1 / 25

Studies of e+e- -> Hadron Reactions Using Initial State Radiation at BaBar

This study presents the results from the Hadron-07 conference on the exclusive e+e- -> hadron reactions with baryons or strange particles. The study focuses on the production of baryon pairs and kaon pairs, as well as the form factors and cross sections of various particles. The use of initial state radiation (ISR) allows for effective measurements of cross sections in a wide energy range.

cathyk
Download Presentation

Studies of e+e- -> Hadron Reactions Using Initial State Radiation at BaBar

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Studies of Exclusive e+e- --> Hadrons Reactions With Baryons or Strange Particles Using Initial State Radiation at BaBar Sergey Serednyakov Budker Institute of Nuclear Physics, Novosibirsk, Russia (Babar, SND) October 8-13, 2007 Hadron-07

  2. Outline • 1 Introduction (list of processes, ISR method) • 2 Baryon pairs production ISR data • 3 SU(3) and QCD tests for baryon form factors • Kaon pairs production data • Strange contribution into R • 5 Conclusions Hadron-07

  3. List of processes, Babar, DL=230 fb-1 • Baryon data • 1 e+e- -> pp, • e+e- -> LL , SS, LS • KK data • 3 e+e- -> KKp, KKh • 4 e+e- -> KK 2p • 5 e+e- -> KK 3p • 6 e+e- -> KK 4p _ _ _ _ _ _ _ _ _ _ All reactions, except e+->ppbar, are with strange quarks in final state. Hadron-07

  4. ISR approach ISR – Initial State Radiation or Radiative Return e+e- -> p pbar g H is radiation function LISR ~ 0.3% LBabar , with LBabar ~ 1 ab-1, we have LISR ~ 3 fb-1 for x ~ 1! ISR approach is effective to measure cross sections changing in wide energy range, because the ISR luminosity is proportional to the energy range. For this reason, it is less effective for narrow resonance study Hadron-07

  5. Baryon Form factors Differential cross section: Total cross section: • the ratio of real cross section • to pointlike cross section Effective form factor: Two measurable values: 1 – effective FF, 2 – GE/GM At the threshold s=4mB2 -> |GE| = |GM| Nonzero phase f between complex form factors GEandGM leads to transverse polarization z of outgoing baryons: |z| ~ a sinf, a~0-0.5 Hadron-07

  6. - e+e- -> pp ,Babar data Phys.Rev.D 73 012005 2006 Cross section Eff. form factor 2.15 2.9 Ratio GE/GM Cosq What is new: 1 – GE/GM > 1 2 – a structure at 2.15 and 2.9 GeV/c2, Hadron-07

  7. - e+e- -> L L , Babar data ArXiv:0709.1988v1 [hep-ex]   p - LL cross section L eff. form factor Cosq GE/GM ~1 Hadron-07

  8. - L polarization in e+e- -> L L process, Babar data ArXiv:0709.1988v1 [hep-ex] Data Results: MC -0.22 < f < 0.28 Under |GE|=|GM| assumption -0.76 < sin  < 0.98 Conclusions: 1 – the transverse polarization of Ls is not seen, 2 – this measurement is not sensitive to the phase between GE and GM Hadron-07

  9. - - - e+e- ->S0 S0,L0 S0 (L0 S0 ), Babar data ArXiv:0709.1988v1 [hep-ex] So -> Lg, L -> p p, Eg > 30 MeV, LLgggkinematic fit 0 ,   p-  fit SLform factor S form factor Hadron-07

  10. SU(3) for baryon form factors For uds baryons: 3 X 3 = 8 + 8 +10 +1 S>>2MB2 SU(3) predictions: SU(3) test with Babar FF data: Conclusions: 1 – S0/L FF ratio agrees with SU(3) 2 – SL/L FF ratio disagrees with SU(3) Hadron-07

  11. Proton form factor vs transfer momentum QCD fit for proton FF data 2.15 Asymptotic fit for baryons FFs 2.9 JETP Lett. 25 510 (1977) Hadron-07

  12. Baryons form factors vs transfer momentum, Babar data S L SL Conclusion: close to the threshold the FF slope of L, S and SL is close to m-8, that is steeper than m-4inQCDasymptotics Hadron-07

  13. A comparison between neutron and doubled L form factor data In SU(3): Fn=2FL A comparison between proton and L form factors (Babar data) Prediction/p=-0.24 V.Chernyak prediction for asymptotic form factors: /p=-0.24, 0/p=0.29, 0/p=0.54, n/p=-0.47 Z.Ph. C42 569 (1989) Hadron-07

