Goldsmiths Particle Physics Summer School 21 st July 2009 Outline 1 Why MICE a brief overview of the Standard Model n eutrino m asses and oscillations the neutrino factory and muon cooling ID: 631778
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Slide1
A Student on MICE
Adam Dobbs, Imperial CollegeGoldsmith’s Particle Physics Summer School21st July 2009Slide2
Outline
1. Why MICE? - a brief overview of the Standard Model -
n
eutrino
masses and oscillations - the neutrino factory and muon coolingWhat is MICE? - muon ionisation cooling – what we hope to show - MICE design - scheduleLife on MICE (what I do) - the office - accelerator beam loss and MICE particle rateConclusion - where we’ve been - why I like what I do
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A Student on MICE, A DobbsSlide3
1. Why MICE?
Introduction to the Standard ModelNeutrino masses and mixingsThe Neutrino Factory
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3
A Student on MICE, A DobbsSlide4
The Standard Model of Particle Physics
A mathematical model of matter and forces at the most fundamental level currently known (with the notable exception of gravity)Extraordinarily good agreement with experimentHeld good for the last 40 years... but not a “final theory”21/07/2009A Student on MICE, A Dobbs
4Slide5
“Fundamental” Particles21/07/2009
A Student on MICE, A Dobbs5
u
Q = +2/3
m = 2.4 MeV
s = 1/2
c
Q = +2/3
m = 1.27
GeV
s = 1/2
t
Q = +2/3
m = 171.2
GeV
s = 1/2
d
Q = -1/3
m = 4.8
MeV
s = 1/2
s
Q = -1/3
m = 104
MeV
s = 1/2
b
Q = -1/3
m = 4.2GeV
s = 1/2
τ
Q = -1
m = 1.777 GeV
s = 1/2
ν
e
Q = 0
m < 2.2
eV
s = 1/2
ν
µ
Q = 0
m < 0.17
MeV
s = 1/2
ν
τ
Q = 0
m < 15.5
MeV
s = 1/2
µ
Q = -1
m = 105.7
MeV
s = 1/2
e
Q = -1
m = 0.511
MeV
s = 1/2
Quarks
Leptons
Fermions
γ
Q = 0
m = 0
s = 1
z
0
Q = 0
m = 91.2
GeV
s = 1
w
±
Q = ±1
m = 80.4
GeV
s = 1
H
Q = 0
m
> 112
GeV
s = 0
g
Q = 0
m = 0
s = 1
Bosons
EM
Weak
Strong
Higgs
G
Q = 0
m = 0
s = 2
GravitySlide6
Interactions
21/07/2009A Student on MICE, A Dobbs6Image courtesy of Wikimedia CommonsSlide7
Beyond the SM: Neutrino Mass and Mixing21/07/2009
A Student on MICE, A Dobbs7SM had assumed neutrinos to have a zero massFirst evidence against this came in 1960s when Ray Davis at the Homestake mine experiment observed a deficit in the number of solar neutrinos detected from that predicted by the standard solar model → “The Solar Neutrino Problem”Slide8
The Plot Thickens
Missing neutrinos and the mysterious appearance of neutrinos were subsequently noticed in neutrinos generated by cosmic rays hitting the atmosphere (Super Kamiokande, SNO), in nuclear reactors (KamLAND) and in particle accelerators (K2K)What is the cause?21/07/2009A Student on MICE, A Dobbs
8
Inside Super Kamiokande, a 50,000 ton water Cherenkov detector based in the
Mozumi Mine, JapanSlide9
Solution: Neutrino Oscillations21/07/2009
A Student on MICE, A Dobbs9All the information about a quantum system is held in a mathematical entity known as the wavefunction, ψNeutrino mass (eigen
)states are
not
the same as neutrino weak flavour (eigen)states......but they are related...... its a questions of hats Slide10
The Mixing Matrix or How the hats are related
21/07/2009A Student on MICE, A Dobbs10
where
,
and are CP violating phases
... yes ... lets not think too hard about this... See “
Where have all the neutrinos gone” on Thursday
The Point
: the neutrino weak force states are a combination of the neutrino mass
states
and we want to know exactly how by measuring the four parameters Slide11
Oscillations Graphically: Flavour = combination of masses
21/07/2009A Student on MICE, A Dobbs11
=
+
Consider 2 neutrino case for simplicity. When a neutrino has just been formed in a weak interaction the neutrino is in a pure single flavour state, which is a combination of two mass states:Slide12
Probing Oscillations: The Neutrino Factory
The Neutrino Factory is a proposed next generation high intensity neutrino sourceAllow us to study the mixing parameters to greater precisionOnly one of various contenders for a next generation neutrino source... but probably the best (but probably the most difficult to realise too)21/07/2009A Student on MICE, A Dobbs
12Slide13
How does it work?Get a beam of protons and zap them into a target...
