Transcript Slide 1
QNP06 – Madrid – 09/06/06
Recent KLOE results on Hadron Physics
Cesare Bini
Universita’ “La Sapienza” and INFN Roma
Outline:
The KLOE experiment at DAFNE
Results on Scalar Mesons
Results on Pseudoscalar Mesons
Prospects for e+e- at Frascati
DAFNE: the Frascati f - factory
• e+e- collider with 2 separate
rings: s = Mf= 1019.4 MeV
• 2 interaction regions
1. KLOE
2. DEAR (kaonic atoms)
FINUDA (hypernuclei)
Luminosity was delivered
to the 3 experiments
KLOE
2700 pb-1
FINUDA
250 pb-1
DEAR
100 pb-1
Luminosity has increased
up to 1.5×1032 cm-2s-1
The KLOE experiment
The detector:
A large drift chamber;
A hermetic calorimeter
A solenoidal superconducting coil
Drift Chamber (He-IsoBut.
( p )
p
2m × 3m)
0.4%
E.M. Calorimeter (lead-scintillating fibres)
E
E
5.4%
55 ps
t
130 ps
E (GeV )
E (GeV )
Magnetic field (SuperConducting Coil)
= 0.52 T (solenoid)
STATUS:
March 2006: end of KLOE data taking
2500 pb-1 on-peak 8 × 109 f decays
200 pb-1 off-peak (energy scan + 1 GeV run)
Physics at a f – factory:
a window on the lowest mass mesons
Sketch of the f decays:
0-+
1--
'
Branching
fraction
K+K-
49.2 %
KS KL
34.0 %
a0(980)
r + +-
15.3 %
f0(980)
g
1.301 %
g
0.125 %
’g
6.2 × 10-5
g
1.1 × 10-4
g
8.3 × 10-5
0++
f(1020)
KK
Main decay
channels
r(770)
Direct decay
Radiative decay
-emission
+ “radiative return” to +-
#events = Br.F. × 8 × 109 ~105 ’, ,
Overview of KLOE physics
(1) Kaon physics: several “fundamental physics” items:
Extraction of the Vus element of the CKM matrix from
5 semi-leptonic decays of neutral and charged kaons
test of CKM Unitarity
CPT tests: first measurement of KS semi-leptonic asimmetry
Kaon interferometry in +-+- final states:
bounds on quantum decoherence + CPT violation
Reduced upper bound on KS CP violating decay
Precision measurement of KS +- / KS
Measurement of KL and KS gg ChPT test
~ 450 pb-1 analysed
= 20 × previous analyses
(2) Hadron physics:
Scalar Mesons ( a0(980), f0(980) (500) )
Pseudoscalar Mesons ( 0, , ’ )
Vector Mesons ( properties of r(770), w(780) )
(3) Measurement of the Hadronic Cross-Section below 1 GeV
hadronic corrections to g-2
Scalar Mesons
How a f-factory can contribute to the understanding of
the scalar mesons
Mass (GeV/c2)
f(1020)
1.
a0(980)
f0(980)
k(800)
(500)
0.
I=0
I=1/2
I=1
Scalar Mesons Spectroscopy:
f0(980), (500) and a0(980)
are accessible (k not accessible)
through f Sg;
Questions:
1. Is (500) needed to describe
the mass spectra ?
2. “couplings”of f0(980) and
a0(980) to f |ss> and to KK,
and .
4-quark vs. 2-quark vs. KK molecule
Scalar Mesons with KLOE
f f0(980)g
f a0(980)g
f (500)g
+-g
g
K+K-g[ 2m(K)~m(f0)~m(f) ] expected BR
K0K0g
“
“
g
K+K-g
expected BR
K0K0g
“
+-g
g
~ 10-6
~ 10-8
~ 10-6
~ 10-8
General Comments:
fits of mass spectra are needed to extract the signals: this
requires a parametrization for the signal shape;
the unreducible background is not fully known: a
parametrization is required and some parameters have to be
determined from the data themselves;
sizeable interferences between signal and background;
The +-g analysis
P.L.B 634 ,148 (2006)
Event selection:
2 tracks with qt>45o; missing momentum q>45o (large angle)
Each track is pion-like (tracking, ToF and Shower shape)
1 photon matching the missing momentum
6.7 ×105 events / 350 pb-1
Particle identification: vs. e and m
(Likelihood: Tof and Shower shape)
pions, muons
(“trackmass”)
pions
muons
electrons
The +-gfinal state is dominated by:
Initial State Radiation
Final State Radiation
The f0(980) is observed as a “bump” in:
d/dm() vs. m()
Ac vs. m() -- Forward-Backward asymmetry
f0(980) signal
Ac
Events
m() (MeV)
data
MC no f0
MC with f0
Fit of the mass spectrum using 2 different models for the scalar amplitude:
Kaon-Loop model
[N.N.Achasov et al. ] mf0, gf0+-, gf0K+K-,
“No Structure” model
[G.Isidori et al. ] mf0, gf0+-, gf0K+K-, gff0g, b0,b1
Free parameters: scalar amplitude + background
An acceptable fit
is obtained with
both models:
P(c2)(KL)=4.2%
P(c2)(NS)=4.4%
Mass values ok
gf0K+K-> gf0+ “Large” coupling to the f
B.R.(f f0(980)g +-g) = 2.1 2.4 × 10-4 (from integral of |Amplitude|2)
The g analysis
Event selection:
5 photons with qg>21o ; no tracks;
Kinematic fit energy-momentum conservation;
Kinematic fit 0 masses: choice of the pairing.
