Alexander Derbin - Academia.edu (original) (raw)

Papers by Alexander Derbin

Unknown eBooks, 1992

Results of experiments on elastic scattering of reactor neutrino on electron are presented. Limit... more Results of experiments on elastic scattering of reactor neutrino on electron are presented. Limitation on the magnetic moment of neutrino mu(sub nu) less than 1.8 x 10(exp -10) mu(sub B) was obtained. The existing uncertainty in the neutrino spectrum confines the possible limit on magnetic moment of approximately 3 x 10(exp -11) mu(sub B) value for detectors with approximately 0.1 MeV threshold.

Nuclear Physics B - Proceedings Supplements, 2013

ABSTRACT This paper summarizes the main recent results of the Borexino experiment, a liquid scint... more ABSTRACT This paper summarizes the main recent results of the Borexino experiment, a liquid scintillator neutrino detector of unprecedented radiopurity currently running at the Laboratori Nazionali del Gran Sasso in Italy. Particularly, the paper is focused on the precision measurement of the 7Be solar neutrino flux, on the search of its day–night modulation, and on the first detection of pep neutrinos. The paper also covers a recent measurement of the CNGS neutrinos speed made in May 2012. A short discussion about the forthcoming scientific program on solar neutrinos, geoneutrinos, and sterile neutrino searches is included at the end.

Nuclear Physics B - Proceedings Supplements, 2003

Nuclear Physics B - Proceedings Supplements, 2011

Borexino is an experiment for low energy neutrino spectroscopy at the Gran Sasso underground labo... more 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 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 in situ muon induced 11 C in a large underground scintillator detector. We measure a 11 C production rate of 0.130 ± 0.026 (stat) ± 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 ab initio estimations based on the 11 C producing nuclear reactions.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

ABSTRACT We report the direct measurement of the Be-7 solar neutrino signal rate performed with t... more ABSTRACT We report the direct measurement of the Be-7 solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso and the search for a day-night asymmetry of this interaction rate. The interaction rate of the 0.862 MeV Be-7 neutrinos is 46 +/- 1.6(stat)(-1.6)(+1.5)(syst) counts/(day . 100 ton). The hypothesis of no oscillation for this solar neutrinos is inconsistent with our measurement at the 5.8 sigma C.L Our result is the first direct measurement of solar neutrinos with an accuracy better than 5%. We report the survival probability for solar v(e) in the transition region between matter-enhanced and vacuum-driven oscillations. The measured day night asymmetry is A(dn) = 0.001 +/- 0.012 (stat) +/- 0.007 (syst), in agreement with the predicition of MSW-LMA neutrino [13] oscillations. This result discourages MSW oscillations with mixing parameters in the LOW region at more than 8.5 sigma, meaning that this region is, for the first time, strongly rejected without the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics. (C) 2012 Elsevier B.V. All rights reserved.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1999

Several portable instruments are designed using previously reported CdTe detector technology. The... more Several portable instruments are designed using previously reported CdTe detector technology. These can be divided into three groups according to their energy ranges: (1)3–30keV XRF analyzers, (2)5–120keV wide range XRF analyzers and (3)γ-ray spectrometers for operation up to 1500keV. These instruments are used to inspect several hundreds of samples in situ during a working day in applications such as a

Journal of Physics: Conference Series, 2012

We observed, for the first time, solar neutrinos in the 1.0-1.5 MeV energy range. We measured the... more We observed, for the first time, solar neutrinos in the 1.0-1.5 MeV energy range. We measured the rate of pep solar neutrino interactions in Borexino to be (3.1±0.6stat±0.3syst) counts/(day·100 ton) and provided a constraint on the CNO solar neutrino interaction rate of <7.9 counts/(day·100 ton) (95% C.L.). The absence of the solar neutrino signal is disfavored at 99.97% C.L., while the absence of the pep signal is disfavored at 98% C.L. This unprecedented sensitivity was achieved by adopting novel data analysis techniques for the rejection of cosmogenic 11 C, the dominant background in the 1-2 MeV region. Assuming the MSW-LMA solution to solar neutrino oscillations, these values correspond to solar neutrino fluxes of (1.6±0.3)×10 8 cm −2 s −1 and <7.7×10 8 cm −2 s −1 (95% C.L.), respectively, in agreement with the Standard Solar Model. These results represent the first measurement of the pep neutrino flux and the strongest constraint of the CNO solar neutrino flux to date. PACS numbers: 13.35.Hb, 14.60.St, 26.65.+t, 95.55.Vj, 29.40.Mc Over the past 40 years solar neutrino experiments have proven to be sensitive tools to test both astrophysical and elementary particle physics models. Solar neutrino detectors have demonstrated that stars are powered by nuclear fusion reactions. Two distinct processes, the main pp fusion chain and the sub-dominant CNO cycle, are expected to produce solar neutrinos with different energy spectra and fluxes. Until now only fluxes from the pp chain have been measured: 7 Be, 8 B, and, indirectly, pp. Experiments involving solar neutrinos and reactor anti-neutrinos have shown that solar neutrinos undergo flavor oscillations.

