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2015 Sambamurti Lecture: Xin Qian 1
Seeking the Origin of Asymmetry
Xin Qian
BNL
2015 Sambamurti Lecture: Xin Qian 2
Outline• The Big Question:
– Why is there much more matter than anti-matter in our universe?
– Is neutrino the key to this question?
• The Overall Strategy: – Neutrino vs. Antineutrino oscillations– Will there be a signal?
– Will the detector technology be viable?
• The Experimental Design and Future Challenges
2015 Sambamurti Lecture: Xin Qian 3
Where is all the anti-matter?
10
10
6.0 0.1 10 (BBN):
6.0 0.07 10 (CMB)baryonN
N
4
CP Violation: Asymmetry between Matter and Anti-matter
CP violation physics laws governing the interaction of matter are different from those governing anti-matter
Parity (P):
Charge (C):
Time (T):
x x
y y
z z
q q
t t
5
Is there CP violation (CPV) in the Standard Model of Particle Physics?
• Yes, CPV exists in the quark sector, but not enough to explain the observed asymmetry
• What about the lepton (neutrino) sector?
Interaction Mediators RelativeStrength
Range (m)
Strong g 1038 10-15
E&M γ 1036 ∞
Weak W, Z 1025 10-18
Gravitation gravitons 1 ∞
10
10
6.0 0.1 10 (BBN):
6.0 0.07 10 (CMB)baryonN
N
2015 Sambamurti Lecture: Xin Qian 6
Outline• The Big Question:
– Why is there much more matter than anti-matter in our universe?
– Is neutrino the key to this question?
• The Overall Strategy: – Neutrino vs. Antineutrino oscillations– Will there be a signal?
– Will the detector technology be viable?
• The Experimental Design and Future Challenges
2015 Sambamurti Lecture: Xin Qian 7
Some Facts about the Neutrino • Neutrinos interact through weak interaction
– It takes a wall thicker than our galaxy to stop a neutrino
• Neutrinos have non-zero mass– Physics beyond the standard model
• The smallness of neutrino mass also suggests a new mechanism of the mass generation
Energy Budget of the Universe
Dark Energy ~73%
Dark Matter ~23%
Visible Matter ~4%
Neutrino >~ 0.3%
2015 Sambamurti Lecture: Xin Qian 8
Some Facts about the Neutrino
• Neutrino Flavor Eigenstate Mass Eigenstate
9
Neutrino OscillationNeutrino Flavor Eigenstate Neutrino Mass Eigenstate
2
1
cossin
sincos
m1
m2
2 2 2 221( ) sin 2 sin 1.27
( ) 1 ( )
L kmP m eV
E GeV
P P
Appearance
Survival 2 2 2ij i jm m m
Neutrino are produced and detected by weak interaction, but propagate as mass eigenstates.
)0(|sin)0(|cos)(| 2)(
1)( 21
EtrPiEtrPi eet
10 CP-violation: P P
13 13 12 12 1
23 23 12 12 2
23 23 13 13 3
1 0 0 cos 0 sin cos sin 0
0 cos sin 0 1 0 sin cos 0
0 sin cos sin 0 cos 0 0 1
ie
i
e
e
23 ~ 45° θ13 and δCP 12 = ~ 32°
2015 Sambamurti Lecture: Xin Qian 11
Available Neutrino Sources
Courtesy of Milind Diwan
CP-violation: P P ee
2015 Sambamurti Lecture: Xin Qian 12
Periodic Summary• To find the origin of matter-anti-matter asymmetry, we
decide to look at the neutrino sector
• With all available channels and practical constraints, we decide to search for new CP violation
• Is this approach viable?
• What about the detector technology?
CP-violation: P P ee
2015 Sambamurti Lecture: Xin Qian 13
Will the signal be non-zero? θ13
• Θ13 is one of three neutrino mixing angles
• Its value was unknown prior 2012
• Do a new experiment to measure Θ13 : Daya Bay
213 ( ) sin 2eP 2
131 sin 2 e eP
2015 Sambamurti Lecture: Xin Qian 14
Reactor Neutrinos• Pure anti-νe source
• ~ 6 anti-νe per fission
• ~ 2 x 1020 anti-νe/GWth/sec
• At 1 km, ~1 event /day/ton/GW
nepe
Inverse Beta Decay
15
The largest, deepest reactor Θ13 experiment in Town
16
Keys to High Precision• Statistics Precision
Powerful reactors (17.6 GW) + Large Mass (80 ton)
• Systematics Accuracy– Reactor: using near/far to form ratio +
baseline (near ~0.4 km, far ~1.7 km)– Detector: “identical detectors” + “precise detector calibration”– Background: deep underground + active/passive shielding
Far/Near νe RatioDistances from
reactor Oscillation deficit
2( , )
( , )far survival fn
near f survival n
N P E LL
N L P E L
17
Daya Bay Anti-νe Detector
192 Photomultipliers on the outside wall
Outer acrylic tank20 ton liquid scintillator
Automated calibration system
Inner acrylic tank20 ton Gd-loaded liquid scintillator
Steel tank40 ton mineral oil
Reflectors at top/bottom of cylinder
5 m diameter
2015 Sambamurti Lecture: Xin Qian 18
2015 Sambamurti Lecture: Xin Qian 19
Detectors in 3 Sites
Experimental Hall 2: Began 1 detector operation on Nov. 5, 2011
Experimental Hall 1Data taking beganAug. 15, 2011
Experimental Hall 3: Began 3 detectors operation on Dec. 24, 2011
2015 Sambamurti Lecture: Xin Qian 20
The Hunting Race for θ13 Since 2011
20
2011
2013
March 2012, Daya Bay reported the discovery of non-zero value of θ13 with a statistical significance > 5σ
2015 Sambamurti Lecture: Xin Qian 21
A Top-10 Scientific Breakthrough of 2012
21Science 338, 1527
2015 Sambamurti Lecture: Xin Qian 22
Periodic Summary• To find the origin of matter-anti-matter asymmetry, we
decide to look at the neutrino sector• With all available channels and practical constraints,
we decide to search for new CP violation
• Is this approach viable?
