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Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth  [PDF]
G. Bellini,J. Benziger,D. Bick,G. Bonfini,D. Bravo,M. Buizza Avanzini,B. Caccianiga,L. Cadonati,F. Calaprice,P. Cavalcante,A. Chavarria,A. Chepurnov,D. D'Angelo,S. Davini,A. Derbin,A. Empl,A. Etenko,K. Fomenko,D. Franco,C. Galbiati,S. Gazzana,C. Ghiano,M. Giammarchi,M. G?ger-Neff,A. Goretti,L. Grandi,C. Hagner,E. Hungerford,Aldo Ianni,Andrea Ianni,V. Kobychev,D. Korablev,G. Korga,D. Kryn,M. Laubenstein,T. Lewke,E. Litvinovich,B. Loer,P. Lombardi,F. Lombardi,L. Ludhova,G. Lukyanchenko,I. Machulin,S. Manecki,W. Maneschg,G. Manuzio,Q. Meindl,E. Meroni,L. Miramonti,M. Misiaszek,R. M?llenberg,P. Mosteiro,V. Muratova,L. Oberauer,M. Obolensky,F. Ortica,K. Otis,M. Pallavicini,L. Papp,L. Perasso,S. Perasso,A. Pocar,G. Ranucci,A. Razeto,A. Re,A. Romani,N. Rossi,R. Saldanha,C. Salvo,S. Sch?nert,H. Simgen,M. Skorokhvatov,O. Smirnov,A. Sotnikov,S. Sukhotin,Y. Suvorov,R. Tartaglia,G. Testera,D. Vignaud,R. B. Vogelaar,F. von Feilitzsch,J. Winter,M. Wojcik,A. Wright,M. Wurm,J. Xu,O. Zaimidoroga,S. Zavatarelli,G. Zuzel
Physics , 2013, DOI: 10.1088/1475-7516/2013/08/049
Abstract: 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.
Muon-induced neutron production and detection with GEANT4 and FLUKA  [PDF]
H. M. Araujo,V. A. Kudryavtsev,N. J. C. Spooner,T. J. Sumner
Physics , 2004, DOI: 10.1016/j.nima.2005.02.004
Abstract: We report on a comparison study of the Monte Carlo packages GEANT4 and FLUKA for simulating neutron production by muons penetrating deep underground. GEANT4 is found to generate fewer neutrons at muon energies above ~100 GeV, by at most a factor of 2 in some materials, which we attribute mainly to lower neutron production in hadronic cascades. As a practical case study, the muon-induced neutron background expected in a 250 kg liquid-xenon WIMP dark matter detector was calculated and good agreement was found for the recoil event rates. The detailed model of neutron elastic scattering in GEANT4 was also shown to influence the nuclear recoil spectrum observed in the target, which is presently a shortcoming of FLUKA. We conclude that both packages are suited for this type of simulation, although further improvements are desirable in both cases.
CNO and pep neutrino spectroscopy in Borexino: Measurement of the deep underground production of cosmogenic 11C in organic liquid scintillator  [PDF]
Borexino Collaboration
Statistics , 2006, DOI: 10.1103/PhysRevC.74.045805
Abstract: Borexino is an experiment for low energy neutrino spectroscopy at the Gran Sasso underground laboratories. It is designed to measure the mono-energetic $^7$Be solar neutrino flux in real time, via neutrino-electron elastic scattering in ultra-pure organic liquid scintillator. Borexino has the potential to also detect neutrinos from the \emph{pep} fusion process and the CNO cycle. For this measurement to be possible, radioactive contamination in the detector must be kept extremely low. Once sufficiently clean conditions are met, the main background source is $^{11}$C, produced in reactions induced by the residual cosmic muon flux on $^{12}$C. In the process, a free neutron is almost always produced. $^{11}$C can be tagged on an event by event basis by looking at the three-fold coincidence with the parent muon track and the subsequent neutron capture on protons. This coincidence method has been implemented on the Borexino Counting Test Facility data. We report on the first event by event identification of \emph{in situ} muon induced $^{11}$C in a large underground scintillator detector. We measure a $^{11}$C production rate of 0.130 $\pm$ 0.026 (stat) $\pm$ 0.014 (syst) day$^{-1}$ ton$^{-1}$, in agreement with predictions from both experimental studies performed with a muon beam on a scintillator target and \emph{ab initio} estimations based on the $^{11}$C producing nuclear reactions.
