fundamental*neutron*physics*...
TRANSCRIPT
Fundamental Neutron Physics Experiments at LANSCE
Mike Snow Indiana University
IU Center for SpaceBme Symmetries NSR/TREX CollaboraBons
LANSCE LUG 2015 Santa Fe
1. Why are LANSCE beams of interest for fundamental neutron physics? 2. Example 1: search for exoBc spin-‐dependent neutron interacBons 3. Example 2: on the way to a test of Bme reversal invariance in epithermal neutron resonances WE NEED LANSCE FOR THIS WORK!
Why use neutrons?
1. Zero electric charge, small magnetic moment, very small electric polarizability->low ”background” from Standard Model interactions
2. Deep penetration distance into macroscopic matter, so neutrons can interact with a lot of matter 3. Coherent interactions with matter->phase sensitive measurements possible 4. High neutron polarization routine for neutron beams->useful in searching for spin-dependent interactions
J. Nico and W. M. Snow, Annual Reviews of Nuclear and ParBcle Science 55, 27-‐69 (2005). H. Abele, Progress in ParBcle and Nuclear Physics 60, 1-‐81 (2008). D. Dubbers and M. Schmidt, Reviews of Modern Physics 83, 1111 (2011).
Nuclear/Particle/Astrophysics with Slow Neutrons: Only 2 Beams in US!
NIST Center for Neutron Research Gaithersburg MD. NG-C beam #2 intensity in the world
Spallation Neutron Source Oak Ridge National Lab (TN) Most intense spallation neutron source in the US.
These two beams are now subscribed with experiments for 5-‐10 years! No room to pursue new ideas. No epithermal beam. Go to LANSCE!
Energy Density of the Universe: Present Inventory
We don’t know what makes two largest
pieces!
The largest piece, dark energy, is also the most mysterious
The dark energy
density corresponds to a length scale of
100 microns. TheoreBcal ideas are almost uncountable calls for qualitaBvely new experiments
New interacBons with ranges from millimeters to microns… “Who ordered that?”
1. Weakly-coupled, long-range interactions are a generic consequence of spontaneously broken continuous symmetries (Goldstone theorem)
2. Specific theoretical ideas (axions, extra dimensions
for gravity) imply new interactions at ~mm-µm scales 3. Dimensional analysis: dark energy->100 microns Experiments should look!
transversely-polarized neutrons corkscrew due to a parity-odd interaction
Neutron Spin Rotation: A Parity-odd Observable
neutron index of refraction in target dependent on incident neutron helicity
+y +x
+z
PNC spin rotation angle is independent of incident neutron energy
target
cold
neutrons
polarization vector
Example of a nonstandard P-‐odd interacBon from spin 1 boson exchange: [Dobrescu/Mocioiu 06, general construc9on of interac9on between nonrela9vis9c fermions ]
V ( σ , r , v) =
8πmc2gAgV
σ •v 1re−rλ
§ Induces an interacBon between polarized and unpolarized mafer § Violates P symmetry § Not very well constrained over “mesoscopic” ranges(millimeters to microns) § Best invesBgated using a beam of polarized parBcles
€
gV γ 5gA
Transversely polarized neutrons corkscrew due to weak interacBon ϕPNC= [+1.7 ± 9.1 (stat) ±1.4 (sys)] x 10-‐7 rad/m W. M. Snow et al., Phys. Rev. C83, 022501(R) (2011). W. M. Snow, et al., Rev. Sci. Inst. 86, 055101 (2015).
Neutron Spin RotaBon Search in n+4He at NIST
Constraints on exoBc neutron V-‐A interacBons
H. Yan, and W. M. Snow, Phys. Rev. Lef. 110, 082003 (2013). Also: much stronger constraints now above ~1 cm from Eot_Wash+ other data [E. G. Adelberger and T. A. Wagner, PRD 88, 031101 (2013)]
Log(|gVgA|)
! (m)
Mass (eV)
-30
-25
-20
-15
-10
-5
10-6 10-5 10-4 10-3 10-2 10-1 100
10-510-410-310-210-1
From neutron spin rotaBon In 4He
Neutron Spin RotaBon (NSR) CollaboraBon W.M. Snow1, E. Anderson1, L. Barron-‐Palos2, C.D. Bass3, T.D. Bass3, B.E. Crawford4,
C. Crawford5 , W. Fox1, J. Fry1, K. Gan6, C. Haddock1, B.R. Heckel7, D. Luo1, M. Maldonado-‐Velazquez2, R. Malone4, D. M. Markoff 8, A.M. Micherdzinska9, H.P. Mumm10, J.S. Nico10, A.K. Opper9, C. Paudel13, S. Penn 11, S. Santra12, M.G.
