Further Evidence for the Nonexistence of Particle-Stable Tetraneutrons

Abstract

--*. -F u r t h e r E v i d e n c e f o r t h e N o n e x i s t e n c e of P a r t i c le -Stab le T e t r a n e u t r o n s S e a r c h f o r T e t r a n e u t r o n s Using a R e c o i l P r o t o n D e t e c t o r S . C i e r j a c k s , G. M a r k u s , W . M i c h a e l i s , W. P ö n i t z

Can Four Neutrons Tango?

“…The 8 He beam intensity was 2 × 10 6 counts=s with a bunch structure synchronized with the cyclotron radio frequency of 13.7 MHz. The purity of the 8 He beam was 99.3%. To obtain the missing-mass spectrum of the tetraneutron system with approximately 1 MeV resolution, the SHARAQ spectrometer was used at 0°to measure the momenta of two α particles that are decay products of 8 Be.…”

“…The energy of the state is 0.83 AE 0.65ðstatÞ AE 1.25ðsystÞ MeV above the threshold of four-neutron decay with a significance level of 4.9σ. Utilizing the large positive Q value of the ð 8 He; 8 BeÞ reaction, an almost recoilless condition of the four-neutron system was achieved so as to obtain a weakly interacting four-neutron system efficiently. Multineutron systems have attracted considerable attention in nuclear physics [1].…”

“…A candidate resonant tetraneutron state is found in the missing-mass spectrum obtained in the doublecharge-exchange reaction 4 Heð 8 He; 8 BeÞ at 186 MeV=u. The energy of the state is 0.83 AE 0.65ðstatÞ AE 1.25ðsystÞ MeV above the threshold of four-neutron decay with a significance level of 4.9σ.…”

“…Possible testing of universality in many fermion systems is another interesting application of these studies. The weakly coupled many-neutron systems can provide an opportunity to investigate the universality in systems governed by a strong interaction; the BCS-BEC crossover found in cold atoms is a good example [6,7].Several attempts have been made to find a bound tetraneutron system by using a uranium fission reaction [1,8], a pion double-charge-exchange (DCX) reaction 4 Heðπ − ; π þ Þ [9-11], and several transfer reactions [12,13]. The existence of the bound tetraneutron system was also discussed in theoretical studies [14][15][16].…”

“…A primary beam of 18 O at 230 MeV=u was bombarded onto a 20-mm-thick beryllium target at BigRIPS [26]. The secondary beam of 8 He at 186 MeV=u was transported to a liquid helium target with a thickness of 136 mg=cm 2 at SHARAQ-S0. A schematic view of the experimental setup for the downstream of F6 is shown in the left panel of Fig.…”