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Motivation for the search for double kaonic nuclear cluster by antiproton annihilation in 3 He

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Search for Double Antikaon Production in Nuclei by Antiproton AnnihilationP. Kienle, Excellence Cluster Universe, TU München

Motivation for the search for double kaonic

nuclear cluster by antiproton annihilation in 3He

Stopped antiproton annihilation in 3He@ J-PARC

1 GeV/c antiproton annihilation in 3He@ J-PARC

Comparison of stopped and 1 GeV/c antipro-

ton annihilation in 3He

Possibility of “Double-Kaonic

Nuclear Cluster” Production

by Stopped-pbar Annihilation

Prelude to „Double-Strange Nuclei“ @ LEAP

W. Weise, arXiv: 0507.058 (nucl-th) 2005

P. Kienle, J. Mod. Phys., A22 (2007) 365

P. Kienle, J. Mod. Phys., E16 (2007) 905

↔

T. Yamazaki, M. Maggiora, P. Kienle, K. Suzuki et al.

- Properties: p+p -> K+ +X @ momentum transfer ~1.6 GeV/c
- MX = 2.267 (3) GeV/c² -> BX = 103(3) MeV
- ΓX = 118(8) MeV/c²
- Assigned to deeply bound, dense K-pp cluster with Bx about twice the value predicted by AY
- High observed production probability is predicted by the AY reaction model for the case of a high density cluster X
- 25% of interaction strength is missing by AY
- Consequences for Double Strange Cluster
- Higher binding energy and higher density expected compared with single strange cluster
- The annihilation process produces high energy and momentum density favoring formation of
- K-K-pp cluster.

- Double-kaonic nuclear clusters have been predicted theoretically.
- Double-kaonic clusters are expected to have a stronger binding
- energy and a higher density than single ones.
- From B(K-pp)= 103 MeV one extrapolates B(K-K-pp)~200 MeV

PL,B587,167 (2004). & NP, A754, 391c (2005).

- How to produce the double-kaonic nuclear cluster?
- heavy ion collision
- (K-,K+) reaction
- pbarA annihilation

We use pbarA annihilation

The elementary pbar-p annihilation reaction:

-98MeV

is forbidden for stopped pbar,

because of a negative Q-value of 98MeV

However, if deeply bound multi kaonic nuclear clusters exist, production by pbar annihilation reactions will be possible!

theoretical

prediction

B.E.=117MeV

G=35MeV

B.E.=221MeV

G=37MeV

Observations of the double-strangeness production in stopped pbar annihilation have been reported by 2 groups only, DIANA@ ITEP and OBELIX@ CERN/LEAR.

Although the observed statistics is very low,

their results have indicated a high yield of ~10-4

Monte Carlo studyfor pbar+3He reactions at rest and at 1GeV/c antiproton momentum

2010/03

F. Sakuma

Monte Carlo study using GEANT4 toolkit

- The K-K-pp acceptance is calculated for B.E. =120, 150 and 200MeV
- Decay widths of K-K-pp is to be 100MeV
- Many-body decay modes of the pbar+3He reactions are considered to be isotropic and proportional to the phase space.
- Particles are generated at the center of the detector system (0,0,0).
- Decay-particle momenta are reconstructed by helix fitting, and K0Sp+p-, Lpp-, LL mass and decay vertex are obtained.
- branching ratios of K0S/L are included correctly.
- energy losses are NOT corrected.
- In this study, acceptance is defined by track fitting. (i.e., CDH is NOT used in the E15 setup)

- Possible backgrounds for LL invariant-mass spectroscopy:
- stopped-pbar + 3He K0S + K+ + K-K-pp
- L + L
- stopped-pbar + 3He K0S + K+ + K-K-pp
- L + S0
- stopped-pbar + 3He K0S + K+ + K-K-pp
- S0 + S0
- stopped-pbar + 3He K0S + K+ + K-K-pp
- L + L + p0
- …
- stopped-pbar + 3He K0S + K+ + L + L
- …

K-K-pp production

missing g

missing 2g

missing p0

phase space

- Possible backgrounds for K0SK+ missing-mass (w/ L) spectroscopy:
- stopped-pbar + 3He K0S + K+ + K-K-pp
- L + L
- stopped-pbar + 3He K0S + K+ + L + L
- stopped-pbar + 3He K0S + K+ + S0 + S0 + p0
- …
- stopped-pbar + 3He K0S + K+ + K0 + S0 + (n)
- stopped-pbar + 3He K0S + K+ + K- + S0 + (p)
- …

K-K-pp production

3N annihilation

2N annihilation

stopped-pbar + 3He K0S + K+ +X [X<2755MeV]

Solenoid setup E15

setup

- B = 0.5T
- CDC resolution : srf = 0.2mm
- sz’s depend on the tilt angles (~3mm)
- ZTPC resolution : sz = 1mm
- srf is not used for present setup
- target system
- liquid 3He
- TARGET_CHM_RMAX = 75.0mm
- TARGET_RMAX = 35.0mm
- TargetLength = 120.0mm
- ThicknessOfTgtCell = 0.3mm (PET)
- ThicknessOfTgtAl = 0.6mm
- ThicknessOfTgtCFRP = 1.0mm

Acceptance for K-K-pp by antiproton at rest and 1GeV/c in 3He

yield (stopped)

- pbar beam momentum : 0.65GeV/c
- beam intensity : 3.4x104/spill/6s @ 270kW
- pbar stopping rate : 3.9%

