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Study of rare processes with the Borexino detector

Study of rare processes with the Borexino detector. Alexander Derbin, Kirill Fomenko on behalf of BOREXINO Collaboration. Detector’s design. Stainless Steel Sphere: 2212 photomultipliers 1350 m 3. Scintillator: 270 t PC+PPO in a 150  m thick nylon vessel. Water Tank:

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Study of rare processes with the Borexino detector

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  1. Study of rare processes with the Borexino detector Alexander Derbin, Kirill Fomenko on behalf of BOREXINO Collaboration

  2. Detector’s design Stainless Steel Sphere: 2212 photomultipliers 1350 m3 Scintillator: 270 t PC+PPO in a 150 m thick nylon vessel Water Tank: gand n shield mwaterČdetector 208 PMTs in water 2100 m3 Nylon vessels: Inner: 4.25 m Outer: 5.50 m Design is based on the principle of graded shielding Carbon steel plates 15th Lomonosov Conference on Elementary Particle Physics

  3. SSS internal view 15th Lomonosov Conference on Elementary Particle Physics

  4. Neutrino magnetic moment SM with mν = 0, μν = 0 T – kinetic energy of scattered e Ev – neutrino energy SM with mν> 0, μeff > 0 additional EM term influencing the cross section and thus the spectral shape Sensitivity enhanced @ low energies The spectrum of recoil electrons caused by the magnetic moment was additionally included in theoretical (fitting) function. The minimum of χ2 corresponds to zero value of the magnetic moment. An upper limit on μeff was obtained in a standard way - minimum values χ2 were determined at various fixed values of μeff, the remaining parameters being free: μeff≤ 5.4 x 10-11mB (90% C.L.) The obtainedμefflimit is model independent and free of systematic errors. 15th Lomonosov Conference on Elementary Particle Physics

  5. Neutrino magnetic moment μkj - matrix element of the neutrino electromagnetic moments; Ak(Eν,L)- the amplitude of the k-mass state For the MSW oscillation solution (under the assumption θ13 = 0): where P1 and P2 are the probabilities for observing respective mass eigenstates, or where Pee is the probability for observing electron flavor eigenstate. For the most probable values of P1, Pee, θ12 andθ13 one can obtain the following limits: 15th Lomonosov Conference on Elementary Particle Physics

  6. Check for non-Paulian (NP) transitions in nuclei p γn p protons 1P1/2 n neutrons 1P1/2 1P3/2 16.0 MeV 1P3/2 19.0 ν π ν π W e- W 1S1/2 33.9 MeV e+ 1S1/2 36.3 The non-Paulian (NP) transitions were searched for in 12C nuclei contained in scintillator. The transition of nucleons from the P-shell to the filled S-shell will result in excited non-Paulian nuclei 12CNP; de-excitation of those NP nuclei can go through emitting of γ, p, n, d, α, ...Similarly, the Pauli-forbidden  - decay processes can be considered. The approach consisted in searching for γ, n, p... emitted in a NP transitions and Pauli-forbidden - decays. 15th Lomonosov Conference on Elementary Particle Physics

  7. Channel Q3p, MeV Q3n, MeV Evis, MeV E.M. STRONG WEAK 12C→12CNP+γ 17.90.9 17.70.6 16.4÷19.4 12C→11BNP+p 6.30.9 7.81.0 4.6÷8.3 12C→11CNP+n 6.50.9 4.50.6 3.2÷7.3 12C→8BeNP+α 3.00.6 2.90.9 0.07÷0.25 12C→12NNP+e-+ - 18.90.9 0.0÷18.9 12C→12BNP+e++ 17.80.9 - 0.0÷17.8 Q-values and energy-allowed transitions The signature of the transitions with two particle in the final state is Gaussian peak in the measured spectra. In case of neutrino emission  spectra are registered. In order to obtain the energy of detected particles one have to take into account the recoil energy of nuclei. Transitions with Q<0 15th Lomonosov Conference on Elementary Particle Physics

