kloe results on hadron physics
DESCRIPTION
Hadron07, Frascati 09/10/2007. KLOE results on hadron physics. Cesare Bini Università “La Sapienza” and INFN Roma on behalf of the KLOE collaboration. Outline: The KLOE experiment Results on pseudoscalar mesons Results on scalar mesons Prospects. 1. The KLOE experiment at DA NE. - PowerPoint PPT PresentationTRANSCRIPT
KLOE results on hadron physicsCesare Bini
Università “La Sapienza” and INFN Romaon behalf of the KLOE collaboration
Hadron07, Frascati 09/10/2007
Outline:1. The KLOE experiment2. Results on pseudoscalar mesons3. Results on scalar mesons4. Prospects
1. The KLOE experiment at DANEDAFNE @ Frascati
Laboratories• e+e- collider with 2 separate
rings:
s = M= 1019.4 MeV
• Luminosity up to 1.5×1032 cm-2s-1
• 2 interaction regions
1. KLOE 2700
pb-1
2. DEAR (kaonic atoms) 100
pb-1 FINUDA
(hypernuclei) 1100 pb-1
KLOE STATUS:
March 2006: end of KLOE data
taking
2500 pb-1 on-peak 8 × 109
decays
200 pb-1 off-peak (energy scan+1
GeV run)
Dafne test in progress
The KLOE physics program: Kaon physics: CP and CPT violation, CKM unitarity, rare decays, ChPT tests Hadron physics: lowest mass pseudoscalar, scalar and vector mesons Hadronic cross-section below 1 GeV: hadronic corrections to g-2
List of the decays: branching ratios and number of events “on tape”B.R. Nev KLOE (2.5 fb-1)
K+K- 0.49 3.7 109
K0K0 KSKL 0.33 2.5 109
0.15 1.1 109 1.3 10-2 9.7 107
1.2 10-3 9.0 106
’ 6.2 10-5 4.6 105
(f0(980), ) 3 10-4 2.5 106
(a0(980)) 7 10-5 4.6 105
KK(f0(980), a0(980)) ? ?
Initial State Radiation e+e-
The KLOE detector: A large drift chamber A hermetic calorimeter A solenoidal superconducting coil
Drift Chamber (He-IsoBut. 2m × 3m)
E.M. Calorimeter (lead-scintillating fibres)
Magnetic field (SuperConducting Coil)
= 0.52 T (solenoid)
)(%4.5
GeVEEE
psGeVEps
t 130)(
55
%4.0)(
p
p
Results presented here:2.1 Precision measurement of the mass2.2 Improved measurement of the - ’ mixing
(also 0)2.3 Dynamics of 3 decays 2.4 Measurement of KS 2.5 Preliminary measurement of B.R.(-e+e-)2.6 A flash on 0
2. Results on pseudoscalar mesons.
Talks by: F.Ambrosino, A.De Santis, B.Di Micco, R.Versaci (Light Meson Spectroscopy I) M.Martini (Low energy QCD)
2.1 Precision measurement of the mass
Motivated by the discrepancy between the two best measurements:NA48 (2002)M() = 547.843 ± 0.030 ± 0.041 MeVGEM (2005) M() = 547.311 ± 0.028 ± 0.032 MeV
( >10 , PDG average gives a scale factor of 5.8 !)Recently a new measurement has been published by CLEO:
CLEO (2007) M() = 547.785 ± 0.017 ± 0.057 MeV
KLOE method: analysis of fully neutral 3 events with with
3 clusters in the calorimeter only.Kinematic fit with 4 constraints ==> energies by cluster positions Discrimination between and very easy from Dalitz plot.Absolute energy scale from the e+e- center of mass energy s(kinematic fit input) - calibrated comparing M() obtained by the energy scan to the PDG value (dominated by CMD-2)
KLOE final result: M() = 547.873 ± 0.007 ± 0.031 MeVSystematic error due to: - detector uniformity; - Dalitz plot cuts. mass check: M() = 134.906 0.012 0.048(compatible at 1.5 with PDG)
3 Dalitz plot mass peak
2.2 Measurement of the – ’ mixing
KLOE method: measurement of
R B.R.( ')B.R.( )
2002 result (Phys.Lett.B541,45) Lint= 16 pb-1 , final states2007 result (Phys.Lett.B648,267) Lint=427 pb-1 , final states
2002 2007
N() 5 107 1.4 109
N() 5 104 1.7 106
N(’) 120 3400
R (4.70 0.47 0.31) 10-3
(4.77 0.09 0.19) 10-3
BR(’) (6.10 0.61 0.43) 10-5
(6.20 0.11 0.25) 10-5
P(*) (41.8 +1.9 -1.6)o (41.4 0.3 0.9)o
Errors are now dominated by “intermediate and ’ B.R.s”:(BR(’ ) known @ 3%, BR((’ ) @ 5.7%)
(*) evaluated according to A.Bramon et al., Eur.Phys.J. C7, 271 (1999)
KLOE analysis uses the constraints:J.L.Rosner, Phys.Rev. D27 (1983) 1101,A.Bramon et al., Phys.Lett. B503(2001) 271E.Kou, Phys.Rev.D63(2001) 54027
Y1: ’ Y2: ’ Y3: R Y4: ’A >3 effect is found:
Z2’ = 0.14 0.04
P = (39.7 0.7)o
' X ' qq Y ' ss Z ' gluons
R.Escribano, J.Nadal (JHEP 0705,006,2007) reanalyze all V P and P V decaysupdating wavefunction overlaps parameters and neglecting the Y1 constraint no evidence of gluonium content
Experimentally:improve (’), BR(’), ’,BR(0)
Constrain to the ’ gluonium content:
e+e- 0: interference pattern between decay and continuum:fit of cross-section s dependence using 2 decays channels of the .
