Recently, we suggested that low-energy beta-beam neutrinos can be very useful
for the study of supernova neutrino interactions. In this paper, we examine the
use of a such experiment for the analysis of a supernova neutrino signal. Since
supernova neutrinos are oscillating, it is very likely that the terrestrial
spectrum of supernova neutrinos of a given flavor will not be the same as the
energy distribution with which these neutrinos were first emitted. We
demonstrate the efficacy of the proposed method for untangling multiple
neutrino spectra. This is an essential feature of any model aiming at gaining
information about the supernova mechanism, probing proto-neutron star physics,
and understanding supernova nucleosynthesis, such as the neutrino process and
the r-process. We also consider the efficacy of different experimental
approaches including measurements at multiple beam energies and detector
configurations.Comment: 13 pages, 11 figures, accepted for publication in Phys. Rev. 

Jachowicz, N.

McLaughlin, G. C.

Volpe, C.

English

arXiv

13 pages, 11 figures, accepted for publication in Phys. Rev. CRecently, we suggested that low-energy beta-beam neutrinos can be very useful for the study of supernova neutrino interactions. In this paper, we examine the use of a such experiment for the analysis of a supernova neutrino signal. Since supernova neutrinos are oscillating, it is very likely that the terrestrial spectrum of supernova neutrinos of a given flavor will not be the same as the energy distribution with which these neutrinos were first emitted. We demonstrate the efficacy of the proposed method for untangling multiple neutrino spectra. This is an essential feature of any model aiming at gaining information about the supernova mechanism, probing proto-neutron star physics, and understanding supernova nucleosynthesis, such as the neutrino process and the r-process. We also consider the efficacy of different experimental approaches including measurements at multiple beam energies and detector configurations

Mclaughlin, G. C.

HAL-IN2P3

Untangling supernova-neutrino oscillations with beta-beam data

Neutrinos are the only particles able to reach the earth straight from the center of a core-collapse supernova. But the information that can be gathered from their signal in a terrestrial detector is limited by the fact that little experimental data on neutrino-nucleus interactions exists and by uncertainties in theoretical calculations. Neutrino oscillations are a further complication : the energy distribution of the neutrinos in a terrestrial detector will be different from the spectrum with which these neutrinos were first emitted. We show that low-energy beta-beams can provide ways to extract information about supernova-neutrinos and their oscillations in a model-independent way