  8. The Borexino responses for searched processes 1. 12C → 12CNP + γ (16.4 MeV) Inner Vessel plus 1m thick layer of buffer 2.12C → 12NNP + e- + ν (18.9 MeV) Inner Vessel 3.12C → 11BNP + p (4.6 and 8.3 MeV) Fiducial Volume 4.12C → 11CNP + n (3.0 and 6.0 MeV) Inner Vessel 15th Lomonosov Conference on Elementary Particle Physics

  9. Events spectra, 485 days live time 1. Raw events spectrum 2. 2ms cut after each muon applied 3. Events within time interval 0.7s after muons crossing SSS are removed (16 days of dead time introduced) 9Li (178 ms), 8He (119 ms) There are no events above 12.5 MeV 15th Lomonosov Conference on Elementary Particle Physics

  10. New limits obtained with the Borexino The Borexino results are 3-4 orders of magnitude stronger then CTF ones The limits for NP transitions in 12C with p-,n- and β±- emissions are the best to date The limit on the NP transition in 12C with γ-emission is comparable to the same result for 16O obtained using Kamiokande data for γBR=1 Borexino has unique parameters to study NP transitions with low Q 15th Lomonosov Conference on Elementary Particle Physics

  11. The relative strength of the NP transitions to the Normal Transitions The NP transitions with emission of , n or p and ,e-pair can be induced by electromagnetic, strong and weak interactions. The obtained limits on lifetime can be converted to limits on the rates of transitions (λNP=1/τNP) and on relative strength of NP-transitions to the normal ones. The decay width of nuclear E1 γ-transition from P- to S-shell given by the Weisskopf estimate is Γγ~ 1.5 keV. The ratio λNP/ λNTis less then 2.2.10-57 (90% c.l.) The width of hadrons emission is 2-3 orders larger width of γ-transition. The measured width of S-hole state in 12C is Γh ≈ 12 MeV. The detection of p or n give a more stringent limit on the relative strength of NP transitions then the detection of γ’s if one can set a similar limit on the lifetime for both decays. The obtained limit is λNP/ λNT ≤ 4.1.10-60. The NP β± -transitions are first-order forbidden P→S transitions. The log(ft) values for such first forbidden transitions range from 6 to 9, conservative value (9) corresponds to life-time τβ~ 500 and level width Γβ= ħλ= ħ/τ=1.4.10-18 eV, so λNP/ λNT ≤ 2.1.10-35 15th Lomonosov Conference on Elementary Particle Physics

  12. Concept of the axions Problem of CP conservation in strong interactions: As it follows from the experimental limit on neutron’s dipole moment the upper limit on the CP-violating parameter is θ ≤ 10-9. This term is relatively small in comparison with all the other parameters of the QCD Lagrangian, and this fact still remains a mystery over a few decades. • A natural solution of the "strong CP problem" was found by R. D. Peccei and H. R. Quinn in 1977 by introducing a new global chiral symmetry U(1)PQ. Spontaneous breaking of that symmetry (at the energy scale fA) allows compensate precisely CP-violating member in the QCD Lagrangian. • The axion concept was introduced in a theory by S. Weinberg and F.Wilczek (1978) who showed that the solution to the problem of CP conservation in strong interactions proposed by Peccei and Quinn should lead to the existence of a neutral pseudoscalar particle; the originalWWPQ axion model contained some certain strict predictions for the coupling constants and had beendisproved by experiments. 15th Lomonosov Conference on Elementary Particle Physics 12