Journal of Cosmology and Astroparticle Physics, 2012

We have measured the muon flux at the underground Gran Sasso National Laboratory (3800 m w.e.) to... more We have measured the muon flux at the underground Gran Sasso National Laboratory (3800 m w.e.) to be (3.41 ± 0.01) · 10 −4 m −2 s −1 using four years of Borexino data. A modulation of this signal is observed with a period of (366±3) days and a relative amplitude of (1.29 ± 0.07)%. The measured phase is (179 ± 6) days, corresponding to a maximum on the 28 th of June. Using the most complete atmospheric data models available, muon rate fluctuations are shown to be positively correlated with atmospheric temperature, with an effective coefficient α T = 0.93 ± 0.04. This result represents the most precise study of the muon flux modulation for this site and is in good agreement with expectations.

Journal of Cosmology and Astroparticle Physics, 2013

The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratori... more 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 Y n = (3.10 ± 0.11) · 10 −4 n/(µ · (g/cm 2 )). The distance profile between the parent muon track and the neutron capture point has the average value λ = (81.5 ± 2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for 12 N, 12 B, 8 He, 9 C, 9 Li, 8 B, 6 He, 8 Li, 11 Be, 10 C and 11 C. 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 11 C yield for which both codes return about 50% lower values. The predicted µ-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.

Journal of Experimental and Theoretical Physics Letters, 2002

Results of background measurements with a prototype of the Borexino detector were used to obtain ... more Results of background measurements with a prototype of the Borexino detector were used to obtain bounds on the lifetime of radiative neutrino decay ν H ν L + γ . The new lower limit for the lifetime of pp and 7 Be neutrinos is τ c.m. ( ν H ν L + γ )/ m ν ≥ 4.2 × 10 3 s eV -1 ( α = 0). It is more than an order of magnitude stronger than the value obtained in previous experiments using nuclear reactors and accelerators. © 2002 MAIK "Nauka/Interperiodica".

JETP Letters, 2012

The axio-electric effect in silicon atoms is sought for solar axions appearing owing to bremsstra... more The axio-electric effect in silicon atoms is sought for solar axions appearing owing to bremsstrahlung and the Compton process. Axions are detected using a Si(Li) detector placed in a low-background setup. As a result, a model-independent constraint on the axion-electron coupling constant |gAe| ≤ 2.2 × 10 −10 has been obtained, which leads to the bounds mA ≤ 7.9 eV and mA ≤ 1.4 keV for the mass of the axion in the DFSZ and KSVZ models, respectively (90% C.L.).

Journal of Experimental and Theoretical Physics Letters, 1997

The European Physical Journal C, 2013

A search for axioelectric absorption of solar axions produced in the p + d → 3 He + γ (5.5 MeV) r... more A search for axioelectric absorption of solar axions produced in the p + d → 3 He + γ (5.5 MeV) reactions has been performed with a BGO detector placed in a lowbackground setup. A model-independent limit on an axionnucleon and axion-electron coupling constant has been obtained: |g Ae × g 3 AN | < 2.9 × 10 −9 for 90% confidence level. The constrains of the axion-electron coupling have been obtained for hadronic axion with masses in (0.1 -1) MeV range: |g Ae | ≤ (1.4 − 9.7) × 10 −7 .

