Why the is Boring and Why that is Exciting

Transcription

1 Why the is Boring and Why that is Exciting Tau Review WIN0 Jean Etienne Duboscq Cornell University Thanks to: T. Browder, M. Davier, S. Eidelman, H. Evans, KK Gan, R. Kass, A. Pich, M. Roney, R. Sobie, A. Stahl, R. Stroynowski, J. Swain, J. Urheim, A. Weinstein

2 The Tau in Other Fields The TAU is the last letter of the Greek alphabet and in spiritual terms represents the end or the fulfillment of the revealed word. It is a sign of life and salvation. In the Old Testament the prophet marks those with a Tau who have chosen to reject a sinful lifestyle (Ezekiel 9:4). From: Hospital Sisters of St Francis web site

3 Outline Overview of the Leptonic Decays Lepton Universality Lorentz Structure & Michel Parameters Inclusive Hadronic Decays Spectral Functions CVC Alpha_s Vacuum Polarization Tau as Hadron Factories Rare Decays Forbidden Decays CP Violation Neutrino Properties

4 Overview of the m = (0.3) MeV BES Lifetime = 90.6 (1.1) fs (LEP, CLEO) B e =B(e) = (0.05) % (tauk WA) B() = (0.05) % (tauk WA) B(e) = 1.75(0.18) % B() = 0.361(0.038) % E >10MeV CLEO B(1/3/5prong) = 85.7(0.13) % /14.56(0.13) / 0.17(0.04) % Expected final states: e n Kn KKn, n= 0, 1, K

5 Leptonic Tau Decays τ - g ν τ SM predicts W g e -, µ -, d θ 5 m f B B m d θ cos θ c d + sin θ c s ν e, ν µ, u Mass: M =1777.0(0.3) MeV (BES) Lifetime: =90.6 (1.1) fs (LEP+CLEO) B e =17.80(0.05)% (LEP+CLEO) B =17.34(0.05)% (LEP+CLEO) τ lifetime (fs) g τ / g e,µ = ± B(τ lνν ) (%)

6 Lepton Universality: Tau Decay Full SM prediction for Lepton Decay B m g g 3m W 4 fm 1 S EW Compare g from tau decays to each other and other weak decays B e vs B g /g e = / to e g / g e = / B e vs < B > g / g = / B vs <B e > g / g e = / g e = g g /g l = / to g / g = / CLEO ± OPAL (prel) ± DELPHI ± ALEPH (prel) ± L3 (prel) ± χ /ν = 0.90 / 4 (CL = 9%) TAU000 average ± W to l Universality good at.5% level from LEP and CDF/D0 g µ / g e

7 Theorists Prefer General, local, derivative free, lepton number conserving, Lorentz invariant structure for fully leptonic decay SM: g V LL=1 ; 11 others = 0 Lorentz Structure M 4G F S,V,T i, j L,R S,V,T 1,, g ij i i, Experimentalists Prefer Something they can measure Michel Parameters use Observed Quantities 1 d dxd cos x 1 1 x 4 3 8x 6 4 m 1 x P cos 41 x 4 m x 3 8x 6 SM: j x E Emax

8 CLEO s Analysis At CLEO - no polarized beams But + and - spins are 95 % correlated Use to decay as spin analyzer vs to l Promising future at BELLE, Babar : stat error dominates 1 d h 0 h h P h h dx e+ Polarization - + e-

9 WA of Michel Parameters SM is still OK /dof is too good CLEO dominates all but value (DELPHI,OPAL) Other Michel param exist in radiative decays - CLEOc, BES? ρ Electrons Muons ξ ξδ η χ /ndf = 3.6 / 7

10 World Summary of g ij Couplings Coupling to right handed currents excluded Coupling limits from mu are still more stringent than limits from taus No LL limits - need scattering to separate S from V S RR S LR S RL V RR V LR V RL T LR T RL

11 Hadronic Tau Decays Weak current ( final state) -first class currents: V: G=+1, J P =1 - - (n) A: G=-1, J P =0 -,1 + -, a1- (n+1) Opposite G parity = second class suppressed (Isospin violation) - soon to be observed? Use to study inclusive QCD properties, CVC Use as a lab to generate lighter mesons

12 Inclusive Hadronic Decays Spectral Function: Decay product Mass Spectrum, after decay kinematic correction + branching ratio normalization This can be broken up into V,A, +Strange contributions, and studied as a function of q^ vs B x 1 dn x B e N x ds Branching Ratio Norm m 1 sm 1 s m q Spectrum V-A kinematics

13 CVC CVC (Isospin): weak coupling in decay is related to e + e - scattering, eg: B 0 f,m dq g(q I 1 ) ee q 50 B WA = 5.17(.14) % F π 30 CVC = 4.94(.3) % Tau000 F π CLEO Tau s [GeV] 10-1 e + e s [GeV]

14 CVC (cont) discrepancy in 3 0 and υ 1.5 τ (V, I=1) ν τ e + e (V, I=1) (ALEPH) 1.5 σ (nb) Mass (GeV/c ) Global test of CVC CVC is (mostly) OK E (GeV) e + e -

