Measurement of h® p0gg BR at KLOE.

blessing material

Biagio Di Micco

Università degli Studi di Roma Tre

h production and Br(h® p0 gg) measurements in past experiments

p- + p ® h + n

(CERN, Brookhaven, GAMS, Crystal Ball)

p+ + d ® p + p + h (67)

p+ + p ® p+ + p +h (67,69)

K- + p ® L + h (70 AGS)

p+ + n ® h + p (71)

p- + n ® p- + n + h (80)

f ®hg (SND 01)

Most recent measurements

AGS/Crystal Ball

Phys. Lett. B 589 (2004) 14

GAMS2000

Z. Phys. C25, 225 (1984)

SND – Novosibirsk

Nucl. Phys. B600 (2001) 3

p- + p ® h + n

Nh = 3´107

f ® h g

Nh = 2.6´105

p- + p ® h + n

Nh = 6´105

Br(h®p0 gg)

(7.2  1.4)10-4

< 8.4 10-4

(2.7  0.9stat  0.5syst)10-4

L2 contributions

at tree level:





0

8

= 0 (Q = 0)

Proportional to the charges,

idem for L4 @ tree level.

p2

p4





+,K+

-,K-

0

8

1-loop contributions from L2 vertices, suppressed by G parity conservation and kaon mass suppression:

-loops = 0.8410-3 eV, k-loops = 2.4510-3 eV

-loops = 0.8410-3 eV, k-loops = 2.4510-3 eV

Br ~ 3.29x10-3 eV/1.18 keV = 2.8x10-6

Theoretical estimate

Estimates of P6 contributes

Extended Nambu Jona-Lasinio G6ENJL = 0.58 ± 0.3 eV

Nambu Jona-Lasinio	G6NJL = 0.11 eV

resonance saturation

L6 coefficient determined by the meson propagator

G6 VMD = 0.18 eV

Gall VMD+sc = 0.42 ± 0.20 eV

Chiral Unitary G Ch Unit = 0.47 ± 0.10 eV











SL





BR(%)

Decay

Lint ~ 450 pb-1

Nf ~ 1.5´109

Nh ~ 1.9´107

2004 collected luminosity

Lpeak = 11´1031

Laverage = 8.3´1031

Lint = 750 pb-1

KLOE collected luminosity

2001+2002 integrated luminosity

2005 estimated luminosity

(until July)

Lint > 750 pb-1

> 5g

f ® h(®3p0)g

2 lost

1 lost – 1 merged

2 merged

h® p0gg @KLOE

5g

final state

Background

< 5g + accidental

f ® h(®gg)g

f ® p0(®gg) g

e+ e-e+ e-(g), e+ e-gg

5g

f ® f0(®p0p0)g

f ® a0(®hp0) g

e+ e- ® w(®p0g)p0

f ®r0(®h g)p0,r0(® p0g)p0

f® hgf

p0

E(gf) = 363 MeV

p0gg

h

E(gf) = 363 MeV

f® hgf

gg

accidental clusters

Signal and accidental background topologies

< 5 g + accidental rejection

f ® h(®gg)g

f®p0(®gg) g

Inclusive g energy after kinematic fit

DATA

MC

Eg> 20 MeV

qg > 21°

p0

f® hgf

p0 p0 p0

7g

p0

p0

g1

g2

Cluster shape variables are used to identify merged clusters

Merged clusters background topology

Merged cluster
identification

—— good

—— merged

barrel

endcap

DATA-MC comparison

—— DATA

------ MC

good-merged discrimination

Background composition

Background composition obtained by fitting mgg

distribution

Correction factors

0.704  0.008

1.07  0.04

0.4  0.1

2.9  0.3

1.50  0.09

0.68  0.04

0.76  0.06

 900 bins

c2 = 1.2

mgg

mgg

Background composition checked on m3g plots

Correction factors obtained by the previous fit

Very nice reproduction of the w peak

w p0

p0g

Completely given by the 2 lost and 1 merged–1 lost normalization

mggg

mggg

5g rejection

f ® f0(®p0p0)g

f ® a0(®hp0) g

e+ e- ® w(®p0g)p0

f ®r0(®h g)p0,r0(® p0g)p0

Rejected vetoing the p0p0,h, w masses.

