moriond qcd, mar., 2007, s.uehara 1 new results on two-photon physics from belle s.uehara (kek) for...
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Moriond QCD, Mar., 2007, S.Uehara 1
New Results on Two-Photon Physics from Belle
S.Uehara (KEK)for the Belle Collaboration
Rencontres de Moriond, QCD and Hadron interactionsMar.17-24, 2007
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Moriond QCD, Mar., 2007, S.Uehara 2
Motivation of Two-Photon Physics
1. Resonance formation
hadrons
2. Hard scattering with a quark line
Hadron production from two quasi-real photon (|q2|<0.001GeV2, with no-tag condition) Exclusive processes with W=0.8 - 4.5 GeV at KEKB/Belle Light-quark resonances, Charmonia Perturbative/Non-perturbative QCD, Hadron production mechanism Wide energy region --- Various physics aspects can be studied simultaneously.
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Moriond QCD, Mar., 2007, S.Uehara 3
KEKB Accelerator and Belle Detector• Asymmetric e- e+ collider
Beam crossing angle: 22mrad
•Continuous injection
•Luminosity Lmax=1.71x1034 cm-2s-1
∫ Ldt 710 fb-1 (by the end of 2006)
8 GeV e- (HER) x 3.5 GeV e+ (LER)
s=10.58 GeV (4S)
High momentum/energy resolutions CDC+Solenid, CsIVertex measurement – Si stripsParticle identification TOF, Si-aerogel, CDC-dE/dx, RPC for KL/muon
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Moriond QCD, Mar., 2007, S.Uehara 4
Reactions at KEKB/Belle
The cross sections observable there e+e(4S)BB --- 1.1 nb e+eqq (uds) --- 2.1 nb e+ecc --- 1.2 nb e+e --- 0.9 nb hadrons (W>0.8GeV) --- ~1 nb (within the acceptance)
Luminosity Function for quasi-real collisions
d(in ee) = (in ) L(W) dW0.0001
0.001
0.01
0.1
0 1 2 3 4 5
W, gamma gamma c.m. energy (GeV)
Lum
inos
ity fu
nctio
n (1
/GeV
)
Calculated with equivalent-photon approximation
Ee+e-=10.58GeVQ2
max=1GeV2
Lum
inos
ity f
unct
ion
(1/G
eV)
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Moriond QCD, Mar., 2007, S.Uehara 5
C = + resonances: Peak structure in the invariant mass distributionTest of QCD: c.m.-energy (W) dependence and angular dependence in high energiesGeneral Analysis strategy Invariant-mass of hadron pair = W (c.m. energy of ) Quasi-real two-photon collisions with final state fully reconstructed --- strict transverse momentum balance is required (| pt| <50 - 200 MeV/c ) This gives efficient background rejection
Two-hadron exclusive final statesMeson/baryon
Meson/anti-baryon
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Moriond QCD, Mar., 2007, S.Uehara 6
K0SK0
S
M(KSKS) |cosθ|<0.6
hep-ex/0609042
Preliminary
Selection: - Ks reconstruction from pairs with a detached vertex - pt-balance requirement
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Moriond QCD, Mar., 2007, S.Uehara 7
Angular distribution; comparison with theories
- qq qqqq with wave function --- (M.Benayoun, V.L.Chernyak)- qq w/ hadronic exchange (handbag) --- (M.Diehl, P.Kroll, C.Vogt) cJ region (check evaluation of angular acceptance)
DKVBC
Preliminary
BC
DKV(handbag)
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Moriond QCD, Mar., 2007, S.Uehara 8
)(/)( 00 KKPLB615,39(2005) = 0.89±0.04±0.15
Cross section; KS0KS
0/K+K ratio
Previous study:
)6.0|cos(|
])[(0
nbW )()( 00
KKKK SS
W-n dep. Preliminary
σ0(KSKS)/σ0(K+K-) approaches BC as W→∞
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Moriond QCD, Mar., 2007, S.Uehara 9
cJ KS0KS
0 decays
process c0 KS0KS
0 c2 KS0KS
0
Br(KS0KS
0) (eV) 7.00 0.65 0.71
0.31 0.05 0.03
Br(KS0KS
0) / Br(K+K) 0.49 0.07 0.08
0.70 0.21 0.12
Consistent with isospin inv. ratio = 0.5
Preliminary
Product of two-photon decay width () and branching fraction to K0
SK0S
Preliminary
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Moriond QCD, Mar., 2007, S.Uehara 10
())( MvsM )()( 00
vsMM
- Select (X)- Combining
(X)
00cc
00 cwith unseen
hep-ex/0609048
p
Ldt= 464fb-1
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Moriond QCD, Mar., 2007, S.Uehara 11
Nxxc
00
2.10.34.162.101
0.02.12.91.36
49.052.001.121.6
98.003.150.280.9
13.007.011.007.014.089.0
20.014.018.015.036.040.1
])[( eVxxBr 310)( xxBr
49.036.1)(/)(
26.086.0)(/)(00
ppBrBr
ppBrBr
4.03.0)(/)(
5.0)(/)(00
ppBrBr
ppBrBrmay be slightly larger than diquark prediction of
c results from the three processes
pp (PLB 621,41(2005)) 7.201.53 0.670.75
Preliminary
Preliminary
BB Br(BB) [eV] Br(BB)
PRD 38, 3516 (1988)
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Moriond QCD, Mar., 2007, S.Uehara 12
<
460/fbPrelim.