Jachowicz, Natalie

McLaughlin, Gail

Volpe, Cristina

Ghent University Academic Bibliography

PoS(NIC X)107Untangling supernova-neutrino oscillations withbeta-beam dataNatalie Jachowicz∗†Ghent University, Department of Subatomic and Radiation Physics, Proeftuinstraat 86, B-9000Gent, BelgiumE-mail: natalie.jachowicz@ugent.beG.C. McLaughlinDepartment of Physics, North Carolina State University, Raleigh, North Carolina 27695E-mail: Gail_McLaughlin@ncsu.eduC. VolpeInstitut de Physique Nucléaire, F-91406 Orsay cedex, FranceE-mail: volpe@ipno.in2p3.frNeutrinos are the only particles able to reach the earth straight from the center of a core-collapsesupernova. But the information that can be gathered from their signal in a terrestrial detectoris limited by the fact that little experimental data on neutrino-nucleus interactions exists and byuncertainties in theoretical calculations. Neutrino oscillations are a further complication : the en-ergy distribution of the neutrinos in a terrestrial detector will be different from the spectrum withwhich these neutrinos were first emitted. We show that low-energy beta-beams can provide waysto extract information about supernova-neutrinos and their oscillations in a model-independentway.10th Symposium on Nuclei in the CosmosJuly 27 - August 1 2008Mackinac Island, Michigan, USA∗Speaker.†N.J. thanks the Research Foundation Flanders (FWO) for financial support. G.C.M. acknowledges support fromthe Department of Energy, under contract DE-FG02-02ER41216. C.V. acknowledges the financial support of the EC un-der the FP6 ’Research Infrastructure Action - Structuring the European Research Area’ EURISOL DS Project, ContractNumber 515768 RIDS.c© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/PoS(NIC X)107Untangling supernova-neutrino oscillations with beta-beam data Natalie Jachowicz1. IntroductionUnderstanding the mechanism of a Type-II core-collapse supernova is a longstanding problem.While the general nature of these events is understood to be the explosion that results from thecollapse of a massive star, a completely self-consistent model of the explosion does not yet exist.Weak interaction physics and neutrino-interactions are widely regarded as central players in theexplosion mechanism. The core is so hot and dense that even the neutrinos are trapped in thecollapse. Afterwards, these neutrinos scatter out of the core on a timescale of about ten seconds,taking away with them the vast majority of the gravitational binding energy released in the collapse.Terrestrial neutrino telescopes can provide precious information about the processes going onin the center of the supernova. The information that can be inferred by the terrestrial detectionof supernova neutrinos however suffers from the fact that the available data on neutrino-nucleuscross sections in this energy region is limited, due to the very small cross sections and due tothe lack of monochromatic neutrino beams. Moreover the accuracy of theoretical predictions isinfluenced by uncertainties and model dependencies. The flexibility of the proposed beta-beamexperiments [1, 2], where neutrinos are produced in the decay of a primary beam of boosted ionscan remedy some of these problems. The energy range interesting for supernova neutrino-physicscan be covered by low-energy beta-beams [?, 4, 5].In this contribution, we examine the use of a beta-beam experiment for the analysis of a super-nova signal in a terrestrial detector. We demonstrate that beta-beam measurements can be of greathelp in the analysis of this signal, thereby avoiding the uncertainties involved in the theoreticalmodeling of neutrino-nucleus interactions and the limitations brought along by the fact that com-mon neutrino beams are not mono-energetic. The central idea of the proposed technique consistsof a reconstruction of supernova-neutrino responses using experimental beta-beam data, hence it isalso of direct use for the prediction of neutrinonucleosynthesis reactions.2. ProcedureNeutrinos and antineutrinos of different flavors decouple at different sites in the stellar core.In terms of energy, the supernova neutrinos are emitted with a low-energy and a high-energy com-ponent, the first associated with electron (anti)neutrinos, the latter with the heavy-flavor mu and tauneutrinos. Common parametrization are Fermi-Dirac or power-law spectra with average energiesranging from roughly 12 to 22 MeV, and varying width. Similar to supernova-neutrino spectra,beta-beam