Study of Light -Hypernuclei by Spectroscopy of Two Body Weak Decay Pions Liguang Tang Department of Physics, Hampton University Jefferson National Laboratory (JLAB) JLab PAC40, June 18, 2013 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) + - This previous PR is now proposed as a part of combined experiments that can run at same time to maximize physics outcome
HRS – HKS: (e, e’K + ) experiments for mass spectroscopy HKS – Enge or HKS – HES: New decay - spectroscopy experiment Future Project: Super Hypernuclear Physics Experiment at JLab Unified collaboration from the previous Hall A and C collaborations Enge ( ) HES ( ) HKS (K) HRS (e’) Septum Combine the features of previous Hall A and C experiments, create an optimized future program w/ the CEBAF CW beam
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 hypernuclei, some of which cannot be produced or measured precisely by other means
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’ -- 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
Precise measurement of ground state B ( 20keV) for a series of light hypernuclei with high resolution (130keV), spin-parity determination of g.s., charge symmetry breaking (CSB) from mirror pairs Neutron rich light hypernuclei ( - coupling) and neutron drip line limit ( 6 H and 8 H) Formation of quasi free continuum and fragmentation mechanism Physics Goal of Decay Pion Spectroscopy Provide precise input for theoretical description of -N interaction. Since B and excitation are the only sources of experimental information, study wide range of hypernuclei is needed.
Preliminary Results from MAMI-C 4H4H 2011 Run Partial 2012 Run Partial KID affected by huge rate of e + at 0 Added 10cm Pb curtain Luminosity increased KID was still a problem K+ singles increased just a little KAOS – SPEC-C 2 A beam 20 A beam We are convinced at least on 4 H observation
Higher production rate (~9 times) Excellent PID for both K + and - Less background (accidental or real) Full coverage of the interested - momentum range Can take data together with the (e, e’K + ) experiment Advantages of Jlab Experiment
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. We are convinced from the MAMI-C test runs that the technique works.