Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://zebu.uoregon.edu/~uochep/talks/talks04/tau.pdf Äàòà èçìåíåíèÿ: Wed Nov 17 00:24:23 2004 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 09:38:42 2012 Êîäèðîâêà: ISO8859-5 Ïîèñêîâûå ñëîâà: hep-ex

Results on Tau Physics from BaBar

Eric Torrence University of Oregon

Ç Search for Lepton Flavor Violation Ç Study of - 3 h - 2 h + (5 prong) Ç Tau Lifetime
Eric Torrence ICHEP `04 August 16, 2004


The BaBar Experiment

240 220 200

BA B

AR

Integrated Luminosity (fb )

-1

180 160 140 120 100 80 60 40 20 0

PEP-II Delivered 253.55/fb BABAR Recorded 244.06/fb BABAR off-peak 22.68/fb

244 fb-1 recorded, more data on its way ( e + e - BB ) = 1.05 nb ( e + e - + - ) = 0.89 nb Almost 220 million + - events! Results shown today use ~100 fb-1

96% Efficiency

1 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep1 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep1 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep1 Jul 1 May 1 Mar 1 Jan 1 Nov 1 Sep1 Jul 1 May 1 Mar 1 Jan 1 Nov

1999 2000

2001

2002

2003

2004

Eric Torrence

ICHEP `04

August 16, 2004


Lepton Flavor Violation

Limits on Lepton Flavor Changing Decays before BaBar/Belle Ç B ( Å e ) < 1.2 ç10 Ç B ( Å ) < 1.1 ç10
- 11 - 12

at 90% CL [MEGA/LAMPF] at 90% CL [SINDRUM] at 90% CL [CLEO] at 90% CL [CLEO]

Ç B ( Å eee ) < 1.0 ç10

-6 -6

Ç B ( Å ÅÅ ) < 1.9 ç10

Forbidden in SM, but no good theoretical motivation Neutrino Oscillations

- W







Å

Å

-

LFV allowed in principle, but rate is very, very small. O(10-40)? Signature of new physics! Search for Å , lll ,...
Eric Torrence ICHEP `04 August 16, 2004


LFV in Tau Decays Å- - Å
+

-



Å+ -



Å-

Natural part of many models of new physics, particularly those trying to explain neutrino data
B(Å->e) B(->Å) 10 10
-10 M1/2=50

Å Å e

Experimental Bound
-12

10

-4

M1/2=50

Å Å

10
-14 M1/2=200

-6

Experimental Bound

10 10 10

10
-16 M = 2 x 1016 GeV -18

-8 M1/2=200

10 400 500 M0 (GeV)

-10

M = 2 x 1016 GeV

100

200

300

100

200

300

400 500 M0 (GeV)

String inspired, heavy R SUSY [King and Oliveira, 1999] See E. Ma Tau02 proceedings for concise review
Eric Torrence ICHEP `04 August 16, 2004


LFV Signature 1-prong "tag" Å 1-prong "tag"

lll

Ç One prong on "tag" side ( , , e , Å ,...) ~ 85% Ç Strict lepton identification Ç No missing momentum on signal side

vs. m for MC signal
E (GeV)

"Neutrinoless" Decay m = m E = E
rec

0.4 0.2 0

- -> Å-e-e+

-m



rec

-E

beam

Smeared by resolution and radiative effects

-0.2 -0.4 -0.6

Count events in signal box

-0.6

-0.4

-0.2

0

0.2 0.4 M (GeV)

Eric Torrence

ICHEP `04

August 16, 2004


Å lll Analysis

E (GeV)

0.4 0.2 0

qq

0.4 0.2 0 -0.2 -0.4 -0.6

QED

-0.2 -0.4 -0.6 -0.6 -0.4 -0.2 0.4 0.2 0 -0.2 -0.4 -0.6 -0.6 -0.4 -0.2 0 0.2 0.4 0 0.2 0.4

