Transcript Document

Results from KLOE
LNF Scientific Committee 23/05/2002
C.Bini
Universita’ “La Sapienza” and INFN Roma
(1) First published papers
(2) Analyses in progress
(3) 2001/2002 data physics perspectives
KLOE physics papers [4+1] (based on data taken in 2000: ~20 pb-1):
(1) Measurement of the branching fraction for the decay KS  p e n
Phys.Lett. B 535 37 (2002)
(2) Study of the decay f  hp0g with the KLOE detector
Phys.Lett. B 536 209 (2002)
(3) Study of the decay f  p0p0g with the KLOE detector
Phys.Lett.B 537 21 (2002)
(4) Measurement of G(KSp+p-(g))/G(KSp0p0)
hep-ex/0204024 , accepted by Phys.Lett.B
(5) Measurement of f  h’g / f  hg
KLOE Note 179 , to be submitted to Phys.Lett. B
KLOE detector papers:
(6) The KLOE electromagnetic calorimeter
Nucl.Instr. and Meth. A482 364 (2002)
(7) The QCAL tile calorimeter of KLOE
Nucl.Instr. and Meth. A483 649 (2002)
(8) The KLOE drift chamber
accepted by Nucl.Instr. and Meth. A
(9) The KLOE trigger system
submitted to Nucl.Instr. and Meth. A
 Results on KS physics [papers (1) and (4)]:
tagging of a pure KS beam (unique opportunity of a f-factory).
KL interaction in the calorimeter (ToF
signature)
 s measurement
 KS “tagging”
Analysis of 2000 data concentrated on:
semileptonic KS decay
G(KS p+p-(g)) / G(KS p0p0)
Measurement of KS decays
Other analyses in progress on larger statistics.
KS Semileptonic decays
Paper dedicated to the memory of L. Paoluzi
Motivation:
 If (CPT ok) .AND. (DS=DQ at work):
G(KS  p e n ) = G(KL  p e n )
BR(KS  p e n ) = BR(KL  p e n ) x (GL/GS)
= ( 6.704 ± 0.071 ) x 10-4
(using all PDG information).
Only one measurement 75 events (CMD-2 1999):
= ( 7.2 ± 1.4 ) x 10-4
MC: the signal
Selection uses:
2 tracks invariant mass
difference of ToF between e and p
ToF selection illustrated for MC events
Notice: sign of the charge is determined
 Semileptonic asymmetry accessible
MC: the background
After ToF cuts  assignment of electron and pion
 Emiss –Pmiss distribution  a clear signal peaked at 0
Result from 17 pb-1
BR(KS  p e n )
2000
BR(KS  p e n ) = (6.91 ± 0.34stat ± 0.15syst) x 10-4
G(KS p+p- (g)) / G(KS p0p0)
Motivations:
 First part of double ratio
Notice: experiments measure double ratio at 0.1% and the single ratio at 1%
KLOE aims to measure each single ratio (KL and KS) at 0.1%
 Extractions of Isospin Amplitudes and Phases A0 A2 and d0-d2  consistent treatment of
soft g in KS  p+p- (g) [Cirigliano, Donoghue, Golowich 2000]
Selection procedure:
1. KS tagging
2. KS  p+p-(g) two tracks from I.P +
acceptance cuts: fully inclusive
measurement: no request on g in calorimeter
eppg (Eg*) from MC  folded to
theoretical g spectrum
3.KS  p0p0
neutral prompt cluster
(Eg>20 MeV and (T-R/c) < 5st )
at least 3 neutral prompt clusters
(p0 e+e-g included)
Result (from 17 pb-1):
Nev (KS  p+p- ) = 1.098 x 106
Nev (KS  p0p0 ) = 0.788 x 106
R = 2.239 ± 0.003stat ± 0.015syst
 stat. uncertainty at 0.14% level
 contributions to “systematic”:
tagging eff. Ratio
0.55%
photon counting
0.20%
tracking
0.26%
Trigger
0.23%
-------------------------------------Total syst. uncertainty 0.68%
PDG 2001 average is
2.197 ± 0.026
( without clear indication of Eg*cut )
Notice: efficiencies by data control
samples (statistically limited)
Goal = reach 0.1% systematic uncertainty
[< 2 x 10-4 on Re(e’/e)].
