1 A Search for deeply-bound Kaonic nuclear state at the J-PARC E15 experiment Yuta Sada Kyoto University On behalf of the J-PARC E15 collaboration

2 Contents Introduction KN interaction and Kaonic nuclei J-PARC E15 experiment K - pp bound state by measuring 3 He(K -,n) reaction measuring 3 He(K -,n/p) reaction Current Status Summary

3 KN interaction and Kaonic nuclei K-nucleon interaction  Low energy Kp scattering  Kaonic hydrogen level shift (KEK-PS E228) Kaonic nuclei  Kaon bound states with a few nucleons  There are some experimental result of the simplest Kaonic nuclei (KNN) (FINUDA,DISTO) 3 M.Iwasaki et al., PRL 78, 3067(1997) Strongly attractive (I=0) How strong? To extract the information about KN interaction below KN threshold FINUDA DISTO B = 105±2±5 MeV  = 118±8±10MeV B = 115±6±4 MeV  = 67±14±3 MeV

4 J-PARC E15 experiment Experimental search for KNN bound states using in-flight (K -, N) reaction on 3 He Experimental search for KNN bound states using in-flight (K -, N) reaction on 3 He 4 K-K- 3 He Formation KNN cluster Neutron (proton)  p p -- Mode to decay charged particles Decay Missing mass Spectroscopy via neutron or proton Invariant mass reconstruction We can observe both the “Formation” and “Decay” of KNN bound state (especially K-pp state is important)

5 Formation spectra : in-flight 3 He(K -,n) T.Koike and T.Harada., PLB652 (2007) 262 quasi-free bound K - escape K - conversion K He  “K - pp” + P K =1GeV/c,  =0º YA potential Signal can be clearly seen! Integrated production cross section amounts to ~3.0 mb/sr.

6 TT Tp Tn Signal(DISTO) vs Background(2NA+rescattering) 2NA and s-wave scattering T.Hiraiwa 2010/12/2-4 Strangeness workshop By E15 exp. we will able to see clear signal!!

7 Isospin components of 3 He(K -, n/p) reaction At 3 He(K , n) reaction, there are 2 reaction components (A, B) ->Can not separate A and B experimentally. At 3 He(K , p) reaction, there is only reaction C. And reaction B and C are isobaric analogical. ->To compare with both 3 He(K -, n/p) reactions, We can get the information of isospin dependence of reactions Reaction A Reaction B Reaction C 3 He(K , n) Reaction 3 He(K , p) Reaction

8 Reaction A (K-, n) reaction Reaction B (K-, n) reaction Reaction C (K-, p) reaction bound Theoretical Calculation of （ K -, n/p ） reaction J. Yamagata-Sekihara, D. Jido, H. Nagahiro, and S. Hirenzaki., Phys. Rev. C80, (2009) Calculation of (K-,n/p)KNN missing-mass spectrum Reaction A Reaction BReaction C 3 He(K , n) Reaction 3 He(K , p) Reaction

9 J-PARC E15 experiment  A search for a KNN bound state using in-flight (K -, N) reaction  To measure the missing mass and invariant mass of KNN states at the same time and isospin dependence of reactions ->More comprehensive understanding of KN interaction and Kaonic nuclei!

10 Current Status

11 Experimental Setup 11 J-PARC K1.8BR Neutron counter Beam sweep magnet Cylindrical Detector System Beamline Spectrometer 1.0 GeV/c K - Neutron TOF length 14~15m Proton

12 Liquid 3 He target and Beamline spectrometers Ni target 0.75 GeV/c DC separator ON Development and test of Liquid 3 He target system was already completed!! Now Final K - was successfully identified using TOF method. Hardware trigger for Kaon works very well. Beam tune is under way. 3 He targetBeamline

13 TOF counter x 5 x 150 cm 3 Plastic Scintillator Configuration : 16 (wide) x 7 (depth) Surface area : 3.2m x 1.5m missing mass resolution for K - pp  = 9.2 MeV/c 2 (P n =1.3 GeV/c,  TOF =150 ps) 10 x 3 x 150 cm 3 Plastic Scintillator Configuration : layer missing mass resolution for KNN  = 6.8 MeV/c 2 (P p =1.3 GeV/c,  TOF =100 ps) Neutron Counter Proton Counter

14 Cylindrical Detector System A newly developed system for invariant mass study 14 Expected mass resolution :  -  ~ 3.5 MeV/c 2 for  -  ~ 13 MeV/c 2 for K - pp (  cdc = 200  m / Field : 0.5 T) CDC Hodoscope And Solenoid

15 CDS Current Status Commissioning using secondly beam (   /K  beam 0.9GeV/c) (2010/10/22~10/24) CH 2 (5mm) Cu (1mm) C (5mm) ~40cm 10cm ~4300  Vertex Point Z (very preliminary) Invariant mass(P   ) (very preliminary) CDS works well!! Real Data!

16 Summary J-PARC E15 experiment  search for a KNN bound state using in-flight (K -, N) reaction  To measure the missing mass and invariant mass of KNN states at the same time and isospin dependence of reactions The preparation is well under way.  3 He Target and Beam line spectrometers are almost ready  CDS works well!! Physics data is coming soon!

17 J-PARC E15 Collaboration 17

18 Back up

19 Typical Event Pt=145MeV/c Pt=470MeV/c CDH Target

20  : isospin of KNN  z component of isospin KNN T: isospin of KN subsystem

21 Background?? : two nucleon absorption 21 2NA +  N rescattering /  conversion looks like a “signal” ?? (2NA itself is not a problem.) 2NA is very small 12 C(K 1GeV/c 12 C(K -,p) T. Kishimoto et al., Prog.Theor.Phys. 118(2007)181. De Broglie wave 1 GeV/c ~ 1.2 fm NN distance in 3 He ~ 2.25 fm Proc. Jpn. Academy, Series B83 (2007) 144. These probabilities are expected to be very small... Anyway, let’s see how they look like!

