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Gas infall motions play a crucial role in high-mass star formation and arecharacterized by observable signatures in the form of blue-shifted asymmetricspectral line profiles ("blue profiles"). However, the connection between blueprofiles and infall motions is unclear due to complex gas motions at parsecscales. In this study, we present the results of an HCN (4-3) mapping surveyconducted with the JCMT, towards 38 massive clumps exhibiting blue profiles inHCO+ (3-2). We extract 34 HCN cores from the 38 observed fields. Thecore-averaged spectra show various line profiles, indicating that blue-profileHCO+ (3-2) does not guarantee the same in HCN (4-3). Through non-LTE radiationtransfer calculations, we attribute the low detection rate of high-$J$ blueprofiles to a combination of insufficient HCN (4-3) opacity and intricate gasmotion across different density layers. The comparison between the MALT90 andBGPS line surveys highlights the importance of appropriate tracers, highspectral resolution, and column density thresholds when searching for blueprofiles. We select 11 reliable infall candidates and adopt the Hill5 model tofit the infall velocity of 0.2-1.9 km/s, corresponding to 5% to 74% offree-fall velocity. Assuming a spherically collapsing model, we estimate themedian and mean mass infall rates to be 4.5E-3 and 7.6E-3 Msun/year,respectively. The consistency of the mass infall rates among differenttransitions suggests a steady accretion process from the clump gas envelope tothe inner region.

Clump-scale Gas Infall in High-mass Star Formation: a Multi-transition View with JCMT HCN (4--3) Mapping