The muon intensity and angular distribution in the shallow-underground laboratory Felsenkeller in Dresden, Germany have been studied using a portable muon detector based on the close cathode chamber design. Data has been taken at four positions in Felsenkeller tunnels VIII and IX, where a new 5 MV underground ion accelerator is being installed, and in addition at four positions in Felsenkeller tunnel IV, which hosts a low-radioactivity counting facility. At each of the eight positions studied, seven different orientations of the detector were used to compile a map of the upper hemisphere with 0.85 • angular resolution. The muon intensity is found to be suppressed by a factor of 40 due to the 45 m thick rock overburden, corresponding to 140 meters water equivalent. The angular data are matched by two different simulations taking into account the known geodetic features of the terrain: First, simply by determining the cutoff energy using the projected slant depth in rock and the known muon energy spectrum, and second, in a Geant4 simulation propagating the muons through a column of rock equal to the known slant depth. The present data are instrumental for studying muon-induced effects at these depths and also in the planning of an active veto for accelerator-based underground nuclear astrophysics experiments. [34,35] that such a veto may reduce the observed background in γ-detectors typical for in-beam nuclear astrophysics experiments to a level that is close to the background in the same detectors deep underground, underlining the importance of a proper muon veto.This work is organized as follows. The underground site is described in sec. 2. Section 3 introduces the experimental setup, including the REGARD muon telescope used here, and experimental procedures. The data analysis and results are presented in sec. 4. The data are then matched, first, by a calculation based on the known rangeenergy relation, and second, by a Monte Carlo simulation using the Geant4 framework (sec. 5). A discussion is offered in sec. 6. The conclusions, a summary and an outlook are given in sec. 7. Description of the underground site studiedThe shallow-underground site Felsenkeller is located in the Plauenscher Grund district, inside the city of Dresden, Germany. The site extends along the Weißeritz river, a tributary of the Elbe, and was used as a quarry until the 18th century, then converted to a brewery, which in turn closed in 1991. The terrain is characterized by a steep cliff that runs from Northeast to Southwest, an approximately flat high plain at 200 m a.s.l. and a river floodplain at 140 m a.s.l. (Fig. 1).Nine horizontal storage tunnels were dug into the rock from 1856 to 1859. All nine tunnels have horizontal access and are interconnected in a comb-like structure (Fig. 2). The site is protected from cosmic rays by an overburden of 45 m of hornblende monzonite rock, part of the "Meißner Massiv" formation. The density of rock samples taken from the tunnels VIII and IX was here found to be (2.69±0.06) g/cm 3 . The hornblende mon...

We observed single and double proton emissions in the 14 O + 4 He interaction by the thick target inverse kinematic (TTIK) method at initial energy for 14 O at 32.7 MeV. We found that the protons mainly originate from the resonance excitation of states in 18 Ne. The observed states in 18 Ne decay by protons mainly to proton unstable states in 17 F. It was found that the decay of a state in 18 Ne at E ex = 8.45 MeV demonstrates the features of a decay by a correlated proton pair. The observed properties of the 14 O + 4 He interaction make a previous interpretation for the rate of 14 O( 4 He, p) 17 F at astrophysical energies suspect. We show how the TTIK method should be modified to obtain the data of astrophysical interest.

The production of 22 Na in ONe novae can be influenced by the 22 Mg(p,γ ) 23 Al reaction. To investigate this reaction rate at stellar energies, we have determined the asymptotic normalization coefficient (ANC) for 22 Mg + p → 23 Al through measurements of the ANCs in the mirror nuclear system 22 Ne + n → 23 Ne. The peripheral neutron-transfer reactions 13 C( 12 C, 13 C) 12 C and 13 C( 22 Ne, 23 Ne) 12 C were studied. The identical entrance and exit channels of the first reaction make it possible to extract independently the ground-state ANC in 13 C. Our experiment gives C 2 p 1/2 ( 13 C) = 2.24 ± 0.11 fm −1 , which agrees with the value obtained from several previous measurements. The weighted average for all the obtained C 2 p 1/2 is 2.31 ± 0.08 fm −1 . This value is adopted to be used in obtaining the ANCs in 23 Ne. The differential cross sections for the reaction 13 C( 22 Ne, 23 Ne) 12 C leading to the J π = 5/2 + and 1/2 + states in 23 Ne have been measured at 12 MeV/u. Optical model parameters for use in the DWBA calculations were obtained from measurements of the elastic scatterings 22 Ne + 13 C and 22 Ne + 12 C. The extracted ANC for the ground state in 23 Ne, C 2 d 5/2 = 0.86 ± 0.08 ± 0.12 fm −1 , is converted to its corresponding value in 23 Al using mirror symmetry to give C 2 d 5/2 ( 23 Al) = (4.63 ± 0.77) × 10 3 fm −1 . The astrophysical S factor S(0) for the 22 Mg(p,γ ) reaction was determined to be 0.96 ± 0.11 keV b. The consequences for nuclear astrophysics are discussed.

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