V.S.Imshennik, O.G.Ryazhskaya

1. V.S.Imshennik, O.G.Ryazhskaya A Rotating Collapsar And Possible Interpretation Of The LSD Neutrino Signal From SN 1987A

2. The work deals with a possible explanation of the results, obtained by underground detectors during Supernova SN1987A explosion. The name "SN" came from the observational astronomy data and deals with an instant appearance of a very bright star, with luminosity of about tens millions of the solar one.

3. Indeed, this is not the birth of a new star, but the destruction of the star, exhausted its nuclear fuel. During the lifetime of the star (its evolution) nuclear forces as well as gravitational, rotating and magnetic field forces act on it. The simplest case:the star is spherically symmetric, non-rotating, non-magnetic.

4. Stable state: The forces of hot gas pressure compensate the gravitational ones. The temperature of the hot gas is supported by the nuclear radiation.Fn=Fg H D He C O Fe Fn Fg In the beginning of its evolution the star consists mainly of hydrogen. During the time due to the nuclear synthesis reaction the energy which keeps the star in equilibrium is released. After the production of Fe nuclei, the further evolution requires the energy consumption. The forming of Fe nuclei takes place in the coreFn<Fg. The star starts to compress, to collapse. Fe - nuclei are destroyed, electrons are practically pressed in the atomic nuclei under the action of gravitational forces. The electron neutrinos are emitted. 10 % energy of state Total energy

5. ~60 years ago the problem looked like the science fiction mixed with a some joke. On April 1st, 1941Phys. Rev. has published «Neutrino Theory of Stellar Collapse»by G.Gamov and M.Schoenberg «The processes of absorption and reemission of free electrons by atomic nuclei which are abundant in stellar matter may lead to such tremendous energy losses through the neutrino emission that the collapse of the entire stellar body with an almost free-fall velocity becomes quite possible»

6. URCA-process The idea was born in Rio casino “Urca” where it was possible to lose a lot of money very quickly. «We have developed the general views regarding the role of neutrino emission in the vast stellar catastrophesknown to astronomy, while the neutrinos are still considered as highly hypothetical particles because of the failure of all efforts made to detect them». G.Gamov, M.Schoenberg

7. 1957 F. Reines and C. Cowan detect antineutrinos from reactor. 1959 An active discussion of the role of neutrinos in astrophysics starts. B. Pontecorvo states, that e-scattering may lead to macroscopic effects. 1965Ya.B. Zel’dovich and O.H.Guseinov show, that gravitational collapse is accompanied by powerful and short (~10 ms) pulse of neutrino radiation. 1965The first proposal to search for collapsing starts (c.s.) using neutrino detectors by G.V.Domogatsky and G.T. Zatsepin 1965The birth of an experimental neutrino astrophysics. 1964-1966 W. Fowler, F. Hoyle investigate the role of neutrinos in the last stages of stellar evolution. The dissociation of iron core plays an important role in stability loss by massive stellar envelopes.

8. 1966The first calculation of collapse dynamics by S. Colgate, R.White 1966-1967 The process of an implosion for stars with 32; 8; 4; or 2 solar masseshas been studied.The parameters of neutrino radiation are obtained (W. Arnett). 1967-1978The structure ofneutrino burst , energy spectra was studied by V.S.Imshennik, L.I.Ivanova, D.K.Nadyozhin, I.V.Otroshenko (Model I) in the first time . Also it was shown that the main flux of the neutrinos is emitted during the cooling stage of a new born neutron star. The duration of neutrino pulse was shown to be ~ 10 s. 1980-1982The time structure and energy spectra of for the initial stage of collapse (<0.1 ms) are obtained by R.Bowers, J.Wilson (Model II). 1987 S. Bruenn’s calculations

9. Neutrino detection from a collapsing star makes it possible: • -       To detect gravitational collapse even it is “silent” (isn’t accompanied by Supernova explosion); • -       To investigate the dynamics of collapse; • -       To estimate the temperature in the star center. If the star is nonmagnetic, nonrotating, spherically symmetrical the parameters of neutrino burst arethe following (Standard model): From the theory of the Standard collapse it follows that the total energy,carried out by all types of neutrinos,corresponds to ~ 0.1 of star core mass and is divided among these 6 components in equal parts.

