Recent KLOE results on Hadron Physics

QNP06 – Madrid – 09/06/06

Cesare BiniUniversita’ “La Sapienza” and INFN Roma

Outline:The KLOE experiment at DAFNE

Results on Scalar MesonsResults on Pseudoscalar Mesons

Prospects for e+e- at Frascati

DAFNE: the Frascati - factory

• e+e- collider with 2 separate

rings: s = M= 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

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)

The detector: A large drift chamber; A hermetic calorimeter A solenoidal superconducting coil

The KLOE experiment

Drift Chamber (He-IsoBut. 2m × 3m)

E.M. Calorimeter (lead-scintillating fibres)

Magnetic field (SuperConducting Coil)

= 0.52 T (solenoid)

)(%4.5GeVEE

E ps

GeVEps

t 130)(

55

%4.0)(

p

p

Physics at a – factory: a window on the lowest mass mesons

Sketch of the decays:

(1020)

a0(980)

f0(980)

'

KK

0-+ 1--

0++

(770)

Direct decayRadiative decay-emission

Main decay channels

Branching fraction

K+K- 49.2 %

KSKL 34.0 %

+ 15.3 %

1.301 %

0.125 %

’ 6.2 × 10-5

1.1 × 10-4

8.3 × 10-5

+ “radiative return” to +-

#events = Br.F. × 8 × 109 ~105 ’, ,

(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 ChPT test

Overview of KLOE physics

(2) Hadron physics: Scalar Mesons ( a0(980), f0(980) (500) ) Pseudoscalar Mesons ( 0, , ’ ) Vector Mesons ( properties of (770), (780) ) (3) Measurement of the Hadronic Cross-Section below 1 GeV

hadronic corrections to g-2

~ 450 pb-1 analysed= 20 × previous analyses

How a -factory can contribute to the understanding of the scalar mesons

(1020)

Mass (GeV/c2)

0.

Scalar Mesons Spectroscopy:f0(980), (500) and a0(980) are accessible (not accessible)through S; Questions:1. Is (500) needed to describe

the mass spectra ?2. “couplings”of f0(980) and

a0(980) to |ss> and to KK, and .

4-quark vs. 2-quark vs. KK molecule

Scalar Mesons

1.

a0(980)

I=0 I=1/2 I=1

f0(980)

(500)

(800)

Scalar Mesons with KLOE

f0(980)K+K-[ 2m(K)~m(f0)~m() ] expected BR ~ 10-6

K0K0““ ~ 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;

a0(980)K+K-expected BR ~ 10-6

K0K0 “ ~ 10-8

(500)

Event selection:2 tracks with t>45o; missing momentum >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

The analysis P.L.B 634 ,148 (2006)

(“trackmass”)

muons

pions

(Likelihood: Tof and Shower shape)

electrons

pions, muons

Particle identification: vs. e and

m() (MeV)

The final state is dominated by:Initial State RadiationFinal 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

dataMC no f0

MC with f0

Events

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-, gf0, b0,b1

Free parameters: scalar amplitude + background

Mass values ok

An acceptable fitis obtained with both models:P(2)(KL)=4.2%P(2)(NS)=4.4%

gf0K+K-> gf0

“Large” coupling to the

B.R.( f0(980) ) = 2.1 2.4 × 10-4 (from integral of |Amplitude|2)

The analysis

Event selection:5 photons with >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 0) using the same 2 models: Improved Kaon-Loop model (introducing the (500 “No Structure” model

Parameters: mass and couplings ( mf0, gf0, gf0K+K-, gf0) + backgroundThe (500) parameters are fixed. The fit is repeated by changing them

2-dim fit shownslice bt slice.A good fitis obtained with both models:P(2)(KL)=14%P(2)(NS)= 4%

Fit results

Comments:(500) is needed in KL fit [p(2) ~ 10-4 14% !]

