Abstract

A linearly polarized photon can be quantized from the Lorentz-boosted electromagnetic field of a nucleus traveling at ultra-relativistic speed. When two relativistic heavy nuclei pass one another at a distance of a few nuclear radii, the photon from one nucleus may interact through a virtual quark-antiquark pair with gluons from the other nucleus forming a short-lived vector meson (e.g. ${\rho^0}$). In this experiment, the polarization was utilized in diffractive photoproduction to observe a unique spin interference pattern in the angular distribution of ${\rho^0\rightarrow\pi^+\pi^-}$ decays. The observed interference is a result of an overlap of two wave functions at a distance an order of magnitude larger than the ${\rho^0}$ travel distance within its lifetime. The strong-interaction nuclear radii were extracted from these diffractive interactions, and found to be $6.53\pm 0.06$ fm ($^{197} {\rm Au }$) and $7.29\pm 0.08$ fm ($^{238} {\rm U}$), larger than the nuclear charge radii. The observable is demonstrated to be sensitive to the nuclear geometry and quantum interference of non-identical particles.

Figure 2A

Data from Figure 2A

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The invariant mass distribution of pi+pi- pairs collected from Au+Au and U+U collisions.
Figure 2B

Example location

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Two-dimensional $\rho^0$ momentum distribution from Au+Au collisions.
Figure 2C

Example location

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Two-dimensional $\rho^0$ momentum distribution from Au+Au collisions.
Figure 2D

Example location

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Two-dimensional $\rho^0$ momentum distribution from U+U collisions.
Figure 3A

Data from Figure 3A

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The $P_T^2 \approx |t|$ distribution of $\rho^0$ collected from Au+Au collisions.
Figure 3B

Data from Figure 3B

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The $P_T^2 \approx |t|$ distribution of $\rho^0$ collected from U+U collisions.
Figure 3C

Data from Figure 3C

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The $P_T^2 \approx |t|$ distribution of $\rho^0$ with $|\phi| < \pi/24$ collected from Au+Au collisions.
Figure 3D

Data from Figure 3D

10.17182/hepdata.132921.v1/t8

The $P_T^2 \approx |t|$ distribution of $\rho^0$ with $|\phi - \pi/2| < \pi/24$ collected from Au+Au collisions.
Figure 4A

Data from Figure 4A

10.17182/hepdata.132921.v1/t9

The $\phi$ distribution for $\pi^+\pi^-$ pairs with a pair transverse momentum less than 60 MeV and and an invariant mass...
Figure 4A pAu data

Data from Figure 4A for pAu

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The $\phi$ distribution for $\pi^+\pi^-$ pairs with a pair transverse momentum less than 60 MeV and and an invariant mass...
Figure 4B

Data from Figure 4B

10.17182/hepdata.132921.v1/t11

The $2 \langle \cos{2 \phi} \rangle$ distribution vs. pair transverse momentum for $\pi^+\pi^-$ pairs with an invariant mass between 650...
Figure 4B pAu data

Data from Figure 4B (pAu data)

10.17182/hepdata.132921.v1/t12

The $2 \langle \cos{2\phi} \rangle$ distribution vs. pair transverse momentum for $\pi^+\pi^-$ pairs with an invariant mass between 650 and...
Figure 5B

Data from Figure 5B

10.17182/hepdata.132921.v1/t13

The $2 \langle \cos{2\phi} \rangle$ distribution vs. pair transverse momentum for $\pi^+\pi^-$ pairs with an invariant mass between 650 and...
Figure 5A

Data from Figure 5A

10.17182/hepdata.132921.v1/t14

The distribution of extracted radii R vs. $\phi$ from Au+Au and U+U.

Figure 2A

Figure 2B

Figure 2C

Figure 2D

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4A

Figure 4A pAu data

Figure 4B

Figure 4B pAu data

Figure 5B

Figure 5A

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