15 Alpha_s υ 1 + a 1.5 τ (V,A, I=1) ν τ parton model prediction ALEPH perturbative QCD (massless) 1.5 The tau mass is just large enough to allow a believable calculation of: R hadrons e α s (Energy) M τ Mass (GeV/c ) τ (ALEPH) Z (LEP + SLD) S (m )=0.345(0.00) S (m )=0.108(0.05) M Z Tau Energy (GeV)

16 Strange Quark Mass Use a moments analysis kl R, S 0 m ds 1 s m k s m l dr, S ds Compare moments Strange=1 and S=0 moments Allows optimal balancing of theory uncertainties, experimental errors at different s m s (m )= 11(3) MeV v+a ALEPH K π K ππ K 3π+K - η (MC) K 4π (MC) K 5π (MC) Mass (GeV/c )

17 Hadronic Vacuum Polarization What is the probability of popping qq out of the Vacuum? * qq * Use e+e- (* qq)hadrons CVC relates this to spectral functions hadrons α had (M ) ( 10 4 ) Z Lynn, Penso, Verzegnassi, 87 Eidelman, Jegerlehner 95 Burkhardt, Pietrzyk 95 Martin, Zeppenfeld 95 Swartz 96 Alemany, Davier, Höcker 97 Davier, Höcker 97 Kühn, Steinhauser 98 Groote et al. 98 Erler 98 Davier, Höcker 98 Direct impact on QED, (g-) Barkov et al. 85 had M Z... ds e e had a (..) ds e e sk s s K s a had ( ) µ Kinoshita, Nizic, Okamoto 85 Casas, Lopez, Ynduráin 85 Eidelman, Jegerlehner 95 Brown, Worstell 96 Alemany, Davier, Höcker 97 Davier, Höcker 97 Davier, Höcker 98

18 Rare Decays B( ) < 1.3x10-3 ( nd Class) CLEO99 B( K ) = 5.0 (1.) x 10-4 CLEO98 B( ) = 4.8 (1.1) x 10-4 CLEO98 B( K 0 K 0 ) = 3.1(.3)x10-4 ALEPH98 B( K - K + K ) < 1.9x10-4 ALEPH98 B( ) < 1.4x10-4 ( nd Class) CLEO96 B( e + e - e + ) =.8(1.5) x10-5 CLEO98 B( 7 +/- ) <.4x10-6 CLEO97 Lots of room for Improvement from B factories

19 Forbidden Decays Massive neutrinos could induce neutrinoless decays In some L-R sym SUSY models Weak Limits Can Beat Tight Limits B B e B( ) < 1.0x10-6 (Belle 001) 19M B(e - ) < 1.x10-11 (MEGA /LAMPF 99) B( ) < 1.1x10-6 (CLEO00 )1M

20 Forbidden Decays (cont) PDG : big list of limits for neutrinoless modes B ( XY) < 10-3 to 10-6 X=(e,,p) Y=( l, m n K ) Newcomer: Belle M (a) τ e K 0 (MC) (b) τ µ K 0 (MC) B(e - K 0 ) < 1.8x10-6 Events / (0MeV/c ) (c) Data and MC (d) Data and MC B( - K 0 ) < 1.8x cut cut M(e K S )(GeV/c ) M(µ K S )(GeV/c ) Lots of Potential for Belle and Babar

21 CP Violation in Decay A W = W vector e i V A H = H scalar Search for CP violation in processes with interfering amplitudes e i se i isospin violation in Su(3) violation in

22 Use one side of events -measured kinematic constraint Belle CPV in A CP cos cos N cos cos N cos cos N cos cos N cos cos BELLE-CONF M pairs Similar CLEO analysis for K final state - PRL81,383(1998)

23 I I CLEO CPV in pairs are produced coherently : Can use info from other Use vs optimal observable PRD45(199)405 D.Atwood, A.Soni CevenPodd CevenPeven Model dependent limit on relative Higgs like coupling 1M pairs dn/d Data Standard Model MC ( a ) ( b ) ( c ) PRD64,09005(001) hep-ex/

24 I I I I CLEO CPV in vs X(use only 1 side) Optimal Observable from CP odd interference between K* and K* 0 (1430) 0.4 ( a ) Data ( b ) Monte Carlo Limit on Higgs like coupling relative to W I I < ξ > τ K 0 π ν τ τ + K 0 π + ν τ τ K 0 π ν τ τ + K 0 π + ν τ M (Kπ) (GeV/c ) sub to PRL hep-ex/

25 Properties Observed by DONUT!!! Mixing?? Mass limit (irrelevant??) M <18 MeV Aleph Method has oddities - see tau000 writeup M <37 MeV from B e Helicity :Michel Params h= =-0.996(0.007) EDM, magnetic moment

26 Tau Review Conclusions 1 Leptonic are apparently very Standard Model Hadronic decays are well measured Hadronic decays provide a lab for QCD with applications well beyond mixing make neutrinoless decay searches exciting CP Violation studies will improve Belle is off to a running start (Babar?) BES/CLEO-C have interesting niches

27 Tau Review Conclusions Remember the on the forehead? Ezekiel 9:4...Walk through the streets of Jerusalem and put a mark on the foreheads of all those who weep and sigh because of the sins they see around them... Why you really should learn about s: Ezekiel 9:5...Follow him through the city and kill everyone whose forehead is not marked. Show no mercy; have no pity!...