4 ×105 events / 450 pb-1 analysis of Dalitz-plot
2 components in the Dalitz-plot
Fit of the Dalitz-plot (without rejecting w0) using the same 2 models:
Improved Kaon-Loop model (introducing the f(500g
“No Structure” model
Parameters: mass and couplings ( mf0, gf0+-, gf0K+K-, gff0g) + background
The (500) parameters are fixed. The fit is repeated by changing them
2-dim fit shown
slice bt slice.
A good fit
is obtained with
both models:
P(c2)(KL)=14%
P(c2)(NS)= 4%
Fit results
f0(980) param.
NS model
KL model
mf0
(MeV)
981 ÷ 987
976 ÷ 987
gffg
(GeV-1)
2.5 ÷ 2.7
-
gf+- (GeV)
1.3 ÷ 1.4
1.4 ÷ 2.0
gfKK
0.1 ÷ 1.0
3.3 ÷ 5.0
0. ÷ 0.9
3.0 ÷ 7.3
(GeV)
R=g2fKK /g2f+-
Comments:
(500) is needed in KL fit [p(c2) ~ 10-4 14% !]
(best parameters are: M=462 MeV, G=300 MeV);
f0(980) parameters agree with +-g analysis KL fit
again R > 1 (gf0KK > gf0+-);
NS fit gives large gff0g but R<1 (??);
BR extracted: integral of |scalar amplitude|2
+0.04
+0.06
-4
BR(f Sg 0 0g ) 1.07+-00..01
(fit)
(syst)
(mod)
10
04
-0.02
-0.05
BR( g) ~ 1/2 × BR(+-g): neglecting KK, we add the 2 BRs
BR(f f0(980)g) = (3.1 ÷ 3.5) × 10-4
G(f f0(980)g) = 1.2 ÷ 1.6 keV
The g analysis
Simultaneous analysis of gg and +- channels:
Pts. = data 450 pb-1 = 20 × published results, hist = KL fit
The spectra are dominated by the a0 production
(negligible unreducible backgrounds).
Work in progress, results soon
Scalar Mesons: Summary and Outlook
1) Complete analysis of f f0(980)g with f0(980) +- and
good description of the scalar amplitude with KL model:
large couplings to Kaons: hint of a large s-quark content
(500) is still required to describe the Dalitz-plot
NS fit suggests large coupling of f0(980) to the f
2) Work in progress to:
make a combined analysis of f0(980) +- and
complete the analysis of f a0(980)g with a0(980)
study the decay chain f [f0(980)+a0(980)]g KKg
(expected sensitivity down to 10-8)
3) Further studies:
search for e+e- e+e-events (gg ) using the
run @ s = 1 GeV (off-peak = less background);
search for the (500) [F.Nguyen et al. 2005]
Pseudoscalar Mesons
Large samples of 0, and ’ through the radiative decay f Pg
8 ×107
9 ×106 0
4 ×105 ’
List of the analyses done or in progress
Measurement of the (and 0) masses
Measurement of the – ’ mixing angle in +- 3g
Measurement of the – ’ mixing angle in +- 7g
this talk
Phys.Lett.B541 (2002) 45
this talk
Dynamic of the decay +-
AIP:Conf.Proc.814:463,2006
Dynamic of the decay
AIP:Conf.Proc.814:463,2006
Measurement of the BR( gg)
AIP:Conf.Proc.814:463,2006
Upper limit on the C-violating decay ggg
Phys.Lett.B591 (2004) 49
Upper limit on the P(CP)-violating decay +-
Phys.Lett.B606 (2005) 276
Study of the decay +-e+e-
in progress
Upper limit on the P(CP)-violating decay
in progress
Measurement of the (and 0) masses
2 recent measurements done with different techniques:
GEM (COSY) p+d 3He+
M()=(547311 ± 28 ± 32) keV/c2
(missing mass technique)
NA48 (CERN) -+p n+
M()=(547843 ± 30 ± 41) keV/c2
( 30 reconstruction)
8 discrepancy: dM()=(532 ± 41 ± 52) keV/c2 (errors added in quadrature)
KLOE: fg; gg check with f0g; 0gg
Technique: kinematic fit mostly based on photon positions and timing;
f energy-momentum and vertex position from large angle Bhabha scattering
3g Dalitz-plot
The and the peak are well defined
Mass (MeV)
Results (still preliminary):
The statistical uncertainty is ~negligible
Systematic uncertainties from knowledge of s and vertex position
(work in progress to reduce it)
