Decade of Hypernuclear Physics at JLAB and Future Prospective in 12 GeV Era Liguang Tang Department of Physics, Hampton University & Jefferson National Laboratory (JLAB) August , 2011, Hadron Physics 2011, Shandong University
Introduction – Hypernuclei Baryonic interactions are important nuclear physics issues to extend the QCD descriptions of single nucleon (its form factors, etc…) to strongly interactive nuclear many body system A nucleus with one or more nucleons replaced by hyperon, such as , , … a Hypernucleus Hypernucleus is a unique tool and a rich laboratory to study YN and YY interactions baryonic interactions beyond NN Study hypernuclei is an important gate way to the interaction
Unique Features of -Hypernuclei Long lifetime: -hypernucleus in ground state decays only weakly via N or N NN, thus mass spectroscopy features with narrow states (< few to 100 keV) Description of a -hypernucleus within two-body frame work – Nuclear Core (Particle hole) (particle): V ΛN (r) = V c (r) + V s (r)(S Λ *S N ) + V Λ (r)(L ΛN *S Λ ) + V N (r)(L Λ *S N ) + V T (r)S 12 Absence of OPE force in N: Study short range interactions is a “distinguish particle” to N (i.e. no Bauli Blocking): a unique probe to study nuclear structure Trace the single particle nature in heavy hypernuclei allows to study the nuclear mean field Hypernuclear physics is an important component in nuclear physics
Advantage of Electro-production Hypernuclei New spin structure due to photon absorption and large momentum transfer - Strong spin flip amplitudes -Highest possible spin Neutron rich hypernuclei ( N- N coupling) High resolution 1.5 MeV (hadronic production) <500keV High accuracy B 50keV is possible Technical challenges – Require small forward angles – High particle singles rates – Accidental coincidence rate – Challenging optics and kinematics calibration AA p A e e’e’ K+K+ (e, e’K) Reaction Low-lying states Lowest few and most stable core states (particle hole states) Narrow hypernuclear states with coupled at different shell levels Non-spin flip (natural parity) states or spin flip (unnatural parity) states These states are most studied
Hall A Techniquee e’e’e’e’ K+K+K+K+ HRS - Hadron HRS - Electron Septum Two Septum magnets - Independent two arms -No problem for post beam -Low e’ singles rate -Low accidental background Difficulties -High hadron momentum which which is resolved by RICH detector -High luminosity but low yield rate (long spectrometers and small acceptances)
Hall C Technique Zero degree e’ tagging High e’ single rate Low beam luminosity High accidental rate Low yield rate A first important milestone for hypernuclear physics with electro- production Beam Dump Target Electron Beam Focal Plane ( SSD + Hodoscope ) K + K + Q D _ D 0 1m Q D _ D Side View Top View Target (1.645 GeV) Phase I K+K+ e’ Phase II Common Splitter Magnet New HKS spectrometer large Tilted Enge spectrometer Reduce e’ single rate by a factor of High beam luminosity Accidental rate improves 4 times High yield rate First possible study beyond p shell
Hall C Technique – Cont. New HES spectrometer larger Same Tilt Method High beam luminosity Further improves accidental rate Further improves resolution and accuracy High yield rate First possible study for A > 50 Beam 2.34 GeV e’ K+K+ e Phase III Common Splitter Magnet
10/13/09 p(e,e'K + ) Production run (Waterfall target) Expected data from E07-012, study the angular dependence of p(e,e’K + ) and 16 O(e,e’K + ) 16 N at low Q 2 R esults on H target – The p(e,e’K + ) C ross S ection (Hall A) p(e,e'K + ) Calibration run (LH 2 Cryo Target) None of the models is able to describe the data over the entire range New data is electro-production – could longitudinal amplitudes dominate? oo
-B (MeV) 0.02 0.2 MeV from n n First reliable observation of 7 He JLab E (HKS, Hall C) Test of Charge Symmetry Breaking Effect. A Naïve theory does not explain the experimental result. A Naïve calculation on CSB effect, which explains 4 H – 4 He and available s, p-shell hypernuclear data, gives opposite shifts to A=7,T=1 iso- triplet Hypernuclei. Jlab E05-115
Hall A Result on 9 Li Spectroscopy Spectroscopy is still under study and not yet published.