  13. "Invisible" axions • Two classes of new theoretical models of an ”invisible” axion retained this particle in the form required for solving the CP problem of strong interactions (and at the same time suppressed it’s interaction with matter): “hadronic”, orKSVZ (Kim, Shifman, Vainshtein, Zakharov) axion model that postulates existence of the additional heavy quark;“GUT”,orDFSZ(Dine, Fischer, Srednicki, Zhitnycki) axion model that requires additional Higgs field. • The axion mass is determined by the axion decay constant fA: wherezandw – mass ratios for light quarks (z = mu/md 0.56, w = mu/ms 0.029), mπandfπ – mass and decay constant ofπ-meson. As the scale of Peccei-Quinn symmetry violation (fA) in both models is arbitrary and can be extended up to the Plank mass ≈ 1019 GeV,the interaction between an axion and matter is suppressed. 15th Lomonosov Conference on Elementary Particle Physics 13

  14. Interactions with matter • The coupling of the axion field to the photons, electrons and nucleons: gAN: as a pseudoscalar particle axion can be absorbed and emitted in nuclear magnetic-type transitions; gAγ: А → 2γdecay (a) and Primakoff (b) effect (axion- -photon conversion in the electromagnetic field); gAe: axio-electric (c) andcompton-like(d) effects 15th Lomonosov Conference on Elementary Particle Physics 14

  15. Axion production channels in the Sun If axion does exist, the Sun should be an intense source of axions. There are 5 main axion formation processes inside the stars: • Reactions of the main solar cycle.The most intensive flux would be expected as a result of the formation of the 3He nucleus and М1-transitions in 7Li nuclei (gAN) : p + d → 3He + A (5.5 MeV) (current work) 7Be + e– → 7Li*+ ν; 7Li* → 7Li + A (478 keV) (CTF) • Monochromatic axions would be produced in magnetic transitions in nuclei whose low-lying levels were excited by the high temperature of the Sun (57Fe,14 keV) (gAN) • Axions could be produced efficiently on the Sun due to photon-axion conversion in an electromagnetic field of plasma (ЕА ~0.5-10 keV) (gAγ) 4. Axion bremsstrahlung: е– + Z → e– + Z +A (gAe) 5. Axion-compton processes:γ + е– → е–+ А (gAe) 15th Lomonosov Conference on Elementary Particle Physics 15

  16. If the proton is captured in the S-state then axion could be radiated instead of -quantum.Axion flux is proportionalto the flux of рр-neutrino (Фνрр= 6.0.1010ν/cm2s) which is known. Axions from the proton capture reaction The ratio of the probability of a nuclear transition with axion production (ωA) to the probability of a magnetic transition (ω) is:well defined in both types of models 15th Lomonosov Conference on Elementary Particle Physics

  17. Borexino response functions for axion processes 1 – axioelectric effect 2 – Compton conversion 3 – Primakoff conversion 4 – Axion decay A→2γ The Monte Carlo method has been used to simulate the Borexino response to electrons and γ-quanta appearing in axion interactions. The response function of the Borexino to the axion's was found by MC simulations based on GEANT4 code, taking into account the effect of ionization quenching and the dependence of the registered charge on the distance from the detector's center. The uniformly distributed γ's and e’s were simulated inside the inner vessel, but the response functions were obtained for events restored inside the FV. The MC candidate events are selected by the same cuts that was applied for real data selection. The signature of all reactions is peak at ~5.5 MeV energy. 15th Lomonosov Conference on Elementary Particle Physics

  18. Data spectrum, 737.8 days live time 1. Raw events spectrum (correlated events excluded) 2. OD + ID muons excluded 3. 2ms cut after each muon + events within time interval 6.5s after muons crossing SSS are removed (202.2 days of dead time introduced) 4. FV + (negative gatti) cuts applied Events with E > 3 MeV: 246 Total expected background (resid. rad. + ext. γ+ 8B neut.): 186 ± 60.5events 1 4 2 3 15th Lomonosov Conference on Elementary Particle Physics

