measures in the distant past precision measurements: what do they provide?

1. Precision experiments • practical tools • scientific: • test of theoretical models, existing laws of physics • confirm and/or constrain models • potential to discover (interactions, particles, ...) Electroweak precision experiments • measures in the distant past • precision measurements: what do they provide? • precision experiments part of large facilities • precision experiments with neutrons proton decay measurements muon decay measurements • neutron decay measurements • lifetime experiment • correlation parameters between neutron • and decay products • neutron electric dipole moment experiments

2. precision experiments: measurement tools measures: a practical tool define a length on the basis of a common feature ~ 3400 BC 1 cubit Royal cubit stick Giza pyramids sides built on the basis of the cubit to a precision of 0.05%!!!

3. precision experiments: measurements measurements: to add to academic interests deduce earth curvature by angle of sunlight • 250 BC - Eratosthenes: • In Syene ~5000 stadia south of Alexandria • sunlight shining directly down well shafts • in Alexandria light measured to be at 7 angle • ~5000 × 360/7 = 252,000 stadia (of the order of 40,000 km) - (cf 40,030 km)

4. precision experiments: particle physics Scientific precision experiments: testing the limits of our description and understanding of nature • particle physics: • masses and lifetimes of particles (quarks, leptons, hadrons, ...) • matrix elements of transitions (CKM, PMNS, nuclear trs, ...) • forces and couplings in reaction processes (GF, , ... ) • signals of rare events, breaking of laws and symmetries, ... • proton lifetime • neutron lifetime (Vud) • neutron decay • neutrinoless-decay goes hand-in-hand with ever more precision calculations

5. precision experiments: proton decay Standard Model describes the change of quark colour and flavour and lepton conversion through gauge bosons g, W±, Z0 d u decay rate as function of energy T, coupling constant G: νe s d u e- Λ0 ( Baryon number B and lepton number L conserved ) u d u p

6. precision experiments: proton decay GUT mechanisms • in models quarks and leptons incorporated into common families (e.g. e+ with d): • interaction with new gauge bosons (X, Y) • masses MX ~ 1015GeV, coupling gU ~ 1/42 new allowed processes: p → π0 + e+ ( Baryon number B and lepton number L NOT conserved ) into specific channel:

7. precision experiments: proton decay 11,200 PMTs detecting e and  50,000 tonnes of ultra-pure water, 1000m underground in the Kamioka Mine Super kamiokande: neutrino oscillation experiment • (100 km < L < 10,000 km) • neutrino flavour states mix, neutrino’s are massive Super kamiokande: use data to look for proton decay events

8. precision experiments: proton decay p → π0 + e+ • 106 event triggers per day: • background from cosmic rays • flashing PMT’s • radioactivities • analyse all data to look for electron signals: • in the correct energy range • total invariant mass per event determined • in the correct momentum range • from the correct part of detector • 18816 surviving events: precision measurement constraining GUT’s

9. precision experiments: lepton g-2 • 1927 Dirac intrinsic angular momentum and magnetic moment • of electron quantified • measurements of g factors pushed further development of QED • May and November 1947 electron g factor measurement different • from 2: g factor anomaly ae • Formulation of QED with first order radiative correction six orders of magnitude improvement in precision expts and theoretical calculation testing the Standard Model to its limits, discovery of new interactions beyond SM

10. precision experiments: lepton g-2 Muon g-2 experiment Brookhaven target • 24 GeV proton focused on nickel target generates pions • pions decay to polarised muons and are injected in storage ring • decay electrons emerge preferentially in direction of muon spin • detect those electrons with high enough energy to be in the direction of the muon motion protons muons pions detectors muon decay to electron detecting a signal of the muon spin inforward direction signal oscillates with spin precession frequency of muon

11. precision experiments: lepton g-2 Brookhaven National Lab: 3 GeVmuons stored in 14 m dia. ring in 1.45 T field • muon has orbital motion in magnetic field • at cyclotron frequency ωC • spin has precession frequency ωS • relative precession of S with respect to velocity • of muon: ωS-ωC direct relationship between ωD and a

12. precision experiments: lepton g-2

13. precision experiments: lepton g-2 first signs of deviation of 2.6σ from Standard Model description? not quite... error in experimental analysis code March 2001 PRL SM Experiment six orders of magnitude improvement in precision expts opening a window to beyond SM physics phenomena

14. precision experiments: neutron decay • neutron beta decay experiment: • Standard Model precision measurements • precision tests on unitarity of the CKM matrix • cosmological significance neutron decay probability, function of particles momenta, spin, correlation coefficients

15. precision experiments: neutron decay parameters • neutron beta decay experiment: • correlation coefficients between particles spin and momenta • coupling constants correlation electron momentum – neutron spin correlation electron and anti-neutrino momentum ratio axial-vector / vector coupling constant free neutron decay from muon decay

16. precision experiments: neutron correlation parameter experiments measurement of λ the “A” experiment: correlation electron momentum – neutron spin • polarised neutrons • electron detection with respect to neutron spin direction

17. Spectra for both spin states 2002: result: A = -0.1189(8)  = -1.2739(19)2006: result: A = -0.1198(5)  = -1.2762(13) testing the CKM matrix of Standard Model B. Maerkisch, PERKEO III : Neutron Decay Measurements

18. precision experiments: neutron correlation parameter experiments the “a” experiment: correlation electron-neutrino momentum proton energy spectrum depends on a measurement of λ p • neutrons (unpolarised) • proton detection, energy measurement p neutrons energy ~ meV, energy release ~MeV n n e- e- proton energy depends on angle between electron and anti-neutrino

