BNL-AGS E930 Home Page

High-Resolution Gamma Spectroscopy of Hypernuclei using a Large-Acceptance Germanium Detector (Hyperball)


Collaboration List


The experiment E930 aims at a high-resolution gamma-ray spectroscopy measurement of several light Lambda hypernuclei employing Hyperball, a large-acceptance germanium detector array for hypernuclear studies constructed in Japan. Lambda hypernuclei are produced by the (K-,pi-) reaction and their gamma transitions are detected in coincidence. We use K- beam at D6 beam line together with the E813 spectrometer (48D48 spectrometer). We will experimentally determine all the terms of Lambda-N spin-dependent interactions, namely, spin-spin, spin-orbit, and tensor forces between a Lambda and a nucleon, through detailed level structures of 9-Lambda-Be, 16-Lambda-O, 7-Lambda-Li, 12-Lambda-C hypernuclei, etc.

·  E930 run in 1998

Data for 9-Be target were taken in 1998 and the two transitions in 9-Lambda-Be, E2(5/2+ -> 1/2+) and E2(3/2+ -> 1/2+), were separately observed at 3.05 MeV. Their energy difference was measured to be only 31+-2 keV, which confirmed a very small spin-orbit force (Lambda-spin-dependent spin-orbit interaction) in the Lambda-N interaction.

·  E930 run in 2001

We will have a beam time in 2001 for 16-Lambda-O, 10-Lambda-B and 7-Lambda-Li runs.

We will detect two M1 transitions from the 6 MeV-excited 1- state to the ground-state doublet (1-, 0-) and the splitting of the doublet will be measured. It gives a strength of the Lambda-N tensor force.

In 7-Lambda-Li run, we use 1.1 Gev/c (K-,pi-) reaction to populate the spin-flip 7/2+ state and try to observe the spin-flip 7/2+ -> 5/2+ M1 transiiton. The energy spacing between the weighted average of the (7/2,5/2) doublet and the weighted average of the (3/2,1/2) gives a good measure of the Lambda-N nucleon-spin-dependent spin-orbit force. It allows us to separately extract strengths of the symmetric LS and the anti-symmetric LS forces, and to understand the origin of the spin-orbit force in the nuclear (baryon-baryon) forces.

In 10-Lambda-B run, we aim at detecting the spin-flip M1 transition of the ground state doublet (3- -> 2-), of which energy is determined by both of the spin-spin and spin-orbit forces. The energy enables us to confirm the spin-spin and spin-orbit strengths measured from our 7-Lambda-Li (E419) and 9-Lambda-Be (E930) data. The sign of the spin-orbit force will be also obtained.

E930 Proposals

BNL-AGS Proposal (E930)
"High-Resolution Gamma-Spectroscopy of Hypernuclei using Large-Acceptance Germanium Detector"
--- submitted on "96-Sep-3, approved on '96-Oct-10

·  Full version (ps, 10 MB), Small version without Fig.1,2 (ps, 5 MB)

·  Cover letter to Tom Kirk (ps)

Proposal to DOE (E930)
"Determination of All the Lambda-N Spin-Dependent Forces using Hypernuclear Gamma Spectroscopy"--- included in the proposal by Hungerford titled "A Proposal to Fund Two Fixed-Target Experiments at the AGS " --- submitted in September, 1999.

·  ps file (7.4 MB)


·  Schemaic view of the setup (pdf) (1998)

·  Hyperball(schematic) , Hyperball(photo)

·  Floor layout in 2001 (eps) , (pdf)

Information for E930 Members

·  Log of the experiment and beam hours

·  Announcement

·  Visitors' schedule

·  BNL registration and housing manual (Japanese): BNLの実験登録の方法等

·  BNL shipping manual (Japanese) : BNLでの荷物の発送・受け取りの方法

·  New memory model (UMEM) used in E930 (designed by Ajimura)


·  Run in 1998

·  Run in 2001  D6 area  Hyperball, chambers, etc.  Around target  Installation  Aerogel Cherenkov  Counting room 

·  BGO counters


Hyperball Home Page (including the publication list)

BNL Experimental Support and Facilities Division


Hirokazu Tamura
Adderess in US:
c/o Prof. Morgan May
Physics Department, 510A, Brookhaven National Laboratory
Upton, NY 11973-5000, USA
phone: +1-631-344-2528
FAX: +1-631-344-5568
Address in Japan:
Department of Physics, Tohoku University
Aramaki, Aoba-ku, Sendai 980-8578, Japan
phone: +81-22-217-6454
FAX: +81-22-217-6455