Measurement of the formation rate of muonic hydrogen molecules
Measurement of the formation rate of muonic hydrogen molecules
复制标题
μ子氢分子形成速率的测量
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
P. Winter
中科院分区：
文献类型：
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作者：
MuCap Collaboration V. A. Andreev;T. Banks;R. Carey;T. Case;S. Clayton;K. Crowe;J. Deutsch;J. Egger;S. Freedman;V. Ganzha;T. Gorringe;F. Gray;D. Hertzog;M. Hildebrandt;P. Kammel;B. Kiburg;S. Knaack;P. Kravtsov;A. Krivshich;B. Lauss;K. Lynch;E. Maev;O. Maev;F. Mulhauser;C. Petitjean;G. Petrov;R. Prieels;G. N. Schapkin;G. G. Semenchuk;M. Soroka;V. Tishchenko;A. Vasilyev;A. Vorobyov;M. Vznuzdaev;P. Winter
背景：速率λppμ表征了在pμ原子与氢的碰撞中ppμ分子的形成。在测量质子上的基本弱µ子俘获反应以确定伪标量耦合GP时，俘获发生在原子态和分子态两个方面。因此，要正确解释这些实验，需要具有λppμ的知识。目的：最近，MUCAP实验测量了单重态pΛ原子的俘获率S，采用低密度的活性靶来抑制Ppμ的形成[V.Andreev(MUCAP Collaboration)，Phys.莱特牧师。110,012504(2013)]PRLTAO0031-900710.1103/PhysRevLett.110.012504.然而，考虑到这个实验前所未有的精确度，λppμ中现有的实验知识必须得到改进。方法：MuCap实验从超纯氢中的Muon消失率推导出弱俘获率。通过在氢中掺入20ppm的Ar，引入了一种竞争形成ppμ的过程，该过程允许从观察到的衰变电子的时间分布中提取λppμ。结果：ppμ形成率为λppμ=(2.0 1±0.0 6stat±0.0 3sys)×10 6s-1。该结果更新了在上述MUCAP出版物中使用的λPPμ值。结论：与以前的实验相比，精密度提高了2.5倍，而且测量是在几乎相同的条件下进行的，这使得λppμ引起的不确定度减少到对ΛS和GP的总体不确定度的较小贡献，正如MUCAP实验所确定的那样。与我们之前发布的结果相比，λppμ的最终值使Λ、S和GP各自的不确定度减少了不到十分之一
Background: The rate λppμ characterizes the formation of ppμ molecules in collisions of muonic pμ atoms with hydrogen. In measurements of the basic weak muon capture reaction on the proton to determine the pseudoscalar coupling gP, capture occurs from both atomic and molecular states. Thus knowledge of λppμ is required for a correct interpretation of these experiments. Purpose: Recently the MuCap experiment has measured the capture rate ΛS from the singlet pμ atom, employing a low-density active target to suppress ppμ formation [V. Andreev (MuCap Collaboration), Phys. Rev. Lett. 110, 012504 (2013)]PRLTAO0031-900710.1103/PhysRevLett.110.012504. Nevertheless, given the unprecedented precision of this experiment, the existing experimental knowledge in λppμ had to be improved. Method: The MuCap experiment derived the weak capture rate from the muon disappearance rate in ultrapure hydrogen. By doping the hydrogen with 20 ppm of argon, a competing process to ppμ formation was introduced, which allowed the extraction of λppμ from the observed time distribution of decay electrons. Results: The ppμ formation rate was measured as λppμ=(2.01±0.06stat±0.03sys)×106s-1. This result updates the λppμ value used in the abovementioned MuCap publication. Conclusions: The 2.5× higher precision compared to earlier experiments, and the fact that the measurement was performed under nearly identical conditions as the main data taking, reduces the uncertainty induced by λppμ to a minor contribution to the overall uncertainty of ΛS and gP, as determined in the MuCap experiment. Our final value for λppμ shifts ΛS and gP by less than one-tenth of their respective uncertainties compared to our results published earlier