Low energy neutrino physics at high intensity pulsed proton accelerators

Low Energy NeuCrino Physics a~ High IR~ensity Pulsed Pro~on AeceleraCors B. Z E I T N I T Z Kernforschungszentrum Karlsruhe and University of Karlsruhe, F.R.G.

I°IITROIICTIQI

During

the

particular new

last in

decade common i n t e r e s t neutrinophysics

insights

were

gaimed

in

t h e weak i n t e r a c t i o n

has c o n t i n u o u s l y

by

discoveries

increased°

like

the

and i n

Fascinating

neutral

current

interaction, t h e ~ and Z b o s o n s , t h e z = p a r t i c l e eto=o Most of t h i s work ~as p e r f o r m e d a t v e r y h i g h e n e r g i e s at PETRA, PEP and CERK° B~t in

mature

energies°

weak In

physics

mamely

physics

energy

The

Walecka

proposals know

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proof

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the

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neutrino

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T°W= D o n n e l l y

the

and

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seventies even

currents

cross smaller

particles°

already° first

could

to

be

completion

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the

one

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445

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446

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Low Energy Neutrino Physics

447

KARMEN SNS =TARGET \

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Low Energy Neutrino Physics

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B° Zeitnitz

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Low Energy Neutrino Physics Table

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NEUTRUNO BLOCKHOUSE

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chamber

?

scheme t h e

i

In

drift

A

of Nemtrim~s

class

Le

The c o n s e r v a t i o n

construcand e n e r g y

scattering°

Nemtrime

the

standard

under

angular

L~s~

because of

Majorana

from

are of

by about 7m

method°

Fmmdamemtal

conservation

oscillate

blockhouse

measurements

Test of C o m s e r v a t ~ o m interesting testing

for

is shielded

?HYSICS NOTIVATIOI

~ZZo~

those

source

neutrino

electrons

projection

ZIIo

A very

the

dedicated

detector

time

The neutron

Le + L are

:

+

-i

%4-

L

&L = 0

and

we w o u l d have two p o s s i b i l i t i e s {a)

L =

ZL x = c o n s t

(b)

L = I(-i)

Lx = c o n s t

&L x = 0 :

with

X = e~z~%

457

Low Energy Neutrino Physics

A suitable

example +

This

reaction

performed

for

the

test

÷

is

p-decay

:

-

+ e

+

v

+

ve

allowed

by

(b)

+ e

+

v

+

ve

allowed

by

both

few

examples

is

one

already°

of

the

SoEo W i l l i s

et

alo

only

where

(12)

(~3)

an e x p e r i m e n t

compared

the

reaction

has

been

rates

of:

#

in

a

Cerenkov

LAMPF (Nil

+

n + e

(14)

ve + d

+

p + p + e-

(15)

counter

beamstopo 80),

to

at

that

melle The

Ve + p

pulsed

filled

Their

result

be c o m p a r e d time

beamstop

source

the

search

for

(&L = 0 ;

&L

= ~AL e = i

) :

Use

of

the

detecting with

In

found

iR

If

is

we r e s t r i c t

The mass

portion

~ ,

R = result

time

wimdows very

Ve and

flavour

v~

theoretical (Com 83~

given

for

ourselves

of

was:

and

D20

0o001 from

at

the

± 0°06 Gargag

~

is

particularly

oscillations

÷~

Ve

and

nuclear

sensitive

( 16 signatures

appearance

)

of

the

measuremeRts

errors°

the

textbooks

iRtroductio~

ratio

H20

experimental

neutrinos

to

of

± 0o15o

neutrino

leads

systematic

the

;

corresponding

meantime

of

ve

reactions

small

the

+÷

the

the

: R = 0o13

for

a mixture

for

with

suitable

v

with

the

L = A

description

Bi!

77~

Per 82)°

definition to

the

e~

Lagrangian M~ ~

+

of

the

In

M

oscillations the

following

can

we h a v e :

:

v

v

be

a short

variables:

generations

is ~

of

(18)

-l= ~

Po oo

tD

0

0 o'} 1,o

+

¢D

(D

Po

~o

~o

-g:~

r~ r~

O

o

o

-1=<

ii

o

~0

~.

0

b,1 ~0

0

II

O

o

f0

0

II

0

¢e

o

tO

~0

r~

II) -3

r~

A A

II

L.

II

0

c~

ro

0

i-o

II

-h

II

m

"o

0

III

"o

ii

0

tD

I

O

II

e~ z~

r~

o

c+

<

r=rl

L. 0.

o ~ ~<

i1)

b~

~°

c~

o

rB

fD

---4

O

o

+

I

II

Ix.3 O

~o

+

O

O

II

O

m

~ ° ° "g:

f~

~0

I,o

fD

f~

I'D

N

O

3

'~

'~

~

¢÷ ~o

m

¢'~

r~

O

~

C)

3

0

O

O

~ ~°

~

II

0

,-~°

O

f3 O

.o

0

d)

,~0 0

~0 N

0

~°

"in

3

3

o

(30

II

II

3 11)

b~ tO

150

On Oo

Low Energy Neutrino Physics

459

v(t) and

with

:

P (v

+

v ) p

v~

-> v~)

£i

mi = p + -2p

vp

+

=

=

1

sin2

;

R and

E2-EI 2

2e°sin2(

t)

o

(24

2

inserting

2

With and

:

ml~OC

P (v

+

: m2 2 c 3 . 2-mi ot) 4p 5

sin 2 2Oosin2(

o

(25

E

4 -

2~

m2 using

this

v#) = i

c

2

Am

,~e 1,

; 1

v

°

(v '# ->

v P)

p -

P

X

,

C

=

cot

:

gives P

v

-> v e )

sin 2 20osin2(

=

1 o 2 7E ~Am2

0X)

(26

v

with

ao

&m

2

o

;n

Detection

The

of

selective

verse

~-decay

Vo

eV

+

2

;

Ev

vF +

ve

reaction of

12 C

12C

+

in

~4eV

;

used

for

the

the

following have

e-

+

L2N -

17o3

conditions to

electron

neutrino

detection

is

in.

:

e++

oscillation

m

appearance°

+

Thus

X in

be

fulfilled

MeV

11

msec

ve +

12 C

for

the

(Z7) +

15o3

MeV

monoenergetic

(30

Mev)

simultaneously:

io An e l e c t r o n of E = 30-17 = 13 MeV is detected w i t h i n a

v

P

÷

ve

defined

volume element V during duration of the beampulse (2x100 nsec)o

460

B o Zeitnitz

Within

2°

the

following

20 msec

17 MeV [mean e n e r g y volume element 3 cm

background

at

~sec

after

the

with

the

same

normalized° ~i <

10 MeV]

are

expected

detector

beampulse

to

i

the

the

during

of

the

suppress

ve f r o m

first

10

during

the

the

same 5000

all

the

will

the

the

of

about

cos-

first

be

LO

detected

measurement

during

~sec a f t e r

at

practically

~.-decay

of

events

within

be k e p t

KARMENo S i n c e

of

maximum e n e r g y

be d e t e c t e d

result

number

with

V can

to

neutrinos

signature

We c a l l

and t h o s e

has

Vo E x p e r i m e n t a l l y

The c o m b i n e d s i g n a t u r e s mic

a positron

can

beam on

beam p u l s e

be

period

N~ ve

ve

Thus

ratios

like

R;

: N
=

,°

R2

< ~V

=

N> ve

will

be p r a c t i c a l l y

N>V e

e

N<

+

N>

ve

independent

of

the

ve

absolute

value

of

the

neutrino

flUXo Figure to

8ao

shows

organic

region

the

left

to

the

(90%

experimental

results

Ev = 3°°°8 from

the

also

shown

MeV)

for

of

the

limits

confidence

at

a

comparison

cannot For

reactor

at

(Fei

CERN ( v

small

mass d i f f e r e n c e s

values

where

be

is ~

Ev

be c l e a r l y the

the

recent

(~

given°

The

by

the

experiment

84)

of

KARMEN (50

reached

comparison

÷ ve

(CHA 841oAS can

to

L of

v~ + ve a p p e a r a n c e °

disappearance

GSsgen

sensitive

detector in

curve

level)°

from the

of

&m 2 and s i n 2 2 e

CHARM c o l l a b o r a t i o n

especially

region

to

corresponding

measurements

is

sensitivity

sciatillator)

~

x;

The r e s u l t

=
GeV~is

seen o u r m e t h o d

mixing

angle

high

energy

+ ~e

a p p e a r a n c e can

0 in

measurements

a

cannot

compete° bo S i m u l t a n e o u s l y for

at

for

detection

a

pulsed

with

beamstop

moderation

neutron detector

source°

The w e l l

known

be s e a r c h e d

selective

reaction

is: 5e

After

v~ ÷ ve ~ ~

of

+ p

the

÷

e+ + n

neutron

within

may be a b s o r b e d by G a d o l i n i u m producing

T-rays

of

total

(27)

the in

energy

organic the

of

liquid

scintillator scintillation

a b o u t 9 MeVo

the

Low Energy Neutrino Physics

The

energy

Because

spectrum

of

the

of

the

strong

spectrum

is

E e + > = 42 ~eVo

the

shifted

increase

trons

is<

positron

positrons

to

of

higher

from

the

can be c h o s e n

at

about

(27)

cross

energies°

Therefare~

the

461

is

shown

section

in

with

fig°

9o

energy

the

The mean e n e r g y

of

lower

detection

level

for

the

posi= of

15 MeVo

/

10.C

100

!