Cross-section parametrization:
Preliminary results:BR(0)=(5.63±0.70)×10-5
()/()=0.0934±0.0021
Using PDG values for the main decay we get: BR()=(8.40±0.19)% (error reduced to 2%, central value shifted –6%)
2.3 Dynamics of the 3 decay'3 decay isospin violation in strong interactions mu md ms
A test of low energy effective theories of QCD
KLOE has studied with high statistics the dynamics of both channels:(a)Dalitz plot analysis: 1.34 106 events(b)”slope” analysis: 0.65 106 events
(a) Dalitz plot (submitted to Phys.Lett.B):- large statistics- negligible background- use X and Y variables
Fit results of the Dalitz plot
Comments: 0. the odd terms (c and e) in X are compatible with 0 (no asymmetries); 1. the quadratic term in X (d) is unambiguosly different from 0; 2. the cubic term in Y (f) is needed to get an acceptable fit; 3. the b=a2/2 (current algebra rule) is largely violated.
Including systematic errorsa=-1.090 0.005 +0.008 -0.019
b= 0.124 0.006 0.010d= 0.057 0.006 +0.007 -0.016
f= 0.14 0.01 0.02
Dalitz plot asymmetries test of C invariance
All asymmetries are compatible with 0 up to the 10-3 level
Left-Right C-invarianceQuadrant C-invariance in I=2 amplit. Sextant C-invariance in I=1 amplit. (see J.G.Layter et al.,Phys.Rev.Lett.29 (1972) 316)
KLOE results: x 5 statistics respect to best previous experiment
(b) Fit results of the ”slope”
The slope is evaluated by comparing the z distribution of the data with a Montecarlo simulation with =0 (pure phase space) High sensitivity to the M() value (Dalitz plot contour)
MC with M()=547.3 MC with M()=547.822
New (preliminary) result: = -0.027 0.004 +0.004 -0.006
in agreement with Crystal Ball (=-0.0310.004);
2.4 Measurement of the decay KS BR estimated by ChPT @ order p4 (G.D’Ambrosio, D.Espriu, Phys.Lett.B175 (1986)27)
KLOE method: KSKL
- KS tagging provided by KL interacting in the calorimeter:
- Large background from KS decay (105 times more frequent)
Red= MC signalBlue= MC backgroundPoints=data
BR(KS )=(2.27 0.12(stat) 0.05(syst))10-6
Result compared to other experiments and theory
KLOE preliminary result based on 622 pb-1 (1/4 of full data sample)Event selection:
4 tracks events + 1 photon (363 MeV );Kinematic Fit-e recognition (kinematic and calo PiD (in progress))
Backgrounds:other decays (mainly and with conversion)charged kaon decays +
2.5 Preliminary measurement of BR(-e+e-)
-Up to now poorly measured (4 events CMD-2, 16 events CELSIUS-WASA);(WASA@COSY program)
-BR predicted by ChPT and VMD models (2.63.6 × 10-4);-Plane asymmetry “unconventional” CP violation ;(D.Gao, Mod.Phys.Lett.A17 (2002) 1583)
Fit of Minv(ee) with signal + background 733±62 signal events (×36 with respect to previous experiments)
Total efficiency = 11.7%Systematic uncertainty still under evaluation
BR(-e+e-)=(2.4 ±0.2stat± 0.4syst) × 10-4
() data pointssignalother decaysother bckg (mainly K±)
In progress: asymmetry Few % level sensitivity
ChPT “golden mode” KLOE has presented a 3 signal (only 1/5 of full statistics)
The signal is confirmed in the full data sample. B.R. updated result with the full sample will have ~15% error
2.6 A flash on 0
4 mass spectrum of selected events(1.5 fb-1 2005 data).Yellow = expected bck.Points = data
CB@MAMI-B: BR=(22.4±4.6±1.7) ×10-5
3. Results on scalar mesons.KLOE contribution to the understanding of the lowest mass scalars:
f0(980), a0(980), (500) through radiative decays in pairs of pseudoscalars
(1020)
Mass (GeV/c2)
a0(980)
I=0 I=1/2 I=1
f0(980)
(500)
(800)
0
1
Motivations: 1. |ss> scalar quark composition
of f0(980), a0(980) 2. Search for evidence of (500)
Results presented here: 3.1 KLOE results on f0(980) 3.2 High statistics study of 3.3 Search for the decay K0K0
Talks by: S.Fiore, F.Nguyen (Light Meson Spectroscopy II)
Large “unreducible” backgrounds for both channels:0 and 0 for ;ISR, FSR and for
Extraction of the scalar amplitude fit of the spectrum parametrization of signal and background
KLOE observed the decay f0(980) in and 00 channels: : Phys.Lett.B634 (2006) 148;
: Phys.Lett.B537 (2002) 21; Eur. Phys.J. C49 (2006) 433;
3.1 Update of KLOE results on f0(980)
f0(980)Dalitz plot
mass spectrum
Comments:1.The Kaon-Loop well describes the mass spectra;2.The f0(980) is strongly coupled to the s quark: gf0KK > gf0+-
3.The scalar amplitude has a large low mass tail (m<600 MeV) that can beinterpreted as due to the (600);In progress: combined fit with improved background amplitudes
Attempt to describe both spectra with a unique scalar amplitude.[Achasov and Kiselev, Phys.Rev.D73 (2006) 054029]:Scalar amplitude = f0(980) + (600) + interference.
