NNbar Oscillation Search With Cold Neutrons DUSEL

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N-Nbar Oscillation Search With Cold Neutrons
_at_DUSEL
M. Snow Indiana University/IUCF DUSEL workshop
Phenomenology/previous experiment Improved limit
of 1000 in transition rate possible with cold
neutrons Also at this workshop A3 RD plans,
cost schedule (Y. Kamyshkov/Tennessee) B1 Low
level counting backgrounds from TRIGA (J.
Hill/CSUDH) B2 Other Uses vertical facility (Y
Kamyshkov/Tennessee) B3 Instrumentationnnbar
technologies (G. Greene/Tennesee-ORNL) B4
Theory nnbar oscillations (R. Mohapathra/Maryland
) B5 Facilities nnbar facility requirements
(Lee Petersen/CNA) B5 Facilities reactor
facility at DUSEL (Y. Kamyshkov/Tennessee) B6
Management TRIGA licensing and ownership (Y.
Kamyshkov) B7 nnbar education and outreach plans
(S. Pfiffnet/Tennessee)

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Scientific Reach Discussed in Recent LBL Workshop
http//inpa.lbl.gov/blnv/blnv.htm
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Neutron-Antineutron transition probability
quasifree condition
Contributions to V ltVmattergt100 neV,
proportional to density ltVmaggt?B, 60 neV/Tesla
B10nT-gt Vmag10-15 eV ltVmattergt , ltVmaggt both
gtgt?
Figure of merit Nneutrons,
Tquasifree observation time
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N-Nbar search at ILL (Heidelberg-ILL-Padova-Pavia)

• No GeV background
• No candidates observed.
• Measured limit for
• a year of running

Baldo-Ceolin M. et al., Z. Phys. C63,409 (1994).
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Scheme of N-Nbar search experiment at DUSEL
3 MW TRIGA research reactor with vertical
hole and cold neutron moderator vn 1000
m/s Vertical shaft 1000 m deep with diameter
4-5 m at DUSEL Large vacuum tube,
focusing reflector, magnetic shielding
Detector (similar to ILL N-Nbar detector) at
the bottom of shaft Letter of intent to DUSEL
submitted
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Sources of x1000 Improvement on ILL Experiment
with Cold Neutrons
-increased phase space acceptance of neutrons
from source (use new supermirror technology, some
RD, see G. Greene talk B3) x60 -increase
running time x3 -increase neutron free-flight
time time x100 -decreased source brightness
x1/20 Must maintain quasifree condition
magnetic shielding RD (see G. Greene talk
B3) For horizontal experiment greater source
brightness counteracted by (dispersive)
gravitational defocusing of Maxwellian neutron
spectrum
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Annular core TRIGA reactor (General Atomics) for
N-Nbar search experiment
GA built 70 TRIGA reactors 0.0114 MW (th)
19 TRIGA reactors presently operating in US
(last commissioned in 1992) 25 TRIGA reactors
operating abroad (last commissioned in
2005) some have annular core and vertical
channel
1 ft
Well-established technology
annular core TRIGA reactor 3.4 MW with convective
cooling, vertical channel, and large cold LD2
moderator (Tn 35K).
See Y Kamyshkov talk B6
Courtesy of W. Whittemore (General Atomics)
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Supermirrors ?critical ?m?critical

• Commercial Supermirror Neutron Mirrors are
  Available With m 3 - 4.
• Phase space acceptance for straight guide ?m2,
  more with focusing reflector

