Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR1 BABAR Results on Hadronic Cross Sections with Initial State Radiation (ISR) Peter A

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


Motivation&

ISR - Method


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)


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


• 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


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 }


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 !


4 Hadrons: e+e e+e e+e


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)


Substructures in e+e

intermediate state is also seen

, combine with meas. at 10.6 GeV f0 a1


(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


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


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) ?


5 Hadrons: e+e

e+e KKKK

PRD 76 (2007) 092005


e+e First inclusive measurement of these states

4.300 events (20% bkg. on peak)30.000 events (20% bkg. on peak)


QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture. non-ISRbackground

selectedevents


are needed to see this picture.

BABAR

BABAR



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




non-ISRbackground

selectedevents

'

f1(1285)



'

BABARQuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.

f

BABAR

Substructures e+e

Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“

benötigt.


benötigt.

Clear evidence for and f1(1285), both channels showing a stracture at ~2 GeV Is this the (2150), (2050) ?

single BW fits


3 Hadrons including 2 Kaons: e+e KKKK

e+e KKS

arXiv:0710.4451 submitted to PRD



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



benötigt.


benötigt.

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



benötigt.

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™

Dekompressor „TIFF (LZW)“ benötigt.


benötigt.

(1500)(1680)consistent with:


6 Hadrons: e+e 2(e+e




Baryons: _e+e pp

to appear in PRD

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



benötigt.


benötigt.

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



benötigt.

Baryon (Effective) Form FactorsCross section parametrized by magnetic and electric form factors GM and GE =m2/4mB

2



Effective FF:|GE|=|GM|

All FF‘s seemto have consistent behaviour

All FF‘s showingrising behaviour


benötigt.


benötigt.

F in agreement withthe prev. measurem.(DM2) and with Fn

(FENICE)


- Can measure |GE/GM| by fitting the distribution of the cosine of helicity angle


benötigt.

| 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


Conclusions


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


To calculate R only using BABAR data in the energy range <2 GeV the missing processes K+K-, KSKL, KSKLmust be measured.

Conclusions

Documents

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR1 BABAR Results on Hadronic Cross Sections with Initial State Radiation (ISR) Peter A