Challenges in Searching for DD* Dimesons
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Talk presented at the
Mini-Workshop BLED
,
17-23 June,
201
8
D
O
U
B
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-
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M
B
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S
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D
D
I
M
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S
O
N
S
Janc & Rosina : (DD*) – (D + D*) = - 0.6 MeV (Bhaduri )
- 2.7 MeV (Grenoble AL1)
What is a promissing production and detection
mechanism?
1
.
M
O
T
I
V
A
T
I
O
N
1.
Effective quark-quark interaction:
Is Vuu = Vcu = Vcc = Vcc
= Vbu = Vbb
= Vbb
(apart from the mass-dependent spin-spin term) ?
2.
Interesting 4-body problem,
t
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B
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=
(
b
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+
b
d
)
@
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*
=
(
c
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+
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)
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c
c
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V
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cc
D + D*
c
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+
d
b
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r
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O
r is the first step to form D
+
D* which merge into DD*.The
later choice can profit from resonance formation, but due to
ther dense environement it is a danger that
the
D
+
D*
system
would again
dissociate before really forming the dimeson.
3
.
T
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-
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1.step: double two-gluon fusion
(g + g) + (g + g) (c + c) + (c + c)
2.step: two c fly close enough in phase space
(c + c) cc [colour antisymmetric diquark]
3.step: the diquark cc gets dressed, cc
ccu or
ccud.
c
c
u
d
e
c
a
y
s
w
e
a
k
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y
(
c
s
)
:
Ξ
c
c
Λ
c
4.step: dimeson forms, cc u d cu cd = D D*
5.step: D* D
γ
electromagnetic decay
or D* D
π
(slow strong decay due to small phase space)
T
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Fermilab CDF 2000
Acording to this speculation, the yield of the tetraquark
systems
ccud
should be as much as ¼ compared to ccu.
However, the atomic-like
cc
+
u
+
d
is almost 100 MeV
above the D + D* threshold and would decay mostly into
two free mesons.
The question remains, whether it will
decay copiously enough through the DD* bound state
or resonance which we are searching for.
The question also remains how to distinguish such
resonance process by analysing the decay products.
T
h
e
e
s
t
i
m
a
t
e
o
f
t
h
e
d
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u
a
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f
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(
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o
,
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c
,
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o
s
i
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a
T
r
e
l
e
a
n
i
2
0
0
5
)
We make an impulse approximation that this two-
quark state is instantaneously transformed in any of the
27 nb (LHCb) ; 58 nb (ALICE)
4.
The production of
dimesons @ Belle & Belle2
B
e
l
l
e
t
i
l
l
n
o
w
:
1
a
b
15% below, 50% at, 35% above Y(4s)
Total
σ
~ 1 nb
σ
(J/
ψ
X) ~ 1pb
σ
(
J
/
ψ
c
c
)
~
0
.
5
p
b
[
m
o
s
t
l
y
J
/
ψ
η
c
]
σ
(DD) < 1pb
Inclusive Production of Four Charm Hadrons
in e
+
e
−
Annihilation at B Factories
Daekyoung Kang, Jong-Wan Lee, and Jungil Lee
Department of Physics, Korea University, Seoul 136-701, Korea
PRD71 (2005) 071501(R)
E
0
=10.6GeV
Q
q
A SIMPLIFIED
ESTIMATE
In order to understand
why
σ
~ picobarn
Q
=
1
0
G
e
V
,
m
c
=
1
.
5
G
e
V
α
=
1
/
1
3
7
,
α
s
=
0
.
2
ε
,p
Assume:
5
. The
decay of the dimeson
DD
* detection
or:
D
0
*
D
0
+
γ
+
1
4
2
M
e
V
D
+
*
D
+
+
γ
+
1
4
1
M
e
V
D
D
*
D
+
D
+
γ
+
~
1
4
0
M
e
V
(65 %)
(35 %)
(67 %)
(31 %)
(2 %)
The search for DD* dimesons involves analyzing effective quark-quark interactions, exploring production mechanisms, and understanding the formation of double-charm baryons. Challenges lie in dressing quarks, optimizing production in colliders, and speculating on fragmentation processes. The potential of tetraquark systems is compared, raising questions on decay thresholds and resonance formation.