- stopped-pbar yield : 1.3x103/spill/6s

we assume K-K-pp production rate = 10-4

K-K-pp production yield = 1.3x104 /week @ 270kW

DAQ & ana efficiency = 0.7

expected K-K-pp yield = 9.4x103 /week @ 270kW

w/o detector acceptance

yield (1GeV/c)

- pbar beam momentum : 1GeV/c
- beam intensity : 6.4x105/spill/6s @ 270kW

we assume K-K-pp production rate = 10-4 for 1GeV/c pbar+p (analogy from the DIANA result of double-strangeness production although the result are from pbar+131Xe reaction)

inelastic cross-section of 1GeV/c pbar+p is (117-45) = 72mb

K-K-pp production CS = 7.2mb for 1GeV/c pbar+p

L3He parameters: * r = 0.08g/cm3

* l = 12cm

- N = s * NB * NT
- N : yield
- s : cross section
- NB : the number of beam
- NT : the number of density per unit area of the target

K-K-pp production yield = 8.9x104 /week @ 270kW

DAQ & ana efficiency = 0.7

expected K-K-pp yield = 6.2x104 /week @ 270kW

w/o detector acceptance

- expected yield w/ detector acceptance ([email protected]) with the assumptions:
- K-K-pp production rate = 10-4 for both stopped & 1GeV/c pbar
- BR(K-K-ppLL) = 100%

Spectrum simulation

expected spectrum ([email protected]) with the assumptions:

- production rate:
- K-K-pp bound-state = 10-4
- K-K-LL phase-space = 10-4
- K+K0S0S0p0 phase-space = 10-4
- K+K0K0S0(n) phase-space = 10-4
- K+K0K-S0(p) phase-space = 10-4

- branching ratio of K-K-pp:
- BR(K-K-ppLL) = 0.1
- BR(K-K-ppLS0) = 0.1
- BR(K-K-ppS0S0 = 0.1
- BR(K-K-ppLLp0) = 0.7

K+K0 missing mass (semi-inclusive) = K+K0 missing mass w/ L

exclusive = K+K0LL detection

LL invariant mass (inclusive)

LL invariant mass (exclusive)

# of K-K-ppLL =

# of K-K-ppLL =

stopped pbar

B.E=200MeV,

G=100MeV

K+K0 missing mass (semi-inclusive)

K+K0 missing mass (exclusive)

# of K-K-pp =

# of K-K-pp =

LL invariant mass (inclusive)

LL invariant mass (exclusive)

# of K-K-ppLL =

# of K-K-ppLL =

1GeV/c pbar

B.E=200MeV,

G=100MeV

K+K0 missing mass (semi-inclusive)

K+K0 missing mass (exclusive)

# of K-K-pp =

# of K-K-pp =

dipole setup

setup

- B = 0.5T
- wire chamber is used for INC, and the same layer-design of the E15-CDC is used
- the same layer-design of the E15-CDC is used for new CDC
- the E15 target system is used
- INC resolution : srf = 0.2mm , sz = 2mm (UV)
- CDC resolution : srf = 0.2mm, sz = 2mm (UV)
- CDC is NOT used for the following analysis

acceptance

yield

- expected yield w/ detector acceptance ([email protected]) with the assumptions:
- K-K-pp production rate = 10-4 for both stopped & 1GeV/c pbar
- BR(K-K-ppLL) = 100%

comparison of the yield between the E15 setup and the dipole

stopped

1 GeV/c

spectrum

expected spectrum ([email protected]) with the assumptions:

- production rate:
- K-K-pp bound-state = 10-4
- K-K-LL phase-space = 10-4
- K+K0S0S0p0 phase-space = 10-4
- K+K0K0S0(n) phase-space = 10-4
- K+K0K-S0(p) phase-space = 10-4

- branching ratio of K-K-pp:
- BR(K-K-ppLL) = 0.1
- BR(K-K-ppLS0) = 0.1
- BR(K-K-ppS0S0 = 0.1
- BR(K-K-ppLLp0) = 0.7

K+K0 missing mass (semi-inclusive) = K+K0 missing mass w/ L

exclusive = K+K0LL detection

LL invariant mass (inclusive)

LL invariant mass (exclusive)

# of K-K-ppLL =

# of K-K-ppLL =

stopped pbar

B.E=200MeV,

G=100MeV

K+K0 missing mass (semi-inclusive)

K+K0 missing mass (exclusive)

# of K-K-pp =

# of K-K-pp =

LL invariant mass (inclusive)

LL invariant mass (exclusive)

# of K-K-ppLL =

# of K-K-ppLL =

1GeV/c pbar

B.E=200MeV,

G=100MeV

K+K0 missing mass (semi-inclusive)

K+K0 missing mass (exclusive)

# of K-K-pp =

# of K-K-pp =

Conclusion

- The expected K-K-pp yield with 1GeV/c pbar-beam is several times larger than the yield with stopped-pbar.
- LL invariant mass measurement seems to be difficult whether performed with stopped-pbar or 1GeV/c pbar-beam.
- K+K0 missing mass measurement is suitable for the K-K-pp search both with stopped-pbar and 1GeV/c pbar-beam.
- However, the following still remains to be discussed
- production yield of the K-K-pp and the BGs
- production mechanism of the K-K-pp in the pbar+3He reaction, especially in the in-flight reaction.