E in Hall A (2003 & 04) s (2 - /1 - ) p (3 + /2 + ’s) Core Ex. States Red line: Fit to the data Blue line: Theoretica l curve: Sagay Saclay-Lyon (SLA) used for the elementary K- Λ electroproduction on proton. (Hypernuclear wave function obtained by M.Sotona and J.Millener) M.Iodice et al., Phys. Rev. Lett. E052501, 99 (2007) ~635 keV FWHM The 12 B Spectroscopy (Hall A & C) K+K+ _ D K+K+ 1.2GeV/c Local Beam Dump E Λ B spectrum ~800 keV FWHM HNSS in 2000 ss pp Phase I in Hall C (E89-009) Phase II in Hall C (E01-011) ~500 keV FWHM HKS in 2005 HKS 2005 has incorrect optics optics tune – affecting the line shape The source is found from Phase III 2009 HKS-HES experiment and the correct method is developed 2005 optics tune and kinematics calibration is under redoing together with the 2009 data The goals are Precise binding energy High resolution Resolve doublet separations
/ / / / / (3/2, 5/2) / 5/2 - 7 Li + (8.665) 0.0 3/ B S 1/2 12 B S 1/2 P 3/2 P 1/2 P 3/2 PP PP Threshold Theory g F. AJZENBERG-SELOVE and C. L. BUSCH, Nuclear Phystcs A336 (1980) g D.J. Millener, Nuclear Phystcs A691 (2001) 93c. P means a mixing of 1/2 and 3/2 states. The Expected 12 B Spectroscopy
Fit 4 regions with 4 Voigt functions c 2 /ndf = /13.76 0.16 Binding Energy B L =13.76±0.16 MeV Measured for the first time with this level of accuracy (ambiguous interpretation from emulsion data; interaction involving L production on n more difficult to normalize ) Within errors, the binding energy and the excited levels of the mirror hypernuclei 16 O and 16 N (this experiment) are in agreement, giving no strong evidence of charge-dependent effects R esults on 16 O target – Spectroscopy of 16 N (Hall A) F. Cusanno et al, PRL 103 (2009)
B (MeV) 28 Si(e, e’K + ) 28 Al HKS JLAB Counts (150 keV/bin) 28 Al ss pp dd Accidentals 1 st observation of 28 Al ~400 keV FWHM resol. Clean observation of the shell structures KEK E140a SKS 28 Si( ,K + ) 28 Si Peak B (MeV) E x (MeV) Errors (St. Sys.) # ± ± # ± ± # ± ± Spectroscopy of 28 Al (Hall C) HKS (Hall C) 2005 Wider Narrower
2009 data analysis is ongoing Current analysis: kinematics calibration and spectrometer optics optimization Additional data for existing spectroscopy 7 He, 9 Li, and 12 B (more statistics and better precision) New data: – 10 Be (puzzle of gamma spectroscopy) – 52 V (further extend beyond p shell) Additional Data By HKS-HES (Hall C, 2009)
New Concept in 12 GeV Era: Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions Fragmentation of Hypernuclei and Mesonic Decay inside Nucleus Free: p + - Free: p + - 2-B: A Z A (Z + 1) + - 2-B: A Z A (Z + 1) + -
Decay Pion Spectroscopy to Study -Hypernuclei 12 C - Weak mesonic two body decay ~150 keV Ground state doublet of 12 B Precise B J p and Direct Production p e’ e 12 C K +K + Example: Hypernuclear States: s (or p ) coupled to low lying core nucleus 12 B g.s. E.M. ** 12 B
Decay Pion Spectroscopy for Light and Exotic -Hypernuclei Fragmentation Process p e’ e 12 C Example: K +K + ** s 12 B * Highly Excited Hypernuclear States: s coupled to High- Lying core nucleus, i.e. particle hole at s orbit 4H4H Fragmentation (< s) 4 H g.s. 4 He - Weak mesonic two body decay (~ s) Access to variety of light and exotic hypernuclei, some of which cannot be produced or measured precisely by other means