... which generates pions...... which will then decay into muons...21/07/2009A Student on MICE, A Dobbs
13
... which are put into a big storage ring until...
... the muons decay to neutrinos!
Feynman diagram for muon decaySlide14
What does it look like?
H
−
LEBT
RFQ
Chopper
H
−
Linac
Stripping
Foil
Synchrotrons
FFAG I
(3-8GeV)
FFAG II
(8-20GeV)
FFAG III
(20-50GeV)
Proton Beam Dump
Solenoidal Decay Channel
(in which
pions
decay to
muons
)
RF Phase Rotation
Muon Cooling Ring
Solenoidal Muon
Linac
Target
(produces
pions
from
protons
)
Near Detector
R109
To Far Detector 2
To Far Detector 1
Muon Decay Ring
(
muons
decay to
neutrinos
)
[below
ground ]
21/07/2009
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A Student on MICE, A DobbsSlide15
OK, but what does all this have to do with small rodents?
Once the muon beam has been generated from the pions it needs to be cooled, sort of shrunk, so that it will fit into the other NF components further downstream, before decaying into neutrinosCooling becomes even more necessary when considering a future muon colliderConventional beam cooling using EM fields does not work because of the short muon life timeEnter MICE...
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A Student on MICE, A Dobbs
15Slide16
2. What is MICE?
Muon Ionisation CoolingMICE layoutMICE Schedule
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A Little Accelerator Physics
MICE stands for the International Muon Ionisation Cooling Experiment“Cooling” refers to the phase space compression or emittance reduction of the muon beam
Phase space here refers to the normal position space
x, y, z
and the momentum space x’, y’, z’ of the beam of particlesThe emittance of a beam refers to how much volume a beam occupies in this phase space21/07/2009A Student on MICE, A Dobbs17Slide18
Emittance21/07/2009
A Student on MICE, A Dobbs18
x
x’
a
b
- the slope of the particle trajectory relative to the axis
z
x
y
Beam
Real Space
Part of Phase SpaceSlide19
Ionisation Cooling
Pass the beam through an absorber e.g. liquid hydrogen, lithium hydrideThe particle beam ionises the medium, the beam particles losing energy and momentum in all directionsRe-accelerate the beam in the beamline direction (z) only, using a radio frequency electric fieldMuon ionisation cooling has never been demonstrated before... but concept is simple
21/07/2009
A Student on MICE, A Dobbs
19LiH2vv
RF
vSlide20
MICE GoalsProduce a functional Neutrino Factory cooling channel (the factory itself will require multiple channels). Specifically:
Produce an input muon beam of momentum between 140 to 240 MeV / c , and a tuneable emittance between 1 to 12 π mm radMeasure the emittance before and after cooling to a precision of 1 part in 1000Produce an approximately 10% cooling effect
21/07/2009
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20Slide21
MICE Home
Based in the UK at Rutherford Appleton Laboratory, DidcotUses the ISIS 800MeV synchrotron accelerator as a proton sourcePossible site for the Neutrino Factory21/07/2009A Student on MICE, A Dobbs
21Slide22
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ISIS
MICE
MICE LayoutMICE Target
Pion
capture with Q1-3
D1
D2
Q4-6
Q7-9
DS
Tracker
CKOV A, B
D = Dipole bending magnet Q = Quadrupole magnet
DS = Decay solenoid GVA1 = Scintillator counter
CKOV = Cherenkov detector
GVA1
Dipoles → bend the beam
Quadrupoles → focus the beamSlide23
What it looks like21/07/2009
A Student on MICE, A Dobbs23Slide24
The Finished Product21/07/2009
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MICE Aspirational Schedule
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3. Life on MICE
The OfficeBeam Loss
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A Student on MICE, A DobbsSlide27
The Office21/07/2009
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Arrive
Sit here
Use theseRead this
Scribble a bit
Look for some interesting weather
Go homeSlide28
MICE in ISIS
