B0
and
B0
s
, spontaneously transform into their own antiparticles and back. This phenomenon is called flavor oscillation. The existence of neutral B meson oscillations is a fundamental prediction of the Standard Model of particle physics. It has been measured in the
B0

B0
system to be about 0.496 ps−1,[1] and in the
B0
s

B0
s
system to be Δms = 17.77 ± 0.10 (stat) ± 0.07 (syst) ps−1 measured by CDF experiment at Fermilab.[2] A first estimation of the lower and upper limit of the
B0
s

B0
s
system value have been made by the DØ experiment also at Fermilab.[3]

On 25 September 2006, Fermilab announced that they had claimed discovery of previously-only-theorized Bs meson oscillation.[4] According to Fermilab's press release:

This first major discovery of Run 2 continues the tradition of particle physics discoveries at Fermilab, where the bottom (1977) and top (1995) quarks were discovered. Surprisingly, the bizarre behavior of the B_s (pronounced "B sub s") mesons is actually predicted by the Standard Model of fundamental particles and forces. The discovery of this oscillatory behavior is thus another reinforcement of the Standard Model's durability... CDF physicists have previously measured the rate of the matter-antimatter transitions for the B_s meson, which consists of the heavy bottom quark bound by the strong nuclear interaction to a strange antiquark. Now they have achieved the standard for a discovery in the field of particle physics, where the probability for a false observation must be proven to be less than about 5 in 10 million (5/10,000,000). For CDF's result the probability is even smaller, at 8 in 100 million (8/100,000,000).

Ronald Kotulak, writing for the Chicago Tribune, called the particle "bizarre" and stated that the meson "may open the door to a new era of physics" with its proven interactions with the "spooky realm of antimatter".[5]

On 14 May 2010, physicists at the Fermi National Accelerator Laboratory reported that the oscillations decayed into matter 1% more often than into antimatter, which may help explain the abundance of matter over antimatter in the observed Universe.[6] However, more recent results at LHCb with larger data samples have suggested no significant deviation from the Standard Model.[7]

Rare decays

B-mesons are an important probe for exploring quantum chromodynamics.[8] Various uncommon decay paths of the B mesons are sensitive to physics processes outside the standard model. Measuring these rare branching fractions sets limits on new particles. The LHCb experiment has observed and searched for several of these decays such as Bsµ+µ.[9]

On February 21, 2017, the LHCb collaboration announced that the rare decay of a neutral B-meson into two oppositely charged kaons had been observed to a statistical significance of 5σ.[10]

See also

References

  1. ^ http://repository.ubn.ru.nl/bitstream/2066/26242/
  2. ^ Abulencia, A.; et al. (CDF Collaboration) (2006). "Observation of
    B0
    s

    B0
    s
    Oscillations". Physical Review Letters. 97 (24): 242003. arXiv:hep-ex/0609040. Bibcode:2006PhRvL..97x2003A. doi:10.1103/PhysRevLett.97.242003.
  3. ^ Abazov, V. M.; et al. (D0 Collaboration) (2006). "Direct Limits on the B0
    s
    Oscillation Frequency"
    (PDF). Physical Review Letters. 97 (2): 021802. arXiv:hep-ex/0603029. Bibcode:2006PhRvL..97b1802A. doi:10.1103/PhysRevLett.97.021802.
  4. ^ "Fermilab's CDF scientists make it official: They have discovered the quick-change behavior of the B-sub-s meson, which switches between matter and antimatter 3 trillion times a second" (Press release). Fermilab. 25 September 2006. Retrieved 8 December 2007.
  5. ^ Kotulak, R. (26 September 2006). "Antimatter discovery could alter physics: Particle tracked between real world, spooky realm". Deseret News. Archived from the original on 29 November 2007. Retrieved 8 December 2007.
  6. ^ Overbye, D. (17 May 2010). "From Fermilab, a New Clue to Explain Human Existence?". The New York Times. Retrieved 26 December 2016.
  7. ^ Timmer, J. (29 August 2011). "LHCb detector causes trouble for supersymmetry theory". Ars Technica. Retrieved 26 December 2012.
  8. ^ CMS Collaboration; LHCb Collaboration (4 June 2015). "Observation of the rare B0
    s
    →µ+µ decay from the combined analysis of CMS and LHCb data"
    . Nature. 522 (7554): 68–72. arXiv:1411.4413. Bibcode:2015Natur.522...68C. doi:10.1038/nature14474. PMID 26047778.
  9. ^ Aaij, R.; Beteta, C. Abellán; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J. (16 October 2015). "Search for the rare decays B0→J/ψγ and B0
    s
    →J/ψγ". Physical Review D. 92 (11). arXiv:1510.04866. Bibcode:2015PhRvD..92k2002A. doi:10.1103/PhysRevD.92.112002.
  10. ^ Aaij, R.; et al. (21 February 2017). "Observation of the Annihilation Decay Mode B0→K+K−". Physical Review Letters. 118 (8). Bibcode:2017PhRvL.118h1801A. doi:10.1103/PhysRevLett.118.081801.

