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NEUTRONS, PARTICLES, AND THE UNIVERSE

NEUTRONS, PARTICLES, AND THE UNIVERSE. Dirk Dubbers, U. Heidelberg. A. OVERVIEW. The ultimate aims of PARTICLE Physics :. Maxwell eqs., Schrödinger eq. electroweak eqs., quantum-chromodyn., ...  (works beautyf. ) gravitation, masses, charges, families,

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NEUTRONS, PARTICLES, AND THE UNIVERSE

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  1. NEUTRONS, PARTICLES, AND THE UNIVERSE Dirk Dubbers, U. Heidelberg ESS 17.05.2002 Neutron Particle Physics

  2. A. OVERVIEW The ultimate aims of PARTICLE Physics: Maxwell eqs., Schrödinger eq. electroweak eqs., quantum-chromodyn., ...  (works beautyf.) gravitation, masses, charges, families, ...(doesn't work yet) Derive the basic laws of nature … e.g. 'gauge invariance' implies  E = /0 E+Bt = 0 B = 0 c2BEt = j/0 … from simple symmetry principle(s) Link all this to cosmology: ESS 17.05.2002 Neutron Particle Physics

  3. ESS 17.05.2002 Neutron Particle Physics

  4. The role of the NEUTRON Beam energy in experiments:  High-energy particle physics at Tera-eV10+12 eV Studies on 2nd and 3rd particle families 3rd: b, t, ,  2nd: s, c, , Low-energy particle physics at Nano-eV10-9 eV Precision studies on 1st particle family1st: d, u, e,e ESS 17.05.2002 Neutron Particle Physics

  5. Sensitivity of neutron experiments: Energy:E ~ 10-22 eV Momentum:p/p = 10-11 Polarization:P ~ 10-7 Neutron exp’t: EDM: E/ ~ 1/month n-charge: 1Å on 10m P-violation: 0.000010 spinrot. Neutron-particle physics: free neutron provides more than two dozen observables Neutron Data Booklet 2002 addresses about two dozen • BASIC QUESTIONS from particle physics and cosmology: ESS 17.05.2002 Neutron Particle Physics

  6. B. SOME PAST ACHIEVEMENTS • WAS THERE A BIG BANG? redshifts and microwave- background pre-1990: 'soft' qualitative evidencefor Big Bang  1990: 'hard' numeric evidence for Big Bang: after 1 sec:freeze-out of neutron/proton ratio to 1/7: after 10 min:light-element abundances: relative to hydrogen n  p ESS 17.05.2002 Neutron Particle Physics

  7. .Light-element abundances depend on: • neutron lifetime  • neutrino cross-sections  1/ • number of particle families N • density  of (ordinary) matter in universe  n  p+e–+e* n+e p+e–  is universeopen, closed, or critical (flat) ? This makes: number of particle familiesN and density of the universe accessible to observation! But: Largest error is due to neutron lifetime From 4He yield: N = 13 / ln/0 = 20 / . · · . · · . . . · · . . . · .· . UCN Measurement of  in ultracold-neutron bottle Tn  1 mK Neutron lifetime : 1985: (925  11) s 1990: (889  3) s 2002: (885.8  0.9) s n = noexp(– t/) ESS 17.05.2002 Neutron Particle Physics

  8. HOW MANY FAMILIES OF PARTICLES POPULATE THE UNIVERSE? 1989: Big Bang result, with new neutron lifetime: N = 2.6  0.3 i.e. N is limited to 3 families.  Confirmed later by high-energy experiment: N = 3.00  0.02 now used as input in Big Bang calculations. Z0 - width at CERN This leaves the average densityof the universe as the only unknown parameter : ESS 17.05.2002 Neutron Particle Physics

  9. DOES THE UNIVERSE REACH ITS CRITICAL MASS? Answer: Yes, but not with ordinary matter! Density of ordinary matter  Critical  density Y /crit Present status: Neutron lifetime is still largest source of error in 4He-abundance calculation ESS 17.05.2002 Neutron Particle Physics

  10. CAN MATTER CHANGE INTO ANTIMATTER?  Neutrinos oscillate: e  , 'Lepton-number oscillations'mc2  0.05 eV 's -detection efficiency  1/ 'Strangeness oscillations' mc2  10-18 eV  Kaons oscillate: K  K*  Do neutrons oscillate n  n* (neutron  antineutron, 'n-nbar' ) 'Baryon-number oscillations' B = +1  -1 Baryon-number oscillations are allowed in some Grand-Unified Theories. ESS 17.05.2002 Neutron Particle Physics

