Status of the HD polarization Project for SPring-8

Transcription

1 Status of the HD polarization Project for SPring-8 M. Germany 1. SPring-8 Facility 2. Motivation of Physics 3. Present Status of Polarized proton and deuteron target: HD target project 3 rd Meeting Polarized Nuclear Targets for Europe in the 6 th European Framework Program February 2-4, 2006, Rech, Germany Super Photon ring 8 GeV 8 GeV electron beam Diameter 457 m RF 508 MHz One-bunch is spread within 12 psec. Beam Current = 100 ma Life time hours 1

2 LEPS facility Collision 8 GeV electron Recoil electron a) SPring-8 SR ring Laser light Electron tagging b) laser hutch Inverse Compton -ray c) experimental hutch RCNP JAERI JASRI collaboration M. Fujiwara, Nuclear Physics News 11 (2001) Laser System 351 nm Ar laser 0.5 multi-line UV, 4 W photons/sec on target 0.2 Linearly polarized laser beam 0.1 Polarized LEP beam ~95% at 2.4 GeV E (GeV)

3 Back Compton Scattering Energy of BCS photons Back Compton scattering E El 1 cos L El 1 cos L 1 cos Ee : Electron velocity /c L : Incident angle of laser photon : Scattered angle of photon Incident electrons E e Scattered electrons Scattered photons E Incident Photons E l Head-on collision ( L =0) E E 2 2 4E mc ex. E e =8 GeV, (Laser =351 nm) 2.4 GeV Maximum l l E e =8 GeV 3

4 LEPS spectrometer SVTX DC1 TOF AC(n=1.03) ray beam LH 2 Target Dipole Magnet Start Counter 0.7 Tesla DC2 DC3 Charged particle identification Reconstructed mass for CH 2 target K/ separation (positive charge) Events K K + p d Momentum (GeV) + K + Mass/Charge (GeV) Mass(GeV) (mass) = 30 MeV (typ.) for 1 GeV/c Kaon 4 cut for K + /K - /proton PID 4

5 Vertex distribution (KK, K tracks) Vertex distribution Events LH 2 target (50mm) ToF start counter Vacuum Window x vertex (mm) BG from target cell z vertex (mm) z vertex (mm) LH 2 target : < z < -910 mm BG from target cell : (z<-960mm, x<-15 mm) Missing mass spectrum p(,k + ) (1116) 72,500 events p(,k + ) 0 (1193) 48,900 events 1.5 ~ 2.4 GeV 0.6 < cos cm < 1 Photon beam asymmetry 5

6 R. Zegers et al., Phys. Rev. Lett. 91 (2003) M. Sumihama et al., soon published in PRC. Photon beam asymmetry d Vertical = d d v [ 1 + Pcos(2) ] dunpol d d Horizontal d = dunpol [ 1 - Pcos(2) ] h nn v - N h nn v + N h N = F acc d d = Pcos(2) N : K + photoproduction yield : K + azimuthal angle P : Polarization of photon n : Normalization factor for N v For all events Long standing Naïve Question: What is the reason for the existence of two quark systems (Mesons) and three quark systems (Baryons)? There is no reason of QCD to exhibit 4-, 5-, 6-, multi-quark systems Why only two or three? Baryonium hunting Dibaryon search (H-dibaryon etc..) 6

7 Pentaquark (5 quark) system QCD does not forbid qqqqq states, but so far only baryons (qqq) and mesons (qq) have been found. (1405)? 3-quark particle (uds) 5-quark particle (uudsu) still poor data / ambiguous interpretation + 5-quark state (uudds) meson-baryon resonance exotic S=+1 particle Nakano et al., PRL 91, (2003) Peak of + neutron neutron 7

