Transcript Document
Presenters:
AGAFONOVA NATALIA
BOYARKIN VADIM
Corno
Grande
LVD
H=3650 m.w.e.
Hmin=3650 m.w.e. <E>=280 GeV Eth = 2.2TeV at sea level
-rate (1 tower)~ 120 h-1
Stopping muon rate
(1 counter) 0.7510-3
- trigger: ε 40 MeV, 2 sc
Data taking trigger:
th=4MeV
(inner counters)
th=7MeV
(external counters)
Event duration – 1 ms,
th=0.6MeV (inner counter)
E–resolution: ~30% =1-5MeV
~20% 5 MeV
t–resolution: ~70 ns
L-shape
tracking
system
1m
1,5m
1m
Module –
portatank,
8 sc
The Tower
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
General idea
How can one detect the neutrino flux from collapsing stars?
Until now, Cherenkov (H2O) and scintillation (СnH2n) detectors which are
~
capable of detecting mainly e , have been used in searching for neutrino
radiation, This choice is natural and connected with large ~ -p cross-section
e
~е p e n
ep
~ 9.3Ee2 1044 см2
Ee 0.5 MeV
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.
n p d EE 2.2
2.2МэВ
MeV
The specific signature of event
How can the neutrino burst be identified ?
The detection of the burst
of N impulses in short
time interval T
А
t
T
1
N~
I ( E i ) ( E i )dE M
2 i
4R i Ethr
Сn H 2n
H 2O
Reactions for scintillation and Cherenkov counters
e p e n p ~ 9.3E 10
44
2
e
e
см
2
cm2
MeV
Ee 0.5МэВ
Ee E 1.3 МэВ
MeV
2
e e e e e ~ 9.4 E2 10 45 см
cm2
e
e
i e i e
2
2
e ~ 1.6 E2 10 45 см
cm
i
i
2
cm2
i e i e e ~ 1.3E2 10 45 см
i
i
C12 C12* 15.1 МэВ
( E 10MeV ) 0.066 10 42 cm 2
С12 (15.1 МэВ) ,е ( Е 20MeV ) 1.23 1042 cm 2
e
e
e 12C 12N e
C e
12
~e 12C 12B e
C e ~
12
Ethr 17.34 MeV 15.9 ms
Ethr 14.4 MeV
29.3 ms
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+
__________
56
56
e 26Fe0 27 Co*e
+
E
56
27
56
56
E
4.056 MeV
Co
Fe
27
26
E 40 MeV
Co
Fe e e 56Co
Ee Eo E
E 1.82MeV
56
e
СnH2n
E 1.72MeV
tot 4.24E 40cm2
So one can expect
~p
550 events from
e
and more than 700
events from e A & eC
in LVD
The possibility to observe the neutrino burst depends
on background conditions
The source of background:
1. Cosmic rays
0<E<
а) muons
b) secondary particles generated by muons (e,,n and 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
Tower Quarters
4Q
C=
1 TOWER
280 scintillation counter
(1.2 t/counter)
120 inner counters
3 TOWERS total
840 sc
1kt – scintillator
1kt – Fe
L
10.2 m
6.3 m
13.4 m
n 56 Fe 57 Fe* 57 Fe (k ), 91.7%
nFe-capture
nth
p
,
(~7MeV)
n54Fe55Fe* 55Fe ( ), 5.8%
sc Fe 130 s
n35Cl 36 Cl * 36 Cl (k ), 75.8%
,
n
p
nth
(2.2 MeV)
np-capture
np D* D
0.334 barn
sc 185 s
72294
Neutrons= 5133.7
843.4
dNn dt B N 0 exp( t )
0-4 MeV
4-12 MeV
23502
N=72294
Neutrons= 5949.6
908.2
0 +
n
e+e-
19603
Neutrons= 18537
2684
For determining the specific neutron yield
number we used the formula:
n N
tot
n
l N
ev
N
the number of searched events
tot
n
N N
sc
n
Fe,Cl
n
l L
in
the average muon path length
total number of muon events both
single muons and groups, and
electromagnetic and hadronic cascades
event
N
g
n 11 10 (
4
cm
2
)
1
6
δ=0.07
N. of ev. Nn/ev.
muons
0-4
MeV
4-12
MeV
Single 1µ
72294
5704
1124
6282
Muon bundle
6611
1211
7822
nFe,sc
(cm2/g)
nsc
0.155
3.0610-4
1.8410-4
0.547
10.8510-4
6.5110-4
neutron
(cm2/g)
23502
1.8410-4
kµ (k=3.54)
83264
cascade
19603
20597
3580
24177 2.03
-
-
Total
116710
33423
6148
39571 0.557
1110-4
6.610-4
Per 1 (all processes)
4.3810-4
7
LVD
En>0MeV
8
dNn dt B N 0 exp( t )
q VFe VPVC VFe VPVC Vsc
K=240/146=1.644
sc = 0.9
Fe,Cl = 0.75
q=(VFe+VPVC)/(VFe+VPVC+Vsc)
K
Nn N
3
V(M pvc=380kg) =0.86 m
n
0.5–4 MeV
N(<4MeV)
3
=185
µs
=7.8
g/cm
MFe
=9.46 t
(np–capture in
scintillator)
=30081
4 -12 MeV
Msc =9.2
t
(nFe,Cl - capture)
.
qN
Fe,Cl
n
/( N
сц
n
54948
q=0.160
N(>4MeV)
3
=134 µs
10107
=0.78
g/cm
=4611
N
Fe,Cl
n
) 0.155