Xi baryon


Xi baryon

The Xi baryons or cascade particles are a family of subatomic hadron particles which have the symbol Ξ and have a +2, +1 or -1 elementary charge or are neutral. They are baryons containing three quarks: one up or down quark, and two heavier quarks. They are sometimes called the cascade particles because of their unstable state; they decay rapidly into lighter particles through a chain of decays [1]. The first discovery of a charged Xi baryon was in cosmic ray experiments by the Manchester group in 1952.[2] The first discovery of the neutral Xi particle was at Lawrence Berkeley Laboratory in 1959.[3] It was also observed as a daughter product from the decay of the omega baryon (Ω
) observed at Brookhaven National Laboratory in 1964.[4]

The Ξ
b
particle is also known as the cascade B particle and contains quarks from all three families. It was discovered by and CDF experiments at Fermilab. The discovery was announced on 12 June 2007. It was the first known particle made of quarks from all three quark generations—namely, a down quark, a strange quark, and a bottom quark. The DØ collaboration reported mass of the new state to be 5.774±0.019 GeV/c2; while the CDF collaboration measured the mass at 5.7929±0.0030 GeV/c2. The two results are consistent with each other. The Particle Data Group world average mass is 5.7924±0.0030 GeV/c2.

When unspecified, the non-up/down quark content of Xi baryons is strange. Thus a Ξ0
b
is contains one up, one strange, and one bottom quark, while a Ξ0
bb
contains one up and two bottom quarks.

Xi Baryons[5][6][7][8]
Particle Symbol Makeup Rest mass
MeV/c2
Isospin
I
Spin(Parity)
JP
Q S C B Mean lifetime
s
Decays to
Xi [9] Ξ0
uss 1 314.86 ± 0.20 12 12+* 0 −2 0 0 2.90 ± 0.09×10−10 Λ0
+ π0
Xi [10] Ξ
dss 1321.31 ± 0.13 12 12+* −1 −2 0 0 1.639±0.015×10−10 Λ0
+ π
Xi resonance [11] Ξ0
(1530)
uss 1 531.80(32) 12 32+ 0 −2 0 0 Ξ + π
Xi resonance [11] Ξ
(1530)
dss 1 535.0(6) 12 32+ −1 −2 0 0 Ξ + π
charmed Xi[12] Ξ+
c
usc 2 467.9 ± 0.4 12 12* +* +1 −1 +1 0 4.42±0.26×10−13 See Ξ+
c
Decay Modes
charmed Xi[12] Ξ0
c
dsc 2 471.0 ± 0.4 12 12* +* 0 −1 +1 0 1.12+0.13
−0.10
×10−13
See Ξ0
c
Decay Modes
charmed Xi resonance [12] Ξ′+
c
usc 2 575.7±3.1 12 12+ +1 −1 +1 0 Ξ+
c
+ γ (Seen)
charmed Xi resonance [12] Ξ′0
c
dsc 2 578.0±2.9 12 12+ 0 −1 +1 0 1.1×10−13 Ξ0
c
+ γ (Seen)
double charmed Xi Ξ++
cc
ucc 12* 12* +* +2 0 +2 0
double charmed Xi[a] [13] Ξ+
cc
dcc 3 518.9 ± 0.9[c] 12* 12* +* +1 0 +2 0 <3.3×10−14[a] Λ+
c
+ K
+ π+
[e] or
p+
+ D+
+ K
[e]
bottom Xi [14] Ξ0
b
usb 5 792 ± 3 12* 12* +* 0 −1 0 −1 1.42+0.28
−0.24
×10−12
[b]
See Ξ
b
Decay Modes
bottom Xi or
Cascade B [14][15][16]
Ξ
b
dsb 5 792.9 ± 3.0 12* 12* +* −1 −1 0 −1 1.42×10−12 See Ξ
b
Decay Modes