  14. e+e- ->K+K-p, KSK-++-, Babar preliminary data KSK-++- Dominant states: K*(980)K and K2*(1430)K K+K-p Isoscalar channel dominates over isovector Parameters(1680): PDG m=172320 MeV, 168020  = 37175 MeV, 15050 ee= 58060 ev, B/BK*K 1/3 Hadron-07

  15. e+e- ->η, 0 , Babar preliminary data 0 η 1.7 f ’’(2.15) e+e-→ 0 is suitable for search of exotic isovector resonances because of OZI suppression. e+e-→  is good channel for study of excited -state.dominates in KK. General fit to , 0, K*(980)K data gives parameters of excited vector mesons r’ , r’’, r’’’, j’ , j’’ . Hadron-07

  16. e+e- ->K+K-p+ p-, K+K-0 p0, Babar data Phys.Rev.D 76 012008 2007 K+K-p+p- Substructure in the final state K*(892) - 1 per event K+K-0p0 K+K-0 p0 K1(1270),K1(1400) – 1+ K+K-p+p- ~ 1500 Hadron-07

  17. Phys.Rev.D 76 012008 2007 Evidence of 1-- X (2175) state, Babar e+e- → jf0(980) j -> K+K-, f0-> p+p-, p0p0 e+e-> K+K-f0 f0 ->p0p0 2.15 (6s) 2.4 Possible nature of X(2150): 1 – ssss, 2 –j ’’, 3- X(2150) is similar to Y(4260): Y(4260) = J/Y f0, Gee=5.5 eV X(2150)= j f0, Gee=2.5 eV M=2175±18 MeV =58±25 MeV Bjf0Gee = =2.5+-0.8+-0.4 eV Hadron-07

  18. e+e- ->K+K-K+ K- , Babar data Phys.Rev.D 76 012008 2007 jK+K-domination J/Y 1.02 ~1.5 ~1.7 ~2 First measurement ! Hadron-07

  19. e+e- -> K+K-+p-p, K+K-+p-,Babar data Submitt. to Phys.Rev.D K+K-+p-p K+K-+p- K+K- ~2.0  j w h Hadron-07

  20. e+e- -> K+K-+p-p+p- , Babar data Phys.Rev.D 73 052003 2006 Cross section Substructures K*0(892) j J/y First measurement ! Hadron-07

  21. Contribution ofstrangenessinto Rfrom processes e+eKK+x, BSBS _ _ R(s) is one of the most fundamental quantities in high energy physics: (g-2)m, aem(mZ2), … R = 3 S e2q(1+aS/p), q=u,d,s, -> R=2 RS~1/3 (~17% of hadronic contribution) A comparison of measured and expected strangeness production cross section: Ecm, GeV 2.53 smm,nb 14 9.6 ss,nb(await.) 5 3.5 ss,nb,(this work) 3.3 2.1 Some of not measured channels: KSKLpp, K+KSpp, jhp, KK5p, .. Conclusion: the studied processes give ~60% of full expected strangeness production in e+e- collisions at Ec.m.~3GeV. This is about 10% of total hadronic cross section. (Syst.err. ~5%) Hadron-07

  22. Conclusions • The ISR approach is applied to PEP-II B-factory data to measure • the e+e- annihilation cross section at much lower energy. • The studied c.m. energy range is from threshold up to ~ 5 GeV, • the ISR equivalent luminosity is ~ 1 fb-1. • The proton, L, S and LS electromagnetic timelike form factors • are measured for the first time or more accurately than before. • For proton the GE/GM ratio is found >1 and a structure at • 2.15 and 2.9 GeV is seen. The QCD and SU(3) test for • the new baryon FF data in the non asymptotic region • give controversial results. • 4. The e+e- processes with pair of kaons in final state are measured • with accuracy better than before or for the first time. • A new KKpp state with mass ~2175 GeV and width ~60 GeV, • possibly j// , is seen. • 6. The strange contribution into total e+e- hadronic cross section • is estimated using new data. For 2E~3 GeV the contribution • is about 10%. Hadron-07

  23. After conclusions Hadron-07

  24. Future neutron form factor experiment e+e- -> n nbar, direct production (not ISR), VEPP-2000, Novosibirsk 2E=2Mn – 2 GeV (1.88 – 2), Nexpected ~ 105events, ~100 energy points VEPP2000 16.07.07 Neutron-antineutron event Hadron-07

  25. - e+e- -> K K , Novosibirsk, Orsay data e+e-KSKL , hep-ex 060657 (2006) e+e-K+K- , arXiv:0707.2279 [hep-ex] K+K- KSKL Systematic error ≈5-10% Babar data coming soon ! Hadron-07

More Related