1 / 36

BABAR Risultati di Fisica con i primi 100 fb -1

BABAR Risultati di Fisica con i primi 100 fb -1. Stefano Passaggio INFN – Sezione di Genova. Gruppo I 16-21 Settembre 2002. Daily luminosity. Integrated luminosity. design. PEP-II performance. Highest inst. luminosity reached so far: 4.602x10 33 cm -2 sec -1

ziarre
Download Presentation

BABAR Risultati di Fisica con i primi 100 fb -1

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. BABARRisultati di Fisica con i primi 100 fb-1 Stefano Passaggio INFN – Sezione di Genova Gruppo I 16-21 Settembre 2002

  2. Daily luminosity Integrated luminosity design PEP-II performance • Highest inst. luminosity reached so far: 4.602x1033 cm-2 sec-1 • Design: 3x1033 cm-2 sec-1 ~88 million BB pairs recorded Off-peak S.Passaggio

  3. Selection of BaBar experimental results “Io non posso ritrar di tutti a pienoperò che sì mi caccia il lungo temache molte volte al fatto il dir vien meno.” un poeta del ’300… • Choice criteria • recent results (summer conferences) • future perspectives • Organization • time dependent CP asymmetries (sin2, sin2) • time independent (direct) CP asymmetries (charmless 2-body, DK) • other excerpts from BaBar @ ICHEP 2002 • (older) non-CP B physics (BR’s, lifetimes, oscillations) S.Passaggio

  4. Time dependent CP asymmetries Direct CP violation. Need more than one amplitude with different weak and strong phases. Cf Sf Interference between mixing and decay. (a,b,g) measurement Exclusive B Meson Reconstruction Coherent B-antiB pair B FlavorTagging S.Passaggio

  5. R.Faccini sin2 • Golden modes: SM  all amplitudes have the same weak phase CP = -1 CP = +1 CP = 0.65 CP odd fraction (L=1) measured: (hc KsK+p-andhc K+K-p0) hchas been added to the sample S.Passaggio

  6. sin2 golden modes(contd) CP=-1 CP=+1 Winter02 was 0.09 sin2 = 0.755  0.074 sin2 = 0.723 0.158 sin2b = 0.741  0.067 (stat)  0.033 (syst) Submitted to PRL, hep-ex/0207042 S.Passaggio Winter02 was 0.04

  7. sin2 golden modes(contd) Constraining , Look for direct CP (BSM) • No direct CP violation in thesemodes within SM • Leave  free and fit for || andSf • Use only |l| = 0.948  0.051(stat)  0.029 (syst) sin2 measurement is now really constraining the apex position! Sf = 0.759  0.074 (stat) No direct CP observed S.Passaggio

  8. Analysis improvements •  s(sin2b) ICHEP00 Still improving faster than statistics Winter 01 LP01 Improved track efficiency and vertex resolution Re-optimized selection criteria Improved effective tagging efficiency (Q: 26.0 28.1) New channel added (cKS) Winter 02  S.Passaggio

  9. If no penguin contribution: Trieste sin2 with D*+D*- • Theoretically uncertain penguin contributions (predicted to be small) • D*+D*- is a mixture of different CP eigenstates (L=0,1,2) • Transversity analysis to determine the CP odd fraction • Measurethe CP even parameters: R=0.07 0.06  0.03 Im(l+) = 0.31  0.43 (stat)  0.13 (syst) |l+| = 0.98  0.25 (stat)  0.09 (syst) ICHEP 02 contributed paper, preliminary Fixing and and refitting the change in likelihood corresponds to 2.7  Needs more statistics to conclude S.Passaggio

  10. Other sin2 results • B0  J/ p0 • Again: • If no penguin measures sin2 • Tree and penguin should have the same order of magnitude • BR(B0  J/ p0) = (2.0  0.6  0.2) 10-5 • S(J/ p0) = 0.05  0.49(stat)  0.16(syst) • C(J/ p0) = 0.38  0.41(stat)  0.09(syst) • B0   KS • Pure penguin (tree highly suppressed) • Within SM measures sin2 • New physics may show up through loop diagrams • BR(B0 KS) = (8.1+3.1-2.5  0.8) 10-6 • sin2 = -0.19+0.52-0.50(stat) 0.09(syst) (assuming ||=1) ICHEP 02,preliminary ICHEP 02,prelim. Still statistically limited… adding also Belle: 2.7  S.Passaggio

  11. Roma sin2: B0+- • Experimentally, one measures eff  , due to non negligible penguin contributions P T + Effect of penguin contributions Need BR’s for +-, 0, 00 to get  from eff Roma, Torino Isospin analysis S.Passaggio