22 Motivation of measuring 3 He(K , n/p) reaction Only 3 He(K , n) reaction channel was E15 exp. →because K - is more attractive proton than neutron, so K - pp is most bounded simply. But isospin components of KNN from 3 He(K , n) reaction is mixed strongly attractive one and another one. only measuring 3 He(K , n) reaction, we can not separate strongly attractive one and another one.  He(K , n) reaction 3 He(K , p) reaction →Both measuring 3 He(K -, n/p) is needed!

23 Background study (two nuclear absorption) 2NA +  N rescattering /  conversion looks like a “signal” ?? (2NA itself is not a problem.) 2NA+  N rescattering2NA+  conversion

24 Background study 2(Dalitz ’ s plot) Signal can be distinguished between background !!

25 Identification of  pn final state by CDS & NC 2010/12/2-4 ストレンジネス研究会 Possible background -  0 pn final state +  missing - QF-  +  missing - QF- ,  conv. +  missing Other processes can be clearly separated!!

26 Solenoid magnet Field strength : 0.5 T (maximum field : 0.7 T) Aperture : 1.2 m Length : 1.2 m June 2010meson Characteristic curve (B vs A) current [A] Field strength [T] Performance Excitation test have been performed in May Design value (max field : 0.7T) was successfully achieved!

27 Liquid 3 He target June 2010meson Temperature in the Target Cell 1.3 K Pressure in the Target Cell 33 hPa Liq. 4 He Consumption 45 L/day Heat Load to the 1K Parts 0.19 W Cooling test with 200L 3 He gas Calculation Development and test of Liquid 3 He target system was already completed!!

28 What are needed to measure 3 He(K -,p) Drift chambers are for knowing the reaction point TOF start and TOF wall for proton are for measuring to TOF( time of flight) of flight proton Glass TIR is talk the next slide in detail

29 Cylindrical Detector Hodoscope (CDH) 29 Plastic scintillation counters for trigger and PID Size : 99 x 30 x 700 mm 3 (W x T x L) Configuration : 36 modules PMT : fine-mesh type (H8409) Cosmic-ray test  int = /- 2.9 ps Intrinsic time resolution ~ 71 ps

30 Cylindrical Drift Chamber (CDC) Size  Inner diameter : 300 mm  Outer diameter : 1060 mm  Length : 950 mm Cell  Hexagonal (Drift length~9mm) Layer  15 layers (7 super layers) AA’A UU’ VV’ AA’ UU’ VV’ AA’ Read out : 1816 ch Gas : Ar-C 2 H 6 (50:50) Efficiency curve Using 90 Sr 30 Efficiency of >99% was achieved for all layers using 90 Sr.

31 Theoretical study on K - pp K - pp bound states should exist! K - pp bound states should exist!  A deep state or shallow state?  Decay width is sufficiently narrow? June 2010meson B.E [MeV]  [MeV] Method Yamazaki and Akaishi (mesonic) Variational Method (ATMS) Shevchenko, Gal, and Mares (mesonic) Coupled Channel Faddeev Calculation Ikeda and Sato (mesonic) Coupled Channel Faddeev Calculation Nishikawa and Kondo ~126Skyrme Model Dote, Hyodo, and Weise 20±3 (s-wave) (mesonic) Chiral SU(3) Variational Method Arai, Oka, and Yasui depend on g Λ*Λ*σ Variational Method (as Λ*p state)

32 Plan of CDS commissioning Commissioning by using Cosmic Ray  Test of Solenoid Magnet Test of CDC in Magnetic Field  Momentum Reconstruction  Efficiency, Resolution   Pt/Pt Commissioning by Secondly beam  p elactic scattering (monochromatic beam)  Check of Pt Resolution by defined momentum Invariant mass of K 0 s and   Check of Mass resolution and peak position

33 Cosmic Ray Data Test of Solenoid magnet and taking data of Cosmic ray Amount of data  field -0.5T (+ beam direction)  2010/5/20~5/28 total 35hour ~500,000 event  filed +0.5T  2010/8/30~9/4 25hour ~400,000 event Characteristic curve (B vs A) Current [A] Field strength [T] Achieved Design value ! (max field : 0.7T)

34 CDC Efficiency Achieved Average 99% over! Efficiency Layer definition Eff= Num of Hit of the layer / Num of Reconstructed Track （ hit is in cell size) （ without the layer of measurement ）

35 XTCurve Axial Layer (Layer 1) Stereo Layer (Layer 4)

Residual [m] Layer AxialStereoAxialStereoAxial Residual of Hit Position Achived 200~350  m To get Intrinsic resolution, Need to comparie with Simulation =209m Residual (Layer1) Residual [m] Result of liner track

37 Data with Secondly beam     beam  (0.9GeV/c) for  p elastic scattering To check Pt resolution    beam  (0.9GeV/c) for Invariant mass of  and K 0 s To check mass resolution and peak point Total time [h] Integrated Trigger Trigger  + (0.9GeV/c) ×10 6  trigger× CDH1hit K  (0.9GeV/c) ×10 6 K trigger× CDH2hit MaterialSize[mm]Thickness [mm](g/cm 2 ) Position [mm] Polyethylene500×5005.0(0.50)+420 C500×5005.0(0.90)+50 Cu300×3001.0(0.90)-50 Secondly beam Set up Target