Strange B meson

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.


B
s meson
Composition
b

s
StatisticsBosonic
FamilyMesons
InteractionsStrong, Weak, Gravitational, Electromagnetic
Antiparticle
B
s (
b

s
)
Mass5366.3±0.6 MeV/c2
Mean lifetime1.470+0.027
−0.026×10−12 s
Decays intoSee
B0
s decay modes
Electric charge0 e
Spin0
Strangeness-1
Bottomness+1
Isospin0
Parity-1

B–B oscillations

Strange B mesons are noted for their ability to oscillate between matter and antimatter via a box-diagram with Δms = 17.77 ± 0.10 (stat) ± 0.07 (syst) ps−1 measured by CDF experiment at Fermilab.[1] That is, a meson composed of a bottom quark and strange antiquark, the strange
B
 meson, can spontaneously change into an bottom antiquark and strange quark pair, the strange
B
 meson, and vice versa.

On 25 September 2006, Fermilab announced that they had claimed discovery of previously-only-theorized Bs meson oscillation.[2] 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).[2]

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".[3]

Better understanding of the meson is one of the main objectives of the LHCb experiment conducted at the Large Hadron Collider.[4] On 24 April 2013, CERN physicists in the LHCb collaboration announced that they had observed CP violation in the decay of strange
B
 mesons for the first time.[5][6] Scientists found the Bs meson decaying into two muons for the first time, with Large Hadron Collider experiments casting doubt on the scientific theory of supersymmetry.[7][8]

CERN physicist Tara Shears described the CP violation observations as "verification of the validity of the Standard Model of physics".[9]

Rare decays

The rare decays of the Bs 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(Bs→ µ+µ−)SM = (3.66 ± 0.23) × 10−9. 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:[10]

This result is compatible with the Standard Model and set limits on possible extensions.

See also

References
  1. A. Abulencia 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. PMID 17280271.
  2. "It might be... It could be... It is!!!" (Press release). Fermilab. 25 September 2006. Retrieved 8 December 2007.
  3. R. Kotulak (26 September 2006). "Antimatter discovery could alter physics: Particle tracked between real world, spooky realm". Deseret News. Retrieved 8 December 2007.
  4. "A Taste of LHC Physics" (PDF). Physics World. June 2008. pp. 22–25.
  5. "LHCb experiment observes new matter-antimatter difference". CERN Press Office. 24 April 2013. Retrieved 24 April 2013.
  6. R. Aaij et al. (LHCb collaboration) (2013). "First Observation of C P Violation in the Decays of B s 0 Mesons". Physical Review Letters. 110 (22): 221601. arXiv:1304.6173. Bibcode:2013PhRvL.110v1601A. doi:10.1103/PhysRevLett.110.221601. PMID 23767711. S2CID 20486226.
  7. M. Hogenboom (24 July 2013). "Ultra-rare decay confirmed in LHC". BBC. Retrieved 18 August 2013.
  8. CMS (14 May 2015). "Mathematical explanation from GENUINE published result". Nature. Retrieved 15 May 2015.
  9. M. Piesing (24 April 2013). "Cern physicists observe new difference between matter and antimatter". Wired UK. Retrieved 24 April 2013.
  10. Collaboration, C. M. S. (4 June 2015). "Observation of the rare Bs0 →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. ISSN 0028-0836. PMID 26047778. S2CID 4394036.


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