  12. B0p+ p - Kp B0+-: time dependent analysis • mES and E S, C unbinned max likelihood fit qq + K S.Passaggio

  13. Roma, Torino Milano Direct CP violation Interference between diagrams with different strong (i) and weak phases(i) Large asymmetries possible in B+/0 decays Diagrams from New Physics can contribute (but hard to extract CKM phases) At the edge of discovery in somechannels More statistics needed Napoli S.Passaggio

  14. B-D0(CP)K- (direct CP) Pisa • B- D0K- B D0CPK • Measurement of B- D0K-, D0  K-+,K-++-, K-+0 (non-CP eigenstates) • Measurement of B D0CPK,D0CP K+K- (CP-even) key ingredients for theoretically clean methods of measuring the angle  No evidence of direct CP violation yet S.Passaggio

  15. preliminary BABAR inclusive Other excerpts ofBaBar @ ICHEP 2002 • InclusiveElectron Spectrum in Charmless Semileptonic B Decays near endpoint • Charmless Exclusive Semileptonic B Decays ( ) preliminary S.Passaggio

  16. BaBar @ ICHEP 2002 • Measurement of BR for Inclusive Semileptonic B Decays events tagged by the presence of a high momentum electron(p* = 1.4  2.3 GeV/c) A second electron in the event is taken as the signal lepton(require p*  0.6 GeV/c to avoid large backgrounds) Opposite sign: primary B decaysSame sign: predominantly secondary charm decays S.Passaggio

  17. BaBar @ ICHEP 2002 Pisa • Determination of BR for Inclusive Decays • Using a Sum ofExclusive modes • NLO prediction within SM (10%) consistent with SM • BSM contributions to loop  observable deviations • quark-hadron duality: • fully inclusive approach to reduce model dependence to access the parton level process • bkg reduced by looking at other B • fully reconstruct 12 exclusive decay modes • use MX to measure the E spectrum • 1st moment of E spectrum • fit of MX spectrum • also constrain S.Passaggio

  18. Roma BaBar @ ICHEP 2002 • The study of the time evolution of: • (~A2) • (~A4: CKM suppressed) provides a theoretically clean measurement of • This measurement requires a knowledge of the ratio D between the decay amplitudes of these two processes • cannot be obtained from a direct measurement (large background from the CKM allowed process) • SU(3) symmetry (in naïve factorization model & if annihilations are negligible) BF (B0 D-(*) p+) fDs2 BF (B0 Ds+(*) p-) l2Dp fD2 tg2qC need to measure these BR BF (B0 Ds(*) K): allows to check that the annihilation is small S.Passaggio

  19. DS+p- Roma BaBar @ ICHEP 2002 Results on 84 Million B Pairs: (B0  DS+-) = [3.2  0.9  1.0]  10-5 3.3s significance (B0  DS-K+) = [3.2  1.0  1.0]  10-5 3.5s significance (B0  DS*+ -) < 4.1  10-5 (B0  DS*-K+) < 2.5  10-5 @90% C.L. DS*+p- DS-K+ DS*-K+ |l|~0.020±0.004(stat.+sys.) (theoretical error due to SU(3) breaking ~30%) S.Passaggio

  20. cc0  p+p– cc0  K+K– BaBar @ ICHEP 2002 Genova • In the framework of naïve factorization, the decay B c0K is forbidden when the assumption is made that the process occurs through the production of a “color singlet” cc pair. If a “color-octet” term is included, then the BR is expected to be of the same order of magnitude as BR(B±  c1K±) = (6.5 ± 1.1)  10–4. • The cc0 is reconstructed in the two decay modescc0 +–cc0  K+K– • The signal yield is separated from combinatorial and “peaking” background (i.e. from other B decays with the same final state) by means of an UML fit to the +– (K+K–) invariant mass distribution. • Combined result for ∫L = 70 fb–1:B(B± cc0 K±) = (2.4 ± 0.7)  10–4 S.Passaggio

  21. Bari BaBar @ ICHEP 2002 Charm physics: D0 decays Dalitz plot analysis of 3-body D0 decays Look for intermediate resonances that contribute to the 3-body final states Extract fractions and relative phases of intermediate resonant states S.Passaggio

  22. B0/B± lifetime BaBar has published two measurements of the B meson lifetimes • Using one fully reconstructed B meson hadronic decay(PRL 87(2001)202803) 23 106 BB pairs • Using partially reconstructed(PRL 89(2002)011802) 23 106 BB pairs • Use only the slow ± from (low Q  sgives D* flight dir) • Oppositely charged pairs give signal, same sign pairs give bkg • (low Q  neglect B momentum) • Other B decay position from a selection of remaining tracks Padova Brec S.Passaggio