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1000 layers
Reflectivity
q
m
q
Multilayer mirror
c
c
Items of commerce
Engineering RD issues _at_DUSEL (1) Mechanical
support of large vertical neutron reflector in
tube (2) Assembly of reflector into tube
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Quasifree Condition B Shielding
?Btltlt? ILL achieved Blt10 nT over 1m diameter,
80 m beam,one layer 1mm shield in SS vacuum tank,
1 reduction in oscillation efficiency (Bitter
et al, NIM A309, 521 (1991).
Engineering RD issues _at_DUSEL (1) Mechanical
support of large vertical magnetic shield (2)
Assembly of shield (3) Magnetic environment of
shaft
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Vopttltlt? Need vacuum to eliminate
neutron-antineutron optical potential
difference. Plt10-5 Pa is good enough, much less
stringent than LIGO
Quasifree Condition Vacuum
Neutron shaft

• Engineering RD
• issues _at_DUSEL
• Mechanics of vertical tube
• (2) Assembly of vertical tube
• (3) Straight shaft 5?

Detector Hall
Door
Control Room Electronics
Access Tunnel
Neutron Dump
See L. Petersen CNA Engineering, B5
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The conceptual scheme of antineutron detector
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New Experiment at Existing Research Reactor?
need cold neutron source at high flux reactor,
close access of neutron focusing reflector to
cold source, free flight path of gt300m
No luck so far (requests to all gt20 MW
research reactors with cold neutron sources)
Cutaway view HFIR reactor at ORNL
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Education/Outreach (S. Pfiffnet/B7)
teach the process to students just how does
one do such a large-scale engineering
study? Engineering and physics workshop at/near
DUSEL Public seminars/lectures associated with
project meetings (energy resources, nuclear
technology) Undergraduate/graduate research (ex
neutron optics simulations, antineutron detector
backgrounds,) College coursework enhancement in
Systems Design (UT, NCSU) DUSEL-related lesson
plans for local high school teachers
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Conclusions
Sensitivity of cold neutron experiment for n-nbar
transition rate can be improved by factor of
1000. Combination of improvements in neutron
optics technology, longer observation time (from
vertical arrangement _at_DUSEL), and larger-scale
experiment Clearly serious engineering and other
issues remain to be addressed before any vertical
experiment can be seriously proposed. Work on
these issues is in progress, see next talk by YK.
A RD effort would be needed to provide the
information required to prepare a reliable cost
estimate
What strikes me most is where you found space
for all this M. Bulgakov, The Master and
Margarita
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NNbar Summary
New physics beyond the SM can be discovered by
NNbar search at DUSEL Expected improvement in
N-Nbar transition probability is a factor of
1,000
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Proto-collaboration for RD Studies
Ayman Hawari, Bernard Wehring, Albert Young, NC
State Alexandre Kozlov Anatoli Serebrov,
PNPI Kenneth Ganezer, Brandon Hartfiel, Jimm
Hill, CSUDH David Baxter, Chris Lavelle, Chen-Yu
Liu, W. M. Snow, Indiana George Flanagan,
Jeffrey Johnson, Gary Mays, ORNL H Lee Dodds,
Yuri Efremenko, Geoff Greene, Susan Pfiffner, Y.
Kamyshkov, Tennessee JeeSeung Jang Pieter Mumm,
NIST Y. Pokotilovskiy, Dubna Rabindra N
Mohapatra, Maryland Takeyasu Ito, LANL William
Bugg, SLAC H. Shimizu, KEK
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(Specific) Scientific Motivation for nnbar
search Neutrino mass-NNbar connection

• Majorana neutrino -gt implies ?(B-L)2
• In quark-lepton unified theories B and L get
  connected, ?L2 implies ?B 2 via B-L symmetry
• -gt N-N-bar oscillation.
• There are reasons to think that there may be
  quark lepton unification at high energies.
• N-N-bar oscillation can be new window to Q-L
  unification as well as B-L symmetry.
• (see R. Mohapathra talk B4)
• Baryon and Lepton Number Violations Workshop
• Sept. 20-22, 2007, LBL http//inpa.lbl.gov/blnv/bl
  nv.htm

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Sensitivity of vertical experiment
For 3 years operation improvement in limit on
transition rate is 1000 horizontal experiment
could be comparable (shorter length compensated
by higher neutron flux)