Fundamental physics in rare pion and muon decays

Fundamental physics in rare pion and muon decays Dinko Počanić University of Virginia IX LASNPA, Quito, Ecuador 18- July 011 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 1 / 40

Overview Outline Overview and status of allowed π and µ decays Pion beta decay: π + π 0 e + ν Radiative pion decay: π + e + νγ Allowed muon decays: ordinary and radiative The π e decay: π + e + ν Summary D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 / 40

Overview Summary of known decays Known and measured pion and muon decays Decay BR π + µ + ν 0.9998770 (4) (π µ ) µ + νγ.00 (5) 10 4 (π µγ ) e + ν 1.30 (4) 10 4 (π e ) e + νγ 1.61 (3) 10 7 (π eγ ) π 0 e + ν 1.05 (34) 10 8 (π e3, π β ) e + νe + e 3. (5) 10 9 (π eee ) π 0 γγ 0.98798 (3) e + e γ 1.198 (3) 10 (Dalitz) e + e e + e 3.14 (30) 10 5 e + e 6. (5) 10 8 µ + e + ν ν 1.0 e + ν νγ 0.014 (4) e + ν νe + e 3.4 (4) 10 5 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 3 / 40

Overview Summary of known decays Pions, muons, fundamental interactions & symmetries Why isn t π e the dominant decay mode? Deep link to V A nature of the weak interaction PV; Pion triplet (π +, π 0, π ), are the Goldstone bosons in the spontaneous breaking of Chiral Symmetry; Explicit breaking of χs: m π m q (Gell-Mann Oakes Renner rel.); Conserved Vector Current: SU() V ; Why is the beta energy spectrum in µ e decay continuous (3-body decay, NO µ eγ)? Lepton Flavor Conservation. Today there are many excellent precise measurements exploring these topics: FAST, MEG, MULAN, Muon(g-), TWIST,... D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 4 / 40

Overview Recent measurements Recent π, µ allowed decay measurements π + π 0 e + ν e................................. PIBETA ( 99 01) SM checks related to CKM unitarity π + e + ν e γ(or e + e )......... PIBETA ( 99 04), PEN ( 06 10) F A /F V, π polarizability (χpt calibration) tensor coupling besides V A (?) µ + e + ν e ν µ................................ TWIST (003 04) departures from V A in L weak µ + e + ν e ν µ γ(or e + e )........... PIBETA ( 04), PEN ( 06 10) departures from V A in L weak { π + e + PEN ( 06 10) ν e..................................... PiENu ( 06 ) e-µ universality pseudoscalar coupling besides V A ν sector anomalies, Majoron searches, m h+, PS l-q s, V l-q s,... search for signs of SUSY (MSSM) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 5 / 40

Pion beta decay Pion beta decay: π + π 0 e + ν (PIBETA: 1999 001 runs) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 6 / 40

Pion beta decay Motivation Quark-Lepton (Cabibbo) Universality The basic weak-interaction V-A form (e.g., µ decay): M e l α ν e ū e γ α (1 γ 5 )u ν is replicated in hadronic weak decays M p h α n ū p γ α (G V G A γ 5 )u n with G V,A 1. Departure from G V = 1 (CVC) comes from weak quark (Cabibbo) mixing: G V = G µ cos θ C (= G µ V ud ) cos θ C 0.97 3 q generations lead to the V ud V us V ub Cabibbo-Kobayashi-Maskawa V cd V cs V cb (CKM) matrix (1973): V td V ts V tb CKM unitarity cond.: V = 1 ( V ud + V us + V ub )? = 0, stringently tests the SM. Prior to 004 there was a persistent.5σ shortfall in V, motivating many experiments to determine CKM m.e. s, esp. V ud and V us. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 7 / 40

Pion beta decay The apparatus and method The PIBETA/PEN apparatus stopped π + beam active target counter 40-det. CsI calorimeter central tracking digitized waveforms stable temp./humidity BC PEN Detector 009 π + beam vac. pure CsI mtpc AD AT PMT PH MWPC1 MWPC 10 cm D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 8 / 40

