yr09_lecture13_grinten

8/9/2019 yr09_lecture13_grinten

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measures in the distant past precision measurements: what do they provide?

precision experiments part of large facilities precision experiments with neutrons

Precision experiments

Electroweak precision experiments

Electroweak precision experiments

proton decay measurements

muon decay measurements

proton decay measurements

muon decay measurements

neutron decay measurementslifetime experimentcorrelation parameters between neutron

and decay products

neutron electric dipole moment experiments

neutron decay measurementslifetime experimentcorrelation parameters between neutron

and decay products

neutron electric dipole moment experiments

practical tools

scientific:test of theoretical models, existing laws

of physicsconfirm and/or constrain modelspotential to discover (interactions,

particles, ...)

practical tools

scientific:test of theoretical models, existing laws

of physicsconfirm and/or constrain modelspotential to discover (interactions,

particles, ...)


2/39

precision experiments: measurement tools

~ 3400 BC

~ 3400 BC

Giza pyramids

sides built on the basis of the cubit

to a precision of 0.05%!!!

Giza pyramids

sides built on the basis of the cubit

to a precision of 0.05%!!!

Royal cubit stick

Royal cubit stick

measures: a practical tool

define a length on the basis of a common feature

measures: a practical tool

define a length on the basis of a common feature

1 cubit

1 cubit


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precision experiments: measurements

measurements: to add to academic interests

deduce earth curvature by angle of sunlight

measurements: to add to academic interests

deduce earth curvature by angle of sunlight

250 BC - Eratosthenes:

In Syene ~5000 stadia south of Alexandria

sunlight shining directly down well shafts in Alexandria light measured to be at 7angle ~5000 360/7 = 252,000 stadia (of the order of

40,000 km) - (cf 40,030 km)


4/39

precision experiments: particle physics

Scientific precision experiments: testing the limits of our description

and understanding of nature

Scientific precision experiments: testing the limits of our description

and understanding of nature

particle physics:masses and lifetimes of particles

(quarks, leptons, hadrons, ...)matrix elements of transitions

(CKM, PMNS, nuclear trs, ...)forces and couplings in reaction

processes (GF, , ... )signals of rare events, breaking of

laws and symmetries, ...

particle physics:masses and lifetimes of particles

(quarks, leptons, hadrons, ...)matrix elements of transitions

(CKM, PMNS, nuclear trs, ...)forces and couplings in reaction

processes (GF, , ... )signals of rare events, breaking of

laws and symmetries, ...

goes hand-in-hand with ever more

precision calculations

goes hand-in-hand with ever more

precision calculations

proton lifetime

neutron lifetime (Vud )

neutron decay

neutrinoless -decay


5/39

precision experiments: proton decay

Standard Model describes the change of quark colour and flavour

and lepton conversion through gauge bosons g, W, Z0

Standard Model describes the change of quark colour and flavour

and lepton conversion through gauge bosons g, W, Z0

d

u

s

d

uu

d

u

e-

e

0

p

( Baryon number B and lepton number L conserved )

( Baryon number B and lepton number L conserved )

52TKGF=

2

2

2 W

WF

MgG =

decay rate as function of energy T, coupling constant G:

decay rate as function of energy T, coupling constant G:


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new allowed processes:

p 0 + e+

new allowed processes:

p 0 + e+

GUT mechanisms

GUT mechanisms

in models quarks and leptons incorporated into common families (e.g. e+ with d):

interaction with new gauge bosons (X, Y) masses MX ~ 10

15 GeV, coupling gU ~ 1/42

4

54

X

pU

M

Mg

d

u

u

u

u-

e+

p

0

{

}

X

u

u

u-

u

d

p{0

}

e

+

Y-

i

iLBLB

yrp 291 10=

yrep32

100 >+

( Baryon number B and lepton number L NOT conserved )

( Baryon number B and lepton number L NOT conserved )

into specific channel:

into specific channel:


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Super kamiokande: neutrino oscillation experiment

