1. analisys: Systematics checks
Salvatore Fiore
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

2. Salvatore Fiore K0 K0  analisys: some updates
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
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

3. Salvatore Fiore K0 K0  analisys: some updates
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 90% CL” is evaluated from the background surviving events, using Feldman Cousins method for sensitivity (this is ok, no “expected mean bkgd” inconsistency)
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

4. Salvatore Fiore K0 K0  analisys: some updates
vs. cuts choice
<1005MeV
<1010MeV
<1015MeV
±100MeV2
35.5
±200MeV2
26.2
19.5
29.6
±300MeV2
23.2
18.0
±400MeV2
22.5
18.2
31.2
±500MeV2
18.1
Previous choice
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

5. Salvatore Fiore K0 K0  analisys: some updates
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 E2miss-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
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

6. MC-Data agreement checks
From last phidec meeting
To make sure of the MC correct behaviour, we made some checks on our selection variables:
We chose a sideband control sample, made by those events which did not survive both “KSKS invariant mass” and “E2miss-P2miss” cuts.
For these events, we evaluated the MC/data ratio for KSKS invariant mass and E2miss-P2miss distribution.
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

7. Salvatore Fiore K0 K0  analisys: some updates
MC-Data comparison
From last phidec meeting
MC/Data: 1.181±0.020
MC/Data: 1.153±0.020
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

8. Salvatore Fiore K0 K0  analisys: some updates
2005 MC-Data comparison
From last phidec meeting
MC/Data: 1.118±0.011
MC/Data: 1.110±0.012
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

9. Salvatore Fiore K0 K0  analisys: some updates
MC-Data agreement
From last phidec meeting
The different distribution ratios are in good agreement, and confirm 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.
± 0.019
± 0.020
± 0.011
± 0.020
2005
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

10. Salvatore Fiore K0 K0  analisys: some updates
SidebandsSideboxes
To better understand MC-data agreement, evaluated on the sidebands of our selection variables, the comparison is now made on a 2-dim plot:
Sidebox1:
Unmatched invmassKK
Signal region
E2miss-P2miss MC
data
Sidebox2:
Unmatched both
Sidebox3:
Unmatched E2miss-P2miss
invmassKK
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

11. MC/data ratios in sideboxes
MC/data events ratios are calculated in each sidebox, before the photon cuts:
Signal region:
37/43
Sidebox1:
1.539±0.023
Signal box:
In agreement within 2σ
with sidebox3
In agreement within 2.5σ
with average ratio
Sidebox3:
20% more than sidebox2
Sidebox1:
35% more than sidebox2
E2miss-P2miss
Sidebox3:
1.364±0.027
Sidebox2:
1.1389±0.0098
invmassKK
Average ratio:
1.2466±0.0087
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

12. Approaching signal box
To better check the sideboxes, “approaching sidebands”
have been used to see how the background behaves
next to the signal box:
Sidebox1a:
1.20±0.13
The same procedure have been applied after the photon cuts, using the full sideboxes
Sidebox3a:
2.11±0.85
Sidebox2a:
1.106±0.097
Average ratio:
1.162±0.078
E2miss-P2miss
invmassKK
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

13. MC/data ratios overview
Before phot.
approaching
After phot.
Signal
37/43
0/1
Sidebox1
1.539±0.023
1.20±0.13
1.65±0.26
Sidebox2
1.1389±0.0098
1.106±0.097
1.024±0.074
Sidebox3
1.364±0.027
2.11±0.85
1.44±0.27
Average
1.2466±0.0087
1.162±0.078
1.146±0.070
Before phot.
approaching
After phot.
Adding photon cuts and approaching signal box each sidebox scales correctly
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

14. 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.
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

15. 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
Spectra
MC/data MC
data
E(g) (MeV)
E(g) (MeV)
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

16. Cluster positions: MC vs data
MC/data
Theta angle distributions:
Phi angle distributions:
MC/data MC
data
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

17. Events undergoing “photon” selection
The events that survive all kine cuts are (in bkgd MC) 21 ISR events phiKsKl with one radiated photon
3 of these ISR photons reach the EMC and make a cluster
The other clusters of these 21 events are:
pions, muons, electrons reaching EMC
uncorrlated background
No FSR events among these
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

18. Present status summary
data + MC (+2004, data only)
Signal efficiency 20.6%
Selection cuts:
Trigger requirement
EVCL: KSKL stream
Vertices:two inside a fiducial volume of 3cm radius and ±8cm in z around IP
# of tracks: two tracks attached to each vertex are required
KS invariant mass reconstructed by π+π- tracks: 4 MeV circle cut applied around KS reco mass in m(K1) vs m(K2) plane
Reconstructed m(f0,a0) < 1010MeV
E2miss-P2miss between -300 and 300 MeV2
Photon request:
One cluster not associated with tracks
Cluster energy compatible with missing momentum
“photon” direction compatible with KSKS (scalar meson) momentum
0 MC bkgd events – 1 data event
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

19. Present status summary
The upper limit is calculated as:
with:
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

20. Salvatore Fiore K0 K0  analisys: some updates
Upper Limit Scenario
Upper limit evaluation method:
We are working in a bayesian approach with flat prior (O. Helene, NIM212(1983) 319, as for Kse+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
1.2·10-8 for if MC04 shows no event
1.1·10-8 for if MC04 shows 1 event
8.9·10-9 for if MC04 shows 2 events
We expect 15% variation of these estimates once MC/data ratios are taken into account and is exactly calculated
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

21. Salvatore Fiore K0 K0  analisys: some updates
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

22. Theoretical estimates
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

23. Salvatore Fiore K0 K0  analisys: some updates
What’s next?
Selection cuts and analysis strategy are now well defined and optimized.
MC-Data agreement have been better verified and Mc/data ratios are obtained, to be used as syst. on expected bkgd
Still Waiting 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
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates

24. Salvatore Fiore K0 K0  analisys: some updates
30/05/2007
Salvatore Fiore K0 K0  analisys: some updates