Energy dependence of the cross sections
Preliminary
Compatible with L3 but not with CLEO
Cross sections ofthe three processescome close above3 GeV
<
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Moriond QCD, Mar., 2007, S.Uehara 13
f0(980) – is ordinary qq meson? - an exotic state? - some special theory needed?
The two-photon coupling is acrucial key.Prediction of uu, dd --- 1.3 – 1.8 keV ss --- 0.3 – 0.5 keV KK molecule --- 0.2 – 0.6keV
f0(980) appears as a small but statistically significant peak.
f2(1270)
f0(980)
separation:by comparing energy deposit in the ECL between data & MC
PRD 75, 051101(R) (2007)f0(980) in
85.9fb-1
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Moriond QCD, Mar., 2007, S.Uehara 14
M [MeV/c2]
[MeV]
[eV]
1.12.16.15.16.985
8.89.135.28.112.34
1479511783205
Fit of the f0(980) line shape
)6.0|cos(|
])[(0
nbW
No ’(P and CP) seen near 958MeV/c2
New upper limit for Br(’), Preliminary(interference with the non-resonant process allowed) < 3.3 10-4 (no interference)
f0(980)
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Moriond QCD, Mar., 2007, S.Uehara 15
Other cJ(1P,2P) measurements
Nevents 64±18(5.3σ)
M[MeV/c2] 3929±5±2
[MeV] 29±10±2
Br [keV] 0.18±0.05±0.03
Observation of a new charmonium Z(3930)
Br ( c0Br ( cKK 1.6 2.3 Br ( c2 0.14 0.11
Br ( c20.44 0.76 0.14 Br ( c2J 11 9 2
DD
Previous two-photon measurements of(cJ(1P))Br from Belle (eV)
A c2(2P) candidate (from ang. distribution)
PLB 615, 39 (2005)
PLB 540, 33 (2002)
PRL 96, 082003 (2006)
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Moriond QCD, Mar., 2007, S.Uehara 16
Summary
Exclusive hadronic final states from two-photon collisions in no-tag mode are measured at Belle.
These results are used to study resonances and test QCD models.
- KS0KS
0 final state above 2.4 GeV much smaller cross section than K+K-
cJ charmonia measured
- preliminary results --- c seen, comparison with pp- f0(980) shows a small peak in
- Charmonia: two-photon decay width and/or ratios among branching fractions are measured for
c, c0, c2 and a c2(2P) candidate
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Moriond QCD, Mar., 2007, S.Uehara 17
Backup slides
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Moriond QCD, Mar., 2007, S.Uehara 18
K0S seletion
Selection: Ks reconstruction from pairs with a detached vertex
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Moriond QCD, Mar., 2007, S.Uehara 19
Fitting formula for f0(980)
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Moriond QCD, Mar., 2007, S.Uehara 20
Angular distribution
Amplitude analysis is now going on.
Preliminary
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Moriond QCD, Mar., 2007, S.Uehara 21
c2(2P) candidate
Nevents 64±18(5.3σ)
Mass[MeV/c2] 3929±5±2
[MeV] 29±10±2
B [keV] 0.18±0.05±0.03
Observation of a new charmonium Z(3930)DD
A candidate of c2(2P) (from angular distr.)
PRL 96, 082003 (2006)
395fb-1
Spin-0 (dashed)
Spin-2, helicity-2 (solid)
|pt| distribution
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Moriond QCD, Mar., 2007, S.Uehara 22
Other cJ(1P) measurements from Belle
r ( c0Br ( cKK 1.6 2.3 Br ( c2 0.14 0.11
Br ( c20.44 0.76 0.14 Br ( c2J 11 9 2
PLB 615, 39 (2005)
PLB 540, 33 (2002)
87.7fb-1
Previous two-photon measurements of(cJ(1P))B from Belle (eV)
M(ll)-M(ll)