Pion beta decay The apparatus and method Number of events 7000 6000 5000 4000 3000 000 π + π 0 e + ν γ1 γ Simulation Data Number of Events 40000 30000 0000 10000 Simulation Data π e ν 1000 0 160 16.5 165 167.5 170 17.5 175 177.5 180 Opening angle Θ γ1γ (degr) 0 45 50 55 60 65 70 75 Positron Energy (MeV) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 9 / 40

Pion beta decay Results PIBETA result for π β decay [PRL 93, 181803 (004)] B exp-t πβ = [1.040 ± 0.004 (stat) ± 0.004 (syst)] 10 8, B exp-e πβ = [1.036 ± 0.004 (stat) ± 0.004 (syst) ± 0.003 (π e )] 10 8, McFarlane et al. [PRD 1985]: B = (1.06 ± 0.039) 10 8 SM Prediction (PDG): B = 1.038 1.041 10 8 (90% C.L.) (1.005 1.007 10 8 excl. rad. corr.) PDG 010: V ud = 0.9745() PIBETA: V ud = 0.9748(5) or V ud = 0.978(30). D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 10 / 40

Pion beta decay Results Present Status of V ud.9800 V ud V = 0.9744 + 0.000 ud.9750.9700.003 nuclear 0 + 0+ neutron nuclear mirrors pion Uncertainty.00.001 Experiment Radiative correction Nuclear correction (Courtesy of John Hardy, May 009) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 11 / 40

Radiative pion decay π + e + νγ Radiative pion decay: π + e + νγ PIBETA: 1999-001 & 004 runs ( PEN: 008 010 runs ) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 1 / 40

Radiative pion decay Motivation π + e + νγ: Standard IB and V A terms SM A tensor interaction, too? Exchange of S=0 leptoquarks P Herczeg, PRD 49 (1994) 47 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 13 / 40

Radiative pion decay Motivation The π eνγ amplitude and FF s The IB amplitude (QED): M IB = i eg F V ud f π m e ɛ µ ē ( kµ kq p µ pq + σ µνq ν ) (1 γ 5 ) ν. kq The structure-dependent amplitude: M SD = eg F V ud m π ɛ ν ēγ µ (1 γ 5 )ν [F V ɛ µνστ p σ q τ + if A (g µν pq p ν q µ )]. The SM branching ratio (γ F A /F V ; x = E γ /m π ; y = E e /m π ), dγ πeγ dx dy = α { ( π Γ FV m ) π πe IB (x, y) + f π m e [ (1 + γ) SD + (x, y) + (1 γ) SD (x, y) ] ( FV m π + f π ) [(1 + γ) S + int (x, y) + (1 γ) S int (x, y)] }. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 14 / 40

Radiative pion decay Previous data Available data on pion form factors F V CVC = 1 Γ(π 0 γγ) α πm π 0 = 0.059(9). F A 10 4 reference note 106 ± 60 Bolotov et al. (1990) (F T = 56 ± 17) 135 ± 16 Bay et al. (1986) 60 ± 30 Piilonen et al. (1986) 110 ± 30 Stetz et al. (1979) 116 ± 16 world average (PDG 004) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 15 / 40

Radiative pion decay Previous data Available data on pion form factors F V CVC = 1 Γ(π 0 γγ) α πm π 0 = 0.059(9). F A 10 4 reference note 106 ± 60 Bolotov et al. (1990) (F T = 56 ± 17) 135 ± 16 Bay et al. (1986) 60 ± 30 Piilonen et al. (1986) 110 ± 30 Stetz et al. (1979) 116 ± 16 world average (PDG 004) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 15 / 40

Radiative pion decay Previous data Available data on pion form factors F V CVC = 1 Γ(π 0 γγ) α πm π 0 = 0.059(9). F A 10 4 reference note 106 ± 60 Bolotov et al. (1990) (F T = 56 ± 17) 135 ± 16 Bay et al. (1986) 60 ± 30 Piilonen et al. (1986) 110 ± 30 Stetz et al. (1979) 116 ± 16 world average (PDG 004) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 15 / 40

Radiative pion decay Results F A Form Factor x 10 4 150 140 130 10 110 100 4σ σ 1σ F V CVC = 59(9) x 10-4 χ Contours Best values of pion form factor parameters: Combined analysis of 1999-001 and 004 data sets M. Bychkov, et al., PRL 103 (009) 05180. 90 80 0 30 40 50 60 70 F V Form Factor x 10 4 80 90 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 16 / 40

