Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions Liguang Tang Department of Physics, Hampton University Jefferson National Laboratory (JLAB) Hall A Collaboration Meeting, June 9-10, 2011, JLAB 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) + - (Update for E )
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 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
Light hypernuclei which stop primarily in thin target foil Weak 2 body mesonic decay at rest uniquely connects the decay pion momentum to the well known structure of the decay nucleus, B and spin-parity of the ground state of hyperfragment Decay pion spectroscopy can be accurately measured and variety of physics may be extracted Most of the background particles move forward, thus pion momentum spectrum is expected to be clean with minor 3-boby decay pions plus some from decay Precision and accuracy do 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 accuracy 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 the primary hypernuclei, as long as the two share the same target E : Study of Light Hypernuclei by Pionic Decay at Jlab Technique and Precision E Hall A Collaboration Meeting, June 9-10, 2011, JLAB
E : Study of Light Hypernuclei by Pionic Decay at Jlab Major Physics Objectives E : Study of Light Hypernuclei by Pionic Decay at Jlab Major Physics Objectives 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 these 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. E Hall A Collaboration Meeting, June 9-10, 2011, JLAB
e e ** K+K+ p AZAZ A (Z-1) A1 Z 1 stop A2Z2A2Z2 (Z-1) = Z 1 +Z 2 ; A=A1+A2 -- A1 ( Z1+1) SPECTROSCOPY e e ** K+K+ , ( - ) p(n) AZAZ (A-1) Z’ -- N BACKGROUND VS Comparison of Spectroscopic and Background - Production (Example) e e’e’ Hodoscope Lucite Č Drift Chamber -- K+K+ HRS - Hadron HRS - Electron Septum Trigger I: HRS(K) & Enge( ) for Decay Pion Spectroscopy Experiment Trigger II: HRS(K) & HRS(e’) for Mass Spectroscopy Experiment 64mg/cm 2 22mg/cm 2 K+K+ -- Experimental Tech. & layout Example E Hall A Collaboration Meeting, June 9-10, 2011, JLAB E : 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
Feasibility Test Run at MAMI by A1 Collaboration - Spec-C K+K+ KAOS Beam e’
MAMI Run Status The first beam period (Commissioning) The first beam period (Commissioning) – May 24 to June 14, 2011 – Maximum beam current: 1.5 A – KAOS detector system needs to be further optimized in order to run with high intensity run (50 A) – Pion arm proven to be clean and low single rate – Run is still undergoing The second period (implement e’ detector) The second period (implement e’ detector) – July 19 to July 31, 2011 The third possible beam period (higher intensity) – November to December, 2011 In general, the physics yield rate at MAMI is about 6 times smaller than that at JLAB In general, the physics yield rate at MAMI is about 6 times smaller than that at JLAB
Summary High intensity CW beam at JLAB and the characters of electro-production make possible for high precision hypernuclear programs, among which the decay pion program is unique. The decay pion spectroscopy program is able to provide precise and fundamental information needed to understand the YN and Y-Nucleus interactions. Unlike the mass spectroscopy program, this program does not request precision and stability on beam energy. Test run at MAMI is undergoing