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Dar
k M
atte
r an
d th
e D
RIF
T
Exp
erim
ent
�
Wha
t is
Dar
k M
atte
r?
�
Why
do
we
belie
ve
in it
?�
How
sha
ll w
e id
entif
y it?
C. J
. Mar
toff,
Pro
fess
or o
f Phy
sics
Phy
sics
C05
6, A
stro
nom
yT
empl
e U
nive
rsity
Spr
ing
'03
Wha
t is
Dar
k M
atte
r?
Dar
k=
not l
umin
ous
(like
sta
rs)
= i
nvis
ible
Mat
ter
=m
ass
=
grav
ityso
urce
Wha
t's th
e E
vide
nce
for
Dar
k M
atte
r?
Kep
ler's
Law
allo
ws
us
to
"see
" di
stan
t mas
s (e
ven
invi
sibl
e m
ass)
R
3 =
T2
(M1
+ M
2)
Thi
s w
orks
per
fect
ly
fo
r so
lar
syst
em, J
ovia
n m
oons
,
bina
ry s
tars
,... a
nyth
ing sm
all
to J
upite
r
Ano
ther
Way
to L
ook
at K
eple
r's L
aw V
eloc
ity is
eas
ier
to m
easu
re th
an o
rbita
l pe
riod
(via
spe
ctro
scop
y an
d D
oppl
er
shift
), e
spec
ially
for
very
dis
tant
obj
ects
We
can
writ
e v
= 2π
R/T
for
orbi
ting
obje
ct
The
n K
eple
r's L
aw c
an b
e re
writ
ten
usin
g al
gebr
a:
R3 =
T2 (
M1+
M2)
⇒ (
R/T
)2 =
(1/R
)(M
1+M
2)
(div
ide
both
sid
es b
y T2 , th
en b
y R
)
⇒
(2π)
2 (R
/T)2
= (
1/R
)(M
1+M
2)(2
π)2
(m
ultip
ly b
oth
side
s by
(2π)
2 )
Fin
ally
get
v 2 =
(1/
R)
• (
M 1+
M 2)
(2π)
2
Kep
ler's
Law
on
the
Gra
nd S
cale
Gal
axie
s ar
e a
mill
ion
times
bi
gger
than
sol
ar s
yste
m (
.01
light
yea
r vs
. 10,
000
light
ye
ar)
Gal
axie
s ha
ve u
p to
a m
illio
n m
illio
n (1
012 )
tim
es m
ore
mas
s th
an th
e so
lar
syst
em
It is
inte
rest
ing
to a
sk, d
oes
Kep
ler's
law
stil
l wor
k fo
r ga
laxi
es?
IT D
OE
SN
'T !!
Mea
sure
d "R
otat
ion
Cur
ve"
for
a ga
laxy
Wha
t doe
s K
eple
r La
w v
iola
tion
(?)
Mea
n?T
he v
eloc
ity is
muc
h to
o la
rge fo
r ob
ject
s fa
r ou
tsid
e th
e vi
sibl
e pa
rts
of th
e ga
laxy
!
The
who
le sh
ape o
f the
gra
ph is
wro
ng!
To
expl
ain
this
, eith
er:
Kep
ler
(and
New
ton)
law
s fa
il fo
r la
rge
syst
ems
O
R
The
vis
ible
par
ts o
f gal
axie
s lie
abo
ut
whe
re th
e m
ass is
AN
D h
ow
muc
h of
it th
ere
is !
A C
lue
The
ris
ing
part
of t
he
rota
tion
curv
e is
NO
T
unex
pect
ed.
Thi
s pa
rt o
f the
cur
ve is
insi
deth
e vi
sibl
e pa
rt o
f the
gal
axy
(as
if a
plan
et o
rbite
d in
side
the
Sun
).
Kep
ler's
Law
exp
lain
s it
reas
onab
lyw
ell w
hen
you
do a
ll th
e m
ath.