Measurement of CNGS muon neutrino speed with Borexino  [PDF]
Borexino Collaboration
Physics , 2012, DOI: 10.1016/j.physletb.2012.08.052
Abstract: We have measured the speed of muon neutrinos with the Borexino detector using short-bunch CNGS beams. The final result for the difference in time-of-flight between a =17 GeV muon neutrino and a particle moving at the speed of light in vacuum is {\delta}t = 0.8 \pm 0.7stat \pm 2.9sys ns, well consistent with zero.
Study of Cosmogenic Neutron Backgrounds at LNGS  [PDF]
A. Empl,R. Jasim,E. Hungerford,P. Mosteiro
Physics , 2012,
Abstract: Cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically neutrons dominate this background as they are particularly difficult to shield and detect in a veto system. Since actual background data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. This means that validation of any simulation code is necessary to assure reliable results. This work studies the validation of the FLUKA simulation code, and reports the results of a simulation of cosmogenic background for a liquid argon two-phase detector embedded within a water tank and liquid scintillator shielding.
Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND  [PDF]
The KamLAND Collaboration
Physics , 2009, DOI: 10.1103/PhysRevC.81.025807
Abstract: Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in $\nu$ detectors, double-$\beta$-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of $^{11}$C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, the neutron production yield in the KamLAND liquid scintillator is measured to be $(2.8 \pm 0.3) \times 10^{-4} \mu^{-1} g^{-1} cm^{2}$. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.
Seasonal modulation in the Borexino cosmic muon signal  [PDF]
Davide D'Angelo,for the Borexino Collaboration
Physics , 2011, DOI: 10.7529/ICRC2011/V04/0510
Abstract: Borexino is an organic liquid scintillator detector located in the underground Gran Sasso National Laboratory (Italy). It is devoted mainly to the real time spectroscopy of low energy solar neutrinos via the elastic scattering on electrons in the target mass. The data taking campaign started in 2007 and led to key measurements of 7}Be and 8B solar neutrinos as well as antineutrinos from the earth (geo-neutrinos) and from nuclear power reactors. Borexino is also a powerful tool for the study of cosmic muons that penetrate the Gran Sasso rock coverage and thereby induced signals such as neutrons and radioactive isotopes which are today of critical importance for upcoming dark matter and neutrino physics experiments. Having reached 4y of continuous data taking we analyze here the muon signal and its possible modulation. The muon flux is measured to be (3.41+-0.01)E-4/m2/s. A modulation of this signal with a yearly period is observed with an amplitude of (1.29+-0.07)% and a phase of (179+-6) d, corresponding to June 28th. Muon rate fluctuations are compared to fluctuations in the atmospheric temperature on a daily base, exploiting the most complete atmospheric data and models available. The distributions are shown to be positively correlated and the effective temperature coefficient is measured to be alpha_T = 0.93 +- 0.04. This result is in good agreement with the expectations of the kaon-inclusive model at the laboratory site and represents an improvement over previous measurements performed at the same depth.
Supernova Neutrino Detection in Borexino  [PDF]
L. Cadonati,F. P. Calaprice,M. C. Chen
Physics , 2000, DOI: 10.1016/S0927-6505(01)00129-3
Abstract: We calculated the expected neutrino signal in Borexino from a typical Type II supernova at a distance of 10 kpc. A burst of around 110 events would appear in Borexino within a time interval of about 10 s. Most of these events would come from the reaction channel $\bar{\nu}_e+p\to e^++n$, while about 30 events would be induced by the interaction of the supernova neutrino flux on $^{12}$C in the liquid scintillator. Borexino can clearly distinguish between the neutral-current excitations $^{12}{C}(\nu,\nu')^{12}{C}^*$(15.11 MeV) and the charged-current reactions $^{12}{C}(\nu_e,e^-)^{12}{N}$ and $^{12}{C}(\bar{\nu}_e,e^+)^{12}{B}$, via their distinctive event signatures. The ratio of the charged-current to neutral-current neutrino event rates and their time profiles with respect to each other can provide a handle on supernova and non-standard neutrino physics (mass and flavor oscillations).
Geoneutrinos in Borexino  [PDF]
Marco G. Giammarchi,Lino Miramonti
Physics , 2006, DOI: 10.1007/s11038-006-9106-6
Abstract: This paper describes the Borexino detector and the high-radiopurity studies and tests that are integral part of the Borexino technology and development. The application of Borexino to the detection and studies of geoneutrinos is discussed.
A. Fluka Study of Underground Cosmogenic Neutron Production  [PDF]
A Empl,E. V. Hungerford,R. Jasim,P. Mosteiro
Physics , 2014, DOI: 10.1088/1475-7516/2014/08/064
Abstract: Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail the predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.
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