tetraneutron

Francisco-Miguel Marqués and co-workers at the GANIL accelerator in Caen used a particle accelerator to fire atomic nuclei at carbon targets and observed the "spray" of particles from the resulting collisions.{{Cite journal |last1=Marqués |first1=F. Miguel |last2=Carbonell |first2=Jaume |date=March 2021 |title=The quest for light multineutron systems |url=https://link.springer.com/10.1140/epja/s10050-021-00417-8 |journal=The European Physical Journal A |language=en |volume=57 |issue=3 |page=105 |doi=10.1140/epja/s10050-021-00417-8 |issn=1434-6001|arxiv=2102.10879 |bibcode=2021EPJA...57..105M |s2cid=231986449 }} In this case the experiment involved firing beryllium-14, boron-15 and lithium-11 nuclei at a small carbon target, the most successful being beryllium-14. This isotope of beryllium has a nuclear halo that consists of four clustered neutrons; this allows it to be easily separated intact in the high-speed collision with the carbon target.{{Cite journal |last1=Marqués |first1=F. M. |last2=Labiche |first2=M. |last3=Orr |first3=N. A. |last4=Angélique |first4=J. C. |last5=Axelsson |first5=L. |last6=Benoit |first6=B. |last7=Bergmann |first7=U. C. |last8=Borge |first8=M. J. G. |last9=Catford |first9=W. N. |last10=Chappell |first10=S. P. G. |last11=Clarke |first11=N. M. |last12=Costa |first12=G. |last13=Curtis |first13=N. |last14=D’Arrigo |first14=A. |last15=de Góes Brennand |first15=E. |date=2002-04-01 |title=Detection of neutron clusters |url=https://link.aps.org/doi/10.1103/PhysRevC.65.044006 |journal=Physical Review C |language=en |volume=65 |issue=4 |page=044006 |doi=10.1103/PhysRevC.65.044006 |issn=0556-2813|arxiv=nucl-ex/0111001 |bibcode=2002PhRvC..65d4006M |s2cid=37431352 }} Current nuclear models suggest that four separate neutrons should result when beryllium-10 is produced, but the single signal detected in the production of beryllium-10 suggested a multineutron cluster in the breakup products; most likely a beryllium-10 nucleus and four neutrons fused together into a tetraneutron.

A later analysis of the method used in the Marqués' experiment suggested that the detection mechanism was unlikely{{cite journal

| last1 = Sherrill | first1 = B. M.

| last2 = Bertulani | first2= C. A

| year = 2004

| title = Proton-tetraneutron elastic scattering

| journal = Physical Review C

| volume = 69 | issue = 2 | pages = 027601

| doi = 10.1103/PhysRevC.69.027601

| arxiv = nucl-th/0312110 |bibcode = 2004PhRvC..69b7601S | s2cid = 26590179

}} but the suggestion was refuted,{{cite arXiv

| last = Marqués | first = F. M.

| display-authors= etal

| year = 2005

| title = On the possible detection of ⁴n events in the breakup of ¹⁴Be

|eprint = nucl-ex/0504009v1

}} and attempts to reproduce these observations with different methods have not successfully detected any neutron clusters.{{cite journal

| last = Aleksandrov | first = D. V.

| display-authors= etal

| year = 2005

| title = Search for Resonances in the Three- and Four-Neutron Systems in the ⁷Li (⁷Li, ¹¹C) 3n and ⁷Li (⁷Li, ¹⁰C) 4n Reactions

| journal = JETP Letters

| volume = 81 | issue = 2 | pages = 43–46

| doi = 10.1134/1.1887912

| bibcode = 2005JETPL..81...43A

| s2cid = 121267804

}}

If, however, the existence of bound tetraneutrons were ever independently confirmed, considerable adjustments would have to be made to current nuclear models. Bertulani and Zelevinsky proposed that, if it existed, the tetraneutron could be formed by a bound state of two dineutron systems.

{{cite journal

| last1 = Bertulani | first1 = C. A.

| last2 = Zelevinsky |first2 = V. G.

| year = 2003

| title = Tetraneutron as a dineutron-dineutron molecule

| journal = Journal of Physics G

| volume = 29 | pages = 2431–2437

| doi = 10.1088/0954-3899/29/10/309

| arxiv= nucl-th/0212060

| bibcode = 2003JPhG...29.2431B

| issue = 10

| s2cid = 55535943

}} However, attempts to model interactions that might give rise to multineutron clusters have failed,{{cite journal

| last1 = Lazauskas | first1 = R.

| last2 = Carbonell | first2 = J.

| year = 2005

| title = Three-neutron resonance trajectories for realistic interaction models

| journal = Physical Review C

| volume = 71 | pages = 044004

| doi = 10.1103/PhysRevC.71.044004

| arxiv= nucl-th/0502037v2

| bibcode = 2005PhRvC..71d4004L

| issue = 4 | s2cid = 119105439

}}{{cite journal

| last = Arai | first = K.

| year = 2003

| title = Resonance states of ⁵H and ⁵Be in a microscopic three-cluster model

| journal = Physical Review C

| volume = 68 | issue = 3 | pages = 034303

| doi = 10.1103/PhysRevC.68.034303

|bibcode = 2003PhRvC..68c4303A

}}{{cite journal

| last1 = Hemmdan | first1 = A.

| last2 = Glöckle | first2 = W.

| last3 = Kamada | first3= H.

| year = 2002

| title = Indications for the nonexistence of three-neutron resonances near the physical region

| journal = Physical Review C

| volume = 66 | issue = 3 | pages = 054001

| doi = 10.1103/PhysRevC.66.054001

| arxiv=nucl-th/0208007

| bibcode = 2002PhRvC..66e4001H

| s2cid = 11852197

}} and it "does not seem possible to change modern nuclear Hamiltonians to bind a tetraneutron without destroying many other successful predictions of those Hamiltonians. This means that, should a recent experimental claim of a bound tetraneutron be confirmed, our understanding of nuclear forces will have to be significantly changed."