High yield of hypernuclei (bound or unbound in continuum) makes high yield of hyper-fragments, i.e. light hypernuclei which stop primarily in thin target foil High momentum transfer in the primary production sends most of the background particles forward Precision does not depend on the precisions of beam energy and tagged kaons The momentum resolution can be at level of ~170keV/c FWHM, powerful in resolving close-by states and different hypernuclei B can be determined with precision at a level of 20keV The experiment can be carried out in parasitic mode with high precision hypernuclear mass spectroscopy experiment which measures the level structures of hypernuclei Physics analysis is more complicated while achieving high resolution is rather simple Study of Light Hypernuclei by Pionic Decay at Jlab Technique and Precision
Precisely determine the single binding energy B for the ground state of variety of light hypernuclei: 3 H, 4 H,..., 11 Be, 11 B and 12 B, i.e. A = 3 – 12 (few body to p shell) Determine the spin-parity J p of the ground state of light hypernuclei Measure CSB’s from multiple pairs of mirror hypernuclei such as: 6 He and 6 Li, 8 Li and 8 Be, 10 Be and 10 B. CSB can also be determined by combining with the existing emulsion result for hypernuclei not measured in this experiment Search for the neutron drip line limit hypernuclei such as: 6 H, 7 H and 8 H which have high Isospin and significant - coupling May also extract B(E2) and B(M1) electromagnetic branching ratios through observation of the isomeric low lying states and their lifetimes. The high precision makes these above into a set of crucial and extremely valuable physics variables which are longed for determination of the correct models needed in description of the Y-N and Y-Nucleus interactions. Study of Light Hypernuclei by Pionic Decay at Jlab Major Physics Objectives
e e ** K+K+ p AZAZ A (Z-1) A1 Z 1 stop A2 Z 2 (Z-1) = Z 1 +Z 2 ; A=A1+A2 -- A1 ( Z1+1)SPECTROSCOPY e e ** K+K+ , ( - ) p(n) AZAZ (A-1) Z’ -- NBACKGROUNDVS Comparison of Spectroscopic and Background - Production Study of Light Hypernuclei by Pionic Decay at Jlab Illustration on the Main Features
(a) 2-B decay from 7 He and its continuum (Phase I: 7 Li target) 1/2 + P Max P Min 0 2 ExEx ExEx 0 2 4H4H He 1/2 + 3/2 + 5/2 + 3H3H 6 He 1- ?1- ? 6H6H 5H5H - Momentum (MeV/c) 3B background (b) 3B background 2 0 ExEx 1 0 ExEx 1 0 ExEx 1 0 ExEx /2 + 5/2 + 1/2 + 9 Li 8 He Li 7H7H 1/2 + 3/2 + 7 Li 1- ?1- ? 6 Li Additions from 9 Li and its continuum (Phase II: 9 Be target) (c) Additions from 12 B and its continuum (Phase III: 12 C target) 12 B Be 11 B 10 Li 10 Be 5/2 + J p =? 10 B 9 He 9 Be 9B9B 8H8H 8 Be 8B8B 3B background Illustration of Decay Pion Spectroscopy
Experimental Layout (Hall A) in 12GeV Era HRS - Electron HKS - Kaons HES - Pions 64mg/cm 2 22mg/cm 2 K+K+ -- Trigger I: HRS(K) & Enge( ) for Decay Pion Spectroscopy Experiment Trigger II: HRS(K) & HRS(e’) for Mass Spectroscopy Experiment
Light Hypernuclei (s,p shell) Fine structure Baryon-baryon interaction in SU(3) coupling in large isospin hypernuclei Cluster structure A Elementary Process Strangeness electro-production Neutron/Hyperon star, Strangeness matter Hyperonization Softening of EOS ? Medium/heavy Hypernuclei Single particle potential Distinguish ability of a hyperon U o (r), m *(r), V NN, … E89-009, E01-011, E05-115(Hall C) E94-107(Hall A) H, 7 Li, 9 Be, 10 B, 12 C, 16 O, 28 Si, 52 Cr Future mass spectroscopy Decay Pion Spectroscopy (Light Hypernuclei) Precise B of ground state CSB Spin-parity J p of ground state Extreme isospin N system …
Summary High quality and high intensity CW CEBAF beam at JLAB made high precision hypernuclear programs possible. Programs in 6GeV era were successful. Together with J-PARC’s new programs, as well as those at other facilities around world, the hypernuclear physics will have great achievement in the next couple of decades. The mass spectroscopy program will continue in 12 GeV era with further optimized design The new decay pion spectroscopy program will start a new frontier