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Neutrinos: From Cosmic Rays and Accelerators to Old Iron Mines and the Fate of the Universe
Alec Habig
UMD Physics
Neutrinos – what are they? decay appears to be a 2-body decay
So, if energy is conserved, the outgoing electron will always have the same energy – simple freshman mechanics
Observed:
epn
A 2-body decay
But… observed spectrum is continuous!
Not a discreteenergy
0 log(E)
log(rate)
Emax
The “Silent Partner”
1930 – Pauli proposes a “silent” partner a 3rd body that doesn’t interact Allows both a continuous spectrum
and conservation of energy 1933 – Fermi details decay
theory, names the neutrino
Solution:
e epn
A 3-body decay!
…they really do exist!
1953 - Fred Reines and Clyde Cowan see inverse decay at the Savannah River reactor:
enpe The positron was observed in a
tank of scintillating fluid. Reines gets 1995 Nobel Prize.
More flavors of 1949 – Powell et al infer the
presence of another in decay and of two more in decay
Add in the more recently observed decay, and: a exists for each lepton
and their anti-particles
,,e
,,e
The “bookkeeping” particle
Cataloging all the reactions, neutrinos are used to account for:
Conservation of Energy Conservation of lepton # and flavor Conservation of angular
momentum (“spin”)
Neutrino properties
These balancing acts work if the has the following properties:
No electrical charge ’s only interact via the weak force
All ’s are left-handed Spin = -½
Both by direct observation, and following from spin lefthandedness m= 0
No Mass?
Direct experimental results say: Mass of e < 3eV!
Compare to: Mass of e = 511 thousand eV Mass of p = 938 million eV
n.b. : 1eV = 1.8x10-33 g!
0 log(E)
log(rate)
Emax
Emax-E
Oscillations!
But, if neutrinos have any mass, quantum mechanics tells us they should “oscillate” between flavors
The probability that a will change to a after traveling distance L is:
E
LmP
222 27.1
sin)2(sin)(
E
LmP
222 27.1
sin)2(sin)(
Parameters of nature: m2 (between the two flavors) sin2(2) (“mixing angle” or
amplitude)
Things we can measure: or , L, E
Note that L/E is proportional to the ’s own “proper time”
How to make a e come from radioactive decay and
decay of come from decays of and come from decay
Observed directly for the first time recently! (by the DONUT experiment)
In practice, to get – ‘s come from decay ‘s come from high energy nucleon
collisions So smack together some protons!
Cosmic Rays Mother Nature
sends the high energy protons to us from space
Collisions with the atmosphere make particle showers
For more, see Scientific American,August 1999 issue
Super-Kamiokande 50kT ultra-pure
water 22.5kt fid. Volume ~85m att. length
11134 50cm PMTs 40% coverage by
photocathode 2ns timing
1800 20cm PMTs in veto shield
Located in zinc mine near Kamioka, Japan
http://www-sk.icrr.u-tokyo.ac.jp/doc/sk/index.html
1 km(2700 mwe)
40 m
40 m
SK images courtesy of Institute for Cosmic Ray Research, The University of Tokyo
Who is Super-K?
~140authors
~35insti-tutions
UMD@Super-K, Summer 2001
Dan Gastler (UMD), floating in top of OD
Alec Habig (UMD) and Jim Stone (BU),fixing Tyvek in barrel of OD
UMD@Super-K, Summer 2001
Andrew Clough (UMD), making cable ends with Erik Blaufuss (Maryland),
Jeff Griskevich (UCI), and Katy Mack (Caltech)
Dan and Erik replace a top OD PMT
(lots more pictures at http://neutrino.d.umn.edu/~superk)
How does it work?
Graphics by Ed Kearns, Boston Univ.
e, , or ?Two similar eventsSeen in “unrolled” view
e-like event at top Showers Fuzzy ring
-like event below One particle Crisp ring decays – makes e
– can’t see! Need very high energy to produce
How far did the go?
The ’s come from cosmic rays hitting the atmosphere
The travels: L ~ 20km from
above L ~ 500km from
the side L ~ 10,000km
from below
The Resultse
From below From above
All e data are consistent with expectations.
Lowest E all low
Higher E ok from above, low from below
Data match oscillations!
Key Data no-oscillations oscillations
Oscillation Parameters oscillating to
(thus disappearing) fits the data well
Values of parameters inside contours work
Best fit values: m2 ~ 2.1x10-3
sin22 ~ 1 At 90% cl:
1.5x10-3 < m2 < 3.4x10-3 eV2
sin22 e not involved
Other Super-K ’s
Low-energy ’s from fusion in core of the Sun (dozens per day)
Very high-energy ’s from Active Galactic Nuclei (black holes) or Gamma-Ray Bursts (if we were bigger or get lucky)
Low-energy ’s from Supernovae in our galaxy (the next time one happens!) Can also make statement about diffuse
SN background! (“SN relics”), probe star formation history of universe
SNEWS Supernova
Early Warning System
Watches for coincidence from world’s detectors
Issue SN alarm, ~hours before light breaks out!
