Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth

The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Yn =(3.10+-0.11)10-4 n/({\mu} (g/cm2)). The distance profile between the parent muon track and the neutron capture point has the average value {\lambda} = (81.5 +- 2.7)cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for 12N, 12B, 8He, 9C, 9Li, 8B, 6He, 8Li, 11Be, 10C and 11C. All results are compared with Monte Carlo simulation predictions using the Fluka and Geant4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being 11C yield for which both codes return about 50% lower values. The predicted {\mu}-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.

[1]  V. Vlachoudis,et al.  The FLUKA Code: Developments and Challenges for High Energy and Medical Applications , 2014 .

[2]  L. Cadonati,et al.  Measurement of geo-neutrinos from 1353 days of Borexino , 2013, 1303.2571.

[3]  P. Mosteiro,et al.  Study of Cosmogenic Neutron Backgrounds at LNGS , 2012, 1210.2708.

[4]  L. Cadonati,et al.  Cosmic-Muon Flux and Annual Modulation in Borexino at 3800 m Water-Equivalent Depth , 2012, 1202.6403.

[5]  L. Cadonati,et al.  First evidence of pep solar neutrinos by direct detection in Borexino , 2012, Physical review letters.

[6]  Andrea Ianni,et al.  Precision measurement of the (7)Be solar neutrino interaction rate in Borexino. , 2011, Physical review letters.

[7]  L. Cadonati,et al.  Muon and cosmogenic neutron detection in Borexino , 2011, 1101.3101.

[8]  Michael Wurm,et al.  Measurement of the solar 8B neutrino rate with a liquid scintillator target and 3 MeV energy threshold in the Borexino detector , 2010 .

[9]  Michael Wurm,et al.  Observation of geo-neutrinos , 2010 .

[10]  I. G. Park,et al.  Measurement of the atmospheric muon charge ratio with the OPERA detector , 2010, 1003.1907.

[11]  M. Decowski,et al.  Production of radioactive isotopes through cosmic muon spallation in KamLAND , 2009 .

[12]  et al,et al.  The Borexino detector at the Laboratori Nazionali del Gran Sasso , 2008, 0806.2400.

[13]  L. Cadonati,et al.  Direct measurement of the 7Be solar neutrino flux with 192 days of borexino data. , 2008, Physical review letters.

[14]  F. Cerutti,et al.  The FLUKA code: Description and benchmarking , 2007 .

[15]  Markus Brugger,et al.  Validation of the FLUKA Monte Carlo code for predicting induced radioactivity at high-energy accelerators , 2006 .

[16]  S. Incerti,et al.  Geant4 developments and applications , 2006, IEEE Transactions on Nuclear Science.

[17]  L. Cadonati,et al.  Cosmogenic 11C production and sentivity of organic scintillator detectors to pep and CNO neutrinos , 2004, hep-ph/0411002.

[18]  F. Feilitzsch,et al.  Neutron Flux at the Gran Sasso Underground Laboratory Revisited , 2003, hep-ex/0312050.

[19]  F. von Feilitzsch,et al.  Neutron Flux Underground Revisited , 2003 .

[20]  E. al.,et al.  Measurement of the residual energy of muons in the Gran Sasso underground laboratories , 2002, hep-ex/0207043.

[21]  E. Katsavounidis,et al.  The MACRO Collaboration: , 2003 .

[22]  L. Cadonati,et al.  Supernova neutrino detection in Borexino , 2000, hep-ph/0012082.

[23]  A. Fasso,et al.  Predicting neutron production from cosmic ray muons , 2001, hep-ex/0101049.

[24]  G. Bruni,et al.  Measurement of the neutron flux produced by cosmic ray muons with LVD at Gran Sasso , 1999 .

[25]  Irradiation Facilities Proceedings of the Specialists' Meeting on Shielding Aspects of Accelerators, Targets and Irradiation Facilities : Arlington, Texas (USA) 28-29 April 1994 , 1995 .

[26]  J. Hong Multiple Muon Measurements with MACRO , 1994 .