Vacuum Polarization and the impact of BaBar data Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay QWG Workshop 2007 October 17 - 20, 2007, DESY hadrons [email protected].
Download ReportTranscript Vacuum Polarization and the impact of BaBar data Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay QWG Workshop 2007 October 17 - 20, 2007, DESY hadrons [email protected].
Vacuum Polarization and the impact of BaBar data Michel Davier Laboratoire de l’Accélérateur Linéaire, Orsay QWG Workshop 2007 October 17 - 20, 2007, DESY hadrons [email protected] 1 Essentials of Hadronic Vacuum Polarization vacuum polarization modifies the interacting electron charge (s ) (0) 1 (s ) with: (s ) 4 Re (s ) (0) photon vacuum polarization function (q2) Leptonic lep(s) calculable in QED. However, quark loops are modified by long-distance hadronic physics, cannot (yet) be calculated within QCD (!) Born: (0) (s ) (s ) / (s ) Way out: Optical theorem (unitarity) ... ... and subtracted dispersion relation for (q2) (analyticity) 0 [eehadrons()] 12 Im (s) R(s) pt ] | Im[ Im (s) (s ) (0) ds 0 s(s s ) i s ... and equivalently for a [had] 2 hadrons |2 s R(s) had (s ) Re ds 3 s(s s ) i 0 had a 2 3 2 4 m2 ds K (s ) s R (s ) 2 The Muonic (g –2) The Situation 1995 Contributions to the Standard Model (SM) Prediction: g 2 a 2 aQED Source (a) Reference QED ~ 0.1 10–10 [Schwinger ’48 &others (Kinoshita)] Hadrons ~ (154 3.5) 10–10 [Eidelman-Jegerlehner ’95 & others] Z, W exchange ~ 0.2 10–10 [Czarnecki et al. ‘95 & others] ahad 3 2 2 ds 4 m2 K (s ) s R (s ) ahad aweak Dominant uncertainty from lowest order hadronic piece. Cannot be calculated from QCD (“first principles”) – but: we can use experiment (!) h a d ”Dispersion relation“ had ... 3 Contributions to the dispersion integral 2 3 (+,) 4 > 4 (+KK) 1.8 - 3.7 3.7 - 5 (+J/, ) 5 - 12 (+) 12 - < 1.8 GeV ahad,LO 12% 5% 5% 2% 1% 3% 2 72% 92% 0% 2[ahad,LO] 1% 9% 4% 0% 0% 0% 6% 2 80% 92% 4 Improved Determinations of the Hadronic Contribution to (g –2) and (MZ 2) Eidelman-Jegerlehner’95, Z.Phys. C67 (1995) 585 Since then: Improved determination of the dispersion integral: better data extended use of QCD Energy [GeV] Input 1995 Input after 1998 2m - 1.8 Data Data (e+e– & ) (+ QCD) 1.8 – J/ Data QCD J/ - Data Data + QCD - 40 Data QCD 40 - QCD QCD Improvement in 4 Steps: Inclusion of precise data using SU(2) (CVC) Alemany-Davier-Höcker’97, Narison’01, Trocóniz-Ynduráin’01, + later works Extended use of (dominantly) perturbative QCD Martin-Zeppenfeld’95, Davier-Höcker’97, Kühn-Steinhauser’98, Erler’98, + others Theoretical constraints from QCD sum rules and use of Adler function Groote-Körner-Schilcher-Nasrallah’98, Davier-Höcker’98, Martin-OuthwaiteRyskin’00, Cvetič-Lee-Schmidt’01, Jegerlehner et al’00, Dorokhov’04 + others Better data for the e+e– + – cross section and multihadron channels CMD-2’02 (revised 03), KLOE’04, SND’05 (revised 06), CMD-2’06, BaBar’04-06 5 Goals of the BaBar ISR Program Precise measurements of cross section for all significant processes, e+e hadrons, from threshold to ~4-5GeV Measure , KK channels with high precision Summing up exclusive cross sections ==>Improve the precision of R Study spectroscopy of JPC=1−− states and their decays M. Davier et al., 2003 0 (e e hadrons( )) R( s ) pt (e e ) s 6 Exclusive Channels with BaBar ISR • systematic program underway using ISR from (4S) energies, taking advantage of high luminosity (B-factory) • statistics comparable to CMD-2/SND for Ecm<1.4 GeV, much better than DM1/DM2 above • full energy range covered at the same time • channels identified using particle ID and kinematic fitting • systematic uncertainties at 5-10% level • large acceptance for hadronic system (boosted opposite to ISR photon) ISR X = 2E /Ecm d (s, x ) H (s, x, ) 0 (s (1 x )) dxd (cos ) 2E 2 2x x 2 x 2 H (s, x, ) , x x sin2 2 s H is radiation function 7 BaBar ISR: e+ehadrons