1. h, h’ studies with the KLOE detector at DaFne
A. Farilla – I.N.F.N. Rome III
for the KLOE Collaboration
Ada Farilla
Uppsala, October 2001

2. * * The DAFNE complex Design philosophy:
DEAR
DAFNE is an Electron - Positron Collider
at s = 1.02 GeV F resonance
( F – Factory )
Design philosophy:
Moderate Single
Bunch Luminosity *
Large Number
of Bunches
4·1030(VEPP-2M) *
120 Bunches
Design Luminosity  5 ·1032
Two interaction points for detectors:
KLOE (CP(T) violation and K Physics)
DEAR / FINUDA (Kaon-Nucleon
Interaction and Hypernuclear Physics)
Ada Farilla
Uppsala, October 2001

3. Beam trajectory length ~ 98 m Beam crossing frequency 368.25 MHz
Beam-beam scattering
@ 5A/beam requires
two independent lines
Beam trajectory length
~ 98 m
Beam crossing frequency
MHz
Nbunch/ring = 120 (max)
Bunch spacing : 2.7 ns
Bunch I.P.:
length = 30 mm (sz)
transv.(x) = 2 mm (sx)
transv.(y) = 20 mm (sy)
Ada Farilla
Uppsala, October 2001

4. The KLOE physics program
e/e to O(10-4) via double ratio
Semileptonic asymmetry (CPT test)
Interferometry
2 pb-1
20 pb-1
200 pb-1
2 fb-1
Close out KS and f physics
KS  3p0, other rare KS decays
KL  2p, KL gg, form factors
s(e+e-  hadrons) to 1% (stat)
1999
2000
Today
End 2001
KS physics
BR(KS  p+p-)/BR(KS p0p0)
BR(KS pen)
f radiative decays
f  f0g, a0g
f  hg, hg
Ada Farilla
Uppsala, October 2001

5. DAFNE performance L dt2001 = 108 pb-1 So far in 2001…
KLOE integrated luminosity
4 Oct
So far in 2001…
L dt2001 = 108 pb-1
Peak luminosity exceeded 3.5 1031 cm-2s-1 (average > 2 1031 )
Integrated luminosity exceeded 2.0 pb-1/day (average > 0.8)
Expected total integrated luminosity in 2001: 200 pb-1 -> ~650 Millions F’s
corresponding to ~ 7.4 Millions h produced ( BR f->hg = ( )% )
Ada Farilla
Uppsala, October 2001

6. The KLOE Detector Superconducting Coil B=0.6 T Be beam pipe
(0.5 mm thickness)
permanent +
Quad’s instrumentation
Iron Yoke
Cylindrical Drift Chamber
4 m Diameter, 3.3 m Length
90% Helium, 10% Isobutane
12582 / 52140
sense / total wires
all stereo wires
Electromagnetic Calorimeter
Pb / Scintillating Fibres
(4880 PMTs)
Endcap - Barrel - Modules
Ada Farilla
Uppsala, October 2001

7. The Electromagnetic Calorimeter
Pb - Sc.Fibres - Matrix
Efficient Detection of Photons > 20 MeV
 Barrel + Endcap = 98% Hermetic Coverage
 Discriminate KL  p0p0 against KL  p0p0 p0
Reconstruct KL  p0 p0 decay vertex with a
precision < 1 cm
 Serve as a 1st level Trigger
<r> = 5 g/cm3
<l0> = 1.6 cm
sampl. frac.~15% (m.i.p.)
Lead
1.2 mm
1.0 mm
1.35 mm
Design:
sE /E = 5% /E(GeV)
s t = 70 ps /E (GeV)
Measured :
sE /E = 5.7% /E(GeV)
s t= 54 ps /E (GeV)  50 ps
450 cm
15X0
52.5 cm
Ada Farilla
Uppsala, October 2001

8. EmC: time and energy performances)
GeV ( ps 54 E =
s(t)
 50 ps
Time resolution
Energy residuals
e+e-e+e-g Eg from DC
Energy resolution
e+e-g
effects due to the beam (spread and bunch to bunch fluctuation) and to EMC cell to cell variation have been subctracted from the constant term
Ada Farilla
Uppsala, October 2001

9. EmC resolution on full neutral channels
f  p0g  ggg, f  hg  ggg
p0  gg h  gg
mp0 = MeV
sm = MeV
mh = MeV
sm = MeV
Ada Farilla
Uppsala, October 2001