10. General idea How can one detect the neutrino flux from collapsing stars? Until now, Cherenkov (H2O)andscintillation (СnH2n) detectors which are capable of detecting mainly , have been used in searching for neutrino radiation, This choice is natural and connected with large -p cross-section As was shown at the first time by G.T.Zatsepin, O.G.Ryazhskaya, A.E.Chudakov (1973), the proton can be used for a neutron capture with the following production of deuterium (d) with  - quantum emission with 180 – 200 µs. The specific signature of event

11. А t T How can the neutrino burst be identified ? The detection of the burst of N impulses in short time interval T

12. The possibility to observe the neutrino burst depends on background conditions The source of background: • Cosmic rays 0<E< • а) muons • б) secondary particles generated by muons(e,,nand long-living isotopes) • с) the products of reactions of nuclear and electromagnetic interactions • 2. Natural radioactivity Е<30 MeV, mainly Е<2.65 MeV • а) , • b) n,(n ), U238, Th232 • c) , (n) d) Rn222 Background reduction: 1. Deep underground location 2. Using the low radioactivity materials 3. Anti-coincidence system 4. Using the reactions with good signature 5. The coincidence of signals in several detectors

13. 5 supernovae were observedin Our Galaxy: 1604 (Kepler) 1572 (Ticho Brage) 1181 1054 (Crab Nebula) 1006 Theoreticians Experimentalists Develop new models of collapse Develop registration methods The theory predicts the possibility of gravitational collapse without envelope drop (without supernova appearance) once per 10 yrs. Due to these events are very rear the detectors should operate with a maximum time and should be multipurpose ones (underground observatories).

14. 1977Arteomovsk Scintillation Detector(INR RAS) has scintillator mass of 105 t, good signature of events (the possibility to detect both particles in the reaction) MeV 1978 Baksan Underground Scintillation Telescope(INR RAS) with a total massof 330 t 1984LSD– (Liquid Scintillation Detector, USSR – Italy), scintillator mass - 90 t, good signature of events (the possibility to detect both particles in the reaction :)

15. Arteomovsk BST Soudan Kamioka GranSasso Homestake Mt Blanc Sudbury KGF The muon depth-intensity curve (underground data): curves are calculated by Bugaev et al., 1998

16. The large volume detectors are the underground observatories for: • Neutrino astrophysics • Cosmic Rays physics • Search for point sources of cosmic rays • Study of neutrino oscillations • Search for rare events predicted by the theory (proton decay, monopoles, dark matter...) • - Geophysical phenomena

17. It is possible to study cosmic rays underground using their penetrating component P,, A ? Neutrinos from collapsing stars Solar neutrinos Neutrinos from point sources hadronic shower em. showers Hadronic shower Muon beams

18. February 23, 1987 2 h 52 min.

20. Events, detected by LSD February,23, 1987 г. (SN 1987 A)

21. On February,23, 1987 A Supernova explosion in the Large Magellanic Cloud occured.

22. 1987А +4 +6 +8 +10 +12 Jones Shelton mv McNaught Jones Discovery Mont Blanc Kamioka, IMB, Baksan Radio (21cм) Sk – 69o202 S W (У В) ? Shelton UT 0h 2h52m 7h36m 9h22m 15h54m Feb24 Feb25

24. LSD Kamiokande IMB Baksan

25. February 23, 1987 1 3 5 7 9 11 mv=12m mv=6m Geograv 2:52:35,4 2:52:36,8 7:36:00 LSD 5 2 43,8 19 2:52:34 KII 2 7:35:35 12 (4) 44 47 7:35:41 IMB 8 47 7:36:06 BUST 2:52:34 1 6 21

26. The detector responses to the standard stellar collapse in the Large Magellanic Cloud if The total energy of neutrino radiation from SN1987A is more than an order of magnitude higher than the binding energy of neutron star with a baryon mass of about 2М

27. The possible solution is : A rotating collapsar The short review of the rotational mechanism: On the threshold of gravitational collapse theFе-O-C stellar core Mt – total mass, I0 – total angular momentum are conserved during the collapse of the core into a rotating collapsar

28. The collapsar with the high probability falls into the region of the dynamical instability. The criterion: Total gravitational energy Total rotational energy During the collapse increases greatlycompared to , which is also an increasing quantity This instability grows with the characteristic hydrodynamic time and leads to the breakup of the collapsar into pieces.