8 Summary of positive results in 2004 Experiment LEPS/SPring-8 DIANA CLAS(d) SAPHIR ITEP(n) CLAS(p) HERMES ITEP(p) ZEUS Mass (MeV) : : few : : : : : : : (MeV) : 25 : 9 : 21 : 25 : 20 : 26 7 : : 24 : Note: Many positive results have been changed to Negative in 2005! Correlated di-quark model + Pentaquark particle Alpha Cluster by Yamazaki & Akaishi 8

9 D K - p X ; M(K - p)= (1520) Counts/5 MeV (?) preliminary MMd(,K p) GeV/c 2 By Nakano et al., 2005 What is the spin and party of +? Naïve quark model Diquark correlations? Jaffe-Wilczek Quark bag surrounded by the pion cloud Hosaka, Phys. Lett. B571, 55 (2003) udud s s p << (mass) udud s s p s 4 s ps 3 s Negative Positive 9

10 Spin observables? Beam asymmetry B Nakayama & Tsushima: Phys. Lett. B583, 269(2004) for the positive parity of the beam asymmetry is significantly positive, whereas for the negative parity of beam asymmetry is significantly negative Physics motivation Nucleon Spin Sum Rules Gerasimov-Drell-Hearn (GDH) 2 2 d m 1/ 2 3/ Forward Spin-Polarizability 1 1/ 2 3/ 2 0 d ss contents in nucleon p p + spin-parity N K ( p p ) 10

11 + spin-parity determination Zhao and Al-Khalili PLB585(2004)91 n K Beam-target double polarization asymmetry 1/2 + 1/2 - meson LEPS of SPring-8 Studying diffractive channels as a tool for non-perturbative QCD (Pomeron structure, search for glueball, f 2 -meson trajectories, etc ) Non-polarized observables are not suitable for this study Search for exotic processes as ss-knockout Henley et al. [94] Titov, Yang, Oh [94-98] 11

12 ss contents in proton -meson: ~ ss p p pomeron exchange + exchange + ss knock-out Study small amplitudes by interference double polarization asymmetry events /2.5MeV =10 MeV Proton(938) events /2.5MeV Missing mass (,K + K - )X (GeV) Invariant mass square (K + K - ) (GeV 2 ) Invariant mass square (K - p) (GeV 2 ) Invariant mass (K + K - ) (GeV) Selections for event (KK mode) M(KK)-M < 10 MeV MM((,K + K - )X)- M proton < 30 MeV 12

13 beam-target double spin asymmetry for p p Titov et al. PRC58(1998)2429 Polarization observables with linearly polarized photon ( in meson rest frame) K + K - Decay direction // to direction of beam Spin-flip processes in Pomeron and f 2 K + K - K + Decay Plane // natural parity exchange (-1) J (Pomeron, Glueball, scalars`) Decay Plane unnatural parity exchange -(-1) J (Pseudoscalar mesons ) 13

14 cos K+ distribution For spin-conserving processes: W(cos ) ~ sin 2-0.2< t < - t min GeV 2, 2.2 < E < 2.4 GeV y x K + z Raw data Numberofevent Distribution on azimuthal K + K - decay angle (tool for double spin-flip processes) Raw data CLAS/LEPS 0 tot 14

15 K+ - pol distribution (tool for unnatural parity exchange processes) t min < t <0.2 GeV 2, 2.2 < E < 2.4 GeV Numberofevent/30 deg. Raw data K+ - pol (degree) Mibe et al. Phys. Rev. Lett. 95, (2005). 15

16 Mibe et al. Phys. Rev. Lett. 95, (2005). What we can study? +p+p +pk + +, K p + p +nk

17 Quark Dynamics from Jlab (D.S. Carman et al., PRL 90, (2003)) CERN Courier June 2003 (6) u Weak decay of d s (7) d u u proton u pion S= 1 3 P 0 operator: 2:1 Quark-pair creation operator? Missing resonances? d Large Anisotropy due to weak decay ss-quark content of proton and neutron p= uud + uudss 17

