j. whitmore beach 2004 june 30, 2004 ktev results: k l ( =e, , ) beach 2004 june 30, 2004 julie...

J. Whitmore BEACH 2004 June 30, 2004

KTeV Results: KKTeV Results: KL L ((=e,=e,,,) )

BEACH 2004June 30, 2004

Julie Whitmore, Fermilab

Physics Motivation - Direct CP Violation KTeV Detector Results Summary

The KTeV Collaboration:Arizona, Campinas, Chicago, Colorado, Elmhurst, Fermilab, Osaka,

Rice, Rutgers, Sao Paulo, UCLA, UCSD, Virginia, Wisconsin


Direct CP Violation in KDirect CP Violation in KLL 00Direct (KL K2 + K1; K2 0*,0Z*)

1124

2.2

0 10)2.16.2(~)(

xA

m

mKBR

W

tL

DIR

The Golden Mode


CPV = Indirect (KL K2 +K1; K1 0+ Interference + Direct (KL K2 +K1; K2 0*,0Z*)

Conserving(KL K2 +K1; K2 0

CP Violation in KCP Violation in KLL 00

120 10)5917(~)( xeeKBR CPVL 120 10)169(~)( xKBR CPVL

Theoretical Predictions

(from theory + BR(KL0))

Theoretical Predictions

120 105.0~)( xeeKBR CPCL 120 105~)( xKBR CPCL

(from theory + BR(Ks0) (NA48))


KTeV Fixed Target RunKTeV Fixed Target Run

KTeV(E832) 96-97 Data Set: 3.3E6 KL 00

KTeV (E799-II) 97 Data Set: 2.7E11 KL Decays

KTeV(E832) 99 Data Set: 3.7E6 KL 00

KTeV (E799-II) 99 Data Set: 3.6E11 KL Decays


The KTeV DetectorThe KTeV Detector

Pure CsI Calorimeter:

(Energy resolution 1% at E = 10GeV, /e rejection of 700)

Transition radiation detectors (p/e rejection of 200)

Drift chambers with resolutions (~100m)

Clean intense beams: (5-8)E12 protons on target per spill • 5-8 x 109 kaons per spill

KTeV (E799-II) Data Set:

6.3E11 Kaon Decays (97 + 99)


Advantage - Dominated by direct CP violation

Disadvantage - 0 difficult; Dalitz decay BR(0 ee ); significant backgrounds

1997 Analyses1. Dalitz Analysis (0 ee )

• Event Selection: 1 , 2 electron-like showers matched to tracks, unbalanced Pt

• Backgrounds: KL 20 , KL 30, n0, 0

• Normalize to KL ee2. Neutral Analysis (0 )

• Special Run - 1 Day of data taking, Single smaller beam

• Normalize to (KL0 0 ) 1999 Data – Dalitz Trigger Prescaled

KKLL

Z vertex

Muon SteelMuon Steel

Muon CountersMuon Counters

KL

e+

e-

CsICsI

from e+e-


BR(KL ) 5.9 x 10-7 (0ee, 1997 Data) [PRD 61,072006 (2000)]

BR (KL ) 1.6 x 10-6 (0, 1997 1 Day) [PLB 447, 240 (1999)]

KKLL DataMC BG Sumn MC MCSignal MC

1997 Data Dalitz Analysis


KKL L ee++ee--

Advantage: fully reconstruct the final state. Disadvantages: not pure direct CP violation

Serious background (KL ee)

Contributions to BR(KL e+e-)• CP Violating: BR ~ (17 ± 9 + 5) x 10-12 (est. from theory+KS 0e+e-)

• CP Conserving: BR ~ 0.5 x 10-12 (est. from theory+ KL )

• Total:BR KL 0e+e-)= (1-3) x 10-11

• New Physics Enhancements in BR

Previous Result: BR (KL 0e+e- )< 5.1 x 10-10 (KTeV1997) [PRL 86, 397 (2001)]


1988 Events76.6 3.3 Est. Background

KKLL e e++ee--

BR(KL e+e-, E*>5MeV) = (6.310.14(stat)±0.42(sys))x10-7 [PRD 64, 012003 (2001)]

L 00,0 ee LeeACC


KKL L ee++ee--

Analysis – 1999 Data • Event selection: 2forming0;

2 electron-like showers matched to tracks, CsI+TRD(/e)

• Backgrounds: KL +-, KL e+acc+rad, and KL ee

• Suppress with kinematic Cuts: |COS()| and min

• Total contribution in the blind analysis box: 3.9 ± 1.4 events (2.9 ± 0.47 events come from KL ee

