晶格量子色动力学的氘核重双链体
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Deuteronlike Heavy Dibaryons from Lattice Quantum Chromodynamics
Parikshit Junnarkar
*
and Nilmani Mathur
†
Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 40000 5, India
(Received 1 July 2019; revised manuscript received 16 August 2019; published 18 October 2019)
We report the first lattice quantum chromodynamics (QCD) study of deuteronlike (np-like) dibaryons
with heavy quark flavors. These include particles with the following dibaryon structures and valence qua rk
contents: Σ
c
Ξ
cc
ðuucuccÞ, Ω
c
Ω
cc
ðsscsccÞ, Σ
b
Ξ
bb
ðuububbÞ, Ω
b
Ω
bb
ðssbsbbÞ, and Ω
ccb
Ω
cbb
ðccbcbbÞ,
and with spin (J) parit y (P), J
P
≡ 1
þ
. Using a state-of-the art lattice QCD calculation, after controlling
relevant systematic errors, we unambiguously find that the ground state masses of dibaryons
Ω
c
Ω
cc
ðsscsccÞ, Ω
b
Ω
bb
ðssbsbbÞ, and Ω
ccb
Ω
cbb
ðccbcbbÞ are below their respective two-baryon thresh-
olds, suggesting the presence of bound states that are stable under strong and electromagnetic interactions.
We also predict their masses precisely. For dibaryons Σ
c
Ξ
cc
ðuucuccÞ, and Σ
b
Ξ
bb
ðuububbÞ, we could not
reach to a definitive conclusion about the presence of any bound state due to large systematics associated
with these states. We also find that the binding of these dibaryons becomes stronger as they become heavier
in mass. This study also opens up the possibility of the existence of many other exotic nuclei, which can be
formed through the fusion of heavy baryons, similar to the formation of nuclei of elements in the periodic
table.
DOI: 10.1103/PhysRevLett.123.162003
A deuteron is a bound state of two baryons, a proton and
a neutron, and is made of six light valence quarks. In the
early Universe, deuterons were created and their stability is
responsible for the creation of other elements. Interestingly,
the strong interactions between quarks, which bring sta-
bility to deuterons, also allow various other six-quark
combinations leading to the possible formation of many
other dibaryons. However, no such strong-interaction-
stable dibaryons, though speculated about many times
[1–8], have been observed yet [9]. Using a state-of-the-
art first principles calculation of lattice quantum chromo-
dynamics (QCD), here we report, for the first time, a
definite prediction of the existence of other deuteronlike
spin-1 dibaryons. We also predict their masses precisely.
These new subatomic particles could either be made of
six heavy quarks (charm and bottom) or heavy and strange
quarks. Such dibaryons are stable against strong and
electromagnetic decays, but, unlike the deuteron, they
can decay through weak interactions. We also find that
such dibaryons become more strong-interaction stable as
they become heavier. We expect that prediction from this
calculation will initiate more theoretical works on heavy
dibaryons, particularly to understand their binding mecha-
nism, and may as well aid in discovering these new
subatomic particles at future experimental facilities, such
as at the upgraded Large Hadron Collider and future high
energy heavy ion facilities. In fact this study opens up the
possibility of the existence of many other exotic nuclei,
which can be formed through the fusion of heavy baryons,
similar to the formation of nuclei of elements in the
periodic table. Formation of these hadrons perhaps also
enhances the possibility of a quark-level analog of nuclear
fusion as discussed recently [10]. Further study of these
exotic states can also provide information on the strong
interaction dynamics at multiple scales.
The particular dibaryons (D) [We identify the two-flavor
spin-1 dibaryons with the symbol D and name them as D
q
1
q
2
,
which are made of two baryons with valence quark contents
ðq
1
q
1
q
2
Þ and ðq
1
q
2
q
2
Þ. In this notation the deuteron is
D
ud
≡ npðuududdÞ. Such dibaryons may be called as D
dibaryons.], which we investigate, are heavy quark analogs
of deuteron (np). They have the spin-(J) parity (P) quantum
numbers: J
P
¼ 1
þ
, with the following dibaryon configura-
tions: D
cu
≡ Σ
c
Ξ
cc
ðuucuccÞ, D
cs
≡ Ω
c
Ω
cc
ðsscsccÞ, D
bu
≡
Σ
b
Ξ
bb
ðuububbÞ, D
bs
≡ Ω
b
Ω
bb
ðssbsbbÞ, and D
bc
≡
Ω
ccb
Ω
cbb
ðccbcbbÞ. Here, Σ
q
; Ξ
qq
; Ω
qq
; Ω
q
1
q
2
q
2
’s are heavy
baryons with the usual nomenclature of the Particle Data
Group [11],andu, s, c, b inside brackets are various quark
flavors. We find that D
cs
, D
bs
,andD
bc
are stable against
strong and electromagnetic decays, and thus it will be
interesting to carry out further theoretical studies on their
binding mechanisms as well as their production mechanisms.
However, for D
cu
and D
bu
, we find the ground state masses
are consistent with their respective two-baryon thresholds,
and therefore our results are not currently precise enough to
Published by the American Physical Society under the terms of
the Creative Commons Attribution 4.0 International license.
Further distribution of this work must maintain attribution to
the author(s) and the published articl e’s title, journal citation,
and DOI. Funded by SCOAP
3
.
PHYSICAL REVIEW LETTERS 123, 162003 (2019)
0031-9007=19=123(16)=162003(6) 162003-1 Published by the American Physical Society
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