V.S.Imshennik, O.G.Ryazhskaya

A Rotating Collapsar

And

Possible Interpretation

Of The LSD Neutrino Signal

From SN 1987A

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.

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.

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

In the beginning of its evolution the star consists mainly of hydrogen. During the time due to the nuclear synthesis reaction

Fn

Fg

The forming of Fe nuclei takes place in the core Fn<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.

Total energy 2%10 cM star 10 % energy of state

the energy which keeps the star in equilibrium is released. After the production of Fe nuclei, the further evolution requires the energy consumption.

~60 years ago the problem looked like the science fiction mixed with a some joke.

On April 1st, 1941 Phys. 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»

~

1

1

eNN

NeNA

ZA

Z

AZ

AZ 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 catastrophes known 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

e

e

epn

nep

~

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.

1965 Ya.B. Zel’dovich and O.H.Guseinov show, that gravitational collapse is accompanied by powerful and short (~10 ms) pulse of neutrino radiation.

1965 The first proposal to search for collapsing starts (c.s.) using neutrino detectors by G.V.Domogatsky and G.T. Zatsepin

1965 The 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.

1966 The 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 masses has been studied. The parameters of neutrino radiation are obtained (W. Arnett).

1967-1978 The structure of neutrino 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.

1980-1982 The 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

ee ~and

,,,~ee

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 are the following (Standard model):

ModelModel

Total Total energy,energy,

Total Total energy of energy of

Total Total energy of energy of

Duration, Duration, ss

Model IModel I

3-143-14 0.5-2.30.5-2.3 0.10.1

12.612.6 10.510.5 -- ~~2020

Model IIModel II

1010 88 2525 55

erge5310,~ erge

5310,MeVE

e,~ MeVE

e,

MeV

Е e )(

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.

~,,~,,~, ee

erg5310

Until now, Cherenkov (H2O) and scintillation (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.

2.2n p d E МэВ

2 44 2~ 9.3 10e p e

E см

e~

e~

nepе ~

General idea

How can one detect the neutrino flux from collapsing stars?

The specific signature of event

MeVE 2.2

MeVEe

5.0

How can the neutrino burst be identified ?

T

The detection of the burst of N impulses in short time interval T

i Ethr

iiiMdEEEI

RN )()(

4

1~

2

А

t

The possibility to observe the neutrino burst depends on background conditions

1. Cosmic rays 0<E< а) muons б) secondary particles generated by muons (e,,n and long-

living isotopes) с) the products of reactions of nuclear and electromagnetic

interactions2. Natural radioactivity Е<30 MeV, mainly Е<2.65 MeV а) , b) n, (n ), U238, Th232 c) , (n) d) Rn222

1. Deep underground location2. Using the low radioactivity materials 3. Anti-coincidence system4. Using the reactions with good signature5. The coincidence of signals in several detectors

The source of background:

Background reduction:

Develop new models of collapse

Experimentalists

The theory predicts the possibility of gravitational collapse without envelope drop (without supernova appearance) once per 10 yrs.

5 supernovae were observed in Our Galaxy:

1604 (Kepler) 1572 (Ticho Brage)11811054 (Crab Nebula)1006

Theoreticians

Develop registration methods

Due to these events are very rear the detectors should operate with a maximum time and should be multipurpose ones (underground observatories).

1977 Arteomovsk Scintillation Detector (INR RAS) has scintillator mass of 105 t, good signature of events (the possibility to detect both particles in the reaction)

1978 Baksan Underground Scintillation Telescope (INR RAS) with a total mass of 330 t

1984 LSD – (Liquid Scintillation Detector, USSR – Italy), scintillator mass - 90 t, good signature of events (the possibility to detect both particles in the reaction : )

*dpn

nep

МэВEd 2.2

nep~

MeV

ArteomovskBST

Soudan

KamiokaGran Sasso

HomestakeMt Blanc

Sudbury

KGF

The muon depth-intensity curve (underground data): curves are calculated by Bugaev et al., 1998

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

Neutrinos from collapsing stars

)~(

)~(

)~(

ee

P,, A

0 0, , ,,

K Kp n

eEAS

Muon beams

, ,( )

. .эл мeливни

( )

Hadronic shower

0, ,,

адронныйКливеньp n

,( ),

?

