Nuclear Physics studied by Neutrino induced Coherent Pion Production

Transcription

1 Nuclear Physics studied by Neutrino induced Coherent Pion Production Yasuhiro SAKEMI Research Center for Nuclear Physics (RCNP) Osaka University Motivation from the point of view of nuclear physics.

2 Neutrino-Nucleus scattering 1. Neutrino oscillations ~ Detector response. Hadron physics ~ Spin structure of nucleon 3. Input into Astrophysics ~ Core collapse supernovae, r-process nucleosynthesis 4. Nuclear physics ~, propagation in the interior of nucleus

3 Physics motivation New probe ~ neutrino Physics ~ search of nuclear interior, property of high density nuclear matter pion, propagation in the nuclear medium ~ Chiral symmetry in nuclear physics Nuclear force ~ short range component condensation Nucleus, propagation ~ pions in nuclei surface pion condensation Nuclear Force: V(r) (MeV) Region Region Region Nuclear Force V( 1 S 0 ) Pion compton wavelength ~ Nuclear force range Temperature : T Phase Transition Tc = 00 MeV RHIC & LHC Quark-Gluon Plasma Deconfinement & Chiral transition Distance: r (fm) GIS SIS 00 Color superconductor Quark/Gluon Vacuum Normal Pion condensation phase Density 0 =0.1(fm -3 ) Neutron star Nuclear Density : (fm -3 )

4 Nuclear force and short range correlation Nuclear force short range correlation of the nuclear interaction 1 exchange + 1 exchange + g (short range: phenomenological parameter) V longitudinal ph = 4πf g' NN k + ω k ( σ k)( σ k) transverse f ρ k V 4π ' ph = f g NN + ( σ1 )( σ ) τ1 τ ω k k f k mπ Critical Density of Pion Condensation Finite expectation value of pion in nuclei Landau-Migdal parameter g ~ g NN, g N, g (N-h)(N-h), ( -h)(n-h), ( -h)( -h) residual interaction g NN, g N ~ Gamow-Teller region, g N ~ quasi-free scattering g ~ excitation region Coherent Pion Production (CPP) m π 1 τ τ g NN 1 1 g N 1 S 1 T g S 1 S T 1 T 1 V g V transverse V longitudinal V q(fm-1) g NN N N -1 g N N -1 g N -1 N N -1 N N -1 N -1

5 Pion condensation phase in high density nuclear matter Short range correlation : g ~ sensitive to critical density of pion condensation phase ~ determine the limit of from the CPP measurement Universality ~ g = g NN=g N =g Relativistic H.F. [1] M. Nakano et al., IJMP E 10-6 (001) 459 [] A. Onishi et al., arxiv:nucl-th/

6 Coherent Pion Production A(p,n + )A(G.S.), A(, - + )A(G.S.) Inclusive measurement Coincidence measurement of neutron and pion Cross section ~ spin longitudinal component : dominant CPP n, t Real Pion Real Pion spreading Quasifree decay Hole Particle Hole Particle Nucleon spreading Nucleon knockout Interaction ~ Virtual Pion q p, 3 He Nucleus (G.S.) Coherent Pion Production (CPP) -Virtual pion ~ emitted from incidence proton beam -Excite /nucleon-particle nucleon-hole states -Propagate with mixing particle-hole states -Produce the real pion -Target nucleus is left in the Ground State (G.S.) Nucleus (G.S.) (virtual) pion scattering Pure longitudinal mode ~ Cross section at forward angle ~ Longitudinal Response Function short range correlaton : g at resonance region

7 - A(, - + )A n, t Neutrino and Hadron Probes Real + Spin longitudinal response function ~ Dominant Residual interaction : + +g (short range) Virtual P, 3 He (Virtual) Pion Scattering Sensitive to NN short range component g Neutrino ~ Weak interaction No distortion, absorption test the, in the interior of nucleus Adler s theorem : M~T( (q)+n X) g =0.33 =0.4 Hadron ~ Strong interaction Distortion, absorption peripheral reaction ~ nuclear surface

8 Distortion effects

9 Present status Hadron probe Sacray (3He,t + ) ~ resolution : poor / shutdown LAMPF (p,n + ) ~ test experiment / shutdown RCNP (p,n + ) (3He,t + ) ~ in progress Neutrino ~ J-PARC! A(, - + )A* what should be considered resolution yield..

