KLOE results on hadron physics
description
Transcript of KLOE results on hadron physics
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)]