Status Report on

C. Di Donato, B. Di Micco, M. Jacewicz

Phi-Decay WG Meeting

February 9 2010

Outline

• Analysis

• Data-MC comparison

• Momenta Smearing

• Evaluation of systematics

• Discussion with referee

• New smearing method

• Track efficiency correction applied on MC (as in the Memo343);

• Cross-check with Kinematic fit

• PCV EVCL vs tracks selected in the analysis

Analysis Event Signature:

2 Prompt Neutral Clusters: |tcl-lcl/c|<5t

Recoil photon: most energetic cluster with E250 MeV2 tracks closest to IP (using PCA, no vertex requirement)

Kinematical Constraints:Two body decay kinematics to calculate E recoil kinematics to calculate : |Et-Pt|<10 MeV (EtPt)Best Photon: we choose one PNC with <0.13 rad to the

calculated (OPAN) Background: main one is 0: M(M

in the 0 rest frame cos

Only barrelTOF(Time Of Flight cut to reject bhabha background)-ANGLE

DATA-MC comparison and MC smearing

Let’s go back to the smearing, starting from control sample selected to check Data-MC: selected using reversed cut on cos

we look at missing mass from +-

Data – MC and smearing: first approach

Missing mass on control sample

We find discrepancy and try to solve smearing the Pt

OLD APPROACH

After Smearing

OLD APPROACH

Only background is included

After Smearing

OLD APPROACH

All background is included

Residual discrepancy on the right tail.

Smearing method?

Background estimation?

Data-MC comparison

Opening angle

between

Data-MC comparison

Invariant Mass

M(MeV) M(MeV)

M(MeV)

Data-MC

PP(MeV) P(MeV)

P(MeV)

Data-MC

Summary on Systematics

After smearing systematics for angular cuts remains practically unchanged.

We look at cosand cos(OpAn) for cluster also in the transverse variable

Summary on Systematics

Full cos

Only transverse angle

xy plane

Summary on SystematicsCos(Full OpAn ) Only transverse angle

The situation is much better, systematic reduced from 1-2% to 1-2 per mil, the price we pay is the

background contamination:

OPAN–Cos–ANGLE–TOF–onlybarrel: Cut Eff = 25.67%

Signal events = 564765, PHI Bkg = 6.7% ETA Bkg = 30%

OPAN–Cos–ANGLE–TOF–onlybarrel–EtPt: Cut Eff = 24.89%

Signal events = 547759, PHI Bkg = 3% ETA Bkg = 0.2%

TransOPAN–CosTrans–ANGLE–TOF–onlybarrel: Cut Eff = 24.26%

Signal events = 533938, PHI Bkg = 25% ETA Bkg = 120%

TransOPAN–CosTrans–ANGLE–TOF–onlybarrel–EtPt: Cut Eff = 22.98%

Signal events = 505692, PHI Bkg = 11% ETA Bkg = 1%

NEW CUTS:

OLD CUTS:

New SystematicsTransverse cos

OK

New Systematics

Cos(Transv. OpAn )

OK

New Systematics

Et-Pt

The systematic on Et-Pt doesn't change.

New Systematics

E-P

Spectra after smearing

Spectra before smearing

Unbiased sample: only preselection

Outline (II)

New data sample to “play with” 560 pb-1 preselected with basic conditions: to study

smearing effect we introduce less kinematic constraints, and ask only ≥2 Prompt Neutral Cluster, one with E≥250MeV

This sample was used for the recent study of systematics and new smearing

What’s new:Different approach for the momenta:we take into account

curv from DTFS cov matrix

Better fitting

We use the smearing function:

tSmearett

Scalett

PfPGausP

fPP

,

1

Full fit with 3 params:

1) Total Scale: 0.88082) shift: 337.8 • 10-6

3) smearing: 0.1470

Smearing: Old method versus New

OLD: simple method each parameterFitted separately

NEW: Full fit with 3 parameters:Total Scale, shift, smearing

E – P cut problemEven with new smearing we do not get satisfactory

comparison with MC

eeg continuum

Unbiased sample: only preselection

Now is clear the problem is on the background estimation

We try to fit the Et-Pt (E–P) spectrum to see if the discrepancy is due to a bad

Signal/Background estimation Data – MC.

E-P: with all MC contributionssatisfying agreement

Output from TFractionFitter (1200bins in the histograms)

2 = 1728 Ndf = 1196

eeg continuum

Process Exp. Int.=602260

Parameter from fit

Original integral

Integral from fit

0.431598 193340 259934

0.3767 245648 226872

eeg 0.0013846 1520 8333.89

0.190317 104500 114620

After smearing and fit…

• Data-MC satisfying agreement

• Branching ratio stability and Systematic seems to be under control, we are reevaluating the systematics.

Other checks:

• kinematic fit

• Prompt Charged Vertex from EVCL

Kinematic fit 21 Input Parameters:

2 PNC: 2 5 = 10 parameters

2 tracks at PCA: 2 3 = 6 parameters

IP position: 3 parameters

Beam info: 2 parameters

7 Constraints:

Time of flight of photons: 2

4-momentum conservation: 4

invariant mass

RAD Stream

DATA-MC comparison 2 distribution

Analysys cut:•RAD•OPAN•Cos•ANGLE•TOF•Onlybarrel•EtPt

RPI Stream

DATA-MC comparison 2 distribution Analysys cut:•RAD•OPAN•Cos•ANGLE•TOF•Onlybarrel•EtPt

RAD StreamP+

P-

True-Rec True-Fit

(Ptrue-Prec)

(Ptrue-Prec)

(Ptrue-Pfit)

(Ptrue-Pfit)

RAD

RPI StreamTrue-Rec True-Fit

P+

P-

(Ptrue-Prec)

(Ptrue-Prec)

(Ptrue-Pfit)

(Ptrue-Pfit)

RPI

PCV Check: EVCL requirement on VTX

MC sgn Efficiency MC BKG Efficiency EXP EfficiencyALL 85619 269870 355371FITOK 77226 90.20% 171795 63.66% 355371 100.00%PCV 76910 99.59% 148768 86.60% 336859 94.79%Match 2 65300 84.90% 123165 82.79% 276182 81.99%Match 1 1254 1.63% 11438 7.69% 26104 7.75%Match 0 430 0.56% 993 0.67% 1406 0.42%

MC sgn Efficiency MC BKG Efficiency EXP EfficiencyALL 13080 1171479 985282FITOK 12179 93.11% 1171270 99.98% 985282 100.00%PCV 12179 100.00% 1171270 100.00% 985282 100.00%Match 2 11009 90.39% 1099563 93.88% 912749 92.64%Match 1 140 1.15% 9883 0.84% 11686 1.19%Match 0 50 0.41% 2195 0.19% 1835 0.19%

RAD

RPI

•PCV means there is the VTX as from EVCL requirement•Match means the tracks we choose are the one connected to PCV

Conclusions

• DATA-MC: the agreement is satisfying; systematics and BR seems to be under control: we are recomputing

• For us everithing is ok and we are ready to produce final number and documentation, if we are below 1%: TOF systematic still to be studied.

• Kinematic fit does not improve resolution and background reduction, moreover the 2 distribution shows disagrement at 2-5% level (well beyond our target)

• We can apply PCV requirement, in RAD stream, we do not use extra VTX info; use Roberto and Antonio work on tracks/vtx

Spare

Fitting with fraction fitter seems better (but fit probability still low)

E