spectra are characterized by long tails, while their average energy and precise shapedepend on the boost-factor γ of the primary beam and the geometry of the experimental setup [6].The core of the proposed technique consists of the construction of normalized linear combina-tions nNγ of beta-beam spectra nγi that then represent the supernova neutrino spectra :nNγ (εν) =N∑i=1ainγi(εν). (2.1)The boost factors γi=1,···,N and the expansion coefficients ai=1,···,N are varied to minimize the ex-pression ∫ενdεν∣∣nNγ(εν)−nSN(εν)∣∣ . (2.2)2PoS(NIC X)107Untangling supernova-neutrino oscillations with beta-beam data Natalie JachowiczIn this way we obtain a synthetic spectrum n f itNγ (εν) that is the best fit to the supernova-neutrinoenergy-distribution nSN(εν) for particular values of the average energy and width.0.00010.0010.010.115 20 25 30 35 40dσ/dω (10-42 cm2  MeV-1 )<εν>= 14 MeV, α=3.016Oω (MeV)0.010.1115 20 25 30 35 40dσ/dω (10-42 cm2  MeV-1 )<εν>= 18 MeV, α=2.0ω (MeV)0.010.1115 20 25 30 35 40dσ/dω (10-42 cm2  MeV-1 )<εν>= 22 MeV, α=3.0ω (MeV)0.0010.010.115 20 25 30 35 40dσ/dω (10-42 cm2  MeV-1 )<εν>= 18 MeV, α=4.0ω (MeV)Figure 1: Comparison between differential cross sections for the reaction 16O(ν ,ν’)16O* folded with su-pernova neutrino spectra with different average energies and widths (full line), and with the correspondingsynthetic spectra with N = 3 (dashed) and N = 5 (dotted) beta-beam spectra in the linear combination.Figure 1 shows that the response produced by a synthetic spectrum i.e. the differential crosssection folded with the linear combination of Eq.(2.1) is very similar to the supernova neutrinosignal in a detector. Hence, using appropriate linear combinations of beta-beam data allows for veryaccurate predictions of supernova-neutrino responses without having to rely on the intermediatesteps of nuclear structure calculations [7].In fact, the accuracy of the fit is so satisfying that it opens ways to a model-independent studyof supernova neutrino oscillations [8]. If we assume that neutrinos of all flavors are emitted inequal numbers, there will be twice as much high-energy neutrinos as low-energy neutrinos. Ina terrestrial detector, both types will interact through neutral-current reactions. Charged-currentdetection channels are only accessible for electron-type neutrinos, as the production of a massivemu- or tau lepton requests more energy than is available for supernova neutrinos. Oscillations willtransform the high and low-energy components in a different way. This does not affect the neutralcurrent signal, as it is not sensitive to the neutrino flavor. In terms of the energy spectra, the neutral3PoS(NIC X)107Untangling supernova-neutrino oscillations with beta-beam data Natalie Jachowicz0.20.10.30.40.50.60.70.80.910.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1(0.1,0.9)(0.2,0.8)(0.3,0.7)(0.4,0.6)(0.5,0.5)(0.6,0.4)(0.7,0.3)(0.8,0.2)(0.9,0.1)         l                                        l                            h                                       h<εnSN>=14 MeV, αnSN=2.0 ; <εnSN>=16 MeV, αnSN=4.0IfitRfit0.20.30.40.50.60.70.80.91(0.1,0.9)(0.2,0.8)(0.3,0.7)(0.4,0.6)(0.5,0.5)(0.6,0.4)(0.7,0.3)(0.8,0.2)(0.9,0.1)         l                                        l                            h                                       h<εnSN>=16 MeV, αnSN=3.5 ; <εnSN>=21 MeV, αnSN=2.00.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1IfitRfit0.20.30.40.50.60.70.80.910.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1(0.1,0.9)(0.2,0.8)(0.3,0.7)(0.4,0.6)(0.5,0.5)(0.6,0.4)(0.7,0.3)(0.8,0.2)(0.9,0.1)         l                                        l                            h                                       h<εnSN>=15 MeV, αnSN=3.0 ; <εnSN>=16 MeV, αnSN=3.0IfitRfit0.20.30.40.50.60.70.80.91(0.1,0.9)(0.2,0.8)(0.3,0.7)(0.4,0.6)(0.5,0.5)(0.6,0.4)(0.7,0.3)(0.8,0.2)(0.9,0.1)         l                                        l                            h                                       h<εnSN>=15 MeV, αnSN=3.5 ; <εnSN>=17 MeV, αnSN=2.50.