{{Short description|Meson that oscillates between matter and antimatter}} {{Technical|date=September 2010}}
{{Infobox particle | name = {{Subatomic particle|Strange B}} meson | image = Quark structure strange B meson.svg | caption = The quark structure of the strange B meson. The color assignment of individual quarks is arbitrary, but the net color charge must be zero. Forces between quarks are mediated by gluons. | num_types = | composition = {{Subatomic particle|bottom antiquark|link=yes}}{{Subatomic particle|Strange quark|link=yes}} | statistics = Bosonic | group = Mesons | interaction = Strong, Weak, Gravitational, Electromagnetic | antiparticle = {{Subatomic particle|Strange antib}} ({{Subatomic particle|bottom quark|link=yes}}{{Subatomic particle|Strange antiquark|link=yes}}) | status = | theorized = | discovered = | symbol = | mass = {{val|5366.3|0.6|ul=MeV/c2}} | mean_lifetime = {{val|1.470| 0.027|-0.026|e=-12|u=s}} | decay_particle = [http://pdg.lbl.gov/2008/tables/rpp2008-tab-mesons-bottom-strange.pdf See {{Subatomic particle|Strange B0}} decay modes] | electric_charge = 0 e | spin = 0 | strangeness = -1 | charm = | bottomness = +1 | topness = | isospin = 0 | hypercharge = | parity = -1 | c_parity = }}The '''{{Subatomic particle|Strange b}} meson''' is a type of unstable subatomic particle known as a meson. It is notable for its observed ability to spontaneously switch into its own antiparticle and back, a rare phenomenon known as particle oscillation.
Because the properties of this oscillation and the particle's other rare decays are very precisely predicted by the Standard Model of particle physics, the strange B meson is of significant interest to scientists. Experiments at facilities like Fermilab and the Large Hadron Collider study the particle to test the limits of the Standard Model and search for new physics. The strange B meson is composed of two elementary particles: a bottom antiquark and a strange quark.
== B–B oscillations == Strange B mesons are noted for their ability to oscillate between matter and antimatter via a box-diagram with {{nowrap|Δ''m''<sub>s</sub> {{=}} 17.77 ± 0.10 (stat) ± 0.07 (syst) ps<sup>−1</sup>}} measured by CDF experiment at Fermilab.<ref>{{Cite journal |author=A. Abulencia ''et al.'' (CDF Collaboration) |year=2006 |title=Observation of {{Subatomic particle|Strange B0}}–{{Subatomic particle|Strange antiB0}} Oscillations |journal=Physical Review Letters |volume=97 |issue=24 |article-number=242003 |arxiv=hep-ex/0609040 |bibcode=2006PhRvL..97x2003A |doi=10.1103/PhysRevLett.97.242003 |pmid=17280271 }}</ref> That is, a meson composed of a bottom quark and strange antiquark, the strange {{Subatomic particle|antib}} meson, can spontaneously change into an bottom antiquark and strange quark pair, the strange {{Subatomic particle|b}} meson, and vice versa.
