E COLLABORATION

Transcription

1 E COLLABORATION A.Acha, H.Breuer, C.C.Chang, E.Cisbani, F.Cusanno, C.W.de Jager, R. De Leo, R.Feuerbach, S.Frullani, F.Garibaldi, D.Higinbotham, M.Iodice, L.Lagamba, J.LeRose, P.Markowitz, S.Marrone, R.Michaels, Y.Qiang, B.Reitz, G.M.Urciuoli, B.Wojtsekhowski And the Hall A Collaboration Hyp-2006 John J. LeRose October 10,

2 Thomas Jefferson National Accelerator Facility Newport News, Va. (aka JLab) Recirculating Superconducting Electron Accelerator 3 simultaneous beams 200 μ-amps (total) CW E max 6 GeV, σ E ~ 3 x 10-5 P ~ 85% October 10,

3 Hall A A Pair of High resolution Magnetic spectrometers (HRS( HRS s) QQD n Q design Momentum Resol. ~ 1 x 10-4 FWHM Angle Resol.. ~ 1 milli-rad Y 0 Resol.. ~ 1 mm BigBite (large acceptance spectrometer) Big Hand (neutron detector) Møller and Compton Polarimeters And more (see see hallaweb.jlab.org/) A Pair of superconducting septum magnets (Θ( HRS = 6 ) 6 October 10,

4 Hypernuclei - historical background - experimental techniques : hypernuclear identification with visualizing techniques emulsions, bubble chambers 1970 Now : Spectrometers at accelerators: CERN (up to 1980) BNL : (K -, π - ) and (K +, π + ) production methods KEK : (π -, K - )and(π +, K + )productionmethods Elementary reaction on neutron : K + n π + Λ π + + n K + + Λ e.g. > 2000 : Stopped kaons at DAΦNE (FINUDA) : (K - stop, π- ) 12 C 12 ΛC > 2000 : Hypernuclear production with an electron beam Elementary reaction on proton : e + p e + K + + Λ Production of MIRROR hypernuclei Λ: I=0, q=0 Λn = Λp Spectroscopy of mirror hypernuclei reveal Λn Λp ΛΣ 0 mixing and ΛN-ΣN coupling October 10, C e.g. 12 ΛB

5 Present status of Λ Hypernuclear Spectroscopy This exp. E Λ N (e,e K + ) O. Hashimoto and H. Tamura, Prog. Part. Nucl. Phys, in press. October 10,

6 Requirements for Studying Electroproduction of Hypernuclei in Hall A High quality electron beam ~100 μa CW σ E/E < 3 x 10-5 <100 μm m spot High resolution spectrometers at small angles 6 ( Septum magnets) Δp/p ~ 1 x 10-4 ( HRS) Excellent particle identification π rejection factor ~1000 ( ( RICH) October 10,

7 User name LeRose Log entry time 12:23:39 on April29,2004 Entry number keyword=good Beam! Beam Strip Charts σ =3 x 10-5 SLI energy spread October 10,

8 Hall A (e,e( e,e K + ) spectrometer setup October 10,

9 12 C(e,e ) 6 6 and 2 GeV Counts 4 10 g.s (FWHM) all peaks Excitation Energy [MeV] October 10,

10 RICH detector C 6 F 14 /CsI proximity focusing RICH ϑ Ch MIP Performances: N p.e. # of detected photons (p.e.) and σ θ (angular resolution) Separation Power ϑ2 ϑ1 = n σσ ϑc Cherenkov angle resolution σ = ϑ c σ p. e. ϑ N p. e. October 10,

11 October 10,

12 Rich PID Effect of Kaon selection : Coincidence Time selecting kaons with Aerogels and with RICH: AERO K AERO K && RICH K π K P Aerogels: n 1 =1.015 n 2 =1.055 n 1.and. n 2 = K Pion rejection factor ~ 1000 October 10,

13 Expected Missing Mass Resolution 1. σe beam /E : 2.5 x ΔP/P (HRS + septum) ~ Straggling, energy loss Δ Missing Mass ~ 600 kev (FWHM) For more see Franceco Cusano s talk in parallel session D2 October 10,