19. precision experiments: neutron correlation parameter experiments measurement of proton energy spectrum • Penning trap • proton detection, energy measurement cold neutrons pass through volume between two electrodes, kept in a magnetic field decay protons trapped and orbit around magnetic field lines open trap by lowering voltage on gate electrode repeat sequence for mirror voltages ranging 0V to 800 V

20. precision experiments: neutron correlation parameter experiments measurement of decay proton integrated energy spectrum fit curve to energy spectrum as function of a: no competition for A measurement but independent method a = -0.1054 ± 0.0055, λ = 1.271 ± 0.018

21. precision experiments: neutron lifetime experiments the neutron lifetime experiment: • precision tests on unitarity of the CKM matrix • cosmological significance • neutrons (of cold or ultra-cold energy) • detect decay products or detect surviving neutrons • experiment at NIST - USA: • beam of cold neutrons • neutrons pass through penning trap • decay protons recorded

22. precision experiments: neutron lifetime experiments the neutron lifetime experiment: NIST superconducting magnet 3T incoming neutron beam solid-state charged particle detector high voltage (27 kV) cage for proton acceleration

23. precision experiments: neutron lifetime experiments • need to know neutron flux to very high precision • need to know trap volume to high accuracy • need to know efficiency of detectors to high accuracy • need to collect many events for statistical precision the neutron lifetime experiment: NIST neutron flux monitor: n + 6Li→3H +  • ρ = (39.30 ± 0.10) µg/cm26Li density • σ = (941.0 ± 1.3) b absorption cross section at 2200 m/s • Ω/4π = 0.004196 ± 0.1% fractional solid angle detector τn = 885.5 ± 3.4 s.

24. precision experiments: neutron lifetime experiments the neutron lifetime experiment: stored ultra-cold neutrons • experiment at ILL: • ultra-cold neutrons guided into storage chambers • seal chamber and store neutrons for a period T • open chamber to neutron detector and count remaining neutrons • repeat cycle for different storage periods T two storage chamber configurations: different surface exposure UCN detector

25. precision experiments: neutron lifetime experiments the neutron lifetime experiment: stored ultra-cold neutrons • need to know neutron flux stability • need to know neutron loss mechanism during storage • need to collect many events for statistical accuracy • different detection efficiencies for two chamber configurations ± 0.36 s • uncertainty in shape of chamber • statistical uncertainty

26. precision experiments: neutron lifetime experiments • experiment at ILL: • ultra-cold neutrons guided into storage chambers • seal chamber and store neutrons for a period T • open chamber to neutron detector and count remaining neutrons • repeat cycle for different storage periods T and different energies the neutron lifetime experiment: stored ultra-cold neutrons

27. precision experiments: neutron lifetime experiments

28. precision experiments: neutron lifetime experiments the neutron lifetime experiment: stored ultra-cold neutrons • latest result too far off to be included in average, now additional measurement: • polarised ultra-cold neutrons guided into storage chambers • seal chamber and store neutrons for a period T • open chamber to neutron detector and count remaining neutrons • repeat cycle for different storage periods T

29. precision experiments: neutron lifetime experiments measurements / error bars incompatible, to be continued...

30. Vud from neutron and nuclear beta decay n = (878.5  0.7st 0.3syst) s “Gravitrap” result n = (885.7  0.7) s world average Perkeo result: A0 = -0.1189(7)  = -1.2739(19) =GA/GV

31. precision experiments: neutron electric dipole moment + + T reversal - - S dn S dn electric dipole moment dn spin S - Electric Dipole Moment: neutron is electrically neutral - + P transform. S S dn dn + - If average positions of positive and negative charges do not coincide: P & T violation CPT conservation  CP violation EDM dn + CP violation in Standard Model generates very small neutron EDM Beyond the Standard Model contributions tend to be much bigger neutron a very good system to look for CP violation beyond the Standard Model

32. nEDM: measurement principle Compare the precession frequency for parallel fields:  = E/h = [-2B0n - 2Edn]/h to the precession frequency for anti-parallel fields  = E/h = [-2B0n + 2Edn]/h : polarisation product E: electric field T: observation time N: number of neutrons Experiments: Measurement of Larmor precession frequency of polarised neutrons in a magnetic & electric field The difference is proportional to dn and E: h( - ) = 4E dn

33. nEDM: measurement principle “Spin up” neutron... 1. Apply /2 spin flip pulse... 2. Free precession... 3. Second /2 spin flip pulse. 4.

34. nEDM at ILL: scheme used 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

35. nEDM at ILL: set-up room temperature experiment

36. nEDM at ILL: normalised frequency measurement

37. nEDM at ILL: performance room temperature experiment

38. nEDM: experiment vs theory Experiment Theory 10-19 10-20 10-21 10-22 10-23 10-24 10-25 10-26 10-27 10-28 10-19 10-20 10-21 10-22 10-23 10-24 10-25 10-26 10-27 10-28 10-29 10-30 10-31 10-32 10-33 10-34 10-35 Neutron EDM upper limit [ecm] 1960 1980 2000 year ofpublication |dn|< 3 x 10-26ecm Progress at ~ order of magnitude per decade Standard Model out of reach Severe constraints on e.g. Super Symmetry dn = 1 ecm

39. precision experiments we have seen: • precision measurements examples • neutron electric dipole moment experiments • neutron lifetime & correlation experiment • anomalous g-factor (g-2) • decay experiments (p, double beta) • test of theoretical models, existing laws of physics • confirm and/or constrain models • potential to discover (interactions, particles, ...) these can: current precision experiments: mostly indirect measurements a very powerful tool to probe theories and their limits revealing signatures of new physics