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Measures in the distant past precision measurements: what do they provide? precision experiments part of large facilities precision experiments with neutrons.

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Presentation on theme: "Measures in the distant past precision measurements: what do they provide? precision experiments part of large facilities precision experiments with neutrons."— Presentation transcript:

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

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

3 precision experiments: measurements measurements: to add to academic interests deduce earth curvature by angle of sunlight 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 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 (G F, ,... )  signals of rare events, breaking of laws and symmetries,... particle physics:  masses and lifetimes of particles (quarks, leptons, hadrons,...)  matrix elements of transitions (CKM, PMNS, nuclear trs,...)  forces and couplings in reaction processes (G F, ,... )  signals of rare events, breaking of laws and symmetries,... goes hand-in-hand with ever more precision calculations goes hand-in-hand with ever more precision calculations proton lifetime neutron lifetime (V ud ) neutron decay neutrinoless  -decay

5 precision experiments: proton decay Standard Model describes the change of quark colour and flavour and lepton conversion through gauge bosons g, W ±, Z 0 Standard Model describes the change of quark colour and flavour and lepton conversion through gauge bosons g, W ±, Z 0 d u sdusdu uduudu e-e- νeνe Λ0Λ0 p ( Baryon number B and lepton number L conserved ) decay rate as function of energy T, coupling constant G:

6 precision experiments: proton decay new allowed processes: p → π 0 + e + new allowed processes: p → π 0 + e + GUT mechanisms in models quarks and leptons incorporated into common families (e.g. e + with d): interaction with new gauge bosons (X, Y) masses M X ~ GeV, coupling g U ~ 1/42 ( Baryon number B and lepton number L NOT conserved ) into specific channel:

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

8 precision experiments: proton decay 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 10 6 event triggers per day: background from cosmic rays flashing PMT’s radioactivities p → π 0 + e +  surviving events: precision measurement constraining GUT’s

9 precision experiments: lepton g 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 a e Formulation of QED with first order radiative correction 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 a e Formulation of QED with first order radiative correction six orders of magnitude improvement in precision expt s and theoretical calculation six orders of magnitude improvement in precision expt s and theoretical calculation testing the Standard Model to its limits, discovery of new interactions beyond SM testing the Standard Model to its limits, discovery of new interactions beyond SM

10 protons target pions muons detectors muon decay to electron precision experiments: lepton g-2 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 detecting a signal of the muon spin in forward direction signal oscillates with spin precession frequency of muon Muon g-2 experiment Brookhaven

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

12 precision experiments: lepton g-2

13 first signs of deviation of 2.6σ from Standard Model description? not quite... error in experimental analysis code first signs of deviation of 2.6σ from Standard Model description? not quite... error in experimental analysis code SM Experiment March 2001 PRL six orders of magnitude improvement in precision expt s opening a window to beyond SM physics phenomena six orders of magnitude improvement in precision expt s 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 correlation electron and anti-neutrino momentum neutron beta decay experiment: correlation coefficients between particles spin and momenta coupling constants correlation electron momentum – neutron spin free neutron decay lifetime from muon decay ratio axial-vector / vector coupling constant

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

17 Spectra for both spin states B. Maerkisch, PERKEO III : Neutron Decay Measurements 2002: result: A = (8) = (19) 2006: result: A = (5) = (13) testing the CKM matrix of Standard Model precision experiments: neutron correlation parameter experiments

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

19 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 measurement of proton energy spectrum precision experiments: neutron correlation parameter experiments

20 a = ± , λ = ± measurement of decay proton integrated energy spectrum fit curve to energy spectrum as function of a: no competition for A measurement but independent method

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

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

23 τ n = ± 3.4 s. 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 precision experiments: neutron lifetime experiments ρ = (39.30 ± 0.10) µg/cm 2 6 Li density σ = (941.0 ± 1.3) b absorption cross section at 2200 m/s Ω/4π = ± 0.1% fractional solid angle detector the neutron lifetime experiment: NIST neutron flux monitor: n + 6 Li→ 3 H + 

24 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 the neutron lifetime experiment: stored ultra-cold neutrons UCN detector two storage chamber configurations: different surface exposure

25 precision experiments: neutron lifetime experiments 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 the neutron lifetime experiment: stored ultra-cold neutrons

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 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 precision experiments: neutron lifetime experiments

29 measurements / error bars incompatible, to be continued...

30 the neutron lifetime experiment: stored ultra-cold neutrons precision experiments: neutron lifetime experiments

31 V ud from neutron and nuclear beta decay =G A /G V Perkeo result: A 0 = (7) = (19)  n = (885.7  0.7) s world average  n = (878.5  0.7 st  0.3 syst ) s “Gravitrap” result

32 P & T violation CPT conservation  CP violation Electric Dipole Moment: neutron is electrically neutral If average positions of positive and negative charges do not coincide: EDM d n + - T reversal dndn S electric dipole moment d n spin S + - dndn S + - P transform. dndn S + - dndn S - + precision experiments: neutron electric dipole moment 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

33 Compare the precession frequency for parallel fields:  =  E  /h = [-2B 0  n - 2Ed n ]/h to the precession frequency for anti-parallel fields  =  E  /h = [-2B 0  n + 2Ed n ]/h The difference is proportional to d n and E: h(  -  ) = 4E d n Experiments: Measurement of Larmor precession frequency of polarised neutrons in a magnetic & electric field  : polarisation product E: electric field T: observation time N: number of neutrons nEDM: measurement principle

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

35 N S 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 Hg u.v. lamp RF coil to flip spins Magnet UCN polarising foil UCN guide changeover Ultracold neutrons (UCN) UCN detector nEDM at ILL: scheme used

36 nEDM at ILL: set-up room temperature experiment

37 nEDM at ILL: normalised frequency measurement

38 nEDM at ILL: performance room temperature experiment

39 d n = 1 e  cm year of publication Experiment Theory Neutron EDM upper limit [e  cm] Progress at ~ order of magnitude per decade Standard Model out of reach Severe constraints on e.g. Super Symmetry |d n |< 3 x e  cm nEDM: experiment vs theory

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


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