1 / 31

General Review of GRAAL physics : Achievements and Future

General Review of GRAAL physics : Achievements and Future. D. Rebreyend LPSC Grenoble (GRAAL Collaboration) MENU04, 30 August ’04. Outline. GRAAL set-up Meson photoproduction on the proton Eta photoproduction on the neutron HYDILE polarized HD target. Compton Beam. Polarisation.

balin
Download Presentation

General Review of GRAAL physics : Achievements and Future

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. General Review of GRAAL physics :Achievements and Future D. Rebreyend LPSC Grenoble (GRAAL Collaboration) MENU04, 30 August ’04

  2. Outline • GRAAL set-up • Meson photoproduction on the proton • Eta photoproduction on the neutron • HYDILE polarized HD target D. Rebreyend, MENU04

  3. Compton Beam Polarisation Energy Spectrum Linear Simulation Tagged region EeESRF = 6027.6 0.6 MeV Experiment Circular FWHM=16 MeV Ftag~ 10 6g/s D. Rebreyend, MENU04

  4. LAGRANgE Detector • Shower Wall • neutron efficiency 20 % •  / neutron PID 250 E 1: Compton g beam 2: Liquid H2/D2 target 3: BGO Calorimeter 4: Cylindrical MWPC’s 5: Plastic Barrel 6: Plastic Wall 7: Plane MWPC’s 8: Shower Wall ToF D. Rebreyend, MENU04

  5. GRAAL Domain LEGS/BNL LEPS/SPRING8 • Eg = .6-1.6 GeV/ W=1.4-2 GeV • Region of second and third resonance • h, K, w,h’ thresholds • Complementary of LEGS and LEPS s (mb) Eg (GeV) h’ threshold w threshold KL threshold h threshold D. Rebreyend, MENU04

  6. Meson Photoproduction on the proton

  7. Survey of GRAAL Results • Published • p+n: S from 700 to 1500 MeV (PLB ’00 and ’02) • hp : S and ds/dW from threshold to 1100 MeV (PRL ’98, PLB ’02) • p0p0p: S and ds/dW from 700 to 1500 MeV (PRL ’03) • Close to completion • p0p: S and ds/dW from 700 to 1500 MeV • hp : extension to 1500 MeV • In progress • p: comparison neutral (p0) / charged decay (p+p-p0) • K and K  D. Rebreyend, MENU04

  8. K Analysis • Channel selection • 3 tracks in MWPC’s • 2-body kinematical constraints  calculation of 3 momenta • PID by combining calculated momenta with DE and/or ToF • important check: vertex reconstruction Distance (primary-secondary) vertices (No efficiency correction) c = 7.6 cm (PDG: 7.89 cm) K L p p+p-

  9. Beam Asymmetry angular distribution ds/dW = (ds/dW)0{1 – PS cos(2f) } 1.05 GeV Good agreement with LEPS PRL ‘03 Azimuthal distribution 1.2 GeV PS 1.4 GeV P angular distribution NH+NV NV-NH/NH+NV Recoil Polarization (linear polar.) 1.05 GeV PLx = PgOx sin2f / (1 - Pg Scos2f) PLy = P - PgT cos2f / / (1 - Pg Scos2f) PLz = PgOz sin2f / (1 - Pg Scos2f) 1.2 GeV 1.4 GeV

  10. Cross Section SAPHIR data (EPJ ’04) p  K+ Counts/dose (a.u.) p  K+S Counts/dose (a.u.)

  11. Eta photoproduction on the neutron

  12. Recent Motivation Soliton Model anti-decuplet Non-exotic resonance with a narrow width 10 MeV • SAID analysis : Possible narrow N* at 1680 and/or 1730 MeV • Polyakov & Rathke (EPJ A18 (03)) : • Dominance of photoproduction on the neutron for N10 • look for reactions :  n  N10  n, K0, K+- D. Rebreyend, MENU04

  13. Preliminary Remarks • Grenoble analysis (A. Lleres) • Studied channels : • d + • nK0 • nK+- • n n (“ easy channel ”) cross section • Comparison p pproton target / deuteron target • Preliminary results (error bars only statistical) • No Fermi momentum correction: width structure(E )100-130 MeV No evidence but statistics is too poor for definite conclusion D. Rebreyend, MENU04

  14.  n(p)  n(p) Event Selection • All final state particles detected: 2  + n (p) • proton/neutron detected at forward angles :  lab 250 • 2  detected in BGO : lab 250 • Selection by  invariant mass and 2-body kinematical angular correlations • no recoil proton/neutron   n / p • Identical geometrical acceptances for n and p • Selection of “Quasi-Free kinematics” ?? D. Rebreyend, MENU04