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MICE is an unique experiment on ISIS – the only one capable of disrupting the synchrotron
The MICE target causes a measure of disruption to the ISIS beam and thus a possible increase in the radioactivity present
MICEEveryone elseSlide29
Beam Loss and Particle RateIn fact, the more
beam loss we produce in ISIS, the more particles we get down the MICE beamline – something we badly need (our current particle rate is far too low) → a tension of needs existsAs a result beam loss in ISIS must be monitored and studied in relation to the MICE targetPart of what I do21/07/2009A Student on MICE, A Dobbs
29Slide30
Beam Loss Simulation: ORBIT
ORBIT = Objective Ring Beam Injection & Tracking
Particle tracking code used by ISIS to simulate their machine
Built under C++ and
SuperCodeFreeIt has issues... 21/07/2009A Student on MICE, A Dobbs30Slide31
Short-Fat Target21/07/2009
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Long-Thin Target21/07/2009
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Cylindrical Target21/07/2009
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Beam Loss Data Analysis39 ionisation chamber beam loss monitors positioned around the ISIS ring
Noisy data – use averages to extract signalLook for affects solely due to the MICE target - remove background signal due to normal ISIS beam lossTarget position and dip time also recorded21/07/2009A Student on MICE, A Dobbs34Slide35
The ISIS Spill and Beam Loss
21/07/2009A Student on MICE, A Dobbs35Beam Intensity (V)
Target Position (V)
Total Beam Loss (V)
Spill with MICE target presentSpills without MICE target presentSlide36
Beam Loss and 3rd Order Polynomial Fit
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Total Beam Loss (V)
3
rd order polynomial fit to MICE specific beam lossLosses due to beam injectionLosses due to beam extractionSlide37
Data reduction: 1 point per dip21/07/2009
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Its Useful Too: Target Melt Event21/07/2009
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8mm
Ti Melting Point = 1660 0CSlide39
Beam Loss Vs Particle Rate21/07/2009
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4. Conclusion
Where we’ve beenWhy I like what I do
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A Student on MICE, A DobbsSlide41
Where We’ve BeenIntroduction to particle physics and the Standard Model
Neutrino mass and oscillationsThe Neutrino Factory to further investigate oscillationsMICE to demonstrate cooling needed for a NFMICE – what, whenMICE and ISIS beam loss issues21/07/2009A Student on MICE, A Dobbs
41Slide42
Why I like what I do“Fill the earth and subdue it” - Genesis → Physics
Physics is challenging, beautiful, useful and even funIf you still don’t like it, a physics degree equips you for many professions... and you don’t have to get up too early in the mornings21/07/2009A Student on MICE, A Dobbs42Slide43
Thank you!Slide44
Masses = Combination of flavours21/07/2009
A Student on MICE, A Dobbs44
=
+
=+Flavour 1 components constructively interfere, flavour 2 components destructively, hence the neutrino is a pure flavour 1 stateSlide45
Different masses travel at different speeds
21/07/2009A Student on MICE, A Dobbs45
Because the different mass states travel at different speeds, the phases between the two changes → flavour 1 components no longer interfere purely constructively, flavour 2 components no longer interfere purely destructively.Slide46
Relative amounts of each flavour component change with time
21/07/2009A Student on MICE, A Dobbs46
So our neutrino now has components of both flavour 1 and flavour 2. The amplitude of the wave for each flavour dictates the probabilty that when the neutrino is detected it will be observed as that flavour. The mixings angles
dictate how these amplitudes vary over time.Slide47
KamLAND: Observation of Oscillation
21/07/2009A Student on MICE, A Dobbs47