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Charmonium Production at BaBar

Charmonium Production at BaBar. Jamie Boyd University of Bristol. On behalf of the Collaboration. Photon 2003, Frascati 7 th -11 th April 2003. BaBar detector & PEP-II performance  c measurements in 2 photon events Measurement of the  c width Observation of  c (2S)

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Charmonium Production at BaBar

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  1. Charmonium Production at BaBar Jamie Boyd University of Bristol On behalf of the Collaboration Photon 2003, Frascati 7th-11th April 2003

  2. BaBar detector & PEP-II performance c measurements in 2 photon events Measurement of the c width Observation of c(2S) J/ production using ISR events Measurement of the J/ total width Understanding J/y production in B decays as a test of non-relativistic QCD: Branching fractions: B+  J/yp L and B0  J/yp p Summary of new exclusive B decays to charmonium Overview Preliminary Result! All of the above analyses represent new or newly updated results J. Boyd - Photon 2003

  3. BaBar Detector Detector of Internally Reflected Cherenkov light 1.5Tsolenoid InstrumentedFluxReturn Identifies muons and neutral hadrons Identifies particles by their Cherenkov radiation K- separation>3.4 for P<3.5GeV/c e+ (3.1GeV) e- (9GeV) SiliconVertexTracker Measures origin of charged particle Trajectories + dE/dx 97% efficiency ElectroMagnetic Calorimeter DriftCHamber Measures energy of electrons and photons (E)/E=1.33%E-1/42.1% Measures momentum of charged particles + dE/dx (pT)/PT=0.13%PT0.45% J. Boyd - Photon 2003

  4. PEP-II Performance PEP-II has provided 100fb-1 to date exceeding design specifications Integrated Luminosity Daily luminosity J. Boyd - Photon 2003

  5. c production in 2 events • c lowest lying charmonium state • c width poorly determined • New Babar result using 1715 ± 70 signal events • Use J/ ISR events as cross check of the detector resolution model • Don’t detect the electrons + - J. Boyd - Photon 2003

  6. J/: Gaussian c: Gaussian Breit-Wigner Bkg.: Exponential from MC c production in 2 events - Analysis strategy c J/ Spectrum fitted with: Free parameters: J. Boyd - Photon 2003

  7. c width c mass c production in 2 events - Results MeV/c2 MeV/c2 Dominant Syst errors: for Mc uncertainty on mass scale for c uncertainty in background parameterization (0.7MeV/c2) J. Boyd - Photon 2003

  8. l c production in 2 events - c(2S) BaBar preliminary results: Theory: Ebert et al., Phys. Rev. D62, 034014 (2000) Eichten, Quigg, Phys. Rev. D49,5845 (1994) Lahde, Riska, hep-ph/0112131 Belle: (in excl. B decays): Crystal Ball: (in (2s) decays) J. Boyd - Photon 2003

  9. J/ production in ISR events • Study ISR e+ e- ->  +- events in the +- mass range around the J/ mass (2.8 – 3.2GeV/c2) • Fit to the J/ mass spectrum to measure J/ parameters • ~10% of ISR events have a photon which falls in the detector acceptance • High statistics due to large luminosity so fully reconstruct both muons and photon • Event selection • E*>3GeV • Muon ID E(EMC)<0.4GeV, p>0.5GeV/c • Kinematic cuts |Etotal-Ebeams|<1.5GeV, <0.07rad • 1C Kinematic fit – mass of the recoil against the di-muon system constrained to be 0 (photon hypothesis) J. Boyd - Photon 2003

  10. J/y production in ISR events – Method Probability that ISR photon has energy fraction x In ISR Integrating and adding in J/ lineshape: Measuring total cross section gives: Substituting in PDG values for B and Bee allows measurement of ee and tot J. Boyd - Photon 2003

  11. J/y production in ISR events - Method Fit the di-muon mass spectrum with: 2nd order polynomial (from simulation) J/ lineshape (from simulation) convoluted with Gaussian (detector resolution) main fit parameter K corrects for FSR Processes = 1.110.01 (from simulation) Obtain total cross section from R Efficiency systematics cancel in this ratio J. Boyd - Photon 2003

  12. J/y production in ISR events - Results ~70k selected events, ~8000 in peak BABAR Preliminary Background: < 0.1% in peak < 0.3% in NR region Preliminary results: PDG: (Dominant systematic is error on K from FSR, and uncertainty on J/ lineshape) J. Boyd - Photon 2003

  13. J/y production in ISR events - Interference Line shape with/without interference convoluted with detector resolution • Interference between J/ production and non-resonant component • Effects the shape of the distribution but has very little effect on the total cross section • Taken into account as a systematic error (0.3%) J. Boyd - Photon 2003

  14. J/y production in ISR events – the future… This is just the beginning for charmonium production in ISR at BaBar Also looking at J/, (2S) production in hadron decays modes Eventual goal is to measure RHAD(s) using ISR at BaBar BABAR Preliminary J/->+-+- (2S)->J/+- +- J. Boyd - Photon 2003

