Post on 04-Feb-2016
description
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20041
Isospin breaking a0-f0 mixing
Markus BüscherForschungszentrum Jülich
Germany
... a tool to investigate (not only!) the structure of the light scalar mesons
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20042
Nature of these states??„Genuine“ qq4-quark statesKK molecules
The light scalar resonances
COSY
S
I
K*(?)
K*(?) K*(?)
K*(?)
a0-(?) a0
0(?) f0(?) a0+(?)
f0(?)
Nonet of light scalar mesons JP=0+ f0(500) (““)
f0(980)a0(980)
f0(1370)K0*(1430)a0(1450)f0(1500)f0(1710)
Possible candidates
9 states}10 states}
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20043
Observables?
KK
(KK/) = (0.183±0.024) (“seen“/“dominant“)
(KK/) = ... (“seen“/“dominant“)
a0– a0
0 f0 a0+
I3= –1 0 +1
m = (984.7±1.2) MeV/c2 (“average“) = (50...100) MeV/c2 (“estimate“)
m = (980±10) MeV/c2 (“estimate“) = (40...100) MeV/c2 (“estimate“)
a0
f0
Observables at COSY (yet unknown): Mass distributions Branching ratios to KK and (Differential) production cross sections Isospin ratios (e.g. pn vs. pp reactions) a0-f0 mixing Polarization observables
COSY limit
a0
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20044
The Accelerator: COSY-Jülich
COSY (Cooler Synchroton)at FZ-Jülich:
• (polarized) p & d beams
• phase-space cooling– electron & stochasting cooling
• p = 0.30 – 3.70 GeV/c– pp pp X (mX 1.1 GeV/c2)– dd X (mX 1.03 GeV/c2)– pp pK+ Y* (mY* 1.5 GeV/c2)
• internal & extracted beams
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20045
The detectors: ANKE & WASA
WASA ANKE
In operation since1998
Ready for experimentsin 2006
-currently at CELSIUS (Uppsala)-nearly 4 coverage-charged and neutral particle i.d.-frozen pellet target (L ~ few1032 cm-2s-1)
-forward spectrometer (small acceptance)-optimized for K+/K- detection-cluster jet target (L ~ few1031 cm-2s-1)
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20046
The a0/f0(980) at COSYReaction Where? Result Goal
pp pp K+K- COSY-11ANKE
a00/f0 contribution??
pp d K+K0 ANKE a0+ channel
dominates
d + WASA First „simple“ experiment
for WASA (2006)
pn d K+K- ANKE (Feb. 2004)
d 0 WASA Angular asymmetriesa0-f0 mixing
pd 3He K+K- MOMO a00/f0 contribution??
3H K+K0
dd 4He K+K- ANKE Winter ’04/05?
4He 0 WASA Isospin violationa0-f0 mixing
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20047
p(2.65 GeV)pdK+K0 at ANKE
Fit:Fit:[(KK)S d]P + [(KK)P d]S
tot(pp dK+K0) = (38 ± 2stat ± 14sys) nb
Q = 46 MeV
•K+d coincidence measurement•Identification of ppdK+X events via TOF, E and particle momenta•Identification of ppdK+K0 events via dK+ missing mass
Dominance of a0+ channel
K+ d
m(K
+)+
m(K
0)
83%
V.Kleber et al., PRL 91, 172304 (2003)
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20048
a0-f0 mixing in dd 4He 0
Strength of a0-f0 mixing unknown• Probably larger than 0- mixing• Close & Kirk: mixing intensity = 8±3% (data from WA102) but critizised by Achasov & Kiselev, Oller
dd 4HeX cross section unknown• Our estimate: (dd 4He a0
0) ~ (50 ... 200) pb• Pilot measurement: dd 4He a0
0/f0 4He K+ K–
Similar to dd 4He 0 experiment @IUCF
Direct production of a00 in dd 4He a0
0 ( 0) is forbidden if isospin is conserved
(12.7 ± 2.2) pb
(15.1 ± 3.1) pb
E.J.Stephenson et al.,Phys. Rev. Lett. 91, 142302 (2003)
ANKE
Dominant channel dd 4He f0(I=0) 4He a0
0(I=1) 4He 0 ??
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 20049
dd (0) vs. dd 0
CSB in propagationof a0/f0
production
Details in: C.Hanhart, nucl-th/0306073
20m
Production
nPropagatioCSB
00 /fa
N
m
1
0000 /fa/fa
00/faN m m-
1
t
1
<<d d
a0
0
d d
f0
a0
0
d d
0
d d
0
?
or 0/
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200410
More a0-f0 mixing ...
f0 a0
K0
K0
_
Further enhancement: “Kaon loops“
f0 a0
K–
K+
8 MeV
“normal“ CSB
o(1%)
N.N.Achasov et al., PLB 88, 367 (1979)
CS
B a
mp
litu
de
d d
f0
a0
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200411
a0/f0 mixing in pn interactions Look, e.g., for angular asymmetries around 90°in pn d+Meson reactions
V.Grishina et al., PLB 521, 217 (2001) V.Kudryavtsev et al., PRC 66, 015207 (2002)
no mixing
„direct“a0-f0 or -
mixing
Kaon loops
angular distribution of the a0 mass distributionpn pn(d) 0
a00 a0
0
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200412
People ...M.Büscher, C.Hanhart, V.Hejny, S.Krewald, A.Sibirtsev, H.Ströher
IKP, FZ Jülich
U.-G.MeißnerHISKP, Universität Bonn / IKP, FZ Jülich
V.KleberIKP, Universität zu Köln
P.Fedorets, L.Kondratyuk, A.KudryavtsevITEP, Moscow, Russia
V.GrishinaINR, Moscow, Russia
A.Dzuba, V.Koptev, S.Mikirtychiants, M.NekipelovPNPI, Gatchina, Russia
and the ANKE collaborationExperimentTheory http:www.fz-juelich.de/ikp/anke
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200413
I.d. of ppdK+K0 events @ ANKE
K+
d
T = 2.65 GeV
t
p• K+-d coincidence measurement
• Identification of ppdK+X events via TOF, E and particle momenta
• Identification of ppdK+K0 events via dK+ missing mass
Background < 10%
COSY
beam
Spectrometer dipole
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200414
First Results on the a0+
V.Kleber et al., PRL 91, 172304 (2003)
nucl-ex/0304020
Q = 46 MeV
Fit:Fit:[(KK)P d]S + [(KK)S d]P
tot(pp dK+K0) = (38 ± 2stat ± 14sys) nb
(pp da0+ dK+K0) =
83% · tot
p p d K+K0 (ANKE)
Markus Büscherm.buescher@fz-juelich.de
DPG Frühjahrstagung Mainz 200415
p(2.65 GeV)ndK+K- at ANKE
• D2 as an effective neutron target• K+ K- d coincidence measurement• unobserved spectator proton
First data on -mesonproduction on neutrons
Narrow a00/f0 signal
at small K+K- masses??
K+ d
K-
m(K
+)+
m(K
- )
inv. mass (K+K-)
verypreliminary!!