HYPERNUCLEAR PHYSICS USING CEBAF BEAM PAST AND FUTURE Liguang Tang Hampton University/JLAB 4 th Workshop on Hadron Physics In China and Opportunities with JLAB 12GeV July 16-20, 2012

INTRODUCTION – BARYONIC INTERACTIONS Baryonic interaction (B-B) is an important part of nuclear force that builds the “world” - Neutron Stars - Astronomical Scale - Neutron Stars - H H (1p) He  (  - 2p, 2n) C  C (3  ) Understand B-B interactions is one of the essential tasks in Nuclear Physics

,  0 (uds) n (udd) p + (uud)  + (uus)  - (dds)  - (dss)  0 (uss) S Q I S = 0 S = -1 S = -2 I 3 = -1 I 3 = +1/2 I 3 = -1/2 I 3 = +1 I 3 = 0 Nucleon (N) Hyperon (Y) S - Strangeness I - Isospin I - Isospin

INTRODUCTION – HYPERNUCLEAR PHYSICS  To understand YN and YY interactions  Producing Y inside of the nucleus  Extract YN and YY interactions by studying the many body system  To study short range interactions in baryonic interactions (OPE is absent in  N interaction)  To better explore nuclear structure using  as a probe (not Pauli blocked by nucleons) and to explore new degree of freedom  Model the baryonic many body system  Study the role and the single particle nature of  in various nuclear medium and density  N and  are the most fundamental interactions. Since  decays only weakly (  N or  N  NN) thus long lifetime, mass spectroscopy  - hypernuclei becomes possible analog to the nuclear mass spectroscopy

 Shell Model with 2-B  N Effective Potential (p N s  ) ssss V  N = V 0 (r) + V  (r) s N  s  + V  (r) L N   s  + V N (r) L N   s N + V T (r) S 12  Additional Contribution:  -  coupling   N   N  Contribute to the repulsive core  Introduce an additional term:   Observables:  Ground state single  binding energy  Excitation spectroscopy (levels and level spacing)  Production and production cross sections  Decays V —  SS SNSN T 5 Radial Integrals: Coefficients of operators THEORETICAL DESCRIPTION: 2B POTENTIAL

BASIC PRODUCTION MECHANISMS AZAZ  n AZAZ -- K-K- (K,  ) Reaction  Low momentum transfer  Higher production cross section  Substitutional, low spin, & natural parity states  Harder to produce deeply bound states AZAZ  n A ++ K+K+ ( , K) Reaction  High momentum transfer  Lower production cross section  Deeply bound, high spin, & natural parity states A  (Z-1)   p AZAZ e e’e’ K+K+ (e, e’K) Reaction  High momentum transfer  Small production cross section  Deeply bound, highest possible spin, & unnatural parity states  Neutron rich hypernuclei CERN  BNL  KEK & DA  NE  J-PARC (Near Future) Disadvantage: Lack absolute energy calibration and resolution CEBAF at JLAB (MAMI-C Near Future) Advantage: Absolute energy calibration & high resolution

4  He 4H4H 3H3H 7  He 7  Li 6  He B  (MeV) 5  He 9  Be 9  Li 8  Be 8  Li 8  He 7  Be 13  N 13  C 10  B 12  B 11  B 9B9B Important source of data but lack statistics and resolution Reliability: Questionable Nevertheless, emulsion experiments before 80’s provided the most complete set of measured single  binding energy B  of s- and p-shell  -hypernuclei

Missing predicted gamma ray Advantages: High resolution (~ few keV) and precise level spacing Disadvantages: low rate (statistics) and unable to measure the ground state binding energy

KEK336 2 MeV(FWHM) KEK E MeV(FWHM) High resolution, high yield, and systematic study is essential and is the key to unlock the “gate” Meson beam lacks absolute mass calibration (no free neutron target) BNL 3 MeV(FWHM)

