Beyond Standard Model Physics in MicroBooNE: Results & Prospects José I. Crespo-Anadón Columbia University Nevis Laboratories 02/12/2020 Lake Louise Winter Institute 2020 Outline ● Search for Heavy Neutral Leptons. ● Search for neutron-antineutron oscillation. ● Revisiting MiniBooNE Low-Energy Excess. José I. Crespo-Anadón BSM in MicroBooNE 2 Outline ● Search for Heavy Neutral Leptons. [arXiv:1911.10545] Accepted today for publication in PRD ! ● Search for neutron-antineutron oscillation. ● Revisiting MiniBooNE Low-Energy Excess. José I. Crespo-Anadón BSM in MicroBooNE 3 Heavy Neutral Leptons (HNL) ● Extension of SM by adding right-handed counterparts to left-handed neutrinos. ● Singlets under SM interactions → Sterile neutrinos. ● Can have both Dirac (Yukawa) and Majorana masses. Mass scale unconstrained. ● Interesting phenomenology: See-saw mechanism explains SM neutrino mass scale. Provide dark matter candidate, baryon asymmetry mechanism (νMSM). Phys.Lett. B620 (2005) 17-26 Phys.Lett. B631 (2005) 151-156 From arXiv:1504.04855 José I. Crespo-Anadón BSM in MicroBooNE 4 HNL Production in Fermilab SBN Program ● HNL may be produced in BNB/NuMI secondary meson decays through mixing with l (μ, e) Standard Model neutrinos. π+, K+ Extended PMNS mixing matrix elements: Ue4, Uμ4 (no τ production). ν Ul4 × ● Mass range up to 493 MeV (K-decay phase N space). Produced in decay pipe ● Full beam line simulation. JHEP 1704 (2017) 102 HNL flux can be derived from SM neutrino flux P. Ballett, S. Pascoli, M. Ross-Lonergan from meson decay. Large mass: – No helicity suppression. – Flux enhanced kinematically (more focused). ● No oscillation due to large mass – loss of coherence. ● HNL decays in flight. Look for HNL decays within the MicroBooNE detector (~470 m from beam target). José I. Crespo-Anadón BSM in MicroBooNE 5 S. D. Porzio's PhD Thesis (2019) Solid: |U = 1 HNL decay channels µ4| Dashed: |Ue4| = 1 ● CC + NC: N → 3ν, νπ0, e-e+ν, μ-μ+ν ● CC: N → γν, μeν, eπ, μπ N l- U l4 W+ u π+ d ● First search in a LArTPC [arXiv:1911.10545]. ● Search for HNL decays within the LArTPC: clean vertex. µ ● Focus first on Uµ4-mediated N → μπ. Mass range: 260 – 385 MeV. π ● Relatively forward-going. ● Reconstruct invariant mass. José I. Crespo-Anadón BSM in MicroBooNE 6 HNL trigger N decay pipe dirt (420 m) 50 m ● HNL travel slower than SM neutrinos. ● Opportunity: extend neutrino trigger window to capture HNL delayed events. Delayed HNL window BNB trigger window extended by 33% (extra w 624 ns). o d n i ● HNL trigger commissioned in June 2017. w BNB window L N ● First HNL search: focus on delayed HNL H window. – No SM neutrino background. Only cosmic ray background. ● Data-driven background measurement using an off-beam trigger with same thresholds as the HNL trigger. José I. Crespo-Anadón BSM in MicroBooNE 7 HNL trigger N decay pipe dirt (420 m) 50 m ● HNL travel slower than SM neutrinos. ● Opportunity: extend neutrino trigger window to capture HNL delayed events. BNB trigger window extended by 33% (extra 624 ns). ● Delayed HNL trigger commissioned in June 2017. HNL BNB window window ● First HNL search: focus on delayed HNL window. – No SM neutrino background. Only cosmic ray background. ● Data-driven background measurement using an off-beam trigger with same thresholds as the HNL trigger. José I. Crespo-Anadón BSM in MicroBooNE 8 Preselection of HNL candidates ● 2E20 Protons on Target passing