11,200 PMTs detecting e

and 50,000 tonnes of ultra-pure water, 1000m

underground in the Kamioka Mine

(100 km < L < 10,000 km)neutrino flavour states mix, neutrinos are massive


Super kamiokande: use data to look for proton decay events


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)%90(102.8/ 330 CLyrB ep >+

analyse all data to look for electron signals:

in the correct energy range total invariant mass per event determined in the correct momentum range from the correct part of detector

106 event triggers per day:

background from cosmic rays flashing PMTs radioactivities

p 0 + e+p 0 + e+

18816 surviving events:

precision measurement constraining GUTsprecision measurement constraining GUTs


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precision experiments: lepton g-2

1927 Dirac intrinsic angular momentum and magnetic momentof electron quantified

measurements of g factors pushed further development of QED

May and November 1947 electron g factor measurement different

from 2: g factor anomaly ae

Formulation of QED with first order radiative correction

2,2

2

==

=

gS

Sm

gq

)5(00119.02

2=

=

gae

00116.02

=

six orders of magnitude improvement in precision expts

and theoretical calculation


and theoretical calculation

testing the Standard Model to its limits, discovery of new

interaction beyond SM

testing the Standard Model to its limits, discovery of new

interaction beyond SM


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protons

target

pions muons

detectors

muon decay to electron


24 GeV proton focused on nickel target generates pions

pions decay to polarised muons and are injected in

storage ring

decay electrons emerge preferentially in direction ofmuon spin detect those electrons with high enough energy to be in

the direction of the muon motion

detecting a signal of the muon spin inforward directionsignal oscillates with spin precession frequency of muon

Muon g-2 experiment Brookhaven


11/39


Brookhaven National Lab: 3 GeV muons stored in 14 m dia. ring in 1.45 T fieldBrookhaven National Lab: 3 GeV muons stored in 14 m dia. ring in 1.45 T field

mc

eBc =

2

2

22

=

===

ga

mceBag ccSD

mc

eB

mc

eBgS )1(2 +=

muon has orbital motion in magnetic field

at cyclotron frequency C spin has precession frequency S

relative precession of S with respect to velocity

of muon: S- C

direct relationship between D

and adirect relationship between D and a


12/39



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first signs of deviation from 2.6

Standard Model description?

not quite... error in experimental analysis code

first signs of deviation from 2.6

Standard Model description?

not quite... error in experimental analysis code

11659100 11659150 11659200 116592

S

M1010a

Experiment

March 2001 PRL


opening a window to beyond SM physics phenomena


opening a window to beyond SM physics phenomena


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precision experiments: neutron decay

neutron beta decay experiment:

Standard Model precision measurements

precision tests on unitarity of the CKM matrix cosmological significance

1222=++ ubusud VVV

keVepn e 782+++

+++

++

EE

ppD

E

pB

E

pAP

EE

ppa

E

mbdW

e

e

e

en

e

e

e

e

1

neutron decay probability, function of particlesmomenta, spin, correlation coefficients


15/39

precision experiments: neutron decay parameters

correlation electron and

anti-neutrino momentum

correlation electron and

anti-neutrino momentum

neutron beta decay experiment:

correlation coefficients between particles spin and momenta

coupling constants

2

2

31

1

+

=a

( )231

12

+

+=A

correlation electron

momentum neutron spin

correlation electron


V

A

G

G=

45

732

cmK

e

= FudV GVG =( )22 31

+

=Vn

nGf

K

free neutron decayfree neutron decay

from muon decayfrom muon decay

ratio axial-vector /

vector coupling constant

ratio axial-vector /

vector coupling constant


16/39

the A experiment: correlation electron


the A experiment: correlation electronmomentum neutron spin

polarised neutrons electron detection with respect to

neutron spin direction

precision experiments: neutron correlation parameter experiments

measurement of measurement of


17/39

Spectra for both spin states

B. Maerkisch, PERKEO III : Neutron Decay Measurements

2002: result: A = -0.1189(8) =-1.2739(19)

