1 / 29

Decay pion spectroscopy of electro-produced hypernuclei

APFB2011 22-26 Aug, 2011 Seoul, Republic of Korea. Decay pion spectroscopy of electro-produced hypernuclei. Tohoku Univ. Kyo Tsukada. Introduction Hypernucleus Concept of decay pion spectroscopy Physics of decay pion spectroscopy. Hypernucleus. Nucleus

meriel
Download Presentation

Decay pion spectroscopy of electro-produced hypernuclei

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. APFB2011 22-26 Aug, 2011 Seoul, Republic of Korea Decay pion spectroscopy of electro-produced hypernuclei Tohoku Univ. Kyo Tsukada

  2. Introduction • Hypernucleus • Concept of decay pion spectroscopy • Physics of decay pion spectroscopy

  3. Hypernucleus • Nucleus • many-body system of proton and neutron • Hypernucleus • Hyperon (Y=L here) in a nucleus • a new degree-of-freedom, “strangeness”, • L can be introduced deep-inside nucleus (no Pauli effect) • energy level can be measured directly • Y-N interaction can be investigated • Impurity effect for nucleus; shrinkage, clustering, deforming, … <-> N-N interaction n p L Y-N interaction should be investigated carefully and precisely for light hypernuclei. high resolution, high accuracy various nuclei ; wide range, new finding

  4. measurements of L(Y) Hypernucleus examples of processes reaction spectroscopy (BL ,mass) JLab MAMI J-PARC (e-’ K+), K+, π- e-, π+, K- γ-ray γ-ray spectroscopy (level splitting) J-PARC a, p weak decays (π-, NN) emulsion (L,LL) (mass) J-PARC L p- spectroscopy (mass) JLab MAMI We can measure the mass of various hypernucei by using completely different way with past experiments.

  5. p- spectra of past experiments • It is difficult to achieve both high statistics and resolution. 7ΛLi 11ΛB KEK-E287, E326 high rate and high quality primary electron beam (1013-14Hz, 100mmf) + thin target (̴10 mg/cm2) beam : stop K- target : 7Li decay p- spectroscopy with high resolution and high accuracy FINUDA Coll. and A. Gal et al., Phys Rev. B 681 (2009) 139 A. Gal, Nucl. Phys. A 828 (2009) 72

  6. Concept of decay pion spectroscopy ] e- beam Kaon tag p Fragments ] two body decay after stop pion spectroscopy π- Λ Absolute mass of various L hypernuclei pion momentum resolution ̴ 100 keV/c -> mass resolution ̴100 keV goal of accuracy ̴ a few 10 keV

  7. Hypernuclei from 9Be target Other targets, 7Li or 12C or so, should be measured in future.

  8. Physics of decay pion spectroscopy • High resolution and accuracy of mass for various light hypernuclei • 3LH, 4LH, …, 11LB, 12LB, i.e. A=3-12 • Spin-parity (JP) of the ground state • Charge symmetry breaking (CSB) • (4LH<->4LHe), (6LHe<->6LLi), (7LHe<->7LLi* <->7LBe), … • Search for hypernucleus near the neutron drip line • 6LH, 7LH, 8LH … • important information for L-S coupling • …

  9. Experiment • Facilities • Experimental apparatus • Estimations • Run summary • Some analysis plots of present conditions

  10. Electron beam facility MAMI-C JLab We started the feasibility study for the decay pion spectrometer experiment at Mainz in this year.

  11. MAMI-C (Mainz Microtron) Spec-B Spec-A Spec-C Frankfurt Mainz KAOS beam A1 collaboration 1st beam time : 24/May/2011-14/Jun/2011 KAOS and SpekC 2nd beam time : 19/Jul/2011-1/Aug/2011 KAOS and SpekA+SpekC 3rd beam time : near future ̴20 km southwest from Frankfurt

  12. spectrometers for decay p spectroscopy • 1500 MeV beam energy • zero-degree kaon tagged byKAOS • decay-pion detection with Spectrometer A & C (dp/p <10-4) 2m Beam dump K+ KAOS target KAOS SpekC SpekA p- p- SpekC SpekA pre-target beam chicane

  13. KAOS • Some detectors were newly introduced. • TOF wall (H-Wall) • Aerogel Cherenkov detectors (AC) • n = 1.015 • Tagger counters Tagger AC H-Wall G-Wall MWPC KAOS Magnet beam H-Wall Trigger=H ⊗G ⊗Tagger G-Wall