DATA-MC comparison of the S2 variables

Good DATA-MC agreement

m4g distribution for signal

and background

m4g distribution of the back-ground, obtained by the MC simulation.

m4g distribution of the signal, obtained by the MC simulation.

The signal content is evaluated by fitting the m4g distribution of the less energetic photons.

A binned likelihood approach is used, taking into account the finite size of MC statistic.

Preliminary fit result

The shape of background + signal after fit well reproduce the DATA.

Pbkg = 0.907  0.049

Psig = 0.093  0.031

NDATA = 735

Nbkg = 667  36 Nsig=6823

e(hp0gg) = 4.63  0.09 (only stat)

N(3p0) = 2288882

e(hp0p0p0) = 0.378  0.08syst 0.01stat

Statistical significance

68%

90%

95%

99%

Br dependence by the bin width for m4g

Bin width variation:

2 – 9 MeV

chosen bin width:

6 MeV

correction:

error:

-0.26  10-5

0.26  10-5

Br dependence by the lower cut on m4g

cut variation:

378 – 478 MeV

chosen cut:

426 MeV

correction:

error:

0.

0.44  10-5

Br dependence by the higher cut on m4g

cut variation:

570 – 720 MeV

chosen cut:

612 MeV

correction:

error:

0.

0.56  10-5

Br dependence by the likelihood cut and 2 merged abundance

Fitted factor

chosen cut

the likelihood isn't good.

the 2 merging correction factor is not good. I'll try with the new likelihood.

For strong cut the 2 merged case is heavily suppressed and it gives a reasonable systematic.

I would give as preliminary overestimated systematic the shown band.

correction:

error:

+0.62  10-5

1.1  10-5

Normalization check

e(hp0p0p0) = 0.378  0.08syst 0.01stat

From direct h ® 3p0 evaluation

N(3p0) = 2288882

From total integrated luminosity estimated run by run:

Lint = 422.5 pb-1

Nf = 1.39  109

Nh = 1.80  107

N(3p0)exp = 5.87  106

De/e ~ 3%

Forget about

Preliminary result

Preliminary systematic error

bin width

low energy cut

high energy cut

likelihood

Overall

0.26  10-5

0.44  10-5

0.56  10-5

1.1  10-5

1.3  10-5

correction

Fit result

bin width correction

likelihood correction

Result

8.0  10-5

-0.26  10-5

+0.62  10-5

8.4  10-5

Result

Br(h®p0gg) = (8.4  2.7  1.3)  10-5

Preliminary

Comparison with theoretical predictions

p6 calculation seems enough

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[1] J.N. Ng and D. J. Peters, Phys. Rev. D46 (1992) 5034

[2] J.N. Ng and D. J. Peters, Phys. Rev. D47 (1993) 4939

[3-4] L. Ametller, J. Bijnens, A. Bramon, F. Cornet, Phys. Lett. B276 (1992)

[5] S. Bellucci and C. Bruno, Nucl. Phys. B452 (1995) 626

[6] E. Oset, J. R. Pelaź and L. Roca, Phys. Rev. D67 (2003) 073013

[7] J. Bijnens, A. Fayyazuddin and J. Prades, Phys. Lett. B379 (1996) 209

[8] A. A. Belkov, A. V. Lanyov, S. Scherer, J. Phys. G 22 (1996) 1383

CB

GAMS

KLOE preliminary

Theoretical history

Merged clusters identification

Shower shape variables are used to identify merged clusters :

x,y,z,tmean =

rms

skewness

We find the distribution of this variables (xk) for good clusters and for merged ones, then we build the likelihood:

and we use the ratio

as a discriminating variable:

mean

The most energetic photon is, in the main part of cases, the recoil photon of the f®hg decay (363 MeV)

before kinematic fit

after kinematic fit

We build the invariant mass m4g of the 4 less energetic photons to search for the signal.

DATA – MC comparison

DATA

MC

the p0 peak is well reproduced

mp(MC) = 134.93 ± 0.04 MeV/c2

mp(DATA) = 135.08 ± 0.07 MeV/c2

DATA-MC comparison of energy distribution

Expected background

142

53

72

41

24

125

213

669

2004-10-27T18:14:05