10 Coherent Pion Production at RCNP g DD extracted from Coherent Pion Production p + A n A (g.s.) 1. Peak shift from N-D residual interaction E g (ћcf pnd /m p ) 0. Longitudinal response function (R L ) ~ dominant at 0 degree s cpp (0 ) R L g (g NN, g ND, g DD ) virtual pion scattering in target nucleus RCNP coherent pion cross section[]. proton A target nucleus 0 scattering virtual N -1 neutron g =0.33 =0.4 ground state + correlation of cross section and g [3]. [] E. Oset, Nucl. Phys. A 59 (1995) 47. [3] T. Udagawa et al., Phys. Rev. C 49 (1994) 6.

11 Experiment Beam ~ proton 400MeV un-polarized Target ~ 1 C (100mg/cm ) True Event 100nA ~ 0.15 cps Observables pion energy and angle position counter (developed newly) neutron energy Neutron Counter NTOF coincidence missing mass spectra Requirements high spatial and angle resolution Dx < 100mm Dq < 1 mrad counting rate ~ 100kcps High magnetic field ~ 0.5 T space boundary Neutron TOF ws target ( 1 C) Ring Cyclotron GEM detector coincidence pion counter 50 < E pi < 150 MeV AVF Cyclotron AVF Cyclotron Facility Schematic layout of the GEM+NTOF experiment

12 Tracking Detector: Gas Electron Multiplier charged particle amplif ication area E aramid carbon (6 m) Ar+ e - Drift (3 kv/cm) GEM 1 GEM V ~400V GEM 3 electron avalanche Readout Board (GND) analog LSI amp. mux. analog data to ADC GEM Readout Board trigger tracking Sci Sci 1 position position 1 GEM detector charged particle

13 Readout System Present Status of Production hardware DAQ system Specification high speed data transfer Readout Electronics Space Wire Protocol Analog-LSI boards Analog MUX Flash ADC SW host Readout Board data CPLD I/O Board ~000ch FPC (one of 14) Va3_Rich Trig/Ctrl

14 Experimental status Hardware Trigger scintillator with WLS fiber GEM detector ~ prototype Experiment and analysis Status Beam: proton (39MeV, <30nA) Target: 1 C (113mg/cm ) Event rate: kcps (p + n event) proton background ~ not separated clearly True/B.G. < 1/60 Improvements TOF & shield longer path length shielding around the beam-line tracking detector precise b information reconstruction with high position resolution range of CPP event energy spectrum of neutron Feasibility check ~ this year Data production run ~ this year/next year background TOF spectrum of pion counter ADC histogram

15 Neutrino induced CPP E=1 GeV resonance region ~, propagation in the interior of nucleus fm /MeV

16 Neutrino Beam Line Beam energy ~ 1 GeV Detector ~ BNL case Liquid Sci. With W.L.S Target Proton Carbon! Nucleus Around Near Detector

17 Predicted response function Quasi-free Longitudinal attractive Transverse repulsive Nuclear density dependence ~ g Neutrino ~ interior of nucleus ~ saturated density Hadron ~ surface of nucleus ~ low density Pion condensation phase Neutron star structure Cooling mechanism of neutron star 6 / g Critical density of pion condensation g M.Nakano et. al. Int. J. of Mod. Phys. E10(001) 459

18 Vacuum : Spontaneously broken ~ Pion as Goldstone boson Nucleon µ i A µ Pion distribution in nuclei Nuclear structure ~ pion distribution Surface pion condensation ~ finite expectation value of pions in the nuclear surface! Chiral Symmetry ~ Pion ( x ) = m π i fππ ( x ) qq 0 ( 50MeV ) 0 1. Meson Cloud in Nucleon : Sea Quark Flavor Asymmetry ~ Drell-Yan process / lepton-dis (E, p ) (E, p) q e * d( x ) u( x ) N u u d h h h + Nucleus (finite density) : Partially restored Nucleus Appeared Phenomena. Nuclear force mediated by pion ~ Strong tensor force meson : J P =0 - pv p + = ( ψ σψ ) φ H ( N. R.) High Density Matter : Restored Simple transition to study the pion behavior in the nucleus 1. Gamow-Teller states (GT) : S=1, L=0 ~ interaction from pi/rho-meson exchange Polarized 3 He beam separate pi / rho response to GT. Pion-like 0 - states : Carry a quantum number of pion Polarized 3 He/ 6 Li beam 0 - state search/identify uπ r π 3 f 1 f e V (1,) τ a 1 a σ1 1 τ a σ = µ π µ = π 4πr ( τ τ )[( σ ) Y ( x) S Z( x) ] V OPEP ( 1,) = mπ c f 1 1 σ + 1 f u p Mean field theory with pion-nucleon coupling ~ Finite pion density in the nuclear surface Include pion exchange explicitly in the mean field σ ψ' jl' ψ jl π ψ ξψ jl + ζψ' ψ' jl' ( σ ) ψ jl ( l' = l ±1) jl jl' σ iα + γ 0 ( M + g ) a a + g ω + g τ ρ + e ω ρ σ f + m π 1 3 π a γ γ γ τ π 0 + τ A ] ψ = E ψ 5 a H. Toki et al. Meson Cloud Pion Distribution In Nucleus? Pion energy ~ Surface like : V~A -1/3 P n+ +