  14. Yield estimation • Model : Statistical decay model • Elementary cross section : 0.2-0.35mb/sr • Initial excited hypernucleus formation prob. : 0.7 • Hyperfragment stopping fractions : 0.87 • Two-body decay branch : 0.2-0.3 • Spectrometer acceptance : 28msr(SpekA,C), 12msr (KAOS) • Particle decay fractions in flight : 0.2 for p-, 0.3 for K+ 9Be target Phys.Lett.B697 (2011) 222 Kaon emission rate : 160-280Hz/mA Coincidence rate : 0.4-0.55 hyperfragments/day/mA

  15. Peak positions and momentum acceptance

  16. Run summary Kaon emission rate : 160-280Hz/mA Coincidence rate : 0.4-0.55 hyperfragments/day/mA

  17. Huge accidental positrons at KAOS accidental positron Covered by Tagger Covered by Tagger preliminary preliminary y-distribution at G-Wall [mm] The large acciedental events caused by positrons exists. Singles rate : 3MHz for G-Wall (H-Wall) for I=2.0uA We should avoid and/or remove positron efficiently. 1st + 2nd polinomial 2nd polinomial 1st polinomial

  18. Analysis • Analysis is ongoing. • Particle identification for KAOS and SpekA,C • Momentum reconstruction • Trace-back of particle tracks to target SpekC KAOS Dt=7.5ns (6.5ns for 110MeV/c) e+, p+ preliminary Dt=10.6ns (11ns for 110MeV/c) π- µ- proton e- time [nsec]

  19. summary • High resolution decay pion spectroscopy for light hypernuclei was proposed. • Mass resolution : ~100 keV • Mass accuracy : ~10 keV • Many light hypernulei including exotic states can be studied via the break-up of highly excited-states. • The 1st and 2nd commissioning run were performed at Mainz and the analysis is ongoing now. • The detectors should be improved in order to take data more efficiently with higher beam current.

  20. backup

  21. Nu ~ Nd ~ Ns Strangeness in neutron stars ( r > 3 - 4 r0 ) Strange hadronic matter (A → ∞) Strangeness LL, X Hypernuclei Z L, S Hypernuclei -2 N -1 0 World of matter made of u, d, s quarks “Stable” Higher density 3-dimensional nuclear chart by M. Kaneta inspired by HYP06 conference poster

  22. (e,e’K+) experiment at MAMI-C • Hypernuclear physics at MAMI-C • Upgrade of MAMI : 0.855 GeV -> 1.508 GeV (2006̴) • KAOS was introduced in MAMI-C (2008̴) Spec-B Kaos 縮尺

  23. (e,e’K+) experiment at MAMI MAMI JLab ~10 MeV (FWHM) ~2.5 MeV (FWHM)

  24. Experimental setup – target – 12C 45 mg/cm2 Al2O3 beam screen 9Be 22 mg/cm2 7Li (in future) beam SpecC SpecA 縮尺 target chamber Kaos

  25. 今回の実験のまとめ • 24 May 7:00 : start beam time • 25 May 18:00 ~ : start data taking • ~28 May 14:00 : calibration data for paddles • ~30 May 11:00 : coincidence data at 500 nA • ~1 June 10:00 : coincidence data at 300 nA with MWPC • ~1 June 22:00 : improvement of AC radiator (Matsushita -> Russian) • ~3 June 13:00 : coin data at 300 nA with MWPC • ~7 June 10:00 : coin data at 1500 nA w/o MWPC • ~8 June 11:00 : coin data at 2000 nA w MWPC • ~14 June 5:00 : coin data at 1500 nA w MWPC target : 125 μm 9Be Total Charge : 1.3 C Anselm : 1 counts / μA / day Sho : 170 counts / 10μA / 20days 10 counts stopping hyper fragments

  26. Target 横から ターゲットホルダー 上から Be 125 μm C 43.86 mg/cm2 Al2O3 beam screen Be 125×4 μm Li ? mg Scattering chamber empty 4 cm 冷却水ノズル

  27. Target x beam z y, x軸、合わせ mirror leveler2 mirror leveler2 ビームパイプ target マーカー マーカー leveler1 z軸合わせ

  28. trigger 124 deg Schematic view of Setup TOF ⊗ Tag ⊗ Scinti G-Wall e- H-Wall MWPC Kaos Kaon tag material : 9Be thickness : 125 μm tilt angle : 54 deg target AC Pion spectroscopy Pion spectroscopy SpecC SpecA VDC VDC 17 deg GC GC Scinti Scinti

  29. Kaos central momentum : 1000 MeV/c ] 0 degree (original beam direction) 17 deg 54 deg target (9Be 125mm) 107.95 deg 107.57 deg ] ] SpekA central momentum : 130 MeV/c momentum acceptance : 25% SpekC central momentum : 125 MeV/c momentum acceptance : 25% e- energy : 1508MeV

More Related