PRODUCTION AND DECAY OF CASCADE HYPERONS
PRODUCTION AND DECAY OF CASCADE HYPERONS
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DOI：
10.1103/physrev.179.1262
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发表时间：
1969-01-01
期刊：
影响因子：
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通讯作者：
MULLER, RA
中科院分区：
文献类型：
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作者：
DAUBER, PM;BERGE, JP;MULLER, RA
在束流动量为1.7、2.1和2.4-2.7 GeV/c的情况下，研究了K−入射到氢上产生级联超子的情况。获得了3028 Ω −和934 Ω 0的样品。给出了E-K+和E 0 K 0产生的横截面和极化。这些数据与I= 0重子交换在− K+产生中的主导地位相一致，但也为与Y 0*（2100）相一致的s通道中的共振形成提供了强有力的证据。在三体和四体末态中观察到大量的K ~*（1530）和K ~*（890）的产生。在质量接近1894 MeV/c2的K − K+ π 0和K − 0 K+ π−末态中观察到一个宽的π π增强，宽度约为98 MeV/c2。这种增强被Badier等人首次观察到的τ *（1930）所识别。寿命测量给出τ τ −=（1.61±0. 0 4）× 10− 10 sec和τ 0=（3.07− 0.20+ 0.22）× 10− 10 sec。假设自旋为1/2的衰变参数分析得出α Λ −=− 0.391±0.045，α Λ 0=− 0.43±0.09，Φ Λ − α ν tan（β γ）Λ −=−（14±1 1），如果使用α Λ= 0.647，则Φ Λ 0=（38±1 9）。这些结果符合T不变性和|Δ I| = 1 2规则。将LRL的结果汇编后得到α =− 0.380±0.034和Φ =−（1±7），这意味着Δ= invtan（− β α）=（178±1 6）。因此，如果T在衰变中严格守恒，则末态Λ π相位差δ s− δ p=−（2±1 6）。观察到两个<$−→ Λ e− ν的例子。对于其他的分支分数，上限为10 × 10− 3。|Δ S| = 1和|Δ S| = 2轻子和非轻子衰变的<$−和<$0。
The production of cascade hyperons by K− incident on hydrogen has been studied at beam momenta of 1.7, 2.1, and 2.4-2.7 GeV/c. A sample of 3028 Ξ− and 934 Ξ 0 was obtained. Cross sections and polarization for Ξ− K+ and Ξ 0 K 0 production are presented. The data are compatible with dominance by I= 0 baryon exchange in Ξ− K+ production, but also provide strong evidence for resonance formation in the s channel compatible with Y 0*(2100). Copious production of Ξ*(1530) and K*(890) is observed in the three-and four-body final states. A broad Ξ π enhancement is observed in the Ξ− K+ π 0 and Ξ 0 K+ π− final states at a mass near 1894 MeV/c 2 and with a width of about 98 MeV/c 2. This enhancement is identified with the Ξ*(1930) first observed by Badier et al. Lifetime measurements give τ Ξ−=(1.61±0. 0 4)× 10− 10 sec and τ Ξ 0=(3.07− 0.20+ 0.22)× 10− 10 sec. A decay-parameter analysis assuming spin ½ yields α Ξ−=− 0.391±0.045, α Ξ 0=− 0.43±0.09, Φ Ξ−≡ invtan (β γ) Ξ−=−(14±1 1), and Φ Ξ 0=(38±1 9) if α Λ= 0.647 is used. These results are in agreement with T invariance and the| Δ I|= 1 2 rule. A compilation of LRL results for Ξ− and Ξ 0 yields α Ξ=− 0.380±0.034 and Φ Ξ=−(1±7), implying Δ= invtan (− β α) Ξ=(178±1 6). Hence the final-state Λ π phase difference δ s− δ p=−(2±1 6) if T is strictly conserved in the decay. Two examples of Ξ−→ Λ e− ν were observed. Upper limits≈ 1× 10− 3 have been set for the branching fractions of other| Δ S|= 1 and| Δ S|= 2 leptonic and nonleptonic decays of Ξ− and Ξ 0.