data quality cuts.. ● Pandora pattern recognition: any vertex with 2 tracks. ● Vertex fiducial volume: exclude TPC edges and sub- performing wires. ● Vertex-track distance: require good vertex reconstruction. ● Number of hits: tracks with E > ~ 20 MeV. ● Flash requirement: consistency between reconstructed scintillation light signal and vertex location. ● Track containment: tracks fully contained in TPC, excluding TPC edges. Rejects cosmic rays entering the detector. Decrease track distortion due to Space Charge Effects. ● Kinematics: Opening angles < 2.8 rad. Reject cosmic rays reconstructed as 2 tracks. Mass from range-based momenta < 500 MeV. HNL signal efficiency ~ 45% (370 MeV mass) Background passing fraction ~ 1.6% José I. Crespo-Anadón BSM in MicroBooNE 9 Angle between tracks BDT classification HNL candidate momentum ● HNL candidate with most signal-like BDT score Examples of BDT variables selected for each event. Signal Background ● BDTs trained on 5 kinematic variables (angle Angle wrt beam between tracks, candidate momentum, angle wrt direction beam direction, azimuth angle, invariant mass). Data-driven background from off-beam triggers. Signal: MC HNL decays superimposed on off-beam Azimuth angle triggers. – 10 different BDTs for 10 mass points in range 260 – 385 MeV. Invariant mass José I. Crespo-Anadón BSM in MicroBooNE 10 Systematic uncertainties JINST 13 P07006 (2018) Estimated from variations on events with BDT score > 0.95: ● HNL flux: Beam simulation and kaon production. ● Protons On Target (POT) measurement. Dynamically Induced Charge ● Trigger time resolution (mass dependent). ● Simulation of signal induced on Example for HNL with mass 325 MeV neighboring TPC wires (not included in the default MC; reconstruction impact). ● Space Charge Effect: Ar ions accumulate in the detector, distorting the electric field. Comparison between turning on and off the effect in simulation. ● Other detector effects (electron recombination, attenuation, diffusion). ● Dominant uncertainty is background Total uncertainty ranges between 10 – 18% sample statistics. between 260 and 385 MeV. José I. Crespo-Anadón BSM in MicroBooNE 11 Results of HNL search ● No excess found in signal region. ● Limits for both Majorana and Dirac hypotheses. (Dirac: expected rates × 2 smaller) Analysis not sensitive to μ and π charge sign. José I. Crespo-Anadón BSM in MicroBooNE 12 Prospects for HNL searches with LArTPCs ● First search for HNL in a LArTPC. ● 2017 - 2018 dataset analyzed. More data to come. ● Using only delayed trigger window. Possibility of extension to on-beam window. Requires more advanced background rejection. ● Perform search in other channels, extending mass range. Best opportunity at high mass range (~ 0.5 GeV), where other off-axis detectors have flux suppressed. ● Search in NuMI beamline. ● Other Fermilab SBN detectors: SBND: higher flux (× 4 closer to target). ICARUS: more volume (× 5). SBND & ICARUS: fast PMT digitization. Potential to resolve beam micro-structure for increased background rejection. ● Future DUNE ND detector. José I. Crespo-Anadón BSM in MicroBooNE 13 Outline ● Search for Heavy Neutral Leptons. ● Search for neutron-antineutron oscillation. ● Revisiting MiniBooNE Low-Energy Excess. José I. Crespo-Anadón BSM in MicroBooNE 14 Neutron-antineutron oscillation J. Hewes PhD Thesis (2017) ● Baryon number (B): accidental symmetry in Standard Model. ● Neutron-antineutron oscillation: BSM process violating B by 2 units. ● Antineutron annihilates with nucleon. Resulting particles experience Final State Interactions with nucleus. ● MicroBooNE size is too small for a competitive search, but it is a platform to develop the analysis for the future DUNE search. 