dark matter and the drift experiment - temple universitycmartoff/teaching/genl_dm.pdfthe dark matter...

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)