30/05/2007 Salvatore Fiore K0 K0 analisys: some updates 1

analisys:Systematics checks

0000 KK)a(f

Salvatore Fiore

30/05/2007 Salvatore Fiore K0 K0 analisys: some updates 2

Main ingredients

• Cuts’ fine tuning to maximize sensitivity• 2-dim sidebands: “sideboxes”• Narrowed sideboxes approaching signal box• MC photon efficiency curve• EMC Cluster energy-position: MC-Data

agreement

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Cuts optimization

Analysis cuts’ bounds have been chosen looking only at signal and bkgd MC, as each cut was added. However, to exclude personal biases from the analysis, an optimization on the selection cuts has been performed looking again only at signal and bkgd MC’s, and minimizing the quantity

Here the quantity “#ev @ 90% CL” is evaluated from the background surviving events, using Feldman Cousins method for sensitivity (this is ok, no “expected mean bkgd” inconsistency)

effic.l. 90% @ ev#

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vs. cuts choice

<1005Me<1005MeVV

<1010Me<1010MeVV

<1015Me<1015MeVV

±100Me±100MeVV22

35.535.5

±200Me±200MeVV22

26.226.2 19.519.5 29.629.6

±300Me±300MeVV22

23.223.2 18.018.0

±400Me±400MeVV22

22.522.5 18.218.2 31.231.2

±500Me±500MeVV22

18.118.1

Previous choicePrevious choice

effic.l. 90% @ ev#

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Optimization effects

• With this procedure, two of the last four kine cuts have been removed (non effective on bkgd)

• The other cuts prooved to be already optimized, only E2

miss-P2miss slightly loosened

(±200 ±300)• Signal efficiency after this procedure is

21.5% (was 20.0%) • Residual MC background events now are 0• Residual Data events still 1

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MC-Data agreement checks

To make sure of the MC correct behaviourMC correct behaviour, we made some checks on our selection variables:

• We chose a sideband control samplesideband control sample, made by those events which did not survive both “Kdid not survive both “KSSKKSS invariant mass” and “Einvariant mass” and “E22miss-Pmiss-P22miss” cutsmiss” cuts.

• For these events, we evaluated the MC/data ratioMC/data ratio for KSKS invariant mass and E2miss-P2miss distribution.

From last phidec meeting

From last phidec meeting

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2001-02 MC-Data comparison

MC/Data: 1.181±0.020MC/Data: 1.181±0.020 MC/Data: 1.153±0.020MC/Data: 1.153±0.020

From last phidec meeting

From last phidec meeting

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2005 MC-Data comparison

MC/Data: 1.118±0.011MC/Data: 1.118±0.011 MC/Data: 1.110±0.012MC/Data: 1.110±0.012

From last phidec meeting

From last phidec meeting

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MC-Data agreement

The different distribution ratios are in good good agreementagreement, and confirm the generated 1:1confirm the generated 1:1 Mc-Data scaling factor.

MC/Data ratios for the same distributions, looking at the events which do not pass that single cut (standard sidebands) have been checked.

1.1713 ± 0.0201.2647 ± 0.019

2001-022001-02

1.2171 ± 0.011 1.1713 ± 0.020

20052005

From last phidec meeting

From last phidec meeting

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SidebandsSideboxes

To better understand MC-data agreement, evaluated on the sidebands of our selection variables, the comparison is now made on a 2-dim plot:

E2 m

iss-

P2 m

iss

invmassKK

Signal regionSignal region Sidebox1:Sidebox1:Unmatched invmassKK Unmatched invmassKK

Sidebox2:Sidebox2:Unmatched both Unmatched both

Sidebox3:Sidebox3:Unmatched EUnmatched E22

missmiss-P-P22missmiss

MCMCdatadata

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MC/data ratios in sideboxes

MC/data events ratios are calculated in each sidebox, before the photon cuts:

E2 m

iss-

P2 m

iss

invmassKK

Signal region:Signal region:37/4337/43

Sidebox1:Sidebox1:1.5391.539±±0.0230.023

Sidebox2:Sidebox2:1.13891.1389±±0.00980.0098

Sidebox3:Sidebox3:1.3641.364±±0.0270.027

Signal box:In agreement within 2σwith sidebox3In agreement within 2.5σwith average ratio

Sidebox3:20% more than sidebox2

Sidebox1:35% more than sidebox2

Average ratio:Average ratio:1.24661.2466±±0.00870.0087

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Approaching signal box

To better check the sideboxes, “approaching sidebands”have been used to see how the background behavesnext to the signal box:

E2 m

iss-

P2 m

iss

invmassKK

Sidebox3a:Sidebox3a:2.112.11±±0.850.85

Average ratio:Average ratio:1.1621.162±±0.0780.078

Sidebox2a:Sidebox2a:1.1061.106±±0.0970.097

Sidebox1a:Sidebox1a:1.201.20±±0.130.13

The same procedure The same procedure have been applied after have been applied after the photon cuts, using the photon cuts, using the full sideboxesthe full sideboxes

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MC/data ratios overview

Before phot.Before phot. Before phot.Before phot.

approachingapproachingAfter phot.After phot.

