Prospects and progress: new experimental searches for - PowerPoint PPT Presentation

Prospects and progress: new experimental searches for neutron-antineutron oscillations and related probes for new physics INT-17-69W A. R. Young Neutron Oscillation: appearance NCSU disappearance and baryogensis Thanks to J. Barrow, M. Frost, Y. Kamyshkov, G. Brooijmans, for slides PPSN 2018 ILL, May 24, 2018

Outline • Oscillations in Neutral Systems and B Violation • Current Limits • A Next Generation Experiment at the ESS • Our Focus Now A. R. Young PPNS 2018 2

Central Questions for the Standard Model Vincenzo Cirigliano’s talk on BSM physics and Josh’s talk on NNbar in DUNE A. R. Young PPNS 2018 3

Central Questions for the Standard Model Sources of Baryon Number Violation A. R. Young PPNS 2018 4

Central Questions for the Standard Model Sources of Baryon Number Violation The cosmological baryon asymmetry A. R. Young PPNS 2018 5

Central Questions for the Standard Model Pattern of charges Sources of Baryon and masses for the Number Violation SM Fermions The cosmological baryon asymmetry A. R. Young PPNS 2018 6

Central Questions for the Standard Model Pattern of charges Sources of Baryon and masses for the Number Violation SM Fermions The cosmological baryon Origins of neutrino asymmetry mass A. R. Young PPNS 2018 7

Central Questions for the Standard Model All Connected by models at higher energy scales … Observable N-N oscillations in a next generation experiment!

Example: Baryogensis • Not enough CP violation in the quark sector for baryogenesis • Baryon number violation required • Accidental symmetry in SM, so possible in the SM through B-L conserving excitations Also fjnd B-violation in GUTS (sphalerons) ΔB=1: p decay → Λ > 10 13 T eV • Many models exploit: strong exptl limits… → electrowk scale (SUSY) & B-L? → leptogenesis and B-L? ΔB=2: not constrained by p decay Provides viable path to observed BAU through, e.g. Post Sphaleron baryogenesis! A. R. Young

Experimental Probes for Baryogenesis models Very limited selection! • Direct particle production at LHC - LHC measurements already putting pressure on EW scale models like MSUSY and RPV SUSY predictions - (It’s also true that high scale models provide new observables potentially discoverable at the LHC or LHC-u like di-quarks and the scalars in PSB models) • EDMs probe CP violation • Neutrino oscillations probe CP-phases in PMNS matrix Can add to this short list... N- N Important and unique process to probe B B violation and baryogenesis oscillations mechanisms at relevant energy scales Cold Neutron Beams ofger a clean and powerful probe for this physics with factor of 1000+ gain in sensitjvity possible! A. R. Young PPNS 2018 10

The Power of Oscillations • Neutral particle oscillations have played a huge role in particle physics • K 0 -K 0 oscillations (ΔS = 2) central to understanding CP-violation in SM • B meson oscillations (ΔB = 2) - Sensitive to CKM elements and CP-violation Sensitive to top mass (m t 2 /m W 2 ) - → fjrst indication of top mass 1987 • Neutrino oscillations provided breakthroughs in understanding the neutrino sector - Initial indication of non-zero mass - Current suggestion of CP-violating phases Somewhat natural to expect that N-N oscillations can provide extremely sensitive probe for new physics. In fact, current sensitivity to couplings of order 4x10 -23 eV (comparable to EDM measurements)... A. R. Young PPNS 2018 11

Process, Critical Parameters Current limit on α ≈ 4×10 -29 MeV, or τ nn = ħ/α ≈ ~1×10 8 s (free neutron) • Potential V: - Nuclear potential ≈ 100 MeV - μ n · B earth ≈ 10 -18 MeV • Strongly suppressed unless quasi- free condition holds (Vt/ħ << 1) - Free neutron experiment requires substantial cancellation of B earth - Free neutron result can be cross-checked with magnetic fjeld (“switch ofg” oscillations with B earth ) A. R. Young PPNS 2018 12

Current Limits Baldo-Ceolin et al, Z.Phys. C63 (1994) 409-416 • Nt 2 = 1.5 10 9 s 2 , P < 1.6 10 -18 (run lasted ~1 year) and τ > 0.86 10 8 s • Many subtle optjmizatjons to minimize losses and backgrounds • CN integrated beam fmux was 1.25 × 10 11 n/s • Experiment was background-free • Bound neutron limits ~3 tjmes betuer • Many consideratjons make these measurements complementary to free neutron oscillatjons