External links

Anthony Ichiro Sanda

Anthony Ichiro Sanda (三田 一郎, Sanda Ichirō, born March 4, 1944) is a Japanese-American particle physicist. Along with Ikaros Bigi, he was awarded the 2004 Sakurai Prize for his work on CP violation and B meson decays.

B-factory

In particle physics, a B-factory, or sometimes a beauty factory, is a particle collider experiment designed to produce and detect a large number of B mesons so that their properties and behaviour can be measured with small statistical uncertainty. Tauons and D mesons are also copiously produced at B-factories,

Two B-factories were designed and built in the 1990s. They are both based on electron-positron colliders with the centre of mass energy tuned to the ϒ(4S) resonance peak, which is just above the threshold for decay into two B mesons (both experiments took smaller data samples at different centre of mass energies). The Belle experiment at the KEKB collider in Tsukuba, Japan, and the BaBar experiment at the PEP-II collider at SLAC laboratory in California, United States, completed data collection in 2010 and 2008, respectively.The B-factories yielded a rich harvest of results, including the first observation of CP violation outside of the kaon system, measurements of the CKM parameters |Vub| and |Vcb|, measurements of purely leptonic B meson decays and searches for new Physics.

Proposals for next-generation B-factories include the canceled SuperB designed to be built in Frascati near Rome in Italy, and Belle II, an upgrade to Belle, which will begin operations in 2018.

B0

B0 may refer to:

B₀, a net magnetisation vector in medical imaging

B0 star, a subclass of B-class stars

Pininfarina B0, an electric car

A paper size

The neutral B meson in particle physics

B-0 : a code name for the FLOW-MATIC compiler

IATA code for La Compagnie, a French airline

BTeV experiment

The BTeV experiment — for B meson TeV (teraelectronvolt) — was an experiment in high-energy particle physics designed to challenge the Standard Model explanation of CP violation, mixing and rare decays of bottom and charm quark states. The Standard Model has been the baseline particle physics theory for several decades and BTeV aimed to find out what lies beyond the Standard Model. In doing so, the BTeV results could have contributed to shed light on phenomena associated with the early universe such as why the universe is made up of matter and not anti-matter.

The BTeV Collaboration was a group of about 170 physicists drawn from more than 30 universities and physics institutes from Belarus, Canada, China, Italy, Russia, and the United States of America. The BTeV experiment was designed to utilize the Tevatron proton-antiproton collider at the Fermi National Accelerator Laboratory, located in the far west suburbs of Chicago, Illinois in the USA. The experiment was scheduled to start in 2006, followed by commissioning in 2008, and data-taking in 2009.

The BTeV Project was terminated by the United States Department of Energy on 2005-02-07 after being removed from the President's Budget for the 2006 fiscal year.