Radiative pion decay Results Experimental history of pion F A and F V THIS WORK POCANIC (004) BOLOTOV (1990) DOMINGUEZ (1988) EGLI 1 (1986) PIILONEN (1986) BAY (1986) STETZ (1978) DEPOMMIER (1963) F V =0.059 F V =0.053 1 F V =0.055 CVC PREDICTION (006) THIS WORK BOLOTOV (1990) EGLI (1986) -0.6-0.4-0. 0 0. 0.4 0.6 0.8 1 1. γ=f A /F V -0.0-0.01 0 0.01 0.0 0.03 0.04 F V D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 17 / 40

Radiative pion decay Results Summary of pion form factor and B.R. results F V = 0.058 ± 0.0017 (14 ) F A = 0.0119 ± 0.0001 exp (F CVC V ) (16 ) a = 0.10 ± 0.06 ( ) 5. 10 4 < F T < 4.0 10 4 90 % C.L. Derived pion polarizability and π 0 lifetime (at L.O.): α E = β M = (.783 ± 0.03 exp ) 10 4 fm 3 τ π 0 = (8.5 ± 1.1) 10 17 s { current PDG avg: 8.4 (4) PrimEx PRL 10: 7.8 () B πeγ (E γ > 10 MeV, θ eγ > 40 ) = 73.86(54) 10 8 (17 ) Above results will be improved with new PEN data and analysis. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 18 / 40

Muon decays µ + e + ν e ν µ(γ) Allowed muon decays: µ + e + ν e ν µ (TWIST 003 05) µ + e + ν e ν µ γ (PIBETA 004, PEN 008 10) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 19 / 40

Muon decays Basic theory Michel parameters of muon decay: µ eν µ ν e d Γ dx d(cos θ) = m µ 4π 3 W eµg 4 F x x0 [ F IS (x) + P µ + cos θ F AS (x) ] [ 1 + P ] e +(x, θ) ˆζ Isotropic part: Anisotropic part: F IS (x) = x(1 x) + 9 ρ(4x 3x x 0 ) + η x 0 (1 x) F AS (x) = 1 3 ξ x x 0 (1 x + 3 [ )]) δ 4x 3 + ( 1 x 0 1 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 0 / 40

Muon decays Michel theory of RMD Michel parameters of radiative muon decay: µ eν µ ν e γ d 3 B(x, y, θ) dx dy π d(cos θ) = f 1(x, y, θ) + ηf (x, y, θ) + (1 4 3 ρ)f 3(x, y, θ) ρ = 3 4 3 4 [ g V LR + g V RL + g T LR + g T RL ] + R(gRL S g RL T + g LR S g LR T ) SM 3 4, η = ( grl V + glr V ) + 1 ( g LR S 8 + g LR T + grl S + g RL T ) ( + glr T + grl T ) SM 0. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 1 / 40

Muon decays Michel theory of RMD OMD study: TWIST experiment (TRIUMF) Main results: ρ = 0.7501 (5) and δ = 0.7507 (7), MacDonald, et al., Phys. Rev. D 78 (008) 03010. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 / 40

Muon decays Michel theory of RMD RMD differential branching ratio [B. VanDevender, PhD thesis] PRELIMINARY (new analysis+data) due to small-angle bremsstrahlung uncertainties in GEANT B exp = [4.40 ± 0.0 (stat.) ± 0.09 (syst.)] 10 3 14! B theo = 4.30 10 3 (E γ > 10 MeV, θ eγ > 30 ) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 3 / 40

Muon decays Michel theory of RMD Experimental History of η PIBETA preliminary (B. VanDevender, PhD thesis; 004 data set): η = 0.084 ± 0.050(stat.) ± 0.034(syst.) η 0.033; new world average: η 0.08 (68 % c.l.) reduced by a factor of.5. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 4 / 40

The π e decay π + e + ν The π e decay: π + e + ν PEN and PiENu experiments (006 ) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 5 / 40