Limits for Intranuclear Decays from Underground Experiments Josh Barrow’s presentation! Free neutron No background beam search R Ox = 5×10 22 s -1 goal at European Spallatjon Source Model dependent CNN DUNE analysis input → R “suppression factor”  Currently limited by atmospheric neutrino backgrounds  Decay products signifjcantly “processed” by heavy nuclei – background rejectjon challenging! A. R. Young PPNS 2018 14

Limits for Intranuclear Decays from Underground Experiments Josh Barrow’s presentatjon! Free neutron R Ox = 5×10 22 s -1 0 background beam search goal at European Spallatjon Source Model dependent CNN DUNE analysis input → R “suppression factor” → Other exotjc decay modes have very similar signatures Intranuclear decay → Nuclear Environment can result in suppression or measurements enhancement in some models complementary to A. R. Young PPNS 2018 CN beams! 15

Next Generation Free Neutron Experiment

Next Generation Free Neutron Experiment  Increase number of neutrons  Increase tjme of fmight  Keep (or increase) detectjon effjciency (50%)  Keep background at zero (need improved dets!)  Betuer B Earth suppression

Next Generation Free Neutron Experiment • Increase number of neutrons • Moderator brightness • Longer run • Moderator area Optjmizatjon requires • Angular acceptance remarkable facility... • Increase tjme-of-fmight • Longer beamline • Colder neutrons • Keep (or even increase) detectjon effjciency (~50%), keep background at ~0 • Exploit current, established hardware and sofuware technologies • Betuer B Earth suppression • Improved passive (+ actjve) shield

European Spallation Source 19

Preparations to test accelerator systems at end of summer are under way and the slab for the accelerator-to-monolith structure was just poured… 2.0 GeV superconducting linac, 14 Hz, 5 MW 20

Commissioning:  Very bright, “pancake moderator” in top position protons Unprecedented opportunity:  Lower moderator volume available for optimized (LD 2 ?) source for N-Nbar  Large beam port allows, in principle, roughtly 2 orders of magnitude more integrated fmux in beam! and space for 200m beam-line ...

ESS Timeline • 2014: ESS construction start Current plan: • 2019-2022: Initial phase: commissioning, intensity ramp, experiments by friendly users • 2023-2025: Initial user program operations: reliable operations with public users; establish basis for future cost sharing – full instrument set is 22 instruments – 15 instruments are under construction – 8 instruments are part of “hot commissioning” in 2022 N-Nbar@ESS 2018–2025:  – R&D as a part of joint ANNI/HI-BEAM instrument proposal – develop full proposal compatible with as-built ESS 2025+: Mount experiment!  22

Beam-line and Detectors Neutron-Anti-Neutron Oscillation 2 Gustaaf Brooijmans Search 3

Next Generation Free Neutron Experiment • Increase number of neutrons • Moderator brightness • Longer run • Moderator area • Angular acceptance • Increase tjme-of-fmight • Longer beamline • Colder neutrons • Keep (or even increase) detectjon effjciency (~50%), keep background at ~0 • Exploit current, established hardware and sofuware technologies • Betuer B Earth suppression • Improved passive (+ actjve) shield

Conceptual Design See e.g. NNbarX (Babu et al.), htup://arxiv.org/abs/arXiv:1310.8593 • High-m super-mirror • Residual B fjeld < 5 nT • Good vacuum < 10 -5 Pa MC optjmizatjon of parameters ongoing! 25

Supermirror Reflector • Crucial in acceptance gain • 2D, so acceptance scales quadratjcally • Modern multj-layer supermirrors have good refmectjvity at increasingly large momentum transfers (Swiss Neutronics) Actjve R&D at Nagoya University, with devices used at JPARC Ni refmectjvity → 0 defjnes m=1 26

Next Generation Free Neutron Experiment • Increase number of neutrons • Moderator brightness • Longer run • Moderator area • Angular acceptance • Increase tjme-of-fmight • Longer beamline • Colder neutrons • Keep (or even increase) detectjon effjciency (~50%), keep background at ~0 • Exploit current, established hardware and sofuware technologies • Betuer B Earth suppression Current work characterizing Current work characterizing • Improved passive (+ actjve) shield magnetjc noise magnetjc noise

Detector • Antj-neutron annihilatjon target • High annihilatjon probability, low Z, high transparency to neutrons • ILL experiment used a carbon foil, 130 μm thick • Annihilatjon produces pions, <n> ~ 5 • Background suppression: • Precise annihilatjon vertex identjfjcatjon of multjtrack events • Good mass and positjon resolutjon • Beam tjme structure? (Mainly for background control samples) 28

Detector cosmic veto cosmic veto Neutron-Anti-Neutron Oscillation 2 Gustaaf Brooijmans Search 9