TWIS T TWIS T TWIS T TWIS T The TRIUMF Weak Interaction Symmetry - PowerPoint PPT Presentation

TWIS T TWIS T TWIS T TWIS T The TRIUMF Weak Interaction Symmetry Test Precision Muon Decay at TRIUMF Nathan Rodning University of Alberta TWIST: Universities of Alberta, British Columbia, Northern British Columbia, Montreal, Saskatchewan; TRIUMF, Texas A&M, Valporaiso, KIAE - Russia

TWIS T TWIS T - TWIS T TWIS T - Personnel Personnel TRIUMF Alberta Regina Willy Andersson Andrei Gaponenko Ted Mathie � � � � Yuri Davydov � Peter Green George Price � � Jaap Doornbos � Peter Kitching � Roman Tacik � Wayne Faszer Rob MacDonald Saskatchewan � Dave Gill Maher Quraan Bill Shin � � � � Peter Gumplinger � Nathan Rodning Texas A&M � Richard Helmer � John Schaapman � Carl Gagliardi � Robert Henderson Farhana Sobratee � John Hardy � John Macdonald Jan Soukup Jim Musser � � � � Glen Marshall � Glen Stinson � Robert Tribble � Art Olin British Columbia � Maxim Vasiliev � David Ottewell Blair Jamieson Valparaiso � Robert Openshaw Doug Maas Don Koetke � � � � Jean-Michel Poutissou � Mike Hasinoff � Robert Manweiler � Renee Poutissou Northern British Columbia � Paul Nord � Grant Sheffer � Elie Korkmaz � Shirvel Stanislaus Hans-Christian Walter Tracy Porcelli KIAE (Russia) � � � Dennis Wright Montreal � Arkadi Khruchinsky � Pierre Depommier � Vladimir Selivanov � Vladimir Torokhov � Students � Professional Staff NL Rodning, University of Alberta - February 2001 2

Outline Outline � Background on muon decay � The E614 Experiment � Sensitivity to new physics NL Rodning, University of Alberta - February 2001 3

µ decay The Standard Model for µ decay The Standard Model for e ± ν W ± ν µ ± Only one coupling is non-zero in the Standard Model (V-A) Interaction is built in V ≡ S | | 0 T ≡ g = | | 0 | | g RR g zero - parity violation is perfect RR RR V ≡ S | | 0 T ≡ g ≡ | | 0 | | 0 g LR g LR LR - exchange particle is known V ≡ | | 0 S ≡ g T ≡ | | 0 | | 0 g g RL RL RL S ≡ T = V ≡ | | 0 | | g g zero | | 1 g LL LL LL NL Rodning, University of Alberta - February 2001 4

� The operator (V-A) satisfies the requirement that the Weak interaction violates parity. � (V-A) violates parity perfectly � The (V-A) operator projects out the left-handed (negative chirality) component of the wave function ψ ⎡ ⎤ + ψ γ µ − γ ψ = ψ γ µ − γ 5 5 ( 1 ) ( 1 ) ⎢ ⎥ ψ ⎣ ⎦ − ψ ⎡ ⎤ ⎡ ⎤ 0 0 + = ψ γ µ = ψ γ µ ψ ⎢ ⎥ ⎢ ⎥ − ψ ⎣ ⎦ ⎣ ⎦ 0 1 − � the (V-A) theory therefore states that leptons with positive chirality do not undergo weak interactions. NL Rodning, University of Alberta - February 2001 5

A more general interaction - which does not presuppose the W ν e ± µ ± ν ∑ γ γ ψ Γ ψ ψ µ Γ ψ 2 ~ | | rate g ν ν γ µ ij ei j e γ = , , S V T = ψ ψ , , i j R L Scalar µ ψ γ ψ Vector Allows for possible µν ψ σ ψ Tensor µ 5 ψ γ γ ψ - scalar Axial Vector 5 ψ γ ψ Pseudoscal ar - vector - tensor interactions of right-handed and left-handed leptons NL Rodning, University of Alberta - February 2001 6

The preceding - - in terms of the Michel parameters in terms of the Michel parameters The preceding ⎡ ⎤ ⎛ ⎞ 2 2 − + ρ − + ξ θ − + δ − 2 ⎜ ⎟ ~ 3 3 ( 4 3 ) cos( ) 1 ( 4 3 ) rate x x x P x x ⎢ ⎥ µ ⎝ ⎠ ⎣ ⎦ 3 3 [ ] 3 For example- ρ ≡ + + + 2 2 2 2 V V T T | | | | | | | | g g g g LL RR LR RL 4 [ ] 3 + + + + 2 2 2 2 S S S S | | | | | | | | g g g g LL RR LR RL 16 Similar expressions [ ] ( ) ( ) exist defining ξ and 3 − + * * S T S T Re Re g g g g δ . LR LR RL RL 4 = = V 2 3 / 4 when | | 1 g Decay Rate LL A fourth parameter, and other couplings are zero η , contributes to order (m e /m µ ) Above expression is modified by radiative Positron corrections, required Positron Angle Energy to second order NL Rodning, University of Alberta - February 2001 7