Results on f radiative decays: [papers (2), (3) and (5)]
Rad. Decay
hg
p0g
h’g
ppg
hp0g
BR (PDG)
1.26%
1.3 x10-3
~10-4
~10-4
~10-4
f  P (0-+) g
f  S (0++) g
S  pp / hp
Analysis of 2000 data on:
f  h’g / hg
f  p0p0g
f  hp0g
[paper (5)]
[paper (2)]
[paper (3)]
f  Scalar Meson + g [f0(980) I=0, a0(980) I=1]
Motivations:
f0, a0, not easily interpreted as qq states; other interpretations suggested:
 qqqq states (lower mass) [Jaffe 1977];
 KK molecule (m(f0,a0)~2m(K)) [Weinstein, Isgur 1990];
f f0g , a0g BR, mass spectra sensitive to f0,a0 nature
[Achasov, Ivanchenko 1989]:
Kaon loop approach:
radiative g
f0,a0
f
Kaon loop
Overlap = structure dependent
function
k = f0 momentum
final state
g(fKK)
from G(fK+K-)
g(f0KK) g(a0KK)
f0, a0 model
g(f0pp) g(a0hp)
M(p0p0) M(hp) spectra
f  p0p0g
 5g
Result (from 17 pb-1):
Nev = 2438  61
BR(f  p0p0g )=(1.09  0.03stat  0.05syst)x10-4
CMD-2 (0.92 0.08 0.06)x10-4
SND
(1.14 0.10 0.12)x10-4
Fit to the Mpp spectrum (kaon loop):
contributions from
f  f0g
f  sg
+ “strong” negative interference
negligible contribution
f  r0p0 p0p0g
Fit results:
M(f0) = 973  1 MeV
g2(f0KK)/4p = 2.79  0.12 GeV2
g(f0pp) /g(f0KK) = 0.50  0.01
g(fsg) = 0.060  0.008
BR(f  f0g  p0p0g ) = (1.49  0.07)x10-4
f  hp0g
Measured in 2 final states:
(Sample 1) h  gg
(Sample 2) h  p+p-p0
(5g)
(2t + 5g)
Results (from 17 pb-1):
(Sample1) Nev = 916 Nbck = 309  20
BR(f  hp0g) = (8.5  0.5stat  0.6syst)x10-5
(Sample2) Nev = 197 Nbck = 4  4
BR(f  hp0g) = (8.0  0.6stat  0.5syst)x10-5
CMD-2 (9.0 2.4 1.0) x 10-5
SND
(8.8 1.4 0.9) x 10-5
Combined fit to the Mhp spectra:
dominated by f  a0g
negligible
f  r0p0 hp0g
Fit results:
M(a0) = 984.8 MeV (PDG)
g2(a0KK)/4p = 0.40  0.04 GeV2
g(a0hp) /g(a0KK) = 1.35  0.09
BR(f  a0g  hp0g) = (7.4  0.7)x10-5
Summary: KLOE Results on Scalars vs. models.