BaBar experiment

The BaBar experiment, or simply BaBar, is an international collaboration of more than 500 physicists and engineers studying the subatomic world at energies of approximately ten times the rest mass of a proton (~10 GeV). Its design was motivated by the investigation of Charge Parity violation. BaBar is located at the SLAC National Accelerator Laboratory, which is operated by Stanford University for the Department of Energy in California.

Belle experiment

The Belle experiment was a particle physics experiment conducted by the Belle Collaboration, an international collaboration of more than 400 physicists and engineers, at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan. The experiment ran from 1999 to 2010.The Belle detector was located at the collision point of the asymmetric-energy electron–positron collider, KEKB. Belle at KEKB together with the BaBar experiment at the PEP-II accelerator at SLAC were known as the B-factories as they collided electrons with positrons at the center-of-momentum energy equal to the mass of the ϒ(4S) resonance which decays to pairs of B mesons.

The Belle detector was a hermetic multilayer particle detector with large solid angle coverage, vertex location with precision on the order of tens of micrometres (provided by a silicon vertex detector), good distinction between pions and kaons in the momenta range from 100 MeV/c to few GeV/c (provided by a Cherenkov detector), and a few-percent precision electromagnetic calorimeter (made of CsI(Tl) scintillating crystals).

The Belle II experiment is an upgrade of Belle that was approved in June 2010. It is currently being commissioned, and is anticipated to start operation in 2018. Belle II is located at SuperKEKB (an upgraded KEKB accelerator) which is intended to provide a factor 40 larger integrated luminosity.

Bottom eta meson

The bottom eta meson (ηb) or eta-b meson is a flavourless meson formed from a bottom quark and its antiparticle. It was first observed by the BaBar experiment at SLAC in 2008, and is the lightest particle containing a bottom and anti-bottom quark.

Bottom quark

The bottom quark or b quark, also known as the beauty quark, is a third-generation quark with a charge of −1/3 e.

All quarks are described in a similar way by electroweak and quantum chromodynamics, but the bottom quark has exceptionally low rates of transition to lower-mass quarks. The bottom quark is also notable because it is a product in almost all top quark decays, and is a frequent decay product of the Higgs boson.

B–Bbar oscillation

Neutral B meson oscillations (or B–B oscillations) is 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 (or oscillating) between their matter and antimatter forms before their decay. The Bs 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 produces long and short-lived neutral kaons.

Bs–Bs mixing was observed by the CDF experiment at Fermilab in 2006 and by LHCb at CERN in 2011.

CP violation

In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge conjugation symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C symmetry) while its spatial coordinates are inverted ("mirror" or P symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

It plays an important role both in the attempts of cosmology to explain the dominance of matter over antimatter in the present Universe, and in the study of weak interactions in particle physics.

CUSB

CUSB (Columbia University-Stony Brook) was a particle detector at the Cornell Electron Storage Ring. CUSB, along with CLEO, discovered both the Υ(3S) and Υ(4S) meson resonances.

They also produced studies of the photon transitions between the Upsilon states and B meson decays.

David George Hitlin

David George Hitlin (born 15 April 1942) is a particle physicist at the California Institute of Technology. He was educated at Columbia University. In 2016 he was awarded the Panofsky Prize by the American Physical Society "for leadership in the BABAR and Belle experiments, which established the violation of CP symmetry in B meson decay, and furthered our understanding of quark mixing and quantum chromodynamics." His co-awardees were Drs. Jonathan Dorfan, Fumihiko Takasaki, and Stephen L. Olsen.

KEKB (accelerator)

KEKB is a particle accelerator used in the Belle experiment to study CP violation. KEKB is located at the KEK (High Energy Accelerator Research Organisation) in Tsukuba, Ibaraki Prefecture, Japan.