2006: result: A = -0.1198(5) =-1.2762(13)

testing the CKM matrix of Standard Modeltesting the CKM matrix of Standard Model


18/39


neutrons (unpolarised) proton detection, energy measurement

the a experiment: correlation electron-neutrino momentum

proton energy spectrum depends on a

the a experiment: correlation electron-neutrino momentum

proton energy spectrum depends on a

n

p

e-e

np

e-

eneutrons energy ~ meV, energy release ~MeVneutrons energy ~ meV, energy release ~MeV

proton energy depends on angle between

electron and anti-neutrino

proton energy depends on angle between

electron and anti-neutrino

measurement of measurement of


19/39

Penning trap proton detection, energy measurement

cold neutrons pass through volume

between two electrodes, kept in a

magnetic field

cold neutrons pass through volume

between two electrodes, kept in a

magnetic field

decay protons trapped and orbit

around magnetic field lines

decay protons trapped and orbit

around magnetic field lines

open trap by lowering voltage on

gate electrode

open trap by lowering voltage on

gate electrode

repeat sequence for mirror voltages

ranging 0V to 800 V

repeat sequence for mirror voltages

ranging 0V to 800 V

measurement of proton energy spectrummeasurement of proton energy spectrum


i i i i i


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a = -0.1054 0.0055, = 1.271 0.018a = -0.1054 0.0055, = 1.271 0.018

measurement of decay proton integrated

energy spectrum

measurement of decay proton integrated

energy spectrum

fit curve to energy spectrum as function

of a:

fit curve to energy spectrum as function

of a:no competition for A measurement

but independent method

no competition for A measurement

but independent method

i i i lif i i


21/39

precision experiments: neutron lifetime experiments

neutrons (of cold or ultra-cold energy)

detect decay products or detect surviving neutrons

the neutron lifetime experiment:the neutron lifetime experiment: precision tests on unitarity of

the CKM matrix cosmological significance

experiment at NIST - USA:

beam of cold neutrons neutrons pass through penning trap decay protons recorded

i i i t t lif ti i t


22/39


superconducting magnet 3Tsuperconducting magnet 3T

solid-state

charged particle detector

solid-state

charged particle detector

high voltage (27 kV) cage for

proton acceleration

high voltage (27 kV) cage for

proton acceleration

incoming neutron beamincoming neutron beam

the neutron lifetime experiment:

NIST


NIST



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n = 885.5 3.4 s.

n= 885.5 3.4 s.

need to know neutron flux to very high precision

need to know trap volume to high accuracy

need to know efficiency of detectors to high accuracy

need to collect many events for statistical precision


= (39.30 0.10) g/cm26Li density = (941.0 1.3) b absorption cross section at 2200 m/s /4 = 0.004196 0.1% fractional solid angle detector


NIST


NIST

neutron flux monitor: n +

6

Li

3

H + neutron flux monitor: n + 6Li3H +



24/39


experiment at ILL:

ultra-cold neutrons guided into storage chambers seal chamber and store neutrons for a period T open chamber to neutron detector and count remaining neutrons repeat cycle for different storage periods T


stored ultra-cold neutrons



UCNUCN

detectordetector

two storage chamberconfigurations: different surface

exposure

two storage chamber

configurations: different surface

exposure



25/39


need to know neutron flux stability

need to know neutron loss mechanism during storage

need to collect many events for statistical accuracy

different detection efficiencies for two

chamber configurations 0.36 s uncertainty in shape of chamber statistical uncertainty







26/39


experiment at ILL:

ultra-cold neutrons guided into storage chambers seal chamber and store neutrons for a period T

open chamber to neutron detector and count remaining neutrons repeat cycle for different storage periods T and different energies





precision e periments: ne tron lifetime e periments


27/39




28/39





latest result too far off to be included in

average, now additional measurement:

polarised ultra-cold neutrons guided

into storage chambers

seal chamber and store neutrons for a

period T

open chamber to neutron detector andcount remaining neutrons repeat cycle for different storage

periods T




29/39


measurements / error bars incompatible, to be continuedmeasurements / error bars incompatible, to be continued

V from neutron and nuclear beta decay


30/39

Vud from neutron and nuclear beta decay

=GA/G

V

Perkeo result:

A0 = -0.1189(7)

= -1.2739(19)

n = (885.7 0.7) sworld average

n = (878.5 0.7st 0.3syst ) sGravitrap result

( )22

31

9.17.4908

+

=

n

ud

sV

precision experiments: neutron electric dipole moment


31/39

P & T violation

CPT conservation CP violation

Electric Dipole Moment:

neutron is electrically neutral

If average positions of positive and

negative charges do not coincide:

