Determining the gluonic gravitational form factors of the proton-猫眼课题宝

DOI：

10.1038/s41586-023-05730-4

发表时间：

2022-07

期刊：

Nature

影响因子：

64.8

通讯作者：

中科院分区：

综合性期刊1区

文献类型：

作者：

B. Duran;Z. Meziani;S. Joosten;M. Jones;S. Prasad;C. Peng;W. Armstrong;H. Atac;E. Chudakov;H. Bhatt;D. Bhetuwal;M. Boer;A. Camsonne;J. Chen;M. Dalton;N. Deokar;M. Diefenthaler;J. Dunne;Lamiaa El Fassi;E. Fuchey;H. Gao;D. Gaskell;O. Hansen;F. Hauenstein;D. Higinbotham;S. Jia;A. Karki;C. Keppel;P. King;H. Ko;X. Li;R. Li;D. Mack;S. Malace;M. McCaughan;R. McClellan;R. Michaels;D. Meekins;M. Paolone;L. Pentchev;E. Pooser;A. Puckett;R. Radloff;M. Rehfuss;P. Reimer;S. Riordan;B. Sawatzky;A. Smith;N. Sparveris;H. Szumila-Vance;S. Wood;J. Xie;Z. Ye;C. Yero;Z. Zhao

质子是宇宙中所有可见物质的主要组成部分之一。它的内在属性包括电荷、质量和自旋。这些都是由量子色动力学（QCD）所描述的其基本成分夸克和胶子的复杂动力学产生的。直到今天，利用电子散射夸克组分之间共享的电荷和自旋一直是积极研究的主题。一个例子是质子电荷半径的新的精确测量。相比之下，人们对质子的内部质量密度知之甚少，主要是由胶子携带的能量所控制，由于胶子不携带电磁电荷，很难通过电子散射获得。在目前的工作中，我们选择使用一个小的颜色偶极子，粒子，通过它的阈值光生探测这种胶子引力密度。从我们的数据中，我们第一次确定了质子的胶子引力形状因子，它编码了它的质量密度。我们使用了各种方法，并确定在所有情况下，质量半径明显小于电荷半径。在某些情况下，所确定的半径与晶格QCD的第一性原理预测非常一致。这项工作为更深入地理解胶子在为可见物质提供引力质量方面的重要作用铺平了道路。

The proton is one of the main building blocks of all visible matter in the universe. Among its intrinsic properties are its electric charge, mass, and spin. These emerge from the complex dynamics of its fundamental constituents, quarks and gluons, described by the theory of quantum chromodynamics (QCD). Using electron scattering its electric charge and spin, shared among the quark constituents, have been the topic of active investigation until today. An example is the novel precision measurement of the proton's electric charge radius. In contrast, little is known about the proton's inner mass density, dominated by the energy carried by the gluons, which are hard to access through electron scattering since gluons carry no electromagnetic charge. In the present work we chose to probe this gluonic gravitational density using a small color dipole, theparticle, through its threshold photoproduction. From our data we determined, for the first time, the proton's gluonic gravitational form factors, which encode its mass density. We used a variety of methods and determined in all cases a mass radius that is notably smaller than the electric charge radius. In some cases, the determined radius is in excellent agreement with first-principle predictions from lattice QCD. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.

Determining the gluonic gravitational form factors of the proton

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