The mass is well in agreement with PDG value
M(0)
= ( 134990 6stat 30syst ) keV
M(0)PDG = ( 134976.6 0.6 ) keV
The mass is in agreement with NA48 and in disagreement with GEM
M() = ( 547822 5stat 69syst ) keV
KLOE
NA48
GEM (see Kirillov @ QNP06)
mass (MeV)
Measurement of the – ’ mixing angle in +- 7g
g N g BR 3 0
BR
f
similar and ’ decay
Method: measurement of R
using
K r chains
g
BRf g N BRcrg crg + BRntr ntr
g
Previous analysis:
’ +- gg
+- gg
+-3g
+-3g
This analysis:
’ +-
’ +-
gg
+-7g
+-7g
7g
427 pb-1 2001/2002 data
N(g) = 1665000 1300
(no bck)
signal (no bck)
’ signal (~10% bck)
N(+-7g’s) = 375060
(Nbckg= 345)
N(´g) = 3405 ± 61stat ± 28syst
R (4.79 0.09 stat 0.20 sys ) 10 -3
BR f g 6.24 0.12 0.28 10 -5
The systematic uncertainty is due to the uncertainty on the intermediate BRs
(1) Pseudoscalar mixing angle: extracted using the parametrisation
[A.Bramon et al. 1999]
m s Z NS tanV
BRf g
2
R
cot P
1
BRf g
m
Z
si n2 P
S
Mixing angle
(2) Analysis of ’ gluonic content:
[E.Kuo, 2001]
Before KLOE results
p
p
2
3
P 41.4 0.3stat 0.7sys 0.6th
1
| uu + dd +Y | ss + Z | glue
2
2
X 2 + YIncluding
+ Z 2 1new KLOE result
X
X2+Y2 = 0.93 ± 0.06
Prospects for e+e- physics at Frascati
Short term program:
New FINUDA Run
2006 – 2007
previous statistics × 5
SIDDHARTA Run
2007 – 2008
upgraded version of DEAR
(see C.Curceanu talk @ QNP06)
???
> 2009
Discussions are open in the laboratory about a possible
continuation of a low-energy e+e- program
Present project == DANAE (not approved yet):
higher luminosity f – factory
(L~1033 cm-2s-1)
energy scan: √s = 1 ÷ 2.5 GeV (L~1032 cm-2s-1)
3 Expressions of Interest have been presented:
KLOE2
Kaon physics + / ’ physics @ f
ggphysics + hadronic cross-section up to 2.5 GeV
AMADEUS
deeply bound hypernuclei @ f
DANTE
baryon time-like form factors (√s > 1.9 GeV)
Waiting for the final decision of the laboratory.
Any contribution is welcome !
http://www.lnf.infn.it/lnfadmin/roadmap/roadmap.html
Spare Slides
Scalar Mesons
Renewed interest after B-factory results:
new scalar meson “zoology” above 2.3 GeV
reconsider the low mass spectrum
A 0++ meson arises from a qq pair in a
triplet spin state (S=1) and P-wave (L=1)
Assuming 2 quarks interacting by a single gluon
exchange, other configurations are found [Jaffe 1977]:
Color triplet diquarks and anti-diquarks
Attractive interaction between diquark and anti-diquark
giving a color singlet
it is possible to build up 4-quarks scalar meson
Analysis of the mass spectra of the lowest mass mesons
Pseudoscalar multi-plet
Vector multi-plet
Scalar multi-plet:
(500), k(700), f0(980), a0(980)
Provided and k are there
the scalars have an
“Inverted Spectrum”
Inverted Mass spectrum hint of a 4q picture
Building Rule:
Mass
usu s sd sd ussd sd u s
add 2
Quarks s
Q=0
Q=0
Q=1
Q=-1 (the f0(980)
and a0(980))
udu s udsd usu d sd u d
add 1
Quark s
Q=0
Q=1
Q=0
udu d
Q=-1 (the k(800))
I3=0 Q=0 (the (500))
2 important consequences: if 4q hypothesis is correct
the (500) and the k(800) have to be firmly established
the s-quark content of f0 and a0 should be sizeable
( f0 and a0 couplings with f (ss) and with kaons
[N.N.Achasov and V.Ivanchenko 1989]
Definition of the relevant couplings (S=f0 or a0):
S to f
S to kaons
f0 to (I=0)
a0 to (I=1)
Coupling ratio
gfSg
gSKK=gSK+K-=gSK0K0
gf0=√3/2 gf0+-=√3 gf0
ga0
Rf0=(gf0K+K-/ gf0+-)2
Ra0=(ga0K+K-/ ga0)2
+
g
Kaon-loop
+
K+
f
f0,a0
K-
(GeV-1)
(GeV)
(GeV)
(GeV)
-
No-structure
f
-
f0,a0
g