Reactions for which results have been published : pp PRD 73, 012005 (2006) 0 PRD 70, 072004 (2004) 22, K+K- , PRD 71, 052001 (2005) K+K- K+K- 00 , 2K+2KPRD 76, 012008 (2007) 33, 2200, K+K-22 PRD 73, 052003 (2006) New results presented last Summer : K+K0, KSK, K+Kh, LL , LS0 , S0S0 BaBar Preliminary submitted to PRD e-Print: arXiv:0709.1988 [hep-ex] 00 BaBar Preliminary 0 0 2 2 ,2 2 h, KK , KK h accepted by PRD e-Print: arXiv:0708.2461 [hep-ex] Work in progress on : , K+K, 30 Inclusive R 8 BaBar ISR: 0 errors include systematics SND huge discrepancy with DM2 BaBar DM2 contribution to ahad (1.05-1.8 GeV) : • all before BaBar 2.45 0.26 0.03 • all + BaBar 2.79 0.19 0.01 • all – DM2 + BaBar 3.25 0.09 0.01 x1010 9 BaBar ISR: 22 contribution to ahad (<1.8 GeV) : • all before BaBar 14.20 0.87 0.24 • all + BaBar 13.09 0.44 0.00 x1010 10 BaBar ISR: 33 BaBar contribution to ahad (<1.8 GeV) : • all before BaBar 0.10 0.10 • all + BaBar 0.108 0.016 x1010 11 BaBar ISR: 2220 BaBar contribution to ahad (<1.8 GeV) : • all before BaBar 1.42 0.30 0.03 • all + BaBar 0.890 0.093 x1010 12 BaBar ISR: + 0 0 Only statistical errors plotted BaBar preliminary ψ ->00J/ψ(->) J/ψ •Previous situation chaotic •Preliminary syst. error: 8% in peak 5% •Good agreement with SND <1.4 GeV •Huge improvement >1.4 GeV •First measurement >2.5 GeV 13 BaBar ISR: +00 --substructure BaBar preliminary MC Intermediate states: 0 large and first seen 0 f0980 a11260 14 BaBar ISR: ++0 Cross sections of submode: h h0 X = 3 0 3 : from subtraction /h h0 3 15 BaBar ISR: BaBar preliminary BaBar,3 BaBar preliminary f0(980) 1st measurement BaBar,3 1.35 0.03 0.45 0.14 1.66 0.01 0.22 0.04 16 BaBar ISR: h • ~4,300 events selected • first measurement BaBar preliminary 17 BaBar ISR: KSK , KK0 KSK-+ K K and K 0 K 0 Dominant states: K*(980)K and K2*(1430)K K+K-0 Isoscalar channel dominates over isovector Parameters (1680): PDG m=172320 MeV, 168020 = 37175 MeV, 15050 ee= 58060 eV, Bh/BK*K 1/3 18 BaBar ISR: KK , KK00 K+K-+ - Substructure in the final state K*(892) - 1 per event K+K-0 0 K+K-0 0 K1(1270),K1(1400) – 1+ K+K-+ - ~ 1500 19 BaBar ISR:KKKK,KK0,KKh K K K K K+K- dominated J/Y KK0 KKh First measurement ! 20 BaBar ISR: KK Cross section Substructures K*0(892) first measurement J/ 21 Present BaBar Measurements only statistical errors syst. 5-10% to obtain R in the energy range 1-2 GeV the processes , 30, 40, K+K-, KSKL, KSKL, KSK+ 0 remain to be measured 22 Evaluating the Dispersion Integral use data use QCD Agreement between Data (BES) and pQCD (within correlated systematic errors) use QCD Better agreement between exclusive and inclusive (2) data than in 19971998 analyses 23 Update for ICHEP-Tau06 ahad [ee] = (690.9 ± 4.4) 10 –10 a [ee] = (11 659 180.5 ± 4.4had ± 3.5LBL ± 0.2QED+EW) 10 –10 including: Hadronic HO – ( 9.8 ± 0.1) 10 –10 Hadronic LBL + (12.0 ± 3.5) 10 –10 Electroweak QED (15.4 ± 0.2) 10 –10 (11 658 471.9 ± 0.1) 10 –10 Knecht-Nyffeler, Phys.Rev.Lett. 88 (2002) 071802 Melnikov-Vainshtein, hep-ph/0312226 Davier-Marciano, Ann. Rev. Nucl. Part. Sc. (2004) Kinoshita-Nio (2006) BNL E821 (2004): aexp = (11 659 208.0 6.3) 10 10 Observed Difference with Experiment (DEHZ) a [exp] – a [SM] = (27.5 ± 8.4) 10 –10 3.3 „standard deviations“ 24 Conclusions and Outlook Hadronic vacuum polarization is still the dominant systematics for SM prediction of the muon g – 2 Significant step in precision from new experimental input CMD-2 + SND for 2 BaBar for multipion channels Precision of SM prediction (5.6) now exceeds experimental precision (6.3) SM prediction for a differs by 3.3 [e+e – ] from experiment (BNL 2004) In the next months many new results expected KLOE 2 (different analyses) BaBar 2, 2K, remaining multihadrons in 1-2 GeV range VEPP-2000 in the longer run vacuum polarization calculations in line for the next challenges new g-2 measurements precision EW measurements (Tevatron, LHC, ILC) 25