## 3 Results  
Estimates show [17] that in order to distinguish the contours of the building against the ground by muon radiography, the difference in the density of the stone, used in the construction, and the surrounding soil should be at least 5%. The material characteristics and thickness of the construction walls are not known, and a preliminary simulation of muon passing through the building and their registration by emulsion detectors was carried out with several different values of wall thickness and density. In the calculations, loam of density 1.78 g/cm\({}^{3}\) was taken as soil material; sandstone of two density options (2.00 g/cm\({}^{3}\) and 2.65 g/cm\({}^{3}\)) was taken as wall material. Simulation of the muon flux passage for the test experiment was carried out with consideration of the emulsion detector design based on Geant4 software package [18]. When specifying the geometry inside the building studied (the widths and lengths of the corridors and the dome), the sizes shown in Figure 4 were used. Figure 3: One of the nuclear emulsion detectors mounted inside the object at a depth of about 10 m at an angle of 45\({}^{\circ}\) in the direction of a wall. Figure 2: Scheme of the arrangement of detectors in the investigated construction. (**a**) Schematic side view: the central detector for measuring the vertical flux of muons, and the side detectors for radiography of the walls. The guide cones indicate the areas visible by each detector. (**b**) Schematic view from above. Letters A, B, C, D show the arrangement of emulsion detectors; A for West; B for North; C for South; D for East. Analysis of the detector D data is presented in the text. The initial muon pulses were specified according to the experimentally obtained distribution [19]. The dependence on the zenith angle \(\theta\) was approximated by the function \(\mathrm{F}(\theta)\sim\cos^{2}(\theta)\); the distribution on the azimuth angle \(\varphi\) was taken uniform. In the calculations, a threshold value of the minimum pulse was taken above which a particle passes through a substance without stopping. Its value depends on the amount of substance in the particle path and, accordingly, varies with the angle of observation. Therefore, part of the initial muon spectrum above this minimum pulse is used in the simulation. The value of the recorded particle flux depends on the amount of material passed. Thus, for sandstone of  
Figure 4: (**a**) The cross-section view of the construction, dimensions are given in mm. (**b**) Computer reconstruction of underground building  
density 2.3 g/cm\({}^{3}\) the flux passing through 3 m, 5 m and 10 m is attenuated by 35%, 2.5-fold and 5-fold at minimal pulse values of 1.56 GeV/s, 2.6 GeV/s and 5.25 GeV/s, respectively. When a flux of particles passes through a layer of a substance of any thickness, up to several kilometers, the output will always contain particles of small energies that have pulses close to the minimal value when entering the substance. They are scattered rather strongly and affect the angle distribution of the registered particle fluxes. To take into account the blurring of the distribution of such particles due to their multiple scattering, and to optimize the simulation time, a special algorithm has been developed that reduces the effect of this mechanism. Figure 5 presents the simulation results in the form of distributions of the number of muons registered by emulsion detectors as functions of the angular variables _tx_ and _ty_. The angular variables _tx_ and _ty_ represent the tangents of the slope angles of tracks in projections on the planes (xz, yz) and are related to the customary angular variables as follows:  
\[tx=\frac{dx}{dz}=\tan\theta\cos\varphi;ty=\frac{dy}{dz}=\tan\theta\sin\varphi,\]  
where \(\varphi\) and \(\theta\) are azimuth and zenith angles. Figure 5: Results of simulation of the number of muons registered by emulsion detectors (presented in angular variables _tx_ and _ty_).