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Lecture II: Neutrons beyond the SM

Motivation Right-handed W bosons Classical theory of neutron decay Search for traces of W R in decay asymmetries CP violation beyond the SM Search for CP violation in neutron decay Electric dipole moments Measurement of the neutron EDM Baryon number violation

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Lecture II: Neutrons beyond the SM

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  1. Motivation Right-handed W bosons Classical theory of neutron decay Search for traces of WR in decay asymmetries CP violation beyond the SM Search for CP violation in neutron decay Electric dipole moments Measurement of the neutron EDM Baryon number violation Scenarios of Baryon number violation Search for neutron-antineutron oscillations Lecture II: Neutrons beyond the SM Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  2. (broken) SU(2)LSU(2)R deviation from maximal parity violation (V+A) additional phases for CP violation Leptoquark exchange additional phases for CP violation exotic couplings Exotic (non V,A) couplings scalar, tensor, or pseudo- tensor interactions Neutron Decay beyond the Standard Model Standard Model SU(2)L (V-A interaction) Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  3. Baryon number violation • Neutron-Antineutron-Oscillations • CP violation • Electric dipole moment • Triple correlations D or R of the decay products • Right-handed currents • Neutrino asymmetry B • CP-violating phases (dn, D, R) New interactions (SuSy…) new phases Baryon asymmetry Unification scenarios Left-right symmetric models Neutrons and New Physics • Search for processes which • are unobservably small in the SM • are not allowed in the SM • deviate observables from the SM values Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  4. Why should we search for CP or B violation? • Baryon Asymmetry in the Universe • Baryon number violation • C and CP violation • Thermal non-equilibrium • Standard Model • B violation in sphalerons (B–L conserved) • C violation in weak interaction • CP violation in Kaons, B mesons • Thermal non-equilibrium in electroweak phase transition A.D. Sakharov: JETP 5 (1967) 24 But Not enough CP violation for Baryogenesis Higgs boson too heavy to create first order phase transition New physics required Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  5. General Hamiltonian: Classical Theory of Weak Decay • Standard Model: Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  6. Surviving in the SM: Find the Parameters… J.D. Jackson et al.: Phys. Rev. 106 (1957) 517 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  7. or Test for right handed currents Find the Parameters… T violation beyond SM Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  8. SM + (V+A)-contributions + and ft(0+0+) and n Mainly B From K3, K2 From K3, K2 From K3, K2 Mainly A B = 0.983(4) [PDG 2004] B = 0.983(4) [PDG2004] B = 0.983(2) [just for fun] Example: Right-Handed Currents Standard Model (V-A) and n Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  9. Challenges in Neutron Decay Experiments Proton detection: Ep < 750 eV acceleration prior to detection special low noise detectors needed Electron detection: Ee < 780 keV typical energy of gamma background sophisticated techniques difficult Life time: =885.7(8) s Velocity: 1000 m/s only 10-7 of the passing neutrons decay, low statistics  all others can create background Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  10. B=0.98010.0046 Serebrov et al, JETP 86 (1998) 1074 Neutron Decay and Right-handed Currents Neutrino asymmetry World average: B = 0.983(4) Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  11. Detector function: Electron and proton in same detector How to Improve? Solid angle: Magnetic field 22 spectrometer Better statistical sensitivity Backscattering suppressed Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  12. Main limitations • Polarisation • Instable high voltage • Scintillator after pulses • High-voltage related background Ep < 750 eV from decay ~20 keV after acceleration) (4-5)20 keV in detector Serebrov et