10. permanent magnet quadrupoles
Quadrupole Calorimeter (QCAL)
45 cm
0.5 mm Al-Be 9°
permanent magnet quadrupoles
10 cm
Acceptance increased thanks
to Quadrupole Instrumentation :
Lead-Scintillator-Tile
Sampling Calorimeter
QCal
Spherical
Beam Pipe
QCAL
Ada Farilla
Uppsala, October 2001

11. The Drift Chamber ~52000 stereo wires
 High and uniform track reconstruction efficiency
 Determine the KL,S vertex with an accuracy of ~ 1mm
 Good momentum resolution
(dp/p  0.3% ) for Kl3 rej.
 Transparent to low energy g (down to 20 MeV) and KL,S regeneration ->
~52000 stereo wires
cell structure:
3:1 field:sense ratio
3 × 3 cm2 in the 46 outer layers
2 × 2 cm2 in the 12 inner layers
[90% He, 10% iC4H10 ( X0=900m )
mec. str. in C-Fibre (<0.1 X0)]
Ada Farilla
Uppsala, October 2001

12. DC resolution and stability
sp/p < 0.3%
45°<<135°
Residuals
Resolution
Well below 200 mm spatial resolution
in most of the impact parameter range
Drift distance (cm)
e+e-e+e-
sp (MeV/c)
Polar angle
mpp = MeV/c2
sm = 1 MeV/c2
KS  p+p-
Polar angle
Ada Farilla
Uppsala, October 2001

13. Pseudoscalars: f   g ,  g
With the decay   ’ we can probe the gluonic content of the ’:
theoretical predictions for BR(  ’) range from 2x10-4 down to ~10-6 in
case of significant gluonic content.
[N.Deshapande and G. Eilam., Phys. Rev. D25 (1980) 270, J. L. Rosner, Phys. Rev. D27 (1983) 1101,
F.E.Close, The DAFNE Physics Handbook Vol. II, Frascati 1992]
The mass eigenstates (547), ’(958) can be related to the SU(3) octet-singlet
states 8, 0 through the mixing angle p , whose value has
been discussed many times in the last 30 years: both from theoretical
predictions and from phenomenological analyses it varies from -23° to -10°.
[A. Bramon et al., Eur. J. C7 (1999) , A. Bramon et al., Phys. Lett. B503 (2001 ) 571 ]
[ F.J. Gilman, R. Kauffman, Phys. Rev. D 36 (1987) 2761]
Recent developments in ChPTand phenomenological analyses suggest the need to
use two mixing parameters 8 and0 in the octet-singlet basis.
[H. Leutwyler, Nucl. Phys. Proc. Suppl. 64 (1998) 223, R. Kaiser and H. Leutwyler, hep-ph/ ,
P. Ball, J. M. Frere and M. Tytgat, Phys. Lett. B365 (1996) 367]
P 8 and0 are related to the mixing angle FP that can be extracted from the
ratio of the amplitudes of   ’ and   
[T. Feldmann,P. Kroll and B. Stech, Phys.Lett.B449 (1999) 339, T. Feldmann Int. J. Mod. Phys. A15(2000)]
Ada Farilla
Uppsala, October 2001

14. f   g ,  g f   g  p+ p- p0 g  p+ p- 3 g BR 3 · 10 - 3
f   g  p+ p-  g  p+ p- 3 g BR  2 ·
The main background comes from:f  KS KL , f  p + p- p0
Event selection:
3 g from the IP ( T – R/c  5•st )
1 charged vertex in cylindrical region
around IP ( r  4 cm ; z 8 cm )
Ep+ + Ep_  430 MeV
for f -> h g
Ep+ + Ep_  550 MeV
for f -> h g
Kinematic fit
From MC simulation
Ep+ + Ep_ (MeV)
f->p pp0
f -> h g
f -> h g
Ada Farilla
Uppsala, October 2001

15. f   g ,  g f -> h g f -> h g p0 h h h Invariant mass
before and after
kinematic fit p0 h h h
Ada Farilla
Uppsala, October 2001

16. f   g ,  g -> h g control sample: Monte Carlo-Data comparison
Radiative g energy p momentum
-> h g control sample:
Monte Carlo-Data
comparison
Charged vertex r p + p- opening angle
Ada Farilla
Uppsala, October 2001

17. E1 vs E2 (after kin. fit) (MeV)
f   g ,  g
The photon energy spectrum of    and
  ’ events allows a very clear identification
of the photons in the two cases.
This can be used to exploit correlations between
the energies of two hardest photons in the
  ’ events. MC
MC ’
MC 
MeV
  ’ events are inside the ellipse
   events are in the two bands at ~363 MeV
E1 vs E2 (after kin. fit) (MeV)
Ada Farilla
Uppsala, October 2001

