Recent CLEO Results on Tau Hadronic Decays J.E. Duboscq Cornell - PowerPoint PPT Presentation

Recent CLEO Results on Tau Hadronic Decays J.E. Duboscq Cornell University Tau04, Nara Japan

CLEO Hadronic Tau Results The CLEO3 Detector Tau Decays to 3 Charged Hadrons + ν PRL90:181802,2003 Structure of KKπ and Wess-Zumino PRL92:232001,2004 JED Tau04 2

The CLEO3 Detector CLEOIII 2230104-001 CL EO III Solenoid Coil Barrel Calorimeter RICH Drift Chamber Silicon / beampipe SC Quadrupole Pylon 14007 01-002 Endcap SC Calorimeter Quadrupoles Rare Earth Iron Quadrupole Polepiece Magnet Barrel Muon JED Tau04 3 Iron Chambers

Tau to 3h ± + ν τ - → h - h + h - ν decays predominantly to pions K - π + π - final state important to strange spectral function, m s , V us K - K + π - state probes Wess-Zumino term K - K + K - state as yet unobserved The Data Sample: 3x10 6 tau pairs at Υ (4s) produced at CESR τ-→ h-h+h- ν JED Tau04 4

Hadronic Particle ID 33 5 010 3 - 001 Combine RICH and dE/dx 100 Efficiency (%) 8 0 6 0 Use DATA D* → Dπ, D → 4 0 K Kπ to obtain PID ε and 2 0 2 5 fake rates Fak e Rat e (%) K f ak e s 2 0 f ak e s K 1 5 Cross check with wrong 10 5 sign K in τ - → K + π - π + ν 0 0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0 3 . 5 4 . 0 search Mom en t um ( G e V/ c) (Use only loose dE/dx for π in KKπ - KKK not a background !) τ-→ h-h+h- ν JED Tau04 5

Event Selection Select 1 vs 3 tracks (using Thrust) Require e/ µ / ρ / π tag Reject events w/ extra showers (3h π 0 rejection) Missing momentum, E vis cuts reject 2 γ background K s 0 rejection for K ππ mode Use KORALB, JETSET, GEANT for efficiency (use data for PID) τ-→ h-h+h- ν JED Tau04 6

3h Results Mode Data τ bgd qq bgd ε (%) 33 5 0 1 0 3 - 002 1 00 πππ 43543 3207±57 152±12 10.27±0.08 πππ KK π 2000 ( a ) ( c ) K ππ 3454 1475±38 57±8 11.63±0.12 5 0 KK π 932 86±9 19±4 12.48±0.11 1 000 Ev e nt s / 20 (MeV/c 2 ) KKK 12 4±2 0.4±0.6 9.43±0.10 0 0 ( b ) ( d ) Largest τ bgd from other KKK K ππ D a t a a ll M C τ→ 3h( π 0 ) ν modes B ac kgrou n d 2 1 2 5 C o nt i n uu m B ac kgrou n d Use MC to get feed-across 0 0 For KKK use data to get feed- 0 . 5 0 . 9 1 . 3 1 . 4 1 . 6 1 . 7 1 . 8 ( 3 h) Mass (GeV/c 2 ) I across KK π Substructure tuned to fit data τ - → h-h+h- ν JED Tau04 7

3h Substructure Plots 33 5 0 1 0 3 - 00 3 6000 πππ ππ ( a ) D a t a Very Good Data a ll M C 4 000 B ac kgrou n d MC agreement 2 000 C o nt i n uu m Ev e nt s / 2 0 (MeV/c 2 ) B ac kgrou n d 0 2 5 0 KK π ( b ) ( c ) K π Used 3 π , K ππ KK 5 0 1 2 5 tuning from TAU02 0 0 K ππ 2 00 ( e ) ( d ) ππ K π Tuned KK π 2 5 0 1 00 substructure: Less 0 0 1 . 1 0 .3 0 . 6 1 . 0 1 . 4 0 . 7 h+h Mass (GeV/c 2 ) K*, more ρ’, no ρ’’ I τ-→ h-h+h- ν JED Tau04 8

3h Systematics 3% PID systematic 2% each systematic for Lumi, σ ( ττ ), track finding 1% each syst for τ backgrounds, CC cuts PID Fake rate syst 0.1%/9%/2%/12% MC/Data studies, τ - → K+ π - π + ν search qq background - MC vs data above tau mass syst = 0.2%/ 2%/1%/3% KK π substructure 2% τ - → h-h+h- ν JED Tau04 9

Final 3h Results B( τ - →̟ - ̟ + ̟ - ν τ ) = 9.13±0.05±0.46% B( τ - → K - ̟ + ̟ - ν τ ) = 0.384±0.014±0.038% B( τ - → K - K + ̟ - ν τ ) = 0.155±0.006±0.009% B( τ - → K - K + K - ν τ ) < 3.7x10 -5 @90% CL First direct 3 π result K ππ consistent w/OPAL (0.360±0.082±0.048%) & CLEO2 (0.346±0.023±0.056%) , higher than ALEPH (0.214±0.037±0.029%) Best precision on KK π Most stringent limit on KKK τ - → h-h+h- ν JED Tau04 10

KK π Structure - Wess Zumino Anomaly Simplest τ decay picture: Vector (axial) current produces even (odd) numbers of pseudoscalars WZ Anomaly allows parity flip and allows a violation of this rule Golden mode τ→η̟̟ 0 ν previously observed by CLEO (no axial component) τ→ KK π ν has both axial and vector (WZ) contribution WZ effects rate and substructure of KK π KK π - WZ Anomaly JED Tau04 11

