Double-charm tetraquark

{{Short description|Type of tetraquark}}

{{Infobox particle

| bgcolour =

| classification = meson

| name = Double-charm tetraquark

| image = Quark structure double-charm tetraquark.svg

| caption =

| num_types =

| composition = 2 charm quarks
1 up antiquark
1 down antiquark

| statistics = bosonic

| group = hadron

| generation =

| electric_charge = +1

| mass = {{val|3868|124|ul=MeV/c2}}{{cite journal |last1=Agaev |first1=S.S. |last2=Azizi |first2=K. |last3=Sundu |first3=H. |title=Newly observed exotic doubly charmed meson $T\_\{cc\}^+$|journal=Nuclear Physics B |date=February 2022 |volume=975 |pages=115650 |doi=10.1016/j.nuclphysb.2022.115650|arxiv=2108.00188|s2cid=236772263 }}

| spin = 1⁺

| isospin = 0{{Cite journal |last1=Aaij |first1=R. |last2=Abdelmotteleb |first2=A. S. W. |last3=Abellán Beteta |first3=C. |last4=Abudinen Gallego |first4=F. J. |last5=Ackernley |first5=T. |last6=Adeva |first6=B. |last7=Adinolfi |first7=M. |last8=Afsharnia |first8=H. |last9=Agapopoulou |first9=C. |last10=Aidala |first10=C. A. |last11=Aiola |first11=S. |date=2022-06-16 |title=Observation of an exotic narrow doubly charmed tetraquark |url=https://www.nature.com/articles/s41567-022-01614-y |journal=Nature Physics |volume=18 |issue=7 |language=en |pages=751–754 |doi=10.1038/s41567-022-01614-y |arxiv=2109.01038 |bibcode=2022NatPh..18..751L |s2cid=237385202 |issn=1745-2481}}

| mean_lifetime = {{val|1.35|0.31|0.21|e=-21|u=s}}

}}

The double-charm tetraquark (T{{su|lh=1|p=+|b=cc}}, cc{{overline|u}}{{overline|d}}) is a type of long-lived tetraquark that was discovered in 2021 in the LHCb experiment conducted at the Large Hadron Collider.{{Cite web|title=What to Know About the Newly Discovered Tetraquark at the Large Hadron Collider|url=https://gizmodo.com/what-to-know-about-the-newly-discovered-tetraquark-at-t-1847396650|access-date=2021-09-27|website=Gizmodo|date=2 August 2021 |language=en-us}}{{Cite web|title=Twice the charm: long-lived exotic particle discovered|url=https://home.cern/news/news/physics/twice-charm-long-lived-exotic-particle-discovered|access-date=2021-09-29|website=CERN|language=en}}{{Cite journal |last1=Aaij |first1=R. |last2=Abdelmotteleb |first2=A. S. W. |last3=Beteta |first3=C. Abellán |last4=Gallego |first4=F. J. Abudinen |last5=Ackernley |first5=T. |last6=Adeva |first6=B. |last7=Adinolfi |first7=M. |last8=Afsharnia |first8=H. |last9=Agapopoulou |first9=C. |last10=Aidala |first10=C. A. |last11=Aiola |first11=S. |date=2022-06-16 |title=Study of the doubly charmed tetraquark T⁺_cc |journal=Nature Communications |language=en |volume=13 |issue=1 |pages=3351 |doi=10.1038/s41467-022-30206-w |pmid=35710739 |pmc=9203551 |issn=2041-1723}} It contains four quarks: two charm quarks, an anti-up and an anti-down quark.

It has a theoretical computed mass of {{val|3868|124|u=MeV/c2}}. The discovery showed an exceptionally strong peak, with 20-sigma significance.{{Cite web|title=LHCb experiment spots extraordinary double charmed tetraquark|url=https://www.nikhef.nl/en/news/lhcb-experiment-spots-extraordinary-double-charmed-tetraquark/|access-date=2021-09-27|website=Nikhef|language=en-US}}

It is hypothesized that studying the behavior of the double-charm tetraquark may play a part in explaining the behavior of the strong force.{{Cite web|last=Wood|first=Charlie|date=2021-09-27|title='Impossible' Particle Discovery Adds Key Piece to the Strong Force Puzzle|url=https://www.quantamagazine.org/impossible-particle-discovery-adds-key-piece-to-the-strong-force-puzzle-20210927/|access-date=2021-09-27|website=Quanta Magazine|language=en}} Following the discovery of the T{{su|lh=1|p=+|b=cc}}, researchers now plan experiments to find its double-beauty counterpart T{{sub|bb}}.{{Cite web|last=Turner|first=Ben|date=2021-08-05|title=New 'doubly charming' particle could help unlock the secrets of how matter is built|url=https://www.livescience.com/double-charm-tetraquark-found-lhc.html|access-date=2021-09-27|website=livescience.com|language=en}} This tetraquark has been found to have a longer lifespan than most known exotic-matter particles.