  19. mA , eV Limits on gAe× gAN vs mA and gAe vs mA 1– Borexino limits on gAe (KSVZ) 2– Borexino limits on gAe× gAN 3 – Reactor experiments and 64Cu source 4 – beam-dump experiments 5 – ortopositronium decay 6 – CoGeNT coll. 7 – CDMS coll. 8 – Solar axion luminosity 9 – Resonant absorption by 169Tm nuclei 10 – Red giant 11– Axioelectric effect in BGO The Borexino resultsexclude large regions of axion masses (0.01-1) MeV and coupling constants gAe~(10-11-10-9) for hadronic axion with mA=1 MeV, gAe<2×10-11. Figure also shows the constraints on gAe that were obtained in the experiments with reactor, accelerator and solar axions as well from astrophysical arguments. 15th Lomonosov Conference on Elementary Particle Physics

  20. 11 gAγ, G eV-1 Limits on gAγvs mA for gAN3=2.8x10-8 mA (KSVZ) 1a – Borexino A→2γdecay 1b – Borexino Primakoff Conv. 2 – CTF results 3 – Reactor experiments 4 – beam-dump experiments 5 – Resonant absorption 6 – Cosme, Solax, DAMA 7, 11 – CAST 8 – Telescopes 9 – HB stars 10 – SUSY and mirror axions allowed region The Borexino resultsexclude large regions of axion masses 10 keV-5 MeV and coupling constants gAγ (2×10-14-10-7) GeV-1. For higher values g2m3 axions decay before reaching the detector, for lower one the probability of axion decay inside Borexino is too low. Borexino limits are more then 2-4 orders magnitude strongerthan obtained by laboratory-based experiments using nuclear reactors. New region available for heavy axions is partially excluded. 15th Lomonosov Conference on Elementary Particle Physics

  21. Perugia Genova Milano Dubna JINR (Russia) Princeton University Kurchatov Institute (Russia) Virginia Tech. University APC Paris Jagiellonian U. Cracow (Poland) BorexinoCollaboration Heidelberg (Germany) Munich (Germany) (Russia) 15th Lomonosov Conference on Elementary Particle Physics

  22. Complementary slides 15th Lomonosov Conference on Elementary Particle Physics

  23. The Pauli Exclusion Principle (PEP). "There can never be two or more equivalent electrons in the atom. These are defined to be electrons for which ... the values of all quantum numbers ... are the same." W. Pauli, 1925 QM:wave function of the system of electrons must be antisymmetric under exchange and permutation of electrons (P.A.M.Dirac, 1930) QFT: field describing the fermions obey anticommutation relations for creation/annihilation operators 1930-1980: E. Fermi – discussion of “weakly” non-identical electrons (1934) H.S. Green – parastatistics: i.e. "100% violating" theory (1953) V.L. Luboshits, M.L. Podgoretskii – the model with the electron as a superposition of nearly degenerated states with defined mass (1971) R.D.Amado, H. Primakoff – pointed out that in the framework of QM PEP-violating transitions are forbidden even if PEP-violation takes place (1980) 1987-1991: A.Yu.Ignatiev, V.A.Kuzmin – the first model with the small parameter characterizing the degree of violation: introduction of 3X3 matrices for the fermions creation/annihilation operators L.B.Okun, О.W.Greenberg, R.N.Mohapatra (1987-91)– attempts to generalize Ignatiev-Kuzmin theory for the case of indefinite number of levels (field). It was found byA.B. Govorkov (1989) that even a small PEP violation in those theories leads to negative probabilities for someprocesses => "... it is hardly possible to build a free field theory with the small violation of Fermi or Bose statistics.We don't thinkthat interactions would change the situation." O.W. Greenberg, R.N. Mohapatra, Preprint University of Maryland, UM PP No. 89-030 (1999) A.D. Dolgov, A.Yu.Smirnov (2005) – discussion of cosmological sequences of the PEP-violation 15th Lomonosov Conference on Elementary Particle Physics

