Kaonic Nuclei Possibility of doublekaonic nuclear cluster KKpp
Kaonic Nuclei Possibility of double-kaonic nuclear cluster, “K-K-pp”, search using p+p reaction @ high-p BL F. Sakuma, RIKEN Workshop on "Physics with General Purpose Spectrometer in the High-momentum Beam Line" 1 27 -28 August 2018, Research Center for Nuclear Physics (RCNP)
Kaonic Nuclei l Bound states of nucleus and anti-kaon l Predicted as a consequence of attractive Kbar. N interaction in I=0 Meson properties change in nuclear media? Y. Akaishi & T. Yamazaki, PLB 535, 70(2002). 0 1 2 3 l Will provide new insight on Kbar. N interaction in media 2
High-Density Matter? Kaonic Nuclei Binding Energy [Me. V] Width [Me. V] Central Density K-p 27 40 3. 5 r 0 K-pp 48 61 3. 1 r 0 K-ppp 97 13 9. 2 r 0 K-ppn 118 21 8. 8 r 0 Y. Akaishi and T. Yamazaki, PRC 65(2002)044005. A. Dote et al. PRC 70(2004)044313. etc. • Deep binding-energy compact state? high density? • Narrow width Metastable state? c. f. Nuclear Binding Energy a few Me. V/nucelon @ A = 2, 3 3
Present Status of Kbar. NN = “K-pp” Kbar. NN is symbolically notated as “K−pp” in this talk p - d K + X pp K+X stopped K- Chiral complicated reactions Phenomenological “in-flight K-” induced reaction Upper limits were also obtained: • LEPS@SPring 8 [Inclusive d(g, K+p-)X] • HADES@GSI [Exclusive pp p. LK+] 4
J-PARC E 15 Experiment • 3 He(in-flight K-, n) reaction @ 1. 0 Ge. V/c – 2 NA processes and Y decays can be discriminated kinematically 5
“K-pp” Search @ K 1. 8 BR 6
Experimental Setup @ K 1. 8 BR m 15 7
3 He + K- L p n Selection E 15 collab. , ar. Xiv: 1805. 12275 • L p-p and p are detected with CDS – A missing neutron is identified by missing-mass of 3 He(K-, Lp)n • Lpnmiss events are selected by log-likelihood method (ln. L) – distance-of-closest-approach for each vertex – kinematical constraint 8
IM(Lp) vs. Momentum Transfer q. Kn E 15 collab. , ar. Xiv: 1805. 12275 IM(Lp) • Seems to consist of 3 components – Bound state • centroid NOT depend on q. Kn – Qasi-elastic K- abs. q. Kn=q. Lp • centroid depends on q. Kn – Background • Broad distribution 9
IM(Lp) vs. Momentum Transfer q. Kn E 15 collab. , ar. Xiv: 1805. 12275 IM(Lp) • Fit with 3 components – Bound state • centroid NOT depend on q. Kn • BW*(Gauss form-factor) – Qasi-elastic K- abs. q. Kn=q. Lp * We conduct the fitting in each 2 D bin • centroid depends on q. Kn • Followed by Lp conversion – Background • Broad distribution 10
“K-pp” Bound-State Select 0. 35<q. Kn<0. 65 Ge. V/c – BS and QF are well separated E 15 collab. , ar. Xiv: 1805. 12275 11
“K-pp” Bound-State Fit values that reproduce the spectrum: E 15 collab. , ar. Xiv: 1805. 12275 12
Present Status of “K-pp” p - d K + X K-3 He n. X pp K+X stopped K- Chiral Phenomenological For further understandings: ü L(1405) production L*N doorway ü p. SN decay channel new info. of Kbar. NN 13
Present Status of “K-pp” p - d K + X In the E 15 experiment, we have observed a very strong candidate of the “K-pp” bound-state pp K+X K-3 He n. X stopped K- Chiral Phenomenological Then, how about two K, “K K pp”? For further understandings: ü L(1405) production L*N doorway ü p. SN decay channel new info. of Kbar. NN 14
Double-Kaonic Nuclear Cluster ppn The double-kaonic nuclear clusters have been also predicted theoretically. • much stronger binding energy • much higher density ppn. K- PL, B 587, 167 (2004). ppn. K-K- How to produce the double-kaonic nuclear cluster? Øheavy ion collision Ø(K-, K+) reaction Øpbar. A annihilation J-PARC Lo. I @ K 1. 8 BR another choice, p+p collision 15