__ l.Oi

v~-

>o

ve

E

0.1

b}

001

001

0001

0.01

01

10

000I

001

0.1

1.0

sin 2 28

Fig°

8°

Experimental

ao

v

÷ ve : A p p e a r a n c e

bo

vp

+ ~e : A p p e a r a n c e

sensitivities

years for

A true

-

event

has

to

A positron

is

and 5 psec

after

Coincident

#-rays

tion

in

tion

point

of

at

two

the

for

oscillation

sensitivity

the

( 90% CoLo)

of

KARMEN f o r

of

KARMEN

two

full

beam

SNSo

sensitivity

full

fulfill

detected

Gd a p p e a r

sin 2 2 ~

beam y e a r s

the within

at

following the

time

the

SNSo

conditions: window

between

about

0°5

a beampu]seo of

total

within positron

sum

energy

a volume within

of

of

about

a time

about 3 i m

9 MeV f r o m

absorp-

around

detec

window of

the

about

100

FSeCo

462

Bo Zeitnitz

2000

1500 22 20 o 18 15 % 12

1000

i~o 8

500

100 5

10

I

15

I

20

[

25

J

30

I

35

i

40

45

ao

Fig°

9o 1o

Energy

distribution

11o C r o s s

section

111oEnergy tion This

signature

Because

of

expected

to

at

very

CERN (CHA 8 4 ) °

merits

of

small

mixing

f~rther with

~ARMEN advantage i

The d e t e c t i n g point

of

discussed

view in

large small° in

at

can be c l e a r l y the

SNS ~ i l l

that

both

SNSo

reactions

(17)

of

part

neutrino 1!Io3

of

high

this

the the

a

seen t h a t

(27)

paper°

the the

are

be r u n

also

experi~ for

differenceso

A

simultaneously

interesting nuclei°

the

experiment

~easurements

will

with

from

oscillation mass

is

sensitivity

results

small

also

shielding

beam s t o p

sensitive

value°

positron

realistic

energy

experiments

and

from

with

be most

interactions

a negligible

through of

simultaneously

the

to

signal

result

oscilla-

+ ~e

background

and t h e

It

is

~

together

at

with

for

scattered

The

84)

~e ÷ p ~ e+ + n a s s u m i n g

energy

figo8bo

(Fei

angles

detector

cosmic

neutrons

shown

experiments

of P = I

reduce

fast

be is

vp f r o m t h e SNS ( r e l a t i v e units) + ve ÷ P + e + n ( s c a l e on t h e r i g h t )

for

relative

from

calculation reactor

will

the

background

of

distribution

probability

i

50 Ev [MeV]

This

from

the

will

be

Low Energy Neutrino Physics

IXZo2

Present

NEUTRXNO:ELECTRO~

discussions

action

are

the

reaction

were

very

mostly

limited

v~

+ e-

to

vp

÷

important

for

interaction°

But

measurements

are

of

of

reactions cross

sign

and s i z e

Though can

of

details

stringent

measurements

the

of

weak

the

reactions

neutral

standard

current

model

from

:

÷ e-

÷

~

÷ e-

IZg)

ve ÷ e -

+

ve + e -

{30)

~e + e=

'>

Ve + e -

(31}

interest° and

in

Even

reaction

neutral

the

a (30)

current

region

of

tools

the

would

are

give

the

information

on

the

current

physics

energies

machines°

of

electrons of

difficult

physics

results

measurement

very

proton

the

be t h e scattered

rough

- charged

nuclear

pulsed

will

of

first

experiments

intensity

experimental

interesting

distributions

{30)o

of

the

of

Most

angular

of

These experiments

{28)

high

of

of

tests

on a l l

corresponding

the

discovery

section

energies°

+ e-

the

be r e a c h e d

stop

cross

high

inter:

~

section

the

total at

neutrino-electron

->

(28)

total

the

on

v p ÷ e-

fundamental

measurements in

more

the

+ e-

the

more

detailed

SCATTERZ~G

experiments

of

463

interference° goals

at

Before

motivation

both the

beam=

going

into

be

dis-

will

cussed° The

structure

cross

of

sections

the

of

formulas

reactions

is

especially

true

as

in

experiments

model

future may

be

development° a paper

of

more In

already

the

first

1979o

to

(31)

is

differential

and

relatively

searches

for

part

we the

and n e u t r a l

deviations

begin

at

an

nomenclature

from

earlier follows

interference

This

model° the

of

that

used

in

But

standard

state

SoPo Rosen and Ho S p i v a k current

total

simple°

Glashow-Weinberg-Salam

Eo F i s c h b a c h ,

chargedin

(28)

the

standard

interesting

the

Bo K a y s e r ,

who d i s c u s s e d toting

in

describing

the

(Kay ve-e

in 79)

scat:

464

B° Zeitnitz

The H a m i l t o n i a n

is

~ritten

_

:

ri

,~/-~

= i

CP i n v a r i a n c e

handed

i~ (%vFi~v)

, i-~5 , i y k

demands

The l a b o r a t o r y { vL)

the

form

:

G

H(,~,e=) with

in

:

'

iYkY5

,

cross

handed

Diy5)~ e ; i

o-k,

OS = Dp = DT :

differential and r i g h t

~e?i(ci+

0

= S,P~V,A,T

and

sections

Ci~ Di

for

( v R) n e u t r i n o s

{32)

realo

scattering

from electrons

of

!eft

is

given

by : d-y'd~ vLe)

=

~o°Ev

vRe)

:

~ oE [ C+B(I-y)+A(I-y) o v

dy with

~o

4°3078 xlO

=

The c o n n e c t i o n the

center

Inserting

o f mass i s

this

cross

section

tered

electron

related

by

into at

the

and

variable

given

=

y

=

2 ]