(Ξ
+ J/ψ
was also seen)
double bottom Xi Ξ0
bb
ubb 12* 12* +* 0 0 0 −2
double bottom Xi Ξ
bb
dbb 12* 12* +* −1 0 0 −2
charmed bottom Xi Ξ+
cb
ucb 12* 12* + +1 0 +1 −1
charmed bottom Xi Ξ0
cb
dcb 12* 12* +* 0 0 +1 −1

[a] Some controversy exists about this data. See references
[b] This is actually a measurement of the average lifetime of b-baryons that decay to a jet containing a same sign Ξ±l± pair. Presumably the mix is mainly Ξ
b
, with some Λ
b
.
† Particle (or quantity, i.e. spin) has neither been observed nor indicated.

See also

References

  1. ^ "The Xi Baryon; http://hyperphysics.phy-astr.gsu.edu/hbase/particles/xi.html"
  2. ^ R. Armenterosa, et al (1952). "The properties of charged V-particles". Philosophical Magazine 43 (341): 597. doi:10.1080/14786440608520216. http://www.informaworld.com/smpp/content~db=all~content=a910643548~frm=titlelink. 
  3. ^ L. W. Alvarez, et al (1959). "Neutral Cascade Hyperon Event". Physical Review Letters 2 (5): 215. Bibcode 1959PhRvL...2..215A. doi:10.1103/PhysRevLett.2.215. 
  4. ^ R. Nave. "The Xi Baryon". HyperPhysics. http://hyperphysics.phy-astr.gsu.edu/hbase/particles/xi.html. Retrieved 2009-06-20. 
  5. ^ V. Abazov, et al (Collaboration) (2007). "Direct observation of the strange b baryon Ξ
    b
    ". Physical Review Letters 99 (5). arXiv:0706.1690. Bibcode 2007PhRvL..99e2001A. doi:10.1103/PhysRevLett.99.052001.
     
  6. ^ "Fermilab physicists discover "triple-scoop" baryon" (Press release). Fermilab. 2007. http://www.fnal.gov/pub/presspass/press_releases/Dzero_baryon.html. Retrieved 2007-06-14. 
  7. ^ "Back-to-Back b Baryons in Batavia" (Press release). Fermilab. 2007. http://www.fnal.gov/pub/presspass/press_releases/backtobackBaryons.html. Retrieved 2007-06-25. 
  8. ^ T. Aaltonen, et al (CDF Collaboration) (2007). "Observation and mass measurement of the baryon Xi(b)-". Physical Review Letters 99 (5). arXiv:0707.0589. Bibcode 2007PhRvL..99e2002A. doi:10.1103/PhysRevLett.99.052002. 
  9. ^ W.-M. Yao et al. (2006). "Particle listings - Neutral Xi". Journal of Physics G (Particle Data Group) 33 (1). http://pdg.lbl.gov/2007/listings/s023.pdf. Retrieved 2008-04-20. 
  10. ^ W.-M. Yao et al. (2006). "Particle listings - Negative Xi". Journal of Physics G (Particle Data Group) 33 (1). http://pdg.lbl.gov/2007/listings/s022.pdf. Retrieved 2008-04-20. 
  11. ^ a b "Particle Data Groups: 2006 Review of Particle Physics - Xi(1530)". http://pdg.lbl.gov/2007/listings/b049.pdf. Retrieved 2008-04-20. 
  12. ^ a b c d W.-M. Yao et al. (2006). "Particle listings - Charmed baryons". Journal of Physics G (Particle Data Group) 33 (1). http://pdg.lbl.gov/2007/tables/bxxxcharm.pdf. Retrieved 2008-04-20. 
  13. ^ W.-M. Yao et al. (2006). "Particle listings - Double charmed positive Xi". Journal of Physics G (Particle Data Group) 33 (1). http://pdg.lbl.gov/2007/listings/s065.pdf. Retrieved 2008-04-20. 
  14. ^ a b W.-M. Yao et al. (2006). "Particle listings - Bottom Xis". Journal of Physics G (Particle Data Group) 33 (1). http://pdg.lbl.gov/2007/listings/s060.pdf. Retrieved 2008-04-20. 
  15. ^ V. M. Abazov et al. (2007). "Direct observation of the strange b baryon Ξ
    b
    ". Physical Review Letters 99 (5): 052001. arXiv:0706.1690. Bibcode 2007PhRvL..99e2001A. doi:10.1103/PhysRevLett.99.052001.
     