The Expression becomes considerably simpler in the The Expression becomes considerably simpler in the Standard Model Standard Model 3/4 ⎡ ⎤ ⎛ ⎞ 2 2 − + ρ − + ξ θ − + δ − 2 ⎜ ⎟ ~ 3 3 ( 4 3 ) cos( ) 1 ( 4 3 ) rate x x x P x x ⎢ ⎥ µ ⎝ ⎠ ⎣ ⎦ 3 3 For example- Standard Model [ ] 1 Values 0 0 0 3 V 2 V 2 T 2 T 2 ρ ≡ + + + | g | | g | | g | | g | LL RR LR RL 4 [ ] 0 0 0 0 3 S 2 S 2 S 2 S 2 + + + + | g | | g | | g | | g | LL RR LR RL 16 [ ] ( ) ( ) 0 0 0 0 3 S T * S T * − + Re g g Re g g LR LR RL RL 4 when V 2 = = 3 / 4 | g | 1 LL and other couplings are zero Similar expressions exist defining ξ, δ, and η . NL Rodning, University of Alberta - February 2001 8

This simple model may be too simple exchange particle: spin 0 spin 2 spin 1 < < ≡ S V T | | 0 . 066 | | 0 . 033 | | 0 g g g RR RR RR < < < S V T | | 0 . 125 | | 0 . 060 | | 0 . 036 g g g LR LR LR < < < S V T | | 0 . 424 | | 0 . 110 | | 0 . 122 g g g RL RL RL > < ≡ V S | | 0 . 96 T g | | 0 . 55 | | 0 g g LL LL LL All but one of these terms has been set to zero in the Standard model for simplicity The Weak Interaction may not be purely (V-A) NL Rodning, University of Alberta - February 2001 9

TWIS T - - Goals TWIS T TWIS T TWIS T Goals Experiment 614 at TRIUMF We propose to study 10 9 µ + decays Goal: • to determine the Michel parameters to a few parts in 10 4 • to test for weak couplings inconsistent with the Standard Model NL Rodning, University of Alberta - February 2001 10

11 - Spectrometer NL Rodning, University of Alberta - February 2001 TWIS T - TWIS T TWIS T TWIS T

TWIS T - - Beamline TWIS T TWIS T TWIS T Beamline NL Rodning, University of Alberta - February 2001 12

TWIS T TWIS T – TWIS T TWIS T – 1AT1 depolarization 1AT1 depolarization 1AT1 Scatter => ~ 0.0001 depolarization 2 = µ slope depolariza tion per 25 depth 4 10 NL Rodning, University of Alberta - February 2001 13

TWIS T - - Chambers & half detector TWIS T TWIS T TWIS T Planar drift chambers sample positron track NL Rodning, University of Alberta - February 2001 14

TWIS T - - Yoke TWIS T TWIS T TWIS T Yoke The TWIST yoke pieces were delivered and assembled before Christmas Alignment was completed in the first week of January NL Rodning, University of Alberta - February 2001 15

TWIS T – – Solenoid and WC track TWIS T TWIS T TWIS T Solenoid and WC track Track is in place and aligned to accept detector cradle and stack Magnet is cooling Commissioning begins this week Mapping complete by end of March NL Rodning, University of Alberta - February 2001 16

TWIS T - - Chambers TWIS T TWIS T TWIS T Chambers NL Rodning, University of Alberta - February 2001 17

TWIST Glass Planes TWIST Glass Planes Planes are assembled on glass plates with optical precision relative to longitudinal coordinate NL Rodning, University of Alberta - February 2001 18

TWIS T – – Chamber Support Cradle TWIS T TWIS T TWIS T Chamber Support Cradle NL Rodning, University of Alberta - February 2001 19

E614 Precision E614 Precision Accepted Experimental Values ρ = ± 0 . 7518 0 . 0026 ξ = ± 1 . 0027 0 . 0085 P µ δ = ± 0 . 7486 0 . 0038 η = − ± 0 . 007 0 . 013 E614 Proposal σ = ± ± 0 . 00005 0 . 00009 ρ σ = ± ± 0 . 00010 0 . 00010 ξ P µ σ = ± ± 0 . 00008 0 . 00010 δ σ ≈ ± 0 . 003 η 25-60 fold improvement in precision on the Michel parameters 3-10 fold improvement in couplings NL Rodning, University of Alberta - February 2001 20

The (forward - backward) distribution goes flat at a value of x dependant (only) upon δ ⎡ ⎤ ⎛ ⎞ 2 [ ] − ξ θ − + δ − 2 ⎜ ⎟ ~ 2 cos( ) 1 ( 4 3 ) Forward Backward x P x x ⎢ ⎥ µ ⎝ ⎠ ⎣ ⎦ 3 Find x such that ⎡ ⎤ ⎛ ⎞ 2 ξ − + δ − 2 ⎜ ⎟ 2 1 ( 4 3 ) x P x x ⎢ ⎥ term vanishes µ ⎝ ⎠ ⎣ ⎦ 3 Standard Model Sensitive primarily to δ Uncertainty in δ E614 Sensitivity NL Rodning, University of Alberta - February 2001 21

Same as the previous slide - on expanded scale ⎡ ⎤ ⎛ ⎞ 2 ξ − + δ − 2 ⎜ ⎟ 2 1 ( 4 3 ) x P x x ⎢ ⎥ µ Zero crossing ⎝ ⎠ ⎣ ⎦ 3 determines δ Slope is essentially P µ ξ Standard Model Uncertainty in δ E614 Sensitivity NL Rodning, University of Alberta - February 2001 22