  24. The main experiments “...In the fundamental physics, if anything could be checked - itmust be checked.“ L.B. Okun SEARCH FOR ATOMS IN ANOMALOUS STATES: 1989-91 Novikov et al., Nolte et al. search for non-Paulian (NP) exotic Ne and Aratoms inF and Cl samples with the mass-spectroscopy technique 1990 Ramberg, Snow search for X-ray emission from the conductor (Cu) with current (to be improved byVIPCollaboration) 1995 Deilamian et al., 1996 Hilborn et al., M. de Angelis et al. search for Pauli-forbidden spectral lines in4He and 16О atoms withthe molecular and laser spectroscopy technique 1998 Barabash et al. search for anomalous С atoms in B samples (γ-activationanalysis) 2000 Javorsek et al. search forBeatoms with 4 electrons in 1s-state (looks like He) SEARCH FOR PAULI-FORBIDDEN TRANSITIONS IN ATOMS AND NUCLEI: 1948 Goldhaber, Scharff-Goldhaber search for X-ray emission from the β-particlescapture in Pb 1974 Reines, Sobel search for X-ray emission from transitions of electrons from L-shell to the filled K-shell 1979 Logan, Ljubicic search forγ-quanta emitted in a Pouli- forbidden transitions of nucleons in nuclei NP transitions withγ emmision: Kamiokande, NEMO-II NP transitions with protons emission : Elegant-V, DAMA/LIBRA NP transitions with neutrons emission: Koshomoto et al. Non-Paulian β+andβ-decays: LSD, NEMO-II, Kekez et al. Counting Test Facility (CTF) 15th Lomonosov Conference on Elementary Particle Physics

  25. Energy released in the NP transitions ENERGY RELEASE (Q) is the difference between the binding energies Ebof the final and initial nuclei. Defining a non-Paulian nucleus as XNP, Y = γ, p, n, d, α… : Q(12C→XNP+Y) = M(12C) - M(XNP) - M(Y) = Eb(XNP) + Eb(Y) - Eb(12C) The binding energy of non-Paulian nucleus Eb(XNPp,n) with 3 protons or 3 neutrons on the S-shell can be evaluated considering the binding energy of normal nucleusEb(X) and the difference between the binding energy of nucleons on S-shell Ep,n(1S1/2) and the separation energy Sp,n(X): Eb(XNPp,n)  Eb(X) + Ep,n(1S1/2) - Sp,n(X) The binding energies Eb(X)of the nuclei and the nucleons separation energiesSp,n(X)are well known. The binding energies of nucleons on the shellsEp,n(1S1/2) are not so precise. The nucleon binding energies of P- and S-shells for the light nuclei were measured while studying (p,2p) and (p,np) 1 GeV proton scattering reactions. Belostotskii et al., Sov. J. of Nucl. Phys. 41, 903 (1085) 15th Lomonosov Conference on Elementary Particle Physics

  26. Calibrations: measurements with 241Am9Be source 15th Lomonosov Conference on Elementary Particle Physics

  27. High-energy events spectra, 485 days live time 1. Raw events spectrum 2. 2ms cut after each muon applied 3. Events within time interval 0.7s after muons crossing SSS are removed (16 days of dead time introduced) 9Li (178 ms), 8He (119 ms) There are no events above 12.5 MeV 15th Lomonosov Conference on Elementary Particle Physics

  28. τ(12C →12CNP+γ) ≥ 5.0.1031 y The limit on the probability of transitions 12C→12CNP+ is based on the experimental fact of observing no events with energy higher than 12.5 MeV passing muon veto cut. We obtain the lower limit on PEP violating transitions of nucleons from P-shell to the occupied 1S1/2-shell according to: E≈ 0.50 is the efficiency of registering an event in the energy interval E; N12C = 2.37.1031 (533 t) is the number of 12C nuclei under consideration; Np+n = 8 is the number of nucleons for which the non-Paulian transitions are possible; T = 468 days is the time of measurements (live time); Slim = 2.44 is the upper limit on the number of candidate events at 90% c.l. G.L. Feldman, R.D.Cousins, PRD57, 3873 (1998) The Borexino limit is 4 orders of magnitude stronger than the CTF one because of the large mass, time of measurement and efficiency of registration. 15th Lomonosov Conference on Elementary Particle Physics