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1IfitRfitFigure 2: Extraction of the oscillation parameters R f it and I f it from a fit of the expressions in Eqs. (2.7)and (2.8) to the neutral SNC(ω) =∫ενdεν (nlSN(εν)+ 2nhSN(εν ))σNC(εν ,ω), and charged-current SCC(ω) =∫ενdεν(R nlSN(εν )+ I nhSN(εν ))σCC(εν ,ω) supernova-neutrino signal in an oxygen detector. For each fittedpoint the original parameter values (R, I) are given between brackets.current signal can then be written asSNC(ω) =∫ενdεν(nlSN(ενe) + 2nhSN(ενµ ,εντ )+ nlSN(ενe)+ 2nhSN(ενµ ,εντ ))σNC(εν ,ω), (2.3)where the energy integration runs over all neutrino flavors. The energy distribution of the neutrinosresponsible for the charged current signal will be distorted according to :SCC(ω) =∫ενdεν(R nlSN(εν) + I nhSN(εν))σCC(εν ,ω), (2.4)with R denoting the fraction of electron-type neutrinos that remained unchanged and I the fractionof heavy-flavor neutrinos that were transformed into electron neutrinos. In the equation above R +I = 1, for any given energy of the neutrinos. For simplicity, in our example below, we assume thatthe neutrinos will evolve either completely adiabatically or completely non-adiabatically so that inaddition, both R and I are constant as a function of neutrino energy, although our analysis could beexpanded to include the more general case. The parameters R and I contain the information aboutoscillations that the supernova neutrinos are carrying and can be recovered from the signal in thedetector in two steps. First, from a set of constructed spectra nNγ , the two linear combinations of4PoS(NIC X)107Untangling supernova-neutrino oscillations with beta-beam data Natalie Jachowiczbeta-beam responsesnl, f itNγ (εν) =N∑i=1al, f iti nγi(εν), (2.5)andnh, f itNγ (εν) =N∑i=1ah, f iti nγi(εν), (2.6)for which2∫ενdεν(nl, f it (εν) + 2nh, f it(εν))σNC(εν), (2.7)minimizes the difference with the neutral current detector signal from Eq.( 2.3) are selected. Theresulting two sets of expansion parameters (a f it,li ; i = 1,N) and (af it,hi ; i = 1,N) are then used toconstruct combinations∫ενdεν(R f it nl, f it(εν) + I f it nh, f it(εν))σCC(εν), (2.8)and seek for the oscillation parameters R f it and I f it that yield the best agreement between theexpression of Eq. (2.8) and the signal of Eq. (2.4).The results are presented in figure 2, showing that the agreement between the original (R, I)and the reconstructed parameters (R f it , I f it ) is very good. Moreover, the reconstruction is stableagainst noise [8].Concluding, we presented a method that may be of help in the analysis of a future supernova-neutrino signal. We propose to use the technique as a lever to make advantage of beta-beam data inuntangling multiple neutrino spectra and disentangling the oscillation characteristics from mixedspectra. This is an essential feature of any model aiming at gaining information about the super-nova mechanism, probing proto-neutron star physics, and understanding supernova nucleosynthe-sis, such as the neutrino process and the r-process. We have shown that the procedure is effectivein extracting oscillation parameters from the signal in a terrestrial detector, illustrating the use ofthe technique for gathering information about the supernova as well as its neutrinos.References[1] P. Zucchelli, Phys. Lett. B 532, 166 (2002).[2] http://beta-beam.web.cern.ch/beta-beam/.[3] C. Volpe, J. Phys. G30, L1 (2004) [arXiv:hep-ph/0303222].[4] P. S. Amanik and G. C. McLaughlin, Phys. Rev. C 75, 065502 (2007) [arXiv:hep-ph/0702207].[5] C. Volpe, J. Phys. G34, R1 (2007) [arXiv:hep-ph/0605033].[6] G. C. McLaughlin, Phys. Rev. C 70, 045804 (2004) [arXiv:nucl-th/0404002].[7] N. Jachowicz and G. C. McLaughlin, Phys. Rev. Lett. 96, 172301 (2006) [arXiv:nucl-th/0604046].[8] N. Jachowicz, G. C. McLaughlin, and C. Volpe, Phys. Rev. C 77, 055501 (2008).5

Recently, we suggested that low-energy P-beam neutrinos can be very useful for the study of supernova-neutrino interactions. In this article, we examine the use of a such experiment for the analysis of a supernova-neutrino signal. Because supernova neutrinos are oscillating, it is very likely that the terrestrial spectrum of supernova neutrinos of a given flavor will not be the same as the energy distribution with which these neutrinos were first emitted. We demonstrate the efficacy of the proposed method for untangling multiple neutrino spectra. This is an essential feature of any model aiming at gaining information about the supernova mechanism, probing proto-neutron star physics, and understanding supernova nucleosynthesis, such as the neutrino process and the r-process. We also consider the efficacy of different experimental approaches including measurements at multiple beam energies and detector configurations

Untangling supernova-neutrino oscillations with beta-beam data

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