g2f0KK/(4p)
(GeV2)
g2a0KK/(4p)
(GeV2)
gf0pp /gf0KK
ga0hp/ga0KK
KLOE
2.790.12
0.400.04
0.500.01
1.350.09
(1) f 0  s s
qqqq
“super-allowed”
(~2 GeV2)
“super-allowed”
(~2 GeV2)
0.3—0.5
0.9
“OZI-forbidden” “OZI-forbidden”
a 0  (uu - dd)
;
(2) f 0  (uu + dd)
qq(1)
qq(2)
“OZI-allowed” “OZI-forbidden”
2
;
0.5
1.5
2
a 0  (uu - dd)
• f0 parameters compatible with 4q model
2
1.5
• a0 parameters not well described by the 4q model
(2001 data  more accurate study of a0)
2
f  Pseudoscalar + g
 hg
 h’g
According to quark model:
 assuming: no other contents (e.g. gluon))
p0 = (uu-dd)/2
h = cosaP (uu+dd)/2 + sinaPss
h’ = -sinaP (uu+dd)/2 + cosaPss
 assuming: f = ss state (aV=0) (F slowly varying function; model dependent)
G(f  h’g)
R=
G(f  h g)
Kh’
= cotg2aP (
)3 x F(aP, aV)
Kh
Decay chains used: (same topology 2T + 3 photons / final states different kinematics)
(a) f  hg  p+p-p0g  p+p- 3g
(b) f  h’g  h p+p-g  p+p- 3g
Results:
N(a) = 50210  220
N(b) = 120  12stat ±5bck
Invariant mass spectrum
of h’g
to get R, effect of non resonant e+e-rh(h)g :
 5% correction (opposite sign interference of
r with h and h’)
BR(f  h’g)
R=

BR(f  hg)
= (4.70  0.47stat  0.31syst) x 10-3
aP = ( 41.8  1.7)o [ qP = (-12.9  1.7)o ]
+1.5
Using the PDG value for BR(f  h g )  BR(f  h’g ) [PDG : (6.7
)  10-5 ]
-1.4
BR(f  h’g ) = (6.10  0.61stat  0.43syst) x 10-5
+ preliminary result using fhgp+p-7g; h hp+p-(hp0p0) hp0p0p0 (hp+p-p0)
BR (f  h’g ) = (7.0  0.6  1.0)  10-5 (not included in paper (5))
BR (f  h’g ) x 10-5
comparison of KLOE results on
BR (f  h’g )
with previous results (from VEPP-2M)
10
2000 data
8
6
4
2
CMD-2
0
BR (f  h’g ) helps in assessing the h’
gluon content: combined analysis.
h’ = X h’ (uu+dd)/2 + Y h’ ss + Z h’ gluonium
Assume Z h’ =0  evaluate X h’ from other channels
 evaluate Y h’ from f  h’g
Result
Xh2 + Yh2  0.95+-00..11
07
SND
KLOE
Analyses in progress (aim to publish by end of 2002):
 Published results x 10 statistics + improve systematic. In particular:
-BR(KS  p e n ) measurement down to 2% + first look at charge asymmetry
-G(KSp+p-(g))/G(KSp0p0) measurement down to 0.1% (work on systematic)
-high statistics a0 spectrum
 KL  gg / KL  3p0
(**)
 Hadronic cross-section s(e+e-  p+p-) vs s 2mp < s < mf
 Measurement of the K0 mass from f  KSKL, KS  p+p-
(**)
KLOE Note 181
 Dynamics of the f  p+p-p0 decay  r+ r- r0 parameters
 Upper limit on h  ggg (test of C invariance in EM decays) KLOE Note 180
(**)
G( KL  gg ) / G( KL  p0p0p0 )
Motivations:
 Long distance contribution to the rare KL  m+m- decay
 Predictions on KS  gg
 Test of Chiral Perturbation Theory
BR(KL  gg ) = (5.86 ±0.15) x 10-4 [NA31 BR(KL  gg ) /BR ( KL  p0p0)]
Drift Chamber volume
KLOE improvement to 1% measurement
Normalization to BR (KL  p0p0p0)
1.3% uncertainty (not 2.2%)
KL  p0p0p0 well measured in all the
fiducial volume:
Measurement of tKL
Event Selection:
 KL tagging (by KS  p+p-)
 Neutral Vertex from 2 g Eg > 100 MeV
8540 ± 120 events (after background subtraction) from 150 pb-1 analyzed
Efficiency checks in progress (data vs Montecarlo)
Distribution of M(gg):
data
(red)
MC signal (black)
MC bckg (blue)
Hadronic cross-section s(e+e-  p+p-) vs s 2mp < s < mf
Measured by Radiative Return
complementary approach to the standard energy scan
Key points: knowledge of ISR function
background (mostly FSR)
 EVA Montecarlo
Select p+p-g events.