SignalSignal 37/4337/43 0/10/1

SideboxSidebox11

1.5391.539±±0.0230.023 1.201.20±±0.130.13 1.651.65±±0.260.26

SideboxSidebox22

1.13891.1389±0.009±0.00988

1.1061.106±0.09±0.0977

1.0241.024±±0.070.0744

SideboxSidebox33

1.3641.364±±0.0270.027 2.112.11±±0.850.85 1.441.44±±0.270.27

AveragAveragee

1.24661.2466±0.008±0.00877

1.1621.162±0.07±0.0788

1.1461.146±±0.070.0700

•Before Before phot.phot.•Before Before phot.phot.

approachingapproaching•After phot.After phot.

Adding photon cuts Adding photon cuts and approaching and approaching signal box each signal box each sidebox scales sidebox scales correctlycorrectly

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Photon efficiency curve

• GEANFI MC photon efficiency is optimized applying an efficiency corection through an hit-miss: some photon clusters are thus flagged as “not seen in data”.

• Removing these clusters fom our Signal MC, efficiency decreases from 21.5% to 20.6% (4% reduction)

• In MC bkgd, no event surviving kine cuts contains such photons: no effect on bkgd evaluation.

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EMC Cluster energy: MC vs data

• MC-data agreement for clusters’ energy and angles has been checked: these distributions are plotted for events surviving “photon” cuts, but without applying all the kine cuts

E() (MeV) E() (MeV)

SpectraSpectra MC/dataMC/data

MCMCdatadata

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Cluster positions: MC vs data

• Theta angle distributions:

• Phi angle distributions:

MCMCdatadata

MC/dataMC/data

MC/MC/datadata

MCMCdatadata

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Events undergoing “photon” selection

The events that survive all kine cuts are (in bkgd MC) 21 ISR eventsISR events phiKsKl with one radiated

photon

• 33 of these ISR photons reach the EMCISR photons reach the EMC and make a cluster

• The other clustersother clusters of these 21 events are:– pions, muons, electronspions, muons, electrons reaching EMC– uncorrlated backgrounduncorrlated background

• No FSR events among theseNo FSR events among these

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Present status summary

• 2001-2002-2005 data + MC (+2004, data only)• Signal efficiency 20.6%• Selection cuts:

– TriggerTrigger requirement– EVCLEVCL: KSKL stream– Vertices:Vertices:two inside a fiducial volume of 3cm radius and ±8cm in z around

IP – # of tracks# of tracks: two tracks attached to each vertex are required– KKSS invariant mass invariant mass reconstructed by π+π- tracks: 4 MeV circle cut applied

around KS reco mass in m(K1) vs m(K2) plane– ReconstructedReconstructed m(m(ff00,a,a00)) < 1010MeV– EE22

missmiss-P-P22missmiss between -300 and 300 MeV2

– Photon request: Photon request: • One cluster not associatedOne cluster not associated with tracks• Cluster energyCluster energy compatible with missing momentum• ““photon” directionphoton” direction compatible with KSKS (scalar meson) momentum

• 0 MC bkgd events – 1 data event

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Present status summary

The upper limit is calculated as:

with:

ε)ππB.R.(K21)e(eLdt

90%CL @ )UL(B.R.(

2S

sig

)00KK

b3.09Φ)eσ(e

22S (0.686))ππB.R.(K

20.6%

2004 adding 2000pb

05-02-2001 for 1410pb Ldt1-

-1

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Upper Limit Scenario

• Upper limit evaluation method: – We are working in a bayesian approach with flat prior

(O. Helene, NIM212(1983) 319, as for Kse+e- analysis)

• With today’s numbers, without accounting for MC/data ratios from the sideboxes, the U.L. scenario is:1.7·10-8 for 2001-02-051.2·10-8 for 2001-02-05 + 2004 if MC04 shows no event1.1·10-8 for 2001-02-05 + 2004 if MC04 shows 1 event8.9·10-9 for 2001-02-05 + 2004 if MC04 shows 2 events

• We expect 15% variation of these estimates once MC/data ratios are taken into account and is exactly calculated

Φ)eσ(e

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Theoretical estimates

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What’s next?• Selection cuts and analysis strategy are now well defined well defined

and optimizedand optimized.• MC-Data agreement have been better verified agreement have been better verified and

Mc/data ratios are obtainedMc/data ratios are obtained, to be used as syst. on used as syst. on expected bkgd expected bkgd

• Still WaitingStill Waiting for 2004 MC for 2004 MC production to include 2004 statistics: it will be ready for ferragosto’s BBQ.

• Further checks:– Exact calculation of run by run using hepdb’s

sqrts and cross-section shape.– Repeat UL calculation to account for MC/data ratios– Separe different contributions in the sideboxes to better

explain different ratios

Φ)eσ(e

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