Neutrinos from point sources

em. shower

s

Solar neutrinos

hadronic shower

It is possible to study cosmic rays underground using their penetrating component

February 23, 19872 h 52 min.

# of# of eventevent

TimeTime, , UTUT±2ms±2ms

Energy,Energy,MeVMeV

11

22

33

44

55

2:52:36,792:52:36,79

40,6540,65

41,0141,01

42,7042,70

43,8043,80

6,2 – 76,2 – 7

5,8 – 85,8 – 8

7,87,8 –11–11

7,0 – 77,0 – 7

6,8 – 96,8 – 9

11

22

7:36:00,547:36:00,54

7:36:18,887:36:18,88

88

99

Events, detected by LSD

February,23, 1987 г. (SN 1987 A)

On February,23, 1987 A Supernova explosionin the Large Magellanic Cloud

occured.

+4

+6

+8

+10

+12

0h 2h52m 7h36m 9h22m 15h54m

Sk – 69o202

McNaught

Radio (21cм)

?

Shelton Jones

DiscoveryJones

Mont Blanc

Kamioka,IMB,

Baksan S W(У В)

1987А

mv

UTFeb24 Feb25

Shelton

DetectorDepth,

meters of water

equivalent

Fiducial volume,

tons

Material Energy

threshold, MeV

Detection

efficiency Background rate

s-1е+ spectrum

of reactionе- spectrum of reaction

BUST

USSR 850130

(200)

160

CnH2n

Fe

10 0.6 0.15

(0.54)

0.013

(0.033)

LSD

USSR –

Italy

520090

200

CnH2n

Fe

5-7 0.9 0.4(0.7) 0.01

KII

Japan –

USA

27002140 H2O 7-14 0.7 0.17

(0.54)

0.022

IMB

USA 15705000 H2O 20-50 0.1 0.02

(0.18)

3.5x10-6

nepe~ ee ii

Kamiokande

BaksanIMB

LSD

February 23, 1987

Optical

Geograv

LSD

KII

IMB

BUST

1 3 5 7

2:52:35,4

2:52:34

2:52:34

7:36:00

7:35:35

7:35:41

7:36:06

44

43,8 19

47

:47

21

5

2(4)

1 6

2

12

8

v m =6vm =12 m

observations

2:52:36,8

m

9 11

February 23, 1987

1 3 5 7 9 11

mv=6mmv=12m

Geograv

LSD

KII

IMB

BUST

2:52:35,42:52:36,8

43,82:52:3

444

2:52:34

7:36:00

7:35:35

7:35:41

7:36:06

19474721

2

12

8

6

5

2

1

(4)

The detector responses to the standard stellar collapse in the Large Magellanic Cloud

DetectorDetector

LSDLSD

BUSTBUST

KIIKII

IMBIMB

1.51.5

22

1717

66

0.0430.043

0.0520.052

0.530.53

0.40.4

0.0240.024

0.0360.036

0.360.36

0.350.35

)1(eK )2()2( baK

e )2( bK

e

)(1

~)(~

2

211

~2

kT

ЕеMeVsФ

MeVkT 2~

LSDLSD BUSTBUST KIIKII IMBIMB

1.71.7

2.12.1

0.10.1

0.10.1

2.12.1±1.0±1.0

1.8±0.81.8±0.8

55

55

0.20.2

0.50.5

55±2.5±2.5

12±612±6

00

00

MeVkT ,эрг

We

,1054~ ik

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 ergWE

etot55

~ 10)21(6

if

The short review of the rotational mechanism:

On the threshold of gravitational collapse the Fе-O-C stellar core

Mt – total mass, I0 – total angular momentum

are conserved during the collapse of the core

into a rotating collapsar

The possible solution is : A rotating collapsar

The collapsar with the high probability falls into the region of the dynamical instability.

