j. whitmore beach 2004 june 30, 2004 ktev results: k l ( =e, , ) beach 2004 june 30, 2004 julie...
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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
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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))
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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)
J. Whitmore BEACH 2004 June 30, 2004
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-
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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)]
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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
Muon SteelMuon Steel
Muon CountersMuon Counters
CsICsI
Z vertex
KL
e+
e-
from e+e-
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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-
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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)
J. Whitmore BEACH 2004 June 30, 2004
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
Muon SteelMuon Steel
Muon CountersMuon Counters
CsICsI
Z vertex from
KL
J. Whitmore BEACH 2004 June 30, 2004
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
J. Whitmore BEACH 2004 June 30, 2004
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)]
J. Whitmore BEACH 2004 June 30, 2004
Kinematic Distributions for KKinematic Distributions for KL L ++- -
and and KKL L ++--
KL
KL0
KL
minCos()
KL0
KL
KL
J. Whitmore BEACH 2004 June 30, 2004
KKL L
BR(KL ) 3.8 x 10-10 (90% C.L.) [PRL 86, 5425 (2001)]
2 events in signal region
Background MC
Data
J. Whitmore BEACH 2004 June 30, 2004
Current StatusCurrent Status
J. Whitmore BEACH 2004 June 30, 2004
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