(33)

2 ]

(34)

Ee / E

y and t h e

v o~

m

e

<<

scattering

E

v

angle

(33)

and { 3 4 )

forward

and t h e

8 in

by :

s i n 2 {~- ~ m )

{36) shows a v e r y

angles°

~aboratory

The kinetic

strong

laboratory energy

peaking

angle of

the

of

for

the

the

scat-

electron

are

: sin28

and w i t h

45 cm 2/NeV

between

y

[ A+B(L-y)+C(L-y)

E e >>

e

-

2me Ee+2m e

(L-y-

me ~ oy) 2E v

(37)

me and Ev >> me: sin2ee

:

2m e T--- (/_y)

{38)

e

Thus f o r any f i x e d e l e c t r o n g i v e n by : angl e emax e max sinee =

energy

~

e

Ee t h e r e

is

a maximum

scattering

(39)

Low Energy Neutrino Physics

Relation tering The

(39) as w i l l

can be used

as

be d i s c u s s e d

later°

measurement

the

coefficients

ling

constamts

of t h e

the

of

differential

A,B~C i n i~

part

(33)

signature

cross

way

for

sections

and ( 3 4 ) o T h e y

following

A = (gV+gA)2 +

the

465

are

we

would

related

to

determine the

1 {Cs+Cp)2

+._~1 ( C s ~ C p = 4 C T ) 2

(40)

16

B = 2 C T2 - - ~1 ( Cs2 +C~)

C = {gV=gA ) 2 + ~

It

can e a s i l y

{417

{Cs+Cp ) 2 + 1

16

gV ~ I ( C V + D A ~ 2

{Cs~Cp+4CT ) 2

16

;

gA

be seen how t h e

formulas

(43)

simplify

if

the

usual

It is interesting to o n l y V:A interactio~

assump:

note that is taken

account°

It

has been shown

of

the

trinos 1o I f

sign

of

are

Dirac

the

(Ros 82~Kay 82)

B only

would

or Najorana

~eutri~os

are

that

the

be s u f f i c i e n t particles

Dirac

experimenta~ to

decide

2o Zf

the

meutrinos

by a two c o m p o n e n t ~M -

this

case the

are

particles

field

Majorana (~

in

principle

so-called

~f m

# 0 : AL = 2 ~ o u l d

osci~lationSo

with

Majorana

CV = DV = CT = D7~ = 0

particles,

= charge

~ i ( ~ v + ~ c)

,°

Ci

be a l l o w e d

determinatio~

whether

the

neu-

:

t y p e s S~P~T,V~A a r e a l l o w e d . L = Le,L~,L~would l y and i n a d d i t i o n &L = 0 { i f m V # 0)o

In

{42)

~ 1 (CA+DV) 2

t i o n s o f Cs = Cp : CT = 0 a r e a p p l i e d ° the coefficient B does Rot a p p e a r i f into

ccup:

:

16

with

scat-

they

conjugate ~vc =

condition + 2C i

°, Di

including

all

interaction

be c o n s e r v e d

could

of

seperate:

be d e s c r i b e d

~v):

Co@~oC =z

is

va~id

+ 2D i

: (44)

"neutrino:antine~trino"

466

B o Zeitnitz

Since tion

the

coupling

(44)

together

cient

Bo

Thus

that

tensor

particle° of

or

Dirac

discussion

measurements sion

be

of

of

be p r e s e n t

mot

The

the

a negative positive zero

we see

meutrino

then

present

the

condicoeffi~

from

(41)

must be a D i r a c

neutrino

experimental

to

Najorana

va~ue of t h e then

and t h e

or

sufficient

versality

showed

angular

fundamental

we s e t :

culated

to be

negative

type,

is

to

real

could

be

information

differenciate

on

between

both

results

from

assumptions°

above

would

be

leads

out

must

B would

CS and Cp are

(41)

B turns

interaction

possible The

with

if

coupling !f

Majorana

weak

constants

by way

of

distributions interest°

charged

current

of

that

the

To s i m p l i f i y

CS = Cp = CT = 0 ( 4 5 ) °

the

example

Under

the

interaction

the

scattered the

assumption

coupling

electrons

following of

constants

discus= #:e are

unical-

from: CV~ A +

CV,A=I

;

DV, A +

DV,A-I

(45)

We o b t a i n : e

gv

where rent Using

=

e stands (NC) (40)

+

for

1

;

charged

current

:

+

1

(CC)

and

I461

~ stands

for

neutral

cur=

interactions° to

(45)

we o b t a i n

~ (Vee-)

=

~o E

~(

=

~o E

Vee- )

from

v

(33)

and

(34)

:

F Ae+ C # ( L - y ) 2 ]

,[47)

2 ]

(48)

[ C ~ + Ae ( l - y )

d~(

e-)

=

~o E

[ A ~ + C~(l=y) 2 ]

(49)

d~{;

e: )

=

~o E

[ C# + A~(l:y)

(5O)

2 ]

