Inclusive cross section and double helicity asymmetry for π0 production in p+p collisions at √s=200 GeV:: Implications for the polarized gluon distribution in the proton
Inclusive cross section and double helicity asymmetry for π0 production in p+p collisions at √s=200 GeV:: Implications for the polarized gluon distribution in the proton
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DOI：
10.1103/physrevd.76.051106
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发表时间：
2007-09-01
影响因子：
5
通讯作者：
Zolin, L.
中科院分区：
文献类型：
--
作者：
Adare, A.;Afanasiev, S.;Zolin, L.
PHENIX实验展示了2005年相对论重离子对撞机在s=200 GeV的根能量下进行极化质子碰撞的结果，包括中快度的π（0）产生。给出了横动量p（T）=0.5 ~ 20 GeV/c时的非极化截面结果，将已发表的数据范围扩展到较低和较高的p（T）。当p（T）< 1 GeV/c时，截面可用p（T）的指数函数描述;当p（T）> 2 GeV/c时，截面可用微扰QCD描述。双螺旋度不对称性A（LL）的基础上提出的5个因素的改善不确定性相比，以前公布的结果，由于改善光束偏振的50%，和更高的综合光度。这些测量对质子中的胶子极化很敏感。利用一个有代表性的胶子极化模型，证明了胶子自旋对质子自旋的贡献受到明显的限制。
The PHENIX experiment presents results from the Relativistic Heavy Ion Collider 2005 run with polarized proton collisions at root s=200 GeV, for inclusive pi(0) production at midrapidity. Unpolarized cross section results are given for transverse momenta p(T)=0.5 to 20 GeV/c, extending the range of published data to both lower and higher p(T). The cross section is described well for p(T)< 1 GeV/c by an exponential in p(T), and, for p(T)> 2 GeV/c, by perturbative QCD. Double helicity asymmetries A(LL) are presented based on a factor of 5 improvement in uncertainties as compared to previously published results, due to both an improved beam polarization of 50%, and to higher integrated luminosity. These measurements are sensitive to the gluon polarization in the proton. Using one representative model of gluon polarization it is demonstrated that the gluon spin contribution to the proton spin is significantly constrained.