29. A rotating collapsar The Two-Stage Gravitational Collapse Model[Imshennik V.S., Space Sci Rev, 74, 325-334 (1995)] aside above

30. The rotation effects make it possible: 1. To resolve the problem of the transformation of collapse into an explosion for high-mass and collapsing supernovae (all types of SN, except the type Ia – thermonuclear SN) 2. To resolve the problem of two neutrino signals from SN 1987A, separated by a time interval of 4.7 h.

31. The difference of neutrino emission in the standard model and in the model of rotating collapsar. Tc~5x1012K Tc~5x1010K The main reaction – URCA-process:

33. Let us consider how the various detectors operated during the explosion of SN1987A could record the neutrino signals in terms of the model of a rotating collapsar, which reduces to the following: 1. Two neutrino bursts separated by a time tgrav~5 h must exist. 2. The neutrino flux during the first burst consists of electron neutrino with a total energyof 8.9х1052erg: the neutrino energy spectrum is hard and asymmetric with mean energies in the range of 25-50 MeV; the duration of the neutrino radiation is t ~ 2.4 - 6 s. 3. The second neutrino burst corresponds to the theory of standard collapse.

34. Fe (2 cm) 6 m 4.5 m 8m Fe (10 cm) Liquid Scintillator Detector (LSD) H=5200 m.w.e. 72 counters 90 tons ofСnH2n (n~9), 200 tons ofFe General view of LSD

35. PM FEU - 49B ( 15 cм) 100 100 150 cм

36. Bugaev E.V., Bisnovaty-Kogan G.S. et al., 1979 The comparison of the total reduced cross-sections with νn cross-section on a free neutron for the reaction

37. Yu.V. Gaponov, S.V. Semenov 1+ GT __________10,589 1+ GT __________ 7,589 1+ GT __________ 4,589 0+ IAS __________ 3,589 1+ __________ 1,72 4+ __________ 0+ F GT GT GT

38. e e e СnH2n СnH2n СnH2n

39. Events 106 105 104 103 102 10 1 Energy range, detected by LSD Energy spectrum of the particles, coming from 2,8 cmiron plate (Geant4 calculations; histogram – total energy deposit) 0 5 10 15 20 25 30 35 40 Energy, MeV

40. * De Rujula, 1987** Alexeyev, 1987

41. Baikal NEUTRINO DETECTORS Arteomovsk SNO LSD Baksan SOUD KamLAND SK LVD IMB KGF AMANDA AMANDA

42. LVD SNO SUPER K SuperK LVD KamLand

44. Radon peaks distribution vs time (November – March, 1997) The counting rate of the LVD during the earthquake in Italy, 1997. Arrows mark the moments of seismic shocks.

45. Neutrons generated by muons underground Number of Events 0 200 400 600 μs

46. Reactions for scintillation and Cherenkov counters MeV cm2 MeV cm2 cm2 cm2

47. The simplest case Double neutron star (NS) Almost all of the angular momentum can turn into an orbital angular momentum, Jоrb≤Jo, J= Jo-Jоrbbecomes the spin angular momentum of the NS themselves especially in the more massive component of this binary. The NS binary is formed through the hydrodynamic fragmentation of a rotating collapsar.

48. e – spectra of volume radiation for B-nucleonic gas + FD-electronic gas The only reaction of URCA-processes: Neutrino radiation luminosity per gramm (Ivanova et al, 1969; Imshennik, Nadyozhin, 1971, 1972)

49. 1. Central parameter of rotating collapsar (t ~ 2.5 sec) 2. Total energy of neutrino radiation (t ~ 6 sec) (Imshennik, Nadyozhin, 1977, 1992):

50. The signal detected by LSD is the first detection of a neutrino burst from the collapse of SN 1987A ?