Tetraquark Explained

In particle physics, a tetraquark is an exotic meson composed of four valence quarks. A tetraquark state has long been suspected to be allowed by quantum chromodynamics,[1] 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.

History and discoveries

Several tetraquark candidates have been reported by particle physics experiments in the 21st century. The quark contents of these states are almost all qQ, where q represents a light (up, down or strange) quark, Q represents a heavy (charm or bottom) quark, and antiquarks are denoted with an overline. The existence and stability of tetraquark states with the qq (or QQ) have been discussed by theoretical physicists for a long time, however these are yet to be reported by experiments.[2]

TimelineIn 2003, a particle temporarily called X(3872), by the Belle experiment in Japan, was proposed to be a tetraquark candidate,[3] as originally theorized.[4] The name X is a temporary name, indicating that there are still some questions about its properties to be tested. The number following is the mass of the particle in .

In 2004, the DsJ(2632) state seen in Fermilab's SELEX was suggested as a possible tetraquark candidate.[5]

In 2007, Belle announced the observation of the Z(4430) state, a tetraquark candidate. There are also indications that the Y(4660), also discovered by Belle in 2007, could be a tetraquark state.[6]

In 2009, Fermilab announced that they have discovered a particle temporarily called Y(4140), which may also be a tetraquark.[7]

In 2010, two physicists from DESY and a physicist from Quaid-i-Azam University re-analyzed former experimental data and announced that, in connection with the (5S) meson (a form of bottomonium), a well-defined tetraquark resonance exists.[8] [9]

In June 2013, the BES III experiment in China and the Belle experiment in Japan independently reported on Zc(3900), the first confirmed four-quark state.[10]

In 2014, the Large Hadron Collider experiment LHCb confirmed the existence of the Z(4430) state with a significance of over 13.9 σ.[11] [12]

In February 2016, the DØ experiment reported evidence of a narrow tetraquark candidate, named X(5568), decaying to .[13] In December 2017, DØ also reported observing the X(5568) using a different final state.[14] However, it was not observed in searches by the LHCb,[15] CMS,[16] CDF,[17] or ATLAS[18] experiments.

In June 2016, LHCb announced the discovery of three additional tetraquark candidates, called X(4274), X(4500) and X(4700).[19] [20] [21]

In 2020, LHCb announced the discovery of atetraquark: X(6900).[22] [23] In 2022, ATLAS observed X(6900).[24]

In 2021, LHCb announced the discovery of four additional tetraquarks, including cu.[25]

In 2022, LHCb announced the discovery of cu and cd.[26]