ELECTRO-PRODUCTION USING CEBAF BEAM  High quality primary beam allows high precision mass spectroscopy on  -hypernuclei  Producing  and  0 from proton simultaneously allows absolute mass calibration – precise binding energy  Mirror and neutron rich hypernuclei comparing those from (  +,K + ) reaction  Spectroscopy dominated by high spin-stretched spin-flip states  Results are important in determining , S N and V 0 terms from  s states and S  term from states with  at higher orbits

 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 E K+K+ e’ Phase II E 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

 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 E Common Splitter Magnet

6GEV PROGRAM HIGHLIGHTS 6GEV PROGRAM HIGHLIGHTS  00 Allowing precise calibration of mass scale p(e, e’K+)  and  0 (CH2 target)

-B  (MeV)  0.02  0.2 MeV from  nn 7  He E in Hall A (2003 & 04)  s (2 - /1 - )  p (3 + /2 + ’s) Core Ex. States ~635 keV FWHM 12  B 6GEV PROGRAM HIGHLIGHTS– CONT. K+K+ _ D K+K+ 1.2GeV/c Local Beam Dump E Λ B spectrum ~800 keV FWHM HNSS in 2000 ss pp Phase I in Hall C (E89-009) Phase II in Hall C (E01-011) B  (MeV) 28 Si(e, e’K + ) 28  Al (Hall C E01-011) HKS JLAB Counts (150 keV/bin) 28  Al ss pp dd Accidentals Phase II in Hall C (E01-011) ~500 keV FWHM HKS in  B 16  N (Hall A) F. Cusanno et al, PRL 103 (2009) 16  N F. Cusanno et al, PRL 103 (2009) ss pp Phase III in Hall C (E05-115) ss pp

6GEV PROGRAM TECHNIQUE SUMMARY  Hall A experiment (Pair of Septums + two HRS)  Advantage: Almost no accidental background and be able to study elementary process at low Q 2 at forward angle  Disadvantage: Low yield rate and cannot study heavier hypernuclei  Hall C experiment (Common Splitter + HKS + HES/Enge)  Advantage: High yield rate and high precision in binding energy measurement  Disadvantage: High accidental background and solid targets only Future program: Combination

EXPERIMENTAL LAYOUT IF IN HALL C HKS - Kaons Enge - Pions HES - Electrons Hodoscope Lucite Č Drift Chamber 64mg/cm 2 22mg/cm 2 K+K+ -- Trigger I: HKS(K) & Enge(  ) for Decay Pion Spectroscopy Experiment Trigger II: HKS(K) & HES(e’) for Mass Spectroscopy Experiment

 High quality with low background  High precision on binding energy and high resolution  High yield rate which leads to wide range of physics:  Elementary production at forward angle  Detailed and precise level structure of light and medium heavy hypernuclei (shell models)  Precise shell structure of heavy hypernuclei (single particle nature and field theory)  High efficiency and productivity: one exp.  Four 6GeV experiments  New physics: Decay pion spectroscopy (Light Hypernuclei)  Precise ground state B   Determination of ground state J p  Search for neutron rich limit (high Isospin states   ) Technical Features of Future Program

DECAY PION SPECTROSCOPY TO STUDY  -HYPERNUCLEI 12 C  - Weak mesonic two body decay ~150 keV Ground state doublet of 12  B B  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    4H4H 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

110 ~ 160 MeV/c ~ MeV/c110.1 ~ MeV/c ~ MeV/c ~ MeV/c Possible observation 4  H ground state Central Mom. : MeV/c → B Λ ( 4 Λ H) : ~ － 1.60 MeV Width : 97 keV/c FWHM Target straggling loss was not corrected Spec-C momentum calibration was not yet done MAMI-C Short Test Run on Decay Pion Spectroscopy

SUMMARY  Hypernuclear Physics is an important part of nuclear physics  Program with CEBAF beam is the only one that provides precise B  and features as Precision mass spectroscopy program  Future program will be highly productive