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Presentation Transcript
MOTIVATION AND POSSIBLE CHANNELS FOR THE SEARCH OF THE DD* DIMESON Mitja Rosina Faculty of Mathematics and Physics, University of Ljubljana and Institute Jo ef Stefan, Ljubljana, Slovenia Talk presented at the Mini-Workshop BLED, 17-23 June, 2018 DOUBLE-CHARM BARYONS AND DIMESONS Janc & Rosina : (DD*) (D + D*) = - 0.6 MeV (Bhaduri ) - 2.7 MeV (Grenoble AL1) What is a promissing production and detection mechanism?
1. MOTIVATION 1. Effective quark-quark interaction: Is Vuu = Vcu = Vcc = Vcc = Vbu = Vbb = Vbb (apart from the mass-dependent spin-spin term) ? 2. Interesting 4-body problem, to understand binding and to forsee the production and detection mechanisms. CHALLENGE: New chances to measure BB*=(bu+bd) @ LHC and DD*=(cu+cd) at the upgraded Belle-2 @ KEK (Tsukuba, Japan).
2. COMPARISON BETWEEN DIMESON AND HYDROGEN MOLECULE POTENTIAL V rcc u cc D + D* c c c d
It is an interesting question whether in the first step "cc" diquark is formed and later automatically dressed by u or d or ubar+dbar. Or is the first step to form D + D* which merge into DD*.The later choice can profit from resonance formation, but due to ther dense environement it is a danger that the D + D* system would again dissociate before really forming the dimeson.
3. The production of ccu baryons and dimesons in p-p colliders 1.step: double two-gluon fusion (g + g) + (g + g) (c + c) + (c + c) 2.step: two c fly close enough in phase space (c + c) cc [colour antisymmetric diquark] 3.step: the diquark cc gets dressed, cc ccu or ccud. ccu decays weakly (c s): cc c 4.step: dimeson forms, cc u d cu cd = D D* 5.step: D* D electromagnetic decay or D* D (slow strong decay due to small phase space)
The dressing (fragmentation) of the b quark b B- B0 Bs b = bu = bd = bs = bud .. 0.375+0.015 .. 0.375+0.015 .. 0.160+0.025 .. 0.090+0.028 Fermilab CDF 2000 WE SPECULATE: The dressing (fragmentation) of the cc diquark cc = ccu = ccd = ccs =ccud .. 37 % .. 37 % .. 16 % .. cc++ cc+ cc+ T cc+ 9 %
Acording to this speculation, the yield of the tetraquark systems ccud should be as much as compared to ccu. However, the atomic-like cc+u+d is almost 100 MeV above the D + D* threshold and would decay mostly into two free mesons. The question remains, whether it will decay copiously enough through the DD* bound state or resonance which we are searching for. The question also remains how to distinguish such resonance process by analysing the decay products.
The estimate of the diquark formation (Del Fabro, Janc, Rosina Treleani 2005) We make an impulse approximation that this two- quark state is instantaneously transformed in any of the 27 nb (LHCb) ; 58 nb (ALICE)
4. The production of dimesons @ Belle & Belle2 Belle till now: 1 ab 15% below, 50% at, 35% above Y(4s) Total ~ 1 nb (J/ X) ~ 1pb (J/ cc) ~ 0.5 pb [mostly J/ c] (DD) < 1pb
Inclusive Production of Four Charm Hadrons in e+e Annihilation at B Factories Daekyoung Kang, Jong-Wan Lee, and Jungil Lee Department of Physics, Korea University, Seoul 136-701, Korea PRD71 (2005) 071501(R) E0=10.6GeV
A SIMPLIFIED ESTIMATE In order to understand why ~ picobarn Q=10 GeV, mc=1.5 GeV = 1/137, s = 0.2 Q q ,p Assume:
5. The decay of the dimeson DD* detection (65 %) (67 %) (31 %) or: D0* D0 + + 142 MeV D+* D+ + + 141 MeV (35 %) (2 %) DD* D + D + + ~140 MeV