Tracks from I.R. 40o < qTRACK < 140o + Part.ID using calorimeter.
1) large angle 55o < qpp < 125o
(blue) a g in the calorimeter required
2) small angle qpp < 15o or qpp > 165o (red) no g required
Sample 1) = higher background (FSR +
p+p-p0); all Mpp spectrum
ds
dM2pp
Sample 2) = higher s, less background
but kinematically limited
(acceptance loss)
pions
photon
M2pp
Comparison of data (22.6 pb-1) with Montecarlo (EVA + detector response):
[visible cross-section, no unfolding applied]
1) Large angle sample (45000 events) - 2) Small angle sample (265000 events)
• MC
• data
(DATA-MC)/MC (%)
qpp < 15o or qpp > 165o
ds(e+e-  p+p-g)/dM2pp(nb/GeV2)
ds(e+e-  p+p-g)/dM2pp(nb/GeV2)
55o < qpp< 125o
• MC
• data
(DATA-MC)/MC (%)
Outlook:
• KLOE 2001 data (175 pb-1) are enough to measure the hadronic crosssection s(e+e-  p+p-) with a statistical uncertainty of ~ 0.15% for small
angle sample and ~ 0.3% for large angle sample.
• The new NLO generator from Kühn et al. (PHOKARA,a,a2), improves
the theoretical description of ISR.
The uncertainty from unaccounted higher order ISR is estimated to be
around 0.5% (hep-ph/0112184)
• Expected improvement in the knowledge of the radiator function and in
the luminosity measurement.
Results are expected before the end of the year!
Measurement of the K0 mass from f  KSKL, KS  p+p-
s(e+e-  KSKL )(mb)
1.0
Method:
f  KSKL , KS  p+pM2K=W2/4 - P2K
W from e+e- invariant mass spectrum;
absolute calibration from f - scan
(normalizing to CMD-2 Mf value)
PK from KS  p+p-
Result:
single event kaon mass resolution
~ 430 keV
MK = 497.574 ± 0.005stat ± 0.020syst MeV
0.8
0.6
0.4
0.2
0.0
0.10
0.05
0.00
497.9
-0.05
-0.10
1015
497.7
497.5
1020
1025
1030
W (MeV)
CMD-2 NA48 KLOE
2001/2002 data physics perspectives:
KS decays: p+p-g with measurement of g spectrum
 gg
limits on  p0p0p0
KL decays:  p+p- / p0p0
 pl±n
h decays:
 sin qC
[6 x106 h in 2001 tag from f  hg Eg = 363 MeV photon]
 ggg
(improve C-test)
 p +p -g
(photon spectrum)
 p +p -p 0 p 0 p 0 p 0
(Dalitz plot slopes)
 p0gg
(branching ratio)
[significant checks of Chiral Perturbation Theory]
K decays: mutual tagging [6 x 105 tags / pb-1  large statistics] but:
sensitive to machine background
difficult analysis (requiring specific tools)
List of items:
 p0l±n
 sin qC (check with sin qC from KL)
 p p0 … all K  BR can be improved
 m n
 fK
 3p Dalitz plot parameters
radiative decays final state + g
Tagging: K+  m+ n tags K-  p- p0
momentum distribution
of the daughter particle
in the K rest frame:
m n peak
p p0 peak
Conclusion
First 4+1 papers using a ~20 pb-1 sample:
previous results are improved.
We have learned how to extract physics results from our data:
Machine parameters monitor and control (example)
Calibration
Efficiency from data
Corrections to Montecarlo
We warmly acknowledge the
DAFNE team for their efforts
in providing us good data.