Structure of tau to 3h ν Decays SM matrix element M ∝ L µ J µ τ ν Define: Q µ =(q 1 +q 2 +q 3 ) µ , s i =(q j +q k ) 3h J is a sum over 4 form factors: J= ∑ f i (q 1 ,q 2 ,q 3 ,Q)F i (s 1 ,s 2 ,Q) f i are kinematics - F i are Form Factors (physics) F 1 ,F 2 are axial terms F 3 is the WZ vector term f3=i ε α βγ q 1 α q 2 β q 3 γ F 4 is the scalar current (negligible) Kuhn, Mirkes, Z.PhysC56, 661(1992) KK π - WZ Anomaly JED Tau04 12

Structure of tau to 3h ν Decays Integrate over ν direction Two remaining Euler angles are kinematically determined d Γ ( τ→ KK π )/dQ 2 ds 1 ds 2 ∝ W A (F 1 ,F 2 )+W B (F 3 ) No interference between Axial and WZ term Measurement possible entirely by using Dalitz plot and Q 2 KK π - WZ Anomaly JED Tau04 13

Decker etal, ZPhysC.58,445(1993) The Physics We Fit Finkemeir & Mirkes, ZPhysC69, 243(1996) a 1 →ρ ( ’ ) π , ρ ( ’ ) → KK F 1 ∝ BW a1 (Q 2 ) x ( BW ρ (s 2 )+ β ρ BW ρ ’ (s 2 ) ) a 1 → K*K, K* → K π F 2 ∝ R F BW a1 (Q 2 ) x BW K* (s 1 ) Text ρ ( ’ , ’’ ) → K*K, K* → K ̟ ρ ( ’ , ’’ ) →ω̟ , ω → KK ½ ( BW ρ (Q 2 )+ λ BW ρ ’ (Q 2 )+ δ BW ρ ’’ (Q 2 ) ) x F 3 ∝ R B ( BW ω (s 2 )+ α BW K* (s 1 ) ) Five real fit parameters to KK π , K π , KK masses KK π - WZ Anomaly JED Tau04 14

The Data and Fit Procedure Use 7 .09x10 6 τ pairs from CLEO3 Use same cuts as τ→ 3h ν analysis 2255 signal events, 256±16±46 background Obtain consistent overall Branching Fraction Use unbinned extended Maximum Likelihood fit including background term PDF = PDF(KK π ) x PDF(KK) x PDF(K π ) Use best known params for BW’ s KK π - WZ Anomaly JED Tau04 15

Fit Results Shown is total fit and 3351203-007 240 600 (a) (b) contributions from Axial 160 400 and WZ components ≈1/2 is from WZ 80 200 Events/20 MeV 0 0 α=0.471±0.060±0.034 1.2 1.4 1.6 1.8 0.6 0.8 1.0 1.2 K+ mass (GeV/c 2 ) K K+ mass (GeV/c 2 ) λ =-0.314±0.073±0.080 I I I 200 (c) δ =0.101±0.020±0.156 Data RB=3.23±0.26±1.90 Fit Wess-Zumino RF=0.98±0.15±0.36 100 Axial Vector Backgrounds Γ WZ 0 0.9 1.1 1.3 1.5 =55.7±8.4±4.9% K K+ mass (GeV/c 2 ) I Γ Tot KK π - WZ Anomaly JED Tau04 16

Substructure Result Relative rates in Kuhn & Mirkes model Axial current: τ→ a 1 (→ρ ( ’ ) ̟ , K*K) ν Vector current (WZ): τ→ ρ ( ’ , ’’ ) ( → K*K , ω̟ ) ν ω̟ ρ (’) ̟ R Axial =2.50.8±0.4% R WZ =3.4±0.9±1.0% K*K K*K R WZ =60.8±8.5±6.0% R Axial =46.8±8.4±5.2% Decay dominated by K*K, 50/50 WZ and Axial B(a1 to K*K)=2.2±0.5% consistent w/ previous CLEO ππ 0 π 0 result Axial component much smaller than ALEPH CVC estimate from DM1, +6 94 DM2 data -8 % CERN EP99-026 KK π - WZ Anomaly JED Tau04 17

Angular Distributions 3351203-008 β : ∠ P(KKpi) in lab frame, 200 200 p K xp π 100 θ : ∠ P( τ ) in lab, P(KK π ) in τ 100 frame (a) (b) 0 0 ψ : ∠ P( τ ), P(lab) in KK π frame Events 1 0 1 1 0 1 I I cos cos 200 Data Angles are all expressible in Vector + Axial Vector terms of observables Axial Vector Only All Backgrounds 100 (c) Angles alone are not enough to 0 1 0 1 extract WZ/Axial contributions I cos KK π - WZ Anomaly JED Tau04 18

Summary Using CLEO3, we have presented: 3 First direct B( τ→ 3 π ν ) result ✓ B( τ→ K ππ ν ) consistent w/OPAL and CLEO, higher than ALEPH ✓ Most stringent limit on τ→ KKK ν ✓ Best precision on B( τ→ KK π ν ) ✓ First Study of WZ and Axial parts of τ→ KK π ν ✓ Breakdown of KK π in Kuhn+Mirkes model JED Tau04 19