Estee J, Lynch W G, Tsang C Y, Barney J, Jhang G, Tsang M B, Wang R, Kaneko M, Lee J W, Isobe T, Kurata-Nishimura M, Murakami T, Ahn D S, Atar L, Aumann T, Baba H, Boretzky K, Brzychczyk J, Cerizza G, Chiga N, Fukuda N, Gasparic I, Hong B, Horvat A, Ieki K, Inabe N, Kim Y J, Kobayashi T, Kondo Y, Lasko P, Lee H S, Leifels Y, Łukasik J, Manfredi J, McIntosh A B, Morfouace P, Nakamura T, Nakatsuka N, Nishimura S, Otsu H, Pawłowski P, Pelczar K, Rossi D, Sakurai H, Santamaria C, Sato H, Scheit H, Shane R, Shimizu Y, Simon H, Snoch A, Sochocka A, Sumikama T, Suzuki H, Suzuki D, Takeda H, Tangwancharoen S, Toernqvist H, Togano Y, Xiao Z G, Yennello S J, Zhang Y, Cozma M D
National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
IFIN-HH, Reactorului 30, 077125 Măgurele-Bucharest, Romania.
Phys Rev Lett. 2021 Apr 23;126(16):162701. doi: 10.1103/PhysRevLett.126.162701.
Many neutron star properties, such as the proton fraction, reflect the symmetry energy contributions to the equation of state that dominate when neutron and proton densities differ strongly. To constrain these contributions at suprasaturation densities, we measure the spectra of charged pions produced by colliding rare isotope tin (Sn) beams with isotopically enriched Sn targets. Using ratios of the charged pion spectra measured at high transverse momenta, we deduce the slope of the symmetry energy to be 42<L<117 MeV. This value is slightly lower but consistent with the L values deduced from a recent measurement of the neutron skin thickness of ^{208}Pb.
许多中子星特性，比如质子丰度，反映了对称能对状态方程的贡献，当中子和质子密度差异很大时，这种贡献起主导作用。为了在超饱和密度下限制这些贡献，我们测量了通过将稀有同位素锡（Sn）束与同位素富集的Sn靶碰撞产生的带电π介子的能谱。利用在高横向动量下测量的带电π介子能谱的比值，我们推断对称能的斜率为42<L<117 MeV。这个值略低，但与从最近对(^{208}Pb)中子皮厚度的测量中推断出的L值一致。
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