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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 1
BABAR Results on Hadronic Cross Sections
with Initial State Radiation (ISR)
Peter A. LukinBudker Institute of Nuclear Physics, Russia for the BABAR collaboration
Experimental SeminarLaboratori Nazionali di FrascatiJune 17, 2008
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 2
Motivation&
ISR - Method
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 3
Motivation: High Precision Test of the Standard Model
Anomalous magnetic moment of the muon
Fine structure constant at Z0-mass QED (MZ)
Muon-Anomaly a= (g-2)/2 =
aaaaatheo QED had weak New physics
Hadronic Vacuum Polarization
2nd largest contribution, pQCD not applicableError of hadronic contribution dominates total error of a!
µ+
q
q
µ+
2m4
had3had ds)s(K)s(
4
1
a
Experimental inputinto dispersion integral
• K(s) = analytic kernel-function, • above typically 2…5 GeV, use pQCD
from S. Eidelman
2
1-2 GeV
2-5GeV>5GeV
2
1-2 GeV
2-5GeV
>5GeV
Central Values Uncertainties
Motivation: (gµ-2) and (MZ)
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 4
ISR-physics:
• Already used at KLOE, used at BABAR over a wider energy range
• Whole s' spectrum from threshold to ~ 4 … 5 GeV
• Data comes as a by-product to the main physics goal of PEP-II
• Greatly reduced point-to-point un- certainty with ISR-program at PEP-II
ISR at (4S) Energies
)(sdM
dM hadr
hadr
Hadrhadr
H(s)
Master-Formula:
Radiator-Function (NLO)MC-Generators EVA, Phokhara, AfkQed
J. Kühn, H. Czyż, G. Rodrigo
s’e-
e+ ISR
Hadrons
Mhadr
had
[m
barn
]
s [GeV]
VEPP-2M BES
(4S)
pQCD
s=10.6 GeV
G
AP:
N
o re
cent
data
ISR@PEP-II
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 5
• Rely on tagged (=measured) photon for identifying ISR-events
• Excellent momentum resolution by means of kinematic fit
• High fiducial efficiency : wide-angle ISR- forces hadronic system into
detector fiducial region at large polar angles
• Harder momentum spectrum due to boost - fewer problems with soft particles; - allows to go down to threshold
• Typically systematic uncertainties ~5% up to ~20% depending on mass and channel
ISR at (4S) EnergiesFeatures: Normalitzation:
1) Integr. Luminosity Lint Radiator Function H
OR2) Or better: use e+e- events
xdHL)M())M(1)(M(
)M(dN)M(dL intBorn
FSR
ISR
0 2 4 6 81
10
100
1000
s’ [GeV]
10
LBABAR = 232 fb-1
ISR Luminosity LISR
(pb-1 / 0.1 GeV)Hadrons
ISR
LISR = integrated luminosity in energy scan, corres-ponding to same statistics as the one in ISR method
Large angle Bhabhas Theory
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 6
First ISR Exclusive Hadronic Channels
measurements
89 fb-1
232 fb-1
} - e+e
- e+e 2(KK2(KK - e+e 3(3(2(KK - e+e pp }
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 7
Many new Results since then ....
all based on 232 fb-1
- e+e KKKK- e+e 2(2(KKKK - e+e KKKKSKKS - e+e 00, 00, 00 now available: ~500 fb-1 !
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 8
4 Hadrons: e+e e+e e+e
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 9
Features: • Important mode for a and QED
• Preliminary precision: 8% in peak 5%• Good agreement with SND <1.4 GeV• Huge improvement >1.4 GeV• First measurement >2.5 GeV
BaBar preliminary
(2050)???
e+e
BaBar preliminary
(1700)
(1450)
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 10
Substructures in e+e
intermediate state is also seen
, combine with meas. at 10.6 GeV f0 a1
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 11
(Sub)structures in e+e
+-
non
BaBar preliminary
BaBar preliminary
- For first time is seen, it is large and even dominating the non-- spectrum, surprise in QCD? Combine with BABAR measurement at 10.6 GeV- The structure at 2050 MeV is the (2050)?!
Questions:
New 4 MC (Czyz, Kühn, Wapienik) arXiv:0804:0359
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 12
e+e
• Factor 2.5 more statistics with respect to published result• Search for (1020)f0(980) final state and relation to (1020) f0(980) • BR of J/ and (2S) to (1020)• Search for new states
Motivation:
K+K+
• Systematic error 8% (was 15%)• Error dominated by acceptance
K+K0
• First measurement ever !• Systematic error 11%
BABARBABAR
PRD-RC 74 (2006) 091103
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 13
Structure in e+e f0(980)
New state with JPC=1- - with mass of 2.175 GeV and 58 MeV width ?