• What about the detector technology?
CP-violation: P P ee
Yes, θ13 is non-zero ~ 8.4o
23
Signal: νμνe Appearance
• Oscillation patterns are very sensitive to the δCP and the mass hierarchy
2015 Sambamurti Lecture: Xin Qian
Accelerator Neutrino Experiment
(~ 100%)
...
• Accelerator Neutrino Beam
• Far Detector to measure Neutrino Oscillation
• Near Detector to categorize Neutrino beam
2015 Sambamurti Lecture: Xin Qian
Recent Accelerator Neutrino Beams
NUMI @ FNAL
BNB @ FNAL
J-PARC
CNGS
2015 Sambamurti Lecture: Xin Qian
Signal and Background
e
e
Charge-Current
Neutral-Current:
e
e
A e X
A e X
A X
A X
A X
A X
A X
It is important to have a detector which can pick up the electron-neutrinos
2015 Sambamurti Lecture: Xin Qian
It is important to have a detector which can differentiate these reactions
2015 Sambamurti Lecture: Xin Qian 28
Requirements on Detector Technology
• Capability to have excellent differentiation power between signal and background for various reactions
• Detector needs to beable to scale to several 10s of kton economically
Answer: Liquid Argon Time Projection Chambers3D Image of Neutrino Interaction
2015 Sambamurti Lecture: Xin Qian 29
time
dE/dx of 1 MIP: 2.1MeV/cm
First proposed by C. Rubbia, 1977 → ICARUS;
Excellent new opportunity with high res. LArTPC
• Argon: most abundant noble gas (1.3% by weight)
• Electron drift v: 1.6 km/s
• Position resolution ~ mm
• PID: dE/dx through charge collection + event topology
2015 Sambamurti Lecture: Xin Qian 30
For 3D demo, visit http://www.phy.bnl.gov/wire-cell/examples/mvd/nue-cc-v2
/#/1Electron Shower Hadronic Shower
2015 Sambamurti Lecture: Xin Qian 31
For 3D demo, visithttp://www.phy.bnl.gov/wire-cell/examples/list/
Neutral pion Neutrino interaction buried under cosmics
2015 Sambamurti Lecture: Xin Qian 32
Periodic Summary• To find the origin of matter-anti-matter asymmetry, we
decide to look at the neutrino sector• With all available channels and practical constraints,
we decide to search for new CP violation
• Is this approach viable?
• What about the detector technology?
CP-violation: P P ee
Yes, θ13 is non-zero ~ 8.4o
LArTPC is a very promising, but complicated detector technology.
It is crucial to gradually scale up and practice this new technology MicroBooNE an 80 tons LArTPC
2015 Sambamurti Lecture: Xin Qian 33
2015 Sambamurti Lecture: Xin Qian 34
MicroBooNE LArTPC• Time Projection Chamber
– 3 wire planes– 8256 channels– 1.6 ms drift time
• Optical system– 32 cryogenic PMTs
• Laser-based Calibration System
• High Voltage System
• Many innovative technologies
10.3 x 2.3 x 2.5 mUniform field of 500 V/cm170 tons of purified LAr
2015 Sambamurti Lecture: Xin Qian 35
2015 Sambamurti Lecture: Xin Qian 36
2015 Sambamurti Lecture: Xin Qian 37
Moving day!June 23rd, 2014
Data is coming!
2015 Sambamurti Lecture: Xin Qian 38
The Experimental Design and Future Challenges
2015 Sambamurti Lecture: Xin Qian 39
Deep Underground Neutrino Experiment• A horn-produced broad band beam
with 60-120 GeV protons at 1200 kW (upgradable to 2.3 MW) from FNAL
• A baseline of 1300 km towards the Sanford Underground Research Facility in Lead, South Dakota
• A 40 kt fiducial volume Liquid Argon Time Projection Chamber located at the 4850 ft level
• A high resolution near detector at FNAL
• This configuration will be achieved in phases according to $ constraints
Aim for CPV, MH, precision measurements of Δm2
32, sin22θ13, sin2θ23, and δCP
Deep Underground Neutrino Experiment
2015 Sambamurti Lecture: Xin Qian 40
One 10 kton LArTPC
2015 Sambamurti Lecture: Xin Qian 41
There are many challenges ahead
• How to scale up the detector to 40 kt?• How to achieve high purity argon at this scale?• How to properly reconstruct neutrino interaction
events to maximize the potential of this technology?
• How to properly control the systematics for precision measurements?
• How to collect enough resources for construction?
• How to maintain a healthy field with such a long-term project?
• …
2015 Sambamurti Lecture: Xin Qian 42
Summary• We are lucky that θ13 is non-zero
• LArTPC technology is promising and under healthy development
• Design of next-generation long-baseline accelerator neutrino experiment is sound
• It has been a long journey to search for new CP violation to explain why we are made of matter
• Our patience will be rewarded, exciting decades to come!
2015 Sambamurti Lecture: Xin Qian 43
In Memorium
Aditya Sambamurti1961-1992
2015 Sambamurti Lecture: Xin Qian 44
Physics Program Of MicroBooNE
44
~eV Sterile Neutrino?MicroBooNE
LAr-ND/T600
LBNF
(Anti)-Neutrino-Argon
Cross Section
MH, CPVUnitarity Test