(best parameters are: M=462 MeV, =300 MeV);

f0(980) parameters agree with analysis KL fit again R > 1 (gf0KK > gf0);

NS fit gives large gf0 but R<1 (??); BR extracted: integral of |scalar amplitude|2

f0(980) param. NS model KL model

mf0 (MeV) 981 ÷ 987 976 ÷ 987

gf (GeV-1) 2.5 ÷ 2.7 -

gf (GeV) 1.3 ÷ 1.4 1.4 ÷ 2.0

gfKK (GeV) 0.1 ÷ 1.0 3.3 ÷ 5.0

R=g2fKK /g

2f 0. ÷ 0.9 3.0 ÷ 7.3

BR( ) ~ 1/2 × BR(): neglecting KK, we add the 2 BRsBR(f0(980)) = (3.1 ÷ 3.5) × 10-4

(f0(980)) = 1.2 ÷ 1.6 keV

Simultaneous analysis of 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

The analysis

Scalar Mesons: Summary and Outlook

1) Complete analysis of f0(980) 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

2) Work in progress to: make a combined analysis of f0(980) and

complete the analysis of a0(980) with a0(980)

study the decay chain [f0(980)+a0(980)] (expected sensitivity down to 10-8)

3) Further studies: search for e+e- e+e-events ( ) 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 P 8 ×107 9 ×106 0

4 ×105 ’

List of the analyses done or in progress

Measurement of the (and 0) masses this talk

Measurement of the – ’ mixing angle in 3 Phys.Lett.B541 (2002) 45

Measurement of the – ’ mixing angle in 7 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( ) AIP:Conf.Proc.814:463,2006

Upper limit on the C-violating decay 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: M()=(532 ± 41 ± 52) keV/c2 (errors added in quadrature)

KLOE: ; check with 0; 0Technique: kinematic fit mostly based on photon positions and timing;

energy-momentum and vertex position from large angle Bhabha scattering

3 Dalitz-plot

Mass (MeV)

The and the peak are well defined

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 GEMM() = ( 547822 5stat 69syst ) keV

Results (still preliminary):The statistical uncertainty is ~negligible

Systematic uncertainties from knowledge of s and vertex position(work in progress to reduce it)

KLOE

NA48

GEM (see Kirillov @ QNP06)

mass (MeV)

Measurement of the – ’ mixing angle in 7

Method: measurement of using similar and ’ decay chains

Previous analysis: ’

This analysis: ’ ’

427 pb-1 2001/2002 data

N() = 1665000 1300 (no

bck)

N(’s) = 375060

(Nbckg= 345)

N(´) = 3405 ± 61stat

± 28syst

signal (no bck)’ signal (~10% bck)

The systematic uncertainty is due to the uncertainty on the intermediate BRs

5

3

1028.012.024.6

10)20.009.079.4(

BR

R sysstat

thsysstatP 6.07.03.04.41Mixing angle

X2+Y2 = 0.93 ± 0.06

Before KLOE results Including new KLOE result

(1)Pseudoscalar mixing angle: extracted using the parametrisation [A.Bramon et al. 1999]

(2) Analysis of ’ gluonic content: [E.Kuo, 2001]

32

2

2sin

tan1cot

p

p

Z

Z

m

m

BR

BRR

P

V

S

NSsP

Prospects for e+e- physics at Frascati

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 – factory (L~1033 cm-2s-1) energy scan: √s = 1 ÷ 2.5 GeV (L~1032 cm-2s-1)

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

3 Expressions of Interest have been presented:

KLOE2 Kaon physics + / ’ physics @ physics + hadronic cross-section up to 2.5 GeV

AMADEUS deeply bound hypernuclei @

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

Provided and are therethe scalars have an“Inverted Spectrum”

Pseudoscalar multi-plet Vector multi-plet

Analysis of the mass spectra of the lowest mass mesons

Scalar multi-plet:(500), (700), f0(980), a0(980)

Inverted Mass spectrum hint of a 4q picture

Q=0 Q=0 Q=1 Q=-1 (the f0(980) and a0(980))

duud

dusdduusdsudsuud

susddsusdssdsuus

I3=0 Q=0 (the (500))

Q=0 Q=1 Q=0 Q=-1 (the (800))add 1Quark s

add 2Quarks s

Building Rule:Mass

2 important consequences: if 4q hypothesis is correct the (500) and the (800) have to be firmly established the s-quark content of f0 and a0 should be sizeable ( f0 and a0 couplings with (ss) and with kaons

[N.N.Achasov and V.Ivanchenko 1989]

S to gS (GeV-1)S to kaons gSKK=gSK+K-=gSK0K0 (GeV)f0 to (I=0) gf0=√3/2 gf0=√3 gf0 (GeV)a0 to (I=1) ga0(GeV)Coupling ratioRf0=(gf0K+K-/ gf0)2

Ra0=(ga0K+K-/ ga0)2

K+

K-

+

-

+

-Kaon-loop No-structure

f0,a0f0,a0

Definition of the relevant couplings (S=f0 or a0):