  29. τ(12C→12NNP+e-+)≥ 3.1.1030 y, τ(12C→12BNP+e++) ≥ 2.1.1030 y The limits on the probabilities of NP β±- transitions are based on the fact of observing no events with energy higher than 12.5 MeV passing muon veto cut. The number of e± emitted with E>12.5 MeV are E≈0.21 and E ≈ 0.16 for transitions 12C→12NNP + e- +  and 12C→12BNP + e+ + , correspondently. The lower limits were obtained as: τ(12C →12NNP + e- + ) ≥ 3.1.1030 y (90% CL) τ(12C →12BNP + e+ + ) ≥ 2.1.1030 y (90% CL) 15th Lomonosov Conference on Elementary Particle Physics

  30. Energy spectrum in the 0.5-8.0 MeV range 1. Spectrum after 0.7s cut + FV 2. Pairs of correlated events (with time interval Δt ≤ 2 ms between signals) are removed 3. Events with positive Gatti variable only are left In the inset the values of Gatti var obtained with AmBe source for protons and 2.2 γ-s are shown 15th Lomonosov Conference on Elementary Particle Physics

  31. τ(12C→11BNP + p) ≥ 2.1.1030 y • Peak position: 4.6-8.3 MeV (90% CL), corresponds to 1.8-4.1 MeV in e- energy scale •Spectrum fit after FV cut: the measured spectrum within FV is fitted by polynomial (bg) + gauss (sig) function; except the region of 2.614 MeV γ-peak from 208Tl, we obtain Slim = 52 (at 90% CL), that for 100t FV mass (NN = 4.45.1030) results in τ(12C→11BNP + p) ≥ 8.9.1029 y •Selective proton-like spectrum fit: additional cut requiring positive Gatti variable has been applied; efficiency of that cut is found to be ε= 0.89 according to the measurements with AmBe source. For the same fitting procedure the lower limit on lifetime is: τ(12C→11BNP + p) ≥ 2.1.1030 y (90% CL) 15th Lomonosov Conference on Elementary Particle Physics

  32. τ(12C→11CNP + n) ≥ 3.4.1030 y • Initial energy:3.2-7.3 MeV (90% CL), mean lifetime is τ ≈ 250 µs; capture on protons (0.33 barns, Eγ= 2.2 MeV) and 12C (3.5 mbarns, Eγ= 4.95 MeV) •Fit of the 2.2 MeV γ-peak: the position and width (90 keV) of the peak are well- known, fit with Gaussian gives Slim = 57: τ(12C→11CNP + n) ≥ 8.1.1029 y •Selection of two correlated events: Ep ≥ 0.5 MeV, 1.0 MeV ≤ Ed≤ 2.4 MeV; 20 µs ≤Δt ≤ 1.25 ms, Δr ≤ 2 m; rp ≤ 4.75 m, rd ≤ 4.75 m; 0.7 s after-muon cut applied for prompt events. 52 events in total was found, 33 events are within the possible energy interval: τ(12C→11CNP + n) ≥ 3.4.1030 y (90% CL) 15th Lomonosov Conference on Elementary Particle Physics

  33. Conclusions Using the unique features of the Borexino - the extremely low background, large scintillator mass and low energy threshold - new limits on the forbidden transitions of nucleons from the P-shell to the 1S1/2-shell in 12C with the emission of γ, n, p, and β± particles have been obtained: τ(12C→12CNP+γ) > 5.0.1031 y, τ(12C→11BNP+p) > 8.9.1029 y, τ(12C→11CNP+n) > 3.4.1030 y, τ(12C→12NNP+e-+ν ) > 3.1.1030 y, τ(12C→12BNP+e++ν ) > 2.1.1030 y, allwith 90% C.L. These limits on NP transitions in 12C with γ-, p-, n- and β± -emissions are the best to date. 15th Lomonosov Conference on Elementary Particle Physics