18 G0 experiment at JLAB: Anapole moment e electroweak process nucl-ex/ Z 0 e This simple picture depicts pairs of strange quarks as they pop into and out of existence alongside the permanent quark residents of the proton. Nuclear physicists have found that strange quarks, though present for just tiny fractions of a second at a time, also contribute to the proton's properties. Image: JLab SPIN CRISIS at least 10% ss content in nucleon - A.I. Titov, et al., Phys. Rev. Lett. 79, 1634 (1997). 18

19 Beam-target asymmetry and exotic processes with unnatural parity exchange ( ss-knockout) LEPS, Spring-8 (calculated by Titov) with 1% ss-bar content Error estimation for C BT measurement C BT = ( p - BG ) ( A - BG ) ( p - BG ) + ( A - BG ) R= BG p + A )/2 = p A p + A - 2 BG C BT ( ) 2 = {1-C BT (1-R)}+C BT R ( p ) 2 C BT C BT (1-R) p + R 2 (1-R) 2 BG ( ) 2 BG 19

20 Polarization in thermal equilibrium H B g N(B) I z B If I=1/2, -1/2> E=g N B +1/2> P N N N N e e ΔE 2kT ΔE 2kT e e ΔE 2kT ΔE 2kT E tanh( ) 2kT proton : g p N B/2kT= B(T)/T(K) electron: g e B B/2kT=0.67 B(T)/T(K) Spin Hamiltonian H H H H H H J, H I : Zeeman terms J I 3( J r )( I r ) H JI a( ), 3 5 : dipole-dipole int. r r H bj L ci L L: rotational angular momentum LS J I IJ LS I,,, *, J,,, *, red: forbidden transition 20

21 Principle of HD Longstanding effort at Syracuse, LEGS/BNL ORSAY mk 15-17T 80% for H, 20% for D (vector) 20%70% in D with DNP 21

22 Present status LEGS/BNL (Syracuse) Orsay GRAAL/ESRF RCNP ( Spring-8) goal: 10m K, 17 T 22

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24 FROM PST05 Nov , Tokyo by KAGEYA et al., 24

25 HYDILE 70 K Shield Liquid 4 He (4.2 K) Saddle coils Al Wires NMR Coils Polarized HD Liquid 3 He (0.5 K) Solenoid Coil 25

26 Liq. He Facility RCNP Use existing House Power line Close to the RCNP office 26

27 1K Pot 1220mm Mixing Chamber 170mm Null Coil 70mm 538mm 550mm Correction Coil Main Coil NbTi joints & Switch 600mm 400mm Nb3Sn joints & Protection Circuit Rough dimensions of the magnet B (T) R(mm) ppm m m 15 Field profile around Magnet Center z (mm) B 0.20 (T) R(mm) Field profile around Mixing Chamber z (mm) 27

28 28 Field profile around Mixing Chamber R(mm) 70mm Mixing Chamber 170mm 1K Pot 538mm R(mm) Z(mm) B(T) Stray Field profile around Magnet

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31 Road map (5 years from 2005 fiscal year) for Studies of Hardron structures Fiscal year After 2010 DR SC magnet HD gas IBC TRC others IBC cryostat and new Data taking system TRC NMR DR+IBC SRC New DR Collaboration with Roma2 ORSAY US HD at Spring-8 meson production, K-production, hidden strangness of nucleon Roma2, ORSAY HD polarization Polarized HD SPring-8 Charged meson production Experiments with magnetic spectrometer Neutral particle detection with Scintillator ball Spin and parity determination of + particle New TPC Scintillator ball TPC design Scintillator ball Installation of new detectors total 92,507 kyen 103, ,000 93,000 93,000 New badget 83,505 96,000 96,000 86,000 86,000 total About 480,000 kyen 31

32 Summary 1. Some results from LEPS at SPring-8 3. C BT measurements with polarized target +p+p +pk + +, K + + +p + p +nk HD at SPring-8 32