  11. The antineutron detector Experimental limit: nn* > 2.9 years < nHn*>  10-23 eV (90% c.l.) Present: limit on neutron oscillations probes 105 GeV range Future: neutron-oscillation search with UCN ? ESS 17.05.2002 Neutron Particle Physics

  12. HOW ARE THE HEAVIER ELEMENTS FORMED IN SUPERNOVA EXPLOSIONS? Within seconds, solar-system masses are created in Super-Nova explosions. The field urgently needs neutron-nuclear data.(from neutron-fission products 'far-off stability') SuperNovae do explode, though not on the computer. • ON TOPOLOGICAL PHASES n(C)=  Cn(R)n(R)·dR Mathematical 'theories of connections' are right at the heart of avant-guard physics. 1984: Berry's theorems on 'topological phases' 1985: first measurements with polarized neutrons 1995: 'hidden symmetries' detected with microwaves 2000: theory of 'off-diagonal Berry Phases' developed 2001: first measurements with neutron interferometry ESS 17.05.2002 Neutron Particle Physics

  13. NEUTRON QUANTUM OPTICS R(3600) = -1 Aharonov-Bohm Aharonov-Casher squeezed states beat optics dressed neutrons optical pumping ... This, too, is a neutron:  = |I + II |2 Status: Non-classical states of neutrons and UCN can be produced and used in neutron-interferometry and spin-echo systems ESS 17.05.2002 Neutron Particle Physics

  14. HOW STRONG ARE NATURE'S FUNDAMENTAL FORCES? Neutrons are sensitive to all four forces of nature 1. THE 'WEAK' FORCE: Neutron-decay measurements: • neutron lifetime  = (885.8  0.9) s • electron-neutrino correlation a = -0.102  0.005 • beta asymmetry A = -0.1189  0.0007 • neutrino asymmetry B = 0.983  0.004 • triple-correlation D = -(0.55  0.95)10-3 . . . give nucleon-lepton weak-interaction coupling-constants: Vector: gV = (1.1470  0.0016)10-5 (c)3 GeV-2 Axial-vector: gA = (-1.4602  0.0008)10-5 (c)3 GeV-2 Phase(V-A): = 180.070  0.120. ESS 17.05.2002 Neutron Particle Physics

  15. Example: beta-asymmetry in neutron decay Experiment:   (= e-) neutrons  spin up   Detector Beam-time will start soon Problem is over-determined: precision tests beyond the Standard Model (see below) ESS 17.05.2002 Neutron Particle Physics

  16.  2. THE ELECTROMAGNETIC FORCE: The strength of the electromagnetic force is given by the fine-structure constant  = e2/c =(2Rh/mec)½ neutron measurements of: h/mn = (3.956 033 3  0.000 000 3)10-7 m2s-1 mn/mp = 1.001 378 418 87  0.000 000 000 58 give a model-independent value: -1 = 137.036 011  0.000 005 nvn = h/m, h = Planck's const. … plus R plus mp/me  is needed for precision tests of Standard Model example: magnetic moment of muon Theory (input ): g=2.002 331 8320(14) Experiment: 3 deviation? g=2.002 331 8404(30) Status: Neutron data give strengths of 2 of the 4 forces of nature ESS 17.05.2002 Neutron Particle Physics

  17. Neutron: gravitational force/inertial force:  = 1.00011  0.00017 3. THE GRAVITATIONAL FORCE: • IS FREE FALL A CONTINUOUS PROCESS? Quantization of UCN in the earth's gravitational field: Do neutrons fall in 'steps'? Answer: yes, they do! •_ _ _ 4. THE 'STRONG' FORCE:(see below) ESS 17.05.2002 Neutron Particle Physics

  18. C. ESS-FLAGSHIP EXPERIMENTS • DO THE STRONG AND ELECTROMAGNETIC FORCES ACT INDEPENDENTLY? Standard Model: strong interactions of proton-proton, proton-neutron, and neutron-neutron must all be equal. But: scattering lengths app = -23.82(1) fm anp = -17.1(2) fm  ESS FLAGSHIP: DIRECT MEASUREMENT OF NEUTRON - NEUTRON SCATTERING LENGTH ann UCN ? N.B.: n-n rate  (n-flux)2 ! Expected n-n scattering rate: several events per minute ESS 17.05.2002 Neutron Particle Physics

