The polarimetric observations of the protoplanetary disk around HL Tau have shown the scattering-induced polarization at ALMA Band 7, which indicates that the maximum dust size is ∼100 μm, while the spectral energy distribution (SED) has suggested that the maximum dust size is approximately a millimeter. To solve the contradiction, we investigate the impact of differential settling of dust grains on the SED and polarization. If the disk is optically thick, a longer observing wavelength traces more interior layers, which would be dominated by larger grains. We find that the SED of the center part of the HL Tau disk can be explained with millimeter-sized grains for a broad range of turbulence strength, while 160 μm–sized grains cannot be explained unless the turbulence strength parameter α _t is lower than 10⁻⁵. We also find that the observed polarization fraction can be potentially explained with a maximum dust size of 1 mm if α _t ≲ 10⁻⁵, although models with 160 μm–sized grains are also acceptable. However, if the maximum dust size is ∼3 mm, the simulated polarization fraction is too low to explain the observations even if the turbulence strength is extremely small, indicating a maximum dust size of ≲1 mm. The degeneracy between 100 μm– and millimeter-sized grains can be solved by improving the ALMA calibration accuracy or polarimetric observations at (sub)centimeter wavelengths.

HL Tau 周围原行星盘的偏振观测显示在 ALMA 波段 7 处发生散射诱导极化，这表明最大尘埃尺寸为 100 μ m，而光谱能量分布 (SED) 表明最大尘埃尺寸大约是一毫米。为了解决这个矛盾，我们研究了尘埃颗粒的差异沉降对SED和极化的影响。如果圆盘在光学上很厚，更长的观测波长会追踪更多的内部层，这些层将由更大的颗粒主导。我们发现 HL Tau 盘中心部分的 SED 可以用毫米级颗粒来解释，以获得广泛的湍流强度，而 160 μ除非湍流强度参数α _t低于10 ^{-5 ，}否则无法解释m 尺寸的晶粒。我们还发现，如果α _t ≲ 10 ^-5，观察到的极化分数可以用 1 毫米的最大尘埃大小来潜在地解释，尽管具有 160微米大小的颗粒的模型也是可以接受的。然而，如果最大尘埃尺寸为~3 mm，即使湍流强度非常小，模拟的极化分数也太低而无法解释观测结果，表明最大尘埃尺寸为≲1 mm。100 μ之间的简并性可以通过提高 ALMA 校准精度或（亚）厘米波长的偏振观测来解决米级和毫米级晶粒。