90 tonnes Near surface Data since August 2015 4 × 10 kton (staged) 1475 m underground First data in 2026 José I. Crespo-Anadón BSM in MicroBooNE 15 Neutron-antineutron oscillation search Signal Signal n + n →π+π-3π0 Cosmic background Background J. Hewes PhD Thesis (2017) ● Exploit LArTPC “bubble-chamber like” pictures using Convolutional Neural Networks (CNN). ● Initial MC-only study shows good separation can be achieved. ● New MC with improved LArTPC signal simulation developed. ● Work in progress. J. Hewes PhD Thesis (2017) José I. Crespo-Anadón BSM in MicroBooNE 16 Outline ● Search for Heavy Neutral Leptons. ● Search for neutron-antineutron oscillation. ● Revisiting MiniBooNE Low-Energy Excess. José I. Crespo-Anadón BSM in MicroBooNE 17 Revisiting MiniBooNE LEE ● MiniBooNE was a Cherenkov detector: cannot distinguish between e and . We do not know the nature of the excess. ● New models provide better fits to the spectra by adding a (dark) Heavy Neutral Lepton produced and decaying in MiniBooNE via a U(1)' dark boson that decays into an e+e- pair. e+e- pair can be mis-id as electron-like appearance in MiniBooNE if collimated or very asymmetric. ● MicroBooNE LEE search can be adapted to search for this signature. Phys. Rev. Lett. 121, 241801 Phys. Rev. D 99, 071701(R) ● MicroBooNE – IPPP Durham collaboration. José I. Crespo-Anadón BSM in MicroBooNE 18 Conclusion Exciting Beyond Standard Model physics program at MicroBooNE. ● First MicroBooNE BSM result: search for Heavy Neutral Leptons in a liquid argon TPC [arXiv:1911.10545]. ● Platform to develop searches for baryon-number violation in the future DUNE. ● MiniBooNE low-energy excess may hide a new dark neutrino sector. ● Blooming phenomenology. Future opportunities: – Dark photon portal: dark matter production in meson decays in beam line. – Higgs portal: dark scalars produced in meson decays in beam line. – Neutrino magnetic transition moment. – Large extra-dimensions. – Milli-charged particles. José I. Crespo-Anadón BSM in MicroBooNE 19 Thank you for your attention! José I. Crespo-Anadón BSM in MicroBooNE 20 MicroBooNE Collaboration November 2019 University of Bern, Switzerland: Y. Chen, A. Ereditato, I. Kreslo, T. Mettler, J. Sinclair, M. Weber Brookhaven: M. Bishai, H. Chen, W. Gu, X. Ji, B. Kirby, Y. Li, X. Qian, B. Viren, H. Wei, C. Zhang University of California, Santa Barbara: X. Luo, N. Kaneshige, E. Yandel University of Cambridge: J. Anthony, P. Detje, A. Moor, A. Smith, M. Uchida University of Chicago: K. Miller, D.W. Schmitz University of Cincinnati: R.A. Johnson Colorado State University: I. Caro Terrazas, R. LaZur, M. Mooney Columbia University: L. Camilleri, D. Cianci, J. Crespo, Y.-J. Jwa, G. Karagiorgi, M. Ross-Lonergan, W. Seligman, M. Shaevitz, K. Sutton Davidson College: B. Eberly Fermilab: S. Berkman, D. Caratelli, R. Castillo Fernandez, F. Cavanna, G. Cerati, K. Duffy, S. Gardiner, E. Gramellini, H. Greenlee, C. James, W. Ketchum, M. Kirby, T. Kobilarcik, S. Lockwitz, A. Marchionni, T. Mohayai, O. Palamara, Z. Pavlovic, J.L. Raaf, A. Schukraft, E. Snider, P. Spentzouris, M. Stancari, J. St.