  19. WHY HAS SO MUCH MATTER SURVIVED THE BIG BANG? . ..qq*. Big Bang theory: matter and antimatter should annihilate each other vs. evidence:we exist explanation: violation of 'CP-symmetry' ? (Sacharow 1965) experimentum crucis: Electric Dipole Moment (EDM) of the neutron: if 'CP' explanation is right: EDM = 10-271 ecm = value required to explain our existence if 'CP' explanation is wrong: EDM = 10-321 e cm = value predicted by the Standard Model present experimental limit: EDM < 6.310-26e cm CPT=1 Ultracold neutrons ! - EDM + (90% c.l.) ESS 17.05.2002 Neutron Particle Physics

  20. ESS-FLAGSHIP: NEW TYPE OF ULTRACOLD NEUTRON (UCN) SOURCE  Solid-deuterium UCN-source Future: Question of dominance of matter over antimatter will be solved in the next twenty years. ESS should be in the game and provide strongest UCN source in the world. ESS 17.05.2002 Neutron Particle Physics

  21. IS THE LEFT-HANDEDNESS OF NATURE AN "EMERGENT PROPERTY"? Standard Model: Electroweak Interaction is 100% left-handed Did Universe start left-right symmetric, i.e. is left-handedness an 'emergent property' ? If so, then 'right-handed' heavy brother of W-boson must exist did parity violation arise as an order-parameter during a phase transition of the vacuum in the early universe Limits from neutron decay experiments: mass of right-handed W:mR > 280 GeV/c2 left-right mixing phase: -0.20 <  < 0.07 mL=81 GeV/c2 WL=W1cos–W2sinWR=W1sin+W2cos (90 % c.l.) Present: neutrons very competitive with high-energy work ESS 17.05.2002 Neutron Particle Physics

  22. ESS-FLAGSHIP: SPONTANEOUS TRANSFORMATION OF A FREE NEUTRON INTO A HYDROGEN ATOM Experimentum crucis: would isolate effect of right-handed boson Fast-hydrogen recoil detector n  H(2S) + e*mS:+½  +1 +½ (left-hd.) mS:+½  +1 –½ (right-hd.) Decay volume Cold neutrons Optical detection of Lyman- in fast coincidence Interesting event signature. Expected n  H rate: 10 events/minute Future: sensitive yes/no experiment on origin of P-violation ESS 17.05.2002 Neutron Particle Physics

  23. IS QUARK-MIXING DONE PROPERLY? When quarks are subject to electroweak force: 'down' = down + some strangeness + some bottomness 'strange' = strange+ some downness + some bottomness 'down' = down + some strangeness + some downness( with respect to 'mass eigenstates') quark mixing matrix is 'unitary' (pure rotation in 'flavor' space) Standard Model of Particle Physics requires: this 'quark-mixing' should be a zero-sum game From neutron decay experiments: 3.0 standard deviations from zero observed: = -0.0083  0.0028 Present: puzzling deviation from Standard Model ? ESS 17.05.2002 Neutron Particle Physics

  24. ESS-FLAGSHIP: THE ULTIMATE NEUTRON-DECAY CORRELATION EXPERIMENT ESS neutron long-pulset = 2 ms Beam chopper  = 4.5 Å,  = 1.5 Å I = 1.2 ·1010/s (peak) Free-neutron cloud N = 2·108 neutrons 103m/s Future: neutron decay at rate N/ =2·105/s studied under optimum conditions 107m/s time-average: 104/s present rate: 2 ·102/s Beam chopper B decay products locked to B-field e- and p+ detector time-gated ESS 17.05.2002 Neutron Particle Physics

  25. D. SUMMARY ESS 17.05.2002 Neutron Particle Physics

  26. E. CONCLUSION Neutron-particle and neutron-nuclear physics is a successful and growing field of neutron science. in recent years: + 4 university chairs + 4 associate profs. solely in D ESS WILL PROVIDE AN OPTIMAL TOOL FOR THEIR WORK. ESS 17.05.2002 Neutron Particle Physics

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