al, JETP 86 (1998) 1074 M. Kreuz et al, PLB 619 (2005) 263 B=0.9670.006stat0.010sys First Experiment (2001) Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  13. Electric dipole moment DSM10-12 DFSI=1.1·10-5Dexp10-3 dSM=10-33…10-31 ecm dexp10-25 ecm RSM10-12 RFSI=1·10-3Rexp(goal)510-3 Neutrons and CP (T) Violation Triple correlations in the decay Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  14. P conserving sensitive to V,A type T violating duee interactions • P violating sensitive to S,T type T violating duee interactions Left-right Exotic fermions Leptoquark • EDM more stringent for left-right, exotic fermions • D more stringent for leptoquark • Limits from P,T violating electron-nucleon interaction more stringent New T violation may contribute on the tree leveltheoretical uncertainties more reliable than for loop type contributions R & D D coefficient R coefficient Present sensitivity for D tests MX in TeV range P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413. Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  15. Measurement of D P violation  Asymmetry with spin-flip D = 0 in SM Principle Set-Up Breaking of detector symmetry Systematic effects Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  16. Measurement of D Optimise for Statistics Optimise for Systematics D = (–2.86.4stat3.0syst)·10-4 D = (–612stat5syst)·10-4 L.J. Lising et al, PRC 62 (2000) 055501. T. Soldner et al, Phys. Let. B 581 (2004) 49. Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  17. D & dn P. Herczeg, Prog. Part. Nucl. Phys. 46 (2001) 413. Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  18. Paramagnetic atoms and molecules Diamagnetic atoms (L = 0) Hadrons, in particular nucleons d(205Tl) < 910-25e cm d(199Hg) < 210-28e cm dn < 610-26e cm CP from electron EDM CP from CP-odd nucleon-nucleon interactions CP in quark sector Incomplete due to relativistic effects, net enhancement of atom EDM relative to electron EDM Incomplete due to finite size of nucleus; atom EDM still suppressed compared to nucleus EDM, but not fully Electric Dipole Moments Probe flavour-diagonal CP violation (negligible in the SM) Schiff’s theorem: Electric fields will be shielded by redistribution of electrons – no EDM of atoms Comparable sensitivity to fundamental CP violation, e.g. superpartner masses and CP-violating phases – complementary observables M. Pospelov & A. Ritz: hep-ph/0504231 W. Bernreuther & M. Suzuki: Rev. Mod. Phys. 63 (1991) 313 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  19. Paramagnetic atoms and molecules Diamagnetic atoms (L = 0) Hadrons, in particular nucleons d(205Tl) < 910-25e cm d(199Hg) < 210-28e cm dn < 610-26e cm EDM of unpaired electron Contributions from CP-odd electron-nucleon interactions (e.g. CP violation in Higgs sector) Apart from thisinsensitive to QCD effects Enhancement of de500, Even larger for molecules(e.g. YbF, PbO) CP-odd nuclear moments, caused by CP-odd nucleon-nucleon interactions or nucleons EDM In generalless important: de, electron-nucleon interaction Nuclear moment calculations very difficult; suppression of individual contribution by factor 100 due to cancellations dn composed of contributions from quarks and gluons No additional atomic or nuclear physics Electric Dipole Moments Probe flavour-diagonal CP violation (negligible in the SM) M. Pospelov & A. Ritz: hep-ph/0504231 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  20. At scales up to 103 TeV M. Pospelov & A. Ritz: hep-ph/0504231 Electric Dipole Moments Probe flavour-diagonal CP violation (negligible in the SM) Paramagnetic atoms and molecules Diamagnetic atoms (L = 0) Hadrons, in particular nucleons d(205Tl) < 910-25e cm d(199Hg) < 210-28e cm dn < 610-26e cm e electron q quarkG gluonN nucleond EDMdC chromo EDMMQM magnetic quadrupole moment S.M. Barr: Int. Journ. Mod. Phys. A 8 (1993) 209 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  21. Electro- 10-20 magnetic 10-22 SUSY 10-24 Neutron Multi Electron Higgs Left-Right 10-30 10-32 10-34 dn = –(1±3.6)10-26 e cm Standard Model de = (6.9±7.4)10-28 e cm 10-36 10-38 Neutron and Electron EDM EDMs in the SM Single CP-violating invariant: JCP = Im(VtbVtd*VcdVcb*)  310-5  Four electroweak vertices needed Quark & nucleon EDMs All EDM vanish on two-loop level Three-loop for quark EDM dqCKM 10-34 e cm Main contribution for dn from four-quark operator, enhanced by long-distance effects (pion loops) dnCKM 10-32 e cm Lepton EDMs Via diagrams with closed quark loops Non-vanishing only at four-loop level deCKM 10-38 e cm CKM-like phases in lepton sector, Majorana  deSeeSaw < 1.510-43 e cm (up to 1010 enhancement by fine-tuning) M. Pospelov & A. Ritz: hep-ph/0504231 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  22. CP Problems Strong CP Problem SuSy CP Problem CP violating contribution to QCD Lagrangian suppressed to < 10-9 – why? CP violating phases are smallOrSoft-breaking masses significantly larger than 1TeV Proposals: Axions CP or P exact symmetry at higher energy scale (e.g. some LR models) Proposals: Heavy superpartners Assume exact CP in soft-breaking sector Accidental cancellations M. Pospelov & A. Ritz: hep-ph/0504231 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  23. Measuring the Neutron EDM – Principle Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  24. B “Spin up” neutron... 1. Apply /2 spin flip pulse... 2. Free precession... 3. Second /2 spin flip pulse. 4. Measuring the Neutron EDM – Resonance Method Sensitivity • Visibility of resonance fringeE Electric field strengthT Time of free precessionN Neutron number Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  25. Four-layer mu-metal shield High voltage lead Quartz insulating cylinder Coil for 10 mG magnetic field Upper electrode Main storage cell Hg u.v. lamp PMT to detect Hg u.v. light Vacuum wall Mercury prepolarising cell RF coil to flip spins Hg u.v. lamp Magnet S N UCN guide changeover UCN polarising foil Ultracold neutrons (UCN) UCN detector The Rutherford-Sussex-ILL-Experiment • = 0.5E = 4.5 kV/mT = 130 s (time of cycle: 210 s)N = 13000 per bunch P.G. Harris et al. : NIM A 440 (2000) 479 Sensitivity improved steadily, 2003: Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  26. Rutherford-Sussex-ILL-Experiment – Hg Magnetometer In-situ measurement of magnetic field by observing precession of 199Hg atoms Precision: 2 nG per cycle (Neutron counting error: 10 nG per cycle) Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  27. Leakage currents Create additional magnetic field and precession Ileak 1nA  effect small Sparks Automatically identified and rejected by magnetometer vE effect Magnetic field in neutron rest frame due to electric field Averages out if there is no net rotational motion of neutrons Effects estimated to be below 10-26 e cm • Geometric phases • Caused by vE effect in combination with gradient of B • Works differently on n and Hg (velocity, distribution) • On Hg: 110-26 e cm (for 1nT/m) • On n: -110-27 e cm (for 1nT/m) Transfer more dangerous than direct effect on dn • Correction possible But dangerous for future projects M. Pendlebury et al. : PRA 70 (2004) 032102 Systematic Effects P.G. Harris et al. : PRL 82 (1999) 904 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  28. Neutron EDM – Projects New UCN sources Superfluid 4He RAL-Sussex-ILLLANCSE / SNS Solid D2 Paul Scherrer InstitutFRM II Munich Gain factors of 103 New n-EDM Projects RAL-Sussex-ILL: Cryo-EDM PSI-IN2P3-... LANSCE / SNS Attempted final precisions: 10-28 ecm Higher fields inside 4He New magnetometers RAL-Sussex-ILL Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  29. Idea: Use high electric field inside some crystalsup to 109 V/cm for certain crystalsand higher density of cold neutrons Prestudies at PNPI: Fedorov, Voronin et al. Not competitive with proposed UCN projects, but with existing oneCompletely different systematics, does not require magnetic field An Alternative – CrystalEDM? Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  30. Classes of B violation |B| = 2p + n  mesons (s) n  n |B| = 1p  leptons, n  leptons, p  mesons, n  mesons Probes high scales (GUT) Probes intermediate scales |(B – L)| = 0 |(B – L)| = 2 Neutrons and Baryon Number Violation Motivation – needed to create Matter-Antimatter-Asymmetry in Universe – implied by GUTs, SuSy, Left-Right-symmetric models Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  31. Today Interesting for GUT breaking schemes, e.g. (embedded in SO(10)): Neutrinos very light, required mass scale makes nn unobservable in these models Consider 2 large extra dimensions Fermion wave-functions localised Effective scale MI for n n: “Large class” of seesaw models for  masses allow observable n n Parity and (B – L) breaking close to conventional GUT scale 21016 GeV Majorana R mass and n n created by same operators SuSy seesaw Large extradims Relates (B – L) breaking, parity breaking, and small neutrino masses: nn observable for scale 100TeV K.S. Babu & R.N. Mohapatra: Phys. Lett. B 518 (2001) 269 S. Nussinov & R. Shrock: Phys. Rev. Lett. 88 (2002) 171601 Models with n n Traditional Review: R.N. Mohapatra: NIM A 284 (1989) 1 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  32. Neutrons in Medium / Field Numbers 5 B = 0 B = 20nT (2.410-15eV) B = 400nT (4.810-14eV) Earth:  50T (310-12eV) 0.1s free flight (100m at 1000 m/s)Flux 1011 n/sObservation time 1 day 4 3 Pn[10-16] B < 10nT (0.1mG)Vacuum < 10-4 mbar Inside nucleus:V  500 MeV (could also change m) 2 1 0 0 0.02 0.04 0.06 0.08 0.10 0.12 0.14 t [s] Phenomenology of nn Free neutrons Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  33. nn – Experiment Analysis by -event visible energy -TOF between SCs -vertex reconstruction 1011 n/s 600 m/s, 81 m free flight B < 10 nT (Mumetal) p < 10-4 mbar 200 m C target Effective running time 280 days M. Baldo-Ceolin et al: Z. Phys. C 63 (1994) 409 Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  34. nn with UCNs? nn in Nuclei Cold neutrons t 0.1 sUCNs t 800 s But: n phase is absorbed and reset in wall collision Inside nucleus: V  500 MeVInteraction can change m Very optimistic Numbers • Require model-dependent corrections for nuclear effects 0.2s free flight (1m at 5 m/s)800 s storageDensity 104cm-3, 1m3Observation time 1 day Soudan 2 iron tracking calorimeter (5.6 kTyr): TFe > 7.21031yr 0.1s free flight (100m at 1000 m/s)Flux 1011 n/sObservation time 1 day J. Chung et al.: Phys. Rev. D 66 (2002) 032004 Background limited! Same number of neutrons/s in very opti-mistic UCN scenario, only gain: (tfree/t)1/2 Other Methods Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  35. Precise absolute measurements of SM observables and consistency checks Beta asymmetry, Antineutrino asymmetry, Lifetime Search for right-handed currents below 1TeV Search for effects unobservably small in the SM (deviations from 0) CP violation in the decay Search for leptoquarks (up to 10 TeV) CP violation in electric dipole moment Search for new phases due to SuSy, LR, exotic fermions (1 to 103TeV) Search for processes forbidden in the SM Neutron-antineutron oscillations  Test of intermediate unification (B-L, LR) scale at 100TeV Nothing found yet, but this is already something… Summary – Neutrons beyond the Standard Model Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  36. The Neutron Guide to the Universe New Physics Standard Model 1019 GeV Planck GUTs - - Temperature Inflation Electroweak Chiral transition Nucleon freeze out Nuclear freeze out Atomic freeze out Galactic freeze out 10-11 GeV 1 s 10-43 s 10-35 s 10-12 s 105 y 109 y today Time Instead of E E/E0 Neutron energies: peV…meV Decay energy: 780 keV Diagram from D. Dubbers Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

  37. The Neutron Guide to the Universe  Gravitational/inertial mass g Magnetic monopole moment dn Electric dipole moment nn Neutron-antineutron oscillation time  CP violating phase in decay mW, WR-WL mixing parameters qn Neutron charge aWM Strength of weak magnetism  Ratio of axial vector to vector coupling N Nucleon-neutrino scattering cross section N Number of light neutrino families Vud Quark mixing element pp Weak interaction in proton-proton interaction n Electric polarisibility of the neutron A, P Parity violating correlations in n-Nucleon and n-Nucleus interactions  Fine structure constant Particle Physics with Slow Neutrons II LNGS Summer Institute, September 2005 Torsten Soldner

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