First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process
First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process
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DOI：
10.22323/1.297.0243
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发表时间：
2018-01
期刊：
影响因子：
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通讯作者：
M. Aghasyan;R. Akhunzyanov;G. Alexeev;M. Alexeev;A. Amoroso;V. Andrieux;N. Anfimov;V. Anosov
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文献类型：
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作者：
M. Aghasyan;R. Akhunzyanov;G. Alexeev;M. Alexeev;A. Amoroso;V. Andrieux;N. Anfimov;V. Anosov
欧洲核子研究中心的COMPASS实验作为其方案的一部分，通过测量半包容性DIS和最近的Drell-Yan过程中与自旋（in）有关的方位角不对称性，探索核子的横向自旋结构。在2002年到2010年之间，COMPASS进行了一系列的SIDIS测量，使用纵向极化的μ子束撞击横向极化的$^6LiD$或$NH_3$目标。Drell-Yan测量用$\pi^-$光束与横向偏振的$NH_3$目标相互作用，从2015年开始运行，并将在2018年继续进行。在这封信中的第一个测量的横向自旋相关的方位角不对称性的π诱导的Drell-Yan过程的报告。测量的不对称性，让访问不同的横向动量相关（TMD）的部分子分布函数（PDF）的提取使用的双μ子事件与不变质量之间的4.3~\gvcw\，和8.5~\gvcw。最近的COMPASS SIDIS测量是在硬尺度上获得的，与这些DY结果相当。这为检验在QCD中预测的Sivers TMD PDF的符号变化和其他横向动量依赖部分子分布函数的（伪）普适特征提供了一种独特的可能性。
The COMPASS experiment at CERN, as part of its programme addresses the exploration of the transverse spin structure of the nucleon by measuring spin (in)dependent azimuthal asymmetries in semi-inclusive DIS and, recently, also in Drell-Yan processes. Between 2002 and 2010 COMPASS performed a series of SIDIS measurements, using a longitudinally polarized muon beam impinging on transversely polarized $^6LiD$ or $NH_3$ targets. Drell-Yan measurements with a $\pi^-$ beam interacting with a transversely polarized $NH_3$ target started with the 2015 run and will be continued in 2018. In this Letter the first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan process is reported. Measured asymmetries giving access to different transverse-momentum-dependent (TMD) parton distribution functions (PDFs) are extracted using dimuon events with invariant mass between 4.3~\gvcw\, and 8.5~\gvcw. A recent COMPASS SIDIS measurement was obtained at a hard scale comparable to that of these DY results. This provides a unique possibility to test predicted in QCD sign change of the Sivers TMD PDF and other (pseudo-)universal features of transvers momentum dependent parton distribution functions.