On 25 September 2006, Fermilab announced that they had claimed discovery of previously-only-theorized B<sub>s</sub> meson oscillation.<ref name="fnal"> {{cite press release |publisher=Fermilab |date=25 September 2006 |title=It might be... It could be... It is!!! |url=http://www.fnal.gov/pub/presspass/press_releases/CDF_meson.html |access-date=2007-12-08 }}</ref> According to Fermilab's press release:
{{quote|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).<ref name="fnal"/>}}
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".<ref> {{Cite news |author=R. Kotulak |url=http://deseretnews.com/dn/view/0,1249,650194039,00.html |archive-url=https://web.archive.org/web/20061018173736/http://deseretnews.com/dn/view/0,1249,650194039,00.html |archive-date=18 October 2006 |date=26 September 2006 |title=Antimatter discovery could alter physics: Particle tracked between real world, spooky realm |work=Deseret News |access-date=2007-12-08 }}</ref>
Better understanding of the meson is one of the main objectives of the LHCb experiment conducted at the Large Hadron Collider.<ref>{{cite web |date=June 2008 |url=http://lhcb.web.cern.ch/lhcb/Hot%20News/Articles/PWJun08gershon.pdf |title=A Taste of LHC Physics |work=Physics World |pages=22–25 |access-date=23 September 2011 |archive-date=4 July 2018 |archive-url=https://web.archive.org/web/20180704154401/http://lhcb.web.cern.ch/lhcb/Hot%20News/Articles/PWJun08gershon.pdf |url-status=dead }}</ref> On 24 April 2013, CERN physicists in the LHCb collaboration announced that they had observed CP violation in the decay of strange {{Subatomic particle|b}} mesons for the first time.<ref> {{cite web | date=24 April 2013 | title=LHCb experiment observes new matter-antimatter difference | url=http://press.web.cern.ch/press-releases/2013/04/lhcb-experiment-observes-new-matter-antimatter-difference | publisher=CERN Press Office | access-date=2013-04-24 }}</ref><ref> {{cite journal |author=R. Aaij ''et al.'' (LHCb collaboration) |year=2013 |title=First Observation of C P Violation in the Decays of B s 0 Mesons |journal=Physical Review Letters |volume=110 |issue=22 |article-number=221601 |arxiv=1304.6173 |bibcode=2013PhRvL.110v1601A |doi=10.1103/PhysRevLett.110.221601 |pmid=23767711 |s2cid=20486226 }}</ref> Scientists found the B<sub>s</sub> meson decaying into two muons for the first time, with Large Hadron Collider experiments casting doubt on the scientific theory of supersymmetry.<ref> {{cite web |author=M. Hogenboom |date=24 July 2013 |title=Ultra-rare decay confirmed in LHC |url=https://www.bbc.co.uk/news/science-environment-23431797 |publisher=BBC |access-date=2013-08-18 }}</ref><ref>{{cite web |author=CMS |date=14 May 2015 |title=Mathematical explanation from GENUINE published result |url=http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14474.html |publisher=Nature |access-date=2015-05-15 }}</ref>
CERN physicist Tara Shears described the CP violation observations as "verification of the validity of the Standard Model of physics".<ref name="WiredCPViolation"> {{cite magazine | author=M. Piesing | date=24 April 2013 | title=Cern physicists observe new difference between matter and antimatter | url=https://www.wired.co.uk/news/archive/2013-04/24/cern-antimatter | magazine=Wired UK | access-date=2013-04-24 }}</ref>
== Rare decays == The rare decays of the B<sub>s</sub> meson are an important test of the Standard Model. The branching fraction of the strange b-meson to a pair of muons is very precisely predicted with a value of Br(B<sub>s</sub>→ μ<sup>+</sup>μ<sup>−</sup>)<sub>SM</sub> = (3.66 ± 0.23) × 10<sup>−9</sup>. Any variation from this rate would indicate possible physics beyond the Standard Model, such as supersymmetry. The first definitive measurement was made from a combination of LHCb and CMS experiment data:<ref>{{Cite journal|title = Observation of the rare Bs0 →μ+μ− decay from the combined analysis of CMS and LHCb data|journal = Nature|date = 4 June 2015|issn = 0028-0836|pages = 68–72|volume = 522|issue = 7554|doi = 10.1038/nature14474|first = C. M. S.|last = Collaboration|arxiv = 1411.4413 |bibcode = 2015Natur.522...68C|pmid=26047778|s2cid = 4394036}}</ref>
<math>Br(B_s \rightarrow \mu^+\mu^-) = 2.8^{+0.7}_{-0.6} \times 10^{-9}</math>
This result is compatible with the Standard Model and set limits on possible extensions.
== See also == *B meson *B–{{Subatomic particle|Antib}} oscillation
==References== {{Reflist}}
==External links== *{{Cite web |author=V. Jamieson |date=18 March 2008 |title=Flipping particle could explain missing antimatter |url=https://www.newscientist.com/channel/fundamentals/mg19726483.600-flipping-particle-could-explain-missing-antimatter.html |work=New Scientist |access-date=2010-01-23 }}
{{Particles}}
{{Use dmy dates|date=August 2019}}
{{DEFAULTSORT:Strange B Meson}} Category:Mesons Category:Strange quark Category:B physics
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