Just
Wha
t is
Mea
sure
d fo
r a
Rot
atio
n C
urve
Obj
ects
out
to r 0
are
with
in th
e vi
sibl
e m
ass
dist
ribut
ion;
thes
e gi
ve th
e in
itial
ris
ing
part
of t
he
v2 v
s R
cur
ve, a
gree
ing
qual
itativ
ely
with
Kep
ler.
Obj
ects
bey
ond
r 0 ar
e ou
tsid
e vi
sibl
e m
ass;
thei
r v2 vs
R c
urve
sh
ould
fall
as 1
/R. It
doe
sn't.
Any
how
the
tota
l mas
s in
dica
ted
by th
e cu
rve
is muc
h to
o la
rge.
A la
rge
"hal
o" o
f uns
een
mas
s w
ould
exp
lain
all
this
.
r 0.
.
.
..
..
.
. ..
. ...
.
..
. .
.
... .
.
..
..
.
. .
.
.
Dar
k M
atte
r H
alo
"See
ing"
the
Dar
k M
atte
r D
irect
ly
Rot
atio
n cu
rves
onl
y sh
ow e
xist
ence
of D
ark
Mat
ter
indi
rect
ly
To
be s
ure
it ex
ists
, we
wan
t to
dete
ct th
e st
uff i
tsel
f, no
t jus
t its
gr
avita
tiona
l inf
luen
ce a
nd a
ppar
ent i
nvis
ibili
ty
We
mus
t kno
w (
or h
ave
a gu
ess)
wha
t the
Dar
k M
atte
r is
mad
e of
in
ord
er to
pla
n ho
w to
det
ect i
t
Thi
s is
whe
re th
eoris
ts c
ome
in h
andy
It Is
Wha
t It I
s...B
ut It
Isn'
t Nor
mal
The
theo
ries
of "w
hat i
s th
e D
ark
Mat
ter"
are
bey
ond
the
scop
e of
this
talk
(m
aybe
late
r in
ch
apte
rs o
n C
osm
olog
y).
How
ever
, the
re a
re v
ery
good
re
ason
s to
bel
ieve
:
It IS
NO
T no
rmal
mat
ter
(pro
tons
+ne
utro
ns+
elec
tron
s)
It IS
a "
gas"
of W
eakl
y In
tera
ctin
g M
assi
ve P
artic
les
(WIM
PS
) le
ft ov
er fr
om th
e B
ig B
ang.
Dire
ct D
etec
tion
of W
IMP
s
If W
IMP
s ex
ist a
nd m
ake
up
the
Dar
k M
atte
r, th
ey w
ill
scat
ter
from
ord
inar
y m
atte
r in
a
dete
ctor
.
The
det
ecto
r at
oms
will
rec
oil;
"sta
ndar
d" n
ucle
ar r
adia
tion
dete
ctor
s ca
n de
tect
thes
e
Iden
tifyi
ng a
WIM
P s
igna
l ag
ains
t ord
inar
y ra
dioa
ctiv
e ba
ckgr
ound
s is
VE
RY
di
fficu
lt. (
Tha
t's w
hy w
e w
ork
in a
dee
p m
ine.
)
Wha
t is
the
WIM
P S
igna
ture
?
(The
re's
that
cra
zy p
ictu
re a
gain
!)
WIM
Ps
have
a d
istin
ctiv
e si
gnat
ure
beca
use
of
the
clou
d-co
llaps
es-t
o-di
sk p
heno
men
on
disc
over
ed b
y La
plac
e, s
tudy
ing
form
atio
n of
S
olar
Sys
tem
Dur
ing
gala
xy fo
rmat
ion,
ord
inar
y m
atte
r cl
oud
colla
pses
in s
ize
and s
pins
fast
er d
ue to
co
nser
vatio
n of
ene
rgy
and
angu
lar
mom
entu
m
WIM
PS
are
Wea
kly
Inte
ract
ing-
they
can
not
easi
ly lo
se e
nerg
y⇒ W
IMP
clo
ud c
anno
t co
llaps
e- it
sta
ys larg
e (c
onsi
sten
t with
rot
atio
n cu
rves
) an
d sph
eric
al an
d non
-rot
atin
g
The
Ear
th a
nd S
olar
Sys
tem
rot
ate
with
the
gala
xy. T
his
give
s di
stin
ctiv
e di
rect
iona
l si
gnat
ures
for
WIM
P s
catte
ring
!