{{cite journal

| last = Pieper | first = S. C.

| year = 2003

| title = Can Modern Nuclear Hamiltonians Tolerate a Bound Tetraneutron?

| journal = Physical Review Letters

| volume = 90 | issue = 25 | pages = 252501

| doi = 10.1103/PhysRevLett.90.252501

| arxiv=nucl-th/0302048

| bibcode=2003PhRvL..90y2501P

| pmid=12857127

| s2cid = 31164554

}}

Further work{{cite journal

| year = 2019

| title = Tetraneutron condensation in neutron rich matter

| last1 = Ivanytskyi | first1 = O.

| last2 = Ángeles Pérez-García | first2 = M.

| last3 = Albertus | first3 = C.

| journal = European Physical Journal A

| volume = 55 | issue = 10| pages = 184

| bibcode = 2019EPJA...55..184I

| arxiv = 1904.11512

| doi = 10.1140/epja/i2019-12900-6 | doi-access = free

}} in 2019 suggests potentially observable consequences in neutron star crusts, if the tetraneutron exists.

In 2016, researchers at RIKEN in Wakō, Japan observed evidence that the tetraneutron exists briefly as a resonance. They fired a beam of neutron-rich helium-8 nuclei (two protons and six neutrons) at a liquid target composed of helium-4 (two protons and two neutrons). Occasionally, the reaction produced beryllium-8 nuclei with four protons and four neutrons, leaving four neutrons unaccounted for. If a four-neutron nucleus did occur, it lasted for about 10⁻²¹ seconds before decaying into other particles.{{Cite news

| title = Physicists find signs of four-neutron nucleus

| last = Grant | first = Andrew

| website = Science News

| url = https://www.sciencenews.org/article/physicists-find-signs-four-neutron-nucleus

| date= 8 February 2016

| access-date = 8 February 2016

}}{{Cite journal

| title = Four neutrons together momentarily

| last1 = Bertulani | first1 = Carlos A.

| last2 = Zelevinsky | first2 = Vladimir

| journal= Nature

| year = 2016 | volume= 532 |issue = 7600 |pages= 448–449

| doi = 10.1038/nature17884 | doi-access = free

| pmid = 27049938

| bibcode= 2016Natur.532..448B

}}{{cite journal

| last1 = Kisamori | first1 = K.

| display-authors= etal

| journal = Physical Review Letters

| title = Candidate Resonant Tetraneutron State Populated by the ⁴He(⁸He,⁸Be) Reaction

| year = 2016

| volume = 116 | issue = 5

| page = 052501

| doi = 10.1103/PhysRevLett.116.052501

| pmid = 26894705

| bibcode = 2016PhRvL.116e2501K

}}

Evidence for unbound clusters of 4 neutrons resonances in the disintegration of beryllium-14 nuclei, in ⁸He-⁸Be interactions, and collisions of ⁴He nuclei give an estimated lifetime around 10⁻²² seconds.{{Cite journal |last1=Duer |first1=M. |last2=Aumann |first2=T. |last3=Gernhäuser |first3=R. |last4=Panin |first4=V. |last5=Paschalis |first5=S. |last6=Rossi |first6=D. M. |last7=Achouri |first7=N. L. |last8=Ahn |first8=D. |last9=Baba |first9=H. |last10=Bertulani |first10=C. A. |last11=Böhmer |first11=M. |last12=Boretzky |first12=K. |last13=Caesar |first13=C. |last14=Chiga |first14=N. |last15=Corsi |first15=A. |date=2022-06-23 |title=Observation of a correlated free four-neutron system |journal=Nature |language=en |volume=606 |issue=7915 |pages=678–682 |doi=10.1038/s41586-022-04827-6 |issn=0028-0836 |pmc=9217746 |pmid=35732764|bibcode=2022Natur.606..678D }}

These discoveries should deepen our understanding of the nuclear forces.{{cite web|url=https://www.sciencenews.org/article/physicists-find-signs-four-neutron-nucleus|title=Physicists find signs of four-neutron nucleus|date=2016-02-24|access-date=2017-06-27|archive-date=2017-07-29|archive-url=https://web.archive.org/web/20170729030228/https://www.sciencenews.org/article/physicists-find-signs-four-neutron-nucleus|url-status=live}}{{cite journal|first=Nigel|last=Orr|title=Can Four Neutrons Tango?|journal=Physics|volume=9|date=2016-02-03|pages=14|doi=10.1103/Physics.9.14|bibcode=2016PhyOJ...9...14O|doi-access=free}}

• Neutronium
• Tetraquark

{{reflist}}

• [https://web.archive.org/web/20021226013002/http://www.cnrs.fr/cw/en/pres/compress/noyau.htm Announcement of possible tetraneutron observations]
• [http://www.ganil.fr/user/news/com/com170402.html Announcement of possible tetraneutron observations] {{Webarchive|url=https://web.archive.org/web/20081125161235/http://www.ganil.fr/user/news/com/com170402.html |date=2008-11-25 }} {{in lang|fr}}
• [https://web.archive.org/web/20160303193644/http://www.cnrs.fr/cw/en/pres/compress/noyau.htm Announcement of possible tetraneutron observations (Internet Archive)]

Category:Hypothetical nuclei

Category:Neutron

Neutronium-4