KLOE results on hadron physics
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Transcript of KLOE results on hadron physics
KLOE results on hadron physicsCesare Bini
Università “La Sapienza” and INFN Roma
MENU07, Julich 11/09/2007
Outline:1. The KLOE experiment2. Results on pseudoscalar mesons3. Results on scalar mesons4. Prospects
1. The KLOE experiment at DANE
DAFNE @ 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
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)
December 2006 - June 2007: FINUDA run
Now: machine tests and preparation of SIDDHARTA (kaonic
atoms) run
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 =σ
psGeVEps
t 130)(
55 ⊕=σ
%4.0)(<
⊥
⊥
ppσ
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
The lowest mass pseudoscalar mesons (JPC=0-+) are accessibleat a - factory through the decays:
B.R. Nev KLOE (2.5 fb-1)K+K- 0.49 3.7 109
K0K0 KSKL 0.33 2.5 109
1.3 10-2 9.7 107
1.2 10-3 9.0 106
’ 6.2 10-5 4.6 105
Results presented here:2.1 Precision measurement of the mass2.2 Improved measurement of the - ’ mixing2.3 Dynamics of 3 decays 2.4 Measurement of KS 2.5 Other analyses in progress (, -e+e-)
2. Results on pseudoscalar mesons.
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 σ, PDG average gives a scale factor of 5.8 !)Recently a new measurement has been presented 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
KLOE final result: M() = 547.873 ± 0.007 ± 0.031 MeVSystematic error due to: - space uniformity; - Dalitz plot cuts. mass check: M() = 134.906 0.012 0.048(well compatible with PDG value)
3 Dalitz plot mass peak
2.2 Measurement of the – ’ mixing
KLOE method: measurement of
€
R =B.R.(φ→η 'γ )
B.R.(φ→ηγ )
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 >3σ effect is found:
Z2’ = 0.14 0.04
P = (39.7 0.7)o
€
' = Xη ' qq +Yη ' ss + Zη ' gluons
R.Escribano and J.Nadal (JHEP 0705,006,2007) reanalyze all V P and P V decaysupdating wavefunction overlaps parameters ==> no evidence of gluonium content
Experimentally:improve (’), BR(’), ’measurements
Constrain to the ’ gluonium content:
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:
Dalitz plot analysis:1.34 106 events
”slope” analysis:0.65 106 events
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.
According to B.Borasoy and R.Nissler (Eur.Phys.J.A26 (2005) 383)it is difficult to accomodate such a small b value in a ChPT approach
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
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 value of M() (Dalitz plot contour)
MC with M()=547.3 MC with M()=547.822
New 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 0.13(stat) +0.03 -0.04(syst))10-6
Result compared to other experiments and theory
0: ChPT “golden mode” 3σ signal (only 1/5 of full statistics)
Updated B.R. result soonwith 15% statistical error
signal confirmed in full data sample.
2.5 Others (2 flashes on other ongoing KLOE analyses)1 +-e+e-: signal observed:1500 events expected with 2.5 fb-1
Few % sensitivity on plane asymmetry (CP violation, D.Gao, Mod.Phys.Lett.A17 (2002) 1583)
3. Results on scalar mesons.KLOE contribution to the understanding of the lowest mass scalars:
f0(980), a0(980), σ(500)
through radiative decays in pairs of pseudoscalars
(1020)
Mass (GeV/c2)
a0(980)
I=0 I=1/2 I=1
f0(980)
σ(500)
(800)
0
1
S (I=0)f0 σ (I=0) f0 σ
(I=1) a0
K+K- (I=0,1) f0 a0
K0K0(I=0,1)f0 a0Motivations: 1. |ss> scalar quark composition 2. Search for evidence of σ(500)
Results presented here: 3.1 Review of KLOE results on f0(980) 3.2 High statistics study of (preliminary) 3.3 Search for the decay K0K0:
KLOE has 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;Dalitz plot FB asymmetry
Fit results:1.The Kaon-Loop well describes the mass spectra;2.The f0(980) is strongly coupled to the s quark: gf0KK > gf0, gf0is large3.The scalar amplitude has a large low mass tail (m<600 MeV) that can beinterpreted as due to the (500) (not clear results yet);
3.1Review of KLOE results on f0(980)
mass spectrum
f0(980)
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, expected dominance of a0(980) intermediate state
B.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 two spectra with a0 production parametrizations(convoluted with efficiencies and resolutions)
The fit parameters. 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 hypothesys (not for f0(980)); 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
3.3 Search for the decay KSKS
InK0K0 the K0K0 pair is:in a J=0 state = [|KSKS>+|KLKL>]/2;in a I=0,1 isospin state a0 and f0 can 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 : (Ldt = 1.4 fb-1)
1 event found;0 expected background;
BR( KSKS)<1.810-8 90% CL
4. Prospects.
The DAFNE team 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)
The possibility to increase the center of mass energy up to 2.5 GeV isalso 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)]
Conclusions:Hadron Physics is an important part of the KLOEprogram;Many results have been obtained;Others are to come:
full data sample to be analysedmore channels not yet analysed