  34. Count rate of axions due to the Compton conversion • The number of expected events in the detector containing N electrons (or 12C nuclei) obtained during time of measurement T due to the Axion-Compton process is: where η – detector’s efficiency, ΦA – axion flux reaching the detector, and me– electron’s mass. Only gAe and mA remains in the right part of S. 15th Lomonosov Conference on Elementary Particle Physics 34

  35. Count rate of axions due to the axions’ decay • The axion flux coming from the Sun: where Φνpp – neutrino flux from pp reaction on the Sun, ωA/ωγ– ratio of the probability of a nuclear transition with axion production (ωA) to the probability of a magnetic transition (ω) • The axion flux reaching the detector where τc.m. – axions’ lifetime and τf – time of flight in c.m.s. • The number of expected A → γγ decays in the detector of volume V is where where η – detector’s efficiency and βc.m.= pA/EA.Only gAγ and mA contribute to the right part of S. 15th Lomonosov Conference on Elementary Particle Physics 35

  36. Interaction of axions with solar matter (gAe) Compton conversion A + e → γ + e pp reaction occurs within ~0.11 of the Sun radius. Axion pass through layer of 6.8•1035 electrons/cm-2 The Compton conversion crossection σCC  g2Ae•5.5•10-25 restricts the sensitivity of solar axion experimetnts by values gAe ≤ 10-6 . In this case axion flux would not be suppressed more then 10%. Axioelectric effect A + e + Z → e + Z σAE ~ Z5(EA)-3/2, the abundance of Fe atoms constrains gAe < 1.1×10−4, in this case 90% of axions escape from the Sun. Because of the low abundance of heavy elements (with Z ≥ 50) in the Sun (~ 1 ppb atom/atom), the probability of axio-electric absorption by heavy atoms is less then by Fe atoms. The axioelectric cross-section is more than 4 orders of magnitude lower than for Compton process, so the axioelec. effect can not be taken into account. 15th Lomonosov Conference on Elementary Particle Physics 36

  37. Interaction of axions with solar matter (gAγ) Axion decay A → 2γ The relation τf ≤ 0.1τcm restricts the region of values of gA and mA that are available for the study in solar experiments: g2Am4A < 6.4πpA(c/L) Primakoff conversion A + Z → γ + Z σPC ≤ g2Aγ•Z2•2•10-29 cm-2, so for protonsthe condition g2Aγ≤ 10-4 GeV-1 provides escape of axions from the Sun (4) (3) (1) (2) Axion decays (1) and Primakoff conversions (2)for KSVZ model (3) and (4) – the same but in assumption that axion does not decay on it’s flight from the S. 15th Lomonosov Conference on Elementary Particle Physics 37

  38. Fit results: Compton conv. A (5.5 MeV) + е– → е– + γ Best fit:Χ2/ndf = 1.25 a = 3.7 ± 0.4, b = (-2.3 ± 2.2)x10-03 S = 0.55 ±8.1 Slim (90 C.L.) = 6.9 events 15th Lomonosov Conference on Elementary Particle Physics

  39. Conclusions The search for 5.5 MeV solar axions emitted in the p(d, 3He)A reaction has been performed. The Compton conversion of axion to a photon, decay axion in two photons and inverse Primakoff conversion on nuclei were searched for. No statistical significant indications on axion interactions were found. The new, model independent upper limits on constants of interaction of axion with electrons, photons and nucleons gAe× gAN≤ 6.5×10-13 and gAγ× gAN≤ 4.6×10-11 GeV-1 were obtained at mA ≤ 1 MeV (90% c.l.). Under the assumption that gAN depends on mA as for KSVZ axion model the limits on axion-electron and axion-photon couplings vs axion mass were obtained |gAe× mA|≤ 2.0×10-5 and |gAγ× mA|≤ 1.7×10-3, where mA and gA are given in eV and GeV-1, respectively (90% c.l.). 15th Lomonosov Conference on Elementary Particle Physics

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