Low Energy Neutrino Physics and

Ae

(gv

gA

+ g )2

= (g

CC

NC As can be

clearly

seem

appears

only

in

feremce

term

between

The t o t a l

the

cross

The

only

of

{54)o

for

in

figoLOo

amnular

simulation rector

at

The

Deviations tars

of

would

the

the

from

is

~e

of

for

includes

could

be p e r f o r m e d

of

much

cross

in

the

error

Ve:e-

inter:

until

lower

determime

plane

ellipses

now

statistics

sections

g~g~

different

which

gives

are

values

bars°

is

a measurement

aR

:

total

rings

also

contributionSo

and w i t h

the

contribution

the

usimg

result

a 50

to

of

a

realistic

l~quid~

Argon

de:

~niversality

gV

= -

the

overlapping

comes

:T:

i

from

model

2sin 2

angle

possible

and Z o p a r t i c l e s

,~ould

Heasurements

show up im s h i f t s

of

differential

of

cross

the

ten=

sections

gV amd gA s e p a r a t e l y °

Weinberg

mow a l s o

of

(53)

corresponding

ellipses°

determine

constraint

~

~hich

of

annular

The $ 1 a s h o w o N e i m b e r g : S a l a m

of

~_

I~

current

current by

Intfo

SHSo

the

Therefore~

+

ring

~L~

~hich

given

intersection

elliptic (68%

the

then

measurements

g~ and g~ w i t h

The

are

elliptic

charged

and c h a r g e d

measurements

correspomdlmg shown

meutrai

v~e e x p e r i m e n t s

energy The

the Ae

%z [ ( ~ + ~

reliable

high

{51)

coefficient

sectioms

O(~ee~ ~ :

were

from

467

eW

area

GW f r o m the to

recent!y

predicts o ~ of

g~ the

purely

reactions use

the

measured

: L 2

ellipses

a determination

interaction°

÷ e e

information at

gives

leptoni¢ e e

(55~,

of

Another

and

e+e ~

the

masses

CERNo The e x t r a c t e d

+ ~ ~ o It of

the

values

W

for

468

B o Zeitnitz

sin2e•

are

partly

dependent 2 / mW

p : This

parameter

radiation recent

is

critical

fixed

to

review

p =

by

the

measured sin

The

of

order this

of

in

masses

error the

0o01

important

+

B~hm

value

of

the

of

parameter

the

be

this

neglects From

(Boa

we

purely

84)

p = 1o12

have

from

CHARM)

a

:

± 0°23°

~ and Z o one g e t s : ;

p = 0°97

expected

from

scintillation detector 2 s i n ~ o Thus we w i l l at

but

mHigg s e t C o ) o

for

parameter

formulas

Ap (mTop~

;

± 0o010

to

our

{ v e scattering,

_+ 0 ° 0 5

eN = 0o221

experimental

measurement the

2

Ao

I

experiments

s i ~ 2 0 W = 0°22 Using

p - 1 in

like

interaction

exact

(m~ cos 2eW) o

corrections

lepto~ic

on t h e

very

of

the

± 0°04° total

KARMEN a t

have

another

cross the

section

SNS i s

of

determination

low energies°

sin2 ew

expected from SNS

ve e-

~-.75--

6 8 % C.L.

Ig~ .l-t-

V~e-

.5-

l

0-@

Fig°

10o E x p e c t e d

68% c o n f i d e n c e

proposed gether

with

re-e-

total

results

ellipses cross

from

other

in

section

the

g~/g~

plane

measurement

v-e ° s c a t t e r i n g

at

for

the

SNS~ t o =

experiments

Low Energy Neutrino Physics

Measurements

of

the

differentia]

sensitive

tests

of

the

theory.

system

proposed

for

the

is

cross

sections

Therefore~

neutrino

469

will

a second

experiment

allow

much more

dedicated

detector

KARMEN° The g o a l

is

to

~

e

_

measure

the

within

differential

at

least

coefficients

A,

this

difficult

solution gaps

(~10

merit

of

cm) the

resolution

scattered uses

B~ and

C in

equations

using

used

is

the of

have

time

the

= 0°23

of

(33)~

(34)°

for a of

very

good

very the

energy

large

measure-

good low

loss

on

technical with

a serious energy

the

work

a rough

with is

of

One

detector

MeVo B e c a u s e The

and

Prototype

placeso

Argon

scattering

m

vee

determination

method

detectors. a

sum o f

different ]iquid

combined

5-10

multiple

energy

energy

of

problem

if

should

be

signa]o

Degrading

be a v o i d e d .

from

is

tracks

gaining

to

at

the a11ow

projection

track

cross

expected

on

of

would

a 50 t o

energies

for

differential

sin2eW

going

e]ectrons

walls

energy

is

discussion

conventional

completely

The

which

angSe

one

passive

bins

down t o

the

section

three task

under

cross

section the

shown i n

as

a

function

of

electron

G1ashow-Weinberg-Salam fig°11o

The c o r r e s p o n d i n g

model

recoil

and

angular

using

distribu:

7

~2 c~ X

>

~

8

I

4

i

Vp +e-

\

@ > W

0

10 20 30 4,0 Energy of Recoi~ Electron Fig°

11o Number

of

one f u l l sents

the

v-e-

scattering

beam y e a r

at

differential trino

events

as a f u n c t i o n

SNS: The shape cross energies

50

sections

of

the

averaged

NqeV

of

energy

curves over

for

repreSNS n e u -

470

tion

Bo Zeitnitz

is

presented

a maximum a n g l e effective

for

figol2o

neutrino

nuclei

i~

the

the electrons

the

separation

sources

will

mainly

in

material

the

case of

from t h e

reaction

Ve+L2C + e-+ 12N { ! i

co (D

I

I

from

energy°

for

detector

reduced

As e x p e c t e d

each e l e c t r o n

signature

pulsed further

in

eq~atio~

This from

fact

or

inverse

Z2Co T h i s

12C by d e l a y e d

msee)

I

there

is

can be used as ~n

background

come from

4°At

(39)

which

at

the

B~decay

of

the

background

may be

anticoincidences

using

+ e + + ~e+L2Co

I

I

t

I

I - -

x

Ve+e-

z~

~5-

Ve + LOAF

5 forward

I

~0

Fig°

12o

strongly forward

~-decay

I

I

I

30 40 50 50 eiec[ron angle 8e

Angular

Argo~ d e t e c t o r ° inverse

i

20

bockword sum

distribution

The s o l i d and

peaked to

line

of

I

[

70

80

electrons

in

a liq~id ve + ~°Ar

shows t h e

sum

of

ve + e= s c a t t e r i n g ~

the

latter

being

is

assumed

that

forward

direction°

a~d backward d i r e c t i o n s

cannot

!t

be d i s t i n g u i s h e d

Low Energy Neutrino Physics

In

addition~

since

the

i~verse

B-decays

whole

angular

small

angles

Since

last

the

angular

the

and s u b t r a c t e d

an

Irvine/Los

stop

84

I:

Because

is

extremely

(Bur

experiment central rains for

very

of

plastic

III°3

in

Donnelly,

R°D°

In t h e

on t h e

tools are

situation

neutrino

in

Peccei for

are t h e r e f o r e

results

this

variables° lecture

The

study

to

15 to

of

of

been

9% t h i s

cosmic

back-

developed°

sensitive

2°5

LAMPF beam

6% or

suppress

has

of

and t a l k s

and

J:D°

subject the

type

mass°

cm t h i c k n e s s

It

The con:

alterna-

There are about 40 c a n d i d a t e s

of

NICLEI

weak

since

interactions

at

Walecka

least

have

extraction for

completely

of

the

~a]

75,

physics

some t i m e

ten

has been

years°

pub3ished

(Don 84~ Don 79,

improve w i t h i n

only For

notes of

factor

the

being

T°~°

excellent

Wal 83 )o The

from e x p e r i m e n t a l

already°

missing°

There

the

few y e a r s when t h e p u l s e d

next

is

But e x p e r i m e n s o m e ~ope

that

can be used°

fo]}owing

the

of

this

available

still

will

sources

the

duty

ar~tishield

scintillator

many a r t i c l e s

review articles

to

scattering°

interest

expressed

extended over the

at

order

NEITRINO INTERRCTIOIS I ! T I

The t h e o r e t i c a l

tal

In

chamber modules°

meutrino-electron

theoretical

high

consists

flash

from

experiment is

collaboration

the

plastic

are

electrons

may be e x t r a p o l a t e d

scattering

Alamos

of

the

12)°

active

target/detector

results

14 a n d ! 5 )

difficult°

effective

40 l a y e r s

ted w i t h

{fig°

of

background

summer a n e u t r i R o - e l e c t r o n by

a

figso

remaining

performed

ground

distributions

(see a l s o

range

471

some b a s i c

a detailed

of T°~°

weak

ideas

are m e n t i o n e d m a i n l y

discussion

Donnelly

interactions

the

reader

is

to

define

referred

to

(Don 84)° with

nuclei

has

two

interesting

aspects: 1:The

mucleus can be used as a m i c r o s c o p i c

dy of

the basic

2°Neutrino

structure

interactions

investigation

of

of

with

nuclear

laboratory

for

the

stu-

t h e weak i n t e r a c t i o n °

muc!ei

structure°

may s e r v e

as a n o t h e r

tool

for

472

B. Zeitnitz

There are many very with

nuclei.

i n t e r e s t i n g proposals

But the f o l l o w i n g discussion

for is

neutrino experiments

r e s t r i c t e d to examples

where i t

is r e a l i s t i c to expect r e l i a b l e measurements w i t h i n the next few years. The t a r g e t nucleus is 12C in a s c i n t i l l a t i n g d e t e c t o r .

The level scheme is shown in f i g u r e 13.

20.4 ms

1+ 1 r _ _ 15.1MeV

+

,

~

3oc \

1.1

llOms •

1+.1

7

(o,~')

/0+.0

~I 12 C

J~ ,T

6

Fig. 13. Isobaric spin t r i p l e t

of

12B,12C and 12N

We hope to observe two types of reactions with the neutrinos from the SNS: 1. I n e l a s t i c s c a t t e r i n g of

v~, ve and ~

neutral c u r r e n t e x c i t a t i o n of a.