The π e decay π + e + ν π eν decay: SM calculations; measurements Modern theoretical calculations: B calc = Γ(π e ν(γ)) Γ(π µ ν(γ)) calc = 1.35 (5) 10 4 Marciano and Sirlin, [PRL 71 (1993) 369] 1.354 () 10 4 Finkemeier, [PL B 387 (1996) 391] 1.35 (1) 10 4 Cirigliano and Rosell, [PRL 99, 31801 (007)] Experiment, world average [current PDG]: Γ(π e ν(γ)) Γ(π µ ν(γ)) exp = (1.30 ± 0.004) 10 4 N.B.: PEN, PiENu aim at: δb B 5 10 4 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 6 / 40

The π e decay π + e + ν π eν decay: SM calculations; measurements Modern theoretical calculations: B calc = Γ(π e ν(γ)) Γ(π µ ν(γ)) calc = 1.35 (5) 10 4 Marciano and Sirlin, [PRL 71 (1993) 369] 1.354 () 10 4 Finkemeier, [PL B 387 (1996) 391] 1.35 (1) 10 4 Cirigliano and Rosell, [PRL 99, 31801 (007)] Experiment, world average [current PDG]: Γ(π e ν(γ)) Γ(π µ ν(γ)) exp = (1.30 ± 0.004) 10 4 N.B.: PEN, PiENu aim at: δb B 5 10 4 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 6 / 40

The π e decay π + e + ν π eν decay: SM calculations; measurements Modern theoretical calculations: B calc = Γ(π e ν(γ)) Γ(π µ ν(γ)) calc = 1.35 (5) 10 4 Marciano and Sirlin, [PRL 71 (1993) 369] 1.354 () 10 4 Finkemeier, [PL B 387 (1996) 391] 1.35 (1) 10 4 Cirigliano and Rosell, [PRL 99, 31801 (007)] Experiment, world average [current PDG]: Γ(π e ν(γ)) Γ(π µ ν(γ)) exp = (1.30 ± 0.004) 10 4 N.B.: PEN, PiENu aim at: δb B 5 10 4 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 6 / 40

The π e decay SM calculations; mass limits π e Decay and the SM B(π e ) in SM dominated by (V A) helicity suppression. Deviations primarily due to PS int. terms. Most general 4-fermion π e amplitude: G F [ ( dγ µ γ 5 u ) ( ν e γ µ γ 5 (1 γ 5 )e ) f e AL In the SM: f l AL + f e PL ( dγ 5 u ) ( ν e γ 5 (1 γ 5 )e ) ] + r.h. ν term = 1, while f l xr = f Px l = 0, with l = e, µ. Strong helicity suppression amplifies sensitivity to f e PL : B obs πe BSM πe B SM πe = B B SM =... m π m e (m u + m d ) f e PL 7700f e PL! Tgt accuracy of the PEN experiment, B/B 5 10 4, translates into attractive mass limits: D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 7 / 40

The π e decay SM calculations; mass limits Example mass bounds from PEN goal accuracy (a) Charged Higgs, m H+ [Shanker, NP B04 (8) 375] Given a mixing angle suppression S 10, we get f e PL S m tm τ m H+ yielding m H+ > 6.9 TeV. (b) Pseudoscalar leptoquarks, m P Given an estimated effective Yukawa coupling of y 1/50, we can find m P, mass of the color-triplet PS l-q: f e PL G F y m P yielding m P > 3.8 TeV. (c) Vector leptoquarks, M G Following Shanker who assumes gauge coupling g g SU(), we get: f e PL 4M W M G yielding M G > 630 TeV. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 8 / 40

The π e decay SUSY tests MSSM calculations (RPC) [Ramsey-Musolf et al., PR D76 (007) 095017] 0.005 0.005 minimal selectron, smuon masses: Re Μ SUSY R e Μ 0.00 0.001 0.0005 0.000 lowest mass chargino: Re µ SUSY R e µ 0.00 0.001 0.0005 0.000 0.005 100 150 00 300 500 700 1000 Min mel,mµ L GeV 100 150 00 300 500 700 1000 m GeV mχ1 slepton mass degeneracy: Re µ SUSY R e µ 0.00 ReHiggsino 0.001 mass 0.0005 param. µ and mũl : 0.000 0.1 1 10 mel mµ L RPV scenario constraints also discussed. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 9 / 40

