Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR1 BABAR Results on Hadronic Cross Sections with Initial State Radiation (ISR) Peter A. Lukin Budker Institute of Nuclear Physics, Russia for the BABAR collaboration Experimental Seminar Laboratori Nazionali di Frascati June 17, 2008

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR2 Motivation & ISR - Method

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR3 Motivation: High Precision Test of the Standard Model  Anomalous magnetic moment of the muon  Fine structure constant at Z 0 -mass  QED (M Z ) Muon-Anomaly a  = (g  -2)/2 =  a   a   a   a   a   theo QED had weak New physics Hadronic Vacuum Polarization 2nd largest contribution, pQCD not applicable Error of hadronic contribution dominates total error of a  ! µ+µ+  q q µ+µ+ Experimental input into dispersion integral K(s) = analytic kernel-function, above typically 2…5 GeV, use pQCD from S. Eidelman 22  1-2 GeV 2-5GeV >5GeV 22  1-2 GeV 2-5GeV >5GeV Central Values Uncertainties   Motivation: (g µ -2) and  (M Z )

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR4 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   )(s dM d M hadr Hadr  hadr   H(s) Master-Formula: Radiator-Function (NLO) MC-Generators EVA, Phokhara, AfkQed J. Kühn, H. Czyż, G. Rodrigo  s’ e-e- e+e+  ISR Hadrons M hadr  had [mbarn]  s [GeV] VEPP-2M BES  (4S) pQCD  s=10.6 GeV GAP: No recent data

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR5 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) Energies Features: Normalitzation: 1) Integr. Luminosity L int  Radiator Function H OR 2) Or better: use e + e -       events  s’ [GeV] 10 L BABAR = 232 fb -1 ISR Luminosity L ISR (pb -1 / 0.1 GeV) Hadrons  ISR L ISR = integrated luminosity in energy scan, corres- ponding to same statistics as the one in ISR method Large angle Bhabhas Theory 

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR6 First ISR Exclusive Hadronic Channels measurements 89 fb fb -1 } - e + e          - e + e   2(         K  K   2(K  K   - e + e   3(      3(        2(      K  K  - e + e   pp }

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR7 Many new Results since then.... all based on 232 fb -1 - e + e            K  K       K  K        - e + e   2(        2(         K  K        K  K   - e + e   K  K     K  K S    K  K S  - e + e    0  0,  0  0,  0  0 now available: ~500 fb -1 !

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR8 4 Hadrons: e + e           e + e           e + e          

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR9 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  e+e   BaBar preliminary  (1700)  (1450)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR10    Substructures in e + e             intermediate state is also seen    , combine with meas. at 10.6 GeV   f 0  a 1 

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR11 (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 B A B AR measurement at 10.6 GeV - The structure at 2050 MeV is the  (2050)?! Questions: New 4  MC (Czyz, Kühn, Wapienik) arXiv:0804:0359

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR12 e+e  e+e   Factor 2.5 more statistics with respect to published result Search for  (1020)f 0 (980) final state and relation to  (1020)  f 0 (980)  BR of J/  and  (2S) to  (1020)  Search for new states Motivation: K+K+K+K+ Systematic error 8% (was 15%) Error dominated by acceptance K+K0K+K0 First measurement ever ! Systematic error 11% B A B AR PRD-RC 74 (2006)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR13 Structure in e + e    f 0 (980) New state with J PC =1 - - with mass of GeV and 58 MeV width ? Toy MC gives <10 -3 probability for stat. fluctuation Fit: K + K   +   ° K + K   0   K+K+K+K+ K+K0K+K0  from K 1 (1270,1400)   decay  f 0 (980)  m(K + K  ) (GeV/c 2 ) m(     ) (GeV/c 2 ) m(     ) (GeV/c 2 ) B A B AR Strangeness partner of Y(4260) ?

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR14 5 Hadrons: e + e                       e + e   K  K         K  K        PRD 76 (2007)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR15 e + e                      First inclusive measurement of these states events (20% bkg. on peak) events (20% bkg. on peak)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR16 non-ISR background   selected events     B A B AR     B A B AR 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 with previous measurements, better precision

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR17 non-ISR background selected events '' f 1 (1285) '' B A B AR ff Substructures e + e            Clear evidence for  and f 1 (1285), both channels showing a stracture at ~2 GeV  Is this the  (2150),  (2050) ? single BW fits

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR18 3 Hadrons including 2 Kaons: e + e   K  K     K  K    e + e   K  K S     arXiv: submitted to PRD

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR19 e + e          S    S  J/  Features: Dominant decay mode for the  (1680) Systematic errors 5% - 6% Significant improvement over existing measurements from DM1, DM2 B A B AR

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR20 Dalitz plots for the        S  Both Dalitz plots are dominated by the K*(890), some K 2 *(1430) also present  Allows 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 B A B AR

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR21 Isospin components in K*(890)K A global fit in E c.m. bins has been performed Result: isoscalar and isovector channels are dominated by resonances  (1500)  (1680) consistent with:

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR22 6 Hadrons: e + e   2(         e + e       

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR23

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR24

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR25 Baryons: _ e + e                pp to appear in PRD

26 PRD 73, (2006) Mode BaBar BF PDG 06 J  p p (2.22 ± 0.16)  (2.17  0.08)  (2S)  p p (3.3 ± 0.9)  (2.65  0.22)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR27 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  candidates Perform a kinematic fit with  mass constraints and distinguish channels based on best  2

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR28 Baryon (Effective) Form Factors Cross section parametrized by magnetic and electric form factors G M and G E  =m 2 /4m B 2 Effective FF: |G E |=|G M | All FF‘s seem to have consistent behaviour All FF‘s showing rising behaviour F  in agreement with the prev. measurem. (DM2) and with F n (FENICE)

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR29 - Can measure |G E /G M | by fitting the distribution of the cosine of helicity angle | G E / G M | for     |G E /G M | < |G E /G M | < 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: <P  C.L.  tests a non-zero relative phase btw. G E and G M :  0.76 < sin  < 0.98 Czyz, Grzelinska, Kühn: hep-ph/

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR30 Conclusions

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR31 Conclusions Radiative Return physics continues to be a productive field beyond B-physics at B A B AR Measurements are important to improve our theoretical understanding of (g-2)  and  (M Z ) (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

Peter A. Lukin BABAR Results on Hadronic Cross Sections with ISR32 To calculate R only using B A B AR data in the energy range <2 GeV the missing processes                  K + K -, K S K L, K S K L   must be measured. Conclusions