-0.6 -0.4 -0.2 0.4 0.2 0 -0.2 -0.4 -0.6 -0.6 -0.4 -0.2

0

0.2 0.4



Data

0

0.2 0.4

M (GeV)
Require 1-3 topology, reject conversions, Particle ID, plus specific cuts per channel against major backgrounds 3 background PDFs, shape from MC/control, rate from data
Eric Torrence ICHEP `04 August 16, 2004


BaBar Å lll LFV Limits
E (GeV)

- e-e+e0.2 -0

- Å+e-e-

- e-Å+Å-

BABAR

-0.2 -0.4 -0.6

- Å-e+e0.2 -0 -0.2 -0.4 -0.6 -0.6 -0.4 -0.2 0 0.2

- e+Å-Å-

- Å-Å+Å-

-0.4

-0.2

0

0.2

-0.4

-0.2

0

0.2

0.4
2

M (GeV/c )

Mode e-e+e- Å+e-e- Å-e+e- e+Å-Å- e-Å+Å- Å-Å+Å- Eff [%] 7.3 Á 0.2 11.6 Á 0.4 7.7 Á 0.3 9.8 Á 0.5 6.8 Á 0.4 6.7 Á 0.5 Nbgd 1.51 Á 0.11 0.37 Á 0.08 0.62 Á 0.10 0.21 Á 0.07 0.39 Á 0.08 0.31 Á 0.09 Nobs 1 0 1 0 1 0 9 BU0 2.0 ç 10-7 1.1 ç 10-7 2.7 ç 10-7 1.3 ç 10-7 3.3 ç 10-7 1.9 ç 10-7 L

No excess found! Limits ( 1 - 3 ) ç10 @ 90% CL L = 91.6 fb-1, = 0.89 nb PRL 92, 121801 (2004)
Eric Torrence ICHEP `04 August 16, 2004

-7


Old Preliminary BaBar Å Å Limits

Significant background from e + e - Å + Å - and Å Å Require electron or rho tag (no muon or pion tags allowed)
BAB
AR
Preliminary

(GeV/c ) m

L = 63 fb-1, = 0.89 nb Bgd expected: 7.8 Á 1.4 Data observed: 13 = ( 5.2 Á 0.5 ) %

2

2.0

Limit 2.0 ç10

-6

@ 90% CL
1.6

Not competitive due to fluctuation Update with 220 fb-1 expected for Tau04...
Eric Torrence

EC

1.8

-1

-0.5

0

0.5

E (GeV)
ICHEP `04 August 16, 2004


Published Belle Å Å Limits

L = 86.3 fb-1, = ( 11.0 Á 0.5 ) % Expected: 20.2 Á 2.1 Observed: 19 BF Limit 3.1 ç10 @ 90% CL PRL 92, 171802 (2004) Also B ( Å ) < 3.4 ç10 Submitted to PRL
-7 -7

Updates expected this week, see BSM-5 2:30 Tuesday
Eric Torrence ICHEP `04 August 16, 2004


Published Lepton Flavor Violation Limits Limits ( ç10 ) at 90% CL based on ~ 90 fb-1 per experiment
Mode BaBar Belle My Combination -7

B( - Å-Å+Å- ) B( - Å-Å+e- ) B( - Å-e+Å- ) B( - Å-e+e- ) B( - e-Å+e- ) B( - e-e+e- )

1.9 3.3 1.3 2.7 1.1 2.0
-7

2.0 2.0 2.0 1.9 2.0 3.5
-7

0.8 1.4 0.7 1.2 0.6 1.5

BaBar: PRL 92, 121801 (2004) Belle: PLB 589, 103 (2004) Also B ( Å ) < 3.1 ç10 and B ( Å ) < 3.4 ç10 (Belle) B-factories have lowered these limits 10-6 Å 10-7 Over 500 fb-1 (0.5 ab-1) expected in next few years 50 distinct modes listed in PDG with LF, L, or B violation Many interesting channels: lhh , Å ' , p ,... lll limits should approach O(10-8) soon Many models predictions are above this level!
Eric Torrence ICHEP `04 August 16, 2004


Five Prong Tau Decays




W



e+ e/Z

Tau Decays provide a clean laboratory to study QCD - - 0 and - - + - extensively studied worldwide 5-prong modes suffer from lack of statistics...
200
Events/(0.1 GeV/c2)