The π e decay Lepton universality Lepton universality (and neutrinos) From R e/µ = R τ/π = Γ(π e ν(γ)) Γ(π µ ν(γ)) = g e me (1 me/m µ) ( ) 1 + δre/µ gµ mµ (1 mµ/m π) Γ(τ e ν(γ)) Γ(π µ ν(γ)) = g τ mτ 3 (1 mπ/m τ ) ( ) 1 + δrτ/π gµ mµm π (1 mµ/m π) one can evaluate ( ) ge = 1.001 ± 0.0016 and g µ π For comparison ( ) ge = 0.999 ± 0.011 and g µ W ( gτ g µ ( gτ g e ) πτ ) W = 1.0030 ± 0.0034. = 1.09 ± 0.014. [Presently allowed level of LUV could account for NuTeV anomaly. ] D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 30 / 40

The π e decay Lepton universality Loinaz et al., PRD 70 (004) 113004 ll = ( gl g l ) 1 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 31 / 40

The π e decay PEN experiment: status, plans 0.5*tgt_wf.mu3.mean-0.5*tgt_wf.pi3.mean {tgt_wf.fitattempt==1 && tgt_wf.subtintegral_left<10e3 && tgt_wf.subtintegral_middle<170e3 && tgt_wf.subtintegral_right<40e3 && 0.5*tgt_wf.e3.mean-0.5*tgt_wf.mu3.mean>10 && 0.5*tgt_wf.e3.mean-0.5*tgt_wf.mu3.mean<70 && trak.ecsi[0]<48} χ / ndf 976. / Constant 5.591 ± 0. PEN experiment: status and plans Approved in 006; development runs: 007, 08; data runs 09, 10. Improved beam tracking (minitpc) implemented in 09, 10 runs. > 0 M π e s recorded (δb/b) stat 10 4. Illustration: decays in the target detector (008 run): trigger-weighted events / ns 4 10 3 10 10 10 1 top: bottom: muons positrons Events 300 50 00 150 100 Measurement π decay curve -1 10 50-10 0 50 100 150 00 pion decay time [ns] 0 0 5 10 15 0 t µ - t π (ns) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 3 / 40

Mean RMS Underflow Overflow Integral 65000 Mean The π e decay PEN experiment: status, plans Waveform fitting in PEN [Anthony Palladino] 65000 60000 55000 50000 45000 40000 35000 30000 5000 500 550 600 650 700 t (0.5 ns) 65000 60000 55000 50000 45000 40000 35000 30000 60000 55000 50000 45000 40000 35000 30000 5000 500 550 600 650 700 t (0.5 ns) 65000 60000 55000 50000 45000 40000 35000 30000 5000 550 600 650 700 750 550 600 650 700 750 t (0.5 ns) t (0.5 ns) D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 33 / 40 5000

χ 3 The π e decay PEN experiment: status, plans χ 3 PEN: distinguishing π e and π µ e decays (measurement) 10 9 χ 3 vs χ for E e +<60MeV 0.005 0.0045 10 9 χ 3 vs χ for E e +>60MeV 0.00 0.0018 8 0.004 8 0.0016 7 0.0035 7 0.0014 6 0.003 6 0.001 [A. Palladino & L.P. Alonzi] 5 4 3 1 0 0 1 3 4 5 6 7 8 9 10 χ 10 8 6 4 χ vs E e + 0.005 0.00 0.0015 0.001 0.0005 0 0.0016 0.0014 0.001 0.001 5 4 3 1 0 0 1 3 4 5 6 7 8 9 10 χ 10 8 6 4 χ vs t e + 0.001 0.0008 0.0006 0.0004 0.000 0 0.0016 0.0014 0.001 0.001 χ 0 0.0008 χ 0 0.0008 0.0006 0.0006 4 6 8 0.0004 0.000 4 6 8 0.0004 0.000 10 0 0 10 0 30 40 50 60 70 80 E e + 10 0 0 50 100 150 00 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 34 / 40 t e +

