6H 7LI(E,X):XUNDL-2 2025SH16 202506 6H c Compiled (unevaluated) dataset from 2025Sh16 6H c Phys. Rev. Lett. 134, 162501 (2025). 6H c Compiled by K. Setoodehnia and J. Kelley (TUNL), May 1, 2025. 6H c The neutron-rich nucleus {+6}H could be used as a benchmark for 6H 2c improving our understanding of nucleon-nucleon and multi-nucleon 6H 3c interactions. However, the results of various experiments and 6H 4c theoretical calculations on its ground state energy and width are 6H 5c inconsistent and ambiguous. To shed some light on this issue, the 6H 6c authors studied the {+6}H ground state using electro-excitation 6H 7c reaction for the first time. 6H c The experiment was performed at the spectrometer facility of the A{-1} 6H 2c Collaboration at the Mainz Microtron Accelerator. A 855-MeV electron 6H 3c beam impinged on a 45-mm-long, 2.4 g/cm{+2} {+nat}Li target, of which 6H 4c 92.7% is {+7}Li. The {+7}Li(e,e'p|p{++}) reaction populated (with an 6H 5c estimated production rate of about one count per day in the 0-10 6H 6c MeV/c{+2} energy range) the {+6}H{-g.s.} via a multi-step process: (1) 6H 7c excitation of a bound proton inside {+7}Li to a |D{++}(1232) resonance 6H 8c when 300 MeV energy is transferred from the electron beam to that 6H 9c proton. (2) This |D resonance subsequently decays via emission of 6H ac n+|p{++}. The neutron's momentum can be absorbed by another bound 6H bc proton resulting in the emission of p+{+6}H from {+7}Li. Triple 6H cc coincidences between the scattered electrons, emitted protons and the 6H dc |p{++} decay products were measured using 3 high resolution 6H ec spectrometers placed at |q{-lab}=15.1|', -23.8|', and 59.1|', 6H fc respectively. Energy loss, momentum, particle trajectory and tof of 6H gc each of these particles were measured using vertical gas Cherenkov 6H hc detectors equipped with drift chambers (with 3 mrad and 1% MeV/c 6H ic resolutions) and two layers of plastic scintillators at each focal 6H jc plane. 6H c The authors reconstructed the missing mass energy spectrum of {+6}H 6H 2c with a resolution of |J1.2 MeV. To subtract the background from {+5}H 6H 3c events which could be produced by a similar reaction via the {+6}Li 6H 4c content of the target, the experiment was repeated using a 99.99% 6H 5c enriched {+7}Li target. No difference in the reconstructed spectrum was 6H 6c observed. 6H c The deduced energy spectrum shows a clear peak around 2-3 MeV above the 6H 2c {+3}H+3n threshold, whose area is consistent (with a significance limit 6H 3c of 5.2|s) with the estimated {+6}H production rate. This peak is 6H 4c attributed to the {+6}H{-g.s.}. At around 21-22 MeV above the 6H 5c {+3}H+3n threshold, another peak with much lower statistics is apparent 6H 6c which could be the highest excitation energy of {+6}H observed by 6H 7c experiments involving pion beams. However, the low statistics prevented 6H 8c the authors to draw any conclusion. The ground state peak is fitted via 6H 9c a convolution of a Breit-Wigner shape plus a Gaussian function whose 6H ac FWHM is fixed to the experimental resolution of 1.2 MeV. From this fit, 6H bc the {+6}H{-g.s.} resonance energy above the {+3}H+3n threshold and the 6H cc width are determined. The systematic uncertainty budget is discussed 6H dc extensively. The present results favor those previously measured 6H ec {+3}H+3n resonance energies and widths that are smaller. Using the 6H fc previous results, the authors deduced E{-c.m.