Sarsour13, S. van Sciver14, E. I. Sharapov 15, H.E. Swanson 7 , J. Vanderwerp 1, S. B. Walbridge 1, H. Yan 1, and V. Zhumabekova 16
Indiana University / CEEM 1
Universidad Nacional Autonoma de Mexico 2 Thomas Jefferson NaBonal Accelerator Facility 3
Gefysburg College 4 University of Kentucky 5 University of Winnipeg 6 University of Washington7
North Carolina Central University 8 The George Washington University 9
NaBonal InsBtute of Standards and Technology 10 Hobart and William Smith College 11 Bhabha Atomic Research Centre 12
Georgia State University 13 Florida State University14
Joint InsBtute for Nuclear Research 15 Al-‐Farabi Kazakh NaBonal University 16
Support: NSF, NIST, DOE, CONACYT, BARC
5th force Long-‐Range InteracBons • Extensions to Standard Model suggest possibility of weakly
interacBng, light bosons • Presence of a spin-‐1 boson exchange causes the transverse
neutron polarizaBon to Blt forward
A Proposal to Search for a Possible Exotic Spin-Dependent
Interaction of Slow Neutrons with Matter at LANSCE FP12
(Proposal #6559)
V (!σ , !r, !v) = !
8πmc2gAgA
!σ •(!vx!r )1
re−rλ
supermirror polarizer (45 cm)
magnetic shields
input coil non-magnetic SM (m=2) input guide (125 cm)
Segmented 3He ionization chamber
non-magnetic SM (m=2) output guide (200 cm)
supermirror polarization analyzer
(45 cm)
AFP spin flipper
output coil
pi/2 turner
NSRf5 Apparatus – Target with a Density Gradient
target (50 cm)
Geneva Mechanism: Rotate the target by increments of 90° (Quadrants)
Measured rotaBons in 10-‐7–10-‐6 rad range will place limits on (gA)2 at 10-‐16 level for 0.1–3mm length scales
1x10-‐6 2x10-‐6 3x10-‐7
1x10-‐4 2x10-‐4 3x10-‐5
Sakharov Criteria to generate maDer/an9maDer asymmetry from the laws of physics – Baryon Number Violation (not yet seen) – C and CP Violation (seen but too small by ~1010) – Departure from Thermal Equilibrium (no problem?)
A.D. Sakharov, JETP Lef. 5, 24-‐27, 1967
MaDer/An9maDer Asymmetry in the Universe in Big Bang, star9ng from zero
Relevant neutron experimental efforts Neutron-antineutron oscillations (B) Electric Dipole Moment searches (T=CP) T Violation in Polarized Neutron Optics (T=CP)
“Time Reversal” -‐> MoBon Reversal
V1(t=0)
V2(t=1)
-V2(t=0)
V3(t=1)
Is the final state of the motion with time-reversed final conditions V3(t=1) the same as the time-reversed initial condition -V1(t=0)?
This is an experimental question Gotta reverse the spins too
Apparatus to Measure σ .k Parity ViolaBng Asymmetry
TRIPLE collaboraBon at LANSCE measured ~80 parity-‐odd asymmetries in p-‐wave resonances in heavy nuclei G. M. Mitchell, J. D. Bowman, S. I. Penwla, and E. I. Sharapov, Phys. Rep. 354, 157 (2001). QuanBtaBve analysis of distribuBon of parity-‐odd asymmetries conducted using nuclear staBsBcal spectroscopy S. Tomsovic, M. B. Johnson, A. Hayes, and J. D. Bowman, Phys. Rev. C 62, 054607 (2000).
Parity ViolaBon in 139La .734 eV Δσ/σ =0.097±.005. 106 amplificaBon of parity violaBon!
T violation is also amplified on the same resonanceSensitivity to T violation can be highNeed polarized eV neutron transmission through polarized nuclear target
“MoBon-‐Reversed” Experiment (sys error free in n opBcs limit)
He Polarizer
He Detector
Xe polarized Target
1313 3N
He Polarizer
He Detector
Xe polarized Target
131 3 3N
N
N
+
-
kn
-kn
-I
I�n
-�n
A true null test for T invariance for forward scattering (like EDMs) arXiv:1407.7004
f3<<f1, f2
FP5 Approved Experiment for TREX
Test of current-‐mode NaI(Tl) detector at the 60m locaBon If it works: we can consider a new survey of nuclei to looks for good candidates for a Bme reversal experiment
Summary • Neutron beams provide unique sensiBvity to possible exoBc new interacBons in Nature
• The NSR CollaboraBon has developed an apparatus capable of measuring rotaBons due to exoBc spin-‐dependent interacBons at LANSCE FP12.
• The TREX CollaboraBon plans to test current-‐mode NaI(Tl) detectors at LANSCE FP5 for applicaBon to a future Bme reversal experiment on neutron resonances
LANSCE is an excellent place to explore these and other new ideas for fundamental neutron physics measurements