See also

External links

Notes and References

  1. U. Kulshreshtha. D. S. Kulshreshtha. J. P. Vary. Hamiltonian, path integral and BRST formulations of large N scalar QCD2 on the light-front and spontaneous symmetry breaking. European Physical Journal C. 75. 4. 174. 2015. 10.1140/epjc/s10052-015-3377-x. 1503.06177. 2015EPJC...75..174K. 119102254 .
  2. Si-Qiang. Luo. Kan. Chen. Xiang. Liu. Yan-Rui. Liu. Shi-Lin. Zhu. Exotic tetraquark states with the qq configuration. European Physical Journal C. 25 October 2017. 77:709. 10. 26 November 2017. 10.1140/epjc/s10052-017-5297-4. 119377466. free.
  3. Web site: D. Harris . 13 April 2008. The charming case of X(3872). Symmetry Magazine. 2009-12-17.
  4. L. Maiani. F. Piccinini. V. Riquer. A.D. Polosa. 2005. Diquark-antidiquarks with hidden or open charm and the nature of X(3872). Physical Review D. 71. 1. 014028. hep-ph/0412098. 2005PhRvD..71a4028M. 10.1103/PhysRevD.71.014028 . 119345314 .
  5. hep-ph/0408124. Kulshreshtha. Usha. Regge Trajectories Analysis to D(2317)±, DSJ(2460)± and DSJ(2632)+ Mesons. Physical Review D. 72. 017902. Daya Shankar Kulshreshtha. Vary. James P.. 2005. 10.1103/PhysRevD.72.017902. 10124970 .
  6. G. Cotugno. R. Faccini. A.D. Polosa. C. Sabelli. 2010. Charmed Baryonium. Physical Review Letters. 104. 13. 132005. 0911.2178. 2010PhRvL.104m2005C. 10.1103/PhysRevLett.104.132005. 20481876. 353652 .
  7. Web site: A. Minard. 18 March 2009. New Particle Throws Monkeywrench in Particle Physics. Universe Today. 2014-04-12.
  8. Web site: Z. Matthews. 27 April 2010. Evidence grows for tetraquarks. Physics World. 2014-04-12. 2011-11-09. https://web.archive.org/web/20111109013800/http://physicsworld.com/cws/article/news/42475. dead.
  9. A. Ali. C. Hambrock. M.J. Aslam. 2010. Tetraquark Interpretation of the BELLE Data on the Anomalous Υ(1S)π+π− and Υ(2S)π+π− Production near the Υ(5S) Resonance. Physical Review Letters. 104. 16. 162001. 0912.5016. 2010PhRvL.104p2001A. 10.1103/PhysRevLett.104.162001. 20482041 .
  10. E. Swanson. 2013. Viewpoint: New Particle Hints at Four-Quark Matter. Physics. 6. 69. 2013PhyOJ...6...69S. 10.1103/Physics.6.69. free .
  11. Web site: C. O'Luanaigh. 9 Apr 2014. LHCb confirms existence of exotic hadrons. CERN. 2016-04-04.
  12. R. Aaij. etal. LHCb collaboration. 2014. Observation of the resonant character of the Z(4430)− state. Physical Review Letters. 1404.1903. 2014PhRvL.112v2002A. 10.1103/PhysRevLett.112.222002. 112. 22. 24949760. 222002. 904429 .
  13. V. M. Abazov. etal. D0 collaboration. 2016. Observation of a new state. 1602.07588. 10.1103/PhysRevLett.117.022003. 27447502. 117. 2. 022003. Physical Review Letters. 2016PhRvL.117b2003A. 7789961 .
  14. 1712.10176. Abazov. V.M.. D0 collaboration. Study of the X±(5568) state with semileptonic decays of the B meson. Physical Review D. 97. 9. 092004. 2018. 10.1103/PhysRevD.97.092004. 2018PhRvD..97i2004A. 119337959. etal.
  15. Web site: J. van Tilburg. 13 March 2016. Recent hot results & semileptonic b hadron decay. CERN. 2016-04-04.
  16. 1712.06144. Sirunyan. A. M.. CMS Collaboration. Search for the X(5568) State Decaying into Bπ± in Proton-Proton Collisions at √s =8  TeV. Physical Review Letters. 120. 20. 202005. 2018. 10.1103/PhysRevLett.120.202005. 29864318. 119402891. etal.
  17. 1712.09620. Aaltonen. T.. CDF Collaboration. A search for the exotic meson X(5568) with the Collider Detector at Fermilab. Physical Review Letters. 120. 20. 202006. 2018. 10.1103/PhysRevLett.120.202006. 29864341. 2018PhRvL.120t2006A. 43934060. etal.
  18. 1802.01840. Aaboud. M.. ATLAS Collaboration. Search for a Structure in the B π± Invariant Mass Spectrum with the ATLAS Experiment. Physical Review Letters. 120. 20. 202007. 2018. 10.1103/PhysRevLett.120.202007. 29864314. 2018PhRvL.120t2007A. 216915898. etal.
  19. http://lhcb-public.web.cern.ch/lhcb-public/#JpsiPhiExotics Announcement by LHCb
  20. R. Aaij. etal. LHCb collaboration. 2017. Observation of J/ψφ structures consistent with exotic states from amplitude analysis of B→J/ψφK decays. 1606.07895. 10.1103/PhysRevLett.118.022003. 28128595. 118. 2. 022003. Physical Review Letters. 2017PhRvL.118b2003A. 206284149 .
  21. R. Aaij. etal. LHCb collaboration. 2017. Amplitude analysis of B→J/ψφK decays. 1606.07898. 10.1103/PhysRevD.95.012002. 95. 1. 012002. Physical Review D. 2017PhRvD..95a2002A. 73689011 .
  22. R. Aaij. etal. LHCb collaboration. 2020. Observation of structure in the J/ψ-pair mass spectrum. Science Bulletin. 65. 23. 1983–1993. 10.1016/j.scib.2020.08.032. 36659056. 2006.16957. 2020SciBu..65.1983L. 220265852 .
  23. Web site: 1 July 2020. Observation of a four-charm-quark tetraquark.. LHCb - Large Hadron Collider beauty experiment. CERN. 12 July 2020.
  24. Web site: ATLAS observes potential four-charm tetraquark. 2022-07-21. ATLAS. en.
  25. LHCb collaboration. Aaij. R.. Beteta. C. Abellán. Ackernley. T.. Adeva. B.. Adinolfi. M.. Afsharnia. H.. Aidala. C. A.. Aiola. S.. Ajaltouni. Z.. Akar. S.. 2021-03-02. Observation of New Resonances Decaying to J/ψK+ and J/ψϕ. Physical Review Letters. 127. 8. 082001. 10.1103/PhysRevLett.127.082001. 34477418. 2103.01803. 2021PhRvL.127h2001A. 232092368.
  26. Web site: LHCb discovers three new exotic particles. CERN. 5 July 2022. 8 July 2022.

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