论文标题
$ k^+k^ - $ $ $对在有效的质量区域接近$ 2M_K $
Investigation of $K^+K^-$ pairs in the effective mass region near $2m_K$
论文作者
论文摘要
CERN的DIRAC实验在反应$ \ rm {p}（24〜 \ rm {gev}/c）+ ni $中，粒子对$ k^+ k^ - ，π^+π^ - $ and $ p \ bar {p \ bar {p} $，配对系统中的相对动量$ q $少于100 mev/c/c。由于背景影响研究，Dirac探索了三个子样本的$ K^+K^ - $对，通过减去 - 使用飞行时间（TOF）技术获得 - 来自初始$ Q $分布的背景，其$ k^+k^ - $样本分数超过70 \％，50 \％和30 \％。首先在库仑模型中对相应的对分布及其纵向投影$ q_l $进行了分析，该模型仅考虑了库仑最终状态互动（FSI），并假定类似点样对生产。此库仑模型分析导致$ k^+k^ - $ $ $ q_l = 0.5 $ meV/c的产量增加了大约四个，而100 meV/c。为了研究强烈互动的贡献，考虑了第二个更复杂的模型，考虑到库仑FSI除了谐振$ f_0（980）$和$ a_0（980）$以及可变距离$ r^*$之间的colomb fsi外，也有生产的$ r^*$。该分析基于配对生产的三个不同参数集。对于70 \％的子样本和最佳参数，$ 3680 \ pm 370 $ $ k^+k^ - $ $ pairs被发现与$ 3900 \ pm 410 $ $ $ k^+k^ - $通过COULOMB模型提取。知道TOF削减对背景抑制的效率，评估检测到的$ k^+k^ - $对的总数约为$ 40000 \ pm 10 \％$，这与30 \％subsample的结果一致。 50 \％子样本中的$ k^+k^ - $ $对数与其他两个值的不同，大约三个标准偏差，证实了本子样本中的实验数据的可靠性较低。
The DIRAC experiment at CERN investigated in the reaction $\rm{p}(24~\rm{GeV}/c) + Ni$ the particle pairs $K^+K^-, π^+ π^-$ and $p \bar{p}$ with relative momentum $Q$ in the pair system less than 100 MeV/c. Because of background influence studies, DIRAC explored three subsamples of $K^+K^-$ pairs, obtained by subtracting -- using time-of-flight (TOF) technique -- background from initial $Q$ distributions with $K^+K^-$ sample fractions more than 70\%, 50\% and 30\%. The corresponding pair distributions in $Q$ and in its longitudinal projection $Q_L$ were analyzed first in a Coulomb model, which takes into account only Coulomb final state interaction (FSI) and assuming point-like pair production. This Coulomb model analysis leads to a $K^+K^-$ yield increase of about four at $Q_L=0.5$ MeV/c compared to 100 MeV/c. In order to study contributions from strong interaction, a second more sophisticated model was applied, considering besides Coulomb FSI also strong FSI via the resonances $f_0(980)$ and $a_0(980)$ and a variable distance $r^*$ between the produced $K$ mesons. This analysis was based on three different parameter sets for the pair production. For the 70\% subsample and with best parameters, $3680\pm 370$ $K^+K^-$ pairs was found to be compared to $3900\pm 410$ $K^+K^-$ extracted by means of the Coulomb model. Knowing the efficiency of the TOF cut for background suppression, the total number of detected $K^+K^-$ pairs was evaluated to be around $40000\pm 10\%$, which agrees with the result from the 30\% subsample. The $K^+K^-$ pair number in the 50\% subsample differs from the two other values by about three standard deviations, confirming -- as discussed in the paper -- that experimental data in this subsample is less reliable.