18. f   g ,  g
In a data sample of 16.6pb-1, after background subtraction we find:
N’ = 124  12stat  5syst , N = (502.1  2.2stat )x102
(Final efficiency : e ’ = 23% , e  = 37.6% )
For the ratio of the two BRs we find:
R = ( Nh eh / Nh eh )•RBR= (5.3 ± 0.5(stat) ± 0.4(sys))•10-3
Using the PDG2000 value for BR(f ->h g) we get:
BR(f ->h g) = (6.8 ± 0.6(stat) ± 0.5(sys))•10-5
hep-ex , Kloe collaboration
Contributed paper to Lepton Photon 2001
Ada Farilla
Uppsala, October 2001

19. f   g Invariant mass of p+ p- g g Recent measuremets of f   g
Ada Farilla
Uppsala, October 2001

20. f   g
From the ratio R we have extracted the mixing angle FP both in the approach suggested by Bramon et al.
(Eur. Phys. J. C7 (99)) [ using ms/m= ]
and in the approach suggested by Feldmann (Int. J. Mod. Phys. A15 (2000))
[using fs=1.34 fp, fq=1.07 fp].
We find the same result with the two
methods:
FP=( )o
hep-ex , Kloe collaboration
Contributed paper to Lepton Photon 2001
+1.7
- 1.5
Ada Farilla
Uppsala, October 2001

21.  h p0 p0  h p p  p0 p p f  h g f  h g  p0 p0 p0
f   g  p+ p- 7 g
We measure BR(f ->h‘g) also in the channels:
f  h g
 h p0 p0
 p0 p p
f  h g
 h p p
 p0 p0 p0
No attempt to distinguish the two channels
Main background comes from:
f -> KS KL ( + “spurious” e.m. clusters)
Ada Farilla
Uppsala, October 2001

22. 7 g from the IP ( T – R/c  5•st )
f   g  p+ p- 7 g
7 g from the IP ( T – R/c  5•st )
1 charged vertex in cylindrical region around IP
( r  4 cm ; z 8 cm )
KSKL rejection:
veto on KS  p+ p-
Ep+ + Ep_ < 440 MeV
cut on <cosqp+ p-< 0.84
Ep+ + Ep_
before K-rej.
MeV
Ep+ + Ep_
afterK-rej.
MeV
Ada Farilla
Uppsala, October 2001

23. Nh = 150  12(stat.) f   g  p+ p- 7 g Ep+ + Ep_
events after background subtraction
1 s agreement with the value of
BR(f   gg ) found in the final state p+ p- 3 g
Ep+ + Ep_
MeV
Ada Farilla
Uppsala, October 2001

24. f   g  g g g , f  p0 g  g g g Event selection:
3 g from the IP ( T – R/c  5•st ) 21o < cosqg < 159o
Etot > 800MeV
Kinematic fit with 4-momentum conservation
Photon assignment: minimization of c2 (p0 g) c2 (h g)
Final efficiency : e = 63%
Main background comes from e+e- -> gg(g)
Ada Farilla
Uppsala, October 2001

25. gg invariant mass (MeV)
Signal selection
gg invariant
mass distribution
p0g
gg invariant mass (MeV)
cosqgg and DEgg define
the two signal bands
vs QED background
cosqgg hg
DEgg MeV
Ada Farilla
Uppsala, October 2001

26. mass distribution after background subtraction
f   g  g g g , f  p0 g  g g g
gg invariant
mass distribution after background subtraction p0 h
G(f  h g  g g g)
G(f  p0g  g g g)
= (3.75 ± 0.02 ± 0.09) KLOE 2000 * (16.6 pb-1)
Preliminary
KLOE* : BR(f  p0g) = (1.377 ± 0.007± 0.05) • 10-3
PDG’00 : BR(f  p0g) = (1.26 ± 0.10) • 10-3
* Kloe internal note 234
Ada Farilla
Uppsala, October 2001

27. Work in progress
1) BR(h  p0p0p0 )/BR(h  gg) ) BR(h  p0p0p0 )/BR(h  p+p-p0) 3) Fit the Dalitz plot of h  p+p-p0 4) Limit on BR(h  g g g) (C-violating decay) 5) BR(h  p0 g g)
6) Study of h  p+p-g
7) Study of h’  p+p-g
Ada Farilla
Uppsala, October 2001

28. DAFNE is increasing the Luminosity delivered
Conclusions
The KLOE detector performs as expected
DAFNE is increasing the Luminosity delivered
With only ~12% of the collected statistics we have already the most precise measurement of BR(f ->h g) and of the pseudoscalar mixing angle fP
Many other interesting h decays are under study
Ada Farilla
Uppsala, October 2001