14 Kinematics, Counting rates e beam E beam = 4.016, 3.777, GeV P e = 1.80, 1.56, 1.44 GeV/c P k = 1.96 GeV/c θ e = θ K = 6 ω= E γ 2.2 GeV Q 2 ~ 0.08 (GeV/c) 2 Beam current : 100 μa Target thickness : ~100 mg/cm 2 Counting Rates ~ counts/peak/hour Targets: 12 C, 9 Be, H 2 O ( 16 O & p) October 10,

15 12 C(e,e K) 12 ΛB October 10,

16 Results on 12 C target Hypernuclear Spectrum of 12 Λ B October 10,

17 12 B Λ spectrum : FIT to the data χ 2 /ndf = kev FWHM October 10,

18 E Hall A Experiment Vs. KEK-E C(e,e K) Λ B Λ C(π C(π + +,K,K + + )) Λ C Λ H. H. Hotchi Hotchi et et al., al., Phys. Phys. Rev. Rev. C C (2001) (2001) October 10,

19 E Vs. FINUDA (at DaΦne) C(e,e K) Λ B Λ C(K C(K - -,, π )) Λ C Λ October 10,

20 Shell model excitation levels for 12 B Λ dependence on the ΛN potential - different set of potential params. 11 C energy spectrum 12 Λ B energy spectrum J=2 +, 3 + J=2 +, 3 + J=2 +, 3 + J=3/2 - E=~5 MeV J=5/2 - E=~4.5 MeV J=1/2 - E=~2 MeV J=3/2 - E=0.0 MeV Λ x 0p Λ J=2 - J=2 - x 0s Λ J=2 - J=1 - J=1 - x 0s J=1 - x 0s Λ J=1 -, 2 - doublet YNG potential Canonical Standard October 10,

21 Comparison with theory DWIA 1 Saclay-Lyon 2 model for elementary K + Λ Shell Model wave functions (8-16 POT N-N interaction 3 ) Λ-N interaction parametrization from γ-ray spectra on 7 Li 4 Λ 1 Sotona M., Frullani S., Prog. Theor. Phys. Suppl. 117 (1994) T. Mizutani, et al., Phys. Rev C 58, 75 (1998) 3 S. Cohen and D. Kurath, Nucl. Phys. A101, 1 (1967) 4 M. Ukai et al. Phys. Rev C 73, (2006) October 10,

22 E : status of 12 Λ B data C(e,e K) Λ B Λ Energy resolution is ~ 636 kev (FWHM) Draft PRL is circulating within the collaboration October 10,

23 9 Be(e,e K) 9 ΛLi 16 O(e,e K) 16 ΛN with p(e,e K)Λ For more see Stefano Marone s talk in parallel session A1 and Pete Markowitz s talk in parallel session C1 October 10,

24 E-94107: Very Preliminary Results on 9 Be target Counts / 200 kev 9 Be(e,e K) 9 Λ Li Red line: Benhold-Mart (K MAID) Blue line: Saghai Saclay-Lyon (SLA) Curves are normalized to the g.s. peak. Missing energy (MeV) October 10,

25 E-94107: waterfall target Be windows H 2 O foil H 2 O foil October 10,

26 E-94107: Preliminary missing mass spectrum 1 1 H (e,e K)Λ O(e,e K) Λ N Λ O(e,e K) Λ N Λ October 10,

27 Summary: The experiment required important modifications to the Hall A apparatus. New experimental equipment performed beautifully. Good quality data on 12 C, 9 Be and 16 O targets ( 12 Λ B, 9 Λ Li and 16 ΛN Hypernuclei) have been taken Re 12 ΛB: S-shell Λ with YNG looks good. P-shell Λ needs work The RICH detector performed as expected and is crucial in kaon selection. VERY Promising Physics outlook for data on the waterfall and 9 Be targets 16 Λ Nand 9 ΛLi hypernuclear spectroscopy p(e,e K)Λ X-Sect. measurement October 10,