}({+3}H+3n)=2.6 MeV {I3} 6H gc and |G=1.6 MeV {I3} for the {+6}H{-g.s.}. Comparison with previous 6H hc experimental and theoretical results are discussed in details. It is 6H ic suggested that {+6}H may have a stronger n-n or n-n-n interaction than 6H jc expected. 6H CL T$LABEL=|G (MeV) 6H CL S$LABEL=E{-c.m.}({+3}H+3n) (MeV) 6H cL DICT$(e,X)=(e,e'p|p{++}) 6H L 0 1.9 MEV 11 2.3 6 6H cL T$From 1.9 MeV {I10} (stat.) {I4} (sys.). 6H cL S$From 2.3 MeV {I5} (stat.) {I4} (sys.). 6H 2H(8HE,4HE):XUNDL-3 2022NI08 202510 6H c Compiled (unevaluated) dataset from 2022Ni08. 6H c Phys. Rev. C 105, 064605 (2022). 6H c Compiled by K. Setoodehnia and J. Kelley (TUNL), September 3, 2025. 6H c The authors studied the {+6}H resonant states. 6H c A {+2}H({+8}He,{+3}He) experiment was performed at the Flerov 6H 2c Laboratory of Nuclear Reactions (JINR, Dubna) using the recently 6H 3c commissioned ACCULINNA-2 fragment separator coupled to the U-400M heavy 6H 4c ion cyclotron. The data for the {+2}H({+8}He,|a) reaction channel were 6H 5c analyzed in the present study. A 26-MeV/nucleon {+8}He beam, produced 6H 6c by projectile fragmentation of a 33.4-MeV/nucleon {+11}B beam on a 6H 7c thick Be target, impinged on a cryogenic deuterium gas target with a 6H 8c thickness of 3.7|*10{+20} atoms/cm{+2}. The recoil |a particles emitted 6H 9c from the reaction at |q{-lab}=8|'-26|' were measured using four 6H ac position sensitive |DE-E-VETO telescopes downstream of the target 6H bc covering the peripheral angles. The tritons from the {+6}H|){+3}H+3n 6H cc decay were measured in coincidence with the |a-particles at 6H dc |q{-lab}|<6|' using a position sensitive Si detector backed by a 4|*4 6H ec array of CsI(Tl) scintillators with 0.5|' and 2% angular and energy 6H fc resolutions, respectively. Neutrons were measured using a neutron wall 6H gc consisting of 48 stilbene-crystal modules that were positioned at |?2m 6H hc downstream of the target. This setup enabled the experimenters to 6H ic measure the |a-{+7}Li-n triple coincidences. 6H c The missing mass spectrum of {+6}H was deduced with a resolution of 6H 2c |?0.8-1.7 MeV from 3850 background subtracted |a-t coincident events. 6H 3c This spectrum shows a rise in E{-T}=3-6 MeV, where E{-T} is the 6H 4c triton energy in the {+6}H c.m. frame, followed by a somewhat flat 6H 5c region. The authors report that the rate of this rise is consistent 6H 6c with a relatively broad {Ip}-wave, {+3}H+3n resonant character of 6H 7c {+6}H, and they claim that there is a resonance or a group of 6H 8c unresolved resonances in {+6}H located at E{-T}|?6.8 MeV, which becomes 6H 9c more visible with an angular cut of |q{-c.m.}<16|'. 6H c The c.m. cross section of |?190 |mb/sr {I+40-80} was deduced for the 6H 2c 6.8-MeV bump at 5|'<|q{-c.m.}<16|'. This is consistent with the 6H 3c predictions by FRESCO calculations, and it is large enough to suggest 6H 4c the resonant population mechanism. The steep rise of detected counts 6H 5c in the missing mass spectrum at 3-3.5 MeV and the broad low-energy tail 6H 6c of the 6.8-MeV bump may indicate that another {+6}H* state may be 6H 7c located at about 4.5 MeV. The present study did not observe the 6H 8c {+6}H{-g.s.