50

CLEO
100

1pr tag
3h-2h+


lept tag
CLEO saw 295 events 25 (1.7 fb-1) PRL 73, 934 (1994)

0

0

2

4

0

2

4 M5 (GeV/c2)

0

Eric Torrence

ICHEP `04

August 16, 2004


BaBar 5-prong Analysis 3 h - 2 h + mass compared to TAUOLA (phase space)
3000 2500 2000 1500 1000 500 0 0.6 0.8 1 1.2 1.4 1.6 1.8 3h2h+ 2 2.2 2.4
2

Events/0.04 GeV/c

2

BABAR
preliminary

- 3h-2h+



Data 3-2+ MC other tau qqbar

Mass (GeV/c )

1-5 topology, lepton tag, thrust, Pt/Emiss, no kaon id (yet) veto e-, 0, and conversions from signal side

Efficiency: 7.5%, Purity: 79%, Events: 15,869, Lumi: 110.7 fb-1 Backgrounds mostly from other tau decays with 0 or Ks
Eric Torrence ICHEP `04 August 16, 2004


Preliminary 5-prong Results
Tag Efficiency [%] Purity [%] Events B ( - 3h- 2h+ ) Electron 4.6 79 9668 (8.52 Á 0.09 Á 0.40) ç 10- Muon 2.9 79 6201 (8.54 Á 0.11 Á 0.45) ç 10-

4 4

Babar Preliminary: hep-ex/0408050 Branching Fraction
Events/0.0125 GeV/c

Hadronic Structure in h+h- pairs
4500 4000 3500 3000 2500 2000 1500 1000 500 0 0.2 0.4 0.6 0.8 1 1.2
2
2

BaBar

Preliminary

8.5 Á 0.4

6 pairs/ev.

BABAR
preliminary
Data 3-2+ MC background

Opal Aleph Cleo PDG

9.1 Á 1.5 8.0 Á 1.7 7.7 Á 1.0

0

8.2 Á 0.6 Phase Space

h+h- Mass (GeV/c )

Monte Carlo Future Plans: 6 8 10 12 + -4 B(3h 2h ) [10 ] Measure 5h 0, 5h 20 modes Separate kaons from pions Study hadronic structure in detail
Eric Torrence ICHEP `04 August 16, 2004


Preliminary Tau Lifetime Ç Very clean 1-3 sample Ç Reconstruct r- decay length from primary IP to 3-track vertex Ç Use simple mean <> to reduce syst.
decay_length_allcuts_unblinded_tau

1-prong 3-prong

Entries Entries

110245 145675 0

Events per 100 Åm

10

4

BABAR
preliminary

Mean Underflow RMS

Overflow

0.0240731 0 0.0406002

10

3

10

2

Data tau uds cc bb

BaBar Delphi

290.8 Á 2.2 291.4 Á 3.0 293.2 Á 2.5 289.2 Á 2.1 290.1 Á 1.9 289.0 Á 4.9 290.6 Á 1.1
290

Preliminary

10

1 -0.3 -0.2 -0.1 0 0.1 0.2

L3



0.3 cm

Opal Aleph

Lifetime with 30 Cleo 290.8 Á 1.5 ( stat ) Á 1.6 ( syst ) fs (prelim.) Uncertainties will be significantly reduced for publication (80 fb-1)
Eric Torrence ICHEP `04

fb-1

PDG
285

295 Tau Lifetime (fs)

August 16, 2004


Summary Lepton Flavor Violation Ç B ( lll ) < ( 1 - 3 ) ç10 published Ç Prelim. result on B ( Å ) to be updated shortly Hadronic Structure Ç Prelim. results with 16k - 3 h - 2 h + events Ç Much more to come here
-7

Tau Lifetime Ç Prelim. lifetime measurement among world's best Ç Improvements and publication expected soon

First results on tau physics from BaBar are just now being published There is a lot of physics to be extracted from this huge data sample See Tau04 (Nara, Japan, September 14-17) for more
Eric Torrence ICHEP `04 August 16, 2004