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

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