Super-Kamiokande (Japan) 50kton
Sudbury Neutrino Observatory(Canada) 1.7kton H2O, 1kton D2O
(Mini-BooNE, KamLAND, Borexino, AMANDA, LIGO also sensitive to nearby SN but not yet sending alarms to SNEWS)
7000 inv. decay, 410 on 16O, 300 elast. scattering, 4o pointing
710 inv. decay, 160 2H breakup, 45 elast. scattering, 17o pointing
Server10s coincidence
window
Email alarmsto astronomers
SSL sockets
PGP signed email
Coincidence server securely hosted byBrookhaven National Lab
Sign up yourself to receive an alert at: http://snews.bnl.gov/
LVD (Italy) 1ktonLiquid scint ~300 e
Experimental Disaster After repairs, SK was slowly
refilled with water One PMT failed, imploded Shock wave crushed neighbors Chain Reaction 2/3 of all PMTs crushed
Recovery Work In the summer of 2002,
47% of ID tubes and all OD tubes were replaced ID tubes with acrylic
shields UMD people worked
all summer SK is operational again Data taking resumed in
Dec. 2002!
Our Work in the OD (2002)
UMD@Super-K, Summer 2005
Rose Smith (UMD), with Tom Kreicbergs (Hawaii),
Aaron Herfurth (BU), and Kirsti Hakala (UMD)
John Eastman (UMD) , Photographer
(lots more pictures at http://neutrino.d.umn.edu/~east0108)
Prepared 6,000 replacement PMTs(being installed now!)
Accelerators Make our own high energy protons
120 GeV p+ Graphite target,Focusing “horn” decay pipe absorber “Near Detector”
Focus the resulting ’s into a beam Let the ’s decay to ’s
Shoot them into a fixed target
Result – a carefully controlled beam!
beam
MINOS
Main Injector Neutrino Oscillation Search
A direct end-to-end oscillation experiment Make our own ’s Measure them at the source
“Near Detector” Measure them again 735km away
“Far Detector” Watch them change flavor!
http://www-numi.fnal.gov
Who is MINOS?
32 institutions175 physicists
Argonne • Athens • Benedictine Brookhaven • Caltech • Cambridge Campinas • Fermilab • College de
France • Harvard • IIT Indiana ITEP-Moscow • Lebedev Livermore •
Minnesota-Twin Cities Minnesota-Duluth • Oxford
Pittsburgh • Protvino • RutherfordSao Paulo • South Carolina
Stanford • Sussex • Texas A&M Texas-Austin Tufts • UCL Western
Washington • William & Mary • Wisconsin
A cross-country beam The ’s start at Fermilab,
aimed down a bit (3.3o) ’s pass under Wisconsin,
Lake Superior, and Duluth, oscillating as they travel
Beam is observed again at the Soudan Mine
735 km
The Old Iron Mine
Soudan Iron mine has been a state historical park since the 1960’s
A new cavern has been excavated at the bottom of the mine
Adjacent to Soudan2 expt. and Historical Tour
Crygenic Dark Matter Search (CDMS) in Soudan2 hall
Expanding the Lab Excavation complete 12/00 Experimental construction started
August 2001 Tours started summer 2002 Come see us!
http://www.soudan.umn.edu
Spring 2000
March 2001December 2000
The MINOS Far Detector Made of 1” x 8m steel octagons Sandwiched with plastic scintillator Steel is magnetized to 1-2 Tesla 5.4kt total steel (3.3kt fiducial) 486 layers – 31m long Near detector similar but smaller
½ Far Det. in cavern
The whole thing!
MINOS Starts to Grow
Current View of MINOS Far Detector
is finished!
Schedule Far detector completed July
2003 Started taking Cosmic Ray
data Many atmospheric neutrino
events have been seen! Near detector finished mid
2004 beam started beginning of
2005 Running beautifully now
2-3 years data taking needed to meet expectations, 5-10 years hoped for Achieved exposure equal to
K2K in December 2005
Scintillator
Scintillator emits light when a charged particle passes through
MINOS uses plastic scintillator strips 4cm wide, 8m long Light carried out of the
ends to Photomultiplier tubes via optical fiber
192 strips per plane Alternate planes at right
angles to get 3D view
Photo of ascintillator strip
41 mm 10 mm
As long as
desired
…
Cross-section photo of two scintillator strips with fibers glued into grooves.