χ 3 The π e decay PEN experiment: status, plans χ 3 PEN: distinguishing π e and π µ e decays (simulation) 10 9 χ 3 vs χ for E e +<60MeV 0.005 0.0045 10 9 χ 3 vs χ for E e +>60MeV 0.00 0.0018 8 0.004 8 0.0016 7 0.0035 7 0.0014 6 0.003 6 0.001 [A. Palladino & L.P. Alonzi] 5 4 3 1 0 0 1 3 4 5 6 7 8 9 10 χ 10 8 6 4 χ vs E e + 0.005 0.00 0.0015 0.001 0.0005 0 0.0016 0.0014 0.001 0.001 5 4 3 1 0 0 1 3 4 5 6 7 8 9 10 χ 10 8 6 4 χ vs t e + 0.001 0.0008 0.0006 0.0004 0.000 0 0.0016 0.0014 0.001 0.001 χ 0 0.0008 χ 0 0.0008 0.0006 0.0006 4 6 8 0.0004 0.000 4 6 8 0.0004 0.000 10 0 0 10 0 30 40 50 60 70 80 E e + 10 0 0 50 100 150 00 D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 35 / 40 t e +

The π e decay PiENu experiment PiENu experiment (TRIUMF) 3000 500 160 140 10 π e ν 000 100 1500 80 1000 500 π µ e π e ν 60 40 0 0 0 10 0 30 40 50 60 70 80 Energy (MeV) 0 60 65 70 75 80 Energy (MeV) π µ e 60000 300 50000 40000 50 00 150 30000 0000 100 50 π e ν 50 100 150 00 50 300 350 400 450 500 Time (ns) 0 0 100 00 300 400 500 Time (ns) Acceptance: Ω 0. 4π sr Excellent energy resolution. Project started in 006. Data taking currently under way. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 36 / 40

Summary Status of allowed π and µ decays A significant experimental effort is under way to make use of the unparalleled theoretical precision in the weak interactions of the lightest particles. Information obtained is complementary to expected collider results, and necessary for their proper interpretation. Orders of magnitude improvement in precision has been achieved; more lie in store. Modest scale of investment of resources required. Unique opportunity for scientific advancement. Great projects for graduate students and postdocs full range of professional training. D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 37 / 40

Summary PEN Collaboration Current and former PIBETA and PEN collaborators L. P. Alonzi a, K. Assamagan a, V. A. Baranov b, W. Bertl c, C. Broennimann c, S. Bruch a, M. Bychkov a, Yu.M. Bystritsky b, M. Daum c, T. Flügel c, E. Frlež a, R. Frosch c, K. Keeter a, V.A. Kalinnikov b, N.V. Khomutov b, J. Koglin a, A.S. Korenchenko b, S.M. Korenchenko b, M. Korolija d, T. Kozlowski e, N.P. Kravchuk b, N.A. Kuchinsky b, D. Lawrence h, W. Li a, J. S. McCarthy a, R. C. Minehart a, D. Mzhavia b,f, E. Munyangabe a, A. Palladino a,c, D. Počanić a, B. Ritchie h, S. Ritt a,c, P. Robmann g, O.A. Rondon-Aramayo a, A.M. Rozhdestvensky b, T. Sakhelashvili f, S.N. Shkarovskiy b, P. L. Slocum a, L. C. Smith a, N. Soić d, U. Straumann g, I. Supek d, P. Truöl g, Z. Tsamalaidze f, A. van der Schaaf g, E.P. Velicheva b, V.P. Volnykh b, Y. Wang a, C. Wigger c, H.-P. Wirtz c, K. Ziock a. a Univ. of Virginia, USA c PSI, Switzerland e Swierk, Poland g Univ. Zürich, Switzerland b JINR, Dubna, Russia d IRB, Zagreb, Croatia f IHEP, Tbilisi, Georgia h Arizona State Univ., USA Home pages: http://pibeta.phys.virginia.edu http://pen.phys.virginia.edu D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 38 / 40

Additional slides Current limits from RMD Additional slides D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 39 / 40

Additional slides Current limits from RMD Experimental Limits (90 % C.L.) on g γ αβ g γ αβ S V T LL 0.550 >0.960 0 LR 0.088 0.036 0.05 RL 0.417 0.104 0.104 RR 0.067 0.034 0 max. values: g S αβ g V αβ g T αβ 1 1 3 0.58 [Most recent global fit by C.A Gagliardi et al., PR D 7 (005) 07300; Add l TWIST constraints on L-R symmetric models: PRL 106 (011) 041804.] D. Počanić (UVa) rare π, µ decays IX LASNPA, 1 Jul 011 40 / 40