The criterion:27.0

grav

rot

Total rotational energyTotal gravitational energy

During the collapse increases greatly compared to , which is also an increasing quantity

rot grav

This instability grows with the characteristic hydrodynamic time and leads to the breakup of the collapsar into pieces.

The Two-Stage Gravitational Collapse Model[Imshennik V.S., Space Sci Rev, 74, 325-334 (1995)]

12 MM

222 , JM

12 111, JM

A rotating collapsar

~,

e

above

aside

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.

Tc~5x1012

KTc~5x1010

K

The difference of neutrino emission in the standard model and in the model of rotating

collapsar.

MeVE

MeVE

MeVE

e

e

)2520(

10

12

~,,~,

~

The main reaction – URCA-process:

MeVE

nep e

)5030(

e e

e~

~

~

e

e

e

e

e

314106.2~ cmg

erg53~, 103.5 erg

eee

52~, 109.8

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 energy of 8.9х1052 erg: 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.

Liquid Scintillator Detector (LSD)

General view of LSD

Fe (2 cm)

Fe (10 cm)

H=5200 m.w.e. 72 counters 90 tons of СnH2n (n~9), 200 tons of Fe

4.5 m

8m

6 m

150 cм

100

100

PM FEU - 49B ( 15 cм)

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

*)1,(),( ZAeZAe

eCoFee56

27

56

26

1+ GT __________10,589 1+ GT __________ 7,589 1+ GT __________ 4,589 0+ IAS __________ 3,589 1+ __________ 1,72 4+ __________ Co

56

27

MeVFeECoE 056.456

26

56

27

MeVE 40

MeVeKE 84.30, MeVE 1MeVE 82.1 MeVE

n72.1

2401027.1 cm

2401005.1 cm

2411041.6 cm

2401027.1 cm

F

GT

GT

GT

0+

24024.4 cmEtot

n

eK

MeVEMeVE

MeVE

72.182.1

84.31,

E

n

eK

MeVEMeVE

MeVEMeVE

72.182.1

484.27,

Yu.V. Gaponov, S.V. Semenov

n

eK

MeVEMeVE

MeVEMeVE

72.182.1

784.24,

СnH2n

CoeFe e5656

СnH2n

CoeFe e5656

СnH2n

CoeFe e5656

MeVE 72.1

EEE oe

MeVE 82.1 MeVE 72.1

MeVE 4

MeVE 82.1

MeVE 7

e

MeVE 82.1EEE oe EEE oe

e

e

Energy spectrum of the particles, coming from 2,8 cm iron plate (Geant4 calculations; histogram – total energy deposit)

0 5 10 15 20 25 30 35 40Energy, MeV

106

105

104

103

102

10

1

Events

Energy range, detected by LSD

DetectorDetector EnergyEnergy

thresholdthreshold

Estimated number ofEstimated number of

eeAA interaction interaction

EstimatedEstimated

EffectEffect Exp.Exp.

NN11 NN22 NN33 NN44

LSDLSD 5 – 75 – 7 3.23.2 5.75.7 3.53.5 4.94.9 3.23.2 55

KIIKII 7 – 147 – 14 0.90.9 3.13.1 1.21.2 2.52.5 2.72.7 22**

BUSTBUST 1010 2.82.8 5.25.2 ~1~1 11****

2N

130 (N )e

E MeV 240 (N )e

E MeV

35 (N )e

f E with

47.5 (N )e

f E with e

kT

5.34ckT MeV

14 32.6 10 /g cm

* De Rujula, 1987 ** Alexeyev, 1987

AMANDA

Baikal

LVD

KGF

KamLANDSK

IMB

SNO

SOUD

ArteomovskLSD

Baksan

AMANDA

NEUTRINO DETECTORS

SUPER K

LVD SuperK

LVD

KamLand

SNO

DetectorDepthm.w.e

Mass,ktons

Thre-shold,MeV

EfficiencyNumber of

events Back-ground

s-1

ArteomovskASD

Russia570

0.1CnH2n

5 0.97 0.8 0.85 57 2.1 9.5 0.16

BaksanBUST

Russia

850 0.13(0.2)CnH2n

10 0.6 - 0.2 45(67)

1.4(2.2)

2.8(4.3)

0.013(0.033)

KamLAND USAJapan

27001.