KEKB It is called a B-factory for its copious production of B-mesons which provide a golden mode to study and measure the CP violation due to its property of decaying into other lighter mesons. KEKB is basically an asymmetric electron–positron collider, with electrons having the energy of 8 GeV and positrons having the energy of 3.5 GeV, giving 10.58 GeV centre-of-mass energy, which is equal to the mass of the Υ(4S) meson.

There are basically two rings for accelerating electrons and positrons. The ring for electrons, having energy of 8 GeV, is called the high-energy ring (HER), while the ring for positrons, having energy of 3.5 GeV, is called low-energy ring (LER). The HER and LER are constructed side-by-side in the tunnel, which has been excavated already in the past for the former TRISTAN accelerator. TRISTAN was the first site to confirm vacuum polarization around an electron. The RF cavities in the HER use superconducting RF (SRF) technology, whereas the RF cavities in the LER use a normal conducting design denoted ARES. The circumference of each ring is 3016 m, having four straight sections. In the KEKB, there is only one interaction point in the "Tsukuba area", where the Belle experiment is located. The other areas (called "Fuji", "Nikko" and "Oho") are currently not actively used by an experiment.

Since the energy of the electrons and positrons is asymmetric, the B meson pairs are created with a Lorentz boost βγ of 0.425, allowing measurements of the B meson decay times via the distance from the (known) collision point.

KEKB's leading finite crossing angle interaction design provides its high luminosity. In the last upgrade, KEKB installed crab cavities on each of its accelerating beams to rotate the bunches of accelerating electrons or positrons, hoping to further increase its luminosity. However, the improvement is not clear and currently under tuning. KEKB is still the world's highest luminosity machine. Its latest world record (in June 2009) is of more than 2.11×1034 cm−2s−1.

LHCb experiment

The LHCb (Large Hadron Collider beauty) experiment is one of seven 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 (heavy particles containing a bottom quark). 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. As of 2017, the spokesperson for the collaboration is 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.

List of mesons

This list is of all known and predicted scalar, pseudoscalar and vector mesons. See list of particles for a more detailed list of particles found in particle physics.This article contains a list of mesons, unstable subatomic particles composed of one quark and one antiquark. They are part of the hadron particle family – particles made of quarks. The other members of the hadron family are the baryons – subatomic particles composed of three quarks. The main difference between mesons and baryons is that mesons have integer spin (thus are bosons) while baryons are fermions (half-integer spin). Because mesons are bosons, the Pauli exclusion principle does not apply to them. Because of this, they can act as force mediating particles on short distances, and thus play a part in processes such as the nuclear interaction.

Since mesons are composed of quarks, they participate in both the weak and strong interactions. Mesons with net electric charge also participate in the electromagnetic interaction. They are classified according to their quark content, total angular momentum, parity, and various other properties such as C-parity and G-parity. While no meson is stable, those of lower mass are nonetheless more stable than the most massive mesons, and are easier to observe and study in particle accelerators or in cosmic ray experiments. They are also typically less massive than baryons, meaning that they are more easily produced in experiments, and will exhibit higher-energy phenomena sooner than baryons would. For example, the charm quark was first seen in the J/Psi meson (J/ψ) in 1974, and the bottom quark in the upsilon meson (ϒ) in 1977.Each meson has a corresponding antiparticle (antimeson) where quarks are replaced by their corresponding antiquarks and vice versa. For example, a positive pion (π+) is made of one up quark and one down antiquark; and its corresponding antiparticle, the negative pion (π−), is made of one up antiquark and one down quark. Some experiments show the evidence of tetraquarks – "exotic" mesons made of two quarks and two antiquarks, but the particle physics community as a whole does not view their existence as likely, although still possible.The symbols encountered in these lists are: I (isospin), J (total angular momentum), P (parity), C (C-parity), G (G-parity), u (up quark), d (down quark), s (strange quark), c (charm quark), b (bottom quark), Q (charge), B (baryon number), S (strangeness), C (charm), and B′ (bottomness), as well as a wide array of subatomic particles (hover for name).

