LFV and LUV at CLEO• Lepton-Flavor Violation:

– Probe non-SM physics and/or SM extensions– Here, report on Upsilon(1S)

• Complements other studies

• MEG (e) @PSI

• Many searches for

• Lepton UniVersality:– “Sometimes a lepton is just a lepton” (Freud [sic])– If not, then something interesting!

LFV in the charged sector

d

tb

1 2 3Generation

Quarks

Leptons

e

cu s

e

En

erg

yQuark mixing (CKM)

Neutrino Oscillations

Mixing in the chargedLepton sector?

Lepton Flavor Violation• Sakharov Conditions for Matter- Universe:

– Baryon Number Violation (B [L=lepton no.])– C-parity (CP-parity) Violation– Universe non-thermal for some time

• B, L “accidental symmetries”, but B-L good QN

LFV summary: decay

1940 1950 1960 1970 1980 1990 2000 2010

10-1

10-2

10-3

10-4

10-5

10-6

10-7

10-6

10-9

10-10

10-11

10-12

10-13

10-14

10-15

→ e → eA → eee

SUSY SU(5)

BR( e ) = 10-13

A eA = 10-15

BR( ) = 10-8

SUSY SU(5)

BR( e ) = 10-13

A eA = 10-15

BR( ) = 10-8

Current Limits:BR(+ e+ ) < 1.2 x 10-11 (MEGA)1)

Ti → eTi < 7 x 10-13 (SINDRUM II)2)

Current Limits:BR(+ e+ ) < 1.2 x 10-11 (MEGA)1)

Ti → eTi < 7 x 10-13 (SINDRUM II)2)

1) hep-ex/9905013 2) A. van der Schaaf, priv. comm.

BR

Year

“Supersymmetric parameterspace accessible by

LHC”

“Supersymmetric parameterspace accessible by

LHC”

(Ritt, MEGs)

Upsilon Decays access a different kinematic regime!

Or add interactions at new scale

Datta et al (PRD60, 014011, 1999: Yl<0.01; J/pl<6x10-7

CLEO search• The detector: CLEO was the first “CLEO-type”

detector

10 GeV energy regime;

Good resolution!

Experimental Search• Search for Y; e• Off-resonance samples used for control &

comparison.

• Primary search variables are scaled momenta of two charged tracks.

• Extended maximum likelihood used to evaluate event-by-event consistency with LFV

Signal parametrized as f(scaled electron,scaled muon momentum)

Known backgrounds saturate observables

No signal observed over backgroundset limits

Lepton Universality• Here, “LUV”(nS)l+l- universal (if no BSM).• LUV NOT statement that (nS)l+l-=(mS)l+l-.• In case of Upsilon:

– Y easiest • 2 Back-to-Back tracks• Direct Continuum Subtraction

– Yee coupling extracted through total Upsilon width• Bhabha subtraction otherwise BIG

– Here, discuss measurement of Y + comparison with Y and Yee

– Very similar to Y: straightforward ON-OFF – To minimize systematics, use consistent muon ID for

both dilepton modes

Dielectronic widths (PRL96, 092003, 2006)

NOTE: Precision measurements – typically 2%!

Measure tau pair xsct w/ many modes:

“Expected ratio”=0.82 (phase space)

Compare on-off resonance yields:

MC to derive efficiency

RESULTS (relative)

Internal consistency

Absolute BF

(+ratio just presented)

Conclusions• Standard Model once again triumphs.

– Although differences in dileptonic widths, resonance-to-resonance, are interesting…

• No indication of departures from SM, but keep looking…

• No more Upsilon resonance dataResonance program for J/psi underway.

LFV in the SM vs. SUSY (meg)

e e

W

e0

e

2emSMSM SUSYSUSY

SM

604

4B 10R( )

W

em

m

probes slepton mixing matrix

SUSYBR( )e

4

5 2

SUS2

Y

2100 GeV

10 tanem

mm

≈ 10-12

• LFV in the SM is immeasurable small• SUSY models predicts BR(→ e) just below the

current experimental limit of 1.2 x 10-11

• Decay → e is free of “SM background” (no hadronic corrections)

• LFV in the SM is immeasurable small• SUSY models predicts BR(→ e) just below the

current experimental limit of 1.2 x 10-11

• Decay → e is free of “SM background” (no hadronic corrections)

The discovery of → e would by physics beyond the SMThe discovery of → e would by physics beyond the SM