  15. BJ/yX experimental observation An excess at low momentum in the inclusive production of charmonium mesons in B decay at the U(4S) has been observed compared to the non-relativistic QCD prediction (excess corresponds to a branching fraction ~10-4) • Possible source includes: • intrinsic charm component of B • production of sdg hybrid with J/y • Rate enhanced due to B decay to J/y baryon-antibaryon NRQCD color singlet data Phys.Rev. D67, 032002 (2003) J. Boyd - Photon 2003

  16. B+  J/ypL B0  J/ypp pp l+l-,l=m,e B+  J/ypL and B0  J/ypp analysis These processes can be enhanced by exotic QCD resonances in intermediate states e.g. (baryonium, pentaquark, nuclear-bound quarkonium) l+l-,l=m,e Key elements of the analysis are the separation of low momentum protons from Kaons (DIRC, dE/dx) - 98 % efficiency, less than 1% misidentification J. Boyd - Photon 2003

  17. B+J/y pL results 4 events in signalregion with an expected background of 0.210.14 Prob.(4, expecting 0.21 0.14) is equal to 2.5x10-4 (3.5 s) Bayesian analysis, uniform prior 0 gives: +9 -6 B(B+J/y pL)=(12 )x10-6 90% CL upper limit 26x10-6 Submitted to PRL hep-ex/0303036 Efficiency uncertainty is dominant systematic J. Boyd - Photon 2003

  18. B0J/y pp results 1 event in signal region Expected 0.640.17 background events, one observed. 90% CL upper limit 1.9x10-6 J. Boyd - Photon 2003

  19. This is not an explanation of the excess • Measured branching fractions order of magnitude • too low to explain excess • Each of the possible QCD exotic resonances (baryonium, pentaquark, nuclear-bound quarkonium) that could be involved foresee a monoenergetic particle (J/y , p, L) in the B frame No evidence for Exotic resonance production J. Boyd - Photon 2003

  20. (4.4  1.4  0.5) x 10-5 (5.1  1.9  0.5) x 10-5 < 9.2 x 10-6 < 2.7 x 10-5 < 6.3 x 10-5 10- 5 +8.5 - 5.6 (11.6 )x10-6 < 1.9 x 10-6 10- 6 (4.6  0.7  0.6) x 10-5 (1.6  0.6  0.4) x 10-5 10- 5 Summary of exclusive B decays to Charmonium Measured Branching fractions And Upper Limits at 90% CL Phys.Rev.Lett. 90, 091801 (2003) J. Boyd - Photon 2003

  21. New measurement of the c width Agrees with large width measurements by Belle Observation of the c(2S) J/ production in ISR events Preliminary measurement of the total J/ width Preliminary measurement of the e+e- J/ width New Exclusive B decays to charmonium J/ Baryon anti-Baryon processes cannot explain the excess of J/ production at low p* in B decays Summary J. Boyd - Photon 2003

  22. What is Mes and DeltaE etaC event selection Systematics on ISR J/ widths J/ baryon anti-baryon event selection BACK UP SLIDES… J. Boyd - Photon 2003

  23. Exclusive B reconstruction variables • The variables MES and E • E is the difference between the B candidate energy and the expected energy • MES is the B candidate mass with the beam energy used as the candidates energy • Nearly uncorrelated • Very useful for distinguishing signal • from, background (continuum & B background) J. Boyd - Photon 2003

  24. c production in 2 events – Event Selection • Do not reconstruct the e+e- • Select 2 photon events • Etot(lab) <9GeV (suppresses B decays) • pT <0.5GeV/c • Fully reconstruct the C(KSK+- ) • Ks ->+- • 0.491<M(+-)<0.503 GeV/c2 • Cos (Ks) > 0.99 • Apply Particle Id on charged K candidate (dE/dX & DIRC) • Fit the KSK+- vertex (prob(2)>0.01) J. Boyd - Photon 2003

  25. J/y production in ISR events – Systematic Errors Summary of the systematic errors on the J/ parameters Statistical error on K factor 0.9% Systematic error on K factor 1.3% (Varying cut values) Background uncertainty 0.5% (MC / varying background cuts) Simulation of J/ lineshape 1.4% (fit with or without muon bremsstrahlung) Interference 0.3% (see slide 13) Total 2.2% J. Boyd - Photon 2003

  26. B -> J/ Baryon anti-Baryon – Event Selection • Reconstruct J/ -> e+e- or +- • 2.95<Mee<3.13 GeV/c2 or 3.06<M<3.13 GeV/c2 • Particle Id on the electron candidates (EMC, dE/dX, DIRC) and muon candidates (EMC, IFR) • Particle Id on Proton candidates (dE/dX, DIRC) • Lambda candidates reconstructed in -> p+- mode • 1.10<Mp<1.13 GeV/c2 •  vertex >2mm from J/ vertex • Cut on difference between expected B energy and B candidate energy (E) & Mes (B-mass with the beam energy used to improve the resolution) • Efficiencies • 4.9  0.9% (B+-> J/ p), 18.4  2.4% (B0 -> J/ pp) J. Boyd - Photon 2003

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