} that is expected at E{-c.m.}({+3}H+3n)=2.6-2.9 MeV. 6H c A total of 130 |a-t-n coincident events were found. The missing mass 6H 2c spectrum obtained from those events still shows evidence for the 6H 3c 6.8-MeV group (14 events) and the 4.5-MeV resonance, but no evidence 6H 4c is found for the {+6}H{-g.s.} expected at |J2.6 MeV. An upper limit of 6H 5c d|s/d|W{-c.m.}|<5 |mb/sr was obtained for the population of the ground 6H 6c state at around 2.6 MeV from Monte Carlo simulations and by a careful 6H 7c background analysis. Four-body {+3}H+3n and two-body {+5}H+n phase 6H 8c volume simulations cannot explain the observed counts in the E{-T}=3-8 6H 9c MeV region, which indicates that the observed {+3}H+3n excitation 6H ac function must be coming from resonant contributions. The deduced 6H bc spectrum was best fitted using two Lorentzian peaks with |G=1.5 MeV at 6H cc E{-c.m.}=4.5 MeV and E{-c.m.}=6.8 MeV. A single broad peak with |G=5.5 6H dc MeV at E{-c.m.}=6.8 MeV underestimates the low-energy data. 6H c The experimental energy distributions of the {+3}H decay fragments 6H 2c (emitted from the {+6}H states at E{-T}=4.5 MeV and E{-T}=6.8 MeV) in 6H 3c the {+6}H rest frame were deduced using the |a-t and |a-t-n coincident 6H 4c events. Those distributions are consistent with one another at 6H 5c E{-T}=3.5-5.5 MeV and at E{-T}=5.5-7.5 MeV. These distributions were 6H 6c analyzed assuming decay via a direct 4-body decay ({+6}H|){+3}H+3n), or 6H 7c via a sequential neutron emission through {+5}H{-g.s.}. The measured 6H 8c energy distributions suggests that the {+6}H{-g.s.} decays via {+5}H+n, 6H 9c which, in turn, decays via emission of a very strongly correlated 6H ac dineutron: {+6}H{-g.s.}|){+5}H{-g.s.}+n|){+3}H{-g.s.}+{+2}n+n. 6H c Finally, the present study does not support the literature value for 6H 2c the ground state at E{-c.m.}({+3}H+3n)|?2.6 MeV. Extensive discussion 6H 3c for this suggestion is presented based on analogies among He and H 6H 4c isotopes' excitation spectra, pairing energy and based on the results 6H 5c of an earlier study using a pion double-charge exchange reaction on 6H 6c {+6}Li. The authors consider the location of the {+6}H{-g.s.} as a 6H 7c still open question and suggest that the E{-c.m.}({+3}H+3n)=4.5 MeV 6H 8c resonance observed here could be the ground state. 6H CL T$LABEL=|G 6H CL S$LABEL=E{-c.m.}({+3}H+3n) (keV) 6H cL T$Width assuming a Lorentzian-shaped peak. 6H cL $The reported resonances above the {+3}H+3n threshold are assuming to 6H 2cL be |D{Il}=1, {Ip}-wave states. 6H cL $d|s/d|W{-c.m.}|?190 |mb/sr {I+40-80} for E{-c.m.}=4-8 MeV and at 6H 2cL 5|'<|q{-c.m.}<16|'. 6H cL $d|s/d|W{-c.m.}<5 |mb/sr is set for E{-c.m.}({+3}H+3n)<3.5 MeV. 6H L 0 1.5 MEV 4.5E3 3 6H cL S$This is interpreted as the lowest-energy resonant state in {+6}H 6H 2cL with reasonably large population cross section, which can be consistent 6H 3cL with the present data. 6H cL $Decay mode: {+5}H{-g.s.}+n|){+3}H+{+2}n+n. 6H L 2.3E3 6 1.5 MEV 6.8E3 5 6H cL E$This state may be a group of unresolved states, or a single broad 6H 2cL state with |G=5.5 MeV; however, the former interpretation is preferred 6H 3cL by the authors. 6H cL E$If a single broad state is assumed, then that should be interpreted 6H 2cL as the upper limit resonance energy admissible for the present data as 6H 3cL the ground state.