(600) parameters and /KK scattering phases fixed(10 different parameter sets, see Eur. Phys.J. C49 (2006) 433)
free parameters: Mf0, gf0KK , gf0+- Preliminary results (uncertainties under evaluation) are encouraging:
Mf0(MeV)
gf0KK
(GeV)gf0+-
(GeV)P(2)
982.1 4.0 -1.7 6.3% 983.7 4.7 -2.2 2.5%
3.2 High statistics study of : the a0(980).
• Selection of:1. events with : fully neutral 5 events;2. events with : 2tracks and 5 events
• Background subtraction: 18% in sample 1, 13% in sample 2• Event counting: 18400 in sample 1, 3600 in sample 2
“Pure” final state, dominance of a0(980) intermediate state
Preliminary results on the branching ratioB.R.( )(1) = (6.92 0.10stat 0.20syst) 10-5
B.R.( )(2) = (7.19 0.17stat 0.24syst) 10-5
in good agreement, (part of the systematic errors are common).Error improvement: 9% (Phys.Lett.B536 (2002) 216) 3% (this result)
• M() spectra• Combined fit of the spectra with a0 production parametrizations(convoluted with efficiencies and resolutions)
The fit parameters (preliminary). Ratio BR( )/BR( ) BR( ) contribution(KL) Kaon-Loop:(N.Achasov,A.V.Kiselev, Phys.Rev.D73(2006)054029) Ma0, couplings ga0KK ga0, phase
(NS) Breit-Wigner + polynominal “background”:(G.Isidori et al., JHEP0605 (2006) 049) Ma0, couplings ga0 ga0KK ga0
KL fit: points =datared =fitting curve (model efficiency and resolution)
Comments:1. Good consistency between sample 1 and 2: the result is experimentally “solid”; 2. KL fit is stable, NS requires to fix some parameters; Results: 2.1 ga0KK ~ 2 GeV and ga0KK / ga0 ~ 0.8 “conflict” with qqqq hypothesis; 2.2 Large values of BR( ) and of ga0
sizeable coupling with the (as for f0(980))
Meson gM (GeV-1)
0 0.13
0.71
´ 0.75
a0(980) 1.6
f0(980) 1.2 – 2.7
Other descriptions: Unitarized Chiral Model [Palomar et al., Nucl.Phys.A729 (2003) 743] KK molecule [Kalashnikova et al., Eur.Phys.J.A24 (2005) 437] Linear Sigma Model [Bramon et al., Phys.Lett.B494 (2000) 221]
3.3 Search for the decay KSKS
In K0K0 the K0K0 pair is:in a J=0 state = [|KSKS>-|KLKL>]/2;in a I=0,1 isospin state a0 and f0 contribute;
Very small allowed phase space: 2MK < MKK < Msmall B.R.Predictions on B.R.: from 10-13 (no scalar contribution) up to 10-7 We have used the decay chain: KSKS ()() 4 tracks+1 photon (E
max=24 MeV) Overall efficiency = 20.6% Very small bckg (ISR KSKL)
Result (preliminary): (Ldt = 1.4 fb-1)1 event found;0 expected background;
BR( KSKS)<1.810-8 90% CL
4. Prospects. (talks by P.Moskal and D.Domenici (Future facilities))
DAFNE is testing now a new scheme to increase luminosity KLOE phase-2 could start (2009):
~10 times more statistics improved detector (inner tracker, improved calorimeter
readout, tagger, new small angle calorimeters) “enriched” physics program
Kaon, , ’ decays (high statistics) (sigma), 0 2 widthdeeply bound kaonic states (AMADEUS proposal)
Increase the center of mass energy up to 2.5 GeV is also considered (KLOE phase-3)
physics program extended tohadronic cross-section (g-2, em)baryon time-like form factors (DANTE proposal) physics (,’,f0(980),a0(980) 2 widths)
[see http://www.lnf.infn.it/lnfadmin/direzione/roadmap/roadmap.htmlF.Ambrosino et al., Eur.Phys.J. C50,729 (2007)]