Scintillator graphicscourtesy of Doug Michael, Caltech
More Scintillator
An M16 PMT
A moduleA blue LED lights up the Scintillator
Scintillator layout 8 modules cover one far
detector steel plane Four 20-wide modules in
middle (perp. ends) Four 28-wide modules on
edges (45 deg ends) Two center modules have
coil-hole cutout
M16 PMT
16 mm
Fiber LayoutCoil B
ypas
s28
28
2828
2020
2020
Plane Assembly MINOS planes are
assembled from parts which can fit down the shaft
Two ½” layers of steel welded together to form 1” thick, 12 ton plane
1 ton scintillator attached to that
Plane hung like a file folder
Multiplexing Light detected by
16 pixel PMTs 8 fibers per pixel,
ganged together to reduce electronics costs by 8x
M16 PMT
16 mm
Fiber Layout
One of 3 Ham. M16PMTs in this “Mux Box”
Front End Electronics Fibers from each strip end are multiplexed onto PMT pixels Signals amplified, shaped, and tracked+held by “VA” chips Hit and Timing information sent upstream from this “Front
End” rack
Data Gathering VME “Master” crate
VA Readout Controllers “VARC”s
Charge from PMTs digitized by 14-bit ADCs
Time stamped to 1.6ns by internal clock
2/6 or 2/36 pre-trigger applied
Hits given absolute GPS time
Data read out over PVIC bus to computer room 4/5 plane software trigger
applied, hits time ordered Data formatted in ROOT
1 of 16 VME cratesDigitizes 72 mux boxesEach w/3 16-pixel PMTs
De-multiplexing If we read out eight fibers with one PMT pixel
How to figure out which strip a particle really went through? Matching hits on both ends of a strip helps in the simplest
track case For multiple hits on a plane and showers:
All the different possible “hypotheses” of which strip was really hit tested against the possible real physics
Best fitting hypotheses saved Reconstructing close multiple muons is very difficult!
A Cosmic Ray De-multiplexed Success rate for Cosmic Rays:
94% of hits correctly associated with their strips 97% of CR events successfully sorted out
A Double Cosmic Ray
A real event Two Cosmic Ray ’s, from same initial
interaction
See live events athttp://farweb.minos-soudan.org/events/LiveEvent.html
interactions in MINOS
First beam neutrino event! In time with beam, coming from Fermilab
interacts in rock or steel, resulting particles splash through detector Charged particle curves in magnetic field (more at the end
as it slows down) Scintillation light read out of strips
Each “pixel” is a lit up strip!
3D reconstruction
16.5 GeV muon
‘s are single, penetrating particles
8.5 GeV electron
e’s make showers which quickly peter out
MINOS simulations courtesy of Brett Viren, Brookhaven Natl. Lab
Expected MINOS results Compare spectrum
near and far Here are expected
results given 3 different sets of oscillation parameters
With same L (735km), lower E ’s will oscillate to and disappear
With no e originally in the beam, any e appearing will be very interesting!
Comparative Resolution
MINOS can make very precise measurements of the oscillation parameters
MINOS’s expected precision (green) is compared to SK’s (yellow) for three different values of m2
So What?’s change flavor as they go along,
and thus have some small mass.
Big Deal.
It’s something not predicted by the Standard Model!
Perhaps a hint towards a Grand Unified Theory – theorists have new fundamental parameters their theories must explain.
Fate of Universe?
’s play a role One has a Very Small mass
(assuming m is comparable to m) But there are incredible numbers of
them sloshing about They could be an appreciable
fraction of the total mass of the universe!
Dark Matter Galactic rotation curves –
luminous matter not enough
Disk stability also needs a Dark Matter halo
If only luminouswere there
Actually observed!
Galaxy M31 image by Jason Ware.
Rocks, dust, gas?
Big Bang Nucleosynthesis calculations limit total number of baryons (p, n – i.e., “normal stuff” )
Not enough dark rocks etc. can exist without changing the cosmic ratio of H, He, Li
Need non-baryonic dark matter. ’s qualify, and they have mass
Hot Dark Matter
’s are “hot”, i.e., have kinetic energy much larger than rest mass
If all DM is hot, universe is “too runny” – matter too smoothly distributed for galaxies to form
Simulations say there can still be as much total mass in HDM as all the baryons – but not enough to be all the DM needed!
Cold Dark Matter
Particles with large rest mass (compared to kinetic energy) e.g. WIMPS or Axions
Alone, “too lumpy” at large scales, galaxy super-clusters don’t form
But, “Cold+Hot Dark Matter” models reproduce large scale structure rather well - add in those ’s!
Simulated Universe,Cold+Hot Dark Matter
Real Galaxy Survey
Courtesy of Greg Bryan and Mike Norman, UIUCCourtesy of Margaret Geller and Emilio Falco, Harvard-Smithsonian Center for Astrophysics
Neutrinos Elusive but numerous Massive ’s have both theoretical
and cosmic consequences We observe flavor
oscillations (and thus mass) in cosmic rays with Super-K
MINOS is studying these oscillations using a precision man-made beam with “before” & “after” measurements
This powerpoint is online at:http://neutrino.d.umn.edu/~habig/Neutrinos.ppt
Neutrinos: they are very small They have no charge; they have no mass; they do not interact at all. The Earth is just a silly ball to them, through which they simply pass like dustmaids down a drafty hall or photons through a sheet of glass. They snub the most exquisite gas, ignore the most substantial wall, cold shoulder steel and sounding brass, insult the stallion in his stall, and, scorning barriers of class, infiltrate you and me. Like tall and painless guillotines they fall down through our heads into the grass. At night, they enter at Nepal and pierce the lover and his lass from underneath the bed. You call it wonderful; I call it crass.
-John Updike