  15. Invariant Mass  n   n  p   p h p : 0.6 % (taking  p=  n )  n : 0.3 % h N  : 1-2 % h N  : 1-3 % 1.2 % 0.9 % Background estimates Simulation Data Small background D. Rebreyend, MENU04

  16. p   p Differential Cross Section : Free/Quasi-free Distributions at fixed CM  (backward) angles versus E CM = 1230 CM = 1170 CM = 1620 CM = 1480 d/d (b/sr) CM = 1390 CM = 1300 CM = 1100 CM = 1040 Clear Discrepancy below 1100 : Data Analysis / Physics ? not quasi-free reaction close to 1000 D. Rebreyend, MENU04

  17.  n   n Differential Cross Section d/d (b/sr) at fixed CM CM = 1540 CM = 1340 • No prominent peak • Structure at E 1.05 GeV (W 1.7GeV) • Marked Angular Dependence CM = 1200 CM = 1070 D. Rebreyend, MENU04

  18. Comparison QF neutron vs QF proton (1)Ratio QF neutron/QF proton R=dn/dp at fixed CM CM = 1540 CM = 1340 • Ratio 0.6-0.5 below 900 MeV • (Bonn, R=0.68 PRL ’97) • Sudden rise around 1 GeV  resonance • (Kouznetsov, Moscow seminar, April ’03) CM = 1200 CM = 1070 D. Rebreyend, MENU04

  19. Comparison QF neutron vs QF proton (2)Integrated Cross Section (p,n 250) neutron normalized QFproton neutron – C x proton * Simulated peak : W=1.68 GeV,  = 10 MeV Because of Fermi motion : FWHM = 127 MeV • No “narrow” peak observed in neutron cross section but • shoulder for neutron above 900 MeV • Rise in difference (neutron-proton) compatible with “narrow” structure D. Rebreyend, MENU04

  20. Comparison QF neutron/QF proton (3)Integrated ( n) Invariant Mass (p,n 250) neutron – C x proton neutron normalized proton * Simulated peak : W=1.68 GeV,  = 10 MeV Because of resolution : FWHM = 96 MeV Number of events (n) Invariant Mass (GeV) • No peak : compatible with behaviour of d/d • Spreading due to Fermi motion Resolution D. Rebreyend, MENU04

  21. Beam Asymmetry  n   n  p   p Beam Asymmetry  See R. Di Salvo’s talk in Parallel Session for more details D. Rebreyend, MENU04

  22. HYDILE target

  23. Operating Principle & Performances • Pure HD • good dilution factor (15 % Al) • n and p are polarized • “Relaxation Magnetic Switch”principle (Hoenig ’67) • o-H2 impurities used to polarize (HD weakly coupled to lattice) • o-H2 decays to p-H2 in a few days HD spins decoupled from lattice • relaxation time / 1/ o-H2 concentration • Fabrication process • polarization of HD with static method in a Dilution Refrigerator (17 T, 10 mK) at Orsay • aging process in DR for 2-3 months  1 T, 1 K • transport from Orsay to Grenoble • Expected performances • polarization : 80 % for p and 20 % for d (50 % with FAP) • relaxation time : 1-2 weeks D. Rebreyend, MENU04

  24. Dilution Refrigerator (Orsay) In-beam + transfert cryostats (Grenoble)

  25. Recent achievements • Installation of Transfer (TC) and In-beam cryostats (IBC) in Grenoble (10/03) • Running of IBC during 3 days at 1.5K (11/03) • First complete and successful transfer of an unpolarized HD sample from Orsay to Grenoble (April 2004) First run with polarized HD in November 2004 D. Rebreyend, MENU04

  26. Summary • p and K,  : results will be released in a “near” future •  n   n : preliminary results on d/d have been obtained at neutron forward angles ( 250) • No prominent peak but structure is observed around W=1.7 GeV not seen on the proton • Extension to all angles foreseen • First data with HYDILE target scheduled in November!! D. Rebreyend, MENU04

  27. Proton Beam Asymmetry D. Rebreyend, MENU04

  28. Neutron Beam Asymmetry D. Rebreyend, MENU04

  29. K0 Analysis D. Rebreyend, MENU04

  30. K0 results D. Rebreyend, MENU04

  31. European Synchrotron Radiation Facility ESRF parameters • Circumference : 844 m • 40 beamlines • Ee = 6.03 GeV • Ie = 200 mA • Bunch structure = 2.8 ns GRENOBLE D. Rebreyend, MENU04

More Related