CnH2n~ 4

-500 22

30054

Gran SassoLVD

Italy,Russia

3300

0.95Fe1.1

CnH2n

4 – 6 0.9 0.6 0.5-

550

470

24

300

60< 0.1

KamiokaSuper-K

Japan,USA2700

22.5H2O

5.5 0.7 - --

6000

750

220-

SNOCanada 6000

1.4H2O

1 D2O5 530

37770

C12,

eipe~ne Ae Ce

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.

Neutrons generated by muons underground

0 200 400 600 μs

Number of Events

Reactions for scintillation and Cherenkov counters2n nС H 2H O

e p e n 2 44 2~ 9.3 10e p e

E см

e ee e 2 45 2~ 9.4 10eee

E см

i ie e 2 45 2~ 1.6 10iie

E см

i ie e 2 45 2~ 1.3 10iie

E см

12 12* 15.1C C МэВ 12 (15.1 )С МэВ

0.5e

E МэВ

1.3e

E E МэВ

eNCe1212

eC12

eBCe1212~

~12 eC

MeVEthr 34.17 ms9.15

MeVEthr 4.14 ms3.29

242,

242

1023.1)20(

10066.0)10(

cmMeVЕ

cmMeVE

е

ee

cm2

cm2

cm2

cm2

MeV

MeV

The simplest case

Double neutron star (NS)

Almost all of the angular momentum can turn into an orbital angular momentum, Jоrb≤Jo, J= Jo-Jоrb becomes 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.

e – spectra of volume radiation for B-nucleonic gas + FD-electronic gas

ee p n The only reaction of URCA-processes:

Neutrino radiation luminosity per gramm(Ivanova et al, 1969; Imshennik, Nadyozhin, 1971, 1972)

,n e

p

NN kT

15

1 12

0

1 ln 2 11 exp sec

1e e

enp

qg

m ft m c kT

5 5

2

1~

1 exp1 expe

ee kT

q x

m c x

00 2.52.5 5.05.0 7.57.5 1010 2020

XXmaxmax(()) 5.0335.033 5.3035.303 6.3276.327 8.0088.008 10.0010.00 18.9718.97

Y(Y()) 5.5095.509 6.7506.750 7.2967.296 8.7578.757 10.5710.57 19.3219.32

1. Central parameter of rotating collapsar (t ~ 2.5 sec)2. Total energy of neutrino radiation (t ~ 6 sec)

(Imshennik, Nadyozhin, 1977, 1992):

2.5 10 ( ~ 10 100)c

52~ 8.9 10e e e

erg

max max~ ~ 30 50ckT x MeV

KTc10102.6

314106.2 cmgc)34.5( MeVkTc

MeV)5030(

The signal detected by LSD is

the first detection of a neutrino burst from the collapse of SN

1987A

?

The simplest case: the star is spherically symmetric, nonrotating, nonmagnetic.

Gravitational energy, the energy of nuclear radiation

George Gamow excluded completely the possibility of using 1D-spherical-symmetric collapse for explanation of SN explosion

«It is, in fact, much more likely that the lack of supporting pressure in the stellar interior will cause a very irregular motion of gas masses, some of them precipitating towards the center and other being ‘squeezed out’ and thrown away in the form of vigorous prominences»…

«The rotation of the star will exercise some kind of directing influence on this phenomenon since the presence of centrifugal force will hinder the inward motions of matter in equatorial regions». [Gamov G.: 1944, Phys. Rev., 65,20]