• Normalize to KL ,ee



CsICsI

Z vertex

KL

e+

e-

from e+e-


KKL L ee++ee--

Signal Ellipse± 2

KL ee; M M

M M

KL e + ACC

KL e+ rad + ACC

XeX

KL

eX

KL

eXeX

Blind Analysis

Box Region


Kinematic Variables for Kinematic Variables for KKL L ee++ee- - and Kand KL L e e++ee--

Cos()

KL0ee

min

KLee

KL0ee

KLeeKLe+e-

KL0e+e-


Kinematic Cuts for Kinematic Cuts for KKL L ee++ee- - and Kand KL L e e++ee--

Phase space cuts optimized• Cuts varied and expected

background and signal acceptance calculated

• 90% CL BR limit determined for each set via Feldman-Cousins technique

• Assume any events are background

• Cuts optimized to yield lowest expected branching ratio limit

• Signal Acceptance: (2.749 ± 0.013)%

• 30% less than 1997 due to accidentals (tighter TRD, phase space, and mass cuts)

• SES: 1.04 x 10-10

Cos

MIN

Cos(<0.745

MIN>0.362


KKL L ee++ee--

BR(KL e+e-) 3.50 x 10-10 (90% C.L.) (1999) [Accepted by PRL]

BR(KL e+e-) 2.8 x 10-10 (90% C.L.) (1997+1999)

1999 Data

Box Region: 130<m<140 MeV/c2

485<meegg<510 MeV/c2

Signal Region:

± 2 in KLe+e-

Background in ellipse:

0.99 ± 0.35


KKL L ++--

Advantage: Probes direct CP violation

Like KL e+e- - fully reconstruct the final state Disadvantages: phase space suppression

• Small relative to the CPC and Indirect CPV

• Potential background (KL )

Contributions to BR(KL +-)

• CP Violating: BR ~ (9 ± 6 + 1) x 10-12(est. from theory + KS 0)

• CP Conserving: BR ~ 5 x 10-12 (est. from theory+ KL ) • Total:BR KL )= (1 – 2) x 10-11

• New Physics Enhancements in BR

Previous limit: BR (KL 0 )< 5.1 x 10-9 (E799-I)


KKL L ++--

1997 Analysis • Event Selection: 2 reconstructing

as a 0; 2 tracks which MIP in the calorimeter, 2 ID muons

• Backgrounds from punch-through and decay-in-flight from +-0 and KL (+ 2ACC);

KL (0.3730.032 evts)

• Suppress with kinematic cuts on M() and M()

• Angular cuts on |COS()| and min less effective than with ee

• Total contribution: 0.87 ± 0.15 events

• Normalize to +-0 decays



CsICsI

Z vertex from

KL


KKL L

Dangerous background for KL 0

Never been observed Analysis

• Event Selection: 2 which do not reconstruct as a 0;

2 tracks which MIP in the calorimeter, 2 ID muons

• Backgrounds from KL (+2ACC), +ACC

• Kinematic Cuts: E

• Total Contribution: 0.155 ± 0.081

• Normalize to KL +-0

QED Pred:BR(KL 9.10.78) x 10-9


KKL L

First observation

4 events seen

BR(KL M>1MeV/c2)95.7

9.5 10))(7.0)(4.10( sysstat

BR(KL E*>10MeV)90.1

8.0 10))(10.0)(42.1( sysstat

[PRD 62, 112001 (2000)]


Kinematic Distributions for KKinematic Distributions for KL L ++- -

and and KKL L ++--

KL

KL0

KL

minCos()

KL0

KL

KL


KKL L

BR(KL ) 3.8 x 10-10 (90% C.L.) [PRL 86, 5425 (2001)]

2 events in signal region

Background MC

Data


Current StatusCurrent Status


SummarySummary

Analyzed 1997 data - BR(KL ) 5.9 x 10-7 (0ee)• B(KL e+e-(6.31 0.14(stat) 0.42(sys))x10-7

• No Dalitz trigger in1999 data • Look forward to future experiments – KOPIO and E391a

Analyzed full KTeV data set (1997 + 1999) - BR(KL e+e-) 2.8 x 10-10 (90% C.L.)

Analyzed 1997 data - BR(KL 3.8 x 10-10 (90% C.L.)• B(KL x 10-9

• Currently analyzing 1999 data

• Combined 1997+1999 data set ~ 2 x 1997

• More accidentals – tighter cuts (lose acceptance)

• Normalize to KL – reduce uncertainties from muon system

• Expected SES (1997+1999) ~ 1 x 10-10

j. whitmore beach 2004 june 30, 2004 ktev results: k l ( =e, , ) beach 2004 june 30, 2004 julie...

Documents

e e slide

e e brk

e e advantage

e e cp conserving

e e cp violating

whitmore beach

e acc rad

csi trd e backgrounds