Experimental Principle 8 Ge. V production decay the produced K-K-pp can be identified: l missing-mass DM(K+K+) l invariant-mass M(LL) Exclusive measurement is desirable, as in case of “K-pp” 16
“K-K-pp” Search @ high-p 2 nd-target 17
8 -10 Ge. V Proton-Yield @ high-p 2 nd-target Prof. Noumi If yield of proton is assume to be as same as that of pion, ~108 proton/spill is expected with pp~8 -10 Ge. V 18
Production-Yield Estimation • CS : s. K-K-pp ~ 0. 5 nb (very “optimistic” assumption) • Beam : 8 Ge. V proton 108 / 6 s x 1 month (30 d) ~ 5 x 1013 • Target : LH 2 target 0. 85 g/cm 2 ( 0. 0708 g/cm 3 12 cm) K-K-pp ~ 104 / month 19
Kinematics K+ [momentum vs. cos(qlab)] B. E = 200 Me. V All decay particles concentrate in forward region (~0. 9<cosq) p- from L L [momentum vs. cos(qlab)] p from L 20
Experimental Requirements • Forward tracking-system – ~0. 9 < cosq – need high-rate detectors • Forward K-ID detector – ~1 < p < ~4 Ge. V/c – p/K separation n~1. 008 • Trigger-level selection OR Trigger. Less DAQ – Usage of n~1. 008 aerogel? 21
with the E 16 -like Setup? E 16 spectrometer + hadron-spectrometer with 108 ppp +15 -15 +45 +15 -45 e+e- acceptance K+K- acceptance 22
(degree) Kinematics of Decay-Particles generated events K+ B. E = 200 Me. V detector acceptance (degree) p- p 23
(degree) + + p(p, K K )X Acceptance double-K+ accepted (~16%) K+ B. E = 200 Me. V (degree) p- p 24
(degree) p(p, LL)X Acceptance double-L accepted (~0. 7%) K+ B. E = 200 Me. V (degree) p- p 25
(Very Rough) Yield Estimation double-K+ accepted event acceptance ~ 16% ~ 1000 / mon double-L accepted event acceptance ~ 0. 7% ~ 10 / mon ü LL decay : 100% K+ [mom vs. cos(qlab)] K+ p- from L [mom vs. cos(qlab)] p- from L p from L [mom vs. cos(qlab)] Hard to perform the exclusive measurement with the E 16 -like setup 26
Would be feasible with the E 50 Spectrometer Prof. Noumi RICH & Trigger-Less DAQ is essential! 27
Summary • Strong candidate of “K-pp” has been observed in E 15 – Existence of double kaonic-nuclear-cluster, “K-K-pp”, is also expected • “K-K-pp” search with 8 -10 Ge. V proton beam is discussed. – 8 Ge. V p+p K++K++”K-K-pp” K++K++L+L – Exclusive measurement is desirable • Requirements for detectors are: – Forward tracking-system (~0. 9<cosq) – Forward K-ID detector (~1<p. K<~4 Ge. V/c) • With the E 16 -like setup, it seems to be difficult to perform the exclusive measurement E 50 spectrometer? 28
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expected K K pp cross-section • The free L production CS in p+p collision is known to be s. L ~ 10 -3 x stotal ~ 50 mb • The free L* production CS at 2. 83 Ge. V is known to be s. L* ~4. 5 mb ~ 0. 1 x s. L • The double-L production CS is expected to be s. L+L ~ 0. 001 x s. L ~ 50 nb (= 10 -3 x stotal) • Thus, the double-L* production CS is expected to be s. L*+L* ~ 0. 01 x s. L+L ~ 0. 5 nb • The DISTO result indicates the K-pp production CS is as much as L* production CS, so we simply assume K-K-pp production CS to be s. K-K-pp ~ s. L*+L* ~ 0. 5 nb Of course, these are very rough estimations and depend on incident energy 30
Kaon identification K+ [mom vs. cos(qlab)] n=1. 02 however, proton contamination is … ? ? ? 31
Past Experiment … KEK-PS E 248 (AIDA) 12 Ge. V p+p K++K++X 32
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