supernovae explosion detection vs neutron background on example of underground detector
DESCRIPTION
Supernovae Explosion Detection vs Neutron Background on Example of Underground Detector. LVD. Presenters: AGAFONOVA NATALIA BOYARKIN VADIM. Corno Grande. LVD H=3650 m.w.e. H min =3650 m.w.e. =280 GeV E th = 2.2TeV at sea level. - PowerPoint PPT PresentationTRANSCRIPT
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
1m
1m
1,5m
L-shapetrackingsystem
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
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
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
0.5eE МэВ
1.3eE 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
So one can expect 550 events from
and more than 700 events from &
in LVD
eCoFee *56
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
0+
24024.4 cmEtot
Yu.V. Gaponov, S.V. Semenov
СnH2n
CoeFe e5656
MeVE 72.1
MeVE 82.1EEE oe
e
pe~
Ae Ce
The possibility to observe the neutrino burst depends on background conditions
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
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:
4QTower Quarters
10.2 m
6.3 m
13.4 m
C=
L
1 TOWER 280 scintillation counter (1.2 t/counter) 120 inner counters
3 TOWERS total 840 sc1kt – scintillator1kt – Fe
(2.2 MeV)nth
p
n
np-capture
(~7MeV)
p
nth
nFe-capture
sFesc 130
DDnp *
,
,
barn334.0
56 57 * 57 ( ), 91.7%n Fe Fe Fe k
%8.5),(55*5554 FeFeFen
ssc 185
%8.75),(36*3635 kClClCln
72294
Neutrons=5133.7
843.4
)exp(0 t
n NBdtdN
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:
6
evtotn NlNn
ClFen
scn
totn NNN ,
inLl
eventN
12
4 )(1011 cm
gn
the number of searched events
total number of muon events both single muons and groups, and electromagnetic and hadronic cascades
the average muon path length
muonsmuons 0-4 0-4 MeVMeV
4-12 4-12 MeVMeV
N. of ev. N. of ev. neutronneutron
Nn/evNn/ev.. nnFe,scFe,sc ((cm2/g)cm2/g)
nnsc sc
(cm2/g)(cm2/g)
Single 1µSingle 1µ
722947229457045704 11241124 62826282 0.1550.155 3.063.061010-4-4 1.841.841010--
44
Muon bundleMuon bundle
235022350266116611 12111211 78227822 0.5470.547 10.8510.851010-4-4 6.516.511010--
44
kµ kµ (k=3.54)(k=3.54)
83264832641.841.841010--
44
cascadecascade
19603196032059720597 35803580 2417724177 2.032.03 -- --
TotalTotal
1167101167103342333423 61486148 3957139571 0.5570.557 11111010-4-4 6.66.61010-4-4
δ=0.07
Per 1 (all processes) 4.3810-4
7
LVDEn>0MeV
8
0.5–4 MeV 0.5–4 MeV
(np–capture in scintillator)(np–capture in scintillator) =185 µs=185 µs
N(<4MeV)N(<4MeV)
=30081=30081 5494854948
4 -12 MeV 4 -12 MeV
(nFe,Cl - capture) .(nFe,Cl - capture) . =134 µs=134 µs
N(>4MeV)N(>4MeV)
=4611=4611 1010710107
nn
KNN
K=240/146=1.644sc = 0.9Fe,Cl = 0.75
scPVCFePVCFe VVVVVq
q=(VFe+VPVC)/(VFe+VPVC+Vsc)
q=0.160=0.78 =0.78 g/cmg/cm33
=7.8 =7.8 g/cmg/cm33
MMscsc =9.2 t=9.2 t
MMFe Fe =9.46=9.46 tt
VV(M(M pvc pvc=380kg) =0.86 m=380kg) =0.86 m33
)exp(0 t
n NBdtdN