  23. 91700 evts sig fi(B+), fi(cont), fi(BB) most precise measurement of (B0) Padova B0 lifetime (contd) Crucial: modeling of t resolution function for signal and background S.Passaggio

  24. opposite sign same sign asymmetry Ferrara,Roma Measurement of md • Select events containing 2 leptons from semileptonic B decays • B0 flavor at decay tagged by sign of lepton charge • l+l- unmixed events (+); ll  mixed events (-) • in a coherent P-wave state  • time dependent asymmetry: Dmd=0.493±0.012±0.009 ps-1 Mixing measurements validate time-dependent asymmetry measurement techniques. S.Passaggio

  25. The next future… Ferrara, Napoli, Roma • Physics on the recoil The high luminosity and the high number of fully reconstructed B’s opens a brand new world in B physics • In 80 fb-1 : • 300 Kfully reco B • 40 K semileptonic B (one  missing) • Able to reconstruct single B in modes with BF ~10-4 - 10-5 S.Passaggio

  26. Physics on the recoil: 100 fb-1 S.Passaggio

  27. Physics on the recoil • Vcb Inclusive Semileptonic spectrum • Vub Analysis on the recoil (with full reconstruction of the hadronic system) will yield a statistical error of 10% and a comparable systematic error by end of the year • b  s • B   results expected for the winter conferences Ferrara, Roma (Inclusive) Pisa, Roma (Measure fB) Napoli S.Passaggio

  28. Ferrara, Napoli, Trieste Pisa Genova Frascati Frascati, Perugia Other ongoing analyses • Vcb D(*)l (D(*)fully reconstructed), dN/dy differential distributionresults expected by winter conferences • CP/CPT measurement of the lifetime difference and test of CPT and T violation in the B0d meson system • Hadronic charmonium decays search for unconfirmed charmonium states (hc) • ISR to excl. final states (2n, KK, …) • BR(DS) S.Passaggio

  29. New physics? (will see…) physics on recoil Conclusions CP violation in B physicsis now an established fact • sin2 (golden) = 0.741  0.067 (stat)  0.033 (syst) • D*+ D*-: Im(l+) = 0.31  0.43 (stat)  0.13 (syst) (2.7 : penguin?) •  KS: sin2 = -0.19+0.52-0.50(stat) 0.09(syst) (BaBar+Belle: 2.7 ) • S = 0.02  0.34stat  0.05systC = -0.30  0.25stat  0.04syst • Time is ripe for observing smaller effects(direct CP, …) • Exploit high luminosity to attack the systematics Isospin analysis has started… S.Passaggio

  30. Backup slides

  31. PEP-II @ SLAC High luminosity asymmetric B factory @ (4S) 9 GeV e- on 3.1 GeV e+ (4S) boost:<bg>  0.55 S.Passaggio

  32. CsI(Tl)EMC 1.5Tsolenoid • e ID • reconstruction Bremsstrahlung recovery DIRC (PID) E/E = 2.3% E-1/4  1.9% e+ (3.1GeV) High quality tracking (fiducial volume: 041 <  < 2.54) DriftChamber e- (9GeV) (pT)/pT = 0.13% PT 0.45% InstrumentedFluxReturn SiliconVertexTracker  ID The BaBar detector z hit resolution ~ 15 m S.Passaggio

  33. CP CP violation with B mesons Three observable interference effects: • CP violation in mixing: • CP violation in decay (direct): • CP violation from mixing/decay interference: (independent from phase conventions) mixing decay S.Passaggio

  34. Generalities on reconstruction • Kinematic variables used for signal and background estimates (fully reconstructed B’s) • From z to t: • Lepton ID: e EEMC/pDCH; lateral shower shape (EMC); dE/dx (DCH)   EEMC; penetr. depth, strip mult., track continuity (IFR) • /K separation: (when applied) based on dE/dx (DCH), Čerenkov ring opening (DIRC) • Continuum rejection: typically based on upper cut on normalized Fox-Wolfram 2nd moment (H2/H0  0.4  0.95) nominal Y(4S) boost in lab frame proper time difference between the 2 B decays S.Passaggio

  35. p-K separation K sample p hypothesis K hypothesis D*+ D0+  (K-+)+ For e=85% P(Kp)=1.7% P(p K)=2.7% S.Passaggio

  36. p+p- asymmetry [Belle – BaBar] S.Passaggio

More Related