19 Pions in nuclei Volume type or Surface type distribution? Intrinsic energy of 1 C as a function of pion number expectation [1]. [1] A. Onishi et al., arxiv:nucl-th/

20 Search for 0 - state with Polarized 3 He Beam Motivation 1. J P =0 - excitations : carry the simple Pion-like quantum number will have a pion correlation in the nucleus. 0 - state is not clearly separated poor data, limited 3. (p,n) data by Orihara et al. ~ low incident energy large difference between data and DWBA at large q ~ signature of pionic field? Physics Goal states search with high resolution charge exchange reaction ( 3 He,t) and ( 6 Li, 6 He). Polarized beam ~ Powerful tool to identify 0 - states with spin observables 3. Pion correlation in the nucleus D nn 1 = σ 1+ t σ l 1 Spin Observables = Tool for 0- state Search/Identification 1. Spin transfer. High resolution charge exchange reaction (p,n) data If longitudinal character ~ dominant (p,p ) data H. Orihara et al., PRL 49, 1318 (198) K. Hosono et al., PRC 30, 746 (1984)

21 Microscopic structure of Gamow-Teller states Motivation : 1. Microscopic structure of Gamow-Teller States ~ observed in high resolution ( 3 He,t) : Can not explain with usual shell model. Parity mixing state due to pion field in the nuclear medium ~ possible explanation? Physics Goal : 1. Determine the pion response (contribution) to Gamow-Teller states obtain the information on parity mixing state. Pion distribution in nucleus ~ Surface pion condensation σ ( q = ) V ( q = 0) B( GT ) 0 στ Parity Mixing State p 1/ + s 1/ f 5/ + d 5/ Nuclear Interaction At large q 0, 1. Tensor interaction ~ dominant. Pion correlation ~ large 3. Sensitive to pion behavior in nuclei j j -1 j MeV 8 0 q 0 p 3/ + d 3/ f 7/ + g 7/ s 1/ + p 1/ d 3/ + p 3/ d 5/ + f 5/ Spin transfer measurement 1. Separate pion / rho-meson contribution. Identify GT states at 0 degree Identify spin flip ( S=1, L=0) states with Polarization Transfer D nn at 0 degree At large q, measure the spin transfer : t t l σ ( nˆ ) σ ( Qˆ ) σ ( qˆ ) 1 Dnn = = t t l t σ ( nˆ ) + σ ( Qˆ ) + σ ( qˆ ) 1+ σ / l σ H. Fujita et al. Determine transition density : t σ l σ ρ = ρ t fi, τ l fi, τ V V t τ l τ ( q ) ( q ) Simple transition Discuss the parity mixing state and pion distribution ρ l fi, τ = I f M f j exp iq [ r ] j σ qτ I M j j i i ρ t fi, τ = 1 I f M f j exp iq [ rj ] σ j qτ j Ii M i

22 CPP reaction mechanism ~ - Real + n, t Virtual P, 3 He (Virtual) Pion Scattering + Real pion Virtual pion in nuclei Offshell pion to onshell Neutrino probe ~ can penetrate interior of nucleus ~ volume type Hadron probe ~ sensitive to surface

23 What should be done next g ~ measurement accuracy pions in nuclei ~ theoretical calculation ~ what should be observed Neutrino beam ~ Coherent Pion Production ~ separation difficult measured observables and extracted physics MC preparation ~ physics/detector study Required specification for the detector Detector design

24 Summary Nuclear physics with Neutrino Beam New probe ~ Neutrino at J-PARC Coherent Pion Production Interior of nucleus ~ Spin response function Short range correlation of nuclear force g ~ phase transition of nuclear matter Pions in Nuclei Natural extension of Spin-Isospin Physics at RCNP Physics discussion, Detector design..