EDM dn

-

T reversal

dn S

electric dipole moment dnspin S

+

- dn S

+

-

P transform.dn S

+

-dn S

-

+

precision experiments: neutron electric dipole moment

CP violation in Standard Model generates very small neutron EDM

Beyond the Standard Model contributions tend to be much bigger

neutron a very good system to look for CP violation beyond the Standard Model

nEDM: measurement principle


32/39

Compare the precession frequency for parallel fields:

= E/h = [-2B0 n - 2Edn]/h

to the precession frequency for anti-parallel fields

= E/h = [-2B0 n + 2Edn]/h

The difference is proportional to dn and E:

h( - ) = 4E dn

Experiments:

Measurement of Larmor precessionfrequency of polarised neutrons in a

magnetic & electric field

NET

dn

2

)(

=

: polarisation productE: electric field

T: observation time

N: number of neutrons




33/39

4.

3.

2.

1.

Freeprecession

...

Apply /2spin

flip pulse...

Spin up

neutron...

Second /2spin

flip pulse.

29.7 29.8 29.9 30.0 30.1

10000

12000

14000

16000

18000

20000

22000

24000Ramsey Resonance Curve

working pointsresonance frequency

1/Ts

neutronsp

inupcount

applied frequency [Hz]


nEDM at ILL: scheme used


34/39

NS

Four-layer mu-metal shield High voltage lead

Quartz insulating

cylinder

Coil for 10 mG

magnetic field

UpperelectrodeMain storage cell

Hg u.v.

lamp

PMT to

detect Hg

u.v. lightVacuum wall

Mercury

prepolarising

cell

Hg u.v. lampRF coil to flip spins

Magnet

UCN polarising foil

UCN guide

changeover

Ultracold

neutrons

(UCN)

UCN detector

nEDM at ILL: scheme used

nEDM at ILL: set-up room temperature experiment


35/39

nEDM at ILL: set-up room temperature experiment

nEDM at ILL: normalised frequency measurement


36/39

0 5 10 15 20

29.9260

29.9265

29.9270

29.9275

29.9280

29.9285

29.9290

29.9295

10-10

T

Neutronresonantfrequency(Hz)

Run duration (hours)

7.7882

7.7884

7.7886

7.7888

7.7890

nEDM at ILL: normalised frequency measurement

nEDM at ILL: performance room temperature experiment


37/39

1300 1400 1500 1600 1700 1800 1900

-60

-40

-20

0

20

40

60

80

100

neutronEDM[

10-

25

ec

m]

run number

ecmdn26103


38/39

-e

+e

1cm

dn = 1 e cm

10-19

10-20

10-21

10-22

10-23

10-24

10-25

10-26

10-27

10-28

1960 1980 2000year ofpublication

Experiment Theory

10-19

10-20

10-21

10-22

10-23

10-24

10-25

10-26

10-27

10-28

10-29

10-30

10-31

10-32

10-33

10-34

10-35

NeutronEDM

upp

erlimit[ e

cm]

Progress at ~ order of magnitude per decadeStandard Model out of reach

Severe constraints on e.g. Super Symmetry

|dn|< 3 x 10-26 e cm

nEDM: experiment vs theory

precision experiments


39/39

precision experiments

test of theoretical models, existing

laws of physicsconfirm and/or constrain modelspotential to discover (interactions,

particles, ...)

test of theoretical models, existing

laws of physicsconfirm and/or constrain modelspotential to discover (interactions,

particles, ...)

precision measurements examples

neutron electric dipole moment experimentsneutron lifetime & correlation experimentanomalous g-factor (g-2)decay experiments (p, double beta)

precision measurements examplesneutron electric dipole moment experimentsneutron lifetime & correlation experimentanomalous g-factor (g-2)decay experiments (p, double beta)

mostly indirect measurements

a very powerful tool to probe theories

and their limits

li i t f h i

mostly indirect measurements

a very powerful tool to probe theories

and their limits

li i t f h i

we have seen:we have seen:

these can:these can:

current precision

experiments:

current precision

experiments:

yr09_lecture13_grinten

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