  16. ^ T. Aaltonen et al. (2007). "Observation and mass measurement of the baryon Ξ
    b
    ". Physical Review Letters 99 (5): 052002. arXiv:0707.0589. Bibcode 2007PhRvL..99e2002A. doi:10.1103/PhysRevLett.99.052002.
     

External links


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Baryon omega — Baryon Oméga Oméga Propriétés générales Classification Baryon Composition Trois quarks, ni u, ni d Propriétés physiques Masse • Ω  : 1,672 GeV.c 2 • Ω0c : 2,697 GeV.c 2 …   Wikipédia en Français

  • Baryon oméga — Oméga Propriétés générales Classification Baryon Composition Trois quarks, ni u, ni d Propriétés physiques Masse • Ω  : 1,672 GeV.c 2 • Ω0c : 2,697 GeV.c 2 …   Wikipédia en Français

  • Baryon delta — Delta Propriétés générales Classification Baryon Composition 3 quarks u et d Propriétés physiques Masse 1,232 GeV.c 2 Charge électrique • Δ++ : +2 …   Wikipédia en Français

  • Baryon xi — Xi Propriétés générales Classification Baryon Composition 1 quark s, 1 quark u ou d, 1 quark c ou s Propriétés physiques Masse • Ξ0 : 1,315 GeV.c 2 • Ξ …   Wikipédia en Français

  • baryon — [ barjɔ̃ ] n. m. • v. 1959; de bary et (électr)on ♦ Phys. Hadron lourd, particule élémentaire formée de trois quarks. Les baryons comprennent les nucléons et les hypérons. ● baryon nom masculin Nom générique des hadrons de spin demi entier. ●… …   Encyclopédie Universelle

  • Baryon lambda — En physique des particules, un baryon lambda, noté par la lettre grecque Λ, est un baryon instable non chargé, constitué de trois quarks : un quark up, un quark down et un quark bottom (c est alors un baryon Λ0b), charm (Λ+c) ou strange (Λ0) …   Wikipédia en Français

  • Baryon Exotique — Un baryon exotique est, en physique des particules, un baryon formé de trois quarks et d une ou plusieurs autres particules (qui peuvent également être des quarks). À l heure actuelle (fin 2005), le pentaquark serait le seul baryon exotique à… …   Wikipédia en Français

  • Baryon sigma — Les baryons Sigma (aussi appelés particules Sigma) sont des baryons composés d un quark étrange (dit quark s) et d une combinaison de quarks up et down, le tout possédant un isospin de 1. Les baryons sigma sont des hypérons. Ils sont notés avec… …   Wikipédia en Français

  • baryon — aryon n. 1. any of the elementary particles having a mass equal to or greater than that of a proton and that participate in strong interactions; a hadron with a baryon number of +1. Syn: heavy particle. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • baryon — [bar′ē än΄, ber′ē än΄] n. [< Gr barys, heavy (see GRAVE1) + (ELECTR)ON] Particle Physics a subatomic particle that is both a hadron and a fermion, as a nucleon or hyperon: the proton is the baryon with the smallest mass …   English World dictionary

  • Baryon number — Flavour in particle physics Flavour quantum numbers: Isospin: I or I3 Charm: C Strangeness: S Topness: T Bottomness: B′ Related quantum numbers: Baryon number: B Lepton number: L Weak isospin: T or T3 Electric charge: Q …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.