1. An Accelerator-Produced, Sub-GeV Dark Matter Search with the MiniBooNE Neutrino Detector
Robert Cooper, New Mexico State University on behalf of the MiniBooNE Collaboration

2. Dark Matter Overview
Abundance of cosmological and indirect evidence for dark matter
Galaxy radial velocity
Gravitational lensing
Nebulae dynamics
“Wimp Miracle” suggests GeV dark matter scale
So far, no fully verified detection claims
Direct (Colliders)
Annhilation
Scattering
10/31/15
R.L. Cooper -- APS DNP 2015

3. Minimal Vector Portal Model
Similar to “dark photon” and introduces additional dark sector coupled kinematically with U(1) vector mediator: 4 new parameters:
Need to suppress SM decays: mV > 2mc SM
Detection
Production
1C. Boehm & P. Fayet, Nucl. Phys. B683 (2004) arXiv:hep-ph/ [hep-ph] C. Boehm et al., Phys. Rev. Lett. 92 (2004) arXiv:astro-ph/ [astro-ph]
B. Batell et al., Phys. Rev. Lett. 113 (2014) arXiv: [hep-ph] P. deNiverville et al., Phys. Rev. D84 (2011) arXiv: [hep-ph]
10/31/15
R.L. Cooper -- APS DNP 2015

4. The MiniBooNE Detector
12 m, 800 ton mineral oil (CH2) Cherenkov detector for nm  ne oscillation search
Optically separated Inner signal / outer veto regions (1280 / 240) × 8” PMTs
Nucleon / electron PID from slower impurity fluor scintillation (N) vs. Cherenkov (e/m)
10 years running: n-mode (6.7×1020 POT), n-mode (11.5×1020 POT)
11 oscillation, 14 cross section / flux papers
19 Ph.D Theses
1A.A. Aguilar-Arevalo et al., Nucl. Instrum. Meth. A599 (2009) 28. arXiv: [hep-ex] 2See our website for a list of all publications.
10/31/15
R.L. Cooper -- APS DNP 2015

5. Suppress n and Produce c at BNB
Normal operation: FNAL BNB delivers 8.9 GeV protons Be target  typical 2×1020 POT yearly
Dark matter operation: divert beam “around” target to 50 m steel beamstop
p± DIF (nm progenitor) suppressed by absorption or DAR in beamstop
p0 decays quickly (c progenitor) and unaffected by beamstop
Beam “off-target” to 50 m beamstop
10/31/15
R.L. Cooper -- APS DNP 2015

6. Off-Target Neutrino Background
New Beamline MC developed
CCQE finds ~50 suppression factor
Preliminary
Preliminary
ON  OFF Target MC
1A.A. Aguilar-Arevalo et al., Phys. Rev. D79 (2009) arXiv: [hep-ex]
10/31/15
R.L. Cooper -- APS DNP 2015

7. MiniBooNE Neutrino Suppression
10 months of running and we collected 1.86×1020 POT
10/31/15
R.L. Cooper -- APS DNP 2015

8. What Is Expected In MiniBooNE?
Consider nucleon elastic scattering
MeV most sensitive recoil range
Same as n NC elastic  SUPPRESS n
DM signal + n BG
With production, cross section, and efficiency: most sensitive region is MeV nucleons
n BG
1A.A. Aguilar-Arevalo et al., Phys. Rev. D82 (2010) arXiv: [hep-ex]
2A.A. Aguilar-Arevalo et al., Phys. Rev. D91 (2014) arXiv: [hep-ex]
10/31/15
R.L. Cooper -- APS DNP 2015

9. Preliminary Results (3.19×1019 POT)
Event Selection:
1 Track (1 recoil)
In beam time
Fiducialized
No veto activity
Hits threshold
Energy threshold
Nucleon PID
Blind Analysis (17% of data open)
Anticipate systematics limited at about 10%
Beam unrelated is largest in total c
n,p
10/31/15
R.L. Cooper -- APS DNP 2015

10. Double Ratio Method Preliminary Preliminary Preliminary Preliminary
Many systematics in common
On-target n runs Off-target c runs
Neutral current (NC) Charged current (CC)
Initial estimates assume uncorrelated errors
Shown are individual distributions
Final fit on ratio soon
Preliminary
Preliminary
Preliminary
Preliminary
10/31/15
R.L. Cooper -- APS DNP 2015

11. Dark Matter Propagation Time
Massive c delayed relative n (mc = 120 MeV, E = 1.5 GeV  6 ns )
Beam – 81× 20 ns RF bunches
dt ~ 1.5 ns Cherenkov (ec)
dt ~ 4.2 ns Scintillation (Nc)
Preliminary
Preliminary
10/31/15
R.L. Cooper -- APS DNP 2015

12. Dark Matter Exclusion Plots
Nucleon – DM
Electron – DM
events
events
1-10 events
10/31/15
R.L. Cooper -- APS DNP 2015

13. Conclusions
MiniBooNE has collected 1.86×1020 POT in beam-off-target configuration to search for sub-GeV dark matter
Beam-off-target suppresses neutrino backgrounds  beam uncorrelated backgrounds dominant
First of its kind, proton beam dump to a large neutrino detector  an extremely well characterized detector!
N-DM analysis will be completed soon  e-DM and inelastic p0 channels are underway
10/31/15
R.L. Cooper -- APS DNP 2015

14. Previous Beam Dump / Fixed Target Experiments – Proton Beams
1Table by R.T. Thornton, Indiana University Nuclear Physics Seminar, Nov. 21, 2014
10/31/15
R.L. Cooper -- APS DNP 2015

15. Vector Portal Exclusion Plots
Nucleon – DM
Electron – DM
events
events
1-10 events
10/31/15
R.L. Cooper -- APS DNP 2015

16. Decay Pipe Survey with FRED
FRED: Finding Radiation Evidence in the Decay pipe
Visual and magnetic field survey  no anomalies
Deployable mast for Hall probes 1 & 2
Hall probe 1
Hall probe 2
Forward-looking LIDAR
Hall probe 3
Camera & Light & Mic
Rear-looking LIDAR
Water level
Gyro
Accelerometer
LabJack digitizer
PoE / USB power distribution system
Tether & strain relief
Flipper arm
10/31/15
R.L. Cooper -- APS DNP 2015