Dire
ctio
n-S
ensi
tive
WIM
P D
etec
tion
with
the
DR
IFT
Det
ecto
rT
echn
ical
dis
cuss
ion
of
dire
ctio
n-se
nsiti
ve n
ucle
ar
radi
atio
n de
tect
ors
is b
eyon
d th
e sc
ope
of th
is ta
lk
I inv
ente
d th
e D
RIF
T c
once
pt
(Neg
ativ
e Io
n T
PC
) to
det
ect
WIM
P d
irect
iona
l sig
natu
re
afte
r ab
out 7
yea
rs o
f wor
k on
ot
her
met
hods
It ca
n de
term
ine
the
dire
ctio
n of
ver
y lo
w e
nerg
y re
coil
atom
s w
ith a
ccep
tabl
e ac
cura
cy, s
ize,
and
pow
er
cons
umpt
ion
for
min
e la
bs.
For
tech
nica
l inf
o on
DR
IFT
/NIT
PC
:ht
tp://
eucl
id.m
ath.
tem
ple.
edu/
~m
arto
ff/D
RIF
T/ta
lks
DR
IFT
is H
untin
g W
IMP
s N
ow
Ano
ther
thre
e ye
ars
wor
k w
ith
colla
bora
tors
(O
ccid
enta
l C
olle
ge, U
.K. D
ark
Mat
ter
Col
labo
ratio
n) a
nd ~
$1M
(U
.S. N
atio
nal S
cien
ce
Fou
ndat
ion,
U.K
. PP
AR
C)
led
to a
rea
l WIM
P d
etec
tor
deep
un
derg
roun
d. T
his
is D
RIF
T.
Run
ning
for
a ye
ar a
nd a
hal
f, st
ill le
arni
ng a
bout
the
dete
ctor
- but
no
WIM
Ps
yet.
DR
IFT
Dat
a Thi
s is
a b
ackg
roun
d al
pha-
part
icle
tr
ack
from
rad
ioac
tivity
in v
acuu
m
vess
el.
11,7
71 a
tom
s of
DR
IFT
gas
ioni
zed
App
rox.
220
,000
ele
ctro
n vo
lts o
f en
ergy
dep
osite
d
Tra
ck le
ngth
gre
ater
than
25
mm
Eas
y to
tell
it is
not
a W
IMP
DR
IFT
Dat
a Thi
s is
a n
eutr
on r
ecoi
l tra
ck
We
prod
uce
thes
e w
ith a
neu
tron
ra
dioa
ctiv
e so
urce
for
calib
ratio
n
Thi
s is
EX
AC
TLY
wha
t a W
IMP
eve
nt
wou
ld lo
ok li
ke (
exce
pt th
e di
rect
iona
l si
gnat
ure)
Abo
ut 2
000
DR
IFT
gas
ato
ms
ioni
zed
Tra
ck le
ngth
less
than
4 m
m
Abo
ut 1
00,0
00 e
V o
f ene
rgy
depo
site
d
We
don'
t see
thes
e w
hen
the
neut
ron
sour
ce is
take
n aw
ay !
DR
IFT
Dat
a Thi
s is
ano
ther
kin
d of
cal
ibra
tion
even
t, pr
oduc
ed b
y an
x-r
ay
radi
oact
ive
sour
ce
300
DR
IFT
gas
ato
ms
wer
e io
nize
d
5,90
0 eV
of e
nerg
y de
posi
ted
Tw
o w
ires
repo
rt-
the
neig
hbor
s ar
e de
ad q
uiet
The
se w
ires
are
2 m
m a
part
(~
1/16
inch
) an
d th
ere
are
1024
of
them
in D
RIF
T (
and
1024
am
plifi
ers,
102
4 w
avef
orm
re
cord
ers.
.. and
one
LIN
UX
co
mpu
ter
to h
andl
e it
all!)
DR
IFT
Dat
a A
cqui
sitio
n (T
empl
e's
Job)