Meson

In particle physics, mesons ( or ) are hadronic subatomic particles composed of one quark and one antiquark, bound together by strong interactions. Because mesons are composed of quark subparticles, they have physical size, notably a diameter of roughly one femtometer, which is about 1.2 times the size of a proton or neutron. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond. Charged mesons decay (sometimes through mediating particles) to form electrons and neutrinos. Uncharged mesons may decay to photons. Both of these decays imply that color is no longer a property of the byproducts.

Outside the nucleus, mesons appear in nature only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays (high-energy protons and neutrons) and ordinary matter. Mesons are also frequently produced artificially in cyclotron in the collisions of protons, antiprotons, or other particles.

Mesons are the associated quantum-field particles that transmit the nuclear force between hadrons that pull those together into a nucleus. Their effect is analogous to photons that are the force carriers that transmit the electromagnetic force of attraction between oppositely charged protons and electrons that allow individual atoms to exist, and further, to pull atoms together into molecules. Higher energy (more massive) mesons were created momentarily in the Big Bang, but are not thought to play a role in nature today. However, such heavy mesons are regularly created in particle accelerator experiments, in order to understand the nature of the heavier types of quark that compose the heavier mesons.

Mesons are part of the hadron particle family, and are defined simply as particles composed of an even number of quarks. The other members of the hadron family are the baryons: subatomic particles composed of odd numbers of valence quarks (at least 3), and some experiments show evidence of exotic mesons, which do not have the conventional valence quark content of two quarks (one quark and one antiquark), but 4 or more.

Because quarks have a spin of ​1⁄2, the difference in quark number between mesons and baryons results in conventional two-quark mesons being bosons, whereas baryons are fermions.

Each type of meson has a corresponding antiparticle (antimeson) in which quarks are replaced by their corresponding antiquarks and vice versa. For example, a positive pion (π+) is made of one up quark and one down antiquark; and its corresponding antiparticle, the negative pion (π−), is made of one up antiquark and one down quark.

Because mesons are composed of quarks, they participate in both the weak and strong interactions. Mesons with net electric charge also participate in the electromagnetic interaction. Mesons are classified according to their quark content, total angular momentum, parity and various other properties, such as C-parity and G-parity. Although no meson is stable, those of lower mass are nonetheless more stable than the more massive, and hence are easier to observe and study in particle accelerators or in cosmic ray experiments. Mesons are also typically less massive than baryons, meaning that they are more easily produced in experiments, and thus exhibit certain higher-energy phenomena more readily than do baryons. For example, the charm quark was first seen in the J/Psi meson (J/ψ) in 1974, and the bottom quark in the upsilon meson (ϒ) in 1977.

Piermaria Oddone

Piermaria J Oddone (born March 26, 1944 in Arequipa, Peru) is a Peruvian-American particle physicist.

Oddone earned his bachelor's degree in Physics at the Massachusetts Institute of Technology in 1965 and a PhD in Physics from Princeton University in 1970.

From 1972, Oddone worked at the US Department of Energy’s Lawrence Berkeley National Laboratory. In 1987 he was appointed Director of the Physics Division at Berkeley Lab, and later became the Laboratory Deputy Director for scientific programs.

He was appointed director of Fermi National Accelerator Laboratory (Fermilab) and took up office on 1 July 2005.Oddone received the 2005 Panofsky Prize in Experimental Particle Physics for the invention of the Asymmetric B-Factory to carry out precision measurements of CP violation in B-meson decays.In September 2012, Oddone announced he would retire on July 1, 2013, after 8 years serving as lab director.

Sookyung Choi

SooKyung Choi is a South Korean particle physicist at Gyeongsang National University. She is part of the Belle experiment and was the first to observe the X(3872) meson in 2003. She won the 2017 Ho-Am Prize in Science.

Strange B meson

The Bs meson is a meson composed of a bottom antiquark and a strange quark. Its antiparticle is the Bs meson, composed of a bottom quark and a strange antiquark.

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