Toy MC gives <10-3 probability for stat. fluctuation
Fit:• K+K+
° K+K0
(Ec.m. s ) ~ 14m f0 ,
2
s
0 mxxei
mx2 s imxx
Abkg.
2
K+K+ K+K0
from K1(1270,1400)
decay
f0(980)
f0(980)
m(K+K) (GeV/c2) m(K+K) (GeV/c2)
m(
)
(G
eV/c
2 )
m(
)
(GeV
/c2 )
BABAR
Strangeness partner of Y(4260) ?
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 14
5 Hadrons: e+e
e+e KKKK
PRD 76 (2007) 092005
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 15
e+e First inclusive measurement of these states
4.300 events (20% bkg. on peak)30.000 events (20% bkg. on peak)
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 16
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture. non-ISRbackground
selectedevents
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
BABAR
BABAR
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
BABAR
Substructures e+e
Rich structure: clear peaks are visible- ~20% , mostly - ~40% , contains some f the rest is well described by and - then almost all -
and modes consistent withprevious measurements, better precision
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 17
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
non-ISRbackground
selectedevents
'
f1(1285)
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
'
BABARQuickTime™ and a
TIFF (Uncompressed) decompressorare needed to see this picture.
f
BABAR
Substructures e+e
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benötigt.
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Clear evidence for and f1(1285), both channels showing a stracture at ~2 GeV Is this the (2150), (2050) ?
single BW fits
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 18
3 Hadrons including 2 Kaons: e+e KKKK
e+e KKS
arXiv:0710.4451 submitted to PRD
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 19
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.QuickTime™ and a
TIFF (Uncompressed) decompressorare needed to see this picture.
e+e S
S
J/
J/
Features: • Dominant decay mode for the (1680)• Systematic errors 5% - 6%• Significant improvement over existing measurements from DM1, DM2
BABAR BABAR
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 20
Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“
benötigt.
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Dalitz plots for the S
Both Dalitz plots are dominated by the K*(890), some K2*(1430) also presentAllows to extract the isospin components (isoscalar, isovector) of the KK*(890) cross section (moduli and relative phase) Allows a description in terms of vector meson resonances without interferences
BABAR
BABAR
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 21
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Isospin components in K*(890)KA global fit in Ec.m. bins has been performed
Result: isoscalar and isovector channels are dominated by resonances Zur Anzeige wird der QuickTime™
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(1500)(1680)consistent with:
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 22
6 Hadrons: e+e 2(e+e
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 23
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 24
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 25
Baryons: _e+e pp
to appear in PRD
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26
23 cGeVm pp /
PRD 73, 012005 (2006)PRD 73, 012005 (2006)
ppS )2( ppS )2(ppJ / ppJ /
ModeMode BaBar BF BaBar BF PDG 06PDG 06
Jpp (2.22 ± 0.16)10-3 (2.17 0.08).10-3
(2S)pp (3.3 ± 0.9)10-4 (2.65 0.22).10-4
ppee ppee
section cross ppee
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 27
Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“
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Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“
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e+e
Continuation of the ISR-baryon program, which started with the measurement of the proton form factor in the time like region
Select events with p and p Add an additional photon for the candidatesPerform a kinematic fit with mass constraints and distinguish channels based on best 2
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 28
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Baryon (Effective) Form FactorsCross section parametrized by magnetic and electric form factors GM and GE =m2/4mB
2
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are needed to see this picture.
Effective FF:|GE|=|GM|
All FF‘s seemto have consistent behaviour
All FF‘s showingrising behaviour
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F in agreement withthe prev. measurem.(DM2) and with Fn
(FENICE)
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 29
- Can measure |GE/GM| by fitting the distribution of the cosine of helicity angle
Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“
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| GE / GM | for
|GE/GM| < 1.73+0.99-0.57
|GE/GM| < 0.71+0.66-0.71
Within large errors consistent with proton results
polarization tested by fitting the slope of the angle btw. the polarization axis and the proton momentum in the rest frame: -0.22 <P<0.28 @90% C.L.
tests a non-zero relative phase btw. GE and GM: 0.76 < sin< 0.98
Czyz, Grzelinska, Kühn: hep-ph/0702122
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 30
Conclusions
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 31
Conclusions
• Radiative Return physics continues to be a productive field beyond B-physics at BABAR
• Measurements are important to improve our theoretical understanding of (g-2) and (MZ)
• (Sub)Structures: growing impact in the field of hadron spectroscopy - New structures at low energies at M~2175, 1900, 2050, ... MeV - Y(4260) discovered in ISR-events - 26 J/ and 10 (2S) branching ratios measured, very competitive
• In future many new, improved studies planned - update current results - additional excl. channels under study, in particular e+e - inclusive measurements of R
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Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR 32
To calculate R only using BABAR data in the energy range <2 GeV the missing processes K+K-, KSKL, KSKLmust be measured.
Conclusions