The European Physical Journal C, 2004

The Pauli exclusion principle (PEP) has been tested for nucleons (n, p) in 12 C and 16 O nuclei, ... more The Pauli exclusion principle (PEP) has been tested for nucleons (n, p) in 12 C and 16 O nuclei, using the results of background measurements with the prototype of the Borexino detector, the Counting Test Facility (CTF). The approach consisted of a search for γ, n, p and/or α's emitted in a non-Paulian transition of 1P -shell nucleons to the filled 1S 1/2 shell in nuclei. Similarly, the Pauli-forbidden β ± decay processes were searched for. Due to the extremely low background and the large mass (4.2 tons) of the CTF detector, the following most stringent up-to-date experimental bounds on PEP violating transitions of nucleons have been established: τ ( 12 C → 12 C + γ) > 2.1 · 10 27 y, τ ( 12 C → 11 B + p) > 5.0 · 10 26 y, τ ( 12 C( 16 O) → 11 C( 15 O) + n) > 3.7 · 10 26 y, τ ( 12 C → 8 Be + α) > 6.1 · 10 23 y, τ ( 12 C → 12 N + e − + νe) > 7.6 · 10 27 y and τ ( 12 C → 12 B + e + + νe) > 7.7 · 10 27 y, all at 90% C.L.

The European Physical Journal C, 2008

Results of background measurements with a prototype of the Borexino detector were used to search ... more Results of background measurements with a prototype of the Borexino detector were used to search for 478 keV solar axions emitted in the M1-transitions of 7 Li * . The Compton conversion of axion to a photon A + e → e + γ, axioelectric effect A + e + Z → e + Z, decay of axion in two photons A → 2γ and Primakoff conversion on nuclei A + Z → γ + Z are considered. The upper limit on constants of interaction of axion with electrons, photons and nucleons -g Ae g AN ≤ (1.0-2.4) × 10 −10 at m A ≤ 450 keV and g Aγ g AN ≤ 5 × 10 −9 GeV −1 at m A ≤ 10 keV are obtained (90%c.l.). For heavy axions with mass at 100 < m A < 400 keV the limits g Ae < (0.7-2.0) × 10 −8 and g Aγ < 10 −9 -10 −8 are obtained in assumption that g AN depends on m A as for KSVZ axion model. These limits are stronger than obtained in previous laboratory-based experiments using nuclear reactor and artificial radioactive sources.

The European Physical Journal C, 2009

A search for resonant absorbtion of 14.4 keV solar axions by 57 Fe target was performed. The Si(L... more A search for resonant absorbtion of 14.4 keV solar axions by 57 Fe target was performed. The Si(Li) detector placed inside the low-background setup was used to detect the γ-quanta appearing in the deexcitation of 14.4 keV nuclear level: A + 57 Fe → 57 Fe * → 57 Fe + γ. The new upper limit for the hadronic axion mass have been obtained: mA ≤ 151 eV (90% C.L.) (S=0.5, z=0.56).

Zeitschrift f�r Physik A Hadrons and Nuclei, 1995

Lower limits on the half-life of the betabeta(2v+0v) decay of76Ge to the excited states in76Se ha... more Lower limits on the half-life of the betabeta(2v+0v) decay of76Ge to the excited states in76Se have been obtained using the results of low-background measurements with a HPGe detector surrounded by passive germanium shielding: T1/2(0+ --> 2{1/+}) >1.1 · 1021 y, T1/2(0+ --> 0{1/+}) > 1.7 · 1021 y, T1/2(0+ --> 22/+) > 1.4 ·1021 y.

The European Physical Journal A, 2013

We have studied the α decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coinci... more We have studied the α decays of 214 Po into 210 Pb and of 212 Po into 208 Pb tagged by the coincidence with the preceding β decays from 214 Bi and 212 Bi, respectively. The employed 222 Rn, 232 Th, and 220 Rn sources were sealed inside quartz vials and inserted in the Counting Test Facility at the underground Gran Sasso National Laboratory in Italy. We find that the mean lifetime of 214 Po is (236.00 ± 0.42(stat) ± 0.15(syst))µs and that of 212 Po is (425.1 ± 0.9(stat) ± 1.2(syst)) ns. Our results, obtained from data with signal-to-background ratio larger than 1000, reduce the overall uncertainties and are compatible with previous measurements.

… C/C OF PIS'MA V …, 1993

Work continues at the Rovno nuclear power plant to measure the cross section for neutrino scatter... more Work continues at the Rovno nuclear power plant to measure the cross section for neutrino scattering by electrons. 1 The primary reason for the current interest in this scattering is that it would yield the most stringent limitations on the magnetic moment of a neutrino.