0+ 0 v

+

E = 15.1 MeV

v/ + P

1 2C* ( 1 5 . 1 )

(56)

Ve + 12C ÷

ve +

/

I 2C* ( 1 5 . 1 )

(57)

T~I~ + 12C +

-vp / +

1 2C* ( 1 5 . 1 )

(58)

The decay of this famous a 15.1MeV

;

+ 12C ÷ P

I

1+ 1

from 12C leads to

12C l e v e l s with defined AT and M .

level in l)C occurs with more than 90% via

y-ray directly to the groundstate.

The reaction

should be a purely isovector

process.

In the long wave-

length limit the cross section can be estimated in a rather modelindependent way by using the B-decay rates of 12N and 12B which are

Low Energy Neutrino Physics

473

the analog states of the 15.1 MeV l e v e l . From r e f .

Ev-E x

LWL 0

i V

where: E

( Don 79) we have:

1 . 0 8 x l O - 3s

=

\-q-/

8,2 K2 (cm 2)

(sg)

Vl

= neutrino energy in MeV; Ex = 15.1 MeV; MN = nucleon mass V

The constants

PA and K are

which would be

given

by

the

isovector axial

BA = K = 1 in

measurement of

the t o t a l

would provide

a model independent

the

coupling constants

WSGIM model.

Thus a

cross section f o r e x c i t a t i o n of t h i s determination

of

level

these coupling

constants. The r e s u l t s of a simultaneous measurement of the i n e l a s t i c s c a t t e r i n g of the neutrinos ve + 9p

which appear in the time window of 0.5 to 5

psec would provide in addition a t e s t of u n i v e r s a l i t y . The signature would be a peak at 15.1 MeV in the summed l i g h t output 3 of the c e l l s w i t h i n about 1 m of the s e n s i t i v e volume. The cross section

for

reaction (56)

MeV. U s i n g equation

(3)

can be calculated f r o m ( 5 9 ) f o r Ev = 29.79 with

p = 3/4

for

;p

and

obtain f o r the energy d i s t r i b u t i o n of the sum of 2 N(¢) d¢ = (18 ¢ - 16 ¢3) d¢ with

¢

= E /52.83 V

Inserting

(60)

into

(59)

;

p = 0 for

ve we

vp and ve : (60)

¢ < 1 and i n t e g r a t i n g gives

the

total

counting

rate expected f o r neutral current e x c i t a t i o n of the 15.1MeV l e v e l by ~p

and ve (2202 fby -1 f o r a distance of 16 m, see also table I ) .

The signature of reaction (56) would be simultaneous detection of

y-

rays during beam on time and with a t o t a l summed energy of 15 MeV in 3 about 1 m The energy r e s o l u t i o n in the s c i n t i l l a t i o n

a volume of detector i s which w i l l

expected to be about 15%. Therefore, a peak i s expected allow subtraction of a r e s t of continuous

background.

For reactions (56) and (57 + 58) the conditions are equal except t h a t the

time window has to

be set between about 0.5

to

5 psec in

the

the case of

the

l a t t e r case. Though these signatures are not

as s t r i n g e n t as in

inverse 8-decays the combined background reduction by passive and a c t i v e a n t i s h i e l d , subtraction of background measured in the pulse pause in corresponding equal time windows and f i n a l l y subtraction of PIP-P

474

B o Zeitnitz

the

peak

both

from

total

the

This

comtinuous

cross

cross

higher

a

sections

sections

for

to

R

Using

{59)

tions

{eqo3)

neutral

can

and

be

an a c c u r a c y

{55}

and

be used

as

{57

sufficient

of

+ 58)

one

obtains

over

about will

to

determine

± 10%o The r a t i o

be m e a s u r e d w i t h

of much

with

=

o NC/

0+ 0

bidden

corresponding

of

assumption

energy

distribu-

universality

for

the

=

0°225

2/9

~

(51}

Ve+V ~

1+ 0

;

E = 12o71 MeV

v/ + p

L 2C* ( 1 2 ° 7 )

5z)

Ve

+

12C

->

Ve

+

"2C*

53)

v

+

+

:v/

+

I 2C* ( L 2 o 7 )

P

12C

mixing

P

this

this

case°

m~ ( M I ) )

~ =

(I2o7)

{54)

,Mould be a p u r e l y

~SGIN m o d e l °

in

rate

on u n i v e r s a l i t y °

1 2C +

P,

the

present

the

~ NC

÷

isospin in

the

test

+

v

Without

sensitive

interaction:

v

bo)

another

integrating

current R

is

should

accuracy° ratio

decay

rest

But

From

it (

is

known

Don 79

isoscalar

that

some

} ~e have

process isospin

(using

for-

mixing

the

known

#~

:

0o92×10 - 3 8

Ev-E X

[

o(~

+ 0 o 0 5 ~ ) 2 K2cm 2

(55)

theory°

Therefore~ tion

this

the level

cross

~2C* of

the

detected

in

Because be tire

detection

the

results

for

an e s t i m a t e

of

section

decays ~ith (12o7)

small

12o7

an u p p e r of

+

~ +

~ight

a very of

is

expected

8Be*(2o9)

output

large

the

y-rays

limit

of

mixing

will

the into

be

very

ratio

small°

In

3~ d e c a y

most

detector° be

cross this

addi-

via:

~ ~ + ~ + ~

scintillation

MeV

isospin

to

a 98% b r a n c h i n g

very

probably

cannot

Therefor,

difficult°

section state°

(55)

~ould

But be

posi= even

valuable

Low Energy Neutrino Physics

2o I n v e r s e

B-decay

As has been m e n t i o n e d im t h e

detector

trinOSo total

In

will

addition,

theory

up

to

another

test

nuclear

strength

(Oon 79~ for

several

the

from the

of

i~verse

the

50

for

NaVe

unified

Figures

14 and

imverse

This as

~-decay

reactions

for

energy

spectra

the will

model mp t o

be o f

interest

information well

as

relatively

15 show t h e

nuclei

and for

can

for

high

of

electrom of

be

used

far

of

the

extraction of

the

¢heckimg

excitation

results

meu=

energies

calculations

energy

s p e c t r u m and t h e o v e r a l l angu]ar distribution 12Co on It will be v e r y d i f f i c u l t to distinguish in

the

backward

measured

isotropicalo

performed

of

section

function

going

Therefore~

practically tarn~t

cress

8-decay

electrons

tiomo

already

measurements about

Oco 72}o expected

times

be used as d e t e c t i n g

and d i f f e r e n t i a l

the

475

imverse

from

angular

Recently ~-decay

those

first

of

going

distribution

~°Ar

in

forward

is

expected

calculations (Fur

82

have

~hich

direc-

also

may be

to

be

been

used

as

materia~o

E e - [MeV]

0

-oI

I0

20

/

/

30

/ \\

/

6~

V

×

45

'~0

Fig°

!4o

I

20

: Expected

energy

30

40

distribution

of

50 Ev [MeV] ve a t

the

SNS ( r e l a t i v e

units) 11 I~I:

: Cross Energy

section

for

Ve+L2C

distribution

The s c a l e on t h e full beam y e a r s o

of 7eft

+ e - + 12N { s c a l e

e= f r o m indicates

v +12C e

the

om t h e

ri ght)

+ e=+12 Ko

event

rate

for

two

476

B o Zeitnitz

i

I

I

1.4

16

1.2

14

1.0

12

A i

i

10

0.8

U

0.6

i

8

0

~i o

0.4,

0.2

0°

45 °

90 °

135°

180 °

E l e c t r o n Qng!e

Fig°

15o

Imverse angle~

~-decay

averaged :

scale

ZVo

COnCLUSIOnS

beamstop

of

the

will

provide

us

with

physics tures

energy in

large

new

field

of

tive

to

basic

conservation addition scattering)

region volume neutrino

high

up t o

can be o b s e r v e d

of

of

neutrinos at

of

these

proton

v~ve~

electron

current nuclear the

~ill

like

- charged

current

first

time°

be

mass

(eogo

the

nuclear

physics

sources

neutrinos reactions

accelerators

~ in

nuclear

pulsed

The m e a s u r e m e n t s the

for

function

pulsed

50 MeVo The use o f

physics°

clean

as a

SNS ~e s p e c t r u m ° right s c a l e : ve + ~ 0 A r

intensity

detectors

neutral

very

;

sources

properties

la~s~

some

new

sections

the

re+ L2 C

Left

The

cross

over

sigma-

will

opem

a

very

sensi-

differences°

interferemceo imelastic

In v

Low Energy Neutrino Physics

~o

Bar 83

REFEREMCES

BoCo B a r i s h ~ Workshop

Bil

77

Bee 84

Low Energy N e u t r i n o

(1983)

SoMo B i l e n k y

and Bo P o n t e c o r v o ~ Physo

AoBShm, T e s t s

of

gorkshop

o f Aachen

Physics~

PrOCo 3o LANPF I I

190

Oscillations~

Noriond

Bur 84

477

Reports

Lepton

41 ( 1 9 7 8 )

the standard

and N e u t r i n o

225:261

mode~

1984 and P r e p r i n t

Mixing

Proceedings

PITHA 8 4 / 1 3

of

the

University

(1984}

Ro Burman e t a~o~ LAMPF P r o p o s a l

NOo 754 (1982)

and p r i v a t e

communication Bur 83

Ro Burman e t with

Com 83

(1983)

and p r i v a t e

Textbook

Cambridge

CHARM C o l ~ a b o r a t i o n ~ Preprint

A search

University for

A study

at LANPF, R e p o r t

of

Don 79

To~o D o n ~ e ~ y

and RoDo P e c c e i ~

ToWo D o n n e l ~ y ,

Fei

FoVo F e i l i t z s c h ~

Erice

references

given

there

So F u r u i ~

Inelastic

Fur 82

A308 (1982) Kay 79

Bo Kayser~ and ~ e u t r a l

Erice

~ectures

e~ectron

Current

elastic

Effects

in

1-85

1984~ t h i s

lectures

neutrino

of muon meu:

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1983

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